Calcineurin B homologous protein 3 negatively regulates cardiomyocyte hypertrophy via inhibition of glycogen synthase kinase 3 phosphorylation.
Cardiac hypertrophy is a leading cause of serious heart diseases. Although many signaling molecules are involved in hypertrophy, the functions of some proteins in this process are still unknown. Calcineurin B homologous protein 3 (CHP3)/tescalcin is an EF-hand Ca(2+)-binding protein that is abundantly expressed in the heart; however, the function of CHP3 is unclear. Here, we aimed to identify the cardiac functions of CHP3. CHP3 was expressed in hearts at a wide range of developmental stages and was specifically detected in neonatal rat ventricular myocytes (NRVMs) but not in cardiac fibroblasts in culture. Moreover, knockdown of CHP3 expression using adenoviral-based RNA interference in NRVMs resulted in enlargement of cardiomyocyte size, concomitant with increased expression of a pathological hypertrophy marker ANP. This same treatment elevated glycogen synthase kinase (GSK3α/β) phosphorylation, which is known to inhibit GSK3 function. In contrast, CHP3 overexpression blocked the insulin-induced phosphorylation of GSK3α/β without affecting the phosphorylation of Akt, which is an upstream kinase of GSK3α/β, in HEK293 cells, and it inhibited both IGF-1-induced phosphorylation of GSK3β and cardiomyocyte hypertrophy in NRVMs. Co-immunoprecipitation experiments revealed that GSK3β interacted with CHP3. However, a Ca(2+)-binding-defective mutation of CHP3 (CHP3-D123A) also interacted with GSK3β and had the same inhibitory effect on GSK3α/β phosphorylation, suggesting that the action of CHP3 was independent of Ca(2+). These findings suggest that CHP3 functions as a novel negative regulator of cardiomyocyte hypertrophy via inhibition of GSK3α/β phosphorylation and subsequent enzymatic activation of GSK3α/β.
Department of Molecular Physiology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan.
Soushi
S
Kobayashi
Department of Molecular Physiology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan.
Tomoe Y
TY
Nakamura
Department of Molecular Physiology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan. Electronic address: wak@ri.ncvc.go.jp.
Shigeo
S
Wakabayashi
D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D057809:HEK293 Cells; D006801:Humans; D006984:Hypertrophy; D047468:Immunoprecipitation; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D050505:Mutant Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats
D002135:Calcium-Binding Proteins; D007328:Insulin; D050505:Mutant Proteins; C486009:TESC protein, human; C000606248:Tesc protein, rat; D007334:Insulin-Like Growth Factor I; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha; D002118:Calcium
Calcineurin B homologous protein; Cardiac hypertrophy; Cardiomyocytes