Balestrini Paula A, Sanchez-Cardenas Claudia, Luque Guillermina M, Baro Graf Carolina, Sierra Jessica M, Hernández-Cruz Arturo, Visconti Pablo E, Krapf Dario, Darszon Alberto, Buffone Mariano G
Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, México.
FASEB J. 2021 Jun;35(6):e21478. doi: 10.1096/fj.202002333RR.
Sperm capacitation is essential to gain fertilizing capacity. During this process, a series of biochemical and physiological modifications occur that allow sperm to undergo acrosomal exocytosis (AE). At the molecular level, hyperpolarization of the sperm membrane potential (Em) takes place during capacitation. This study shows that human sperm incubated under conditions that do not support capacitation (NC) can become ready for an agonist stimulated AE by pharmacologically inducing Em hyperpolarization with Valinomycin or Amiloride. To investigate how Em hyperpolarization promotes human sperm's ability to undergo AE, live single-cell imaging experiments were performed to simultaneously monitor changes in [Ca ] and the occurrence of AE. Em hyperpolarization turned [Ca ] dynamics in NC sperm from spontaneously oscillating into a sustained slow [Ca ] increase. The addition of progesterone (P4) or K to Valinomycin-treated sperm promoted that a significant number of cells displayed a transitory rise in [Ca ] which then underwent AE. Altogether, our results demonstrate that Em hyperpolarization is necessary and sufficient to prepare human sperm for the AE. Furthermore, this Em change decreased Ca oscillations that block the occurrence of AE, providing strong experimental evidence of the molecular mechanism that drives the acquisition of acrosomal responsiveness.
精子获能对于获得受精能力至关重要。在此过程中，会发生一系列生化和生理修饰，使精子能够发生顶体胞吐作用（AE）。在分子水平上，精子膜电位（Em）在获能过程中发生超极化。本研究表明，在不支持获能（NC）的条件下孵育的人类精子，可通过用缬氨霉素或氨氯吡咪药理学诱导Em超极化，从而为激动剂刺激的AE做好准备。为了研究Em超极化如何促进人类精子发生AE的能力，进行了实时单细胞成像实验，以同时监测[Ca]的变化和AE的发生。Em超极化使NC精子中的[Ca]动力学从自发振荡转变为持续缓慢的[Ca]升高。向经缬氨霉素处理的精子中添加孕酮（P4）或K，促使大量细胞的[Ca]出现短暂升高，随后发生AE。总之，我们的结果表明，Em超极化对于使人类精子为AE做好准备是必要且充分的。此外，这种Em变化减少了阻碍AE发生的Ca振荡，为驱动顶体反应性获得的分子机制提供了有力的实验证据。
