PIP5KI Gamma and Arf6 are required during acrosomal exocytosis in human spermatozoa.

PELLETAN, LEONARDO E; GINER, FEDERICO; VITALE, NICOLAS; MAYORGA, LUIS S; BELMONTE, SILVIA A

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. SAIB; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. SAIB

PIP5KIGAMMA AND ARF6 ARE REQUIRED DURING ACROSOMAL EXOCYTOSIS IN HUMAN SPERMATOZOA Pelletán LE, Giner F, Vitale N*, Mayorga LS and Belmonte SA. 1Biol Cel y Mol, IHEM-CONICET, FCM-UNCuyo, Mendoza, Argentina. 2INSERM-CNRS-U Strasbourg, France.During fertilization, the spermatozoon must penetrate the zona pellucida to reach the oolema. Only sperm that have completed the acrosome reaction (AR) can successfully accomplish this task. The AR is a calcium-regulated exocytosis where the membrane of the single secretory vesicle, the acrosome, fuses to the plasma membrane. We have recently demonstrated that the small GTPase Arf6 is not only present in sperm cells but when activated induces AR in the complete absence of calcium. On the other hand, we demonstrated by TLC that active Arf6 increases spermatozoa’s phosphatidylinositol 4,5-bisphosphate (PIP2) synthesis. It has been described in other cell types that Arf6 regulates the activity of phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) that catalyzes the conversion of phosphatidylinositol 4-phosphate (PI4P) in PIP2. So, we moved on to analyze PI4P5K function in sperm cells. By Western blot and IFI we demonstrated that PI4P5K is present in human sperm cells. We observed that Arf6 directly activate a recombinant PI4P5K by using purified proteins in the presence of PI4P and 32PgammaATP. The recombinant active kinase did not affect calcium-induced acrosomal exocytosis in functional assays but the antibody against the PI4P5K inhibited calcium-triggered AR suggesting that this enzyme is required for exocytosis.