Effects of unsaturated fatty acids on the conformational state of nicotinic acetylcholine receptor.

PERILLO, V. L.; BARRANTES, F. J.; ANTOLLINI, S. S.

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2010

Free fatty acids (FFA) are non-competitive antagonists of the nicotinic acetylcholine receptor (AChR) and their site of action is supposedly located at the lipid-AChR interface, where lipids can be annular or non-annular. It is known that the cis-unsaturated FFA, and not trans-unsaturated FFA, produce conformational modifications in the AChR resting state. Using T. californica receptor-rich membranes, we studied the changes in AChR conformational state generated by differences in the double-bond position of monounsaturated FFA. Using the higher affinity of the fluorescent AChR blocker crystal violet for the desensitized than for the resting state, it was observed that a double bond in positions ù6 or ù9 increased the KD values of the AChR in the desensitized state whereas no effect was observed in ù11 or ù13. Only FFA with an ù9 double bond changed the KD values in the resting state. DPH and Laurdan fluorescence studies showed that fluidity increased the most in FFA with ù9 and ù11 double bonds and that ù6 and ù13 had less effect. Fluorescence resonance energy transfer experiments showed that the FFA with an ù6 double bond remained as an annular lipid whereas all the others also interact at non-annular sites. Thus, the location of the unsaturated double bond appears to be of critical importance for FFA-AChR interaction.