Mitochondriales Connexin 43: Regulation und Funktion

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Cardiomyocyte connexin43 (Cx43) plays a causal role in the cardioprotecion by ischemia preconditioning (IP), since infarct size reduction by IP is lost in heterozygous Cx43 deficient mice hearts and isolated cardiomyocytes. Apart from Cx43 being localized at the cardiomyocyte sarcolemma, we have demonstrated that Cx43 is present in mitochondria isolated from mice, rat, pig and human LV myocardium; the Cx43 content is higher in mitochondria isolated from preconditioned than from non-preconditioned myocardium. The exact localization of Cx43 within mitochondria and the mechanisms regulating its import or degradation are unknown. Therefore, signal transduction pathways will be stimulated by ischemia/reperfusion in isolated rat hearts and cardiomyocytes in the absence or presence of specific protein kinase (A,C,G or MAP kinase) inhibitors and rnitochondrial Cx43 levels and its exact localization (outer/inner membrane or matrix) will be measured. Alternatively, protein kinases will be stimulated by specific agonists and changes in mitochondrial Cx43 content will be assessed. To determine Cx43 function in mitochondria, its complete ablation will be induced in genetically modified mice (cre/flox) by the injection of 4-hydroxytamoxifen, and mitochondrial membrane potential, respiration, swelling, opening of the permeability transition pore and radical formation will be measured before and following ischemia/reperfusion; in the latter experimental setup, infarct size will be assessed separately in in vivo hearts.