Inwardly rectifying potassium channels: their structure, function, and physiological roles.
Inwardly rectifying K(+) (Kir) channels allow K(+) to move more easily into rather than out of the cell. They have diverse physiological functions depending on their type and their location. There are seven Kir channel subfamilies that can be classified into four functional groups: classical Kir channels (Kir2.x) are constitutively active, G protein-gated Kir channels (Kir3.x) are regulated by G protein-coupled receptors, ATP-sensitive K(+) channels (Kir6.x) are tightly linked to cellular metabolism, and K(+) transport channels (Kir1.x, Kir4.x, Kir5.x, and Kir7.x). Inward rectification results from pore block by intracellular substances such as Mg(2+) and polyamines. Kir channel activity can be modulated by ions, phospholipids, and binding proteins. The basic building block of a Kir channel is made up of two transmembrane helices with cytoplasmic NH(2) and COOH termini and an extracellular loop which folds back to form the pore-lining ion selectivity filter. In vivo, functional Kir channels are composed of four such subunits which are either homo- or heterotetramers. Gene targeting and genetic analysis have linked Kir channel dysfunction to diverse pathologies. The crystal structure of different Kir channels is opening the way to understanding the structure-function relationships of this simple but diverse ion channel family.
Hibino
Hiroshi
H
Department of Pharmacology, Graduate School of Medicine and The Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan.
Inanobe
Atsushi
A
Furutani
Kazuharu
K
Murakami
Shingo
S
Findlay
Ian
I
Kurachi
Yoshihisa
Y
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000737:chemistry / Q000502:physiology; D006801:Humans; D054086:KATP Channels; D051379:Mice; D018345:Mice, Knockout; D000069437:Pharmacological Phenomena / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000502:physiology*
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D054086:KATP Channels; C489461:Kir2.1 channel; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel