Actin polymerization and development of hyperactivated (HA) motility are two processes that take place during sperm capacitation.Actin polymerization occurs during capacitation and prior to the acrosome reaction,fast F-actin breakdown takes place.The increase in F-actin during capacitation depends upon inactivation of the actin severing protein,gelsolin,by its binding to phosphatydilinositol-4,5-bisphosphate (PIP2) and its phosphorylation on tyrosine-438 by Src.