Uncoupling PIP2-calmodulin regulation of Kv7.2 channels by an assembly destabilizing epileptogenic mutation

J Cell Sci. 2015 Nov 1;128(21):4014-23. doi: 10.1242/jcs.176420. Epub 2015 Sep 10.

Abstract

We show that the combination of an intracellular bi-partite calmodulin (CaM)-binding site and a distant assembly region affect how an ion channel is regulated by a membrane lipid. Our data reveal that regulation by phosphatidylinositol(4,5)bisphosphate (PIP2) and stabilization of assembled Kv7.2 subunits by intracellular coiled-coil regions far from the membrane are coupled molecular processes. Live-cell fluorescence energy transfer measurements and direct binding studies indicate that remote coiled-coil formation creates conditions for different CaM interaction modes, each conferring different PIP2 dependency to Kv7.2 channels. Disruption of coiled-coil formation by epilepsy-causing mutation decreases apparent CaM-binding affinity and interrupts CaM influence on PIP2 sensitivity.

Keywords: Allosteric; Calmodulin; Coiled-coil; Epilepsy; KCNQ; Leucine zipper; M-current; PIP2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calmodulin / genetics
  • Calmodulin / metabolism*
  • Cell Line
  • Humans
  • KCNQ2 Potassium Channel / genetics
  • KCNQ2 Potassium Channel / metabolism*
  • Mutation / genetics
  • Phosphatidylinositol 4,5-Diphosphate / metabolism*
  • Protein Binding

Substances

  • Calmodulin
  • KCNQ2 Potassium Channel
  • Phosphatidylinositol 4,5-Diphosphate