Signal transduction mechanisms regulating ion fluxes in the sea urchin sperm

Abstract

Ion permeability changes involving ion channels and transporters are essential for fertilization, since they are key elements in sperm-egg signaling and environmental sensing. Changes modulated by external factors and components from the outer layer of the homologous egg, like the sperm-activating peptides and the fucose-sulfate glycoconjugate, trigger complex signaling systems in the sperm that modulate how sperm swim, find the egg and fertilize it. These signaling systems depend on plasma membrane ion permeability and involve an alteration of second messenger levels, changes of membrane potential and intracellular Ca2+, Na+ and pH, along with changes in sperm morphology in the case of the acrosome reaction (AR). New procedures to elucidate the signaling pathways implicated in sperm ion transport have expanded the opportunities to dissect sperm-egg signaling revealing how sperm ion channels participate in activation, motility, chemotaxis, and the AR. The sperm signaling pathways involve a large variety of ion channels and transporters, which are discretely localized and finely orchestrated to play specific roles that define the elaborate performance of sperm and allow a successful fertilization. In this review we will focus on the signaling molecules involved in the final aim of the sperm, to reach and fertilize the egg.