Calcium channel

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A calcium channel is an ion channel which shows selective permeability to calcium ions. It is sometimes synonymous as voltage-gated calcium channel,[1] although there are also ligand-gated calcium channels.[2]

Comparison tables[edit]

The following tables explain gating, gene, location and function of different types of calcium channels, both voltage and ligand-gated.

Voltage-gated[edit]

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 neurons
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[edit]

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 Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) TPCN1, TPCN2 endosomal/lysosomal membranes NAADP-activated calcium transport across endosomal/lysosomal membranes[5]
Cation channels of sperm Calcium (CICR) PKD2 family sperm (specifically flagella) non-selective calcium-activated cation channel directing sperm in female reproductive tract[6]
store-operated channels indirectly by ER/SR depletion of calcium[4] ORAI1, ORAI2, ORAI3 plasma membrane provide calcium signaling to the cytoplasm[7]

Pharmacology[edit]

Depiction of binding sites of various antagonistic drugs in the L-type calcium channel.

L-type calcium channel blockers are used to treat hypertension; in most areas of the body, depolarization is mediated by sodium influx into a cell; changing the calcium permeability has little effect on action potentials. However, in many smooth muscle tissues, depolarization is mediated primarily by calcium influx into the cell. L-type calcium channel blockers selectively inhibit these action potentials in smooth muscle which leads to dilation of blood vessels; this in turn corrects hypertension.[8]

T-type calcium channel blockers are used to treat epilepsy. Increased calcium conductance in the neurons leads to increased depolarization and excitability, this leads to a greater predisposition to epileptic episodes. Calcium channel blockers reduce the neuronal calcium conductance and reduce the likelihood of experiencing epileptic attacks.[9]

References[edit]

  1. ^ "calcium channel" at Dorland's Medical Dictionary
  2. ^ Striggow F, Ehrlich BE (August 1996). "Ligand-gated calcium channels inside and out". Current Opinion in Cell Biology. 8 (4): 490–5. doi:10.1016/S0955-0674(96)80025-1. PMID 8791458. 
  3. ^ Walter F., PhD. Boron (2005). Medical Physiology: A Cellular And Molecular Approach. Elsevier/Saunders. ISBN 1-4160-2328-3.  Page 479
  4. ^ a b c Rang HP (2003). Pharmacology. Edinburgh: Churchill Livingstone. p. 54. ISBN 978-0-443-07145-4. 
  5. ^ "TPCN1 - Two pore calcium channel protein 1 - Homo sapiens (Human) - TPCN1 gene & protein". www.uniprot.org. Retrieved 2017-12-11. 
  6. ^ Gao, Zhiqian; Ruden, Douglas M.; Lu, Xiangyi (2003-12-16). "PKD2 cation channel is required for directional sperm movement and male fertility". Current Biology. 13 (24): 2175–2178. ISSN 0960-9822. PMID 14680633. 
  7. ^ "The functions of store-operated calcium channels". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1864 (6): 900–906. 2017-06-01. doi:10.1016/j.bbamcr.2016.11.028. ISSN 0167-4889. 
  8. ^ Katz, A. M. (September 1986). "Pharmacology and mechanisms of action of calcium-channel blockers". Journal of Clinical Hypertension. 2 (3 Suppl): 28S–37S. ISSN 0748-450X. PMID 3540226. 
  9. ^ Zamponi, Gerald W.; Lory, Philippe; Perez-Reyes, Edward (July 2010). "Role of voltage-gated calcium channels in epilepsy". Pflügers Archiv. 460 (2): 395–403. doi:10.1007/s00424-009-0772-x. ISSN 0031-6768. PMC 3312315Freely accessible. PMID 20091047. 

External links[edit]