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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
84
56-POS
Board 56
CatSper Channels Are Activated by PKA in Mouse Sperm
Gerardo Orta
1
, José L. De la Vega-Beltran
1
, David Martín-Hidalgo
2
, Pablo E. Visconti
2
,
Alberto Darszon
1
.
1
Instituto de Biotecnología-Universidad Nacional Autónoma de México, Cuernavaca, Morelos,
Mexico,
2
University of Massachusetts, Amherst, MA, USA.
In mammals, sperm become motile during ejaculation and swim up the female reproductive tract
where they undergo physiological changes named capacitation before being capable of fertilizing
the egg. One of the first signaling events is an intracellular cAMP elevation triggered by HCO3-
influx which activates the soluble adenylyl cyclase (sAC)1, leading to PKA-dependent protein
phosphorylation2. CatSper, a sperm exclusive, alkali- and voltage-gated Ca2+ channel, has been
proposed to be responsible for the Ca2+ influx that accompanies and is necessary for
capacitation. The key role of cAMP in capacitation and fertilization was demonstrated using
pharmacological tools for gain and loss of function of PKA-dependent pathways3 and confirmed
with sAC null mouse models whose sperm are sterile4. We hypothesized that CatSper is the
molecular candidate in this mechanistic pathway. We tested this possibility using western blot
analysis, Em and [Ca2+]i measurements, and CatSper whole-cell patch-clamp current
recordings. Our results show a direct regulation of CatSper by PKA when stimulated by HCO3-
influx. Notably, in whole-cell patch-clamp recordings, cAMP in the pipette solution activates
CatSper currents strongly and this effect is blocked by PKA inhibitors H89 and PKI.
Pharmacological inhibition of the PKA-pathway and CatSper blockade annul the effect of
HCO3- on: [Ca2+]i levels, Em and CatSper currents. Additionally, our experiments with sperm
from CatSper KO mice confirm that HCO3- does not alter the ionic currents obtained under
CatSper channel recording conditions. All together our results indicate that CatSper channels are
activated by PKA directly, having a major role in the Ca2+ influx occurring during capacitation.
These findings have significant implications for our understanding of fertilization.
Support acknowledged from CONACyT Fronteras 71, PAPIIT/UNAM IN205516 and NIH RO1
HD038082-13 to Darszon A. NIH RO1 HD038082-13 to Visconti PE.