Phosphatidylinositol-4,5-bisphosphate is required for KCNQ1/KCNE1 channel function but not anterograde trafficking

Alice A Royal, Andrew Tinker, Stephen C Harmer

Research output: Contribution to journalArticle (Academic Journal)peer-review

3 Citations (Scopus)
161 Downloads (Pure)

Abstract

The slow delayed-rectifier potassium current (IKs) is crucial for human cardiac action potential repolarization. The formation of IKs requires co-assembly of the KCNQ1 α-subunit and KCNE1 β-subunit, and mutations in either of these subunits can lead to hereditary long QT syndrome types 1 and 5, respectively. It is widely recognised that the KCNQ1/KCNE1 (Q1/E1) channel requires phosphatidylinositol-4,5-bisphosphate (PIP2) binding for function. We previously identified a cluster of basic residues in the proximal C-terminus of KCNQ1 that form a PIP2/phosphoinositide binding site. Upon charge neutralisation of these residues we found that the channel became more retained in the endoplasmic reticulum, which raised the possibility that channel-phosphoinositide interactions could play a role in channel trafficking. To explore this further we used a chemically induced dimerization (CID) system to selectively deplete PIP2 and/or phosphatidylinositol-4-phosphate (PI(4)P) at the plasma membrane (PM) or Golgi, and we subsequently monitored the effects on both channel trafficking and function. The depletion of PIP2 and/or PI(4)P at either the PM or Golgi did not alter channel cell-surface expression levels. However, channel function was extremely sensitive to the depletion of PIP2 at the PM, which is in contrast to the response of other cardiac potassium channels tested (Kir2.1 and Kv11.1). Surprisingly, when using the CID system IKs was dramatically reduced even before dimerization was induced, highlighting limitations regarding the utility of this system when studying processes highly sensitive to PIP2 depletion. In conclusion, we identify that the Q1/E1 channel does not require PIP2 or PI(4)P for anterograde trafficking, but is heavily reliant on PIP2 for channel function once at the PM.

Original languageEnglish
Article numbere0186293
Number of pages22
JournalPLoS ONE
Volume12
Issue number10
Early online date11 Oct 2017
DOIs
Publication statusPublished - 11 Oct 2017

Keywords

  • Animals
  • CHO Cells
  • Cell Membrane/drug effects
  • Cricetinae
  • Cricetulus
  • Endoplasmic Reticulum/drug effects
  • Genes, Reporter
  • Golgi Apparatus/drug effects
  • HEK293 Cells
  • Humans
  • Ion Channel Gating/drug effects
  • KCNQ1 Potassium Channel/metabolism
  • Mutation/genetics
  • Phosphatidylinositol 4,5-Diphosphate/metabolism
  • Potassium Channels, Voltage-Gated/metabolism
  • Protein Binding/drug effects
  • Protein Multimerization/drug effects
  • Protein Transport/drug effects
  • Sirolimus/pharmacology

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