Polyphosphoinositide-derived diacylglycerol stimulates the hydrolysis of phosphatidylcholine by phospholipase C during exocytosis of the ram sperm acrosome. Effect is not mediated by protein kinase C.

摘要: In ram spermatozoa, treatment with the ionophore A23187 and Ca2+ led to an increase in total diacylglycerol mass exocytosis of acrosomal granule. If sperm cells were prelabeled [3H]palmitic acid, stimulation A23187/Ca2+ resulted generation [3H]diacylglycerols a mixture saturated unsaturated fatty acids. When 1-O-[3H]octadecylglycerophosphocholine, [3H]alkylacylglycerol. No rise [3H]diacyl- or [3H]alkylacylphosphatidic acid was detected under these conditions. Moreover, no changes phosphatidic have been previously noted similar Thus, results indicate that diradylglycerols are generated via phospholipase C (PLC). Increases paralleled by rises monoacyl- monoalkylglycerols labeled at position 1, but not free [3H]octadecanol, implying that, unlike somatic cells, spermatozoa catabolize 2-diglyceride lipase. Activation PLC appears be effected phosphoinositide-derived diacylglycerol: exposure Mg2+, cation known inhibit phosphoinositide hydrolysis, less activity upon stimulation, addition exogenous 1,2-diacylglycerols enhanced enzyme's activity. However, 1,3-diacylglycerol alkylacylglycerol also stimulated activity, suggesting effect is unlikely mediated protein kinase C. Since essential molecular sequence leading membrane fusion mammalian suggest their constitutes fundamental event during response physiological agonists.