Isoproterenol activates extracellular signal-regulated protein kinases in cardiomyocytes through calcineurin.
BACKGROUND
Extracellular signal-regulated kinases (ERKs) and calcineurin have been reported to play important roles in the development of cardiac hypertrophy. We examined here the relation between calcineurin and ERKs in cardiomyocytes.


RESULTS
Isoproterenol activated ERKs in cultured cardiomyocytes of neonatal rats, and the activation was abolished by chelation of extracellular Ca(2+) with EGTA, blockade of L-type Ca(2+) channels with nifedipine, or depletion of intracellular Ca(2+) stores with thapsigargin. Isoproterenol-induced activation of ERKs was also significantly suppressed by calcineurin inhibitors in cultured cardiomyocytes as well as in the hearts of mice. Isoproterenol failed to activate ERKs in either the cultured cardiomyocytes or the hearts of mice that overexpress the dominant negative mutant of calcineurin. Isoproterenol elevated intracellular Ca(2+) levels at both systolic and diastolic phases and dose-dependently activated calcineurin. Inhibition of calcineurin also attenuated isoproterenol-stimulated phosphorylation of Src, Shc, and Raf-1 kinase. The immunocytochemistry revealed that calcineurin was localized in the Z band, and isoproterenol induced translocation of calcineurin and ERKs into the nucleus.


CONCLUSIONS
Calcineurin, which is activated by marked elevation of intracellular Ca(2+) levels by the Ca(2+)-induced Ca(2+) release mechanism, regulates isoproterenol-induced activation of ERKs in cardiomyocytes.
Zou
Y
Y
Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, Chiba.
Yao
A
A
Zhu
W
W
Kudoh
S
S
Hiroi
Y
Y
Shimoyama
M
M
Uozumi
H
H
Kohmoto
O
O
Takahashi
T
T
Shibasaki
F
F
Nagai
R
R
Yazaki
Y
Y
Komuro
I
I
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D006332:Cardiomegaly / Q000201:enzymology*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D007545:Isoproterenol / Q000494:pharmacology*; D051379:Mice; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000318:Adrenergic beta-Agonists; D065095:Calcineurin Inhibitors; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D011506:Proteins; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019061:src-Family Kinases; D019908:Proto-Oncogene Proteins c-raf; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D019703:Calcineurin; D007545:Isoproterenol; D002118:Calcium