Requirement of subunit co-assembly and ankyrin-G for M-channel localization at the axon initial segment

Hanne B. Rasmussen*, Christian Frøkjær-Jensen, Camilla S. Jensen, Henrik S. Jensen, Nanna K. Jørgensen, Hiroaki Misonou, James S. Trimmer, Søren Peter Olesen, Nicole Schmitt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

The potassium channel subunits KCNQ2 and KCNQ3 are believed to underlie the M current of hippocampal neurons. The M-type potassium current plays a key role in the regulation of neuronal excitability; however, the subcellular location of the ion channels underlying this regulation has been controversial. We report here that KCNQ2 and KCNQ3 subunits are localized to the axon initial segment of pyramidal neurons of adult rat hippocampus and in cultured hippocampal neurons. We demonstrate that the localization of the KCNQ2/3 channel complex to the axon initial segment is favored by co-expression of the two channel subunits. Deletion of the ankyrin-G-binding motif in both the KCNQ2 and KCNQ3 C-terminals leads to the disappearance of the complex from the axon initial segment, albeit the channel complex remains functional and still reaches the plasma membrane. We further show that although heteromeric assembly of the channel complex favours localization to the axon initial segment, deletion of the ankyrin-G-binding motif in KCNQ2 alone does not alter the subcellular localization of KCNQ2/3 heteromers. By contrast, deletion of the ankyrin-G-binding motif in KCNQ3 significantly reduces AIS enrichment of the complex, implicating KCNQ3 as a major determinant of M channel localization to the AIS.

Original languageEnglish (US)
Pages (from-to)953-963
Number of pages11
JournalJournal of Cell Science
Volume120
Issue number6
DOIs
StatePublished - Mar 15 2007

Keywords

  • Ankyrin-G
  • Axon initial segment
  • Epilepsy
  • KCNQ
  • M current
  • Targeting

ASJC Scopus subject areas

  • Cell Biology

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