Morphological and molecular mechanisms involved in the acrosome swelling in human sperm

SOSA CM; ZANETTI, MN; DE BLAS, G; MAYORGA, LS

Congreso; 48º SAIB; 2012

SAIB

The acrosome reaction is an exocytic event essential for fertilization. It requires the attachment of the outer acrosomal membrane to the plasma membrane, the opening of fusion pores, and the releasing the acrosomal contents together with hybrid vesicles. In a previous report we have proposed that the swelling of the acrosome and the deformation of the outer acrosomal membrane is required for the process. By means of transmission electron microscopy, in this communication we provide evidence for this requirement: we show that all stimulators of the acrosome reaction stimulate swelling and that swelling precedes the deformation of the outer acrosomal membrane and the appearance of intraacrosomal vesicles. According to observations in other models, the contact between the outer acrosomal membrane and the plasma membrane is part of the mechanism of store operated calcium channels opening. However, by using specific inhibitors we show that swelling is downstream the opening of these channels. Our results indicate that acrosomal swelling is an essential part of acrosmal exocytosis and that it is triggered by the influx of calcium through store operated calcium channels in the plasma membrane.