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Endogenous KCNE subunits govern Kv2.1 K+ channel activation kinetics in Xenopus oocyte studies

Item Type:Article
Title:Endogenous KCNE subunits govern Kv2.1 K+ channel activation kinetics in Xenopus oocyte studies
Creators Name:Gordon, E. and Roepke, T.K. and Abbott, G.W.
Abstract:Kv2.1 is a voltage-gated potassium (Kv) channel that generates delayed rectifier currents in mammalian heart and brain. The biophysical properties of Kv2.1 and other ion channels have been characterized by functional expression in heterologous systems, and most commonly in Xenopus laevis oocytes. A number of previous oocyte-based studies of mammalian potassium channels have revealed expression-level-dependent changes in channel properties, leading to the suggestion that endogenous oocyte factors regulate channel gating. Here, we show that endogenous oocyte potassium channel KCNE ancillary subunits xMinK and xMiRP2 slow the activation of oocyte-expressed mammalian Kv2.1 channels two-to-fourfold. This produces a sigmoidal relationship between Kv2.1 current density and activation rate in oocyte-based two-electrode voltage clamp studies. The effect of endogenous xMiRP2 and xMinK on Kv2.1 activation is diluted at high Kv2.1 expression levels, or by RNAi knockdown of either endogenous subunit. RNAi knockdown of both xMiRP2 and xMinK eliminates the correlation between Kv2.1 expression level and activation kinetics. The data demonstrate a molecular basis for expression-level-dependent changes in Kv channel gating observed in heterologous expression studies.
Keywords:Ion Channel Gating, Kinetics, Molecular Cloning , Oocytes, Patch-Clamp Techniques, Protein Subunits, Small Interfering RNA, Shab Potassium Channels, Voltage-Gated Potassium Channels, Xenopus Proteins, Animals, Rats, Xenopus Laevis
Source:Biophysical Journal
Publisher:Biophysical Society
Page Range:1223-1231
Date:15 February 2006
Official Publication:https://doi.org/10.1529/biophysj.105.072504
PubMed:View item in PubMed

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