Ezrin Protein Network In Human Sperm Function Studies Can Process

Before fertilization,sperm must fulfill some preparative events that render the spermatozoa competent for fertilization,which collectively known as capacitation.Capacitation is a necessary process before sperm fertilize an oocyte in vivo.All mammalian sperm must undergo this process.During sperm capacitation,modifications of membrane characteristics represent a key step in the process,however,the molecular basis of these events is not fully understood.Ezrin is the best studied member of the ERM family.As a cross-linker between the cortical cytoskeleton and plasma membrane proteins,it contributes mainly on the remodeling of membrane surface structure,so as to mediate a series of cell events including cell-cell and cell-substrate adhesion,cytomorphosis,formation of the microvilli,and so on.Furthermore,activated ezrin and the Rho dissociation inhibitor, RhoGDI,promote the formation of cortical cytoskeleton-polymerized actin via Rho activation.Thus,ezrin,actin,RhoGDI,Rho and plasma membrane proteins form a complicated network in vivo,which contribute to the assembly of the membrane surface structure.Previous studies in our laboratory have shown that ezrin and RhoGDI1 are expressed in human testis.We are thus interested in whether the ezrin-RhoGDI1-actin-membrane protein network is involved during human sperm capacitation.Our results indicated that ezrin was activated by phosphorylation on the 567 threonine residue during human sperm capacitation.Co-immunoprecipitation studies suggested that interaction between ezrin and RhoGDI1 increased and RhoGDI1 was phosphorylated,suggesting that RhoGDI1 dissociated from RhoA,which led to actin polymerization during capacitation.We speculate that activated ezrin then interacts with polymerized actin and glycosylated membrane protein cd44 after capacitation.Blocking sperm capacitation with ezrin or actin monoclonal antibodies decreased the acrosome reaction rate,but incubation with antibodies had no effect on acrosome reaction alone.Taken together,our study demonstrates that a network consisting of ezrin,RhoGDI1,RhoA,F-actin and membrane proteins functions to influence the sperm membrane modification during human sperm capacitation.