PKC mediates cyclic stretch-induced cardiac hypertrophy through Rho family GTPases and mitogen-activated protein kinases in cardiomyocytes.
Signaling events, including Rho GTPases and protein kinase C (PKC), are involved in cardiac hypertrophy. However, the mechanisms by which these pathways cooperate during the hypertrophic process remain unclear. Using an in vitro cyclic stretch model with neonatal rat cardiomyocytes, we demonstrated that stretch-induced activation of RhoA, Rac1/Cdc42, and phosphorylation of Rho-guanine nucleotide dissociation inhibitor (GDI) were prevented by inhibition or depletion of PKC, using chelerythrine and phorbol 12-myristate 13-acetate, indicating that phorbol ester-sensitive PKC isozymes may be upstream regulators of Rho GTPases. Using adenoviral-mediated gene transfer of wild-type (WT) and dominant-negative (DN) mutants of PKCalpha and delta, we found that stretch-induced activation of Rho GTPases and phosphorylation of Rho-GDI were mainly regulated by PKCalpha. PKCdelta was involved in regulation of the activation of Rac1. Stretch-induced increases in [(3)H]-leucine incorporation, myofibrillar reorganization and cell size, were blocked by inhibition of Rho GTPases, or overexpression of DN PKCalpha and delta, suggesting that PKCalpha and delta are both required in stretch-induced hypertrophy, through Rho GTPases-mediated signaling pathways. The mechanism, whereby PKC and Rho GTPases regulate hypertrophy, was associated with mitogen-activated protein (MAP) kinases. Stretch-stimulated phosphorylation of MEK1/ERK1/2 and MKK4/JNK was inhibited by overexpression of DN PKCalpha and delta, and that of MKK3/p38 inhibited by DN PKCdelta. The phosphorylation of ERK and JNK induced by overexpression of WT PKCalpha, and the phosphorylation of p38 induced by WT PKCdelta, were regulated by Rho GTPases. This study represents the first evidence that PKCalpha and delta are important regulators in mediating activation of Rho GTPases and MAP kinases, in the cyclic stretch-induced hypertrophic process.
Pan
Jing
J
Division of Molecular Cardiology, Cardiovascular Research Institute, The Texas A&M University System Health Science Center, College of Medicine, Temple, Texas 76504, USA. jpan@medicine.tamu.edu
Singh
Ugra S
US
Takahashi
Toshiyuki
T
Oka
Yoshitomo
Y
Palm-Leis
Ants
A
Herbelin
Bradley S
BS
Baker
Kenneth M
KM
D000818:Animals; D000831:Animals, Newborn; D006332:Cardiomegaly / Q000209:etiology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013347:Subcellular Fractions / Q000201:enzymology; D014018:Tissue Distribution; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
D020730:Guanine Nucleotide Dissociation Inhibitors; D007527:Isoenzymes; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020741:rho GTP-Binding Proteins