Rol of ESCRT complex in the acrosomal exocitosis in human sperm.

POCOGNONI CA, MAYORGA LS, BELMONTE SA.

Mendoza

Congreso; 28° Reunión Científica Anual Sociedad de Biología de Cuyo.; 2010

Sociedad de Biología de Cuyo.

During acrosomal exocytosis in human sperm, cup-shaped invaginations are formed in the outer acrosomal membrane leading to the formation of intraacrosomal vesicles. These vesicles have a topology equivalent to the internal vesicles of multivesicular bodies. The ESCRT (endosomal sorting complex required for transport) pathway is required for terminal membrane fission events in several important biological processes, including multivesicular body biogenesis, HIV budding and cytokinesis. VPS4 is an ATPase of the AAA family with a key function in this pathway. Our aim was to evaluate the role of VPS4 proteins in acrosomal exocytosis. For this purpose, dominant negative mutants of VPS4 A and B, and the wild type proteins with His6 tags where produced in E. coli. Permeabilized human sperm were incubated with 100-300 nM of each purified protein and then the acrosome reaction was triggered with Ca2+. Exocytosis was assessed by FITC-Pisum sativum lectin binding. The results indicate that the VPS4 negative mutants significantly inhibit the acrosomal exocytosis (ED50 in the 100 nM range) whereas the wild type proteins did not affect exocytosis. These preliminary results suggest that acrosomal exocytosis requires the ESCRT-mediated deformation of the outer acrosomal membrane.