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Emerging Concepts in Ion Channel Biophysics
Tuesday Speaker Abstracts
9
Glutamate Receptor Dynamics
Vasanthi Jayaraman
.
University of Texas Medical School at Houston, TX, USA.
No Abstract
Ion Channels and Sperm Physiology
Polina V. Lishko
1
, Nadja Mannowetz
1
, Melissa R. Miller
1
, Sam Kenny
2
, Ke Xu
2
.
1
UC Berkeley, Berkeley, CA, USA,
2
UC Berkeley, Berkeley, CA, USA.
Ion channels control sperm cell physiology by regulating membrane potential, intracellular levels
of calcium and pH: intracellular calcium stimulates sperm hyperactivated motility, whereas
intracellular protons inhibit it. Steroid hormone progesterone produced by an ovulated egg,
promotes calcium influx through sperm channel CatSper- an event so central for fertilization that
men lacking these channels are infertile. Human CatSper is associated with membrane non-
genomic receptor- serine hydrolase ABHD2- that degrades endogenous CatSper inhibitor 2-
arachidonoylglycerol upon progesterone exposure. ABHD2 is ubiquitously expressed, and the
pathway discovered in spermatozoa, is likely a universal pathway that defines membrane
progesterone signaling in other tissues. ABHD2 prefers progesterone over most steroids,
however its steroid-specificity profile provides an unexpected insight on how female
reproductive cycle can regulate sperm fertility. Activation of CatSper channel upon progesterone
exposure happens in less than a second, thus allowing calcium changes to propagate rapidly to
achieve a concerted movement. Such signaling event is ensured by a nanodomain organization of
the sperm control units that are located in close proximity to each other. The combination of
superresolution imaging method (STORM) and electrophysiology helps to reveal a detailed
nanodomain organization of sperm control units, as well as to understand their fine tuning and
regulation.