The Signaling module cAMP/epac/Rap1/PLCε/IP3 mobilizes acrosomal calcium during sperm exocytosis

Publication date: Available online 17 December 2015 Source:Biochimica et Biophysica Acta (BBA) - Molecular Cell Research Author(s): Ornella Lucchesi, María C. Ruete, Matías A. Bustos, María F. Quevedo, Claudia N. Tomes Exocytosis of the sperm's single secretory granule, or acrosome, is a regulated exocytosis triggered by components of the egg's investments. In addition to external calcium, sperm exocytosis (termed the acrosome reaction) requires cAMP synthesized endogenously and calcium mobilized from the acrosome through IP3-sensitive channels. The relevant cAMP target is Epac. In the first part of this paper, we present a novel tool (the TAT-cAMP sponge) to investigate cAMP-related signaling pathways in response to progesterone as acrosome reaction trigger. The TAT-cAMP sponge consists of the cAMP binding sites of protein kinase A regulatory subunit RIβ fused to the protein transduction domain of the human immunodeficiency virus-1 TAT. The sponge permeated into sperm, sequestered endogenous cAMP, and blocked exocytosis. Progesterone increased the population of sperm with Rap1-GTP, Rab3-GTP and Rab27-GTP in the acrosomal region; pretreatment with the TAT-cAMP sponge prevented the activation of all three GTPases. In the second part of this manuscript, we show that phospholipase Cε (PLCε) is required for the acrosome reaction downstream of Rap1 and upstream of intra-acrosomal calcium mobilization. Last, we present direct evidence that cAMP, Epac, Rap1 and P...
Source: Biochimica et Biophysica Acta (BBA) Molecular Cell Research - Category: Molecular Biology Source Type: research