title: Inhibition of Kir2.1 (KCNJ2) by the AMP-activated protein kinase.
abstract: The inward rectifier K(+) channel Kir2.1 participates in the maintenance of the cell membrane potential in a variety of cells including neurons and cardiac myocytes. Mutations of KCNJ2 encoding Kir2.1 underlie the Andersen-Tawil syndrome, a rare disorder clinically characterized by periodic paralysis, cardiac arrhythmia and skeletal abnormalities. The maintenance of the cardiac cell membrane potential is decreased in ischaemia, which is known to stimulate the AMP-activated serine/threonine protein kinase (AMPK). This energy-sensing kinase stimulates energy production and limits energy utilization. The present study explored whether AMPK regulates Kir2.1. To this end, cRNA encoding Kir2.1 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. Kir2.1 activity was determined in two-electrode voltage-clamp experiments. Moreover, Kir2.1 protein abundance in the cell membrane was determined by immunostaining and subsequent confocal imaging. As a result, wild type and constitutively active AMPK significantly reduced Kir2.1-mediated currents and Kir2.1 protein abundance in the cell membrane. Expression of wild type Nedd4-2 or of Nedd4-2(S795A) lacking an AMPK phosphorylation consensus sequence downregulated Kir2.1 currents. The effect of wild type Nedd4-2 but not of Nedd4-2(S795A) was significantly augmented by additional coexpression of AMPK. In conclusion, AMPK is a potent regulator of Kir2.1. AMPK is at least partially effective through phosphorylation of the ubiquitin ligase Nedd4-2.
authors.affiliation: Department of Physiology, University of Tübingen, Gmelinstrasse 5, Tübingen, Germany.
authors.forename: Ioana
authors.initials: I
authors.lastname: Alesutan
authors.forename: Carlos
authors.initials: C
authors.lastname: Munoz
authors.forename: Mentor
authors.initials: M
authors.lastname: Sopjani
authors.forename: Miribane
authors.initials: M
authors.lastname: Dërmaku-Sopjani
authors.forename: Diana
authors.initials: D
authors.lastname: Michael
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: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015536:Down-Regulation; D006801:Humans; D009154:Mutation; D009865:Oocytes; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors*; D014981:Xenopus
chemical_list: C489457:KCNJ2 protein, human; D024661:Potassium Channels, Inwardly Rectifying; D055372:AMP-Activated Protein Kinases