Intracellular Ions And Water Flows Are Required For Acrosomal Swelling And Exocytosis In Human Sperm

MATA MARTINEZ ESPERANZA; ARIAS RODOLFO; POBLETE SANTIAGO; DE BLAS, GERARDO ANDRÉS

San Luis

Congreso; XXXVII Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2019

Sociedad de Biología de Cuyo

The acrosome reaction (AR) is the exocytosis of the acrosome, asecretory vesicle located in the apical area of the sperm head. During exocytosis, it has been observed that, in order to achieve secretion, the acrosome must undergo morphological changes, including increased volume (acrosomal swelling). In other cell types, the increase in volume of secretory vesicles is crucial to carry out exocytosis, with ions and water flows being required. We assume that molecular machinery similar to the one responsible for swelling of other secretory vesicles is involved in AR. Consequently, we proposed that chloride, potassium and water channels are present in human sperm acrosome and are required for its swelling and AR. To test this we used capacitated and permeabilized human sperm as a strategy to study if intracellular ion channels were involved. First, we incubated the sperm with general or specific inhibitors of chloride, potassium or water channels and, then, the ARwas induced with 10μM of free calcium. The results obtained support our hypothesis and also suggest the participation of intracellular aquaporins (7 and 8), the chloride transporters (ClC-2 and ClC-3), and the auxillary subunit of voltage-dependent channels Kvβ1 during AR. 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 thus perform exocytosis in human sperm.