Trafficking of the IKs-Complex in MDCK Cells: Site of Subunit Assembly and Determinants of Polarized Localization

Authors

  • Jens-Peter David,

    1. The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author
  • Martin N. Andersen,

    1. The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author
  • Søren-Peter Olesen,

    1. The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author
  • Hanne B. Rasmussen,

    Corresponding author
    • The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author
    • These authors contributed equally to this work.

  • Nicole Schmitt

    1. The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author
    • These authors contributed equally to this work.


Corresponding author: Hanne B. Rasmussen, hannebr@sund.ku.dk

Abstract

The voltage-gated potassium channel KV7.1 is regulated by non-pore forming regulatory KCNE β-subunits. Together with KCNE1, it forms the slowly activating delayed rectifier potassium current IKs. However, where the subunits assemble and which of the subunits determines localization of the IKs-complex has not been unequivocally resolved yet. We employed trafficking-deficient KV7.1 and KCNE1 mutants to investigate IKs trafficking using the polarized Madin-Darby Canine Kidney cell line. We find that the assembly happens early in the secretory pathway but provide three lines of evidence that it takes place in a post-endoplasmic reticulum compartment. We demonstrate that KV7.1 targets the IKs-complex to the basolateral membrane, but that KCNE1 can redirect the complex to the apical membrane upon mutation of critical KV7.1 basolateral targeting signals. Our data provide a possible explanation to the fact that KV7.1 can be localized apically or basolaterally in different epithelial tissues and offer a solution to divergent literature results regarding the effect of KCNE subunits on the subcellular localization of KV7.1/KCNE complexes.

Ancillary