Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Trapidil, an antiplatelet drug, has been shown to reduce restenosis after angioplasty. It exerts its action, at least in part, by inhibiting vascular smooth muscle cell proliferation, antagonizing platelet-derived growth factor (PDGF). We examined its site of action on PDGF cellular signaling. Exposure of cultured rat vascular smooth muscle cells to increasing concentrations of trapidil for 18 hours resulted in a dose-dependent reduction in PDGF-BB-stimulated [3H] thymidine incorporation. Trapidil (400 microg/mL) increased PDGF beta-receptor protein by 28+/-8%, whereas PDGF-induced tyrosine phosphorylation of PDGF beta-receptor remained unchanged. PDGF-induced tyrosine phosphorylation of phospholipase Cgamma, the p85 regulatory subunit of phosphatidyl-inositol 3 kinase, Ras GTPase-activating protein, and an adaptor molecule Shc were also not altered. On the other hand, trapidil inhibited PDGF-stimulated mitogen-activated protein kinase (MAP kinase) activity by 35+/-7% at 10 minutes and by 32+/-10% at 6 hours. Activation of Raf-1, an upstream activator of MAP kinase, by PDGF was also attenuated by trapidil. Moreover, protein content of MAP kinase phosphatase-1, which inactivates MAP kinase, was elevated in trapidil-treated cells. These actions of trapidil may be mediated by cAMP. Thus, there was a 1.9-fold increase in cellular cAMP generation in trapidil-treated cells. The present results demonstrate that trapidil antagonizes PDGF-induced mitogenesis and MAP kinase activation in vascular smooth muscle cells, probably through cAMP.
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PMID:Trapidil inhibits platelet-derived growth factor-stimulated mitogen-activated protein kinase cascade. 946 Dec 38

The triazolopyrimidine trapidil has been found in controlled clinical trials to prevent restenosis after vascular injury. Although trapidil is widely regarded as a platelet-derived growth factor receptor (PDGF) antagonist, its precise mode of action is still unknown. This study was designed to investigate the inhibition of mitogenesis by trapidil in cultured bovine coronary artery smooth muscle cells (SMC) and to identify major signal transduction pathways involved. Trapidil inhibited PDGF-BB-induced mitogenesis in SMC in a concentration-dependent manner. Comparable inhibitory effects were obtained after stimulation of smooth muscle cells by phorbol ester, which suggests that the action of trapidil was not restricted to PDGF receptor-mediated mechanisms. Trapidil also inhibited PDGF- and phorbol ester-induced mitogen-activated protein kinase as well as Raf-1 kinase activity. As a possible target of trapidil, stimulation of cellular protein kinase A (PKA) activity was detected. Trapidil also induced the phosphorylation of vasodilator-stimulated phosphoprotein in SMC. Antimitogenic effects of trapidil were completely abolished by PKA inhibitors. Neither a direct stimulation of cAMP formation nor a phosphodiesterase inhibition was observed at antimitogenic concentrations of trapidil. However, trapidil directly activated purified PKA holoenzyme in a cAMP-independent manner. In conclusion, trapidil exerts its antimitogenic effects on SMC by direct activation of PKA. Thus, PKA-mediated inhibition of the Raf-1/MAP kinase pathway may be involved in the antimitogenic actions of the compound.
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PMID:Antimitogenic effects of trapidil in coronary artery smooth muscle cells by direct activation of protein kinase A. 968 64

Trapidil suppresses platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell (VSMC) proliferation by inhibiting Raf-1/extracellular signal-regulated kinase (ERK) via cAMP/protein kinase A (PKA). We examined whether trapidil inhibits PDGF-induced VSMC migration and investigated its mechanisms of action. VSMC migration was inhibited to a similar extent by trapidil and forskolin. A PKA inhibitor N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide (H89) blocked the inhibition by forskolin to a greater degree than that by trapidil. Trapidil but not forskolin suppressed PDGF-stimulated RhoA activation. In the presence of both H89 and (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride monohydrate, an inhibitor of Rho-associated kinase (ROCK), trapidil and forskolin inhibited migration to a similar extent. Thus, in addition to cAMP/PKA activation, trapidil inhibits RhoA/ROCK activation, which may be important in trapidil's inhibitory effect on migration.
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PMID:Trapidil inhibits platelet-derived growth factor-induced migration via protein kinase A and RhoA/Rho-associated kinase in rat vascular smooth muscle cells. 1589 6