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Direct and specific activation of human inward rectifier K+ channels by membrane phosphatidylinositol 4,5-bisphosphate

Direct and specific activation of human inward rectifier K+ channels by membrane phosphatidylinositol 4,5-bisphosphate
Direct and specific activation of human inward rectifier K+ channels by membrane phosphatidylinositol 4,5-bisphosphate
Many ion channels are modulated by phosphatidylinositol 4,5-bisphosphate (PIP(2)), but studies examining the PIP(2) dependence of channel activity have been limited to cell expression systems, which present difficulties for controlling membrane composition. We have characterized the PIP(2) dependence of purified human Kir2.1 and Kir2.2 activity using (86)Rb(+) flux and patch clamp assays in liposomes of defined composition. We definitively show that these channels are directly activated by PIP(2) and that PIP(2) is absolutely required in the membrane for channel activity. The results provide the first quantitative description of the dependence of eukaryotic Kir channel function on PIP(2) levels in the membrane; Kir2.1 shows measureable activity in as little as 0.01% PIP(2), and open probability increases to ?0.4 at 1% PIP(2). Activation of Kir2.1 by phosphatidylinositol phosphates is also highly selective for PIP(2); PI, PI(4)P, and PI(5)P do not activate channels, and PI(3,4,5)P(3) causes minimal activity. The PIP(2) dependence of eukaryotic Kir activity is almost exactly opposite that of KirBac1.1, which shows marked inhibition by PIP(2). This raises the interesting hypothesis that PIP(2) activation of eukaryotic channels reflects an evolutionary adaptation of the channel to the appearance of PIP(2) in the eukaryotic cell membrane.
0021-9258
37129-37132
D'Avanzo, Nazzareno
0af1c4a7-ffe0-44d9-90cc-caa53591750f
Cheng, Wayland W.L.
160e9e4c-b341-4da9-b4f2-3be8d456dd3e
Doyle, Declan A.
f85f52c8-ce43-4f15-bd06-1df106f73b26
Nichols, Colin G.
042f1de5-f614-4b02-83fb-0b56b7f62e4d
D'Avanzo, Nazzareno
0af1c4a7-ffe0-44d9-90cc-caa53591750f
Cheng, Wayland W.L.
160e9e4c-b341-4da9-b4f2-3be8d456dd3e
Doyle, Declan A.
f85f52c8-ce43-4f15-bd06-1df106f73b26
Nichols, Colin G.
042f1de5-f614-4b02-83fb-0b56b7f62e4d

D'Avanzo, Nazzareno, Cheng, Wayland W.L., Doyle, Declan A. and Nichols, Colin G. (2010) Direct and specific activation of human inward rectifier K+ channels by membrane phosphatidylinositol 4,5-bisphosphate. The Journal of Biological Chemistry, 285 (48), 37129-37132. (doi:10.1074/jbc.C110.186692). (PMID:20921230)

Record type: Article

Abstract

Many ion channels are modulated by phosphatidylinositol 4,5-bisphosphate (PIP(2)), but studies examining the PIP(2) dependence of channel activity have been limited to cell expression systems, which present difficulties for controlling membrane composition. We have characterized the PIP(2) dependence of purified human Kir2.1 and Kir2.2 activity using (86)Rb(+) flux and patch clamp assays in liposomes of defined composition. We definitively show that these channels are directly activated by PIP(2) and that PIP(2) is absolutely required in the membrane for channel activity. The results provide the first quantitative description of the dependence of eukaryotic Kir channel function on PIP(2) levels in the membrane; Kir2.1 shows measureable activity in as little as 0.01% PIP(2), and open probability increases to ?0.4 at 1% PIP(2). Activation of Kir2.1 by phosphatidylinositol phosphates is also highly selective for PIP(2); PI, PI(4)P, and PI(5)P do not activate channels, and PI(3,4,5)P(3) causes minimal activity. The PIP(2) dependence of eukaryotic Kir activity is almost exactly opposite that of KirBac1.1, which shows marked inhibition by PIP(2). This raises the interesting hypothesis that PIP(2) activation of eukaryotic channels reflects an evolutionary adaptation of the channel to the appearance of PIP(2) in the eukaryotic cell membrane.

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Direct_and_Specific_Activation_of_Human_Inward_Rectifier_K+_Channels_by_Membrane_Phosphatidylinositol_4,5-Bisphosphate.mht - Version of Record
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e-pub ahead of print date: 4 October 2010
Published date: 26 November 2010
Organisations: Centre for Biological Sciences

Identifiers

Local EPrints ID: 342293
URI: http://eprints.soton.ac.uk/id/eprint/342293
ISSN: 0021-9258
PURE UUID: bca27a5e-1a82-4fc8-9b9f-5e465fb6a64f

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Date deposited: 20 Aug 2012 14:10
Last modified: 19 Jul 2019 21:54

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Contributors

Author: Nazzareno D'Avanzo
Author: Wayland W.L. Cheng
Author: Declan A. Doyle
Author: Colin G. Nichols

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