Browse by author
Lookup NU author(s): Dr Seva TelezhkinORCiD
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).
M-channels are voltage-gated potassium channels that regulate cell excitability. They are heterotetrameric assemblies of Kv7.2 and Kv7.3 subunits. Their opening requires the presence of the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)). However, the specificity of PI(4,5)P(2) as a binding and activating ligand is unknown. Here, we tested the ability of different phosphoinositides and lipid phosphates to activate or bind to M-channel proteins. Activation of functional channels was measured in membrane patches isolated from cells coexpressing Kv7.2 and Kv7.3 subunits. Channels were activated to similar extents (maximum open probability of ∼0.8 at 0 mV) by 0.1-300 μM dioctanoyl homologs of the three endogenous phosphoinositides, PI(4)P, PI(4,5)P(2), and PI(3,4,5)P(3), with sensitivity increasing with increasing numbers of phosphates. Non-acylated inositol phosphates had no effect up to 100 μM. Channels were also activated with increasing efficacy by 1-300 μM concentrations of the monoacyl monophosphates fingolimod phosphate, sphingosine 1-phosphate, and lysophosphatidic acid but not by phosphate-free fingolimod or sphingosine or by phosphate-masked phosphatidylcholine or phosphatidylglycerol. An overlay assay confirmed that a fusion protein containing the full-length C terminus of Kv7.2 could bind to a broad range of phosphoinositides and phospholipids. A mutated Kv7.2 C-terminal construct with reduced sensitivity to PI(4,5)P showed significantly less binding to most polyphosphoinositides. We concluded that M-channels bind to, and are activated by, a wide range of lipid phosphates, with a minimum requirement for an acyl chain and a phosphate headgroup. In this, they more closely resemble inwardly rectifying Kir6.2 potassium channels than the more PI(4,5)P(2)-specific Kir2 channels. Notwithstanding, the data also support the view that the main endogenous activator of M-channels is PI(4,5)P(2).
Author(s): Telezhkin V, Reilly JM, Thomas AM, Tinker A, Brown DA
Publication type: Article
Publication status: Published
Journal: The Journal of Biological Chemistry
Year: 2012
Volume: 287
Issue: 13
Pages: 10001-10012
Print publication date: 23/03/2012
Online publication date: 01/02/2012
Date deposited: 09/03/2017
ISSN (print): 0021-9258
ISSN (electronic): 1083-351X
Publisher: American Society for Biochemistry and Molecular Biology, Inc.
URL: http://dx.doi.org/10.1074/jbc.M111.322552
DOI: 10.1074/jbc.M111.322552
PubMed id: 22303005
Altmetrics provided by Altmetric
