The position of the double bond in monounsaturated free fatty acids is essential for the inhibition of the nicotinic acetylcholine receptor
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- 作者：Vanesa L. Perillo ; Gaspar A. Fern¨¢ndez-Nievas ; Ana S. Vall¨¦s ; Francisco J. Barrantes ; Silvia S. Antollini
- 关键词：ACh ; acetylcholine ; AChR ; nicotinic acetylcholine receptor ; Carb ; carbamylcholine ; Chol ; cholesterol ; CrV ; crystal violet ; DPH ; 1 ; 6-diphenyl-1 ; 3 ; 5-hexatriene ; FFAs ; free fatty acids ; sFFAS ; saturated free fatty acids ; cis-FFAs ; cis-unsaturated free fatty
- 刊名：Biochimica et Biophysica Acta (BBA)/Biomembranes
- 出版年：2012
- 出版时间：November, 2012
- 年：2012
- 卷：1818
- 期：11
- 页码：2511-2520
- 全文大小：855 K
文摘
Free fatty acids (FFAs) are non-competitive antagonists of the nicotinic acetylcholine receptor (AChR). Their site of action is supposedly located at the lipid-AChR interface. To elucidate the mechanism involved in this antagonism, we studied the effect that FFAs with a single double-bond at different positions (¦Ø6, ¦Ø9, ¦Ø11 and ¦Ø13 cis-18:1) have on different AChR properties. Electrophysiological studies showed that only two FFAs (¦Ø6 and ¦Ø9) reduced the duration of the channel open-state. The briefest component of the closed-time distribution remained unaltered, suggesting that ¦Ø6 and ¦Ø9 behave as allosteric blockers. Fluorescence resonance energy transfer studies indicated that all FFAs locate at the lipid-AChR interface, ¦Ø6 being restricted to annular sites and all others occupying non-annular sites. The perturbation of the native membrane order by FFAs was evaluated by DPH (1,6-diphenyl-1,3,5-hexatriene) and Laurdan fluorescence polarization studies, with the greatest decrease observed for ¦Ø9 and ¦Ø11. AChR conformational changes produced by FFAs present at the lipid bilayer were evaluated by fluorescence quenching studies of pyrene-labeled AChR and also using the AChR conformational-sensitive probe crystal violet. All cis-FFAs produced AChR conformational changes at the transmembrane level, but only ¦Ø9, ¦Ø11 and ¦Ø13 perturbed the resting state. Thus, the position and isomerism of the torsion angle of unsaturated FFAs are probably a key factor in terms of AChR blockage, suggesting that FFAs with a unique cis double bond at a superficial position inside the membrane directly inhibit AChR function by perturbing a potential conserved core structure for AChR gating at that level.