Gating of alpha sub(3) beta sub(4) neuronal nicotinic receptor can be controlled by the loop M2-M3 of both alpha sub(3) and beta sub(4) subunits

• Published in: Pflügers Archiv Vol. 439; no. 1-2; pp. 86 - 92
• Main Authors: Rovira, J C, Vicente-Agullo, F, Campos-Caro, A, Criado, M, Sala, F, Sala, S, Ballesta, J J
• Format: Journal Article
• Language: English
• Published: 01.12.1999
• Subjects: Acetylcholine receptors (nicotinic); Xenopus
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s004249900143

Previous studies have shown that the gating mechanism of alpha sub(3) beta sub(4) neuronal nicotinic receptors is affected by a residue in the middle of the M2-M3 loop of the beta sub(4) subunit. We have extended the study of the same location to the alpha sub(3) subunit. Bovine alpha sub(3) beta sub(4) receptors were mutated in position 268, substituting the residue present in wild-type receptors, i.e. leucine in alpha sub(3) and asparagine in beta sub(4), for an aspartate. Wild-type and mutated alpha sub(3 )and beta sub(4) subunits were combined to form four different receptors. We have measured macroscopic currents in Xenopus oocytes elicited by nicotine, and related them to surface receptor expression measured with an epibatidine-binding essay. We also obtained single-channel recordings of the receptors to study their kinetic behaviour. The results were analysed in terms of an allosteric model with three states. We found that the effect of the mutation in the alpha sub(3) subunit on the gating of the receptor was similar to the corresponding mutation in the beta sub(4) subunit. The effect when both subunits were mutated was additive, suggesting that the contribution of each subunit to the gating mechanism is independent.