Nicotinic acetylcholine receptor and lipid domains in reconstituted model membranas

BERMÚDEZ, V.; ANTOLLINI, S. S.; AVELDAÑO, M. I.; BARRANTES, F. J.

San Miguel de Tucumán, Tucumán, Argentina

Congreso; 45 Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2009

Nicotinic acetylcholine receptor and lipid domains in reconstituted model membranes Vicente Bermúdez, Silvia S. Antollini, Marta I. Aveldaño and Francisco J. Barrantes. Inst. Invest. Bioquímicas de Bahía Blanca, CONICET-Univ. Nac. Sur, Bahía Blanca, Argentina. It has been proposed that the nicotinic acetylcholine receptor (AChR) is preferentially located in ordered lipid domains (rafts); however the reasons for this preference are not clear. Affinity purified AChR from T. californica and a synthetic transmembrane peptide (gM4, the AChR region in closer contact with lipids) were reconstituted into liposomes having a lipid composition resembling that of raft domains (PC:SM:Chol, 1:1:1). Their distribution in membrane domains was assessed by Förster resonance energy transfer between AChR intrinsic fluorescence and dehydroergosterol (fluorescent cholesterol probe). AChR exhibited no preference for any membrane domain. In contrast, gM4 peptide showed a distinct preference for raft-like domains. We characterized the lipid composition of detergent resistant and soluble fractions (DRMs and DSM, respectively) obtained after treatment of the liposomes, with or without protein, with 1% Triton X-100 at 4°C. DRMs and DSMs were enriched in Chol and POPC, respectively, and the presence of AChR or gM4 did not change this lipid distribution. However, AChR induced a significant increase in the amount of the DSM fraction, whereas gM4 caused an opposite effect. Thus the AChR membrane location does not result exclusively from intrinsic physicochemical properties of the protein but is likely to depend on extrinsic factors.