CLONING OF A RECEPTOR FOR PROSTAGLANDIN-F2-ALPHA FROM THE OVINE CORPUS-LUTEUM

A complementary DNA clone encoding a functional receptor for prostagla ndin F-2 alpha (PGF(2 alpha)) has been isolated from an ovine large lu teal cell complementary DNA library (prepared from day 10 midluteal ph ase RNA). This receptor, which has been designated FP, consists of 362 amino acids (M(r) = 40,982) and is a member of the family of G protei n-coupled receptors. Radioligand binding studies with membranes prepar ed from transfected COS cells demonstrated specific 17-[H-3]phenyl-tri nor-PGF(2 alpha) binding that was displaced by prostanoids in the orde r of 17-phenyl-trinor-PGF(2 alpha) > PGF(2 alpha) > fluprostenol > PGD (2) > PGE(2) >> 8-epi PGF(2 alpha). Xenopus laevis oocytes injected wi th RNA encoding the ovine FP receptor responded to 17-phenyl-trinor-PG F(2 alpha) with increased membrane chloride conductance in calcium-fre e medium. Northern blot analysis with RNA from day corpus luteum showe d a major band of similar to 6.1 kilobases. On day 14, when luteolysis usually starts, the abundance of this 6.1-kilobase band was variable between individual ewes, and on day 16, when luteolysis is underway, t he message was uniformly less abundant. This variability appeared to c orrelate with circulating progesterone. Thus, when the progesterone le vel was high (days 10 and 14 depending on whether luteolysis had start ed), the amount of FP receptor message was high, whereas when the prog esterone level was low or falling (day 16), the amount of FP receptor message decreased. We have cloned an ovine FP receptor whose expressio n confers appropriate functional activity in COS cells and Xenopus ooc ytes. Furthermore, the level of messenger RNA encoding the FP receptor is high in the midluteal phase ovine corpus luteum and decreases duri ng luteolysis.