KCa1.1 | BK | Maxi-K | Calcium-activated Potassium Channel Subunit Alpha-1
Calcium- and sodium-activated Potassium channels
Today, eight human calcium-activated channels are known: KCa1.1 (also known as BK or Maxi-K), KCa2.1 (also known as SK1), KCa2.2 (also known as SK2), KCa2.3 (also known as SK3) , KCa3.1 (also known as IK or SK4), KCa4.1, KCa4.2, KCa5.1
KCa channels are made up of two different subunits, alpha and beta. The alpha subunit contains six or seven trans-membrane regions and forms homo- or heter-tetramers. The beta subunit has a regulative function and contains 2 trans-membrane regions.
This family of ion channels is, for the most part, activated by intracellular Ca2+. However, some of these channels (the KCa4 and KCa5 channels) are responsive instead to other intracellular ligands, such as Na+, Cl−, and pH. Furthermore, multiple members of family are both ligand and voltage activated.
KCa1.1 Background Information
The KCa1.1 potassium channel (aka BK channel, Slo1 or Maxi-K channel) contributes to repolarization of the membrane potential. These channels are large conductance, voltage and calcium-sensitive potassium channels which are fundamental to the control of smooth muscle tone and neuronal excitability. The channels are activated by both membrane depolarization or increase in cytosolic Ca2+ that mediates export of K+. It is also activated by the concentration of cytosolic Mg2+. The channels can be formed by 2 subunits: the pore-forming alpha subunit, which is the product of this gene, and the modulatory beta subunit. Intracellular calcium regulates the physical association between the alpha and beta subunits.
Widely expressed in all tissues, except myocytes
Controls excitability in a number of systems, such as regulation of the contraction of smooth muscle, the tuning of hair cells in the cochlea, regulation of transmitter release, and innate immunity.
Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy (PNKD3), Cerebellar Atrophy, Developmental Delay, Dyskinesia, Chorea, Absence seizures
KCa1.1 channels are pharmacological targets for the treatment of stroke.
RAB11B, beta subunits: KCNMB1, KCNMB2, KCNMB3 and KCNMB4, gamma subunits: LRRC26, LRRC38, LRRC52 and LRRC55. Beta and gamma subunits are accessory, and modulate its activity.
Tetraethylammonium (TEA), paxilline, iberiotoxin, hydrochlorothiazide, diazoxide, chlorzoxazone, cromoglicic acid, BMS 191011
Kaczmarek et al. (2017) International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 69(1):1-11
Data and Applications