Effects of modulators of protein kinase C on human sperm capacitation

Abstract

To examine the effects of stimulators or inhibitors of protein kinase C on capacitation and protein phosphorylation in human sperm. Capacitated sperm treated with or without modulators of protein kinase C were monitored by the chlortetracycline fluorescence assay. Capacitation was confirmed by the ability of sperm to undergo the acrosomal reaction in response to mouse zonae pellucidae. 32P-labeled sperm phosphoproteins were analyzed by one-dimensional gel electrophoresis to detect the effect of protein kinase C stimulator, 12-O-tetradecanoyl-phorbol-13-acetate, on protein phosphorylation. The treatment of sperm with protein kinase C stimulators resulted in the following: [1] the rapid appearance of the clear perimeter pattern, featuring distribution of fluorescence over the entire head exhibiting a bright perimeter and bright midpiece; [2] an accelerated ability to undergo the acrosomal reaction; and [3] an enhanced phosphorylation of 57.5-kd sperm phosphoprotein. Furthermore, these stimulatory effects were inhibited by protein kinase C inhibitors. Protein phosphorylation mediated by protein kinase C may be involved in the regulation of human sperm capacitation.