Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Tuesday Speaker Abstracts

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.

9