Two rare variations, D478N and D478E, that occur at the same amino acid residue in nicotinic acetylcholine receptor (nAChR) α2 subunit influence nAChR function

NEUROPHARMACOLOGY

卷:85

Article

Dash, Bhagirathi¹  Li, Ming D.¹ 

[1] Univ Virginia, Sch Med, Dept Psychiat & Neurobehav Sci, Charlottesville, VA 22911 USA

关键词: Nicotinic acetylcholine receptor;    Single nucleotide variation;    Missense mutation;    Receptor structure-function;    Electrophysiology;   

DOI  :  10.1016/j.neuropharm.2014.05.014

来源: Elsevier

【 摘 要 】

There occur two rare variations, Asp(D)478Asn(N) and Asp(D)478GIu(E), in the putative cytoplasmic amphipathic alpha-helices of human nicotinic acetylcholine receptor (nAChR) alpha 2 subunit as a result of mutation in the 1st (G -> A: rs141072985) and 3rd (C -> A: rs56344740) nucleotide of its 478th triplet codon (GAC). We assessed the effects of these two variations on the function of alpha 2 beta 2- and alpha 2 beta 4-nAChRs as they could alter the electronegativity and/or the structure of the cytoplasmic 'portals' (framed by subunit amphipathic alpha-helices) necessary for obligate ion permeation from extracellular space to cytoplasm. We injected decreasing ratio of subunit cRNAs (alpha:beta; 10:1, 1:1 and 1:10) into Xenopus oocytes to express putative low-sensitivity (LS; 10:1), intermediate-sensitivity (IS; 1:1) and high sensitivity (HS; 1:10) isoforms of wild type and variant alpha 2 beta 2- and alpha 2 beta 4-nAChRs. Two-electrode voltage clamp analyses indicate that the agonist (ACh or nicotine) induced peak current responses (I-max) of alpha 2 beta 2-nAChR isoforms and those of alpha 2 beta 4-nAChR isoforms are increased (1.3-4.7-fold) as a result of D478E variation. The alpha 2 subunit D478N variation only increases the I-max of IS (similar to 2-fold) or HS (1.4-2.1-fold) alpha 2 beta 2-nAChRs. Concentration-response curves constructed indicate no effect on agonist sensitivities of LS and HS isoforms of alpha 2 beta 2- and alpha 2 beta 4-nAChRs as a result of either variation in alpha 2 subunit. Between the two variant nAChRs, alpha 2(D478E)*-nAChR isoforms generally yield higher I-max than those of respective alpha 2(D478N)*-nAChR isoforms. These effects could be attributed to alteration in cytoplasmic 'portals' and/or ion permeation through it owing to change in amino acid electronegativity (D -> N) and side chain length (D -> E) in nAChR alpha 2 subunit. (C) 2014 Elsevier Ltd. All rights reserved.

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