JP2008280266A - Monoclonal antibody - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new monoclonal antibody against human-originated endothelin receptor type A. <P>SOLUTION: This monoclonal antibody against the human-originated endothelin receptor type A reacts with an extracellular loop of the human-originated endothelin receptor type A, and does not react with any of the N-terminal domain, C-terminal domain and intracellular loop of the human-originated endothelin receptor type A. The constitution that the extracellular loop domain is an extracellular second loop, the constitution inhibiting the binding of the endothelin receptor with a natural ligand and the constitution capable of inhibiting a natural ligand-specific signal transmission of the endothelin receptor are recommended. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a monoclonal antibody, and more particularly to a novel monoclonal antibody against human-derived endothelin receptor type A.

  Membrane receptor proteins on the cell surface play an extremely important role in transmitting extracellular information into the cell. Therefore, a substance that binds to a membrane receptor protein becomes a candidate substance as an agonist-type drug or an antagonist-type drug. Among membrane receptor proteins, the G protein-coupled receptor (GPCR) is particularly focused on drug development because about half of currently marketed small molecule drugs target this receptor. Collecting. In addition, about half of the GPCRs are orphan GPCRs whose natural ligands functioning in vivo have not been identified, and natural ligands and related compounds are expected as candidates for new drugs. Ligand screening for GPCRs is extremely intense.

  The GPCR penetrates the cell membrane seven times, and exists with its N-terminus facing out of the cell and its C-terminus facing into the cell. That is, the extracellular domain of GPCR is composed of an N-terminal domain, an extracellular first loop, an extracellular second loop, and an extracellular third loop. Similarly, the intracellular domain of GPCR is composed of an intracellular first loop, an intracellular second loop, an intracellular third loop, and a C-terminal domain.

  Endothelin (ET) is a peptide consisting of 21 amino acid residues and is known to have a strong vasoconstrictive action. Endothelin has been found in three isoforms, ET-1, ET-2 and ET-3. On the other hand, a receptor that specifically binds to endothelin is an endothelin receptor. Two types of endothelin receptors, endothelin receptor type A (ETAR) and endothelin receptor type B (ETBR), have been found, ETAR shows strong binding to ET-1 and ET-2, ETBR is It shows the same degree of connectivity with three types of ET.

  The endothelin receptor is a kind of GPCR and has a structure that penetrates the cell membrane seven times. The primary structure of human-derived endothelin receptor type A (hereinafter sometimes abbreviated as “hETAR”) has already been elucidated, and its N-terminal domain, each extracellular domain, each intracellular domain, and the C-terminal A site corresponding to the domain has also been identified.

  Endothelin receptor antagonists can be therapeutic agents for various diseases involving endothelin, and new antagonists are actively being searched for (for example, Patent Documents 1 and 2). For example, the antagonist is expected to have an action of suppressing vasoconstriction and may be a therapeutic agent for cardiomyopathy. On the other hand, it has been generally attempted to apply an antibody against a receptor as an antagonist (antagonist antibody), and an antibody against an endothelin receptor may be a therapeutic agent for cardiomyopathy or the like. Currently, polyclonal antibodies have already been obtained as antibodies against human-derived endothelin receptor type A, and some of them are commercially available. On the other hand, monoclonal antibodies that specifically recognize only the primary structure of hETAR have been obtained (Non-patent Document 1). However, neither a polyclonal antibody nor a monoclonal antibody has been obtained that specifically recognizes the extracellular loop of hETAR. Therefore, an antibody capable of inhibiting the binding and signal transduction between hETAR and natural ligands (ET-1, ET-2) has not been obtained.

JP 2001-64262 A JP 2004-43495 A Biochemical and Biophysical Research Communications, 1992, Vol. 187, No. 3, p. 1241-1248

  An object of the present invention is to provide a novel monoclonal antibody against human-derived endothelin receptor type A that is useful for new drug development and the like.

  The present inventors use a fusion gene of a gene encoding chaperonin, a kind of molecular chaperone, and a gene encoding human-derived endothelin receptor type A to immunize mice with human-derived endothelin receptor type. An immune response against A was induced. Then, spleen cells of the mouse and myeloma were fused to prepare a hybridoma population, and a hybridoma producing a monoclonal antibody that specifically recognizes the extracellular loop of hETAR was searched. As a result, one type of clone was successfully selected. And it succeeded in acquiring a desired monoclonal antibody from the said hybridoma, and completed this invention. The gist of the present invention is as follows.

  The invention according to claim 1 is a monoclonal antibody against human-derived endothelin receptor type A, which reacts with the extracellular loop of human-derived endothelin receptor type A, and has an N-terminal domain of human-derived endothelin receptor type A, It is a monoclonal antibody that does not react to either the C-terminal domain or the intracellular loop.

  The monoclonal antibody against human-derived endothelin receptor type A of the present invention (hereinafter sometimes abbreviated as “anti-hETAR monoclonal antibody”) specifically reacts with the extracellular loop of human-derived endothelin receptor type A. And does not react to any of the N-terminal domain, C-terminal domain, or intracellular loop. The monoclonal antibody of the present invention is useful for developing therapeutic agents for diseases related to the extracellular loop of human-derived endothelin receptor type A. The monoclonal antibody of the present invention is also useful for diagnosis of diseases related to the extracellular loop of endothelin receptor type A and construction of immunoassay for endothelin receptor type A.

  The invention according to claim 2 is the monoclonal antibody according to claim 1, which recognizes the three-dimensional structure of the extracellular loop.

  The monoclonal antibody of the present invention recognizes the three-dimensional structure of the extracellular loop. In other words, it does not recognize only the primary structure of the extracellular loop. Such a configuration provides a monoclonal antibody particularly suitable as an antagonist antibody for hETAR. The extracellular loop that retains the three-dimensional structure corresponds to a natural hETAR (active hETAR) extracellular loop, and exists on the surface of a living cell, for example.

  It is recommended that the extracellular loop domain is an extracellular second loop (Claim 3).

A configuration derived from a mouse (Claim 4) and a configuration having the following properties (Claim 5) are recommended.
(A) Subclass: IgG2a
(B) Light chain: kappa chain (c) Reacts with human-derived endothelin receptor type A and does not substantially react with either mouse-derived endothelin receptor type A or rat-derived endothelin receptor type A.

  Invention of Claim 6 is a monoclonal antibody of any one of Claims 1-5 which can inhibit the coupling | bonding of an endothelin receptor and a natural ligand.

  The invention according to claim 7 is the monoclonal antibody according to any one of claims 1 to 6 capable of inhibiting natural ligand-specific signal transduction possessed by the endothelin receptor.

  Such a configuration provides a monoclonal antibody that can be used as an antagonist to human-derived endothelin receptor type A.

  The monoclonal antibody of the present invention is useful for developing therapeutic agents for diseases related to the extracellular loop of human-derived endothelin receptor type A. It is also useful for diagnosing diseases related to the extracellular loop of endothelin receptor type A and constructing an immunoassay for endothelin receptor type A.

  Hereinafter, the best mode for carrying out the present invention will be described.

First, the structure of human-derived endothelin receptor type A (hETAR) will be described.
As described above, hETAR is a kind of G protein-coupled receptor (GPCR), which exists seven times through the cell membrane, with its N-terminal outside and the C-terminal facing inside. The gene (cDNA) encoding hETAR has already been isolated, and the amino acid sequence of hETAR is also known. SEQ ID NO: 3 shows the base sequence of the hETAR gene and the amino acid sequence corresponding to the base sequence, and SEQ ID NO: 4 shows only the amino acid sequence.

  According to the structure generally considered by the hydrophobic model of hETAR, each domain of hETAR corresponds to the following portion in the amino acid sequence shown in SEQ ID NO: 4. The left side is the amino acid number, and the right side is each domain. When the amino acid sequences of the extracellular domains (N-terminal domain, extracellular first loop, extracellular second loop, and extracellular third loop) are compared between different animals, the homology of the N-terminal domain is low, and each loop The homology of is known to be high.

1 to 24: membrane translocation signal peptide sequence (cleaved and removed after expression)
25 to 80: N-terminal domain 101 to 119: intracellular first loop 141 to 161: extracellular first loop 180 to 205: intracellular second loop 225 to 256: extracellular second loop 275 to 310: intracellular first loop 3 loops 332-348: extracellular third loop 372-427: C-terminal domain

  The monoclonal antibody of the present invention is a monoclonal antibody against human-derived endothelin receptor type A, which reacts with the extracellular loop of human-derived endothelin receptor type A, and has an N-terminal domain and a C-terminal of human-derived endothelin receptor type A. It does not react to either domain or intracellular loop. As a method for producing the monoclonal antibody of the present invention, a known method can be employed as it is, and for example, it can be produced based on the cell fusion method of Kohler and Milstein. Briefly, hybridoma populations are prepared by fusing spleen cells of animals such as mice in which an immune response to hETAR has been induced and myeloma, and those producing a desired monoclonal antibody are selected from the hybridoma population. Then, the selected hybridoma can be cultured, and a desired monoclonal antibody can be isolated and purified from the culture.

  As a method for inducing an immune response against hETAR, a general protein immunization technique in which an animal is inoculated with hETAR (protein) may be used, but a genetic immunization technique in which an hETAR gene is administered to an animal is preferably used.

  That is, since hETAR is a membrane protein, it is generally difficult to use full-length hETAR as an immunogen. Therefore, when it is desired to induce an immune response against the extracellular loop of hETAR with protein immunity, the peptide of the extracellular loop is used as the immunogen. However, since the extracellular loop has high homology among different organisms, even when the peptide is used as an immunogen, a sufficient immune response may not be induced. After all, it is difficult to sufficiently induce an immune response against the extracellular loop by protein immunization.

  On the other hand, according to gene immunization, by using a gene encoding the full length of hETAR, a situation similar to that in which full length hETAR is used as an immunogen can be created. Furthermore, since the expressed hETAR can exist in a native state (active state) in the animal body, it is possible to induce an immune response specific to the three-dimensional structure of hETAR. In addition, according to the gene immunization technique, it can be performed if only the hETAR gene is available, and it is not necessary to prepare purified hETAR.

  However, even in this case, since the homology of the N-terminal domain is low among different animals in hETAR, an immune response against the N-terminal domain may be mainly induced. Conventionally, only antibodies that recognize the N-terminal domain have been obtained for antibodies against hETAR, which is considered to be one of the causes. Therefore, more preferably, a fusion gene of a gene encoding chaperonin and a gene encoding hETAR is used as a gene inoculated into an animal. By using the fusion gene as an immunogen, an immune response against the extracellular loop can be induced more selectively than when the hETAR gene is used alone. Details of the gene immunization method using the fusion gene are described in International Publication No. 2006/041157.

  Chaperonins are a type of molecular chaperone and are present in all living organisms such as bacteria, archaea, and eukaryotes. In particular, it is abundant in bacterial cytoplasm, eukaryotic mitochondria, and chloroplasts. Chaperonin has an activity of promoting protein folding and an activity of preventing protein denaturation. Chaperonin is a large cylinder-like complex protein with a total molecular weight of about 800,000 to 1,000,000, in which two ring-shaped structures composed of 7 to 9 chaperonin subunits (also referred to as HSP60) having a molecular weight of about 60,000 overlap. . Chaperonin has a cavity inside the ring-shaped structure, and temporarily folds the protein in the middle of folding or denatured protein to form a complex. And it is known that the protein accommodated in the cavity is correctly folded, and then the correctly folded protein is released from the cavity.

  Chaperonins are classified into group I type found in bacteria and eukaryotic organelles and group II type found in eukaryotes and archaea. In the gene immunization performed when the monoclonal antibody of the present invention is produced, when using the above-mentioned fusion gene, any group I type or group II type chaperonin gene may be employed. A representative example of group I chaperonins is GroEL derived from E. coli. A representative example of group II type chaperonins is TCP derived from archaea. The base sequence of the gene encoding the GroEL subunit is shown in SEQ ID NO: 8.

  Here, in the “gene encoding chaperonin (chaperonin gene)”, in addition to the gene encoding chaperonin subunit (chaperonin subunit gene), a “chaperonin subunit linked body” in which a plurality of chaperonin subunits are connected in tandem. Including the gene encoding. The gene encoding the chaperonin subunit conjugate is the same as a gene in which a plurality of chaperonin subunit genes are linked in tandem. Note that the chaperonin subunit linked body can form a ring-shaped structure similar to natural chaperonin.

  As a method for producing the fusion gene, for example, the hETAR gene and the chaperonin gene may be linked by a ligation reaction. In addition, when administering the fusion gene to an animal, it is preferable to administer the fusion gene in an expression vector and under the control of a promoter. Examples of expression vectors include pCI, pSI, pAdVantage, pTriEX, pKA1, pCDM8, and pS. Examples of the promoter on the expression vector include CMV promoter, AML promoter, SV40 promoter, SRα promoter, EF-1α promoter and the like. Furthermore, an enhancer that enhances promoter activity may be included in the expression vector. Furthermore, the expression vector may contain a CpG motif.

  Examples of the method for administering the fusion gene to animals include subcutaneous injection, intramuscular injection, intravenous injection and the like. Administration by particle gun is also applicable. The dose may be appropriately determined according to the expression vector used, the type of promoter, etc., but is generally 1 to 3 mg / kg body weight per time, which is 25 to 100 μg / time for mice. The number of administrations may be one, but a higher immune response can be induced by performing multiple administrations at regular intervals.

  In addition, when an immune response is induced in an animal by protein immunization, a generally performed method can be employed as it is. For example, purified hETAR is prepared and a mixed solution with an adjuvant is prepared. This mixed solution is injected subcutaneously into a mouse or the like to induce an immune response against hETAR. If necessary, it may be administered multiple times at intervals, and boosted.

  The animal to be immunized is not particularly limited, but preferably a mouse is used. Thereby, a mouse-derived monoclonal antibody can be obtained.

  Hybridoma can be produced by the method of Kohler and Milstein. That is, the spleen is extracted from an animal that has been genetically or protein immunized by the above-described procedure and induced an immune response against hETAR, and spleen cells are collected. Then, the spleen cells and myeloma are fused to produce a hybridoma population. Selection of a hybridoma can be performed using, for example, a HAT selection medium. In addition, the hybridoma can be cloned by, for example, a limiting dilution method. Thus, a hybridoma that produces an anti-hETAR monoclonal antibody that reacts with the extracellular loop of hETAR and does not react with any of the N-terminal domain, C-terminal domain, and intracellular loop of hETAR may be selected and cloned.

  Then, by culturing the selected and cloned hybridoma, an anti-hETAR monoclonal antibody having the above-mentioned properties can be produced. Hybridoma culture may be performed in the peritoneal cavity of an animal or in vitro using a dish or the like. When culturing a hybridoma in the abdominal cavity of an animal, ascites can be collected and a monoclonal antibody can be isolated and purified from the ascites. When culturing in vitro, monoclonal antibodies can be isolated and purified from the culture solution.

  The purification of the monoclonal antibody can be performed by combining various known techniques such as chromatography, salting out, dialysis, and membrane separation. When the subclass of the monoclonal antibody is IgG, it can be simply purified by affinity chromatography using protein A.

  The monoclonal antibody of the present invention can be used for various applications. For example, it can be applied to drug development as an antagonist to hETAR. That is, hETAR inhibits natural ligand-specific signal transduction to suppress vasoconstriction and can be applied to cardiomyopathy treatment and hypertension treatment. Moreover, if the structure of the complementarity determining region (CDR) of the monoclonal antibody of the present invention is specified and chimerized or humanized, it can be made a safer drug. In addition, the monoclonal antibody of the present invention includes a low molecular weight drug screening reagent, a cardiomyopathy / hypertension test reagent, a research reagent for ETAR localization verification using tissue sections / cells, a test reagent for preparing recombinant ETAR-expressing cells, It can also be used for research reagents for crystal structure analysis of ETAR.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(1) Isolation of human-derived endothelin receptor type A gene PCR was performed using a human lung cDNA library (Takara Bio Inc.) as a template and oligonucleotides having the nucleotide sequences shown in SEQ ID NOS: 1 and 2 as primer pairs. A DNA fragment containing the human-derived endothelin receptor type A (hETAR) gene having the base sequence shown in No. 3 (hereinafter referred to as “DNA fragment A”) was amplified. In DNA fragment A, an NheI site was introduced at the 5 ′ end and a SalI site was introduced at the 3 ′ end from the primer. Similarly, PCR was performed using oligonucleotides having the nucleotide sequences shown in SEQ ID NOS: 1 and 5 as primer pairs, and a DNA fragment containing the hETAR gene having the nucleotide sequence shown in SEQ ID NO: 3 (hereinafter referred to as “DNA fragment B”). Amplified). In DNA fragment B, a sequence encoding NheI site at the 5 ′ end and a SalI site encoding two stop codons (TAATAG) at the 3 ′ end were introduced into the DNA fragment B.

(2) Isolation of GroEL subunit gene Genomic DNA was extracted and purified from Escherichia coli HMS174 (DE3) strain (Novagen). Next, PCR was performed using the purified genomic DNA as a template and oligonucleotides having the nucleotide sequences shown in SEQ ID NOs: 6 and 7 as primer pairs, and a DNA fragment containing the GroEL subunit gene having the nucleotide sequence shown in SEQ ID NO: 8 ( Hereinafter, it is referred to as “DNA fragment C”). In DNA fragment C, a sequence encoding a SalI site at the 5 ′ end and two stop codons (TAATAG) at the 3 ′ end and a NotI site were introduced from the primer.

(3) Construction of a vector for gene immunization expressing a fusion protein of human endothelin receptor type A and GroEL subunit A mammalian expression vector pCI Mammalian Expression Vector (Promega) is digested with restriction enzymes NheI and SalI to produce bacteria. After dephosphorylating the end with derived alkaline phosphatase (BAP), the DNA fragment A prepared in (1) above was inserted. Furthermore, this expression vector was digested with SalI and NotI, and the end was dephosphorylated with BAP, and then the DNA fragment C prepared in (2) above was inserted to construct the vector pCI-hETAR · GroEL. That is, the vector pCI-hETAR · GroEL has a fusion gene of a gene encoding hETAR and a gene encoding GroEL subunit. On the other hand, similarly, after digesting the mammalian expression vector pCI Mammalian Expression Vector with restriction enzymes NheI and SalI, and dephosphorylating the end with BAP, the DNA fragment B prepared in (1) above was inserted, Vector pCI-hETAR was constructed. That is, the vector pCI-hETAR has only the hETAR gene.

(4) Preparation of human-derived endothelin receptor type A stable expression cells and human-derived endothelin receptor type B stable expression cells Using pCI-hETAR · GroEL constructed in (3) as a template, the nucleotide sequences shown in SEQ ID NOs: 1 and 5 PCR was performed using an oligonucleotide having a primer pair to obtain a DNA fragment containing the hETAR gene. This DNA fragment was introduced into the NheI-XhoI site of pCIneo (Promega) to construct pCIneo-hETAR. On the other hand, PCR was performed using a human placenta cDNA library (Takara Bio Inc.) as a template and oligonucleotides having the nucleotide sequences shown in SEQ ID NOs: 9 and 10 as primer pairs, and a human-derived endothelin receptor type B (hETBR) gene (sequence) A DNA fragment containing No. 11) was obtained. This DNA fragment was introduced into the NheI-XhoI site of pCIneo to construct pCIneo-hETBR.

37.5 μL of Lipofectamin solution, 625 μL of OPTI-MEMI medium, and 625 μL of OPTI-MEMI medium containing 20 μg of pCIneo-hETAR were mixed. Using this mixed solution, pCIneo-hETAR was introduced into 2 × 10 ⁵ CHO-K1 cells (Dainippon Pharmaceutical Co., Ltd.). In a similar procedure, pCIneo-hETBR was introduced into CHO-K1 cells. As a control, only pCIneo1 was introduced into CHO-K1 cells. Each CHO-K1 cell into which the gene was introduced was cultured in Ham's F12K + 10% FBS medium (ICN) for 30 hours. Further, each cell was detached, suspended, seeded with 5 × 10 ⁵ cells in a 100 mm dish, and treated with Ham's F12K + 10% FBS medium containing antibiotic G418 (Promega) at a concentration of 0.8 mg / mL for 2 weeks. Was done. After drug treatment, antibiotic resistant cells were cloned by limiting dilution. Each cloned CHO-K1 cell was further cultured overnight using a 96-well microtiter plate at an initial cell concentration of 2 × 10 ⁴ cells / 100 μL. When the cells were stimulated with ET-1 (Peptide Institute) within the concentration range of 10 ⁻⁶ to 10 ⁻¹² M after the completion of the culture, the intracellular Ca ²⁺ concentration increased temporarily. The Ca ²⁺ concentration was measured using a Ca ²⁺ signal analyzer (FLIPR; Molecular Devices) and an intracellular Ca ²⁺ staining kit (Ca3kit; Molecular Devices). From this, it was found that both active hETAR and active hETBR were normally stably expressed on the CHO-K1 cell membrane.

(5) Gene immunization The vector pCI-hETAR · GroEL was dissolved in physiological saline to a concentration of 250 μg / mL to prepare a composition for immunization. This immunizing composition was immunized by injecting 0.12 mL each into both thigh muscles of 8-week-old mouse BALB / c (female) (day 0). Thereby, 30 μg each of pCI-hETAR · GroEL was administered to both legs, ie, 60 μg per animal. Thereafter, immunization was repeated repeatedly on the 7th, 21st, and 28th days. Then, blood was collected on days 0, 7, 14, 21, 28, 35, and 42 to prepare serum. As a control, mice were immunized with the vector pCI-hETAR, which expresses hETAR alone.

(6) Evaluation of antibody binding in serum to active hETAR by flow cytometry CHO-K1 cells (hereinafter referred to as “hETAR gene-introduced cells”) into which pCIneo-hETAR has been introduced and stable expression has been confirmed, pCIneo-hETBR CHO-K1 cells (hereinafter referred to as “hETBR gene-introduced cells”) that were introduced and confirmed to have stable expression, and CHO-K1 cells (control cells) into which pCIneo had been introduced were washed with PBS. Serum on day 35 after immunization was diluted 500-fold and incubated with each cell. Further, each cell was washed with PBS, phycoerythrin-labeled anti-mouse IgG antibody (Beckman Coulter) was added as a secondary antibody, and each cell and serum were then used using a flow cytometer FACSCalibur (Becton Dickinson). The interaction with anti-hETAR antibody was analyzed.

As a result, when hETAR gene-introduced cells were used, phycoerythrin was hardly detected in the serum before gene immunization, but was detected in the serum after gene immunization. This indicated that anti-hETAR antibodies in the serum after immunization bind to hETAR gene-introduced cells. On the other hand, when hETBR gene-introduced cells were used, phycoerythrin was not detected in the serum after gene immunization. This indicated that anti-hETAR antibody in the serum after immunization did not bind to the hETBR gene-introduced cells. Even when control cells were used, phycoerythrin was not detected in the serum after gene immunization. This indicated that anti-hETAR antibodies in the post-immune serum did not bind to control cells.
From the above, gene immunization with the vector pCI-hETAR · GroEL was able to induce the production of antibodies that specifically recognize the extracellular domain of active hETAR in mouse serum.

(7) Preparation of anti-hETAR monoclonal antibody Booster immunization was performed on 6 mice genetically immunized by the same procedure as in (5) above. Three days after the booster, the spleen was removed and spleen cells were prepared. By the PEG method, 1 × 10 ⁸ spleen cells and 1 × 10 ⁷ BALB / C mouse-derived HAT-selective myeloma SP2 / 0 cells were fused (cell fusion). A population of fused cells (hybridoma) was suspended in RPMI medium and seeded in each well of 14 96-well microplates. At this stage, about 990 hybridomas were obtained.

  The medium in the microplate was replaced with RPMI medium supplemented with HAT Media Supplement (50 ×) (Sigma, product number: H0262) at a frequency of once every 3 days for 2 weeks from the day after cell fusion.

  Antibody binding was evaluated by the same flow cytometry as in (6) above, and the binding between hETAR gene-introduced cells and antibodies in the hybridoma culture supernatant in each well was examined. As a result, binding to the antibody was confirmed in the 4 holes.

  Four types of hybridomas that were confirmed to be bound to antibodies were cloned by limiting dilution. That is, four types of hybridomas were seeded in a 96-well microplate so that there were 1 cell / hole or less and cultured. Two weeks later, the same flow cytometry was performed, and the binding of the antibody (anti-hETAR monoclonal antibody) in the cloned culture supernatant was confirmed. As a result, four hybridomas producing anti-hETAR monoclonal antibodies were cloned.

  Each hybridoma was cultured in 100 mL of RPMI medium for 2 weeks. Each culture supernatant was subjected to a protein G column (Amersham Bioscience) and purified and concentrated to obtain about 2 mg of each of the four types of purified anti-hETAR monoclonal antibodies.

  Each anti-hETAR monoclonal antibody was tested as follows. From these results, one type of anti-hETAR monoclonal antibody having the desired properties was selected (clone number hA21). In the following, the test procedure and results are shown in order, with the anti-hETAR monoclonal antibody of clone number hA21 (hereinafter sometimes simply abbreviated as “hA21”) as a representative.

(8) Evaluation of binding to hETAR by flow cytometry A PBS solution of hA21 having a concentration of 10 μg / mL (hereinafter referred to as “hA21 solution”) was prepared. On the other hand, hETAR gene-introduced cells, hETBR gene-introduced cells, and control cells were washed with PBS, respectively, and hA21 solution was incubated with each cell. Furthermore, each cell was washed with PBS, and after adding phycoerythrin-labeled anti-mouse IgG antibody (Beckman Coulter) as a secondary antibody, each cell, hA21, and a flow cytometer FACScalibur (Becton Dickinson) were used. The interaction of was analyzed. The results are shown in FIGS. FIG. 1 is a histogram showing the analysis results of the interaction between hETAR gene-introduced cells and hA21. FIG. 2 is a histogram showing the analysis results of the interaction between hETBR gene-introduced cells and hA21. FIG. 3 is a histogram showing the analysis results of the interaction between the control cells and hA21. 1-3, the vertical axis represents the number of cells, and the horizontal axis represents the fluorescence intensity derived from phycoerythrin (PE). Moreover, the cell which belongs to M2 (right area | region) among two areas (M1, M2) represents the cell couple | bonded with hA21.

  As a result, when hETAR gene-introduced cells were used, many cells were detected in the M2 area (FIG. 1). This indicated that hA21 binds to hETAR transgenic cells. On the other hand, when hETBR gene-introduced cells were used (FIG. 2) and control cells were used (FIG. 3), almost no cells were detected in the M2 area. This indicated that hA21 did not bind to either hETBR gene-introduced cells or control cells. From the above, it was shown that hA21 specifically recognizes the extracellular domain of active hETAR.

(9) Evaluation of binding to hETAR by immunological cell staining hETAR gene-introduced cells and hETAR gene-introduced cells were seeded in a 6-well plate with a cover glass and cultured. After confirming that the cells adhered and proliferated, the cover glass was immersed in a 4% paraformaldehyde / PBS solution to immobilize the cells, and subjected to cell membrane permeabilization with saponin. Thereafter, the cover glass was incubated with the hA21 solution. Further, the cover glass was washed with PBS, phycoerythrin-labeled anti-mouse IgG antibody (Beckman Coulter, Inc.) was added as a secondary antibody, and then observed using a fluorescence microscope (Olympus). The interaction was analyzed. The results are shown in FIGS. 4 (a) and 4 (b) and FIGS. 5 (a) and 5 (b). FIG. 4 is a photograph showing the results of observation of hETAR gene-introduced cells incubated with the hA21 solution with a fluorescence microscope, (a) is a differential interference image, and (b) is a fluorescence microscope image. FIG. 5 is a photograph showing the result of observation of hETBR gene-introduced cells incubated with the hA21 solution with a fluorescence microscope, where (a) is a differential interference image and (b) is a fluorescence microscope image. 4 and 5, the location where fluorescence is detected is the location where hA21 is bound on the cell. The scale bar shown in FIGS. 4 and 5 indicates 100 μm.

  As shown in FIG. 4B, when hETAR gene-introduced cells expressed on the cell membrane were used, fluorescence was detected and hA21 was bound on the cell membrane. On the other hand, when hETBR gene-introduced cells were used, no fluorescence was detected and hA21 was not bound on the cell membrane. From the above, it was shown by immunological cell staining that hA21 specifically binds to hETAR (extracellular domain) expressed on cells.

(10) Epitope analysis Three amino acid residues were shifted in the following four frames of the amino acid sequence shown in SEQ ID NO: 4 to produce a total of 60 peptides consisting of 15 amino acid residues.
Amino acid numbers 25 to 96 of SEQ ID NO: 4 (frames including the N-terminal domain): peptide numbers 1 to 20
-Amino acid numbers 128 to 175 of SEQ ID NO: 4 (frame including extracellular first loop): Peptide numbers 25 to 36
Amino acid numbers 210 to 272 of SEQ ID NO: 4 (frame including the extracellular second loop): Peptide numbers 37 to 53
-Amino acid numbers 312 to 356 of SEQ ID NO: 4 (frame including the extracellular third loop): Peptide numbers 61 to 71

  Each prepared peptide was immobilized on a glass array. The glass array was incubated with hA21 solution after blocking with rat serum. Furthermore, Cy5-labeled anti-mouse IgG rat antibody (Jackson ImmunoResearch) was added as a secondary antibody, and then the interaction between each peptide and hA21 was analyzed using a fluorescent slide scanner Genepix 4200A (Axson Instruments). The results are shown in FIG. In FIG. 6, the vertical axis represents the fluorescence intensity, and the horizontal axis represents the number of each peptide. As shown in FIG. 6, hA21 bound strongly only to peptides 42 and 43 corresponding to a part of the extracellular second loop (circled portion in FIG. 6). The 42nd peptide corresponds to the amino acid number 225 (Val) to 239 (Cys) of SEQ ID NO: 4, the 43rd peptide corresponds to the amino acid number 228 (Pro) to 242 (Asn), both of which are the extracellular second loop. (Amino acid numbers 225 to 256) constitute a part of it. From the above, it was found that hA21 specifically recognizes the extracellular second loop of hETAR.

(11) Evaluation of intracellular Ca ²⁺ signal transduction inhibitory activity hETAR gene-introduced cells were cultured overnight at an initial cell concentration of 2 × 10 ⁴ cells / 100 μL using a 96-well microtiter plate. After completion of the culture, hA21 within a concentration range of 10 ⁻⁶ to 10 ⁻¹² M was added to each well. As a control, mouse IgG (Pierce, negative control) or peptide antagonist BQ123 (TOCRIS, positive control) was similarly added in a concentration range of 10 ⁻⁶ to 10 ⁻¹² M. One hour later, the degree of antibody concentration-dependent decrease in the transient increase in intracellular Ca ²⁺ concentration when each cell was stimulated with 1 × 10 ⁻⁸ M endothelin ET-1 (Peptide Institute) was measured. The Ca ²⁺ concentration was measured using a Ca ²⁺ signal analyzer (FLIPR; Molecular Devices) and an intracellular Ca staining kit (Ca3kit; Molecular Devices). The results are shown in FIG. FIG. 7 is a graph showing the relationship between the intracellular Ca ²⁺ concentration and the concentration of each additive. As shown in FIG. 7, when hA21 was added, a decrease in intracellular Ca ²⁺ concentration was observed, as was the case with BQ123. This indicated that hA21 competitively inhibited the binding between endothelin ET-1 and hETAR, resulting in inhibition of signal transduction into the cell. The 50% inhibitory concentration (IC50) was calculated to be 1.708 × 10 ⁻⁷ M for hA21 and 2.807 × 10 ⁻⁸ M for BQ123.
From the above, it was shown that hA21 can inhibit natural ligand-specific signal transduction possessed by hETAR.

(12) Isotype analysis The isotype of hA21 was determined using a mouse monoclonal antibody isotyping kit (GE Healthcare). Detection was performed by sandwich ELISA using horseradish peroxidase-labeled mouse IgG antibody. The results are shown in FIG. FIG. 8A is a photograph showing the result of the control, and FIG. 8B is a photograph showing the result of hA21. As shown in FIG. 8 (b), the hA21 subclass was IgG2a, and the light chain was κ chain (see arrow).

(13) Evaluation of binding to heterologous ETAR “mETAR gene-introduced cells” and “rETAR gene-introduced cells” were prepared in the same manner as in the above (1) to (6). Using these cells, the binding of hA21 to mETAR and rETAR was evaluated by flow cytometry similar to (8) above. The results are shown in FIG. FIG. 9A is a histogram showing the analysis result of the interaction between the mETAR gene-introduced cell and hA21, and FIG. 9B is a histogram showing the analysis result of the interaction between the rETAR gene-introduced cell and hA21. That is, in any case, almost no cells were detected in the M2 area. This indicated that hA21 did not bind to either mETAR gene-transferred cells or rETAR gene-transferred cells. When rETAR gene-introduced cells were used (FIG. 9 (b)), the number of cells detected in the M2 area was greater than when mETAR gene-introduced cells were used (FIG. 9 (a)). It was a level that can be called uncoupled. From the above, it was shown that hA21 reacts specifically with hETAR, but does not substantially react with either mETAR or rETAR.

It is a histogram showing the analysis result of interaction with a hETAR gene transfer cell and hA21. It is a histogram showing the analysis result of interaction between hETBR gene introduction cell and hA21. It is a histogram showing the analysis result of interaction with a control cell and hA21. It is the photograph showing the result of having observed the hETAR gene transfer cell incubated with hA21 solution with the fluorescence microscope, (a) is a differential interference image, (b) is a fluorescence microscope image. It is the photograph showing the result of having observed the hETBR gene transfer cell incubated with hA21 solution with the fluorescence microscope, (a) is a differential interference image, (b) is a fluorescence microscope image. It is a graph showing the result of an epitope analysis. It is a graph showing the relationship between intracellular Ca ^<2+ > density ^| concentration and the density ^| concentration of each additive. It is the photograph showing the result of an isotype analysis, (a) shows the result of a control, (b) shows the result of hA21. (A) is a histogram showing the analysis result of the interaction between the mETAR gene-introduced cell and hA21, and (b) is a histogram showing the analysis result of the interaction between the rETAR gene-introduced cell and hA21.

Claims (7)

  A monoclonal antibody against human-derived endothelin receptor type A, which reacts with the extracellular loop of human-derived endothelin receptor type A, and has N-terminal domain, C-terminal domain, and intracellular loop of human-derived endothelin receptor type A. Monoclonal antibody that does not react to either.   The monoclonal antibody according to claim 1, which recognizes the three-dimensional structure of the extracellular loop.   The monoclonal antibody according to claim 1 or 2, wherein the extracellular loop domain is an extracellular second loop.   The monoclonal antibody according to any one of claims 1 to 3, which is derived from a mouse. The monoclonal antibody according to claim 4, which has the following properties.
(A) Subclass: IgG2a
(B) Light chain: kappa chain (c) Reacts with human-derived endothelin receptor type A and does not substantially react with either mouse-derived endothelin receptor type A or rat-derived endothelin receptor type A.   The monoclonal antibody according to any one of claims 1 to 5, which can inhibit the binding between an endothelin receptor and a natural ligand.   The monoclonal antibody according to any one of claims 1 to 6, which can inhibit signal transduction specific to a natural ligand of an endothelin receptor.