Novel Mechanisms of Motility Induction in the Sperm of a Teleost Fish

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This project focuses on the initiation of sperm motility in the Pacific herring (Clupea pallasi). The overall goal is to define the series of extracellular and intracellular events that lead to the initiation of sperm motility and to determine the biologically relevant functions of the two molecules, SMIF (sperm motility initiation factor) and HSAP (herring sperm activating peptide), that induce sperm motility in this teleost fish. SMIF and HSAP are chorion-derived molecules that initiate different sperm motility trajectories, and do so via different sperm surface receptors that may involve independent signaling mechanisms. It has also been suggested that the two motility initiating systems have different functions in fertilization, that is, they are more than redundant or backup means of achieving sperm motility. The proposed research is a U.S.-Japan collaboration which brings researchers from two laboratories that have identified different herring sperm motility initiators. The proposal seeks to determine the targets, mechanisms of action and biological functions of both motility inducing molecules.The study proposes to: 1), Immunologically and biochemically identify and characterize the sperm surface receptors for the two motility initiators, SMIF and HSAP. 2) Determine the role(s) of the receptors in effecting different sperm trajectories and eliciting a chemotactic through specific receptor activation and inhibition studies. 3) Elucidate the ionic events and signaling mechanisms associated with HSAP and SMIF motility initiation by determining the interdependence of Ca2+ and Na+ fluxes, the role of a membrane Na+-Ca2+ exchanger, the involvement of phospohorylation by Protein Kinase C, and by delineating the ionic fluxes associated with the different sperm motility patterns and sperm receptor activation. 4) Investigate the role for each inducer in situ, with respect to sperm motility induction and fertilization, through the use of antibodies, signal transduction and ion channel blockers, and selective removal and addition of each molecule.