CHARACTERIZATION OF THE SIGNALING PATHWAY OF THE ACROSOME REACTION IN HUMAN SPERM.

SOLÍS A; SÁNCHEZ-TUSIE AA; CHURCHILL G; DE BLAS GA; DARSZON A; TREVIÑO CL

Okinawa

Simposio; 11th International Symposium on Spermatology.; 2010

Although the Acrosome Reaction (AR) is a fundamental exocytic event for fertilization, the signaling pathway involved in this process is not completely understood. The physiological induction of the AR triggers a biphasic Ca2+ influx; however, the molecular entities involved in this process are not clearly defined. A model of the AR signaling pathway involving the Exchange Protein directly Activated by cAMP (Epac) has been proposed. We speculate that Epac might stimulate the enzyme (CD38) that catalyzes the production of nicotinic acid adenine dinucleotide phosphate (NAADP), which in turn activates intracellular Two Pore Channels (TPCs), releasing a small amount of Ca2+ that would convey the signal to other channels (IP3R and RyR) releasing more Ca2+ from internal stores and amplifying the response, the depletion of intracellular pools of calcium will cause the activation of Store Operated channels (SOC). In the present work we employ the EPAC specific cAMP analogue (8-pCPT-2’-O-Me-cAMP) to trigger the Ca2+ rise in the presence or absence of specific channel inhibitors to confirm or rule out the participation of these components in the proposed signaling pathway. We measured intracellular Ca2+ changes in sperm loaded with a fluorescent Ca2+ indicator. Our preliminary results suggest that SOC, TPC and IP3R are implicated in the signaling pathway trigger by Epac.