title: Translocation of connexin 43 to the inner mitochondrial membrane of cardiomyocytes through the heat shock protein 90-dependent TOM pathway and its importance for cardioprotection.
abstract: We have previously shown that connexin 43 (Cx43) is present in mitochondria, that its genetic depletion abolishes the protection of ischemia- and diazoxide-induced preconditioning, and that it is involved in reactive oxygen species (ROS) formation in response to diazoxide. Here we investigated the intramitochondrial localization of Cx43, the mechanism of Cx43 translocation to mitochondria and the effect of inhibiting translocation on the protection of preconditioning. Confocal microscopy of mitochondria devoid of the outer membrane and Western blotting on fractionated mitochondria showed that Cx43 is located at the inner mitochondrial membrane, and coimmunoprecipitation of Cx43 with Tom20 (Translocase of the outer membrane 20) and with heat shock protein 90 (Hsp90) indicated that it interacts with the regular mitochondrial protein import machinery. In isolated rat hearts, geldanamycin, a blocker of Hsp90-dependent translocation of proteins to the inner mitochondrial membrane through the TOM pathway, rapidly (15 minutes) reduced mitochondrial Cx43 content by approximately one-third in the absence or presence of diazoxide. Geldanamycin alone had no effect on infarct size, but it ablated the protection against infarction afforded by diazoxide. Geldanamycin abolished the 2-fold increase in mitochondrial Cx43 induced by 2 preconditioning cycles of ischemia/reperfusion, but this effect was not associated with reduced protection. These results demonstrate that Cx43 is transported to the inner mitochondrial membrane through translocation via the TOM complex and that a normal mitochondrial Cx43 content is important for the diazoxide-related pathway of preconditioning.
authors.affiliation: Servicio de Cardiología, Hospital Vall d'Hebron, Barcelona, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Rodriguez-Sinovas
authors.forename: Kerstin
authors.initials: K
authors.lastname: Boengler
authors.forename: Alberto
authors.initials: A
authors.lastname: Cabestrero
authors.forename: Petra
authors.initials: P
authors.lastname: Gres
authors.forename: Miriam
authors.initials: M
authors.lastname: Morente
authors.forename: Marisol
authors.initials: M
authors.lastname: Ruiz-Meana
authors.forename: Ina
authors.initials: I
authors.lastname: Konietzka
authors.forename: Elisabet
authors.initials: E
authors.lastname: Miró
authors.forename: Andreas
authors.initials: A
authors.lastname: Totzeck
authors.forename: Gerd
authors.initials: G
authors.lastname: Heusch
authors.forename: Rainer
authors.initials: R
authors.lastname: Schulz
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Dorado
mesh_terms: D000818:Animals; D016227:Benzoquinones; D001692:Biological Transport / Q000502:physiology; D002316:Cardiotonic Agents / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D018031:Connexin 43 / Q000378:metabolism*; D003981:Diazoxide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology*; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D047029:Lactams, Macrocyclic; D008297:Male; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine; D014018:Tissue Distribution
chemical_list: D016227:Benzoquinones; D002316:Cardiotonic Agents; D002352:Carrier Proteins; D018031:Connexin 43; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011809:Quinones; D003981:Diazoxide; C001277:geldanamycin