Cyclic AMP inhibitors inhibits PDGF-stimulated mitogen-activated protein kinase activity in rat aortic smooth muscle cells via inactivation of c-Raf-1 kinase and induction of MAP kinase phosphatase-1.
In rat aortic smooth muscle cells (RASMC), pretreatment with forskolin inhibited the activation of p42/44 isoforms of mitogen-activated protein kinase (MAP) kinase stimulated in response to low concentrations of PDGF (10 ng/ml). This correlated with a strong inhibition of PDGF-stimulated MEK and C-Raf-1 kinase activity. However, the effect of forskolin could be surmounted by increasing the concentration of PDGF. Under such conditions forskolin was only effective against prolonged MAP kinase activation. The ability of forskolin to inhibit the late phase of MAP kinase activity was reversed by pretreatment of the cells with cycloheximide, suggesting the involvement of a protein synthesis step. This was not due to effects upstream of MAP kinase since PDGF-stimulated MEK activation was decreased by cycloheximide, an effect potentiated by forskolin. Forskolin stimulated the induction of the dual specific phosphatase MAP kinase phosphatase-1 (MKP-1), although this effect was small relative to levels induced by PDGF and angiotensin II. However, PDGF stimulated induction of MKP-1 was abolished by the protein kinase A inhibitor H89 and this correlated with the reversal of forskolin-mediated inhibition of PDGF-stimulated MAP kinase activity. These studies implicate a role for intracellular cyclic AMP in at least two aspects of MAP kinase signaling, including both the inhibition of Raf-1 activation and the induction of MKP-1.
Plevin
R
R
Department of Physiology & Pharmacology, University of Strathclyde, Glasgow, UK.
Malarkey
K
K
Aidulis
D
D
McLees
A
A
Gould
G W
GW
D000818:Animals; D001011:Aorta; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D054638:Dual Specificity Phosphatase 1; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000096:biosynthesis*; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D013449:Sulfonamides; D014981:Xenopus
D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D007211:Indoles; D007546:Isoquinolines; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D013449:Sulfonamides; D005576:Colforsin; D003513:Cycloheximide; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C064758:Ro 31-8220