Caveolin-3 inhibits growth signal in cardiac myoblasts in a Ca2+-dependent manner.
Caveolin, a major protein component of caveolae, directly interacts with multiple signaling molecules, such as Ras and growth factor receptors, and inhibits their function. However, the role of the second messenger system in mediating this inhibition by caveolin remains poorly understood. We examined the role of Ca2+-dependent signal in caveolin- mediated growth inhibition using a rat cardiac myoblast cell line (H9C2), in which the expression of caveolin- 3, the muscle specific subtype, can be induced using the LacSwitch system. Upon induction with IPTG and serum-starvation, the expression of caveolin-3 was increased by 3.3-fold relative to that of mock-induced cells. The recombinant caveolin-3 was localized to the same subcellular fraction as endogenous caveolin-3 after sucrose gradient purification. Angiotensin II enhanced ERK phosphorylation, but this enhancement was significantly decreased in caveolin-3-induced cells in comparison to that in mock-induced cells. Similarly, when cells were stimulated with fetal calf serum, DNA synthesis, as determined by [3H]-thymidine incorporation, was significantly decreased in caveolin- 3-induced cells. When cells were treated with Ca2+ chelator (BAPTA and EGTA), however, this attenuation was blunted. Calphostin (PKC inhibitor), but not cyclosporine A treatment (calcineurin inhibitor), blunted this attenuation in caveolin-3 induced cells. Our findings suggest that caveolin exhibits growth inhibition in a Ca2+-dependent manner, most likely through PKC, in cardiac myoblasts.
Fujita
Takayuki
T
Cardiovascular Research Institute, Department of Pathology and Department of Medicine, Yokohama City University Graduate School of Medical Science, Fukuura, Yokohama, Japan.
Otsu
Kouji
K
Oshikawa
Jin
J
Hori
Hideaki
H
Kitamura
Hitoshi
H
Ito
Takaaki
T
Umemura
Satoshi
S
Minamisawa
Susumu
S
Ishikawa
Yoshihiro
Y
D000809:Angiotensins / Q000378:metabolism; D000818:Animals; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism*; D021941:Caveolae / Q000502:physiology; D051244:Caveolin 3 / Q000378:metabolism*; D002460:Cell Line; D049109:Cell Proliferation; D002999:Clone Cells; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D032386:Myoblasts, Cardiac / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D015398:Signal Transduction
D000809:Angiotensins; D065095:Calcineurin Inhibitors; D051244:Caveolin 3; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium