Role of hyperpolarization on human sperm acrosomal exocytosis.

BUFFONE MG; ROMAROWSKI A; EHRENHAUS LJ; BALESTRINI PA; PUGA MOLINA LC; KRAPF D; LUQUE GM

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Sperm capacitation in the female tract is essential to gain fertilization ability. During this processes sperm undergo a series of physiological modifications that lead to two main events: acquisition of hyperactivated motility and the ability to undergo acrosomal reaction (AR). It has been reported either pharmacologically or genetically (potassium channel Slo3 Knockout mice) that hyperpolarization of the plasma membrane (Em) is necessary and sufficient for sperm acrosomal responsiveness. This change in Em is driven by the cAMP/PKA signaling pathway associated to capacitation. Both, PKA and Slo3 are located in the flagellum and little is known about how this change is transduced to the head where AR takes place and how this plays out in human sperm. In this work we aimed to study the role of cAMP/PKA pathway on Em and its impact on acrosomal responsiveness in human sperm.Human sperm was incubated with CFTR, NBC, Ouabain and PKA inhibitors, with or without valinomycin to induce hyperpolarization and A23187 to induce AR. Changes in Em were assessed by using Disc(3)5 and flow cytometry. To assess the acrosomal status, human sperm were stained with Pisum sativum and observed under an epifluorescence microscope. In the present work we found that, similar to what occurs in mice, activation of the cAMP/PKA pathway is essential for AR responsiveness and that changes in this pathway are involved in the Em. We also found that in conditions where hyperpolarization does not occur inhibitors of (CFTR, NBC or sodium-potassium ATPase), sperm cannot undergo AR in response to Calcium ionophore. By inducing hyperpolarization using valinomycin, we have observed that sperm can undergo AR even in conditions that do not support capacitation. All together, these results suggest a pivotal role of cAMP/PKA in Em changes in human sperm and that Em is essential to prepare sperm to undergo AR.