Calcium channel
A calcium channel is an ion channel which displays selective permeability to calcium ions. It is sometimes synonymous as voltage-dependent calcium channel,[1] although there are also ligand-gated calcium channels.[2]
Comparison tables
The following tables explain gating, gene, location and function of different types of calcium channels, both voltage and ligand-gated.
Voltage-gated
| Type | Voltage | α1 subunit (gene name) | Associated subunits | Most often found in |
| L-type calcium channel ("Long-Lasting" AKA "DHP Receptor") | HVA (high voltage activated) | Cav1.1 (CACNA1S) Cav1.2 (CACNA1C) Cav1.3 (CACNA1D) Cav1.4 (CACNA1F) |
α2δ, β, γ | Skeletal muscle, smooth muscle, bone (osteoblasts), ventricular myocytes** (responsible for prolonged action potential in cardiac cell; also termed DHP receptors), dendrites and dendritic spines of cortical neurones |
| P-type calcium channel ("Purkinje") /Q-type calcium channel | HVA (high voltage activated) | Cav2.1 (CACNA1A) | α2δ, β, possibly γ | Purkinje neurons in the cerebellum / Cerebellar granule cells |
| N-type calcium channel ("Neural"/"Non-L") | HVA (high-voltage-activated) | Cav2.2 (CACNA1B) | α2δ/β1, β3, β4, possibly γ | Throughout the brain and peripheral nervous system. |
| R-type calcium channel ("Residual") | intermediate-voltage-activated | Cav2.3 (CACNA1E) | α2δ, β, possibly γ | Cerebellar granule cells, other neurons |
| T-type calcium channel ("Transient") | low-voltage-activated | Cav3.1 (CACNA1G) Cav3.2 (CACNA1H) Cav3.3 (CACNA1I) |
neurons, cells that have pacemaker activity, bone (osteocytes), thalamus (thalamus) |
Ligand-gated
- the receptor-operated calcium channels (in vasoconstriction)
| Type | Gated by | Gene | Location | Function |
| IP3 receptor | IP3 | ITPR1, ITPR2, ITPR3 | ER/SR | Releases calcium from ER/SR in response to IP3 by e.g. GPCRs[4] |
| Ryanodine receptor | dihydropyridine receptors in T-tubules and increased intracellular calcium (Calcium Induced Calcium Release - CICR) | RYR1, RYR2, RYR3 | ER/SR | Calcium-induced calcium release in myocytes[4] |
| Two-pore channel | ||||
| Cation channels of sperm | ||||
| store-operated channels | indirectly by ER/SR depletion of calcium[4] | ORAI1, ORAI2, ORAI3 | plasma membrane |
Pharmacology
L-type calcium channel blockers are used to treat hypertension.
References
- ^ "calcium channel" at Dorland's Medical Dictionary
- ^ Striggow F, Ehrlich BE (August 1996). "Ligand-gated calcium channels inside and out". Curr. Opin. Cell Biol. 8 (4): 490–5. doi:10.1016/S0955-0674(96)80025-1. PMID 8791458.
- ^ Walter F., PhD. Boron (2005). Medical Physiology: A Cellular And Molecular Approach. Elsevier/Saunders. ISBN 1-4160-2328-3. Page 479
- ^ a b c Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. Page 53
External links
- "Voltage-Gated Ion Channels". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.
{{cite web}}: Cite has empty unknown parameter:|coauthors=(help) - "TRIP Database". a manually curated database of protein-protein interactions for mammalian TRP channels.
{{cite web}}: Cite has empty unknown parameter:|coauthors=(help) - Calcium+Channels at the U.S. National Library of Medicine Medical Subject Headings (MeSH)