Format

Send to:

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 2011 Nov 4;286(44):37990-9. doi: 10.1074/jbc.M111.258012. Epub 2011 Sep 8.

Discrete M3-M4 intracellular loop subdomains control specific aspects of γ-aminobutyric acid type A receptor function.

Author information

  • 1Department of Anesthesiology, Emory University, Atlanta, Georgia 30322, USA.

Abstract

The GABA type A receptor (GABA(A)R) is a member of the pentameric ligand gated ion channel (pLGIC) family that mediates ionotropic neurotransmission. Residues in the intracellular loop domain (ILD) have recently been shown to define part of the ion permeation pathway in several closely related members of the pentameric ligand gated ion channel family. In this study, we investigated the role the ILD of the GABA(A)R α1 subunit plays in channel function. Deletion of the α1 ILD resulted in a significant increase in GABA EC(50) and maximal current amplitude, suggesting that the ILD must be intact for proper receptor function. To test this hypothesis, we conducted a mutagenic screen of all amino acids harboring ionizable side chains within this domain to investigate the contribution of individual charged residues to ion permeation. Using macroscopic and single channel voltage-clamp recording techniques, we found that mutations within a subdomain of the α1 ILD near M3 altered GABA apparent affinity; interestingly, α1(K312E) exhibited reduced partial agonist efficacy. We introduced point mutations near M4, including α1(K383E) and α1(K384E), that enhanced receptor desensitization. Mutation of 5 charged residues within a 39-residue span contiguous with M4 reduced relative anion permeability of the channel and may represent a weak intracellular selectivity filter. Within this subdomain, the α1(K378E) mutation induced a significant reduction in single channel conductance, consistent with our hypothesis that the GABA(A)R α1 ILD contributes directly to the permeation pathway.

PMID:
21903587
[PubMed - indexed for MEDLINE]
PMCID:
PMC3207432
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk