Angiotensin II stimulates two myelin basic protein/microtubule-associated protein 2 kinases in cultured vascular smooth muscle cells.
In cultured vascular smooth muscle cells, angiotensin II (Ang II) stimulated a cytosolic protein kinase activity toward myelin basic protein (MBP) in a time- and dose-dependent manner. Phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate also increased the MBP kinase activity. Downregulation of protein kinase C by prolonged treatment of the cells with phorbol 12,13-dibutyrate markedly attenuated the Ang II- and PMA-induced MBP kinase activation. The Ang II- and PMA-stimulated MBP kinase activities were resolved almost equally into two distinct fractions on Mono-Q HR5/5 column chromatography (kinase 1 and kinase 2). The kinase assay in polyacrylamide gel revealed that apparent molecular masses of kinase 1 and kinase 2 were 40 and 45 kd, respectively. Microtubule-associated protein 2 also served as a substrate for both the kinases. Immunoblot analysis with an antiphosphotyrosine antibody suggested that both the kinases were tyrosine-phosphorylated during the action of Ang II. Phosphoamino acid analysis revealed that Ang II and PMA induced phosphorylation of both the kinases on serine/threonine as well as tyrosine residues. Phosphopeptide mapping patterns of kinase 1 and kinase 2 isolated from Ang II-stimulated cells were almost identical with those from PMA-stimulated cells. These results indicate that in vascular smooth muscle cells Ang II activates two species of MBP/microtubule-associated protein 2 kinases mainly through the protein kinase C-signaling pathway and suggest that tyrosine and serine/threonine phosphorylation may be involved in this process.
Tsuda
T
T
Department of Internal Medicine (1st Division), Kobe University School of Medicine, Japan.
Kawahara
Y
Y
Ishida
Y
Y
Koide
M
M
Shii
K
K
Yokoyama
M
M
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002478:Cells, Cultured / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013379:Substrate Specificity; D014443:Tyrosine
D000804:Angiotensin II; D014443:Tyrosine; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3