LYSINE ACETYLATION AS A MODULATOR OF SPERM CAPACITATION

CAROLINA BARO GRAF; CINTIA V STIVAL; DARIO KRAPF; CARLA RITAGLIATI; MARIANO G BUFFONE

Holderness, New Hampshire

Congreso; Gordon Research Conference in Fertilization & Activation of Development; 2017

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 (hiperactivation) and with their ability to undergo the acrosome reaction. At the molecular level, capacitation correlates with: activation of cAMP-PKA pathway, increase in intracellular pH and Ca2+ concentration, hyperpolarization of the plasma membrane potential, loss of cholesterol and other lipid modifications and increase in protein tyrosine phosphorylation. How these signaling pathways interact to induce hiperactivation and the acrosome reaction is not well understood. The mature sperm is transcriptionally and translationally silent. To obtain full functionality, spermatozoa 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 differentiation, maturation and fertilization, has been well established. Acetylation as a broad and abundant PTM comparable with phosphorylation, however, has not been well analyzed. Recently, two groups identified 576 and 456 acetylated proteins in capacitated and non capacitated human sperm respectively, 250 were present in both conditions. In the present work, we studied the role of acetylation in capacitation of mouse. WB analysis with anti-acetyl lysine antibodies showed lysine acetylation of lots of proteins spanning a wide mass range. The kinetic of acetylation during capacitation didn´t show any clear tendency, probably while some proteins are acetylated others are deacetylated. In order to determine the importance of acetylation in the molecular events associated with capacitation, we used two deacetylases inhibitors (iDACs), TSA and NAM, and studied their effect in the phosphorylation of PKA substrates and pY, in the membrane potential, in the intracellular Ca2+ concentration and in their ability to undergo the acrosome reaction when induced with Progesterone. Remarkably, sperm incubated in the presence of iDACs in non capacitating conditions exhibit phosphorylation patterns, membrane potential and acrosome reaction percentages comparable to those of control capacitated sperm.