title: Interaction between connexin 43 and nitric oxide synthase in mice heart mitochondria.
abstract: Connexin 43 (Cx43), which is highly expressed in the heart and especially in cardiomyocytes, interferes with the expression of nitric oxide synthase (NOS) isoforms. Conversely, Cx43 gene expression is down-regulated by nitric oxide derived from the inducible NOS. Thus, a complex interplay between Cx43 and NOS expression appears to exist. As cardiac mitochondria are supposed to contain a NOS, we now investigated the expression of NOS isoforms and the nitric oxide production rate in isolated mitochondria of wild-type and Cx43-deficient (Cx43(Cre-ER(T)/fl) ) mice hearts. Mitochondria were isolated from hearts using differential centrifugation and purified via Percoll gradient ultracentrifugation. Isolated mitochondria were stained with an antibody against the mitochondrial marker protein adenine-nucleotide-translocator (ANT) in combination with either a neuronal NOS (nNOS) or an inducible NOS (iNOS) antibody and analysed using confocal laser scanning microscopy. The nitric oxide formation was quantified in purified mitochondria using the oxyhaemoglobin assay. Co-localization of predominantly nNOS (nNOS: 93 ± 4.1%; iNOS: 24.6 ± 7.5%) with ANT was detected in isolated mitochondria of wild-type mice. In contrast, iNOS expression was increased in Cx43(Cre-ER(T)/fl) mitochondria (iNOS: 90.7 ± 3.2%; nNOS: 53.8 ± 17.5%). The mitochondrial nitric oxide formation was reduced in Cx43(Cre-ER(T)/fl) mitochondria (0.14 ± 0.02 nmol/min./mg protein) in comparison to wild-type mitochondria (0.24 ± 0.02 nmol/min./mg). These are the first data demonstrating, that a reduced mitochondrial Cx43 content is associated with a switch of the mitochondrial NOS isoform and the respective mitochondrial rate of nitric oxide formation.
authors: Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany; Institute for Pathophysiology, West German Heart and Vascular Center, University Schhool of Medicine Essen, Essen, Germany.
authors: Mücella
authors: M
authors: Kirca
authors: Petra
authors: P
authors: Kleinbongard
authors: Daniel
authors: D
authors: Soetkamp
authors: Jacqueline
authors: J
authors: Heger
authors: Csaba
authors: C
authors: Csonka
authors: Péter
authors: P
authors: Ferdinandy
authors: Rainer
authors: R
authors: Schulz
mesh_terms: D033741:Adenine Nucleotide Translocator 1 / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D033741:Adenine Nucleotide Translocator 1; D018031:Connexin 43; C543076:GJA1 protein, mouse; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II
keywords: connexin; heart; mitochondria; nitric oxide