Conformational rearrengement of the nicotinic acetylcholine receptor induced by its lipid microenvironment.

ANTOLLINI, S.S.; FERNÁNDEZ NIEVAS, G.A.; BARRANTES, F.J.

Pinamar

Congreso; X Congress Panamerican Association for Biochemistry and Molecular Biology (PABMB); XLI Annual Meeting Argentine Society for Biochemistry and Molecular Biology Research (SAIB); and XX Annual Meeting Argentine Society for Neurochemistry (SAN); 2005

X Congress Panamerican Association for Biochemistry and Molecular Biology (PABMB); XLI Annual Meeting Argentine Society for Biochemistry and Molecular Biology Research (SAIB); and XX Annual Meeting Argentine Society for Neurochemistry (SAN)

Perturbations of the nicotinic acetylcholine receptor (AChR) native lipid environment alter its function, pointing to the lipid-protein interface as the locus where “lipid signals” are gated to unleash the subsequent ion pore opening and closure, probably initiated by changes in the topology of the outer ring TM segments and ultimately leading to a conformational change of the whole AChR. The possible AChR conformational changes induced by perturbations of its native lipid microenvironment in T. californica AChR-rich membranes were studied with fluorescence spectroscopy using the probe crystal violet (CrV). This probe behaves as an AChR ion blocker, displaying higher affinity for the desensitized conformation (D, in the presence of agonist) than for the resting conformation (R, absence of agonist) of the AChR. We took advantage of these AChR-CrV differences in affinity to monitor AChR conformational states. KD values for AChR-CrV interaction measured in the absence of agonist decreased both in cholesterol-depleted or cholesterol-enriched membranes, suggesting the occurrence of AChR intermediate conformational state(s). Addition of highly hydrophobic molecules that act as AChR non-competitive inhibitors (free fatty acids and steroids) to native membranes in the absence of agonist decreased the KD values to levels obtained in the presence of agonist. The results indicate a direct correlation between lipid environment of the AChR and its conformational state. Supported by grants from UNS, FONCYT and TWAS.