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Ca2+-Calmodulin and PIP2 interactions at the proximal C-terminus of Kv7 channels

William S Tobelaim1, Meidan Dvir1, Guy Lebel2

  • 1a Department of Physiology & Pharmacology , Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel.

Channels (Austin, Tex.)
|October 5, 2017
PubMed

Insights

Phosphatidylinositol-4,5-bisphosphate (PIP2) and calcium-bound calmodulin (Ca2+-CaM) stabilize the IKS potassium channel open state by competing for binding sites on Kv7.1 helix B, impacting cardiac function.

Area of Science:

  • Biophysics
  • Molecular Biology
  • Cardiology

Background:

  • The slow IKS potassium current, generated by Kv7.1/KCNE1 co-assembly, is crucial for cardiac action potential repolarization.
  • Mutations in Kv7.1 and KCNE1 genes are linked to cardiac arrhythmias.
  • Kv7.1 C-terminus binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2).

Purpose of the Study:

  • To investigate the functional interaction between PIP2 and Ca2+-CaM at the Kv7.1 helix B binding site.
  • To determine if PIP2 and Ca2+-CaM share functional roles in modulating Kv7.1 channel gating.
  • To explore the conservation and functional relevance of these interactions in other Kv7 subtypes.

Main Methods:

  • Electrophysiological recordings of Kv7.1 currents, both alone and with KCNE1.
  • Site-directed mutagenesis to probe interactions at the Kv7.1 helix B.
  • Comparative analysis of homologous Kv7 subtypes.

Main Results:

  • PIP2 competes with the N-lobe of Ca2+-CaM for binding to a site on Kv7.1 helix B.
  • Both PIP2 and Ca2+-CaM stabilize the Kv7.1 channel open state, suggesting a shared functional role.
  • These competitive binding and functional features are conserved in other Kv7 subtypes, indicating a common regulatory mechanism.

Conclusions:

  • PIP2 and Ca2+-CaM interactions converge on Kv7 helix B to regulate channel gating.
  • This regulation is Kv7 subtype-dependent, highlighting the specificity of PIP2-CaM modulation.
  • Understanding these interactions provides insights into cardiac electrophysiology and potential therapeutic targets for arrhythmias.
Keywords:
KCNQKv7PIP2Potassium channelcalmodulin

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