The low molecular weight GTPase Rho regulates myofibril formation and organization in neonatal rat ventricular myocytes. Involvement of Rho kinase.
The assembly of contractile proteins into organized sarcomeric units is one of the most distinctive features of cardiac myocyte hypertrophy. In a well characterized in vitro model system using cultured neonatal rat ventricular myocytes, a subset of G protein-coupled receptor agonists has been shown to induce actin-myosin filament organization. Pretreatment of myocytes with C3 exoenzyme ADP-ribosylated Rho and inhibited the characteristic alpha1-adrenergic receptor agonist-induced myofibrillar organization, suggesting involvement of the Rho GTPase in cardiac myofibrillogenesis. We used adenoviral mediated gene transfer to examine the effects of activated Rho and inhibitory mutants of one of its effectors, Rho kinase, in myocytes. Rho immunoreactivity was increased in the particulate fraction of myocytes infected with a recombinant adenovirus expressing constitutively activated Rho. Rho-infected cells demonstrated a striking increase in the assembly and organization of sarcomeric units and in the expression of the atrial natriuretic factor protein. These Rho-induced responses were markedly inhibited by co-infection with adenoviruses expressing putative dominant negative forms of Rho kinase. A parallel pathway involving Ras-induced myofibrillar organization and atrial natriuretic factor expression was only minimally affected. alpha1-Adrenergic receptor agonist-induced myofibrillogenesis was inhibited by some but not all of the Rho kinase mutants. Our data demonstrate that activated Rho has profound effects on myofibrillar organization in cardiac myocytes and suggest that Rho kinase mediates Rho-induced hypertrophic responses.
Hoshijima
M
M
Department of Medicine and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093, USA.
Sah
V P
VP
Wang
Y
Y
Chien
K R
KR
Brown
J H
JH
D036002:ADP Ribose Transferases / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D001905:Botulinum Toxins; D002478:Cells, Cultured; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009206:Myocardium / Q000201:enzymology*; D009210:Myofibrils / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D015398:Signal Transduction; D020703:ras GTPase-Activating Proteins; D054460:rho-Associated Kinases
D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D018340:Receptors, Adrenergic, alpha-1; D020703:ras GTPase-Activating Proteins; D009320:Atrial Natriuretic Factor; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D001905:Botulinum Toxins; D020558:GTP Phosphohydrolases