Effect of a dominant negative ras on myocardial hypertrophy by using adenoviral-mediated gene transfer.
BACKGROUND
The small guanosine triphosphate-binding protein ras regulates a signal transduction cascade linking cell surface receptors to mitogen-activated protein kinase (MAPK). Because the molecular signaling mechanisms underlying cardiac hypertrophy remain unclear, the current study examined the regulatory role of ras in both the biochemical and morphologic aspects of hypertrophy.


METHODS
Adenoviral-mediated gene transfer was used to express a dominant negative mutant of ras (rasN17) at high efficiency in primary neonatal ventricular myocytes. Beta-galactosidase staining and Western blot analysis confirmed successful transfection and expression of the rasN17 gene product. MAPK activity was measured by an in vitro kinase assay resulting in radioactive phosphorus labeled product. Morphologic hypertrophy was assessed by fluorescein-conjugated phalloidin.


RESULTS
Compared with uninfected or control adenoviral-infected cells, myocytes infected with rasN17 demonstrated attenuated basal MAPK activity. In contrast, rasN17 expression did not affect endothelin 1-induced MAPK activation. Morphologic studies showed that although rasN17 produced a phenotypic difference in the basal state, the ability of cardiac myocytes to morphologically respond to endothelin 1 stimulation, as manifested by sarcomeric reorganization, remained unaltered by the expression of the rasN17 gene product.


CONCLUSIONS
Endothelin 1-stimulated MAPK activation and endothelin 1-induced morphologic hypertrophy are ras-independent processes.
Pracyk
J B
JB
Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md., USA.
Hegland
D D
DD
Tanaka
K
K
D000256:Adenoviridae; D000818:Animals; D000831:Animals, Newborn; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D006332:Cardiomegaly / Q000201:enzymology / Q000473:pathology* / Q000503:physiopathology; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation; D015870:Gene Expression; D011905:Genes, ras; D005822:Genetic Vectors; D016297:Mutagenesis, Site-Directed; D009206:Myocardium / Q000166:cytology* / Q000201:enzymology / Q000473:pathology; D017354:Point Mutation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012518:Sarcomeres / Q000473:pathology / Q000502:physiology; D014162:Transfection; D001616:beta-Galactosidase / Q000096:biosynthesis
D019332:Endothelin-1; D011993:Recombinant Fusion Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D001616:beta-Galactosidase