Acid-sensing ion channel (ASIC) 1a/2a heteromers have a flexible 2:1/1:2 stoichiometry

Proc Natl Acad Sci U S A. 2014 Jun 3;111(22):8281-6. doi: 10.1073/pnas.1324060111. Epub 2014 May 20.

Abstract

Acid-sensing ion channels (ASICs) are widely expressed proton-gated Na(+) channels playing a role in tissue acidosis and pain. A trimeric composition of ASICs has been suggested by crystallization. Upon coexpression of ASIC1a and ASIC2a in Xenopus oocytes, we observed the formation of heteromers and their coexistence with homomers by electrophysiology, but could not determine whether heteromeric complexes have a fixed subunit stoichiometry or whether certain stoichiometries are preferred over others. We therefore imaged ASICs labeled with green and red fluorescent proteins on a single-molecule level, counted bleaching steps from GFP and colocalized them with red tandem tetrameric mCherry for many individual complexes. Combinatorial analysis suggests a model of random mixing of ASIC1a and ASIC2a subunits to yield both 2:1 and 1:2 ASIC1a:ASIC2a heteromers together with ASIC1a and ASIC2a homomers.

Keywords: BLINaC; ENaC; single-molecule imaging; subunit counting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Sensing Ion Channels / chemistry*
  • Acid Sensing Ion Channels / physiology*
  • Acidosis / physiopathology
  • Analgesics / chemistry
  • Animals
  • Drug Design
  • Green Fluorescent Proteins / chemistry
  • Humans
  • Hydrogen-Ion Concentration
  • Luminescent Proteins / chemistry
  • Models, Chemical*
  • Oocytes / physiology
  • Patch-Clamp Techniques
  • Protein Multimerization
  • Protein Structure, Quaternary
  • Protons
  • Red Fluorescent Protein
  • Xenopus

Substances

  • ASIC1 protein, human
  • ASIC2 protein, human
  • Acid Sensing Ion Channels
  • Analgesics
  • Luminescent Proteins
  • Protons
  • Green Fluorescent Proteins