title: Auxiliary KCNE subunits modulate both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels.
abstract: The diversity of the voltage-gated K(+) (Kv) channel subfamily Kv2 is increased by interactions with auxiliary β-subunits and by assembly with members of the modulatory so-called silent Kv subfamilies (Kv5-Kv6 and Kv8-Kv9). However, it has not yet been investigated whether these two types of modulating subunits can associate within and modify a single channel complex simultaneously. Here, we demonstrate that the transmembrane β-subunit KCNE5 modifies the Kv2.1/Kv6.4 current extensively, whereas KCNE2 and KCNE4 only exert minor effects. Co-expression of KCNE5 with Kv2.1 and Kv6.4 did not alter the Kv2.1/Kv6.4 current density but modulated the biophysical properties significantly; KCNE5 accelerated the activation, slowed the deactivation and steepened the slope of the voltage-dependence of the Kv2.1/Kv6.4 inactivation by accelerating recovery of the closed-state inactivation. In contrast, KCNE5 reduced the current density ~2-fold without affecting the biophysical properties of Kv2.1 homotetramers. Co-localization of Kv2.1, Kv6.4 and KCNE5 was demonstrated with immunocytochemistry and formation of Kv2.1/Kv6.4/KCNE5 and Kv2.1/KCNE5 complexes was confirmed by Fluorescence Resonance Energy Transfer experiments performed in HEK293 cells. These results suggest that a triple complex consisting of Kv2.1, Kv6.4 and KCNE5 subunits can be formed. In vivo, formation of such tripartite Kv2.1/Kv6.4/KCNE5 channel complexes might contribute to tissue-specific fine-tuning of excitability.
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia and Department for Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jens-Peter
authors.initials: JP
authors.lastname: David
authors.affiliation: Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department for Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Jeroen I
authors.initials: JI
authors.lastname: Stas
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia and Department for Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Nicole
authors.initials: N
authors.lastname: Schmitt
authors.affiliation: Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department for Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Bocksteins
mesh_terms: D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials; D051379:Mice; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism* / Q000502:physiology; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000502:physiology; D021381:Protein Transport; D051669:Shab Potassium Channels / Q000378:metabolism*
chemical_list: C496988:KCNB1 protein, human; C489622:KCNE1 protein, human; C489619:KCNE2 protein, human; C418492:KCNE3 protein, human; C470587:KCNE4 protein, mouse; C502068:KCNE5 protein, human; C450424:KCNG3 protein, human; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D051669:Shab Potassium Channels