Connexin43 in cardiomyocyte mitochondria contributes to mitochondrial potassium uptake

• Published in: Cardiovascular research Vol. 83; no. 4; pp. 747 - 756
• Main Authors: Miro-Casas, Elisabet, Ruiz-Meana, Marisol, Agullo, Esperanza, Stahlhofen, Sabine, Rodrı́guez-Sinovas, Antonio, Cabestrero, Alberto, Jorge, Inmaculada, Torre, Iratxe, Vazquez, Jesus, Boengler, Kerstin, Schulz, Rainer, Heusch, Gerd, Garcia-Dorado, David
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.09.2009
• Subjects: Animals; Biological and medical sciences; Cardiology. Vascular system; Connexin 43 - chemistry; Connexin 43 - deficiency; Connexin 43 - genetics; Connexin 43 - metabolism; Connexins; Connexins - genetics; Connexins - metabolism; Coronary heart disease; Gap Junction beta-1 Protein; Gap Junctions - metabolism; Heart; Hemichannels; In Vitro Techniques; Ion Transport; Male; Medical sciences; Membrane Potential, Mitochondrial; Mice; Mice, Knockout; Mice, Transgenic; Mitochondria, Heart - metabolism; Myocardial ischaemia; Myocarditis. Cardiomyopathies; Myocytes, Cardiac - metabolism; Oxygen Consumption; Potassium - metabolism; Preconditioning; Protein Structure, Quaternary; Rats; Rats, Sprague-Dawley; Reperfusion; Tandem Mass Spectrometry; Myocardial ischaemia; Hemichannels; Connexins; Reperfusion; Preconditioning; Heart; Cardiovascular disease; Myocardial ischemia; Coronary heart disease; Myocardial disease; Phlebology; Uptake; Myocyte; Vascular disease; Connexin; Mitochondria; Circulatory system; Cardiology; Potassium
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1093/cvr/cvp157

Aims Connexin43 is present at the inner membrane of cardiomyocyte mitochondria (mCx43), but its function remains unknown. Methods and 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dye uptake and K+ flux was assessed in wild-type mice using hemichannel blockers and Cx43KI32 mice in which Cx43 had been replaced by Cx32.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 18α-glycyrrhetinic acid had an inhibitory effect on mitochondrial K+ influx in wild-type cardiomyocytes, but not in cardiomyocytes from Cx32 mutants. Conclusion These results indicate that mCx43 contributes to mitochondrial K+ flux in cardiomyocytes, potentially by forming hemichannel-like structures.