Phosphorylation of LIMK1 and COFILIN is regulated by PAK4 and okadaic acid-sensitive protein phosphatases during mouse sperm capacitation.

LUQUE GM; BALESTRINI PA; KRAPF D; SCHIAVI-EHRENHAUS LJ; STIVAL C; JABLOÑSKI M; BUFFONE MG; ROMAROWSKI A; UGO B; GILIO N

Mar del Plata

Congreso; Reunión Conjunta de la Sociedad Argentina de Investigación Clínica (SAIC), la Sociedad Argentina de Inmunología (SAI) y la Sociedad Argentina de Fisiología (SAFIS).; 2018

Actin dynamics play a central role in controlling the process of of exocytosis in somatic cells as well as in sperm from several mammalian species. In spermatozoa, acrosomal exocytosis, a special type of controlled secretion, is an absolute requisite for fertilization in mammals. This complex exocytic process is controlled by several players including the actin cytoskeleton. We previously have shown the involvement of small GTPases of the Rho family in the signaling pathway that leads to actin polymerization during sperm capacitation. We have also demonstrated the participation of LIMK1 and COFILIN, both downstream effectors of small GTPases that are modulated by phosphorylation. In the present work, we studied the role of phosphatases and PAK kinases in the regulation of LIMK1/ COFILIN phosphorylation during mouse sperm capacitation. One of the widely known phosphatases of COFILIN in somatic cells.Slingshot homolog 1 (SSH1), was observed to be expressed in mouse sperm and localized in the acrosome and the principal piece of the flagellum, as well as its characteristic regulator protein, 14-3-3. The time course of SSH1 dephosphorylation is coincident with that observed for COFILIN dephosphorylation. Furthermore, okadaic acid-sensitive protein phosphatases were found to dephosphorylate SSH1 and their inhibition resulted in persistent levels of phosphorylated COFILIN. However, flow cytometry analysis revealed that okadaic acid did not significantly affect the percentage of sperm that undergo acrosomal exocytosis. On the other hand, inhibition of PAK4 kinase by a specific inhibitor (PF-3758309) resulted in lower levels of pLIMK1 and a significant decrease in the percentage of sperm that undergo acrosomal exocytosis (p