A nonproton ligand sensor in the acid-sensing ion channel

Neuron. 2010 Oct 6;68(1):61-72. doi: 10.1016/j.neuron.2010.09.001.

Abstract

Acid-sensing ion channels (ASICs) have long been considered as extracellular proton (H(+))-gated cation channels, and peripheral ASIC3 channels seem to be a natural sensor of acidic pain. Here, we report the identification of a nonproton sensor on ASIC3. We show first that 2-guanidine-4-methylquinazoline (GMQ) causes persistent ASIC3 channel activation at the normal pH. Using GMQ as a probe and combining mutagenesis and covalent modification analysis, we then uncovered a ligand sensor lined by residues around E423 and E79 of the extracellular "palm" domain of the ASIC3 channel that is crucial for activation by nonproton activators. Furthermore, we show that GMQ activates sensory neurons and causes pain-related behaviors in an ASIC3-dependent manner, indicating the functional significance of ASIC activation by nonproton ligands. Thus, natural ligands beyond protons may activate ASICs under physiological and pathological conditions through the nonproton ligand sensor, serving for channel activation independent of abrupt and marked acidosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Sensing Ion Channels
  • Acids / pharmacology
  • Amiloride / therapeutic use
  • Animals
  • Behavior, Animal / drug effects
  • Biophysics / methods
  • Calcium / metabolism
  • Cells, Cultured
  • Cricetinae
  • Cricetulus
  • Disease Models, Animal
  • Dithionitrobenzoic Acid / pharmacology
  • Dose-Response Relationship, Drug
  • Electric Stimulation / methods
  • Ganglia, Spinal / cytology
  • Glutamates / metabolism
  • Guanidines / chemistry
  • Guanidines / pharmacology
  • Hydrogen-Ion Concentration
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / genetics
  • Ion Channel Gating / physiology*
  • Ligands
  • Membrane Potentials / drug effects
  • Membrane Potentials / genetics
  • Mice
  • Mice, Knockout
  • Mutagenesis, Site-Directed / methods
  • Mutation / genetics
  • Nerve Tissue Proteins / deficiency
  • Nerve Tissue Proteins / drug effects
  • Nerve Tissue Proteins / physiology*
  • Pain / chemically induced
  • Pain / drug therapy
  • Pain / physiopathology
  • Pain Measurement
  • Patch-Clamp Techniques
  • Protein Structure, Tertiary / drug effects
  • Protein Structure, Tertiary / physiology
  • Protons
  • Quinazolines / chemistry
  • Quinazolines / pharmacology
  • Rats
  • Sensory Receptor Cells / chemistry
  • Sensory Receptor Cells / drug effects
  • Sensory Receptor Cells / physiology*
  • Sodium Channels / deficiency
  • Sodium Channels / drug effects
  • Sodium Channels / physiology*
  • Sulfhydryl Reagents / pharmacology
  • Time Factors
  • Transfection / methods

Substances

  • 2-guanidine-4-methylquinazoline
  • ASIC3 protein, rat
  • Acid Sensing Ion Channels
  • Acids
  • Glutamates
  • Guanidines
  • Ligands
  • Nerve Tissue Proteins
  • Protons
  • Quinazolines
  • Sodium Channels
  • Sulfhydryl Reagents
  • gamma-glutamylmethylamide
  • Amiloride
  • Dithionitrobenzoic Acid
  • Calcium