Background and purpose. The α7 and α4ß2* (* denotes possibly assembly with another subunit) nicotinic acetylcholine receptors (nAChR) are the most abundant nAChR in the mammalian brain. These receptors are also the most commonly targeted nAChR in drug discovery programs for brain disorders. However, the development of subtype-specific agonists remains challenging, mainly due to the high degree of sequence homology and conservation of function in nAChR. We have developed C(10) variants of cytisine, a partial agonist of α4ß2 nAChR that has been used for smoking cessation. The C(10) methyl analogue used in this study displays negligible affinity for α7 nAChR, while retaining high-affinity for α4ß2 nAChR.
Experimental approach. The structural underpinning of the selectivity of 10-methylcytisine for α7 and α4ß2 nAChR was investigated using molecular dynamics simulations, mutagenesis and whole-cell and single-channel current recordings.
Key results. We identified a conserved arginine in the ß3-strand that exhibits a non-conserved function in nAChR. In α4ß2 nAChR, the arginine forms a salt-bridge with an aspartate residue in loop B that is necessary for receptor expression, whereas in α7 nAChR, this residue is not stabilised by electrostatic interactions, making its side chain highly mobile. This lack of constrain produces steric clashes with agonists and affects the dynamics of residues involved in agonist binding and the coupling network.
Conclusions and implications. We conclude that the high mobility of the ß3-strand arginine in the α7 nAChR influences agonist binding, and possibly gating network and desensitisation. The findings have implications for rational design of subtype-selective nAChR agents.
Minguez-Viñas, TeresaNielsen, Beatriz E.Shoemark, Deborah K.Gotti, CeciliaSessions, Richard B.Mulhollad, Adrian J.Bouzat, CeciliaWonnacott, SusanGallagher, TimothyBermudez, IsabelOliveira, A. Sofia
Department of Biological and Medical Sciences
Year: Not yet published.
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