Connexin43 in cardiomyocyte mitochondria contributes to mitochondrial potassium uptake

Abstract

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dye uptake and K + flux was assessed in wild-type mice using hemichannel blockers and Cx43KI32 mice in which Cx43 had been replaced by Cx32.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. © The Author 2009.