title: Inhibition of the heterotetrameric K+ channel KCNQ1/KCNE1 by the AMP-activated protein kinase.
abstract: The heterotetrameric K(+)-channel KCNQ1/KCNE1 is expressed in heart, skeletal muscle, liver and several epithelia including the renal proximal tubule. In the heart, it contributes to the repolarization of cardiomyocytes. The repolarization is impaired in ischemia. Ischemia stimulates the AMP-activated protein kinase (AMPK), a serine/threonine kinase, sensing energy depletion and stimulating several cellular mechanisms to enhance energy production and to limit energy utilization. AMPK has previously been shown to downregulate the epithelial Na(+) channel ENaC, an effect mediated by the ubiquitin ligase Nedd4-2. The present study explored whether AMPK regulates KCNQ1/KCNE1. To this end, cRNA encoding KCNQ1/KCNE1 was injected into Xenopus oocytes with and without additional injection of wild type AMPK (AMPKα1 + AMPKβ1 + AMPKγ1), of the constitutively active (γR70Q)AMPK (α1β1γ1(R70Q)), of the kinase dead mutant (αK45R)AMPK (α1(K45R)β1γ1), or of the ubiquitin ligase Nedd4-2. KCNQ1/KCNE1 activity was determined in two electrode voltage clamp experiments. Moreover, KCNQ1 abundance in the cell membrane was determined by immunostaining and subsequent confocal imaging. As a result, wild type and constitutively active AMPK significantly reduced KCNQ1/KCNE1-mediated currents and reduced KCNQ1 abundance in the cell membrane. Similarly, Nedd4-2 decreased KCNQ1/KCNE1-mediated currents and KCNQ1 protein abundance in the cell membrane. Activation of AMPK in isolated perfused proximal renal tubules by AICAR (10 mM) was followed by significant depolarization. In conclusion, AMPK is a potent regulator of KCNQ1/KCNE1.
authors.affiliation: Department of Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Ioana
authors.initials: I
authors.lastname: Alesutan
authors.forename: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Mentor
authors.initials: M
authors.lastname: Sopjani
authors.forename: Miribane
authors.initials: M
authors.lastname: Dërmaku-Sopjani
authors.forename: Christine
authors.initials: C
authors.lastname: Zelenak
authors.forename: Henning
authors.initials: H
authors.lastname: Fröhlich
authors.forename: Ana
authors.initials: A
authors.lastname: Velic
authors.forename: Scott
authors.initials: S
authors.lastname: Fraser
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Kemp
authors.forename: Guiscard
authors.initials: G
authors.lastname: Seebohm
authors.forename: Harald
authors.initials: H
authors.lastname: Völkl
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D015640:Ion Channel Gating; D051657:KCNQ1 Potassium Channel / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D018613:Microscopy, Confocal; D016297:Mutagenesis, Site-Directed; D000075702:Nedd4 Ubiquitin Protein Ligases; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018075:RNA, Complementary; D012265:Ribonucleotides / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; C489622:KCNE1 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D018075:RNA, Complementary; D012265:Ribonucleotides; D029867:Xenopus Proteins; D000620:Aminoimidazole Carboxamide; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; C000618460:nedd4l protein, Xenopus; D044767:Ubiquitin-Protein Ligases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide