Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

45-POS Board 45 Electrophysiological Characterization of Ionic Current in Sea Urchin Sperm Verónica Loyo Celis , Gerardo Orta, Alberto Darszon. Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico. Sea urchins are widely used in studies of developmental biology since they are external fertilizers and possess a large number of gametes. Speract, a decapeptide released from the egg jelly, induces chemotaxis in Lytechinus pictus sea urchin sperm. This peptide triggers several intertwined biochemical and electrophysiological processes that result in intracellular increases in cyclic nucleotides ([cGMP], [cAMP]), pH (pH i ) and Ca 2+ [Ca 2+ ] i , as well as membrane potential changes caused by regulated ionic fluxes of K + , Na + and Ca 2+ . These events lead to [Ca 2+ ] i fluctuations that control flagellar beating and thus sperm swimming paths. The identity of the transporters associated with the [Ca 2+ ] i changes required for chemotaxis is still not fully known. CatSper, a sperm exclusive Ca 2+ channel composed of four alpha subunits and five accessory subunits (beta, gamma, delta, epsilon and zeta), which is expressed exclusively in the flagellum has been detected in sea urchin sperm and there is evidence for it´s involvement in chemotaxis (Seifert et al . Embo J. 2015; Espinal-Enriquez et al . Sci Rep. In press). This work presents initial findings in an endeavor to electrophysiologically characterize CatSper in sea urchin sperm using the patch-clamp technique. Due to the morphology and size of the sea urchin sperm (3-4 µm diameter head and around 50 µm long of the flagella), we have resorted to the technique previously described by Sánchez et al . (FEBS Lett. 2001), which swells sperm diluting sea water 10 fold, which increases the probability of obtaining high resistance seals to record ion currents. Applying this experimental strategy we are now obtaining patch-clamp recordings in the cell attached configuration and detecting macroscopic ionic currents. Support acknowledeged from Consejo Nacional de Ciencia y Tecnología CONACyT Fronteras 71, PAPIIT/UNAM IN205516 and NIH RO1 HD038082-13 to A. Darszon.

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