Identification of a determinant of acetylcholine receptor gating kinetics in the extracellular portion of the γ subunit

Sergio Fucile, Anna M. Mileo, Francesca Grassi, Anna M. Salvatore, Stefano Alemà, Fabrizio Eusebi

Research output: Contribution to journalArticlepeer-review

Abstract

A large body of structure-function studies has identified many of the functional motifs underlying ion permeation through acetylcholine receptor (AChR) channels. The structural basis of channel gating kinetics is, however, incompletely understood. We have previously identified a novel shorter form of the AChR γ subunit, which lacks the 52 amino acids within the extracellular amino-terminal half, encoded by exon 5. To define the contribution of the missing domain to AChR channel function, we have transiently coexpressed the mouse short γ subunit (γ(s)) with α, β and δ subunits in human cells and recorded single-channel currents from the resulting AChRs, Our findings show that replacement of the γ by the γ(s) subunit confers a long duration characteristic to AChR channel openings without altering unitary conductance sizes or receptor affinity for the transmitter. We also show that αβγ(s)δ AChR channels exhibit a peculiar voltage sensitivity characterized by a short opening duration when the membrane potential is hyperpolarized. Together, these findings indicate that the domain in the extracellular amino-terminal half of the γ subunit that encompasses a conserved disulphide loop and a critical tyrosine residue implicated in receptor oligomerization and insertion at the cell surface is a functional motif that also modulates AChR channel gating kinetics. The results also provide a molecular explanation of the functional diversity exhibited by skeletal muscle AChRs during development.

Original languageEnglish
Pages (from-to)2564-2570
Number of pages7
JournalEuropean Journal of Neuroscience
Volume8
Issue number12
DOIs
Publication statusPublished - Dec 1996

Keywords

  • γ subunit
  • Ion channel gating kinetics
  • Mouse
  • Nicotinic acetylcholine receptor
  • Transfection

ASJC Scopus subject areas

  • Neuroscience(all)

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