LYSINE ACETYLATION AS A MODULATOR OF SPERM CAPACITATION

BARO GRAF, CAROLINA; KRAPF, DARIO; RITAGLIATI, CARLA; LUQUE, GUILLERMINA M.; STIVAL, CINTIA; BUFFONE, MARIANO G.

Mar del Plata

Congreso; LRXIII Reunión Anual de la Sociedad Argentina de Investigación Clínica; 2018

Mammalian sperm are unable to fertilize the egg before undergoing a series of biochemical and physiological changes in the female reproductive tract, collectively known as capacitation. Functionally, capacitation is associated with changes in the sperm motility (hyperactivation) and with their ability to undergo the acrosome reaction. At the molecular level, capacitation correlates with activation of the cAMP-PKA pathway, increase in intracellular pH and Ca2+ concentration, hyperpolarization of the plasma membrane potential, lipid modifications and increase in protein tyrosine phosphorylation. How these signaling pathways interact to induce hyperactivation and acrosomal responsiveness is not well understood. Since mature sperm are transcriptionally and translationally silent, they rely on postranslational modifications (PTM) more than any other cell type. Therefore, it is an exceptional model for the study of signaling pathways based on PTM. The importance of phosphorylation, an essential PTM in sperm physiology has been well established. Acetylation as a broad and abundant PTM comparable with phosphorylation, however, has not been well analyzed. In this context, the general aim of our work was to study the role of protein acetylation in the signaling cascade responsible for the acquisition of fertilizing capacity of mammalian sperm. WB and immuno-localization analyses with anti-acetyl lysine antibodies showed acetylation of several proteins, with a significant increase detected in capacitated sperm. Therefore, we used deacetylase inhibitors to produce pharmacological hyperacetylation under non-capacitating conditions and evaluated the molecular and functional events associated to capacitation. In this condition, we observed increased PKA activity and [Ca2+]i, CatSper opening and hyperpolarization, all capacitation-associated molecular events. Furthermore, hyperacetylation of non-capacitated sperm promotes hyperactivation and prepares the sperm to undergo acrosome reaction, even in the absence of HCO3- and BSA. Together, these results show that acetylation plays a critical role in acquisition of the fertilization competence of mammalian sperm