A necessary connection: cholesterol and nicotinic receptors

FABIANI, C.; PEÑALVA, D.A.; CORRADI, J.; ANTOLLINI, S.S.

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2019

Sociedad Argentina de Biofísica

It is known that the muscle nicotinic acetylcholine receptor (nAChR) is highly influencedby its lipid environment. It is present in high-density clusters in the muscle cellmembrane where it localizes mainly in liquid-ordered (Lo) domains enriched incholesterol and sphingolipids. Its transmembrane domain forms the ion channel pore andexhibits extensive contacts with the surrounding lipids. In this work we studied the closerelationship between nAChR and cholesterol under different experimental conditions inorder to enrich with, deplete of, redistribute between both hemilayers, and oxidatecholesterol molecules. These conditions were evaluated either in T. californica nAChR-richmembranes, in model membranes containing purified nAChR or in cells expressingnAChR. Cholesterol modifications were confirmed by lipid analysis using thin layerchromatography. Evaluation of a) membrane order perturbations, by Laurdan GP andfluorescence anisotropy, b) increase/decrease of Lo domains, by fluorescencemicroscopy, c) nAChR-Lo domains correlation, by detergent treatment and SDS-PAGE,and d) nAChR conformation and function, by fluorescence spectroscopy andelectrophysiology showed that changes in the amount, distribution or oxidation ofcholesterol impacts not only in the size, location and curvature-domain shape of Lodomains and in the nAChR preference for them, but also in nAChR functionality andnAChR structural conformation. A high correlation between the quantitative presence ofcholesterol, its transmembrane and lateral asymmetry and nAChR conformation andfunctionality is postulated.