Structural basis for α-bungarotoxin insensitivity of neuronal nicotinic acetylcholine receptors

NEUROPHARMACOLOGY

卷:160

Article

Sine, Steven M.^1,2,3  Strikwerda, John R.¹  Mazzaferro, Simone¹ 

[1] Mayo Clin, Coll Med, Dept Physiol & Biomed Engn, Receptor Biol Lab, Rochester, MN 55905 USA

[2] Mayo Clin, Coll Med, Dept Pharmacol & Expt Therapeut, Rochester, MN 55905 USA

[3] Mayo Clin, Coll Med, Dept Neurol, Rochester, MN 55905 USA

关键词: Neuronal nicotinic acetylcholine receptor;    alpha-subunit;    alpha-Bungarotoxin;    Radio-ligand binding;    Sucrose gradient analysis;    Single channel recording;    3D structure;    Inter-residue interactions;   

DOI  :  10.1016/j.neuropharm.2019.05.037

来源: Elsevier

【 摘 要 】

The ten types of nicotinic acetylcholine receptor alpha-subunits show substantial sequence homology, yet some types confer high affinity for alpha-bungarotoxin, whereas others confer negligible affinity. Combining sequence alignments with structural data reveals three residues unique to alpha-toxin-refractory alpha-subunits that coalesce within the 3D structure of the alpha 4 beta 2 receptor and are predicted to fit between loops I and II of alpha-bungarotoxin. Mutating any one of these residues, Lys189, Ile196 or Lys153, to the alpha-toxin-permissive counterpart fails to confer alpha-bungarotoxin binding. However, mutating both Lys189 and Ile196 affords alpha-bungarotoxin binding with an apparent dissociation constant of 104 nM, while combining mutation of Lys153 reduces the dissociation constant to 22 nM. Analogous residue substitutions also confer high affinity alpha-bungarotoxin binding upon alpha-toxin-refractory alpha 2 and alpha 3 subunits. alpha 4 beta 2 receptors engineered to bind alpha-bungarotoxin exhibit slow rates of alpha-toxin association and dissociation, and competition by cholinergic ligands typical of muscle nicotinic receptors. Receptors engineered to bind alpha-bungarotoxin co-sediment with muscle nicotinic receptors on sucrose gradients, and mirror single channel signatures of their alpha-toxin-refractory counterparts. Thus the inability of alpha-bungarotoxin to bind to neuronal nicotinic receptors arises from three unique and interdependent residues that coalesce within the receptor's 3D structure.

【 授权许可】

Free