FUNCTIONAL EXPRESSION OF RECOMBINANT HUMAN LUTEINIZING HUMAN CHORIOGONADOTROPIN RECEPTOR

The functional capacity of the recombinant human LH/hCG receptor was t ested on the basis of gonadotropin stimulation of cAMP production by s table transfections of Chinese hamster ovary (CHO) cells. A CHO cell l ine expressed with the hLH/hCG receptor cDNA covering the entire amino acid coding region revealed the presence of LH/hCG binding site (Kd:1 .45x10(-10)M) on the plasma membrane. Treatment of transfected cells(C HO-LH/hCGR) with hCG induced dose-dependent increases in intracellular cAMP production, indicating that the expressed human LH/hCG receptor functionally couples with endogenous adenylyl cyclase. Although hCG in duced dose-dependent increases in cAMP production. rat and bovine LH a nd human FSH did not alter cAMP levels compared to control values. Nor thern blot analysis with a cRNA probe derived from human LH/hCG recept or cDNA indicated the presence of three LH/hCG receptor mRNA transcrip ts(5.4, 3.6 and 2.4 kilobases) in RNA prepared from human ovary. Prein cubation of CHO-LH/hCGR cells with hCG for 16h decreased the subsequen t cAMP production caused by a 30min results indicate that desensitizat ion to hCG stimulation occurs in CHO-LH/hCGR cells. Therefore, this ce ll line provides a tool with which to pursue detailed studies on the m olecular basis of LH/hCG induced desensitization. (C) 1994 Academic Pr ess, Inc.