Jeyakumar, M and Krishnamurthy, HN and Dighe, RR and Moudgal, NR (1997) Demonstration of complimentarity between monoclonal antibodies (MAbs)to human chorionic gonadotropin (hCG) and polyclonal antibodies to luteinizing hormone hCG receptor (LH-R) and their use in better understanding hormone-receptor interaction. In: Receptors & Signal Transduction, 7 (4). pp. 299-310.
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We have earlier reported that polyclonal antisera raised in rabbits to a luteinizing hormone/chorionic gonadotropin receptor (LH-R) purified from sheep luteal tissue has antibodies exhibiting hormone agonistic and antagonistic activities. Western blot analysis showed this antibody (LHR-anti IgG) to be highly specific to sheep luteal LH receptor (LH-R) (Jeyakumar and Moudgal, 1991). Using this, along with a battery of mouse monoclonal antibodies (MAbs) to hCG, an attempt has been made to better understand the interaction of LH/hCG with its receptor. Of the eight hCG MAbs screened, three (B-14/B-7, B-52/18 and A(7)/G(4)) were specific to the beta-subunit; while a second set of three (G(10)/F-7, H-9/E-9 and B-52/21) were specific to the alpha-subunit. Two additional MAbs (B-52/28 and F-9/G(8)) did not recognize individual subunits, but bound like the rest intact hCG. Both I-125 hCG and I-125 anti LHR-IgG bound specifically to ovine luteal membrane LH-R. Assuming that a certain degree of similarity should exist between hCG and LHR-anti IgG, different hCG MAbs were tested for their ability to block the binding of either I-125 hCG or I-125 LHR-anti IgG to sheep luteal LH-R. It appears that hCG and LH-R share a minimum of four sites that are complementary to each other and these are recognized by the hCG MAbs B-14/B-7, G(10)/F-7, A(7)/G(4), and H-9/E-9. Whereas two of the MAbs B-14/B-7 and G(10)/F-7 blocked the binding of both I-125 labeled hCG and LHR-anti IgG to the receptor, MAbs A(7)/G(4) and H-9/E-9 only inhibited the binding of I-125 LHR-anti IgG to the LH-R. Although individually B-14/B-7 and G(10)/F-7 blocked the binding of I-125 LHR-anti IgG to LH-R to a maximum extent of 43%, together they inhibited binding by as much as 80%. The ability of B-14/B-7 to inhibit binding of I-125 LHR-anti IgG to the receptor was also significantly increased by the addition of A(7)/G(4). Finally, by demonstrating direct binding of the immobilized hCG MAbs B-14/B-7, G(10)/F-7, A(7)/G(4), and H-9/E-9 to LHR-anti IgG, we have been able to establish that the receptor binding sites of hCG and LHR-anti IgG are complementary and that a set of four sites are recognizable by the hCG MAbs. From the degree of interaction, it appears that two sites recognized by MAbs B-14/B-7 and G(10)/F-7 (representing a site each in the beta- and alpha-subunit of hCG) have a prominent role in the interaction of hCG with its receptor. Thus, this study has provided us with an opportunity to investigate the interaction of LH/hCG with its receptor by an indirect approach of monitoring the binding of their respective antibodies with each other.
| Item Type: | Journal Article |
|---|---|
| Publication: | Receptors & Signal Transduction |
| Publisher: | Humana Press Inc |
| Additional Information: | Copyright of this article belongs to Receptors & Signal Transduction. |
| Keywords: | LH receptor;polyclonal antibodies to LH-R;hCG monoclonal antibodies;anti-idiotypic antibodies. |
| Department/Centre: | Division of Biological Sciences > Molecular Reproduction, Development & Genetics Division of Biological Sciences > Biochemistry |
| Date Deposited: | 30 May 2009 17:39 |
| Last Modified: | 27 Feb 2010 12:01 |
| URI: | http://eprints.iisc.ac.in/id/eprint/18795 |
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