title: Role of connexin-43 in protective PI3K-Akt-GSK-3β signaling in cardiomyocytes.
abstract: Sarcolemmal connexin-43 (Cx43) and mitochondrial Cx43 play distinct roles: formation of gap junctions and production of reactive oxygen species (ROS) for redox signaling. In this study, we examined the hypothesis that Cx43 contributes to activation of a major cytoprotective signal pathway, phosphoinositide 3-kinase (PI3K)-Akt-glycogen synthase kinase-3β (GSK-3β) signaling, in cardiomyocytes. A δ-opioid receptor agonist {[d-Ala(2),d-Leu(5)]enkephalin acetate (DADLE)}, endothelin-1 (ET-1), and insulin-like growth factor-1 (IGF-1) induced phosphorylation of Akt and GSK-3β in H9c2 cardiomyocytes. Reduction of Cx43 protein to 20% of the normal level by Cx43 small interfering RNA abolished phosphorylation of Akt and GSK-3β induced by DADLE or ET-1 but not that induced by IGF-1. DADLE and IGF-1 protected H9c2 cells from necrosis after treatment with H(2)O(2) or antimycin A. The protection by DADLE or ET-1, but not that by IGF-1, was lost by reduction of Cx43 protein expression. In contrast to Akt and GSK-3β, PKC-ε, ERK and p38 mitogen-activated protein kinase were phosphorylated by ET-1 in Cx43-knocked-down cells. Like diazoxide, an activator of the mitochondrial ATP-sensitive K(+) channel, DADLE and ET-1 induced significant ROS production in mitochondria, although such an effect was not observed for IGF-1. Cx43 knockdown did not attenuate the mitochondrial ROS production by DADLE or ET-1. Cx43 was coimmunoprecipitated with the β-subunit of G protein (Gβ), and knockdown of Gβ mimicked the effect of Cx43 knockdown on ET-1-induced phosphorylation of Akt and GSK-3β. These results suggest that Cx43 contributes to activation of class I(B) PI3K in PI3K-Akt-GSK-3β signaling possibly as a cofactor of Gβ in cardiomyocytes.
authors.affiliation: Division of Cardiology, Second Department of Internal Medicine, Sapporo Medical University, School of Medicine, Sapporo, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kuno
authors.forename: Masaya
authors.initials: M
authors.lastname: Tanno
authors.forename: Takayuki
authors.initials: T
authors.lastname: Miki
authors.forename: Hidemichi
authors.initials: H
authors.lastname: Kouzu
authors.forename: Takahito
authors.initials: T
authors.lastname: Itoh
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sato
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sunaga
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Murase
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Miura
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism*; D019610:Cytoprotection / Q000502:physiology; D019332:Endothelin-1 / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D017629:Gap Junctions / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D000701:Analgesics, Opioid; D018031:Connexin 43; D019332:Endothelin-1; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016308:Enkephalin, Leucine-2-Alanine; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3