Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/46—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates
  • C07K14/47—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates from mammals
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/28—Drugs for disorders of the nervous system for treating neurodegenerative disorders of the central nervous system, e.g. nootropic agents, cognition enhancers, drugs for treating Alzheimer's disease or other forms of dementia
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/68—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids
  • G01N33/6893—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids related to diseases not provided for elsewhere
  • G01N33/6896—Neurological disorders, e.g. Alzheimer's disease
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2800/00—Detection or diagnosis of diseases
  • G01N2800/28—Neurological disorders
  • G01N2800/2814—Dementia; Cognitive disorders
  • G01N2800/2828—Prion diseases

Definitions

• the present invention relates to methods for the detection or isolation of prion proteins by use of chaperones specifically binding to said proteins. -The invention further relates to a method for in-vitro diagnosis of a transmissible spongiform encephalopathy and to pharmaceutical compositions, preferably for the prevention or treatment of said disease.
• TSEs Transmissible spongiform encephalopathies
• BSE bovine spongiform encephalopathy
• CJD Creutzfeldt-Jakob disease
• Infectious preparations derived from infected brains are resistant to ultraviolet and ionizing radiation as well as other procedures which inactivate nucleic acids indicating that nucleic acids may not be required for infectivity.
• Purification of infectious preparations from brains revealed the presence of a protein required for infectivity (36).
• Prions consist mainly of a protease resistant protein designated PrpSc (prion protein, 'Sc' for scrapie), a posttranslationally modified form of the proteinase K sensitive host encoded PrP c ('c' for cellular) (8, 9, 11 , 34). Both isoforms share the same amino acid sequence, but differ in their secondary structure (31 , 42). Circular Dichroism (CD) and Fourier Transform Infrared (FTIR) spectroscopy revealed a significantly higher ⁇ -sheet content for p r pSc as compared to a high ⁇ -helix content in PrP c (17, 31 , 38).
• CD Circular Dichroism
• FTIR Fourier Transform Infrared
• the technical problem underlying the present invention is to provide a simple method for the efficient isolation of prion proteins and the detection of said proteins, preferably in a way that allows for discrimination between different isoforms of PrP.
• the present invention relates to a method for the detection of a prion protein comprising the steps of:
• the present invention relates to a method for the isolation of a prion protein comprising the steps of:
• Hsp60 binds specifically to Hsp60 in an S. cerevisiae environment as well as in vitro.
• the Hsp60 family is one of the best characterized members of the molecular chaperones which mediate ATP-dependent folding of polypeptide chains (13, 18, 22, 23) and which are widely distributed and conserved between prokaryotes and mammals.
• Human Hsp60 (544 amino acids) is proposed to form tetradecameric complexes in vivo as shown in the crystal structure of the prokaryotic homologue GroEL (10).
• cerevisiae (15, 19, 21 ) encode N-terminally truncated proteins of 399, 317 and 246 amino acids in length, comprising at least in part the apical domain of the Hsp60 monomer. This apical domain contains several amino acid residues which specifically mediate peptide binding in the case of GroEL (14).
• PrP c /Hsp60 interaction in vivo was confirmed employing the 'false baits' LexA-bicoid and LexA-NFI/CTF2 as well as authentic LexA and LexA-
• PrP c /Hsp60 interaction does not involve additional factors and that thus, chaperones can be used for the detection and isolation of prion proteins.
• the recombinant rPrP27-30 (47) represents the proteinase K sensitive isoform of the proteinase K resistant core PrP27-30 isolated from scrapie preparations.
• the results of the in vitro interaction between rPrP27-30 and Hsp60 reveal that the core region of PrP (amino acids 90 to 231 ) is sufficient for binding to Hsp60.
• Hsp60 might be involved in the propagation of PrpSc as has been shown for the interaction of the yeast prion-like factor [psi*] with the "" molecular chaperone Hsp104 (12, 50). Based on studies with transgenic mice, it has been suggested recently that a species-specific macromolecule, designated 'protein X', participates in prion formation (43). Protein X was proposed to function as a molecular chaperone facilitating the transformation of PrP isoforms. This unknown factor 'X' might in fact be Hsp60. (ii) Alternatively, Hsp60 could prevent aggregation of PrP c to PrpSc amyloids e.g. by trapping misfolded forms of PrP c .
• Prion proteins can be extracted from natural sources, for example, by the method described in (31 , 64); involving suspending tissue in sucrose, homogenization and clarification by centrifugation.
• Contacting the probe suspected to contain a prion protein with a chaperone can be carried out by known methods, for example, with the chaperone being in solution or being immobilized, for example on a matrix such as a gel or a resin for chromatography (66).
• Suitable chaperones which specifically bind to prion proteins can be inter alia determined by the person skilled in the art by assaying the binding of a particular chaperone to prion proteins as described in the Examples, below.
• a fragment, analogue or derivative of said chaperone is used which is still capable of binding the prion protein.
• derivative refers to such derivatives which may be prepared from the functional groups which occur at side chains on the residues or the N- or C-terminus groups, by means known in the art.
• fragment relates to any fragment of the chaperone which still has the capability to interact with the prion protein and such a fragment can be prepared by techniques known to the person skilled in the art.
• the chaperone used in the method for detection and/or isolation of a prion protein is Hsp60 or GroEL.
• the chaperone is a recombinant protein, i.e., the chaperone is produced by recombinant DNA technology, namely by expression from a cloned DNA sequence.
• the chaperone is part of a fusion protein, which can comprise, besides the chaperone a protein or preferably, a protein domain which confers to the fusion protein a specific binding capacity.
• the recombinant chaperone is fused to glutathione-S-transferase.
• any prion protein, isoform, fragment or derivative of such prion protein or mixture of said substances can be detected or isolated by the method of the invention as long as it is capable of being bound by the chaperone.
• the prion protein to be detected or isolated is the prion protein PrP c and/or an isoform of PrP c .
• the prion protein isoform is the isoform PrP sc or a fragment or derivative thereof.
• the prion protein is the processed form PrP c 23- 231 comprising amino acids 23 to 231 of PrP sc and/or the isoform PrP sc is the N- terminally truncated derivative PrP27-30 or a fragment thereof.
• the chaperone can be in solution or be attached to a solid phase.
• the interaction can, for example, be proved by (i) crosslinking employing reagents such as dimethylsuberimidate (52), (ii) by affinity chromatography (66) by adding the immobilized ligand directed against one of the tags fused to one of the both partners (Criss-Cross interactions), or (iii) by analyzing the complex by a non-denaturing polyacrylamid gel (53) or by a size exclusion chromatography which is mostly HPLC/FPLC (54).
• the chaperone is in solution and detectably labelled.
• the person skilled in the art will know suitable labels or will be able to ascertain such labels using routine experimentation.
• the detectable label is selected from a radioisotope, a fluorescent compound, a colloidal metal, a chemiluminescent compound, a bioluminescent compound, a phosphorescent compound or an enzyme.
• the chaperone is bound to a solid phase for the detection and/or isolation of a prion protein.
• Suitable materials are known to the person skilled in the art and include, for example, a gel or a resin (Sepharose, agarose, nitrocellulose, dynabeads ® , polystyrene etc.).
• the solid phase is a matrix comprising glutathione, such as glutathione-sepharose.
• the protein domain used for binding of the chaperone to a matrix can a so e an o igo st ne 5 , a mo u n n ng peptide (CBP) (56), S-peptide (ribonuclease A) (57), FLAG (58), green- fluorescent protein (GFP, 65), BTag (59), or maltose-bi ⁇ ding-protein (MBP; 61 ).
• the tagged chaperone can be immobilized to gluthathione, IMAC-Ni 2+ ' Calmoduiin, S-protein 104 aa (57), anti-FLAG-antibodies, anti GFP-antibodies, BTag-antibodies (59) or maltose (60).
• coupling of the chaperone itself by the fusion protein can be done via thiol-groups of non-oxidized cysteins or, alternatively, via free lysine or ⁇ - amino groups to cyanogen bromide agarose or ⁇ -hydroxy succinimide activated agarose (63).
• the interaction can be determined by IASYS (FISONS). Protein-protein interactions can be detected and measured by biosensors, which use the evanescent field to probe biomolecular mass and concentration close to the probe surface. Alternatively, such interaction can be determined by far western blot/affinity blot (62): the prion-protein either tagged or untagged or the chaperone either tagged or untagged are blotted onto a membrane such as nitrocellulose or PVDF. The other interaction partner either the tagged/untagged prion protein or the tagged/untagged chaperone in solution is incubated with the protein associated membrane. Interaction is confirmed by addition of an antibody directed against the protein in solution itself or the tag fused to the protein (62).
• the chaperone is part of a matrix contained within an affinity chromatography column (63, 66) and step (b) is modified in such a way that (i) the probe suspected to contain the prion protein is passed through the column, (ii) after washing, the prion protein is eluted from the column, optionally by a change in pH or ionic strength and collected; and (iii) optionally the collected prion protein is further purified.
• the isolation of the prion protein is carried out as a batch process according to standard procedures or, for example, by using a modified version of the procedure described in the Examples, below, wherein instead of the prion protein, the chaperone is attached to glutathione-Sepharose beads, for example, gluthathione-Sepharose 4B beads.
• Prion proteins isolated and purified according to the method of the invention can be used, for example, as immunogen for raising antibodies, as active component of pharmaceutical compositions or for the development of diagnostic assays, such as ELISA.
• the probe can be obtained from various organs, preferably from tissue, for example brain, ileum, cortex, dura mata, purcinje cells, lymphnodes, nerve cells, spleen, tonsils, muscle, cells, placenta, pancreas eyes, backbone marrow or peyer'sche plaques or from a body fluid, preferably from blood, cerebrospinal fluid, semen or milk.
• tissue for example brain, ileum, cortex, dura mata, purcinje cells, lymphnodes, nerve cells, spleen, tonsils, muscle, cells, placenta, pancreas eyes, backbone marrow or peyer'sche plaques or from a body fluid, preferably from blood, cerebrospinal fluid, semen or milk.
• a further preferred embodiment o the nvent on re ates to a met o for the in-vitro diagnosis of a transmissible spongiform encephalopathy, wherein step (b) is modified in such a way that the differences in binding of the chaperone to PrP c and an isoform of PrP c , respectively, preferably PrP sc , are used to determine whether an isoform of PrP c is present in the probe or not.
• the present invention furthermore provides a complex of the chaperone and a prion protein and, in addition, a composition for the detection and/or isolation of a prion protein comprising a chaperone as defined above.
• the present invention relates to a diagnostic composition
• a diagnostic composition comprising the chaperones as defined above.
• Such compositions may contain additives commonly used for diagnostic purposes.
• Said compositions can be used for the diagnosis of transmissible spongiform encephalopathies by applying the approach described above, wherein a probe taken from a body is incubated with a chaperone and the strength of binding of the chaperone to the prion protein contained in the probe is determined.
• diagnosis is often carried out post mortem but is, in certain cases, also possible on the living organism (biopsy).
• biopsy living organism
• diagnosis is possible for living individuals.
• the present invention relates to a pharmaceutical composition
• a pharmaceutical composition comprising a chaperone as defined above or, alternatively, comprising a substance that inactivates said chaperone.
• Such compositions can optionally comprise pharmaceutically acceptable carriers.
• chaperons like Hsp60 are assumed to be capable of preventing the aggregation of PrP c to PrP sc , it might be possible to block the conversion of the isoform PrP c into the prion associated isoform PrP sc by administration of such chaperones which specifically bind prion proteins and, thus, to prevent or treat transmissible spongiform encephalopathy.
• chaperones are involved in the transformation of PrP c to PrP sc .
• blocking such transformation by the administration of agents which specifically inactivate such chaperones which specifically interact with prion proteins could also be helpful for the treatment or prevention of transmissible spongiform encephalopathies.
• Such substances can be selected by the person skilled in the art by routine experimentation and include ligands that bind to the chaperone, thus preventing the interaction of the chaperone with the prion protein.
• ligands are antibodies, preferably monoclonal antibodies, or a fragment of a protein which a domain responsible for binding to the chaperone, e.g. a fragment of PrP c containing amino acids 180 to 210.
• compositions are used for the prevention or treatment of transmissible spongiform encephalopathy, for example, Scrapie, bovine spongiform encephalopathy (BSE), Creutzfeld-Jacob Disease (CJD), Gerstmann- Strau ⁇ ler-Scheinker-Syndrome (GSS), Kuru, fatal familial insomnia (FFI) or transmissible mink encephalopathy (TME).
• transmissible spongiform encephalopathy for example, Scrapie, bovine spongiform encephalopathy (BSE), Creutzfeld-Jacob Disease (CJD), Gerstmann- Strau ⁇ ler-Scheinker-Syndrome (GSS), Kuru, fatal familial insomnia (FFI) or transmissible mink encephalopathy (TME).
• Figure 1 Identification of PrP c 23-231/Hsp60 interaction employing the two- hybrid system.
• Yeast cells containing the reporter plasmid pSH18-34 were cotransformed with the pJG4-5 plasmid carrying the cDNA clone encoding for Hsp60 (amino acids 146-544) and the bait plasmids pSH2-1 (row 1 ), pSH2-1-GST (row 2), pSH2-1-GST-PrP C (row 3), pSH2-1-
• NFI/CTF2 (row 4) (49), pEG202-bicoid (row 5) (21 ) and pSH2-1-Prp C -GST (row 6).
• Five of each transformants were resuspended in TE, dotted on galactose plates either supplemented with X-Gal (A) or leucine deficient (B) and incubated at 30° C for 5 days.
• FIG. 2. Immunoblot analysis of pull-down assays to demonstrate the in vitro interaction of Hsp60 and GroEL in the presence of PrP fused to GST.
• GST-rPrP27-30 (2 mg) as well as GST-PrP c (2 mg) immobilized on glutathione- Sepharose were incubated with 10 mg Hsp60. After centrifugation beads were washed and resuspended in sample buffer. 4 ml each of GST-PrP c (lane 2), GST-rPrP27-30 (lane 3) and GST (lane 4) as well as 200 ng Hsp60 as a control (lane 1 ) were analyzed by SDS-PAGE (12.5 %) and immunoblotting (PVDF) employing a monoclonal mouse anti-Hsp60 antibody and chemiluminescence detection.
• PVDF immunoblotting
• Figure. 3 Mapping the PrP c /GroEL interaction site using fragments of PrP c as fusions with GST.
• PrP c cassette was cloned via EcoRI/BamHI restriction sites into vectors pSH2-1 and pEG202, yielding pSH2-1/pEG202-PrP c .
• the GST-PrP c cassette was excised from this vector using the EcoRI and Sa/I restriction sites and cloned into pEG202, resulting in pEG202-GST-PrP c .
• Example 2 Expression of the 'bait' protein LexA-GST-PrP c in S. cerevisiae strain EGY48
• GST glutathione S-transferase
• Example 3 Identification of PrP c /Hsp60 interaction by the two-hybrid screen.
• yeast strain EGY48 (MATa ura3 his3 trpl LEU2::LexAop6-LEU2), which carries a chromosomal insertion of LexA binding sites upstream of the LEl/2-gene was used as the recipient host (19, 21).
• yeast strain EGY48 was transformed with the reporter plasmid pSH 18-34 containing a LexA controlled lacZ gene as a second reporter.
• cerevisiae cells were cotransformed with the 'bait'-plasmid and pJG4-5 containing a HeLa cDNA library fused to the acidic B42 transactivation domain (19, 21 ).
• the cDNA insert of the pJG4-5 plasmid is controlled by a galactose inducible promoter. Therefore, interaction between the two hybrids occurs only in the presence of galactose.
• cDNAs of 55 positive clones were recovered from 5 ml S. cerevisiae cell cultures. Cells were incubated at 30° C for 2 days, harvested by centrifugation (3000 rpm, 10 min at 4° C) and washed (1 M sorbitol, 0,1 M EDTA, pH 8.0). After resuspension in SCE (1 M sorbitol, 0,1 M sodium citrate, pH 5.8, 10 mM EDTA, 0,1 M b-mercaptoethanol) the cells were incubated with 40 ml Lyticase (5 U/ml, Sigma) for 1 h at 37° C.
• TE-lysis buffer 50 mM Tris/HCI, pH 7.4, 20 mM EDTA containing 1% SDS
• the lysate was phenol extracted, the DNA ethanol precipitated and resuspended in TE.
• the DNA was transformed in E. coli strain KC8 which enables the selection of pJG4-5 plasmids by ampicillin resistance and complementation of its tryptophan auxotrophy (19, 21 ).
• the plasmids were retransformed in EGY48 and the transformants tested for b- galactosidase production and for their Leu + -phenotype.
• cDNA inserts were sequenced with the T7-sequencing kit (Pharmacia) based on the dideoxy method (41 ). Homology searches for the cDNA sequences were performed at the National Center for Biotechnology Information using the BLAST network service
• Hsp60 heat shock protein 60
• the isolated Hsp60 cDNAs encode for three N-terminally truncated proteins with different lengths starting at position aa 146, aa 228 and aa 298, respectively (EMBL M34664). All of them contain parts of the putative peptide binding domain of Hsp60 (14).
• PrP c lacking GST strongly interact with Hsp60.
• LexA-GST (Fig. 1 , row 2)
• authentic LexA (Fig. 1 , row 1 )
• LexA-bicoid (Fig. 1 , row 5) showed no interaction with Hsp60.
• Example 5 Recombinant Hsp60 binds specifically to PrP c 23-231 and rPrP27-30 in vitro.
• PrP c 23-231 represents the mature form of the cellular prion protein.
• Scrapie prion isolates consist mainly of the protease-resistant core which is 27 30 kDa in size (referred to as PrP27-30) (35, 42), comprising amino acids 90 to 231.
• PrP27-30 the protease-resistant core which is 27 30 kDa in size (referred to as PrP27-30) (35, 42), comprising amino acids 90 to 231.
• PrP27-30 27 30 kDa in size
• GST as well as PrP c 23-231 and rPrP27-30 fused to GST (47, 48) were immobilized and incubated with Hsp60. Hsp60 was detected in the presence of GST-PrP c (Fig.
• GST Proteins and antibodies.
• GST::P180-210 and GST::P218-231 were prepared as described (48).
• GST::rPrP27-30 (aa 90 to 231 of the Syrian Golden Hamster prion protein) was expressed in and purified from E. coli and from the baculovirus expression system (47). GroEL and anti-rabbit-lgG-POD as well as anti-mouse-lgG-POD
• Example 6 Binding of the bacterial GroEL to PrP c 23-231 and rPrP27-30 in vitro.
• the prokaryotic homologue of the Hsp60 family is also capable of binding to PrP c - recombinant GroEL in corresponding in vitro binding experiments was employed.
• Pull-down assays were performed by equilibrating glutathione-Sepharose 4B beads (Pharmacia) loaded with GST or the GST fusion protein in refolding buffer (RF) (32) including 0.5 % Triton-X-100.
• RF refolding buffer
• the equilibrated beads were incubated with an up to 10 fold molar excess of GroEL or Hsp60 (monomer) at room temperature in the presence of RF including 0.5 % Triton-X-100. After centrifugation (2500 rpm, 10 min) the beads were washed with RF and analyzed on a 12.5 % SDS Phastgel, blotted and probed for the presence of GroEL or Hsp60.
• FLAG tagged Hsp60 has been synthesized as a 61 kDA protein in the baculovirus system (Fig. 4, lane 1 ).
• Co-expression of GST::rPrP c (rPrP23-231 ) (lane 3) and GST::rPrP27-30 (rPr90-231 ) (lane 4) downregulates FLAG::Hsp60 expression, whereas co-expression of GST does not affect expression of FLAG::Hsp60 (lane 2).
• Hsp60 in the presence of PrP c can occur either on transcription or translational level.
• PrP could trigger proteolytic degradation of Hsp ⁇ O.
• PrP c could lead to an increased secretion process of Hsp ⁇ O.
• the presence of Hsp60 in the culture medium would prove this hypothesis.
• Downregulation of Hsp60 in the presence of PrP can account for a direct PrP/Hsp60 interaction which leads to an increased downregulation of Hsp ⁇ O.
• Application of PrP-peptides spanning parts of the prion protein can identify the region of the prion protein which is responsible for the downregulation of Hsp ⁇ O expression.
• PrP PrP-associated form of PrP is made from a cell surface precursor that is both protease- and phospholipase-sensitive. J. Biol. Chem. 266 (1991 ), 18217-18223.
• NFI/CTF1 Transcriptional activation of NFI/CTF1 depends on a sequence motif strongly related to the carboxyterminal domain of RNA polymerase II. Nucl. Acids Res. 22 (1994), 2601-2603.

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