title: Connexin43 in cardiomyocyte mitochondria contributes to mitochondrial potassium uptake.
abstract: OBJECTIVE
  Connexin43 is present at the inner membrane of cardiomyocyte mitochondria (mCx43), but its function remains unknown.
  
  
  RESULTS
  In this study we verified the presence of mCx43 by a mass spectrometry-based proteomic approach in purified mitochondrial preparations from mouse myocardium and determined by western blot analysis that the C-terminus of mCx43 is oriented towards the intermembrane space. Cross-linking studies with dimethylsuberimidate indicated the presence of Cx43 hexamers in mitochondrial membranes. The contribution of Cx43 to both mitochondrial dye uptake and K(+) flux was assessed in wild-type mice using hemichannel blockers and Cx43KI32 mice in which Cx43 had been replaced by Cx32. Uptake of the Cx43 hemichannel-permeant dye Lucifer Yellow was reduced in mitochondria from wild-type mice by two hemichannel blockers (carbenoxolone and heptanol) and in Cx43KI32 compared with wild-type mice. Mitochondrial K(+) influx (PBFI fluorescence) was decreased in digitonin-permeabilized cardiomyocytes from Cx32 mutants compared with wild-type mice, and addition of the Cx43 hemichannel blocker 18alpha-glycyrrhetinic acid had an inhibitory effect on mitochondrial K(+) influx in wild-type cardiomyocytes, but not in cardiomyocytes from Cx32 mutants.
  
  
  CONCLUSIONS
  These results indicate that mCx43 contributes to mitochondrial K(+) flux in cardiomyocytes, potentially by forming hemichannel-like structures.
authors.affiliation: Servicio de Cardiología, Hospital Universitari Vall d'Hebron, Pg. Vall d'Hebron 119, Barcelona 08035, Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Miro-Casas
authors.forename: Marisol
authors.initials: M
authors.lastname: Ruiz-Meana
authors.forename: Esperanza
authors.initials: E
authors.lastname: Agullo
authors.forename: Sabine
authors.initials: S
authors.lastname: Stahlhofen
authors.forename: Antonio
authors.initials: A
authors.lastname: Rodríguez-Sinovas
authors.forename: Alberto
authors.initials: A
authors.lastname: Cabestrero
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Jorge
authors.forename: Iratxe
authors.initials: I
authors.lastname: Torre
authors.forename: Jesus
authors.initials: J
authors.lastname: Vazquez
authors.forename: Kerstin
authors.initials: K
authors.lastname: Boengler
authors.forename: Rainer
authors.initials: R
authors.lastname: Schulz
authors.forename: Gerd
authors.initials: G
authors.lastname: Heusch
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Dorado
mesh_terms: D000818:Animals; D018031:Connexin 43 / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D066298:In Vitro Techniques; D017136:Ion Transport; D008297:Male; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010101:Oxygen Consumption; D011188:Potassium / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D051381:Rats; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry; D000097002:Gap Junction beta-1 Protein
chemical_list: D018031:Connexin 43; D017630:Connexins; D011188:Potassium; D000097002:Gap Junction beta-1 Protein