Transglutaminase activity in bovine calf testicular membranes: evidence for a possible role in the interaction of follicle-stimulating hormone with its receptor.
Transglutaminase (TGase) activity, determined by incorporation of [1,4-14C]putrescine into casein, was demonstrated in a light membrane fraction derived from bovine calf testicular homogenates. In common with other TGases thus far identified, testicular TGase is calcium dependent. A concentration-dependent relationship was observed between decreasing TGase activity and increasing concentrations of N-ethylmaleimide and bacitracin, inhibitors of TGase, and the TGase substrate monodansylcadaverine. Although NEM at all concentrations tested had no effect on [125I]human (h) FSH-receptor binding, dissociation of [125I]hFSH from its receptor was enhanced when [125I]hFSH-receptor complexes were formed in the presence of NEM. Dissociation of [125I]hFSH from its receptor also increased in the presence of bacitracin or monodansylcadaverine. Reduced TGase activity always paralleled increases in hormone-receptor dissociation. The inverse relationship between TGase activity and [125I]hFSH-receptor dissociation observed in this study suggests that TGase activity may be involved in the interaction of FSH with its receptor and that protein cross-linking (via peptide bond formation) may be a mechanism whereby some FSH-receptor complexes are stabilized in the bovine testis.
D000818:Animals; D001414:Bacitracin / Q000494:pharmacology; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D005033:Ethylmaleimide / Q000494:pharmacology; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D008297:Male; D011700:Putrescine / Q000378:metabolism; D011962:Receptors, FSH / Q000187:drug effects / Q000378:metabolism*; D013737:Testis / Q000187:drug effects / Q000201:enzymology*; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002364:Caseins; D011962:Receptors, FSH; D001414:Bacitracin; D005640:Follicle Stimulating Hormone; D011503:Transglutaminases; C008542:monodansylcadaverine; D002103:Cadaverine; D005033:Ethylmaleimide; D002118:Calcium; D011700:Putrescine