Role and regulation of PI3K in sperm capacitation and the acrosome reaction

Mammalian spermatozoa undergo several signaling and biochemical transformations in the female genital tract, collectively called capacitation. The capacitated spermatozoon binds to the egg zona pellucida, where it undergoes the acrosome reaction (AR), a process enabling it to penetrate and fertilize the egg. Actin polymerization occurs in sperm capacitation and depolymerization prior to the AR. In this review we describe the possible role and regulation of PI3K in sperm capacitation and the acrosome reaction. We claim that PI3K is activated by protein kinase A and suppressed by protein kinase C. Only partial activation of PI3K is seen during the capacitation time, however towards the end of incubation, full activation is observed. Actin polymerization during capacitation is independent on PI3K activity, suggesting that the enzyme is not involved in sperm capacitation. However, the full activation of PI3K towards the end of the capacitation suggests that it might mediate the AR, as indeed was found.