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J Biol Chem. 2014 Aug 15;289(33):22749-58. doi: 10.1074/jbc.M114.589796. Epub 2014 Jun 19.

Novel Kv7.1-phosphatidylinositol 4,5-bisphosphate interaction sites uncovered by charge neutralization scanning.

Author information

1
From the Department of Biochemistry I-Cation Channel Group, the International Graduate School of Neuroscience, the Ruhr University Bochum Research School, and.
2
the IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and.
3
the Institute of Physiology, Ruhr University Bochum, 44801 Bochum, Germany.
4
the Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, 1165 Copenhagen, Denmark.
5
the International Graduate School of Neuroscience, the Ruhr University Bochum Research School, and the IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and guiscard.seebohm@ukmuenster.de.

Abstract

Kv7.1 to Kv7.5 α-subunits belong to the family of voltage-gated potassium channels (Kv). Assembled with the β-subunit KCNE1, Kv7.1 conducts the slowly activating potassium current IKs, which is one of the major currents underlying repolarization of the cardiac action potential. A known regulator of Kv7 channels is the lipid phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 increases the macroscopic current amplitude by stabilizing the open conformation of 7.1/KCNE1 channels. However, knowledge about the exact nature of the interaction is incomplete. The aim of this study was the identification of the amino acids responsible for the interaction between Kv7.1 and PIP2. We generated 13 charge neutralizing point mutations at the intracellular membrane border and characterized them electrophysiologically in complex with KCNE1 under the influence of diC8-PIP2. Electrophysiological analysis of corresponding long QT syndrome mutants suggested impaired PIP2 regulation as the cause for channel dysfunction. To clarify the underlying structural mechanism of PIP2 binding, molecular dynamics simulations of Kv7.1/KCNE1 complexes containing two PIP2 molecules in each subunit at specific sites were performed. Here, we identified a subset of nine residues participating in the interaction of PIP2 and Kv7.1/KCNE1. These residues may form at least two binding pockets per subunit, leading to the stabilization of channel conformations upon PIP2 binding.

KEYWORDS:

Electrophysiology; Heart; Molecular Modeling; Phosphatidylinositol; Phosphoinositide; Phospholipid; Potassium Channel; Structural Biology; Xenopus

PMID:
24947509
PMCID:
PMC4132781
DOI:
10.1074/jbc.M114.589796
[Indexed for MEDLINE]
Free PMC Article

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