Channelpedia

Downregulation of Kv1.5 K Channels by the AMP-Activated Protein Kinase.


Authors: Sobuj Mia, Carlos Munoz, Tatsiana Pakladok, Gulab Siraskar, Jakob Voelkl, Ioana Alesutan, Florian Lang

Journal, date & volume: Cell. Physiol. Biochem., 2012 Sep 24 , 30, 1039-1050

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/23221389

Channelpedia reference in: Kv1.5

Abstract
Background: The voltage gated K(+) channel Kv1.5 participates in the repolarization of a wide variety of cell types. Kv1.5 is downregulated during hypoxia, which is known to stimulate the energy-sensing AMP-activated serine/threonine protein kinase (AMPK). AMPK is a powerful regulator of nutrient transport and metabolism. Moreover, AMPK is known to downregulate several ion channels, an effect at least in part due to stimulation of the ubiquitin ligase Nedd4- 2. The present study explored whether AMPK regulates Kv1.5. Methods: cRNA encoding Kv1.5 was injected into Xenopus oocytes with and without additional injection of wild-type AMPK (α1 β 1γ1), of constitutively active (γR70Q)AMPK (α1 β 1γ1(R70Q)), of inactive mutant (αK45R)AMPK (α1(K45R)β1γ1), or of Nedd4-2. Kv1.5 activity was determined by two-electrode voltage-clamp. Moreover, Kv1.5 protein abundance in the cell membrane was determined by chemiluminescence and immunostaining with subsequent confocal microscopy. Results: Coexpression of wild-type AMPK(WT) and constitutively active AMPK(γR70Q), but not of inactive AMPK(αK45R) significantly reduced Kv1.5-mediated currents. Coexpression of constitutively active AMPKγR70Q further reduced Kv1.5 K(+) channel protein abundance in the cell membrane. Co-expression of Nedd4-2 similarly downregulated Kv1.5-mediated currents. Conclusion: AMPK is a potent regulator of Kv1.5. AMPK inhibits Kv1.5 presumably in part by activation of Nedd4- 2 with subsequent clearance of channel protein from the cell membrane.