Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

11-POS

Board 11

Regulation of K2P Potassium Channels by Membrane Cholesterol

Galit Blecher

, Noam Zilberberg.

Ben-Gurion University of the Negev, Beer-Sheva, Israel.

Potassium leak channels (K

) play a central role in setting the membrane resting potential. Their

activity is regulated by physical and chemical effectors such as temperature, pH, mechanical

stretch and phosphorylation. Cholesterol is an essential structural component of mammalian cell

membranes and it also is a main component of lipid rafts, which are cholesterol/sphingomyeline

enriched microdomains in the membrane. It was found that membrane cholesterol regulates the

activity of several membrane proteins. In this study, we describe the mechanism by which

membrane cholesterol levels affects K

channels activity.

We studied the influence of membrane cholesterol levels on several members of the K

family:

human K

2.1, K

3.1, K

5.1 and K

9.1 channels as well as K

0 channels from Drosophila

melanogaster, all expressed in

Xenopus laevis

oocytes and studied using the two electrode voltage

clamp technique (TEVC). Depletion of membrane cholesterol using Methyl-β-cyclodextrin

(MβCD) altered the activity of most tested channels. Application of 1-5mM MβCD reduced

2.1 currents by 80% and increased K

0 currents 7-fold. Other channels displayed milder

responses. In accordance with these results, sphingomyelin hydrolysis by sphingomyelinase had

effects similar to those of MβCD on K

2.1 channels. Unlike most cholesterol sensitive channels,

2.1 channels are not expressed within lipid rafts and are not affected by the elimination of

consensus cholesterol binding domains. While mutant K

2.1 and K

0 channels, that are

insensitive to phosphorylation, were not affected by cholesterol depletion, G-protein activity

blockade had no effect. We thus conclude that the activity of members of the K

potassium

channels is regulated by membrane cholesterol and speculate that K

2.1 channel's activity is

regulated via alteration of kinase activity.