Interactions between highly hydrophobic molecules and the acetylcholine receptor in native system.

FERNÁNDEZ NIEVAS, G.A.; ANTOLLINI, S.S.

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).

A group of highly hydrophobic molecules, steroids and free fatty acids (FFA), act as non-competitive inhibitors of the nicotinic acetylcholine receptor (AChR). The details of these interactions are still unknown. In this work, we used the fluorescence resonance energy transfer (FRET) between the intrinsic AChR and the probe Laurdan to study effects of FFAs and steroids on AChR-rich membranes from T. californica. Structural different steroids and FFAs produced similar decreases in FRET efficiency (E), and competitive studies between them suggested the occurrence of equivalent sites for both types of molecules at the lipid-protein interface. Endogenous production of FFAs by controlled digestion of membrane phospholipids with phospholipase A2 produced similar decreases of E. Controlled hydrolyzed of T. californica membranes with proteinase K suggests that the interaction sites for steroids and FFA on the AChR are located in its transmembrane regions. Experiments using desensitized AChR (1mM Carb) showed different diminutions of E, suggesting that the sites for hydrophobic molecules are sensitive to AChR conformation, and in particular to rearrangement of the transmembrane portions,  making some of these lipid-protein interface sites (i.e. non annular sites) no further accessible to exogenous molecules.