Classification of ion channels

At present, about 300 different ion channels have been identified in humans. Usually, ion channels are classified according to gating mechanism (voltage-gated, ligand-gated, cyclic nucleotide-gated, lipid-gated, light-gated, temperature-gated, mechanosensitive), ion selectivity (sodium channels, potassium channels, chloride channels, calcium channels, proton channels, nonselective channels), or cellular localization (plasma membrane or intracellular).

The current unified nomenclature of mammalian ion channels is based on the recommendations of The International Union of Basic and Clinical Pharmacology (IUPHAR) (https://www.guidetopharmacology.org/) together with The Human Genome Organization (HUGO) nomenclature committee (HGNC) (https://www.genenames.org/). Although the efforts of these two organizations are hugely important and helpful, there are some discrepancies in how they view the final classification. IUPHAR uses the ion channel names, which are mostly used in the literature, and therefore IUPHAR classification is preferred by ion channel researchers. In contrast, HGNC proposes to assign the unique symbols and names to each human gene/protein and therefore is preferred by genome biologists. To give you an example, HGNC sees voltage-gated sodium channel Nav1.7 (IUPHAR’s nomenclature) as SCN9A, so the protein name is the same as the gene’s (SCN9A) except that it’s not italicized.

Below you’ll find different classifications of human ion channels.

Classification by gating mechanism.

  • Voltage-gated ion channels
  • Ligand-gated ion channels
  • Cyclic nucleotide-gated ion channels
  • Lipid-gated ion channels
  • Temperature-gated ion channels
  • Mechanosensitive ion channels

Classification by ion selectivity.

  • Sodium channels
  • Potassium channels
  • Chloride channels
  • Calcium channels
  • Proton channels
  • Nonselective channels

Classification by cellular localization.

  • Plasma membrane ion channels
  • Intracellular ion channels
    • Endoplasmic reticulum ion channels
    • Mitochondrial ion channels
    • Lysosomal ion channels
    • Endosomal ion channels
    • Nuclear ion channels

Other classifications.

  • Leak channels
  • Constitutively open channels
  • Ion channels with non-channel functions

Non-human ion channels.

  • Invertebrate Ion Channels
  • Viral ion channels
  • Bacterial ion channels
  • Plant ion channels
  • Synthetic/Artificial ion channels
  • Light-gated ion channels