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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
105
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.