A calcium channel is an ion channel which shows selective permeability to calcium ions. It is sometimes synonymous with voltage-gated calcium channel, although there are also ligand-gated calcium channels.
The following tables explain gating, gene, location and function of different types of calcium channels, both voltage and ligand-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)
|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)
|neurons, cells that have pacemaker activity, bone (osteocytes), thalamus (thalamus)|
|IP3 receptor||IP3||ITPR1, ITPR2, ITPR3||ER/SR||Releases calcium from ER/SR in response to IP3 by e.g. GPCRs|
|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|
|Two-pore channel||Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP)||TPCN1, TPCN2||endosomal/lysosomal membranes||NAADP-activated calcium transport across endosomal/lysosomal membranes|
|Cation channels of sperm||Calcium (CICR)||PKD2 family||sperm (specifically flagella)||non-selective calcium-activated cation channel directing sperm in female reproductive tract|
|store-operated channels||indirectly by ER/SR depletion of calcium||ORAI1, ORAI2, ORAI3||plasma membrane||provide calcium signaling to the cytoplasm|
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.
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.