title: Classification of 2-pore domain potassium channels based on rectification under quasi-physiological ionic conditions.
abstract: It is generally expected that 2-pore domain K(+) (K2P) channels are open or outward rectifiers in asymmetric physiological K(+) gradients, following the Goldman-Hodgkin-Katz (GHK) current equation. Although cloned K2P channels have been extensively studied, their current-voltage (I-V) relationships are not precisely characterized and previous definitions are contradictory. Here we study all the functional channels from 6 mammalian K2P subfamilies in transfected Chinese hamster ovary cells with patch-clamp technique, and examine whether their I-V relationships are described by the GHK current equation. K2P channels display 2 distinct types of I-V curves in asymmetric physiological K(+) gradients. Two K2P isoforms in the TWIK subfamily conduct large inward K(+) currents and have a nearly linear I-V curve. Ten isoforms from 5 other K2P subfamilies conduct small inward K(+) currents and exhibit open rectification, but fits with the GHK current equation cannot precisely reveal the differences in rectification among K2P channels. The Rectification Index, a ratio of limiting I-V slopes for outward and inward currents, is used to quantitatively describe open rectification of each K2P isoform, which is previously qualitatively defined as strong or weak open rectification. These results systematically and precisely classify K2P channels and suggest that TWIK K(+) channels have a unique feature in regulating cellular function.
authors.affiliation: a Department of Biological Sciences ; University at Albany; State University of New York ; Albany , NY USA.
authors.forename: Haijun
authors.initials: H
authors.lastname: Chen
authors.forename: Dongchuan
authors.initials: D
authors.lastname: Zuo
authors.forename: Jianing
authors.initials: J
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
authors.forename: Liqun
authors.initials: L
authors.lastname: Ma
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D015640:Ion Channel Gating; D008564:Membrane Potentials; D024683:Potassium Channels, Tandem Pore Domain / Q000737:chemistry / Q000145:classification* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000145:classification / Q000378:metabolism
chemical_list: D024683:Potassium Channels, Tandem Pore Domain; D020033:Protein Isoforms