WO1999063094A2 - Nucleotide and protein sequences of gpr1 and methods based thereon - Google Patents

Abstract

The present invention relates to a (GPR1). The method provides nucleotide sequences of GPR1 genes, and amino acid sequences of their encoded proteins, as well as derivatives (e.g., fragments) and analogs thereof. In a specific embodiment, the GPR1 protein is a yeast protein. The invention further relates to fragments (and derivatives and analogs thereof) of GPR1 which comprise one or more domains of a GPR1 protein. Antibodies to GPR1, its derivatives and analogs, are additionally provided. Methods of production of the GPR1 proteins, derivatives and analogs, e.g., by recombinant means, are also provided. The invention provides for screening assays for identification of compounds that modulate GPR1 expression or activity. Therapeutic methods and pharmaceutical compositions are provided. In specific examples, isolated GPR1 genes and the sequences thereof, are provided.

Description

NUCLEOTIDE AND PROTEIN SEQUENCES OF GPRl AND METHODS BASED THEREON

SPECIFICATION

1. INTRODUCTION

The present invention relates to the discovery, identification and characterization of a novel G protein coupled receptor (referred to herein as GPRl). The invention encompasses GPRl nucleotides, host cell expression systems, GPRl proteins, derivatives, and antibodies to the receptor. The invention provides for screening assays for identification of compounds that modulate GPRl expression or activity. Such identified compounds may be useful in the treatment of diseases caused by fungal infection.

2. BACKGROUND OF THE INVENTION

The baker's yeast Saccharomyces cerevisiae is a nonpathogenic fungus that can exist in two alternative forms, a single-cell form and a pseudohyphal form that consists of long filaments of attached cells. Similarly, the pathogenic fungi Candida albicans and Cryptococcus neoformans can exist as single-cell or filamentous forms. Recently, it has been shown that the non- filamentous form of C. albicans (Lo, H.J. et al., 1997, Cell 90:939-949) and the mating filament-defective form of C. neoformans (Alspaugh, J.A. et al., Genes Dev.) are avirulent in mammalian hosts.

The switch to filamentous growth in S. cerevisiae involves some of the signaling components that are also required for the pheromone response signal transduction pathway. These include components of the MAP kinase cascade and a transcription factor, Stel2 (Roberts, R.L. et al., 1994 Genes Dev. 8:2974-2985). However, the heterotrimeric G protein α-subunit involved in pheromone signaling, Gpal, is not required for pseudohyphal growth. Instead, a different G protein α- subunit, Gpa2. is required for this process (Kubler. E. et al., 1997. J. Biol. Chem. 272:20321-20323; Lorenz, M.C. and J. Heitman. 1997, EMBO J. 16:7008-7018). The GPRl gene has been recently identified as a gene encoding a protein capable of interacting with the GPA2 subunit (Yun, C. et al., 1997, Biochem and Biophys. Res. Comm. 240:287-292). The signal transduction pathway involved in the switch to filamentous growth appears to be conserved among the nonpathogenic and pathogenic yeasts. For example, the MAP kinase and Stel2 homologs in C. albicans are involved in filamentation (Kohler, J.R. et al., 1996, Proc. Natl. Acad. Sci. USA 93: 13223- 13228; Leberer, E.D. et al., 1996, Proc. Natl. Acad. Sci. USA 93:13217-13222), and the Gpa2 homologue in C. neoformans is required for mating filament formation (Alspaugh, J.A. et al., 1997, Genes Dev.).

C. neoformans is one of the most common invasive, opportunistic pathogens in acquired immune deficiency syndrome (AIDS) patients and is the most common cause of fungal meningitis worldwide (Mitchell et al., 1995, Clin. Microbiol. Rev. 8:515- 548). The identification of compounds capable of inhibiting the signal transduction pathway involved in filament formation in pathogenic yeasts can provide useful agents for treatment of diseases associated with fungal infections. The identification of proteins involved in the signal transduction pathway also can provide targets for screening assays designed to identify such compounds useful in treating fungal infections.

3. SUMMARY OF THE INVENTION

The present invention relates to the discovery, identification and characterization of a novel nucleic acid molecule encoding GPRl, a novel Saccharomyces cerevisiae (S. cerevisiae) G-protein coupled receptor. The present invention encompasses GPRl nucleic acid molecules comprising nucleotide sequences that encode GPRl proteins as well as derivatives and analogs thereof having functional activity, portions of the GPRl protein having functional activity, and fusion proteins containing GPRl or a portion thereof fused to another polypeptide. The invention further provides for nucleic acids hybridizable to or complementary to the foregoing nucleotide sequences and encoding for proteins having GPRl -like G-protein coupled receptor activity. The invention also encompasses host cells expressing such nucleic acid molecules and the expression products of such nucleic acid molecules. Methods of production of the GPRl proteins, derivatives and analogs, e.g., by recombinant techniques, are also provided, as well as antibodies to GPRl. and GPRl derivatives and analogs. In a specific embodiment, the GPRl nucleic acid molecule and encoded protein are derived from Saccharomyces cerevisiae. The invention also encompasses agonists and antagonists of GPRl , including molecules that compete with the native natural GPRl ligand, and antibodies, as well as nucleotide sequences that can be used to inhibit GPRl gene expression (e.g., antisense and ribozyme molecules) or enhance GPRl expression (i.e., expression constructs that place the GPRl gene under the control of a strong promoter).

Further, the present invention also relates to methods for the use of the GPRl gene and/or gene products for the identification of compounds which modulate GPRl gene expression and/or gene product activity. Such compounds may be used to inhibit the conversion of non- filamentous forms of fungi to filamentous forms. Such compounds may be used in treatment of fungal infections.

3.1 DEFINITIONS As used herein, underscoring or italicizing the name of a GPRl shall indicate the GPRl gene, in contrast to its encoded protein product which is indicated by the name of GPRl in the absence of any underscoring or italicizing. For example, "GPRl" shall mean the GPRl gene, whereas "GPRl " shall indicate the protein product of the GPRl gene. In addition, a loss of function mutant allele of the gene is indicated by the name of the gene in lower case or by an allele number. 4. BRIEF DESCRIPTION OF THE FIGURES

Figure 1A. Nucleotide sequence of the GPRl gene. Figure IB. Amino acid sequence of GPRl with potential transmembrane domains underlined. Residues shown in bold are conserved in almost all G protein-coupled receptors. Boxed regions show sequence motifs in the third cytoplasmic loop that are related to sequences found in the third cytoplasmic loops of the pheromone receptors.

Figure lC. Predicted topology of GPRl in the membrane, Arrowheads indicate junction sites in plasmids obtained from the two-hybrid screen. Boxed regions show sequence motifs related to sequences in the third cytoplasmic loops of the pheromone receptors and an asparagine-rich region in the third cytoplasmic loop. Figure 2A. Genotypes of S. cerevisiae strains used in genetic studies. Figure 2B. Phenotype of GPRl and ras2 mutants. A diploid heterozygous for gprl::HIS3 and ras2::LEU2 mutations (H96) was sporulated and tetrads were dissected. Left, representative sample of tetrads after growth for 2 or 3 days, as indicated. Right, tetrad labeled with genotype of spore colonies.

Figure 2C. A strain with the genotype gprl::HIS3 ras2::LEU2 (YX12) was transformed with either a single copy GPA2 plasmid (pGPA2-33.1), a multicopy GPA2 plasmid (pGPA2-l 12.1), a single copy GPA2^R273Λ plasmid (pG2CT-33.2), or a multicopy GPA2^R273A plasmid (pG2CT-l 12.2) and streaked out for single colonies on selective medium.

Figure 2D. A wild type strain (W303 IB) and a strain with the genotype gprl::HIS3 (YX6B) transformed with either multicopy GPA2 plasmid pGPA2-l 12.1 (mcGPA2), single copy GPA2^R273A plasmid pG2CT-33.2 (scGPA2*), or vector YEplacl 12 (vector) were grown to saturation for 2 days, incubated at 50 °C for 20 min, and diluted and plated to determine the percent survival. Values for GPRl strains are represented by the open bars (n=3); values for gprl::HIS3 strains are represented by the filled bars (n=3).

Figure 3. GPRl is localized to the cell surface. A wild type strain (W3031 A) was transformed with a multicopy plasmid containing a GPRl-GFP fusion construct (pGPRl-GFP.l) and viewed by fluorescence microscopy with a FITC filter (Grelp-GFP) or with differential interference contrast (DIC) optics.

Figure 4A. Effect of deleting sequences in the third loop and cytoplasmic tail of GPRl . Alignment of sequences in the third cytoplasmic loops of GPRl, the α-mating factor receptor Ste3p, the a- mating factor receptor Ste2p, the S pombe P-factor receptor mam2, and the S. pombe M-factor receptor map3. Figure 4B. A strain with the genotype gprl::HIS3 ras2::LEU2 (YX12) carrying either pGPRl- 22.2, pGPRl^d490-⁵⁸⁶-22.2, pGPRl ²⁷⁷-²⁸⁴-22.2, pGPRl^d610-^6,7-22.2, or YCplac22 (vector) was streaked out for single colonies. Figure 4C. Cell extracts were prepared from a wild type strain ( W3031 A) containing vector YEplac 112 (lane 1 ), pGPR 1 -GFP .1 (lane 2), pGPRl^^-GFP.l (lane 3), pGPRl^d490-⁵⁸⁶-GFP.l (lane 4), pGPRl^d6,°-⁶'⁷ - GFP. l (lane 5), pGPRl^d694"954-GFP.l (lane 6), and pGPRl^d841-⁹⁵⁴-GFP.l (lane 7). A Western blot containing these samples was probed with anti-GFP polyclonal antiserum. The blot was reprobed with anti-PGK polyclonal antiserum. Figure 4D. A wild type strain (W3031 A) transformed with pGPRJ^d277"28 -GFP.1 , pGPRl^d490-⁵⁸⁶-GFP.l, or pGPRl^d6,°-^6,7-GFP. l was viewed by fluorescence microscopy with a FITC filter.

Figure 5. GPRl RNA levels in cells starved for nitrogen and amino acids. RNA was isolated from wild type auxotrophic (W3031 A, lanes 1-6) and proto trophic (W3031B.TLH, lanes 7-9) strains under the following conditions: growing in log phase in the presence (lanes 1 and 4) or absence (lane 7) of amino acids, incubated in the absence of nitrogen and amino acids for 24 hr (lanes 2 and 8), incubated in the absence of nitrogen for 24 hr with essential amino acids present (lane 5), 2 hr after the addition of 10 mM asparagine and essential amino acids to starved cells (lanes 3 and 6), or 2 hr after the addition of 10 rnM asparagine to starved cells (lane 9). A Northern blot prepared from the RNA was hybridized with a GPRl probe and then rehybridized with a PGK1 probe as a loading control.

Figure 6. Model for the Ras and GPR1/GPA2 signaling pathways. For clarity, some of the known interactions between the Ras and GPA2 pathways have not been shown. 5. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the discover}', identification and characterization of a S. cerevisiae nucleic acid molecule that encodes a novel G-protein coupled receptor, herein referred to as GPRl. The novel GPRl has been characterized as a protein of 961 amino acids that is predicted to have seven transmembrane domains spanning the plasma membrane, which is characteristic of G-protein coupled receptors . The deduced structure of the protein indicates that it would contain a very large third cytoplasmic loop of approximately 346 amino acids, and a large cytoplasmic tail of approximately 281 amino acids. The third cytoplasmic loop contains two copies of a short, basic sequence; one copy is present at the amino- terminal end of the loop and the other copy is present at the C-terminal end. The third cytoplasmic loop also contains a poly-asparagine stretch.

The invention provides GPRl nucleic acid molecules and their encoded proteins. The invention also relates to GPRl derivatives and analogs which are functionally active, i.e., they are capable of displaying one or more known functional activities associated with a full-length (wild-type) GPRl protein. Such functional activities include but are not limited to the ability to interact with the G_α subunit GPA2, regulation of cAMP levels and induction of filament formation in fungi. The invention further relates to fragments of GPRl which comprise one or more domains of the GPRl protein including but not limited to the extracellular domain or the cytoplasmic loop and tail domains indicated in Figure lC. The GPRl genes of the invention include the Saccharomyces cerevisiae gene and GPRl and related GPRls (homologs) in other species such as Candidas albicans and Cryptococcus neoformans. The GPRl genes and proteins can also be from vertebrates, or more particularly, mammals. Production of the foregoing proteins and derivatives, e.g., by recombinant methods, is provided by the present invention. Antibodies to GPRl, its derivatives and analogs, are additionally provided. The present invention also relates to screening methods for identification of compounds that regulate the expression or activity of the GPRl protein. Such compounds may be useful for treatment of diseases caused by fungal infection by administering such compounds that regulate GPRl expression or activity (e.g., antibodies, GPRl antisense nucleic acids, GPRl antagonist derivatives).

5.1. ISOLATION OF GPRl GENES The present invention relates to GPRl nucleic acid molecules. In a specific embodiment, the GPRl nucleic acid molecule comprises the DNA sequences of SEQ ID NO:l, or the coding regions thereof, or nucleotide sequences encoding a GPRl protein (e.g., a protein having the sequence of SEQ ID NO:2) shown in Figure 1A and B. Nucleic acids can be single or double stranded. The invention also relates to nucleic acids complementary to, or hybridizable under conditions described below, to the foregoing sequences and which encode a protein having GPRl activity.

In a specific embodiment, a nucleic acid which encodes for a functionally active GPRl protein which is hybridizable to a GPRl nucleic acid (e.g., having sequence SEQ ID NO:l), or to a nucleic acid encoding a GPRl derivative, under conditions of low stringency is provided. As used herein, a functionally active GPRl refers to a transmembrane G-protein coupled receptor involved in the regulation of filamentous growth in yeast. By way of example and not limitation, procedures using such conditions of low stringency are as follows (see also Shilo and Weinberg, 1981, Proc. Natl. Acad. Sci. USA 78:6789-6792; and Sambrook et al. 1989, Molecular Cloning, A Laboratory Manual, 2d Ed., Cold Spring Harbor Laboratory Press, Cold Spring harbor. New York): Filters containing DNA are pretreated for 6 h at 40 °C in a solution containing 35% formamide, 5X SSC, 50 mM Tris-HCl (pH 7.5), 5 mM EDTA, 0.1% PVP, 0.1% Ficoll, 1% BSA, and 500 mg/ml denatured salmon sperm DNA. Hybridizations are carried out in the same solution with the following modifications: 0.02% PVP, 0.02% Ficoll, 0.2% BSA, 100 mg/ml salmon sperm DNA, 10% (wt/vol) dextran sulfate, and 5-20 X 10⁶ CpM ³²P-labeled probe is used. Filters are incubated in hybridization mixture for 18-20 h at 40 °C, and then washed for 1.5 h at 55 °C in a solution containing 2X SSC, 25 mM Tris-HCl (pH 7.4), 5 mM EDTA, and 0.1% SDS. The wash solution is replaced with fresh solution and incubated an additional 1.5 h at 60 °C. Filters are blotted dry and exposed for autoradiography. If necessary, filters are washed for a third time at 65-68°C and reexposed to film. Other conditions of low stringency which may be used are well known in the art (e.g.. as employed for cross species hybridizations).

In another specific embodiment, a nucleic acid which encodes a functionally active GPRl and is hybridizable to a GPRl nucleic acid under conditions of high stringency is provided. By way of example and not limitation, procedures using such conditions of high stringency are as follows: Prehybridization of filters containing DNA is carried out for 8 h to overnight at 65 °C in buffer composed of 6X SSC, 50 mM Tris-HCl (pH 7.5), 1 mM EDTA, 0.02% PVP, 0.02% Ficoll, 0.02% BSA, and 500 mg/ml denatured salmon sperm DNA. Filters are hybridized for 48 h at 65 °C in prehybridization mixture containing 100 mg/ml denatured salmon sperm DNA and 5-20 X 10⁶ CpM Of ³²P-labeled probe. Washing of filters is done at 37°C for 1 h in a solution containing 2X SSC, 0.01% PVP, 0.01% Ficoll. and 0.01% BSA. This is followed by a wash in 0.1X SSC at 50°C for 45 min before autoradiography. Other conditions of high stringency which may be used are well known in the art. In another specific embodiment, a nucleic acid which encodes a functionally active GPRl and is hybridizable to a GPRl nucleic acid under conditions of moderate stringency is provided. For example, but not limited to, procedures using such conditions of moderate stringency are as follows: Filters containing DNA are pretreated for 6 h at 55 °C in a solution containing 6X SSC, 5X Denhart's solution, 0.5% SDS and 100 mg/ml denatured salmon sperm DNA. Hybridizations are carried out in the same solution and 5-20 X 10⁶ CpM ³²P- labeled probe is used. Filters are incubated in hybridization mixture for 18-20 h at 55 °C, and then washed twice for 30 minutes at 60°C in a solution containing IX SSC and 0.1% SDS. Filters are blotted dry and exposed for autoradiography. Other conditions of moderate stringency which may be used are well-known in the art. Washing of filters is done at 37°C for 1 h in a solution containing 2X SSC, 0.1% SDS,

Nucleic acids encoding derivatives and analogs of GPRl proteins and GPRl antisense nucleic acids are additionally provided. In particular, GPRl derivatives can be made by altering GPRl nucleic acid sequences by substitutions, additions or deletions that provide for functionally equivalent molecules, i.e., molecules capable of regulating filament formation in fungi. Due to the degeneracy of nucleotide coding sequences, other DNA sequences which encode substantially the same amino acid sequence as shown in Figure 1 may be used in the practice of the present invention. These include, but are not limited to, those containing, as a primary amino acid sequence, all or part of the amino acid sequence of the GPRl protein including altered sequences in which functionally equivalent amino acid residues are substituted for residues within the sequence resulting in a silent change. For example, one or more amino acid residues within the sequence can be substituted by another amino acid of a similar polarity which acts as a functional equivalent, resulting in a silent alteration. Substitutes for an amino acid within the sequence may be selected from other members of the class to which the amino acid belongs. For example, the nonpolar (hydrophobic) amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan and methionine. The polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine. The positively charged (basic) amino acids include arginine, lysine and histidine. The negatively charged (acidic) amino acids include aspartic acid and glutamic acid.

Derivatives or analogs of GPRl include but are not limited to those molecules comprising regions that are substantially homologous to GPRl or fragments thereof (e.g., in various embodiments, at least 60% or 70% or 80% or 90% or 95%) identity over an amino acid sequence of identical size or when compared to an aligned sequence in which the alignment is done by a computer homology program known in the art) or whose encoding nucleic acid is capable of hybridizing to a coding GPRl sequence, under stringent, moderately stringent, or non-stringent conditions (See, for example pp323-358, Nucleic Acid and Protein Sequence Analysis, ed. Bishop M.J. and Rawlings, C.J. ,1987, IRL Press, Oxford, England) . Fragments of GPRl nucleic acids comprising regions conserved between (with homology to) other GPRl nucleic acids, of the same or different species, are also provided. Nucleic acids encoding one or more GPRl domains are provided.

Specific embodiments for the cloning of a GPRl gene, presented as particular examples but not by way of limitation, follow. Any eukaryotic cell potentially can serve as the nucleic acid source for the molecular cloning of the GPRl gene. The nucleic acid sequences encoding GPRl can be isolated from a variety of different sources including but not limited to fungi, such as S. cerevisiae, C neoformans. and C. albicans, vertebrate, mammalian and human sources. The DNA may be obtained by standard procedures known in the art from cloned DNA (e.g., a DNA "library"), by chemical synthesis, by cDNA cloning, or by the cloning of genomic DNA. or fragments thereof, purified from the desired cell (See, for example, Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, 2d Ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York Glover, D.M. (ed.), 1985, DNA Cloning: A Practical Approach MRL Press, Ltd., Oxford, U.K. Vol. I, II.). Whatever the source, the GPRl should be molecularly cloned into a suitable vector for propagation of the DNA molecule.

For expression cloning (a technique commonly known in the art), an expression library is constructed by methods known in the art. For example, mRNA (e.g., S. cerevisiae) is isolated, cDNA is made and Hgated into an expression vector (e.g., a bacteriophage derivative) such that it is capable of being expressed by the host cell into which it is then introduced. Various screening assays can then be used to select for the expressed GPRl product. For example, complementation of GPRl mutant alleles in, for example, S. cerevisiae may be used to identify GPRl cDNA clones. In addition, a portion of the GPRl gene can be purified and labeled, and a cDNA library may be screened by nucleic acid hybridization to the labeled probe (Benton, W. and Davis, R., 1977, Science 196:180; Grunstein, M. and Hogness, D., 1975, Proc. Natl. Acad. Sci. U.S.A. 72:3961). In another embodiment. anti-GPRl antibodies can be used for selection of clones expressing GPRl protein.

In another embodiment, polymerase chain reaction (PCR) is used to amplify the desired sequence in a genomic or cDNA library. Ohgonucleotide primers representing known GPRl sequences can be used as primers in PCR. The synthetic oligonucleotides may be utilized as primers to amplify by PCR sequences from a source (RNA or DNA), preferably a cDNA library, of potential interest. PCR can be carried out, e.g., by use of a Perkin-Elmer Cetus thermal cycler and Taq polymerase (GPRl Amp.). The nucleic acids being amplified can include mRNA or cDNA or genomic DNA from any eukaryotic species. After successful amplification of a segment of a GPRl gene, that segment may be molecularly cloned and sequenced. and utilized as a probe to isolate a complete cDNA or genomic clone. This, in turn, will permit the determination of the GPRl's complete nucleotide sequence, the analysis of its expression, and the production of its protein product for functional analysis, as described infra.

Genomic DNA encoding the GPRl protein may also be isolated. For example, DNA fragments are generated, some of which will encode the desired GPRl protein. The DNA fragments are generated by cleavage of genomic DNA at specific sites using various restriction enzymes. Alternatively, one may use DNAse in the presence of manganese to fragment the DNA, or the DNA can be physically sheared, as for example, by sonication. The linear DNA fragments can then be separated according to size by standard techniques, including but not limited to, agarose and poly aery lamide gel electrophoresis and column chromatography.

Once the DNA fragments are generated, identification of the specific DNA fragment containing the desired GPRl gene may be accomplished in a number of ways. For example, if a portion of the GPRl gene or its specific RNA, or a fragment thereof, is available and can be purified and labeled, the generated DNA fragments may be screened by nucleic acid hybridization to the labeled probe (Benton, W. and Davis, R., 1977, Science 196: 180; Grunstein, M. and Hogness, D., 1975, Proc. Natl. Acad. Sci. U.S.A. 72:3961). Those DNA fragments with substantial sequential complementarity to the probe will hybridize.

Further selection can be carried out on the basis of the properties of the GPRl . Alternatively, the presence of the GPRl may be detected by assays based on the physical, chemical, or immunological properties of its expressed product. For example, DNA clones can be selected which produce a protein that, e.g., has similar or identical electrophoretic migration, isolectric focusing behavior, proteolytic digestion maps, or antigenic properties as known for GPRl . If an antibody to GPRl is available, the GPRl protein may be identified by binding of labeled antibody to the putatively GPRl synthesizing clones, in an ELISA (enzyme-linked immunosorbent assay )-type procedure. The present invention encompasses GPRl genes isolated from S. cerevisiae as well as GPRl genes from other species. To isolate homologous GPRl genes from other species, one synthesizes several different degenerate primers, for use in PCR reactions. In a preferred aspect, the ohgonucleotide primers represent at least part of the GPRl gene comprising conserved GPRl sequences of different species. It is also possible to vary the stringency of hybridization conditions used in priming the PCR reactions, to allow for greater or lesser degrees of nucleotide sequence similarity between the known GPRl nucleotide sequence and the nucleic acid homolog being isolated. In addition genomic and/or cDNA libraries may be screened with labeled GPRl DNA fragments and hybridized to the genomic or cDNA libraries. For cross species hybridization, low stringency conditions are preferred. For same species hybridization, moderately stringent conditions are preferred. In this fashion, additional homologs of the GPRl gene encoding GPRl proteins and GPRl analogs may be identified. Once identified and isolated the GPRl gene can then be inserted into an appropriate cloning vector or amplification and/or expression in a host. A large number of vector-host systems known in the art may be used. Possible vectors include, but are not limited to, plasmids and modified viruses, but the vector system must be compatible with the host cell used. Such vectors include, but are not limited to. bacteriophages such as lambda derivatives, or plasmids such as PBR322 or pUC plasmid derivatives or the Bluescript vector (Stratagene). The insertion into a cloning vector can, for example, be accomplished by ligating the DNA fragment into a cloning vector which has complementary cohesive termini. However, if the complementary restriction sites used to fragment the DNA are not present in the cloning vector, the ends of the DNA molecules may be enzymatically modified. Alternatively, any site desired may be produced by ligating nucleotide sequences (linkers) onto the DNA termini; these ligated linkers may comprise specific chemically synthesized oligonucleotides encoding restriction endonuclease recognition sequences. Recombinant molecules can be introduced into host cells via transformation, transfection, infection, electroporation, etc., so that many copies of the GPRl sequence are generated. In specific embodiments, transformation of host cells with recombinant DNA molecules that incorporate the isolated GPRl gene, cDNA, or synthesized DNA sequence enables generation of multiple copies of the GPRl gene. Thus, nucleotide sequences encoding GPRl may be obtained in large quantities by growing transformants, isolating the recombinant DNA molecules from the transformants and, when necessary, retrieving the inserted GPRl from the isolated recombinant DNA.

5.2. EXPRESSION OF GPRl PROTEINS The nucleic acid molecule coding for a GPRl protein or a functionally active analog or fragment or other derivative thereof can be inserted into an appropriate expression vector, i. e. , a vector which contains the necessar}' elements for the transcription and translation of the inserted protein-coding sequence. The necessary transcriptional and translational signals can also be supplied by the native GPRl gene and/or its flanking regions. A variety of host-vector systems may be utilized to express the protein-coding sequence. These include but are not limited to microorganisms such as yeast containing yeast vectors, mammalian cell systems infected with virus (e.g., vaccinia virus, adenovirus, etc.); or bacteria transformed with bacteriophage DNA, plasmid DNA, or cosmid DNA. The expression elements of vectors vary in their strengths and specificities. Depending on the host-vector system utilized, any one of a number of suitable transcription and translation elements may be used. In specific embodiments, the S. cerevisiae GPRl gene is expressed, or a sequence encoding a functionally active portion of the S. cerevisiae GPRl gene is expressed. In yet another embodiment, a fragment of GPRl comprising a domain of the GPRl protein such as the extracellular, cytoplasmic loop or tail domain is expressed (see, Figure IB). Any of the methods previously described for the insertion of DNA fragments into a vector may be used to construct expression vectors containing a GPRl protein coding sequence and appropriate transcriptional/translational control signals. These methods may include in vitro recombinant DNA and synthetic techniques and in vivo recombinants (genetic recombination). Expression of nucleic acid sequences encoding GPRl , or fragments thereof, may be regulated by a second nucleic acid sequence so that the GPRl protein or peptide is expressed in a host transformed with the recombinant DNA molecule. For example, expression of a GPRl protein may be controlled by any promoter/enhancer element known in the art. Such promoters include promoter elements from yeast or other fungi such as the Gal4 promoter, the ADH (alcohol dehydrogenase) promoter and the PGK (phosphoglycerol kinase) promoter. Additional promoters that may be used in the practice of the invention include the alkaline phosphatase promoter, prokaryotic promoters such as β- lactamase, or viral promoters such as the CMV promoter, or tac promoter, or mammalian promotor/enhancer elements, such as tissue-specific elements. In a specific embodiment, a vector is used that comprises a promoter operably linked to a GPRl -encoding nucleic acid, one or more origins of replication, and, optionally, one or more selectable markers (e.g., an antibiotic resistance gene).

Expression vectors containing a GPRl gene insert can be identified by three general approaches: (a) nucleic acid hybridization, (b) presence or absence of "marker" gene functions, and (c) expression of inserted sequences. In the first approach, the presence of the GPRl gene inserted in an expression vector can be detected by nucleic acid hybridization using probes comprising sequences that are homologous to an inserted GPRl gene. In the second approach the recombinant vector/host system can be identified and selected based upon the presence or absence of certain "marker" gene functions (e.g., resistance to antibiotics) caused by the insertion of the GPRl gene into the vector. For example, if the GPRl gene is inserted within the marker gene sequence of the vector, recombinants containing the GPRl insert can be identified by the absence of the marker gene function. In the third approach, recombinant expression vectors are identified by assaying for the GPRl product expressed by the recombinant. Such assays are based, for example, on the physical or functional properties of the GPRl protein in in vitro assay systems, e.g., binding with anti-GPRl antibody or in vivo assay systems, e.g., complementation of mutant GPRl alleles in, for example, different yeast species.

Once a particular recombinant DNA molecule is identified and isolated, several methods known in the art may be used to propagate it. Once a suitable host system and growth conditions are established, recombinant expression vectors can be propagated and prepared in quantity. As previously explained, the expression vectors which can be used include, but are not limited to, the following vectors or their derivatives: human or animal viruses such as vaccinia virus or adenovirus; insect viruses such as baculovirus; yeast vectors; bacteriophage vectors (e.g., lambda), and plasmid and cosmid DNA vectors, to name but a few.

In addition, a host cell strain may be chosen which modulates the expression of the inserted sequences, or modifies and processes the GPRl product in the specific fashion desired. Expression from certain promoters can be elevated in the presence of certain inducers; thus, expression of the genetically engineered GPRl protein may be controlled. Furthermore, different host cells have characteristic and specific mechanisms for the translation and post-translational processing and modification (e.g., glycosylation, phosphorylation of proteins). Appropriate cell lines or host systems can be chosen to ensure the desired modification and processing of the foreign protein expressed. For example, expression in a bacterial system can be used to produce an unglycosylated core protein product. Expression in yeast will produce a glycosylated product. Furthermore, different vector/host expression systems may effect processing reactions to different extents.

In other specific embodiments, the GPRl protein, fragment, analog, or derivative may be expressed as a fusion, or chimeric protein product comprising the protein, fragment, analog, or derivative joined via a peptide bond to a heterologous protein sequence. Such a chimeric product can be made by ligating the appropriate nucleic acid sequences encoding the desired amino acid sequences to each other by methods known in the art, in the proper coding frame, and expressing the chimeric product by methods commonly known in the art. Alternatively, such a chimeric product may be made by protein synthetic techniques, e.g., by use of a peptide synthesizer. 5.3. IDENTIFICATION AND PURIFICATION OF THE GPRl GENE PRODUCT In particular aspects, the invention provides GPRl , preferably GPRl derived from yeast, and fragments and derivatives thereof which comprise an antigenic determinant (i.e., can be recognized by an antibody) or which are otherwise functionally active, as well as nucleic acid sequences encoding the foregoing. "Functionally active" GPRl material as used herein refers to that material displaying one or more known functional activities associated with a full-length wild-type GPRl protein, e.g., localization within the cell membrane and induction of filament formation in yeast.

Once a recombinant which expresses the GPRl gene sequence is identified, the GPRl product can be analyzed. This is achieved by assays based on the physical or functional properties of the product, including radioactive labelling of the product followed by analysis by gel electrophoresis, immunoassay, etc.

Once the GPRl protein is identified, it may be isolated and purified by standard methods including chromatography (e.g., ion exchange, affinity, and sizing column chromatography), centrifugation, differential solubility, or by any other standard technique for the purification of proteins.

Alternatively, once a GPRl protein produced by a recombinant is identified, the amino acid sequence of the protein can be deduced from the nucleotide sequence of the GPRl contained in the recombinant. As a result, the protein can be synthesized by standard chemical methods known in the art (e.g., see Hunkapiller, M., et al., 1984, Nature 310: 105-111).

In another alternate embodiment, native GPRl proteins can be purified from natural sources, by standard methods such as those described above (e.g., immunoaffmity purification).

In a specific embodiment of the present invention, such GPRl proteins, whether produced by recombinant DNA techniques or by chemical synthetic methods or by purification of native proteins, include but are not limited to those containing, as a primary amino acid sequence, all or part, of the amino acid sequence substantially as depicted Figure 1 (SEQ ID NO:2), as well as fragments and other derivatives, and analogs thereof, including proteins homologous thereto.

5.4. GENERATION OF ANTIBODIES TO GPRl PROTEINS AND DERIVATIVES THEREOF

According to the invention, GPRl protein, its fragments or other derivatives, or analogs thereof, may be used as an immunogen to generate antibodies which immunospecifically bind such an immunogen. Such antibodies include but are not limited to polyclonal, monoclonal, chimeric, single chain, Fab fragments, and an Fab expression library. In a specific embodiment, antibodies to a S. cerevisiae GPRl protein are produced. In another embodiment, antibodies to a domain of a GPRl protein are produced.

Various procedures known in the art may be used for the production of polyclonal antibodies to a GPRl protein or derivative or analog. In a particular embodiment, rabbit polyclonal antibodies to an epitope of a GPRl protein encoded by a sequence of SEQ ID NO: 1 , or a subsequence thereof, are obtained. For the production of antibody, various host animals are immunized by injection with the native GPRl protein, or a synthetic version, or derivative (e.g., fragment) thereof, including but not limited to rabbits, mice, rats, etc. Various adjuvants may be used to increase the immunological response, depending on the host species, and including but not limited to Freund's (complete and incomplete), mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanins, dinitrophenol, and potentially useful human adjuvants such as BCG (bacille Calmette-Guerin) and corynebacterium parvum.

For preparation of monoclonal antibodies directed toward a GPRl protein sequence or analog thereof, any technique which provides for the production of antibody molecules by continuous cell lines in culture may be used. For example, the hybridoma technique originally developed by Kohler and Milstein (1975, Nature 256:495-497), as well as the trioma technique, the human B-cell hybridoma technique (Kozbor et al., 1983, Immunology Today 4:72), and the EBV hybridoma technique to produce human monoclonal antibodies (Cole et al., 1985, in Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77-96) may be used to produce monoclonal antibodies. According to the invention, techniques described for the production of single chain antibodies (e.g.,U.S. Patent 4,946,778) can be adapted to produce GPR1- specific single chain antibodies. An additional embodiment of the invention utilizes the techniques described for the construction of Fab expression libraries (Huse et al., 1989, Science 246:12751281) to allow rapid and easy identification of monoclonal Fab fragments with the desired specificity for GPRl protein derivatives, or analogs. In the production of antibodies, screening for the desired antibody is accomplished by techniques known in the art, e.g. ELISA (enzyme-linked immunosorbent assay). For example, to select antibodies which recognize a specific domain of a GPRl protein, one assays generated hybridomas for a product which specifically binds to a GPRl fragment containing such domain. For selection of an antibody that specifically binds a first GPRl homolog but which does not specifically bind a different GPRl homolog, one selects on the basis of positive binding to the first GPRl homolog and a lack of binding to the second GPRl homolog.

5.5. SCREENING FOR GPRl AGONISTS AND ANTAGONISTS

A variety of different assay systems can be designed and used to identify compounds or compositions that modulate GPRl activity or GPRl gene expression, and therefore, may be useful to inhibit filament formation and useful in the treatment of diseases associated with fungal infections. In each of the assay systems described below, the S.cerevisiae GPRl gene may be utilized, as well as GPRl genes from other species.

In accordance with the invention, cell-based assay systems are used to screen for compounds that modulate the activity of GPRl and thereby, modulate filament production in yeast. Compounds that may affect GPRl activity include but are not limited to compounds that bind to the GPRl functional domains and either activate signal transduction (agonists) or block activation (antagonists). Compounds that affect GPRl activity by affecting GPRl gene expression, including molecules that affect transcription are also be identified using the screens of the invention. However, it should be noted that the assays described are also identify compounds that modulate GPRl signal transduction (e.g., compounds which affect downstream signaling events and participate in transducing the signal activated by the natural

GPRl ligand). The identification and use of such compounds which affect signaling events downstream of GPRl and thus modulate effects of GPRl on the switch from non-filamentous to filamentous growth in yeast are within the scope of the invention. To this end, cells that endogenously express GPRl can be used to screen for compounds that modulate GPRl activity. Alternatively, cells that do not normally express GPRl can be genetically engineered to express the GPRl gene and such cells may be used for screening purposes. The cells can be further engineered to incorporate a reporter molecule linked to the signal transduced by activated GPRl to aid in identification of compounds that modulate GPRl activity. Cells to be used to screen for compounds are cells that respond to activation of GPRl , e.g., as measured by a chemical, physiological, biological, or phenotypic change. For example, a test compound may be tested for its ability to inhibit or activate filament formation. Alternatively, constructs containing the cAMP responsive element linked to any of a variety of different reporter genes may be introduced into cells. Such reporter genes may include but are not limited to a selectable marker, such as HIS3, which allows for selection for growth in the absence of histidine. Alternatively, a cAMP responsive element can be linked to the lacZ gene encoding β-galactosidase, followed by a screen for production of blue color in the presence of X-gal. Following exposure of the cells to a test compound , the level of reporter gene expression may be quantitated to determine the test compounds ability to regulate GPRl activity.

In a specific embodiment of the invention, screening for drugs that antagonize the GPRl can be performed using a reporter assay that responds to the activity of the GPR1/GPA2 pathway. In a specific embodiment of the invention this can be accomplished by coupling the GPRl receptor to the GPA1 α-subunit. which activates the pheromone response pathway in yeast. Activation of the pheromone response pathway results in transcriptional induction of a number of genes, including the FUS1 gene in S. cerevisiae, which provides a rapid and specific assay for GPRl activity. The screen relies on the fact that the extreme C-terminus of a G protein α- subunit determines its receptor specificity. In yeast, mutations in the C-terminus of GPA1 effect coupling to the a-factor and α-factor receptors, indicating that the determinants for receptor specificity as well as for receptor binding are located in this region. A chimeric α-subunit consisting of a large N-terminal segment of GPA1 and a small C-terminal segment of GPA2 couples the GPRl receptor to the pheromone response pathway.

In an embodiment of the invention a chimeric GPA1/GPA2 α-subunit gene is constructed that consists of the N-terminal amino acids of GPA1 and C- terminal amino acids of GPA2. In a specific embodiment of the invention, a construct containing the N-terminal 438 amino acids of GPA1 and the C-terminal 35 amino acids of GPA2 is used for screening purposes. Substitution of the C-terminal amino acids of GPA1 will abolish binding to the pheromone receptors. The endogenous wild type GPA1 gene will be replaced with the chimeric GPA1/GPA2 gene using a selectable marker inserted downstream of the coding region. In addition the strain of yeast to be used will have the genotype άri::LEU2 ste2::LEU2 ste3::LEU2. The far I ::LEU2 allele is required to prevent cell cycle arrest by the cyclin-dependent kinase inhibitor FAR1 upon activation of the pheromone response pathway. The STE2 and STE3 genes encode the pheromone receptors, thus, strains of yeast containing deletions of these genes will ensure that any signals transmitted by the GPA1/GPA2 α-subunit will originate with the GPRl receptor. In addition, a gprl ::HIS3 mutation will be introduced into the strain described above. Comparison of the GPRl and gprl :HIS3 strains will confirm that the signal observed is GPRl - dependent. The resultant strain will be transformed with a reporter gene construct designed to measure activation of the pheromone responsive FUS promoter. For example, a construct containing a FUSl-/αeZ reporter construct can be used to measure activation of the GPRl signaling pathway.

High throughput screening will be accomplished by plating the reporter strain into wells of microtiter plates, each of which will contain a potential GPRl antagonist. The wells will also contain complete medium, which activates the GPRl receptor, and in instances where the reporter lacZ gene is used, the X-gal substrate is added. After incubation with potential antagonists, the cells are permeabilized by adding chloroform to the wells and the blue color derived from cleavage of the X-gal substrate will be measured by spectrophotometry using a micorotiter plate reader. Parallel samples will be processed using the GPRl : :HIS3 strain to ensure that the decrease in signaling observed in the presence of a particular compound requires the GPRl receptor. Compounds of interest will be those that decrease the amount of signal generated by the reporter, indicating that they block activation of GPRl.

Compounds identified in the screen described above will be further tested for their ability to block pseudohyphal development of S. cerevisiae cells and to block filament formation in the pathogenic yeasts C. albicans and C. neoformans. Compounds that block yeast filamentation will be tested for efficacy against yeast infection in mice or rabbits. Various doses of pathogenic yeast culture will be administered to animals in the presence or absence of the identified antagonist, and its ability to block productive infection will be assessed.

In utilizing such cell-based assay systems, the cells expressing the GPRl gene are exposed to a test compound or to vehicle controls (e.g.. placebos). After exposure, the cells can be assayed to measure the expression and/or activity of components of the signal transduction pathway of GPRl . For example, expression of the GPRl gene is associated with a switch in yeast from non-filamentous growth to filamentous growth, thus, in a specific embodiment of the invention assays may be designed to measure filament formation. The ability of a test compound to decrease the level of filament formation, above those levels seen with cells treated with a vehicle control, indicates that the test compound inhibits signal transduction mediated by the GPRl receptor.

Soluble GPRl may be recombinantly expressed and utilized in non-cell based assays to identify compounds that bind to GPRl . Recombinantly expressed GPRl polypeptides or fusion proteins containing one or more of the GPRl functional domains may be prepared as described above, and used in the non-cell based screening assays. For example, where agonists of the natural ligand are sought, the full length GPRl , or a soluble truncated GPRl , e.g. , in which the one or more of the cytoplasmic and transmembrane domains is deleted from the molecule, a peptide corresponding to one or more of the extracellular domains, or a fusion protein containing one or more of the GPRl extracellular domains fused to a protein or polypeptide that affords advantages in the assay system (e.g.. labeling, isolation of the resulting complex, etc.) can be utilized. Where compounds that interact with the cytoplasmic domain are sought to be identified, peptides corresponding to the GPRl cytoplasmic domain and fusion proteins containing the GPRl cytoplasmic domain can be used. The principle of the assays used to identify compounds that bind to the GPRl involves preparing a reaction mixture of the GPRl and the test compound under conditions and for time sufficient to allow the two components to interact and bind, thus forming a complex which can be removed and/or detected in the reaction mixture. The identity of the bound test compound is then determined.

The screening assays are accomplished by any of a variety of commonly known methods. For example, one method to conduct such an assay involves anchoring the GPRl protein, polypeptide, peptide, fusion protein or the test substance onto a solid phase and detecting GPRl /test compound complexes anchored on the solid phase at the end of the reaction. In one embodiment of such a method, the GPRl reactant is anchored onto a solid surface, and the test compound, which is not anchored, may be labeled, either directly or indirectly. In practice, microtitre plates conveniently can be utilized as the solid phase. The anchored component is immobilized by non-covalent or covalent attachments. The surfaces may be prepared in advance and stored. In order to conduct the assay, the non-immobilized component is added to the coated surfaces containing the anchored component. After the reaction is completed, unreacted components are removed (e.g., by washing) under conditions such that any complexes formed will remain immobilized on the solid surface. The detection of complexes anchored on the solid surface can be accomplished in a number of ways. Where the previously non-immobilized component is pre-labeled, the detection of label immobilized on the surface indicates that complexes were formed. Where the previously non-immobilized component is not pre-labeled, an indirect label can be used to detect complexes anchored on the solid surface; e.g.. using a labeled antibody specific for the previously non-immobilized component.

Alternatively, a reaction is conducted in a liquid phase, the reaction products separated from unreacted components using an immobilized antibody specific for GPRl protein, fusion protein or the test compound, and complexes detected using a labeled antibody specific for the other component of the possible complex to detect anchored complexes.

The GPRl gene product can interact in vivo with one or more cellular macromolecules, such as nucleic acid molecules or proteins. For example, the GPRl protein has been demonstrated to form a cytoplasmic complexes with the GPA2 protein In yet another embodiment of the invention, the two hybrid system for selecting interacting proteins in yeast (Fields and Song, 1989, Nature 340:245-246; Chin et al., 1991, Proc. Natl. Acad. Sci. USA 88:9578-9582) can be used to identify molecules that specifically bind to GPRl or derivatives thereof. Once such interacting proteins are identified, compounds that stabilize or disrupt such interactions can be useful in regulating the activity of the GPRl protein.

To assay for compounds that interfere with the interaction of GPRl protein with cellular macromolecules, either the GPRl protein or the macromolecule may be anchored onto a solid phase. Complex formation can be detected at the end of the reaction comparing complex formation in the presence or absence of test compound. The order of addition of test compounds can be varied to obtain different information about the compounds being tested. For example, test compounds that interfere with the interaction by competition can be identified by conducting the reaction in the presence of the test compound, i.e., by adding the test compounds to the reaction mixture prior to or simultaneously with the GPRl protein and the cellular binding partner. Alternatively, test compounds that disrupt preformed complexes, i.e, those compounds with higher binding constants that displace one of the components from the complex, can be tested by adding the test compound to the reaction after the complexes have formed. Assays may also be designed to screen for compounds that regulate

GPRl gene expression at the transcriptional level. In one embodiment, DNA encoding a reporter molecule can be linked to a regulatory element of the GPRl gene and used in appropriate intact cells, cell extracts or lysates to identify compounds that modulate GPRl gene expression. Appropriate cells or cell extracts are prepared from any cell type that normally expresses the GPRl gene, thereby ensuring that the cell extracts contain the transcription factors required for in vitro or in vivo transcription. The screen can be used to identify compounds that modulate the expression of the reporter construct. In such screens, the level of reporter GPRl expression is determined in the presence of the test compound and compared to the level of expression in the absence of the test compound. Compounds that increase the level of GPRl gene expression or prevent the repression of GPRl gene expression, at the transcriptional level, may be useful for treatment of diabetic disorders.

The compounds which may be screened in accordance with the invention include, but are not limited to inorganic compounds, peptides, antibodies and fragments thereof, and other organic compounds (e.g.. peptidomimetics) that bind to GPRl and either activate the activity of GPRl (i.e.. agonists) or inhibit the activity of GPRl (i.e.. antagonists). Compounds may include, but are not limited to, peptides such as, for example, soluble peptides, including but not limited to members of random peptide libraries; (see, e_^ ,, Lam, K.S. et aL, 1991, Nature 354:82-84: Houghten, R. et al., 1991, Nature 354:84-86), and combinatorial chemistry-derived molecular library made of D- and/or L- configuration amino acids, phosphopeptides (including, but not limited to, members of random or partially degenerate directed phosphopeptide libraries; see, e.g.. Songyang, Z. etal., 1993, Cell 72:767-778). Screening the libraries can be accomplished by any of a variety of commonly known methods. In a specific embodiment, screening can be carried out by contacting the library members with a GPRl protein (or nucleic acid or derivative) immobilized on a solid phase and harvesting those library members that bind to the protein (or nucleic acid or derivative). Examples of such screening methods, termed "panning" techniques are described by way of example in Parmley and Smith, 1988, Gene 73:305-318; Fowlkes et al., 1992, BioTechniques 13:422-427; PCT Publication No. WO 94/18318. Compounds identified via assays such as those described herein may be useful, for example, in elaborating the biological function of the GPRl gene product, and for ameliorating diseases associated with fungal infections. Assays for testing the efficacy of compounds identified in the screens can be tested in animal model systems for fungal infections. For example, the rabbit model of Cryptococcal meningitis may be utilized (Alspough, J.A., et al., 1997, Genes Dev. 11:3206-3217) or the mouse model of Candida infection may be utilized to test the efficacy of compounds (Lo, et al., 1997, Cell 90:939-949). Such animal models may be used as test substrates for the identification of drugs, pharmaceuticals, therapies and interventions which may be effective in treating such fungal infections.

5.6. USES OF COMPOUNDS THAT REGULATE GPRl ACTIVITY

The present invention relates to nucleic acid molecules encoding yeast GPRl and the use of those molecules in screening assays designed to identify compounds capable of regulating the biological activity of GPRl . For example, the identified compounds can be used to inhibit the activity of GPRl , thereby, inhibiting the switch from non-filamentous to filamentous growth in fungi.

The invention provides for treatment or prevention of various diseases and disorders caused by fungi by administration of a compound that regulates the expression or activity of the GPRl protein. Such compounds include but are not limited to: GPRl proteins and analogs and derivatives (including fragments) thereof; antibodies thereto (as described hereinabove); nucleic acids encoding the GPRl proteins, analogs, or derivatives (e.g., as described hereinabove); GPRl antisense nucleic acids, and GPRl agonists and antagonists. In an embodiment of the invention, diseases associated with fungal infections are treated or prevented by administration of a compound that regulates GPRl function. Such diseases include those associated with fungi that infect plants, including but not limited to corn smut fungus Ustilago maydis (Regenfelder, E et al, 1997 EMBO J. 16:1934-1942) and the chestnut blight fungus Cryphonectria parasitica (Kasahara, S. and Nuss, D.L., 1997, Mai. Plant Microbe Interact 10:984-993) In a preferred embodiment, diseases and disorders involving fungal infection are treated or prevented by administration of a compound that antagonizes (inhibits) GPRl function. Compounds that can be used include but are not limited to anti-GPRl antibodies (and fragments and derivatives thereof containing the binding region thereof), GPRl antisense nucleic acids, and GPRl nucleic acids that are dysfunctional (e.g., due to a heterologous, non-GPRl sequence) insertion within the GPRl coding sequence) that are used to "knockout" endogenous GPRl function by homologous recombination (see, e.g., Rothstein, 1983, Meth. Enzymol. 101 : 202- 211, Capecchi, 1989, Science 244:1288-1292). In a specific embodiment of the invention, a nucleic acid containing a portion of a GPRl gene in which GPRl sequences flank (are both 5' and 3' to) a different GPRl sequence, is used, as a GPRl antagonist, to promote GPRl inactivation by homologous recombination (see also Koller and Smithies, 1989, Proc. Natl. Acad. Sci. USA 86:8932-8935; Zijlstra et al., 1989, Nature 342:435-438). Other compounds that inhibit GPRl function can be identified by use of known convenient in vitro assays, e.g., based on their ability to inhibit binding of GPRl to another protein, or inhibit any known GPRl function, as preferably assayed in vitro or in cell culture, although genetic assays may also be employed. Preferably, suitable in vitro or in vivo assays, are utilized to determine the effect of a specific compound and whether its administration is indicated for treatment of the affected tissue.

The compounds of the invention are preferably tested in vitro, and then in vivo for a desired therapeutic or prophylactic activity, prior to use in humans. For example, in vitro assays which can be used to determine whether administration of a specific therapeutic is indicated, include in vitro cell culture assays in which yeast grown in culture, and exposed to or otherwise administered a therapeutic compound and the effect of such a therapeutic upon the growth characteristics of the yeast is observed. In a specific embodiment of the invention the ability of a compound to regulate, i.e., activate or inhibit filament formation in various species of fungi may be assayed. The invention provides methods of treatment and/or prophylaxis by administration to a subject of an effective amount of a compound of the invention. In a preferred aspect, the compound is substantially purified. The subject is preferably an animal, and is preferably a mammal, and most preferably human. Various delivery systems are known and can be used to administer a compound capable of regulating GPRl activity or expression, e.g. encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the compound, receptor-mediated endocytosis (see, e.g., Wu and Wu, 1987, J. Biol. Chem. 262:4429-4432). Methods of introduction include but are not limited to intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal, epidural, and oral routes. The compounds may be administered by any convenient route, for example by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.) and may be administered together with other biologically active agents. Administration can be systemic or local. In addition, it may be desirable to introduce the pharmaceutical compositions of the invention into the central nervous system by any suitable route, including intraventricular and intrathecal injection; intraventricular injection may be facilitated by an intraventricular catheter, for example, attached to a reservoir, such as an Ommaya reservoir. Pulmonary administration can also be employed, e.g., by use of an inhaler or nebulizer, and formulation with an aerosolizing agent.

In a specific embodiment, it may be desirable to administer the compositions of the invention locally to a specific area of the body; this may be achieved by, for example, and not by way of limitation, local infusion during surgery, topical application, e.g., in conjunction with a wound dressing after surgery, by injection, by means of a catheter, by means of a suppository, or by means of an implant, said implant being of a porous, non-porous, or gelatinous material, including membranes, such as sialastic membranes, or fibers.

In yet another embodiment, the compound capable of regulating the expression or activity of GPRl can be delivered in a controlled release system. In one embodiment, a pump may be used (see Langer, supra; Sexton, CAC Crit. Ref.

Boomed. Eng. 14:201 (1987); Buchwald et al., Surgery 88:507 (1980); Saudek et al., N. Engl. J. Med. 321 :574 (1989)). In another embodiment, polymeric materials can be used (see Medical Applications of Controlled Release, Langer and Wise (eds.), CAC Pres., Boca Raton, Florida (1974); Controlled Drug Bioavailability, Drug Product Design and Performance, Smolen and Ball (eds.), Wiley, New York (1984); Ranger and Peppas, J. Macromol. Sci. Rev. Macromol. Chem. 23:61 (1983); see also Levy et al., Science 228:190 (1985); During et al, Ann. Neurol. 25:351 (1989); Howard et al, J. Neurosurg. 71 : 105 (1989)). In yet another embodiment, a controlled release system can be placed in proximity of the therapeutic target, i.e., the brain, thus requiring only a fraction of the systemic dose (see, e.g., Goodson, in Medical Applications of Controlled Release, supra, Vol. 2, PP. 115-138 (1984)). Other controlled release systems are discussed in the review by Langer (Science 249:1527- 1533 (1990)).

The present invention also provides pharmaceutical compositions. Such compositions comprise a therapeutically effective amount of a compound capable of regulating GPRl activity or expression and a pharmaceutically acceptable carrier. In a specific embodiment, the term "pharmaceutically acceptable" means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other Generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like. Water is a preferred carrier when the pharmaceutical composition is administered intravenously. Saline solutions and aqueous dextrose and glycerol solutions can also be employed as liquid carriers, particularly for injectable solutions. The composition can be formulated as a suppository, with traditional binders and carriers such as triglycerides. Oral formulation can include standard carriers such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate, etc. Examples of suitable pharmaceutical carriers are described in "Remington's Pharmaceutical sciences" by E.W. Martin. Such compositions will contain a therapeutically effective amount of the Therapeutic, preferably in purified form, together with a suitable amount of carrier so as to provide the form for proper administration to the patient. The formulation should suit the mode of administration.

The amount of the compound of the invention which will be effective in the treatment of a particular disorder or condition will depend on the nature of the disorder or condition, and can be determined by standard clinical techniques. In addition, in vitro assays may optionally be employed to help identify optimal dosage ranges. The precise dose to be employed in the formulation will also depend on the route of administration, and the seriousness of the disease or disorder, and should be decided according to the judgment of the practitioner and each patient's circumstances. Effective doses may be extrapolated from dose response curves derived from in vitro or animal model test systems.

The invention also provides a pharmaceutical pack or kit comprising one or more containers filled with one or more of the ingredients of the pharmaceutical compositions of the invention, optionally associated with such container(s) can be a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, use or sale for human administration.

6. EXAMPLE: ISOLATION AND CHARACTERIZATION

OF THE GPRl GENE

The subsection below describes the isolation and characterization of a gene encoding a putative G-protein coupled receptor that is believed to provide the upstream signal that activates GPA2. The GPRl associated signaling pathway plays an essential role in inducing the switch from non-filamentous to filamentous growth in yeast.

6.1. MATERIALS AND METHODS 6.1.1 TWO HYBRID SCREEN AND YEAST METHODS Strains of S. cerevisiae utilized are indicated in Figure 2 A. The yeast were grown on YEPD (2% glucose) or YEP-Gal (3% galactose), and strains under selection were grown on synthetic dropout media, as described (Gutherie and Fink, 1991, Guide to Yeast Genetics and Molecular Biology. Academic Press, Inc. San Diego, Ca). pGBT9-GPA2, a plasmid containing the GPA2 gene, was transformed into reporter strain HF7c(Clontech) and the resulting strain was individually transformed with each of three yeast genomic DNA fusion libraries, Y2HL-C1, Y2HL-C2, and Y2HL-C3 (James et al., 1996, Genetics 144:1425-1436). Transformation mixtures were plated on medium lacking histidine, and positive transformants were retested for β-galactosidase expression by incubation in the presence of 0.3 mg/ml X-gal. GPRl -containing plasmids THl-10 and THl-12 were both isolated from library Y2HL-C1. Controls for non-specific protein interactions included co-expression of pGBT-GPA2 with a plasmid expressing a GAL4 activation domain fusion with SV40 large T-antigen and co-expression of THl-10 with a plasmid expressing GAL4 binding domain fusion with p53, both of which gave background levels of β-galatactosidase activity.

Yeast cells were sporulated by resuspending 0.1 ml of a saturated culture into 2.5 ml of sporulation medium (1% potassium acetate, 0.1% yeast extract, 0.05% glucose, 0.1 mM tryptophan, 0.2 mM leucine, 0.03 mM histidine, 0.05 mM uracil, and 0.07 mM adenine) and incubating them at 30°C with shaking for 3 days. Heat shock assays were performed by diluting an overnight saturated culture 1 :20 into fresh medium and incubating it at 30 °C with shaking for 2 days. 1 ml of this culture was then removed into a glass tube which was placed in a 50 °C water bath for 20 min. Heat shocked and non-heat shocked cultures were then diluted and plated for counting. Yeast cells were starved for nitrogen by growing them to log phase in

YEPD and transferring them to medium containing 4% glucose, 0.26 mM adenine, and 1.7% Difco Yeast Nitrogen Base without amino acids and ammonium sulfate for 24 hr, as described (Hirimburegama et al., 1992, J. Gen. Microbiol. 138:2035-2043). Addition of nitrogen to starved cells was performed by adding asparagiine and essential amino acids to the following final concentrations: 10 mM asparagine, 0.4 mM tryptophan, 0.9 mM leucine, and 0.13 mM histidine. Yeast transformations were performed by the lithium acetate method (Ito et al. 1983, J. Bact. 153:163-168) modified as described previously (Hirsch and Cross, 1993, Genetics 135:943-953). Yeast RNA was extracted from cells as described previously (Cross and Tinkelenberg, 1991, Cell 65:875-883).

6.1.2 IMMUNOBLOTS

Cell lysates were prepared by harvesting 12 ml of log phase cells, washing once with cold TE and resuspending in 150 μl of lysis buffer (50 mM Tris- HCl [pH 8.0], 1% SDS, 1 mM PMSF, 1 μg of apoprotin, leupeptin, chymostatin, and pepstatin per ml). The mixture was added to acid-washed glass beads (0.5 mm) and shaken at high speed for 10 min. Glass beads and cell debris were separated from the lysate by centrifugation in a microfuge for 2 min. Protein concentration of the samples was determined using a bicinchoninic acid protein assay kit (Pierce) and equal amounts were loaded onto SDS polyacrylamide gels (10% poly aery lamide). Separated proteins were transferred to nitrocellulose and the blot was probed with anti-GFP rabbit polyclonal antiserum at a dilution of 1 : 1000 or with anti-PGK rabbit polyclonal antiserum at a dilution of 1 :300,000. Donkey anti-rabbit immunoglobulin conjugated to horseradish peroxidase (Amersham) was used at a dilution of 1 :10,000 and immune complexes were detected with an enhanced chemiluminescence kit (Amersham).

6.1.3. NORTHERN BLOTS

RNA was transferred to a nitrocellulose membrane after formaldehyde- agarose gel electrophoresis as described (Lehrach et al, 1977, Biochemistry 16:4743- 4751). The membranes were UV cross-linked using a Stratalinker UV box. Prehybridization and hybridization were done at 65° C in a buffer containing 0.9 M NaCl, 0.09 M sodium citrate, 0.1 % Ficoll, 0.1% poly vinylpyrrolidone, 0.1% bovine serum albumin, 33 mM sodium pyrophosphate, 50 mM sodium phosphate monobasic. The probe used was a gel-purified DNA restriction fragment ³² P-labeled by random primer labeling using a Prime-It kit (Stratagene). The fragments used were a 1.4 kb Xbal-Mlul fragment from plasmid THl-10 and a 0.5 kb BamHI-Xbal fragment from pPGKl, which encodes phosphoglycerate kinase.

6.1.4. MICROSCOPY Cells containing the GPRl-GFP fusion protein were grown at room temperature and viewed using either the FITC filter for fluorescence microscopy or Nomarski optics for differential interference contrast microscopy on a Zeiss Axiophot microscope. They were photographed with a lOOx objective.

6.2. RESULTS 6.2.1. ISOLATION OF THE GPRl GENE To isolate other components of the GPA2 signaling pathway, a two- hybrid protein interaction screen (Fields and Song, 1989, Nature 340:245-246) was performed using GPA2 as the bait. Screening of a yeast genomic library with a GPA2 fusion construct resulted in the isolation of plasmids containing short segments of an uncharacterized gene that was given the name GPRl. The full-length GPRl gene encodes a protein of 961 amino acids (GenBank accession number Z74083) that is predicted to contain seven membrane-spanning domains, a feature characteristic of G protein-coupled receptors (Figure 1 A and B). The putative structure of this protein indicates that it would contain a very large third cytoplasmic loop of approximately 346 amino acids, and a large cytoplasmic tail of approximately 281 amino acids. The third cytoplasmic loop contains two copies of a short, basic sequence; one copy is present at the N-terminal end of the loop and the other copy is present at the C- terminal end (Figure IB and C). The third cytoplasmic loop also contains a poly- asparagine stretch of unknown function.

In contrast to the pheromone receptors, which have no homology to other receptors of this class, GPR can be aligned with the G protein-coupled receptor superfamily (Baldwin, 1993, EMBO J. 12:1693-1703). In particular, GPRl contains several amino acids in its transmembrane domains that are conserved within this superfamily. Of these, the most highly conserved residues are the alanine at position 193 in transmembrane domain 4, the phenylalanine at position 262 in transmembrane domain 5, the tryptophan at position 634 in transmembrane domain 6, and the tyrosine at position 676 in transmembrane domain 7 (Figure IB). When these residues are positioned with respect to the predicted arrangement of the receptor transmembrane α- helices (Baldwin, 1993,EMBO J. 12:1693-1703), they all face away from the surrounding membrane lipid and toward the center of the molecule or the other helices. Intramolecular interactions between these transmembrane α-helices are thought to maintain the structure of the receptor in the membrane and allow it to bind the G protein.

Two GRβl-containing plasmids were isolated in the two-hybrid screen; one contained the coding region for the C-terminal 122 amino acids and the other contained the coding region for the C-terminal 99 amino acids (Figure IB). The cytoplasmic tail regions of several mammalian G protein-coupled receptors have also been shown to interact with G_α subunits, although in these cases the membrane- proximal region of the cytoplasmic tail contains the G_α-binding activity (O'Dowd et al., 1988, J. Biol. Chem. 263:15985-15992; Kδnig et al., 1989, Proc. Natl. Acad. Sci. USA 86:6878-6882; Munch et al., 1991, Eur. J. Biochem. 198:357-364; Ohyama et al., 1992, Biochem. Biophys. Res. Comm. 189:677-683; Hawes et al., 1994, J. Biol. Chem. 269:15776-15785). The finding that the C-terminal end of the GPRl cytoplasmic tail interacts with GPA2 suggests that other G_α subunits may also interact with this region of their associated receptors. If the assays used previously to measure α-subunit /receptor binding are less sensitive than the two-hybrid assay, this area of contact could have been overlooked.

6.2.2 GPRl ACTS UPSTREAM OF GPA2 To determine if GPRl acts in the same signaling pathway as GPA2, a diploid strain heterozygous for GPRl and RAS2 deletion alleles was sporulated and tetrads were dissected. Strains containing single gprl or rasl mutations grew normally, but strains containing both Agprl and ά.ras2 mutations displayed a severe growth defect (Figure 2B). The slow growth rate of t,gprl &ras2 strains was essentially identical to that seen in Agpa2, ts.ras2 strains, suggesting that GPRl and GPA2 function in the same process. An experiment was therefore performed to determine the effect of different GPA2 alleles on the growth rate of a Agprl Aras2 strain. A single copy plasmid containing GPA2 had no effect on the growth rate of the Agprl Aras2 strain; however, multicopy GPA2 partially suppressed the growth defect of this strain (Figure 2C). Moreover, the constitutive GPA2^R273A allele in single copy completely suppressed the growth phenotype of the Agprl Aras2 strain. The most straightforward interpretation of these results is that GPA2 acts downstream of GPRl in the same signaling pathway, as would be expected for a G_α subunit and its associated receptor. In addition, the finding that Agpa2 and Agprl mutations produce the same degree of growth inhibition in a Aras2 strain suggests that GPR is the only receptor that is coupled to GPA2. The idea that GPRl and GPA2 act in the same signaling pathway is also supported by the finding that the growth defect of a Agpa2 Agprl Aras2 is no more severe than that of a Agpa2 Aras2 strain.

6.2.3. GPRl IS NOT REQUIRED FOR GPA2 EXPRESSION OR BASAL ACTIVITY The genetic experiment that places the function of GPRl upstream of

GPA2 is consistent with more than one possible relationship of their gene products. As mentioned above, a likely possibility is that GPRl encodes the receptor that couples to GPA2. However, alternative possibilities are that the GPRl gene product is required for the expression of the GPA2 gene or that it is required to maintain the stability or activity of the GPA2 protein. To test these possibilities, the effect of GPA2 on heat shock sensitivity was determined in cells lacking GPRl function.

Wild type cells carrying a single copy plasmid with the constitutive GPA2^R273A allele under its own promoter (scGPA2*, Figure 2D) were 13-fold more sensitive to heat shock than cells carrying vector alone. Expression of GPA2^R273A conferred a similar increase in heat shock sensitivity on Agprl cells. If the function of GPRl gene product were to promote efficient expression of the GPA2 gene, then a null allele of GPRl would be expected to decrease the expression of GPA2 ^R273A and thus decrease its ability to confer heat shock sensitivity. These results therefore demonstrate that GPRl is not required for efficient expression of GPA2. Overexpression of the wild type GPA2 gene by expressing it from the GAPDH promoter on a multicopy plasmid conferred a modest 2-fold increase in heat shock sensitivity on wild type cells (mcGPA2, Figure 2D). Overexpression of GPA2 also conferred about a 2-fold increase in heat shock sensitivity on Agrpl cells when compared to vector alone in the same cells. Therefore, the basal activity of GPA2 is maintained in the absence of a functional GPRl gene, suggesting that GPRl is not required for the stability or activity of the GPA2 protein.

Strains containing the Agprl mutation and wild type GPA2 were slightly more sensitive to heat shock than the corresponding GPRl strains, suggesting that the GPA2 pathway is activated to a low level in Agprl strains. This phenotype can be compared to deletion of the pheromone receptor gene STE3, which confers about a 2-fold increase in the basal activity of the pheromone response pathway (Boone et al, 1993, Proc. Natl. Acad. Sci. USA 90:9921-9925). Therefore, these results are entirely consistent with the assignment of Grelp as the receptor that couples to GPA2.

6.2.4 GPRl IS LOCALIZED TO THE CELL SURFACE If GPRl is a member of the G protein-coupled receptor family, then it should be located at the cell surface. To determine the subcellular location of GPRl, the GPRl gene was fused with the coding sequence of green fluorescent protein (GFP; Chalfie et al. , 1994, Science 263 :802-805) and transformed into wild type cells. The GPRl-GFP construct complemented the growth defect of a Agprl Aras2 strain, demonstrating that the fusion gene is fully active. Cells expressing GPRl-GFP showed a cell surface staining pattern, demonstrating that GPRl is localized at the plasma membrane (Figure 3). In addition to cell surface staining, a portion of the signal appeared in discrete foci within cells, suggesting that Grelp may also be located on intracellular vesicles.

6.2.5 MEMBRANE PROXIMAL REGIONS OF THE GPRl AND

THIRD CYTOPLASMIC LOOP ARE REQUIRED FOR FUNCTION A number of studies have demonstrated that G protein-coupled receptors contain sequences in the membrane-proximal regions of their third cytoplasmic loops that are required for coupling to the G protein (Baldwin, 1994, EMBO J. 12:1693-1703). The GPRl third cytoplasmic loop contains the sequences KRIKAQIG near its N-terminal end and KKRRAQIQ near its C-terminal end (Figure IB and C, boxed). A related sequence is present in the third cytoplasmic loop of the S. cerevisiae pheromone receptors, which have very short third cytoplasmic loops. Mutation of some these residues in the α-factor receptor affects its ability to couple to the GPA1 G_α subunit without affecting its ability to bind ligand (Clark et al, 1994, J. Biol. Chem. 269:8831-8841). Likewise, the pheromone receptors from Schizosaccharomyces pombe have a related sequence in their third cytoplasmic loops (Kitamura and Shimoda, 1991, EMBO J. 10:3743-3751; Tanaka et al, 1993, Mol. Cell. Biol. 13:80-88). An alignment of these sequences is shown in Figure 4A.

To test whether the membrane-proximal regions of the third cytoplasmic loop of GPRl are required for its function, each of these regions was individually deleted from the GPRl coding sequence. GPRl mutations in which the coding region contained a deletion of eight amino acids at the N-terminal region

(residues 277-284) or C-terminal region (residues 610-617) of the third cytoplasmic loop were unable to complement the growth defect of a Agprl Aras2 strain (Figure 4B). The third cytoplasmic loop of also contains a long stretch of poly-asparagine residues (Figure IB, boxed). To determine whether this asparagine-rich sequence is required for GPRl function, a GPRl mutation containing a deletion of this region (residues 490-586) was also constructed. The GPRl^d490-^m gene was able to complement the growth defect of a Agrpl Aras2 strain (Figure 4B).

The abundance and localization of the mutant GPRl proteins was investigated by tagging each construct with GFP. To determine the relative abundance of the mutated versions of GPRl , an immunoblot containing cell extracts from strains expressing each of the GPRl deletions was probed with anti-GFP antiserum. The GPRl^d277-²⁸⁴, GPRl^d490-⁵⁹⁶, and GPRl⁰⁶'^0'6'⁷ constructs all expressed proteins at a level equal to or higher than the wild type expression level (Figure 4C, lanes 2-5). Localization of the mutated versions of GPRl was determined by observing cells expressing the GFP-tagged versions of the proteins by fluorescence microscopy. The GPRl^d277-²⁸⁴, GPRl^0490'596, and GPRl^d6'°-⁶'⁷ constructs all expressed proteins that were localized to the cell surface (Figure 4D). These results demonstrate that deletion of an internal region of the GPRl third cytoplasmic loop that encompasses 97 amino acids has no effect on the function of GPRl, but that deletion of the membrane-proximal regions of this loop abolishes the function of GPRl. This evidence supports the idea that GPRl is a member of the G protein-coupled receptor family.

It was also of interest to determine whether the region of GPRl that encodes the cytoplasmic tail of the protein is required for its function because this portion of GPRl was isolated in the two-hybrid screen based on its interaction with GPA2. However, constructs that deleted most of the GPRl cytoplasmic tail (residues 694-954) or the smaRest region that was isolated in the two-hybrid screen (residues 841-954) did not produce a protein product that was detectable by immunoblot (Figure 4C, lanes 6, 7), so this region appears to be important for some step in the production or stabilization of GPRl .

6.2.6 GPRl RNA IS INDUCED IN RESPONSE

TO NITROGEN STARVATION AND AMINO ACIDS To test whether the GPRl gene is regulated by the availability of- nutrients, the effect of nitrogen starvation on the abundance of GPRl RNA was determined. RNA samples were isolated from cells in log phase, from cells that had been starved for nitrogen and essential amino acids for 24 hr, and from starved cells to which asparagine and essential amino acids had been added back for 2 hr. The abundance of GPRl RNA increased to a very high level in cells starved for nitrogen and amino acids compared to its abundance in cells growing in log phase (Figure 5, lanes 1, 2). Addition of essential amino acids and asparagine, an efficient nitrogen source, to starved cells caused a decrease in the abundance of GPRl RNA (Figure 5, lane 3). Cells starved for a carbon source did not display induction of GPRl RNA, suggesting that this induction is not a general response to growth arrest. In addition, there was no difference in the abundance of GPRl RNA in cells growing on a fermentable carbon source compared to cells growing on a non-fermentable carbon source. To determine whether induction of GPRl RNA requires amino acid starvation, a strain that is prototrophic for all amino acids was starved solely for nitrogen. Likewise, an auxotrophic strain was starved for nitrogen in the presence of essential amino acids. In both of these cases, GPRl RNA was not induced (Figure 5, lanes 4-9), indicating that amino acid starvation is necessary for this response. The induction of GPRl RNA therefore appears to be a specific response to nitrogen and amino acid deprivation.

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of the appended claims. Various references are cited herein, the disclosures of which are incorporated by reference in their entireties.

Claims

1. A purified GPRl protein.

2. The protein of claim 1 which is a yeast protein.

3. The protein of claim 2 which is a Saccharomyces cerevisiae 5 protein.

4. The protein of claim 1 which comprises the amino acid sequence substantially as set forth in Figure IB (SEQ ID NO:2).

5. A purified protein encoded by a nucleic acid hybridizable to the 10 GPRl DNA sequence as set forth in Figure 1A (SEQ ID NOT).

6. A purified derivative or analog of the protein of claim 1 , which displays one or more functional activities of a GPRl protein.

7. A purified fragment of a GPRl protein comprising a domain of the GPRl protein selected from the group consisting of: the

15 extracellular domain; transmembrane domain ;cytoplasmic domain or cytoplasmic tail domain.

8. A chimeric protein comprising a fragment of a GPRl protein consisting of at least 6 amino acids fused via a covalent bond to an amino acid sequence of a second protein, in which the

20 second protein is not a GPRl protein.

9. An antibody which is capable of binding a GPRl protein.

10. The antibody of claim 9 which is monoclonal.

11. An isolated nucleic acid comprising a nucleotide sequence encoding a GPRl protein.

12. The nucleic acid of claim 11 which is a DNA.

13. An isolated nucleic acid comprising a nucleotide sequence complementary to the nucleotide sequence of claim 11.

14. The nucleic acid of claim 11 in which the GPRl protein is a yeast GPRl protein.

15. The nucleic acid molecule of claim 11 in which the GPRl protein is a Saccharomyces cerevisiae GPRl protein

16. An isolated nucleic acid comprising the GPRl coding sequence as set forth in Figure 1 A.

17. An isolated nucleic acid hybridizable to the GPRl DNA sequence indicated in Figure 1 A and coding for a protein having the functional activity of GPRl .

18. An isolated nucleic acid comprising a nucleotide sequence encoding a fragment of a GPRl protein that displays one or more functional activities of the GPRl protein.

19. An isolated nucleic acid comprising a nucleotide sequence encoding the chimeric protein of claim 8.

20. An isolated nucleic acid comprising a nucleotide sequence encoding a protein, said protein comprising the amino acid sequence of Figure IB (SEQ ID NO:2).

21. A recombinant cell containing the nucleic acid of claim 11.

22. A recombinant cell containing the nucleic acid of claim 13.

23. A recombinant cell containing the nucleic acid of claim 14.

24. A recombinant cell containing the nucleic acid of claim 18.

25. A method of producing a GPRl protein comprising growing a recombinant cell containing the nucleic acid of claim 1 1 such that the encoded GPRl protein is expressed by the cell, and recovering the expressed GPRl protein.

26. A method of producing a chimeric GPRl protein comprising growing a recombinant cell containing the nucleic acid of claim 18 such that the encoded chimeric GPRl protein is expressed by the cell, and recovering the expressed chimeric GPRl protein.

27. A method of producing a GPRl protein comprising growing a recombinant cell containing the nucleic acid of claim 16 such that the encoded GPRl protein is expressed by the cell, and recovering the expressed GPRl protein.

28. A method of producing a protein comprising a fragment of a GPRl protein, which method comprises growing a recombinant cell containing the nucleic acid of claim 17 such that the encoded protein is expressed by the cell, and recovering the

5 expressed protein.

29. A pharmaceutical composition comprising an effective amount of a GPRl protein; and a pharmaceutically acceptable carrier.

30. The composition of claim 29 in which the GPRl protein is a yeast GPRl protein.

10 31. A method of treating or preventing a disease or disorder involving a fungal infection in a subject comprising administering to a subject in which such treatment or prevention is desired an effective amount of a molecule that regulates GPRl function.

15 32. The method according to claim 31 in which the subject is human.

33. A method of treating or preventing a disease or disorder involving a fungal infection in a subject comprising administering to a subject in which such treatment or

20 prevention is desired an effective amount of a molecule that inhibits GPRl function.

34. The method according to claim 33 in which the molecule that inhibits GPRl function is selected from the group consisting of an anti-GPRl antibody or a fragment or derivative thereof

25 containing the binding region thereof, a GPRl antisense nucleic acid, and a nucleic acid comprising at least a portion of a GPRl gene into which a heterologous nucleotide sequence has been inserted such that said heterologous sequence inactivates the biological activity of at least a portion of the GPRl gene, in 5 which the GPRl gene portion flanks the heterologous sequence so as to promote homologous recombination with a genomic GPRl gene.

35. A method of identifying a molecule that specifically binds to a ligand selected from the group consisting of a GPRl protein, a

10 fragment of a GPRl protein comprising a domain of the protein, and a nucleic acid encoding the protein or fragment, comprising (a) contacting said ligand with a plurality of molecules under conditions conducive to binding between said ligand and the molecules; is and (b) identifying a molecule

15 within said plurality that specifically binds to said ligand.

36. A method of for identifying a compound capable of modulating GPRl activity, comprising: a. contacting a compound to a cell that expresses a GPRl gene; b. measuring the level of GPRl activity in the cell; and 20 c. comparing the level obtained in (b) to the level of GPRl activity obtained in the absence of the compound; such that if the level obtained in (b) differs from that obtained in the absence of the compound, a compound capable of modulating a GPRl activity has been identified.

25 37. The method of claim 36 wherein the activity is filament formation in yeast.

38. The method of claim 36 wherein the level of GPRl activity obtained in the absence of the compound is increased.