title: Regulation of cardiac ATP-sensitive potassium channel surface expression by calcium/calmodulin-dependent protein kinase II.
abstract: Cardiac ATP-sensitive potassium (K(ATP)) channels are key sensors and effectors of the metabolic status of cardiomyocytes. Alteration in their expression impacts their effectiveness in maintaining cellular energy homeostasis and resistance to injury. We sought to determine how activation of calcium/calmodulin-dependent protein kinase II (CaMKII), a central regulator of calcium signaling, translates into reduced membrane expression and current capacity of cardiac K(ATP) channels. We used real-time monitoring of K(ATP) channel current density, immunohistochemistry, and biotinylation studies in isolated hearts and cardiomyocytes from wild-type and transgenic mice as well as HEK cells expressing wild-type and mutant K(ATP) channel subunits to track the dynamics of K(ATP) channel surface expression. Results showed that activation of CaMKII triggered dynamin-dependent internalization of K(ATP) channels. This process required phosphorylation of threonine at 180 and 224 and an intact (330)YSKF(333) endocytosis motif of the K(ATP) channel Kir6.2 pore-forming subunit. A molecular model of the μ2 subunit of the endocytosis adaptor protein, AP2, complexed with Kir6.2 predicted that μ2 docks by interaction with (330)YSKF(333) and Thr-180 on one and Thr-224 on the adjacent Kir6.2 subunit. Phosphorylation of Thr-180 and Thr-224 would favor interactions with the corresponding arginine- and lysine-rich loops on μ2. We concluded that calcium-dependent activation of CaMKII results in phosphorylation of Kir6.2, which promotes endocytosis of cardiac K(ATP) channel subunits. This mechanism couples the surface expression of cardiac K(ATP) channels with calcium signaling and reveals new targets to improve cardiac energy efficiency and stress resistance.
authors.affiliation: Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Sierra
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Zhu
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sapay
authors.forename: Vikas
authors.initials: V
authors.lastname: Sharotri
authors.forename: Crystal F
authors.initials: CF
authors.lastname: Kline
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Luczak
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Subbotina
authors.forename: Asipu
authors.initials: A
authors.lastname: Sivaprasadarao
authors.forename: Peter M
authors.initials: PM
authors.lastname: Snyder
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mohler
authors.forename: Mark E
authors.initials: ME
authors.lastname: Anderson
authors.forename: Michel
authors.initials: M
authors.lastname: Vivaudou
authors.forename: Leonid V
authors.initials: LV
authors.lastname: Zingman
authors.forename: Denice M
authors.initials: DM
authors.lastname: Hodgson-Zingman
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034281:Dynamins / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D017136:Ion Transport; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D032383:Myocytes, Cardiac / Q000166:cytology / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013912:Threonine / Q000378:metabolism; D000099161:Kcnj11 Channel
chemical_list: D033962:Adaptor Protein Complex 2; D002118:Calcium; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D034281:Dynamins; D024661:Potassium Channels, Inwardly Rectifying; D013912:Threonine; D000099161:Kcnj11 Channel