Surface expression and single channel properties of KCNQ2/KCNQ3, M-type K+ channels involved in epilepsy

J Biol Chem. 2000 May 5;275(18):13343-8. doi: 10.1074/jbc.275.18.13343.

Abstract

Mutations in either KCNQ2 or KCNQ3 underlie benign familial neonatal convulsions (BFNC), an inherited epilepsy. The corresponding proteins are co-expressed in broad regions of the brain and associate to heteromeric K(+) channels. These channels mediate M-type currents that regulate neuronal excitability. We investigated the basis for the increase in currents seen after co-expressing these subunits in Xenopus oocytes. Noise analysis and single channel recordings revealed a conductance of approximately 18 pS for KCNQ2 and approximately 7 pS for KCNQ3. Different conductance levels (ranging from 8 to 22 pS) were seen upon co-expression. Their weighted average is close to that obtained by noise analysis (16 pS). The open probability of heteromeric channels was not increased significantly. Co-expression of both subunits increased the surface expression of KCNQ2 and KCNQ3 by factors of 5 and >10, respectively. A KCNQ2 mutant associated with BFNC that has a truncated cytoplasmic carboxyl terminus did not reach the surface and failed to stimulate KCNQ3 surface expression. By contrast, several BFNC-associated missense mutations in KCNQ2 or KCNQ3 did not alter their surface expression. Thus, the increase in currents seen upon co-expressing KCNQ2 and KCNQ3 is predominantly due to an increase in surface expression, which is dependent on an intact carboxyl terminus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Epilepsy / physiopathology*
  • Gene Expression Regulation
  • Humans
  • Ion Channel Gating / genetics
  • KCNQ2 Potassium Channel
  • KCNQ3 Potassium Channel
  • Mutation
  • Patch-Clamp Techniques
  • Potassium Channels / physiology*
  • Potassium Channels, Voltage-Gated

Substances

  • KCNQ2 Potassium Channel
  • KCNQ2 protein, human
  • KCNQ3 Potassium Channel
  • KCNQ3 protein, human
  • Potassium Channels
  • Potassium Channels, Voltage-Gated

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