Phospholipase C-mediated release of low molecular weight follicle-stimulating hormone receptor-binding inhibitor from testis membranes.
Low molecular weight inhibitors (FRBI) of FSH binding to receptor have been isolated from a variety of gonadal tissue extracts. Because of similarities noted in the composition of FRBI and that expected for polypeptides anchored to plasma membrane via a glycosyl-phosphatidylinositol linkage, we used bacterial phospholipase C to determine if FRBI could be released from calf testis membranes. FRBI was measured by use of radioligand-receptor assays and by a direct chemical method involving derivatization with dansyl chloride followed by HPLC. Phospholipase C treatment released FRBI from calf testis membranes in a time-dependent fashion. Phospholipase C-mediated release was blocked by O-phenanthroline, a specific inhibitor of phosphoinositol-phospholipase C (PI-PLC) activity. These data suggest that FRBI is anchored to testicular plasma membranes via a phospholipase C cleavable glycosyl-phosphatidylinositol anchor. The quantity of PI-PLC releasable FRBI in the testis and its FSH receptor-binding inhibitory potency suggest the possibility that endogenous regulation of FRBI release from testicular membranes could result in local attenuation of FSH action at the receptor level.
Sluss
P M
PM
Department of Urology, University of Rochester Medical Center, New York 14642.
Ewing
J F
JF
Schneyer
A L
AL
D000818:Animals; D002417:Cattle; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors; D006020:Glycopeptides / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008970:Molecular Weight; D011962:Receptors, FSH / Q000378:metabolism*; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000494:pharmacology*
D006020:Glycopeptides; D011962:Receptors, FSH; D005640:Follicle Stimulating Hormone; D010738:Type C Phospholipases