US-Mexico Cooperative Research: cGMP Regulated Ionic Channels in Sperm

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This award will support Prof. Bennett Shapiro of the University of Washington in a research collaboration with Prof. Alberto Darszon of the Centro de Investigacrones y Estudios Avanzador (CINVESTAV) in Mexico City. The reserarchers intend to explore the mechanism whereby sea urchinsperm respond to eggs of the same species. It is known that peptides that diffuse from the egg to bind at the sperm surface cause the sperm to alter several ultra cellular parameters. The pepticles may play a chemotactic role and also cause transient elevations in ultracellular ıCa2+! and ıcEMP!. Preliminary data suggests the presence of a cGMP- dependent Ca2+ chfannel in plasma membranes from the sperm. Possible candidates for such a channel will be purified and their characteristics explored in reconstituted bilayer systems. Such a channel may be a component of the signal tranduction pathway of sperm chemotaxis; an analysis of its properties may clarify the mechanism of the analogoris channel that is responsible for photo transduction.l The sea urchin sperm offers some distinct advantages one more complex cell types as a basic model for chemostraxis. Many of the superflous (in this context) cellular activities related to the cell cycle, growth, and differentiation are absent from the spermitozoan. The amplified metabolism of this non-dividing cell and its limited stimulus for chemotaxis are in contrast to E. coli, which respond to a host of attractants and repellants and are actively growing and dividing. Thus the metabolically mono focused sperm array allow researchers to unearth some biochemical mechanism in the pathway of chemotaxis. By combing the strengthsof the Mexian group in planar bilayer studies with special interests in the recoinstitution of membraneprotein channels, with the experience of the U.S. group in functional studies of purified proteins that mediato cellular behavior, this study has the potential to increase our understanding of sperm chemotaxis and egg-sperm interaction.