Copyright © 2006, European Society of Cardiology
Dual level of interactions between calcineurin and PKC-
in cardiomyocyte stretch
aUnité INSERM U400, Créteil, France
bImaging plate-forme Institut Mondor de Médecine Moléculaire Créteil, France
cUnité INSERM U689CRCIL Paris, France
* Corresponding author. Present address: Unité INSERM U769 Faculté de Pharmacie 92296 Châtenay-Malabry, France. Tel.: +33 1 46 83 57 59; fax: +33 1 46 83 54 75. Email address: bertrand.crozatier{at}cep.u-psud.fr
Objectives Myocardial stretch activates a number of interconnected pathways including the protein kinase C (PKC) pathway that in turn activates mitogen activated protein kinases (MAPK), leading to gene expression stimulation and ventricular hypertrophy. A role of calcineurin has also been shown during hypertrophy. The goal of our study was to look for a possible interconnection between PKC and calcineurin in myocardial stretch.
Methods Neonatal rat cardiomyocytes were cultured for 5 days and a 15% stretch was applied. Expression of MAPK and PKC-
was evaluated by Western blot analysis. The specific role of PKC- was evaluated by transfection of cardiomyocytes with a specific inhibitor peptide. Calcineurin and PKC- complex formation and co-localization were evaluated by co-immunoprecipitation and by immunolocalization.
Results The PKC isoform involved in stretch-induced ERK and JNK activations was PKC-. We show here that calcineurin is also found to be involved in the stretch response and that calcineurin and PKC- co-operate at 2 levels during stretch. First, stretch-induced translocation of PKC- from the cytosolic to the membrane fraction was inhibited by calcineurin inhibitors, indicating that calcineurin was necessary for PKC- activation induced by stretch. A second level of interaction was the formation of a calcineurin–PKC- complex, which increased during stretch. Immunofluorescent studies indicated that, after stretch, calcineurin and PKC- were co-localized at the level of the perinuclear membrane. These results may have a major relevance in vivo since we also found similar PKC-–calcineurin complexes in the phase of thoracic aortic stenosis in rats during which heart failure develops.
Conclusion Calcineurin appears to be necessary for stretch-induced PKC- activation after which the phosphatase and the kinase are co-localized in a complex at the level of the perinuclear membrane where they may finely regulate the phosphorylation of their target proteins.
KEYWORDS MAP kinases; Protein kinase C; Signal transduction; Myocytes