AU2003200860B2 - Orphan receptor - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): KARO BIO AB Invention Title: ORPHAN RECEPTOR The following statement is a full description of this invention, including the best method of performing it known to

US:

la ORPHAN RECEPTOR This invention relates to cellular nuclear receptors and their uses..

A large family of nuclear receptors which confer cells with responsiveness to molecules such as retinoid acid, vitamin D, steroid hormones and thyroid hormones has been identified. Extensive studies have shown that the members of this superfamily of nuclear receptors activate and/or repress gene transcription through direct binding to discrete cis-acting elements termed "hormone response elements" (HRE). It has been shown that these HRE's comprise repeats of consensus palindromic hexanucleotide DNA motifs. The specificity of the HRE's is determined by the orientation of, and spacing between, halfsites (i.e:.half a palindromic sequence)(Umenesono et al, 1991 Cell 65, 1255-1266).

Specific DNA binding is mediated by a strongly-conserved DNA binding domain, containing two zinc fingers, which is conserved among all thus discovered nuclear receptors. Three amino acids at the C-terminal base of the first zinc finger (known as the "P-box") are important for the recognition of the half site nucleotide sequence. Members of the nuclear receptor superfamily have been classified into different groups on the basis of the amino acid sequence within the P box.

All members of the nuclear receptor superfamily also contain a hypervariable N-terminal domain and a ligand-binding domain containing some "patches" of conserved sequence.

One of these is called the "Ti-domain".

2 Molecules which are thought to be nuclear receptors, as they are structurally related to characterised receptors, but for which no ligand has been found, are termed "orphan receptors". Many such orphan receptors have been identified (see for example Evans R.M. (1988) Science 240, 889-895 and O'Malley, B.(1990) Mol. Endocrinol. 4 363-369).

We have now unexpectedly identified, initially in rat a new orphan receptor, which is related to the known estrogen receptor ERa, and which we have designated "ERp" (specifically "rER" in rat). In this specification "ERp" will be used to refer to the receptors hERO or rER or related receptors. The nucleotide and amino acid sequences of rERP have now been determined and are shown in Fig. 1.

We have also identified a human Erp "hERP", the amino acid DNA and sequences of which are shown in Fig. 13A and 13B respectively.

According to one aspect of the invention there is provided a novel estrogen receptor-related nuclear receptor, hereinafter termed "ERp" having the amino acid sequence of Figs. 1, Fig. 13A or 14A or substantially the same amino acid sequence as the amino acid sequence shown in Figs. 1, 13A or 14A or an amino acid sequence functionally similar to those sequence. The isolated receptor may be particularly useful in the search for molecules for use in treatment of diseases or conditions such as cardiovascular diseases, central nervous system diseases or conditions or osteoporosis, prostate cancer or benign prostatic hyperplasia.

The receptor of the invention may also be used in the testing of environmental chemicals for estrogenic activity. There has been increasing concern over the effect of various chemicals released into the environment on the reproduction of humans and animals.

Threats to the reproductive capabilities of birds, fish, reptiles, and some mammals have become evident and similar effects in humans have been proposed. Substantial evidence is now emerging which shows that exposure to certain chemicals during critical periods of foetal life may distort the development of the reproductive organs and the immune and nervous systems. On the basis of possible parallels between actual wildlife effects, seen for example in birds and seals living in highly polluted areas, and proposed effects in humans, in combination with documented human reproductive effects caused by prenatal exposure to the pharmaceutical estrogen, diethyl stilbestrol (DES), "estrogenic" chemicals have been proposed to threaten the reproductive capability of both animals and humans.

Among the chemicals known or suspected to act as estrogen mimics on the human body, or in other ways disturb the human endocrine system, there are several which have already been identified as environmental hazards. Among the chemicals that have been mentioned as potential causes of disruption of reproductive function in animals and humans are chlorinated organic compounds such dieldrin, endosulfans, chlordanes, endrins, aldrin, DDT and some PCBs, plastics such as Bisphenol A, phthalates and nonylphenol, and aromatic hydrocarbons. Some of the proposed effects on humans have been suggested to be due to an increasing exposure to environmental estrogens in fact, exposure to chemical compounds to which higher organisms during the foetal period react in a way that is similar to when they are exposed to high dosages of estrogens. The effects are manifested by for example perturbations of the sex characteristics and impaired reproductive potential. In humans, elevated risks of breast cancer and other hormone-related disease has also been discussed as possible effects. In addition, to the documented "estrogenic" effects, it has recently been demonstrated that environmental pollutants may also act on hormonal pathways other than the estrogenic pathway it has been shown that p,p' DDE the main metabolite of DDT (also in humans) is a fairly antiandrogenic agent (Kelce W.R. et al Nature 1995 375:581-585). Epidemiological studies on these issues are, however, presently difficult to interpret. Nevertheless, there is a growing opinion against these potentially hormone disrupting chemicals, and very palpable public and environmental demand for the governmental agencies and industry to act. In view of the similarities between the receptor of the present invention, Erp and the classical estrogen receptor, Erp may be used in the testing of chemicals for estrogenic effect.

An amino acid sequence functionally-similar to the sequence shown in Fig. 1, 13A or 14A may be from a different mammalian species.

An amino acid sequence which is more than about 89%, identical with the sequence shown in Fig. 1, 13A or 14A is substantially the same amino acid sequence for the purposes of the present application. Preferably, the amino acid sequences is more than about 95% identical with the sequence shown in Fig. 1, 13A or 14A.

Accordingto another aspect of the invention there is provided a DNA sequence encoding a nuclear receptor according to the first aspect of the invention. Preferably, the DNA sequence is that given in Fig. 1, 13A or 14A or is a DNA sequence encoding a protein or polypeptide having the functionality of ERp.

ER3 is unique in that it is extremely homologous to the rat estrogen receptor, in particular in its DNA binding domain. It appears that ERO has a very limited tissue distribution. In 20/06 2006 16:19 FAX 61 8 9221 4196 GRIFFITH HACK PERTH 1io

INO

c- female rats, it appears to be present only in the ovaries, and in male rates in the prostate and testes. As these tissues are classic targets for estrogen action, it can be odeduced that ER may mediate some of the effects of estrogen.

0The different ligand specificity of ERa and ER may be O0 exploited to design pharmaceutical agents which are oselective for either receptor. In particular, the (N 10 differences in ligand specificity may be used to develop Mdrugs that specifically target cardiovascular disease in 0postmenopausal women or osteoporosis.

ci Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and 'comprises", means "including but not limited too, and is not intended to exclude other additives, components, integers or steps".

By 'consisting of" is meant including, and limited to, whatever follows the phrase "consisting of". Thus, the phrase 'consisting of" indicates that the listed elements are required or mandatory, and that no other elements may be present. By "consisting essentially of" is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase "consisting essentially of" indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they affect the activity or action of the listed elements.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part fl:\uOctrKMae\R~tYPe\pqmniS Nuepdud c1&imu KPAO DIV JUne 200E.doC 20/Od/06 COMS ID No: SBMI-03926526 Received by IP Australia: Time 18:44 Date 2006-06-20 20/06 2006 16:20 FAX 61 8 9221 4196 GRIFFITH HACK PERTH So1011l 5a of the common general knowledge in the art, in Australia or any other country.

The nuclear receptor of the invention, ERP, a method of producing it, and tests on its functionality will now be described, by way of example only, with reference to the accompanying drawings, Figs. 1 to 15 in which: Fig. 1 shows the amino acid sequence of ERp and the nucleotide sequence of the gene encoding it; Fig. 2A is a phylogenetic tree showing the evolution of ERP and other receptors; Fig. 2B shows the homology between the different domains in ERp and certain other receptors; Fig. 2C is an alignment of the amino acid sequence in the ligand binding domains of rERp, rERa, mERa, and hERa; Fig. 2D is an alignment of the amino acid sequence in the DNA binding domains of rERp, rERn, mERa and hERa; E:\ter\zx \M.\Rbype\P4B769 A ed Ulmin KAIO DIV Juni 3IDG.doc 20/06/OS COMS ID No: SBMI-03926526 Received by IP Australia: Time 18:44 Date 2006-06-20 Fig. 3A is a film autoradiograph of prostate gland showing strong expression of a clone of the receptor of the invention, clone 29; Fig. 3B is a darkfield image showing prominent signal for clone 29 in epithelium of prostatic alveoli. The stroma(s) exhibit(s) weaker signal; Fig. 3C is a bipolarization image of cresyl violet counterstained section showing silver grains over epithelium whereas the stroma(s) contain(s) less grains; The bar represents 0.7 mm for Fig. 3A, 200 pm for Fig. 3B and 30 pm for Fig. 3C; Fig. 4A shows a film autoradiograph of ovary showing strong expression of clone 29 in follicles at different developmental stages (some are indicated by arrows). The interstitial tissue (arrowheads) shows low signal; Fig. 4B shows a darkfield image showing high expression of clone 29 in granular cells of primary secondary tertiary and mature follicles. Low signal is present in interstitial tissue (it); Fig. 4C is a bipolarization image of ovary a showing strong signal in granular cells (gc), whereas the oocyte (oc) and the cainterna (ti) are devoid of clear signal; The bar represents 0.9 mm for Fig. 4A, 140 pm for Fig. 4B and 50 pm for Fig. 4C; Fig. 5A illustrates the results of saturation ligand binding analysis of cloned ERP; Fig. 5B illustrates the specificity of ligand binding by cloned ER; Fig. 5C illustrates E2 binding by ERP; Fig. 6 illustrates the activation of transcription by cloned ER3; Fig. 7 and 7A illustrates stimulation by various ligands by cloned ER3; Fig. 8 illustrates the results of RT-PCR experiments on the expression of rat estrogen receptors; Fig. 9 illustrates the results of RT-PCR experiments on the expression of human Erp (hERP); Fig. 10A is a Hill plot comparing binding of 125 I-E2 by hERcc and rERP; Fig. 10B is a Scatchard plot comparing binding of 1 25 I-E2 by hERac and rERP; Fig. 11A illustrates the relative binding affinity ofhERa and rERP for various ligands; Fig. 11B is a detail of Fig. 12A; Fig. 12 is an alignment of various estrogen receptors; Fig. 13A shows the amino acid sequence of human ERO; Fig. 13B shows the DNA sequence of human Erp; Fig. 14A shows the amino acid sequence of mERP; Fig. 14B shows the DNA sequence of mouse Erp; and Fig. 15 illustrates ligand binding affinities for various phytoestrogens by ER's of the invention.

A. CLONING OF RAT ERB 1, PCR-amplification and complementary DNA cloning.

A set of degenerate primers (DBD 1,2,3 and WAK/FAK) were designed previously according to the most highly conserved sequences of the DNA-binding domain(Pbox) and ligand binding domain (Ti-stretch) of members of the nuclear receptor family (Enmark, Kainu, Pelto-Huikko, Gustafsson, J-A (1994) Biochem. Biophys. Res. Commun. 204, 49-56). Single strand complementary DNA reverse transcribed from rat prostate total RNA was employed with the primers in PCR reactions as described in Enmark, Kainu, Pelto-Huikko, Gustafsson, J-A (1994) Biochem. Biophys. Res. Commun. 204, 49-56. The amplification products were separated on a 2% low melting agarose gel and DNA products between 400 and 700 bp were isolated from the gel and ligated to TA cloning vector (Invitrogen). As alternatives, we also used the RP-IRP-2 and DBD66-100/DBD210-238 primer sets in the DNA-binding domain of nuclear receptors exactly as described by Hirose Fijimoto, Yamaai, Kim, K.H., Matsuura, Jetten, A.M (1994) Mol. Endocrinol. 8, 1667-1677 and Chang, C., Lopes Da Silva, Ideta, Lee, Yeh, Burbach, J.P.H (1994) Proc. Natl.

Acad. Sci. 91, 6040-6044 respectively. Clone number 29 (obtained with the DBD-WAK/FAK set) with a length of 462 bp showed high homology with the rat estrogen receptor cDNA which was previously cloned from rat uterus (Koike, Sakai, Muramatsu, M. (1987) Nucleic Acids Res 2499-2513). The amino acid residues predicted by clone 29 DNA sequences suggested that this DNA fragment encoded part of the DNA-binding domain, hinge region and the beginning of the ligand binding domain of a novel member of the nuclear receptor family. Two PCR primers (Figure 1) were used to generate a probe of 204 bp consisting of the hinge region of the novel receptor, which was used to screen a rat prostate cDNA library (Clontech gtl0) under stringent conditions resulting in four strongly positive clones with a size of 0.9 kb, 1.8kb and 5-6kb respectively. The clone of 2.5kb was sequenced and Figure 1 shows the nucleotide sequence determined in the core facility (CyberGene AB) by cycle sequencing using fluorescent terminators (Applied Biosystems) on both strands, with a series of internal primers and deduced amino acid sequence of clone 29. Two in frame ATG codons are located at nucleotide 424 and nucleotide 448, preceding by an in-frame stop codon at nucleotide 319, which suggests that they 06/03 2003 17:04 FAX 61 8 9221 4196 GRIFFITH HACK PERTH Z002 9 are possible start codons. The open reading frame encodes a protein of 485 amino acid residues (counted from the first methionine) with a calculated molecular weight of 54.2 kDa. Analysis of the proteins by synthesized by in-vitro translation from the clone 29 cRNA in rabbit reticulocyte lysate revealed a doublet protein baud migrating at approximately 57 kDa on SDS-PAGE gels (data not shown), confirming the open reading frame. The doublet protein band is probably caused by the use of both ATG codons for initiation of protein synthesis. The amino acid sequence of clone 29 protein shows the characteristic zinc module DNA-binding domain, hinge region and a putative ligand binding domain, which are the characteristic features of members of the nuclear receptor family (Trsai, O'Malley, B.W (1994) Ann. Rev. Biochem. 63, 451-486; Hird, Gustafsson, J-A (1993) Acc. Chem. Res. 26, 644-650; Laudet, HiAni, Coli, Catzeflis, Stehelin, D (1992) EMBLJ. 11, 1003- 1012).

Protein sequence comparison with several representative members of the nuclear receptor family (Figure 2) showed the clone 29 protein is most related to the rat estrogen receptor (ERot), cloned from uterus (Koike, Sakai, Muramatsu, M. (1987) Nucleic. Acids Res. 15, 2499-2513), with 95% identity in the DNA-binding domain (amino acid residues 103-167) (Griffiths, KC, Davies, P.p.

Eaton, Harper, Turkes, Peeling, W.B. (1991) in Endocrine Dependent Tunours, eds. Voigt, K-D. Knabbe, C. (Raven Press), pp. 83-125).

A number of functional characteristics have been identified within the DNA-binding domain of nuclear receptors (Hard, Gustafsson, J-A. (1993) Ace. Chem. Res 26, 644-650 and Zilliacus, Carlstedt-Duke, Gustafsson, J-A., Wright, A.P.H. (1994) Proc. Natl. Acad. Sci. USA 91, 4175-4179). The so-called P-box specifies nucleotide sequence recognition of the core half-site within the response element, while the D- box mediates dimerization between receptor monomers. The clone 29 protein P-box and D-box sequences of EGCKA and PATNQ, respectively, are identical to the corresponding boxes in ERa (Hiird, Gustafsson, J-A. (1993) Acc. Chem. Res 26, 644-650 and Koike, Sakai, Muramatsu, M. (1987) Nucleic Acids Res. 15, 2499-2513), thus predicting that clone 29 protein binds to ERE sequences.

The putative ligand binding domain (LBD) of clone 29 protein (amino acid residues 259-457) shows closest homology to the LBD of the rat ERa (Figure 2), while the homology with the human ERRI and ERR2 proteins (Giguere, Yang, Segui, Evans R.M. (1988) Nature 331, 91-94) is considerably less. With the human, mouse and xenopus estrogen receptors the homology in the LBD is also around 55%, while the homology with the LBD of other steroid receptors is not significant (Figure Cysteine residue 530 in human ERa has been identified as the covalent attachment site of an estrogenic affinity label (Harlow, Smith Katzenellenbogen, Greene, Katzenellenbogen, B.S. (1989) J.

Biol. Chem. 264, 17476- 17485). Interestingly, clone 29 protein (Cys-436) as well as the mouse, rat and xenopus ERos have a cysteine residue at the corresponding position. Also, two other amino acid residues described to be close to or part of the ligand-binding pocket of the human ERa-LBD (Asp 426 and Gly 521) are conserved in the LBD of clone 29 protein (Asp 333 and Gly 427) and in the LBD of ERas from various species (20,21). The ligand-dependent transactivation function TAF-2 identified in ERa (Danielian, White, Lees, Parker, M.G. (1992) EMBO J. 11, 1025-1033), which is believed to be involved in contacting other transcription factors and thereby influencing activation of transcription of tarteg genes, is almost completely conserved in clone 29 protein (amino acid residues 441-457). Steroid hormone receptors are phosphoproteins (Kuiper, Brinkmann, A.O. (1994) Mol. Cell. Endocrinol. 100, 103-107), and several phosphorylation sites identified in the N-terminal domain and LBD of ERa (Arnold, Obourn, Jaffe, Notides. A.C. (1995) Mol.

Endocrinol. 9, 24-33 and Le Goff, Montano, Schodin, Katzenellenbogen, B.S (1994) J Biol. Chem. 269, 4458-4466) are conserved in clone 29 protein (Ser 30 and 42, Tyr 443). Clone 29 protein consists of 485 amino acid residues while ERcs from human, mouse and rat consist of 590-600 amino acid residues. The main difference is a much shorter N-terminal domain in clone 29 protein i.e 103 amino acid residues as compared to 185-190 amino acid residues in the other receptor proteins. Also the non-conserved so-called F-domain at the C-terminal end of ERas is 15 amino acid residues shorter in clone 29 protein. The cDNA insert of a positive clone of 2.6 kb was subcloned into the EcoR1 site of pBluescript (trademark) (Stratagene). The complete DNA sequence of clone 29 was determined (CyberGene AB) by cycle sequencing using fluorescent terminators (Applied Biosystems) on both strands, with a series of internal primers.

Figs 2C and 2D respectively compare the ligand and DNA binding domain of Erp compared to rat, mouse and human Era's.

2. Saturation ligand binding analysis and ligand competition studies: Clone 29 cDNA was subcloned in pBluescript downstream of the T7 promoter to give p29-T7. Clone 29 protein was synthesized in vitro using the TnT-coupled reticulocyte lysate system (Promega). Translation reaction mixtures were diluted five times with TEDGMo buffer (40 mm Tris/HC1, pH 7.4, ImM EDTA, glycerol, 10 mM Na 2 MoO 4 10 mM DTT) and 0.1 ml aliquots were incubated for 16 h at 80 C with 0.3- 6.2 nM [2,4,6,7- 3 H]-17p-estradiol (NEN-Dupont; specific radioactivity 85 Ci/mmol) in the presence or absence of a 200-fold excess of unlabelled E2.

Fig. 5A illustrates the results of a saturation ligand analysis of clone 29 protein.

Reticulocyte lysate containing clone 29 protein was incubated with 6 concentrations of 3 H]E2 between 0.3 and 6.0 nM. Parallel tubes contained an additional 200 fold of non-radioactive E2. Bound and free ligand were separated with a dextran-coated charcoal assay. The Kd (0.6 nM) was calculated from the slope of the line in the Scatchard plot shown (r 0.93), and the number of binding sites was extrapolated from the intercept on the abscissa (Bmax 1400 fmol/ml undiluted translation mixture).

For ligand competition studies diluted reticulocyte lysate was incubated with 5 nM [2,4,6,7- 3 H]-17p-estradiol in the presence of either 0, 5, 50, 500 or 5,000 nM of non- radioactive E2, estrone, estriol, testosterone, progesterone, corticosterone, Saandrostane-33,17p-diol, 5a-androstanc-3a, 17p-diol and diethylstilbestrol (DCES) for 16 h at 8 0 C. Bound and unbound steroids were separated with a dextran-coated charcoal assay (Ekman, Barrack, Greene, Jensen, Walsh, P.C (1983) J. Clin. Endocrinol Metab. 57, 166-176).

Fig. 5B illustrates the specificity of ligand binding by clone 29 protein.

Reticulocyte lysate containing clone 29 protein was equilibrated for 16 h with nM 3 H]E2 and the indicated fold excess of competitors. Data represent [H]E2 bound in the presence of unlabelled E2, testosterone progesterone (prog), corticosterone (cortico), estrone diethylstilbestrol (DES), 5a-androstane-3a, -17P-diol (3a-AD), 5a-androstane- 3P,17p-diol (3p-AD) and estriol ['H]E2 binding in the absence of competitor was set at 100%.

3. In-situ hybridisation: In-situ hybridisation was carried out as previously described (Dagerlind A., Friberg, Bean, Hkfelt, T (1992) Histochemistry 98, 39-49). Briefly, two oligonucleotide probes directed against nucleotides 994-1041 and 1981-2031 were each labelled at the 3'-end with 3 P-dATP using terminal deoxynucleotidyltransferase (Amersham, UK). Adult male and female Sprague-Dawley rats (age 2 to 3 months n=10) were used for this study. The T ts were decapitated and the tissues were rapidly excised and frozen on dry ice. The tissues were sectioned in a Microm HM500 cryostat at 14 gm and thawed onto Probe-On glass slides (Fisher Scientific, PA, USA). The slides were stored at 0 C until used. The slides were incubated in humidifed boxes at 42 0 C for 18 h with 1x10 6 cpm of the probe in a hybridization solution containing formamide, 4 x SSC (1 x SSC 0.15 M NaCI, 0.015 M sodium citrate), 1 x Denhardt (0.02 BSA, 0.02 Ficoll, 0.02 PVP), I sarkosyl, 0.02 M sodium phosphate (pH 10% dextransulphate, 500 pg/ml salmon sperm DNA and 200 mM DTT. Slides were subsequently rinsed in 1 x SSC at 55C for 60 min with four changes of SSC and finally in 1 x SSC starting at 55°C and slowly cooled to room temperature, transferred through distilled water and briefly dehydrated in and 95% ethanol for 30 sec each, air-dried, and covered with Amersham P-man autoradiography film for 15 to 30 days. Alternatively the slides were dipped in Kodak NTB2 nuclear track emulsion (diluted 1:1 with distilled water) and exposed for 30 to 60 days at 4 0 C. Finally, the sections were stained with cresyl violet.

Clear expression of clone 29 was observed in the reproductive tract of both male and female rats, while in all other rat tissues the expression was very low or below the level of detection with in-situ hybridisation (not shown). In male reproductive organs high expression was seen in the prostate gland (Figure while very low expression was observed in testis, epididymis and vesicula seminalis (not shown).

In dipped sections, expression was clearly visible in prostate epithelial cells (secreting alveoli) while the expression in smooth muscle cells and fibroblastsin the stroma was low (Figure In female reproductive organs expression was seen in the ovary (Figure while uterus and vagina were negative (not shown). In dipped sections high expression was seen in the granulosa cell layer of primary, secondary and mature follicles (Figure whereas primordial follicles, oocytes and corpora lutea appeared completely negative. Low expression was seen in the interstitial cells of the ovary. Both anti-sense oligonucleotide probes used produced similar results. Addition of a 100 fold excess of the respective unlabelled oligonucleotide probes during the hybridisation reactions abolished all signals.

4. Transactivation analysis in CHO-cells: The expression vector pCMV29 was constructed by inserting the 2.6 kb clone 29 fragment in the EcoRI site of the expression vector pCMV5 (Andersson, Davis, Dahlbick, Jirnvall, Russell, D.W. (1989) J. Biol. Chem. 264, 8222- 8229). The pERE-ALP reporter construct contains a secreted form of the plancental alkaline phosphatase gene (Berger, Hauber, Hauber, Geiger, Cullen, B.R. (1988) Gene 66, 1-10) and the MMTV-LTR in which the glucocorticoid response elements were replaced by the vitellogenin promoter estrogen response element (ERE).

CHO-K1 cells were seeded in 12-well plates at approximately 1.7 x 105 cells per well in phenol-red free Ham F12 medium with 5% FCS (dextran-coated charcoal treated) and 2 mM Lglutamine. After 24 h the cells were transfected with 250 ng pERE-ALP vector and 50 ng pCMV29 using lipofectamine (Gibco) according to the manufacturer's instructions. After five hours of incubation the cells were washed and refed with 0.5 ml phenol-red free Coon's F-12 medium containing,% serum substitute (SRC 3000, Tissue Culture Services Ltd., Botolph Claydon, Buckingham, UK) 2 mM Lglutamine and 50 pg/ml gentamicin plus hormones as indicated. After 48 h the medium was assayed for alkaline phosphatase (ALP) activity by a chemiluminescence assay. A 10 pl aliquot of the cell culture medium was mixed with 200 pl assay buffer (10 mM diethanolamine pH 10.0 1 mM MgC12 and 0.5 mM CSPD (Tropix Inc. Boston, USA)) and incubated for 20 min at 37 C before measurement in a microplate luminometer (Luminoskan; Labsystems, Finland) with integral measurement for 1 second. The ALP activity of ERE-reporter alone was set at 1.

Ligand binding characteristics and transactivation function of clone 29 protein: On the basis of the described high homology between clone 29 protein and rat ERol in the DBD and LBD it was hypothesized that clone 29 protein might encode a novel ER. Furthermore, biological effects of estrogens on rat prostate and ovary, which show high expression of clone 29 RNA, are well known (Griffiths, K., Davies, Eaton, C. Harper, Turkes, Peeling W. B. (1991) in Endocrine Dependent Tumours, eds Voigt, K-D. Knabbe, C. (Raven Press), pp 83-125; Richards, J.S (1994) Endocrine Rev. 15, 725-745; and Habenicht, U-F., Tunn, Senge, Th., Schroder, Schweikert, Bartsch, El Etreby, M.F. (1993) J. Steroid Biochem. Molec. Biol. 44, 557-563). In order to analyze the steroid binding properties of clone 29 protein synthesized in vitro, the reticulocyte lysate was incubated at 8 0 C for 16 h with increasing concentrations (0.3-6.0 nM) of 3 H]E2 in the presence or absence of a 200 fold molar excess of unlabelled E2. Linear transformation of saturation data revealed a single population of binding sites for E2 with a Kd (dissociation constant) of 0.6 nM (Figure 5A and Steroid binding specificity was measured by incubating reticulocyte lysate with 5 nM ['H]E2 in the presence of 0.5, 50, 500 and 5,000 nM unlabelled competitors. Competition curves generated are indicative of an estrogen receptor in that only estrogens competed efficiently with ['H]E2 for binding (Figure 5B). Fifty percent inhibition of specific binding occured by 0.6 fold excess of unlabelled E2; diethylstilbestrol, estriol, estrone and 5a-androstane-3p, 17p-diol were 5, 15, 50 and 150 times, respectively, less effective as competitors. Neither testosterone, progesterone, corticosterone nor 5c- androstane-3a,17p-diol were efficient competitors, even at the highest concentrations used (1000 fold excess).

The dissociation constant and the steroid binding specificities measured are in good agreement with data previously reported for ERs in rat and human prostate, rat granulosa cells, rat antral follicles and whole rat ovarian tissue (Ekman, P., Barrack, Greene, Jensen, Walsh. P.C (1983) J. Clin.

Endocrinol. Metab. 57, 166-176; van Beurden-Lamers, Brinkmann, A.O., Mulder, van der Molen, H. (1974) Biochem. J 140, 495-502; Kudolo, G.B., Elder, Myatt, L. (1984) J. Endocrinol. 102, 83-91; and Kawashima, Greenwald, G.S. (1993) Biology ofReprod. 48 172-179).

When clone 29 protein was labelled with a saturating dose of 3 H]E2 and analyzed on sucrose density gradients, a single peak of specifically bound radioactivity was observed. The sedimentation coefficient of this complex was about 7S, and it shifted to 4S in the presence of 0.4 M NaCl (not shown). To investigate the transcriptional regulatory properties of clone 29 protein, we performed co-transfection experiments in which CHO cells were transfected with a clone 29 protein expression vector and/or an estrogen-responsive reporter gene construct.

Cells were incubated in the absence ofE2 (clone 29) or in the presence of 100 nM E2 (Clone 29 E2) or in the presence of 100 nM E2 and 12 pM Tamoxifen (Clone 29 E2/Tam). In the absence of exogenously added E2 clone 29 protein showed considerable transcriptional activity which could be further increased by the addition of 100 nM E2 (Figure Simultaneous addition of a 10 fold excess of the antiestrogen Tamoxifen partially suppressed the E2 stimulated activity (Figure 6).

The constitutive transcriptional activity of clone 29 protein could be suppressed by the anti-estrogen ICI-1624384 (not shown). It has been shown previously that the wild-type mouse and human ERs are constitutive activators of transcription, and that the transcriptional activity can be stimulated further by the addition of E2 (Txukerman, Xiao-Kun Zhang., Hermann, Wills, K. Graupner, Phal, M. (1990) New Biologist 2, 613-620 and Lees, Fawell, Parker, M.G. (1989) Nucl. Acids Res. 17, 5477-5488). To obtain more insight into what concentrations of E2 effect clone 29 protein transcriptional activity, transient transfection experiments were carried out in the presence of increasing concentrations ofE2. CHO-cells were transiently transfected with the ERE-reporter plasmid and the clone 29 protein expression plasmid. Cells were incubated with increasing concentrations of E2 (0.1 1000 nM), estrone (El, 1000 nM), So-androstane-3P,17p-diol (3P-AD, 1000 nM) or no ligand added. Alkaline phosphatase activity (ALP) was measured as described and the activity in the absence of ligand (control) was set at 1. The figure shows relative ALP-activities from three independent experiments. Clone 29 protein began to respond at 0.1 nM E2 and maximal stimulation was observed between 1 nm and 10 nM E2 (Figure The maximal stimulation factor was 2.6 0.5 fold (mean SD. n 9) as compared to incubation in the absence ofE2. Apart from E2 also estrone and 3P,17p-diol could stimulate transcriptional activity, albeit at higher concentrations (Figure Dexamethasone, testosterone, progesterone, 5a-androstane-3a, 17p-diol, thyroid hormone and all-trans-retinoic acid could not stimulate transcriptional activity of clone 29 protein, even at the highest concentration (1000 nM) tested (not shown). The results of the co-transfection experiments are in agreement with the ligand binding and specificity data of clone 29 protein presented in Figure 5. In control experiments, wild-type human ERa also showed transcriptional activity in the absence of E2, which could be increased by the addition of E2 (not shown).

6. Detection of rat ER expression by RT-PCR The tissue specificity of expression of rat ERp and ERa was determined using reverse transcriptase polymerase chain reaction (RT-PCR). The results of the experiment are shown in Fig. 8.

B. Isolation of human Erp 1. A human version of Erp (hERP) has also been cloned from human ovary. The tissue specificity of hER3 expression in a variety of cells was also determined using the RT-PCR technique. The results are shown in Fig. 9. It will be noticed that there is a very high level of mRNA of hERp in human umbilical vein endothelial cells (HUVEC) but no detection ofhERa in the same cells. In addition, it will be seen that in human osteosarcoma cell line (HOS-D4), hERp is expressed in greater quantities compared to hERa.

I. A human version of ERp (hERp) has also been cloned. The tissue specificity of hERp expression in a variety of cells was also determined using the RT-PCR technique. The results are shown in Fig. 9. It will be noticed that there is a very high level of mRNA of hER[ in human umbilical vein endothelial cells (HUVEC) but no detection of hERoc in the same cells. In addition, it will be seen that in human osteosarcoma cell line (HOS-D4), hER3 is expressed in greater quantities compared to hERa.

The partial DNA sequence of hER3 is shown in Fig. 10 and a derived amino acid sequence is shown in Fig. 11.

Cloning of human Erp from testis A commercially available cDNA from human testis (Clontech, article no.

HL1161x) was screened, using a fragment containing the ligand-binding domain of the rat Erp cDNA as probe. Approximately 106 recombinants were screened, resulting in one positive clone. Upon sequencing of this clone, it was seen that the insert was 1156 bp (Figure 13A and 13B). This corresponds to most of the translated region of a receptor with an overall homology of 90.0% to rat Erp, therefore deduced to represent the human form of Erp.

The cloned hERP, however, lacks approximately 47 amino acids at the N-terminal end and 61 amino acids at the C- terminal end (as compared to the rat sequence). Further screening of the same library was unsuccessful.

PCR technology was therefore used to obtain the remaining parts. For oligonucleotides were sunthesised; two degenerate oligonucleotides containing all possible codons for the amino acids adjacent to the initiation methionine and the stop codon, respectively, of the rat Erp, and two specific oligonucleotides containing the sequence of the clone isolated from the human testis library and situated approximately 100 bp from respective end of this clone. PCR with the N-terminal and C-terminal pair of oligos yielded specific bands, that were subcloned and sequenced. The parts of these new clones that overlap the original cDNA clone are identical to this.

-It was thus possible to construct peptide and DNA sequences corresponding to the whole open reading frame (Fig. 13A and 13B).

When comparing the human Erp to rat Erp, this receptor is 79.6% identical in the N-terminal domain, 98.5% in the DNA-binding domain, 85.6% in the hinge and 91.6% in the ligand-binding and F-domains. These numbers match very well those found when comparing the rat and human forms of Era.

Studies of the expression of human Erp using Northern blot show expression in testis and in ovaries. The expression in prostate, however, appears lower than found in the rat.

The human Erp gene has been mapped to chromosome 14 using PCR and to region 14q22-23 using the FISH technique, whereas the human Erp gene has been mapped to chromosome 6q25.

2. Comparison of ligand binding affinity of hERa and rERp The ligand affinity of the two estrogen receptors, human Era (ovary) (hERa) and rat Erp (rERp) was tested in binding saturation experiments and in binding competition experiments.

cDNA of the receptor subtypes hERa and rERp were in vitro translated in rabbit reticulocyte lysate in presence of non-radioactive amino acids according to the instructions supplied by the manufacturer (Promega).

The radioactive ligand used in all experiments was 16a-[' 1 I]-17P-estradiol 25 I]-E2) (NEX- 144, New England Nuclear). The method for the binding experiments was previously described in: Salomonsson M, Carlsson B, Haggblad J. J. Steroid Biochem. Molec. Biol. Vol. 50, No. 5/6 pp. 313-18, 194. In brief, estrogen receptors are incubated with to equilibrium (16-18 h at The incubation was stopped by separation of protein-bound 2 I]-E2 from free 2 I]-E2 on Sephadex G25 columns.

The radioactivity of the eluate is measured in a gamma-counter.

In the competition experiments, non-radioactive ligands were diluted in DMSO, mixed with (approximately 100-200 pM), aliquoted in parallel, and finally hERoc or rERp was added. The final concentration of DMSO in the binding buffer was 2%.

The buffer used in the experiments was of the following composition: Hepes (pH=7.5) 20 mM, KC1 150 mM, EDTA 1 mM, glycerol monothioglycerol 6 mM, Na 3

MO

4 3. Equilibrium binding saturation experiments (KI-determinations) A range of concentrations of 2 5 I]-E2 were mixed with the ER:s and incubated as described above, free [L 25 I]-E2 was determined by substracting bound ['2I]-E2 from added Binding data was analysed by Hill-plots and by Scatchard plots (Figure 11). The equilibrium binding results are shown in Table 1. The apparent Kd-values for 25 I]-E2 differed between the two ER:s with approximately a factor of four; Kd(hERa):Kd(rERP) 1:4.

Table 1. Equilibrium dissociation constants for [t 2 sI]-E2 to the two subtypes.

Receptor subtype Kd (Hill-plot) Kd (Scatchard-plot) hERa 0.06 nM 0.09 nM rERp 0.24 nM 0.42 nM 4. Competition experiments (ICso determinations) The experiments were performed as described above. IC 5 0 values were obtained by applying a four parameter logistic analysis; where I is the added concentration of binding inhibitor, IC 5 0 is the concentration of inhibitor at half maximal binding and S is a slope factor. The free concentration of 125 I]-E2 was determined by sampling an aliquot from the wells at the end of the incubation and then substract bound radioactivity from sampled total radioactivity.

Since the equilibrium binding experiments (above) showed that the Kd-values for 25 ]-E2 differed between the two ER:s, K-values (from the Cheng-Prusoff equation: Ki=ICo/(l+LIKd) where L is free 25 were calculated for the compounds investigated. Two approaches for calculating RBA (Relative Binding Affinity) were used. The RBA values were derived using either the ICso values or the K, values. In both approaches, the value for the compound 16a-bromo-estradiol was selected as the reference value Both approaches gave similar results. The results are summarized in Figure 12. In these Figures "4-OH-Tam" 4-hydroxy-tamoxifen; "DES" diethylstilbestrol; "Hexestr" hexestrol; "ICI-164384" ICI pic compound no. 164382; "17P-E2" 17p-estradiol; "16a-B- E2" 16a-bromo-estradiol; "Ralox" Raloxifen; and "17a-E2"= 17a diol.

The results show that Era and Erp have significant different ligand binding affinities the apparent Kd-values for 2 I]-E2 differed between the two ER's by a factor of about 4 (Kd(hERa): Kd (rERP) Some compounds investigated showed significant differences in the competition for binding of 2 1I]-E2 to the ER's. Certain compounds were found to be more potent inhibitors of ['5I]-E2 binding to hERa as compared to rERp whereas others were found to be more potent inhibitors of 25 I]-E2 binding to rERP than to hERcc.

The entire disclosure in the complete specification of our Australian Patent Application No.

69880/96 is by this cross-reference incorporated into the present specification.

Claims (8)

1. An isolated estrogen receptor (called ERA) consisting of the amino acid sequence of Fig. 1. 0 ci

2. An isolated estrogen :receptor (called ERY) consisting of the amino acid secuence which is more than identical to the amino acid sequence shown in Pig. 1. 00 o 3. An isolated estrogen 'receptor (called ERP) consisting of the amino acid sequence of Fig. 13A. 0 4. An isolated estrogen receptor (called ERA) consisting of the amino acid sequence of Fig. 14A. is 5. An estrogen receptor according to any one of claims 1 to 4 which is derived, from mammalian cells.

6. An estrogen receptor according to claim S which is derived from rat or hman cells.

7. An isolated DNA sequence encoding an isolated estrogen receptor according to any one of claims 1 to 6. B. An isolated DNA sequence according to claim 7 in which the DNA sequence is one of those Figs 1, 13B or 14B.

9. The use of an estrogen receptor according to any one of claims 1 to 6 or a DNA sequence according to claim 7 or claim 8, in an assay to determine molecules which bind an estrogen receptor according to any one of claims I to 6. The use of an estrogen receptor according to any one of claims 1 to 6 or a DNA sequence according to claim 7 or claim 8, in an assay to determine molecules for use in the treatment of ERP specific diseases or conditions or H:\t-ryr\Xco\te\p4B76, Aneftsd Clam. XARO DIV Jima 2006f4Cc 30106/06 COMS ID No: SBMI-03926526 Received by 1P Australia: Time 18:44 Date 2006-06-20 20/06 2006 16:20 FAI 61 8 9221 4196 GRIFFITH HACK PERTH [013 0 -64 0 CA diseases or conditionis related to an estrogen receptor Saccording to any one of claims 1 to 6. o

11. A method of treating an ER3 specific disease or condition or a disease or condition related to an estrogen receptor according to any one of claims 1 to S6, comprising the step of administering to a subject an NO 00 estrogen receptor according to any one of claims 1 to 6 Sor a DNA sequence according to claim 7 or claim 8. eN S12. The use of an estrogen receptor according to any one of o claims 1 to 6 or a DNA sequence according to claim 7 or claim 8, in an assay to determine molecules for use in the treatment of prostate or ovarian cancer, benign prostatic hyperplasia, diseases of the central nervous system, osteoporosis,'or cardiovascular disease.

13. A drug design method comprising comparing binding of a test compound to ERa and to an estrogen receptor according to any one of claims 1 to 6.

14. The use of an estrogen receptor according to any one of claims 1 to 6 in the testing of the possible estrogenic or other hormonal effects of a substance. An isolated receptor according to any one of claims 1 to 4 substantially as hereinbefore described with reference to any one of the examples. Dated this 20 th day of June 2006 KARO 1BO AB By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\tmrrYXyr \ap\«:emype\VM Amenied Claim xfa ziv June 2006.do 2i0/t6/06 COMS ID No: SBMI-03926526 Received by IP Australia: Time 18:44 Date 2006-06-20