Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

4-POS

Board 4

Functional Analysis of the Voltage Sensor Domain Present in the Mammalian Sperm-

Specific Na

Exchanger by Patch-Clamp Fluorometry of Chimeric Fluorescent Voltage

Sensor

César Arcos Hernández

, Takuya Nishigaki.

Instituto de Biotecnología, Cuernavaca, Morelos, Mexico.

Sperm motility is accurately regulated by several enzymes, transporters and ion channels. Some

of these proteins are expressed only in spermatozoa, but the functional relationship among them

is not fully understood. Sperm-specific Na

exchanger (sNHE) is an essential protein for

mouse sperm motility regulation and is localized in the principal piece of mammalian

spermatozoa. Differently from somatic NHEs, sNHE has two predicted regulatory domains, a

voltage sensor domain (VSD) and a cyclic nucleotide binding domain (CNBD), although their

functionality remains to be confirmed. In the case of the VSD, it has been proposed that

hyperpolarization caused by Slo3 (a sperm specific K

channel) promotes an intracellular

alkalization by the sNHE through this VSD. This signal cascade is thought to be involved in

sperm hyperactivation. Interestingly, there are experiments that suggest the VSD of sNHE is

functional in mice but not in humans. Correlating this, the fourth transmembrane segment of the

VSD of the human sNHE, but not the mouse sNHE, lacks an arginine in a critical position, which

could cause the domain not to be functional. To demonstrate functional differences in the VSD

of the sNHE between human and mouse, we will produce fluorescent voltage sensors (VSFPs)

using Arclight, a popular VSFP, as a template and replace its VSD by that of sNHE. We will

analyze the biophysical properties of the VSFPs expressed in HEK293 cells by using patch

clamp fluorometry and extrapolate the function of the VSDs of human and mouse sNHE.

This project is supported by PAPIIT (DGAPA IN206116).