Identification of Müllerian Inhibiting Substance Specific Binding in Human Cell Lines

Summary

The receptor for Müllerian Inhibiting Substance (MIS), a gonadal glycoprotein hormone, has not been previously identified. Plasma membranes from MlS-sensitive human tumor cell lines (HTB-111, endometrial carcinoma; and A-431, vulvar squamous carcinoma) were detergent extracted and incubated with ¹²⁵I-labeled MIS anti-idiorypic antibody, or radioiodinated human recombinant MIS (¹²⁵I rhMIS), with and without unlabeled competitors. ¹²⁵I anti-idiotypic MIS antibody bound to HTB-111 membrane extracts was displaceable by unlabeled anti-idiotypic antibody, but not by anti-isotypic antibody prior to cross-linking. Specific binding of the anti-idiotypic MIS antibody to endometrial carcinoma cells was verified using fluorescence activated cell analysis and fluoresceinated antibody. Furthermore, unlabeled anti-idiotypic MIS antibody competed for ¹²⁵I rhMIS binding to A-431 vulvar carcinoma membranes. The labeled anti-idiotypic MIS antibody binding complex could be separated from ³²P labeled EGF receptor in the A-431 membranes, indicating that EGF, a natural inhibitor of MIS activity, and MIS itself bind to different receptors. These studies demonstrate a specific, displaceable binder for MIS in the plasmalemmae of two human tumor lines. Purification of this cell surface receptor protein will be greatly aided by using the MIS anti-idiotypic antibody.

Müllerian Inhibiting Substance - Receptor - Anti-idiotypic Antibody - Binder