Role of Intracellular Ionic and Water Flows During Acrosome Reaction in Human Sperm

POBLETE SANTIAGO; MATA MARTINEZ ESPERANZA; ZANETTI NATALIA; ARIAS RODOLFO J; MAYORGA LUIS S; DE BLAS GERARDO A

Congreso; Reunión Conjunta SAIB-SAMIGE; 2020

SAIB-SAMIGE

The acrosome reaction (AR) is essential for the fertilization of the oocyte and consists of the exocytosis of the secretory granule (acrosome) located in the apical area of the sperm head. During the exocytic event it has been observed that to achieve secretion, the acrosome must undergo morphological changes, including an increase in volume or acrosomal swelling (AS). The swelling of secretory vesicles has been reported as crucial for different types of exocytosis. It is known that ions and water fluxes are essential for swelling. We assumed that the molecular machinery responsible for swelling should be similar for AS. Consequently, we hypothesized that chloride, potassium, and water channels present in the acrosome of human sperm should be required for AS and exocytosis. To test this, we used capacitated and permeabilized human sperm as a strategy to study whether intracellular ion channels are involved. First, we incubated the sperm with inhibitors of chloride, potassium, or water channels and, then, the AR was induced with 10μM of free calcium. The results obtained not only support our hypothesis, but also suggest the participation of intracellular AQP-7, AQP-8, ClC-2, ClC-3, and Kvβ1 during exocytosis and a direct requirement of ClC-3 and AQP-7 for AS. Furthermore, we identified the presence of all these proteins in the human sperm by Western Blot assays, as well as the subcellular localization in the acrosomal region of AQP-7 and Kvβ1 by immunofluorescence assays. In summary, our results indicate that intracellular water, chloride, and potassium flows are required to complete acrosomal swelling and exocytosis in human sperm.