PEPTIDE AND IMMUNOCHEMICAL MAPPING OF THE ECTODOMAIN OF THE PORCINE LH RECEPTOR

The LH/hCG receptor is a G protein-coupled receptor with an N-terminal extracellular domain involved in hormone-receptor interaction. The re combinant porcine receptor, stably expressed in Chinese hamster ovary (CHO) cells, has the same characteristics (K-d, and cAMP production) a s in Leydig cells. Six synthetic peptides derived from the receptor ec todomain and two polyclonal antipeptide sera were tested in the homolo gous system porcine LH and porcine LH receptor. Their ability to inhib it hormone binding and signal transduction on CHO cells expressing the recombinant receptor was evaluated. Peptides 25-40 and 107-121 exhibi ted a high transduction inhibition as compared with hormone binding, p eptides 21-36, 102-111, and 102-121 inhibited hormone binding more eff iciently than signal transduction, and peptide 7-24 exhibited inhibiti on of both hormone binding and hormone-induced cAMP production, Immuno globulins against peptides 21-36 and 102-111 inhibited both hormone an d receptor activation suggesting that these sequences are located on t he receptor surface. The data suggest that multiple, discontinuous reg ions of the extracellular domain of porcine LH receptor are involved i n hormone binding and signal transduction. Two minimum critical sequen ces, 21-24 and 102-107, are involved in hormone binding and vicinal se gments may be implicated in signal transduction.