Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51812 (mitogen-activated protein)
 10,636 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation of h-caldesmon has been proposed to regulate airway smooth muscle contraction. Both extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinases phosphorylate h-caldesmon in vitro. To determine whether both enzymes phosphorylate caldesmon in vivo, phosphorylation-site-selective antibodies were used to assay phosphorylation of MAP kinase consensus sites. Stimulation of cultured tracheal smooth muscle cells with ACh or platelet-derived growth factor increased caldesmon phosphorylation at Ser789 by about twofold. Inhibiting ERK MAP kinase activation with 50 microM PD-98059 blocked agonist-induced caldesmon phosphorylation completely. Inhibiting p38 MAP kinases with 25 microM SB-203580 had no effect on ACh-induced caldesmon phosphorylation. Carbachol stimulation increased caldesmon phosphorylation at Ser789 in intact tracheal smooth muscle, which was blocked by the M(2) antagonist AF-DX 116 (1 microM). AF-DX 116 inhibited carbachol-induced isometric contraction by 15 +/- 1.4%, thus dissociating caldesmon phosphorylation from contraction. Activation of M(2) receptors leads to activation of ERK MAP kinases and phosphorylation of caldesmon with little or no functional effect on isometric force. P38 MAP kinases are also activated by muscarinic agonists, but they do not phosphorylate caldesmon in vivo.
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PMID:Phosphorylation of caldesmon by ERK MAP kinases in smooth muscle. 1075 21

Quantitative sandwich enzyme immunoassay (EIA) systems, that can distinguish between active-form subtypes of mitogen-activated protein kinases (p44 and p42 MAP kinase, also called ERK1 and ERK2), were developed employing subtype-specific antibodies as a solid phase and an antibody specific for the phosphorylated region of MAP kinases as the detector. Using these systems, we investigated the dynamic changes in the activity of ERK1 and ERK2 in platelet-derived growth factor (PDGF)-treated rat mesangial cells and nerve growth factor (NGF)-treated PC12. Both ERK1 and ERK2 were activated immediately after stimulation, and the activity reached a maximum at 5-10 min. The total activity of both subtypes correlated well with that obtained using the conventional method. Compared with the usual methods, these systems should have a higher specificity and be more convenient and suitable for experiments with multiple samples. Moreover, as these EIA systems can be applied not only to rat MAP kinases but also to human, mouse and rabbit MAP kinases, they are potentially very useful for a range of investigations.
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PMID:Development of EIA systems for active-form MAP kinase. 1075 39

Gab1 is a member of the Gab/DOS (Daughter of Sevenless) family of adapter molecules, which contain a pleckstrin homology (PH) domain and potential binding sites for SH2 and SH3 domains. Gab1 is tyrosine phosphorylated upon stimulation of various cytokines, growth factors, and antigen receptors in cell lines and interacts with signaling molecules, such as SHP-2 and phosphatidylinositol 3-kinase, although its biological roles have not yet been established. To reveal the functions of Gab1 in vivo, we generated mice lacking Gab1 by gene targeting. Gab1-deficient embryos died in utero and displayed developmental defects in the heart, placenta, and skin, which were similar to phenotypes observed in mice lacking signals of the hepatocyte growth factor/scatter factor, platelet-derived growth factor, and epidermal growth factor pathways. Consistent with these observations, extracellular signal-regulated kinase mitogen-activated protein (ERK MAP) kinases were activated at much lower levels in cells from Gab1-deficient embryos in response to these growth factors or to stimulation of the cytokine receptor gp130. These results indicate that Gab1 is a common player in a broad range of growth factor and cytokine signaling pathways linking ERK MAP kinase activation.
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PMID:Role of Gab1 in heart, placenta, and skin development and growth factor- and cytokine-induced extracellular signal-regulated kinase mitogen-activated protein kinase activation. 1077 59

We have previously reported that tranilast, an anti-allergic drug, prevented the experimental intimal thickening in the rat and mouse femoral arteries and its effect may be exerted through the inhibition of vascular smooth muscle cell proliferation. However, its inhibitory mechanism has yet to be understood. In this study, we investigated the inhibitory effect of tranilast on platelet-derived growth factor BB-homodimer (PDGF-BB) mediated signal transduction pathways in cultured human coronary artery smooth muscle cells (CASMCs). Growth responses to PDGF-BB were measured by [(3)H]-thymidine incorporation or cell counting. Activation of DNA synthesis and augmentation of cell proliferation stimulated by PDGF-BB in quiescent cultures of CASMCs were inhibited by tranilast in a concentration-dependent manner. Western blot analysis of lysates from CASMCs with an anti-activated mitogen-activated protein (MAP) kinase antibody revealed that tranilast (10 - 300 microM) inhibited MAP kinase activation by PDGF-BB in a concentration-dependent manner. Tranilast also reduced PDGF-BB-stimulated tyrosine phosphorylation of a 180 kDa band, corresponding in mass to the PDGF beta-receptor, as shown by immunoblots using an anti-phosphotyrosine antibody. Receptor-binding study with [(125)I]-PDGF-BB on CASMCs showed that tranilast (10 - 1000 microM) inhibited the specific binding of PDGF-BB to cell surface receptors in a concentration-dependent manner. Scatchard analysis revealed that pretreatment with 300 microM tranilast decreased the maximum binding capacity (B(max)) from 27.6 to 18.0 fmol 10(6) cells(-1) without affecting binding affinity (K(d) approximately 0.15 nM), indicating a non-competitive inhibition of the receptor binding. These results suggest that the suppression of human CASMC growth by tranilast might be at least partly due to blockade of PDGF-BB-receptor binding.
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PMID:Inhibitory mechanism of tranilast in human coronary artery smooth muscle cells proliferation, due to blockade of PDGF-BB-receptors. 1080 67

Enhanced activity of receptor tyrosine kinases such as the platelet-derived growth factor-receptorbeta (PDGF-Rbeta) has been implicated as a contributing factor in the development of hepatic fibrosis. In this study we have used tyrosine kinase inhibitors of the tyrphostin class (AG1295) to specifically block autophosphorylation of PDGF-Rbeta and proliferation of rat hepatic stellate cells. We also examined the effect of AG1295 on the PDGF-BB-induced activation of the 44 kd and 42 kd mitogen-activated protein (MAP) kinase isoforms (p44mapk/p42mapk). Rat hepatic stellate cells were treated with AG1295 (10 micromol/L) for 24 hours and stimulated with PDGF-BB for 5 minutes. AG1295 specifically inhibited autophosphorylation of PDGF-Rbeta and caused a 20% decrease in PDGF-BB-stimulated bromodeoxyuridine incorporation by rat hepatic stellate cells. Treatment of rat hepatic stellate cells with AG1295 resulted in an inhibition of the PDGF-BB-induced activation of MAP kinase isoforms. Quantification of the immunoprecipitated tyrosine-phosphorylated phosphatidylinositol 3-kinase, phospholipase C-gamma, and p21ras guanosine triphosphatase-activating protein by Western blotting revealed that AG1295 treatment effectively inhibits tyrosine phosphorylation of these kinases in hepatic stellate cells. Our findings demonstrate that AG1295 is a selective inhibitor of the tyrosine phosphorylation of PDGF-Rbeta and its downstream signaling pathway, and this compound could offer a strategy for the treatment of fibrotic liver diseases.
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PMID:Platelet-derived growth factor receptor tyrosine kinase inhibitor AG1295 attenuates rat hepatic stellate cell growth. 1081 Oct 56

Retinoic acid is known to cause the myeloid differentiation and G1/0 cell cycle arrest of HL-60 cells in a process that requires mitogen-activated protein/extracellular signal regulated kinase (MEK)-dependent extracellular signal regulated kinase (ERK)2 activation. It has also been shown that ectopic expression of cFMS, a platelet-derived growth factor (PDGF)-family transmembrane tyrosine kinase receptor, enhances retinoic acid-induced differentiation and G1/0 arrest. The mechanism of how the retinoic acid and cFMS signaling pathways intersect is not known. The present data show that the ectopic expression of cFMS results in the differential loss of sensitivity of retinoic acid-induced differentiation or G1/0 arrest to inhibition of ERK2 activation. PD98059 was used to inhibit MEK and consequently ERK2. In wildtype HL-60 cells, PD98059 blocked retinoic acid-induced differentiation; but in cFMS stable transfectants, PD98059 only attenuated the induced differentiation, with the resulting response resembling that of retinoic acid-treated wild-type HL-60. In wild-type HL-60, PD98059 greatly attenuated the retinoic acid-induced G1/0 arrest allied with retinoblastoma (RB) hypophosphorylation; but in cFMS stable transfectants, PD98059 had no inhibitory effect on RB hypophosphorylation and G1/0 arrest. This differential sensitivity to PD98059 and uncoupling of retinoic acid-induced differentiation and G1/0 arrest in cFMS transfectants is associated with changes in mitogen-activated protein kinase signaling molecules. The cFMS transfectants had more activated ERK2 than did the wild-type cells, which surprisingly was not attributable to enhanced mitogen-activated protein-kinase-kinase-kinase (RAF) phosphorylation. Retinoic acid increased the amount of activated ERK2 and phosphorylated RAF in both cell lines. But PD98059 eliminated detectable ERK2 activation, as well as inhibited RAF phosphorylation, in untreated and retinoic acid-treated wild-type HL-60 and cFMS transfectants, consistent with MEK or ERK feedback-regulation of RAF, in all four cases. Since PD98059 blocks the cFMS-conferred enhancement of the retinoic acid-induced differentiation, but not growth arrest, the data indicate that cFMS-enhanced differentiation acts primarily through MEK and ERK2, but cFMS-enhanced G1/0 arrest allied with RB hypophosphorylation depends on another cFMS signal route, which by itself can effect G1/0 arrest without activated ERK2. Ectopic expression of cFMS and differential sensitivity to ERK2 inhibition thus reveal that retinoic acid-induced HL-60 cell differentiation and G1/0 arrest are differentially dependent on ERK2 and can be uncoupled. A significant unanticipated finding was that retinoic acid caused a MEK-dependent increase in the amount of phosphorylated RAF. This increase may help sustain prolonged ERK2 activation.
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PMID:Retinoic acid increases amount of phosphorylated RAF; ectopic expression of cFMS reveals that retinoic acid-induced differentiation is more strongly dependent on ERK2 signaling than induced GO arrest is. 1085 50

Proliferation of vascular smooth muscle cells (SMC) in response to platelet-derived growth factor (PDGF) and other mitogens plays an important role in restenosis following coronary angioplasty. Elevation of adenosine 3',5'-cyclic monophosphate (cAMP) concentration in SMC has been shown to inhibit SMC mitogenesis and could be obtained either directly by stimulation of adenylyl cyclase-coupled receptors or indirectly by inhibition of cAMP-specific phosphodiesterase (PDE4) or the cyclic guanosine 3', 5'-monophosphate-inhibitable phosphodiesterase (PDE3). This study compared the effects of the selective PDE3 inhibitors trequinsin and quazinone with the selective PDE4 inhibitors Ro 20-1724 and rolipram on PDGF-induced DNA synthesis, mitogen-activated protein (MAP) kinase activation, cAMP levels, and protein kinase A (PKA) activation in SMC. Both PDE3 and PDE4 inhibitors stimulated intracellular PKA activation as seen from phosphorylation of vasodilator-stimulated phosphoprotein (VASP). However, only PDE3 inhibitors, and not inhibitors of PDE4, reduced PDGF-induced DNA synthesis and inhibited p42/p44 MAP kinase phosphorylation. At antimitogenic concentrations, the PDE3 inhibitors had only minor effects on cAMP levels. In contrast, PDE4 inhibitors increased the forskolin-induced cellular cAMP concentration 13- to 17-fold above control. These data demonstrate that inhibitors of PDE3 are potent antimitogenic agents and that a general increase in cellular cAMP levels and PKA activation per se are not sufficient to inhibit PDGF-induced SMC mitogenesis.
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PMID:Inhibition of platelet-derived growth factor-induced mitogenesis by phosphodiesterase 3 inhibitors: role of protein kinase A in vascular smooth muscle cell mitogenesis. 1085 33

Mechanical force is an important modulator of cellular morphology and function in a variety of tissues, and is particularly important in cardiovascular systems. Vascular smooth muscle cell (VSMC) hypertrophy and proliferation contribute to the development of atherosclerosis, hypertension, and restenosis, where mechanical forces are largely disturbed. How VSMCs sense and transduce the extracellular mechanical signals into the cell nucleus resulting in quantitative and qualitative changes in gene expression is an interesting and important research field. Recently, it has been demonstrated that mechanical stress rapidly induced phosphorylation of platelet-derived growth factor (PDGF) receptor, activation of integrin receptor, stretch-activated cation channels, and G proteins, which might serve as mechanosensors. Once mechanical force is sensed, protein kinase C and mitogen-activated protein kinases (MAPKs) were activated, leading to increased c-fos and c-jun gene expression and enhanced transcription factor AP-1 DNA-binding activity. Interestingly, physical forces also rapidly resulted in expression of MAPK phosphatase-1 (MKP-1), which inactivates MAPKs. Thus, mechanical stresses can directly stretch the cell membrane and alter receptor or G protein conformation, thereby initiating signalling pathways, usually used by growth factors. These findings have significantly enhanced our knowledge of the pathogenesis of arteriosclerosis and provided promising information for therapeutic interventions for vascular diseases.
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PMID:Mechanical stress-initiated signal transductions in vascular smooth muscle cells. 1098 77

In previous studies we have showed that somatostatin (SST) inhibits cell division, mitogen-activated protein (MAP) kinase and Ras activity in the human neuroblastoma cell line SY5Y. In the present study, we have assessed the role of a series of SST analogs, three of which were selective for SSTR1, SSTR2 or SSTR5, in these cellular events. All the analogs inhibited forskolin-induced cAMP accumulation. Selective stimulation of SSTR1 or SSTR2 but not of SSTR5 inhibited platelet-derived growth factor (PDGF)-induced [(3)H]thymidine incorporation. The three analogs inhibited PDGF-stimulated MAP kinase activity, at least at an early time. In contrast, none of the analogs used individually was able to inhibit PDGF-stimulated Ras activity. A combined stimulation of SSTR2 and SSTR5 was necessary to obtain a significant inhibitory effect, suggesting the possibility of receptor heterodimerization. These results indicate that SST inhibition of Ras and MAP kinase activities takes place via different pathways and that SST inhibition of PDGF-induced cell proliferation occurs via a Ras-independent pathway.
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PMID:Selective stimulation of somatostatin receptor subtypes: differential effects on Ras/MAP kinase pathway and cell proliferation in human neuroblastoma cells. 1100 77

Stress responses induced in fibroblasts by cryopreservation were compared in suspension or three-dimensional cultures at various times up to 5 days of recovery. Cryopreservation caused an 86% inhibition in [(35)S]methionine incorporation, with recovery over 2 days to 45% &plusmn: 14% of its original value. Stress proteins, including heat shock protein (hsp) and glucose-regulated proteins (GRP), detected by immunoblotting, responded with transient increases in cellular content (hsp27 and hsp90 in suspension and three-dimensional culture, and hsp70 only in three-dimensional culture), decreases at 24 h (hsp56, hsp70, hsp90, and GRP78 in three-dimensional culture and hsp90 in suspension), or little change (hsp70 in suspension). Polyacrylamide gel electrophoresis of [(35)S]methionine-labeled proteins showed transient induction of hsp47 within 4 h, and increased synthesis of hsp90 and GRP78 and other unidentified proteins at 24 h, but no change in hsp70. The mitogen-activated protein (MAP) kinase, p38, showed a transient increase after thawing, followed by a peak in extracellular signal-regulated kinase at 24 h. The stress-activated protein kinase (JNK) was not activated. In both stress protein and MAP kinase responses, the three-dimensional cultures showed a more intense response than fibroblasts in suspension. Although some responses were related to osmotic and cold stress during freezing, others were unique. Cryopreservation induced mRNA for selected growth factors, including vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) A chain, which increased 5- to 20- fold at 48 h returning to basal levels by 120 h. Our results indicate the novel finding that cryopreservation of fibroblasts grown in three-dimensional culture induced a specific cellular stress response including growth factors.
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PMID:Comparison of the stress response to cryopreservation in monolayer and three-dimensional human fibroblast cultures: stress proteins, MAP kinases, and growth factor gene expression. 1107 40


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