KCa and Ca2 + Channels: The complex thought

Potassium channels belong to the largest and the most diverse super-families of ion channels. Among them, Ca2 +-activated K+ channels (KCa) comprise many members. Based on their single channel conductance they are divided into three subfamilies: big conductance (BKCa), intermediate conductance (IKCa) and small conductance (SKCa; SK1, SK2 and SK3). Ca2 + channels are divided into two main families, voltage gated/voltage dependent Ca2 + channels and non-voltage gated/voltage independent Ca2 + channels. Based on their electrophysiological and pharmacological properties and on the tissue where there are expressed, voltage gated Ca2 + channels (Cav) are divided into 5 families: T-type, L-type, N-type, P/Q-type and R-type Ca2 +. Non-voltage gated Ca2 + channels comprise the TRP (TRPC, TRPV, TRPM, TRPA, TRPP, TRPML and TRPN) and Orai (Orai1 to Orai 3) families and their partners STIM (STIM1 to STIM2). A depolarization is needed to activate voltage-gated Ca2 + channels while non-voltage gated Ca2 + channels are activated by Ca2 + depletion of the endoplasmic reticulum stores (SOCs) or by receptors (ROCs). These two Ca2 + channel families also control constitutive Ca2 + entries. For reducing the energy consumption and for the fine regulation of Ca2 +, KCa and Ca2 + channels appear associated as complexes in excitable and non-excitable cells. Interestingly, there is now evidence that KCa - Ca2 + channel complexes are also found in cancer cells and contribute to cancer-associated functions such as cell proliferation, cell migration and the capacity to develop metastases. This article is part of a Special Issue entitled: Calcium Signaling In Health and Disease.
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