TY - JOUR

T1 - AMP-activated protein kinase downregulates Kv7.1 cell surface expression

AU - Andersen, Martin N

AU - Krzystanek, Katarzyna

AU - Jespersen, Thomas

AU - Olesen, Søren-Peter

AU - Rasmussen, Hanne Borger

N1 - © 2011 John Wiley & Sons A/S.

PY - 2012

Y1 - 2012

N2 - The potassium channel Kv7.1 is expressed in the heart, where it contributes to the repolarization of the cardiac action potential. Additionally, Kv7.1 is expressed in epithelial tissues playing a role in salt and water transport. We recently demonstrated that surface-expressed Kv7.1 is internalized in response to polarization of the epithelial Madin-Darby canine kidney (MDCK) cell line and that this was mediated by activation of protein kinase C (PKC). In this study, the pathway downstream of PKC, which leads to internalization of Kv7.1 upon cell polarization, is elucidated. We show by confocal microscopy that Kv7.1 is endocytosed upon initiation of the polarization process and sent for degradation by the lysosomal pathway. The internalization could be mimicked by pharmacological activation of the AMP-activated protein kinase (AMPK) using three different AMPK activators. We demonstrate that the downstream effector of AMPK is the E3 ubiquitin ligase Nedd4-2. Additionally, we show that AMPK activation results in a downregulation of Kv7.1 currents in Xenopus oocytes through a Nedd4-2-dependent mechanism. In summary, surface-expressed Kv7.1 channels are endocytosed and sent for degradation in lysosomes by an AMPK-mediated activation of Nedd4-2 during the initial phase of the MDCK cell polarization process.

AB - The potassium channel Kv7.1 is expressed in the heart, where it contributes to the repolarization of the cardiac action potential. Additionally, Kv7.1 is expressed in epithelial tissues playing a role in salt and water transport. We recently demonstrated that surface-expressed Kv7.1 is internalized in response to polarization of the epithelial Madin-Darby canine kidney (MDCK) cell line and that this was mediated by activation of protein kinase C (PKC). In this study, the pathway downstream of PKC, which leads to internalization of Kv7.1 upon cell polarization, is elucidated. We show by confocal microscopy that Kv7.1 is endocytosed upon initiation of the polarization process and sent for degradation by the lysosomal pathway. The internalization could be mimicked by pharmacological activation of the AMP-activated protein kinase (AMPK) using three different AMPK activators. We demonstrate that the downstream effector of AMPK is the E3 ubiquitin ligase Nedd4-2. Additionally, we show that AMPK activation results in a downregulation of Kv7.1 currents in Xenopus oocytes through a Nedd4-2-dependent mechanism. In summary, surface-expressed Kv7.1 channels are endocytosed and sent for degradation in lysosomes by an AMPK-mediated activation of Nedd4-2 during the initial phase of the MDCK cell polarization process.

KW - AMP-Activated Protein Kinases

KW - Action Potentials

KW - Animals

KW - Blotting, Western

KW - Calcium

KW - Cell Line

KW - Cell Polarity

KW - Dogs

KW - Down-Regulation

KW - Endocytosis

KW - Endosomal Sorting Complexes Required for Transport

KW - Fluorescent Antibody Technique

KW - Humans

KW - KCNQ1 Potassium Channel

KW - Lysosomes

KW - Microscopy, Confocal

KW - Oocytes

KW - Protein Kinase C

KW - Protein Transport

KW - Transfection

KW - Ubiquitin-Protein Ligases

KW - Xenopus laevis

U2 - 10.1111/j.1600-0854.2011.01295.x

DO - 10.1111/j.1600-0854.2011.01295.x

M3 - Journal article

C2 - 21957902

VL - 13

SP - 143

EP - 156

JO - Traffic

JF - Traffic

SN - 1398-9219

IS - 1

ER -