Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.12.2 (MEK)
 18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously reported that mast cell tryptase is a potent mitogen for cultured airway smooth-muscle cells, but the early intracellular signals mediating this response are not known. In many cells, proliferative effects are mediated by a mitogen-activated protein kinase signaling pathway involving Raf-1, MAP kinase kinases (MEKs), and extracellular signal-regulated protein kinases (ERKs) 1 and 2. Therefore, we tested for tryptase-induced activation of ERK1 and 2 in cultured dog tracheal smooth-muscle cells. Tryptase, in nanomolar concentrations which potently stimulated DNA synthesis, increased dual phosphorylation of ERKs in cellular lysates as well as ERK2 kinase activity in immunoprecipitates. Pretreatment of cells with the MEK inhibitor PD098059 abolished tryptase-induced increases in DNA synthesis and attenuated increases in ERK2 activity. Irreversible inhibition of tryptase's proteolytic activity, using p-amidino phenylmethanesulfonyl fluoride, attenuated tryptase-induced increases in DNA synthesis and dual phosphorylation of ERKs by 76% and 40 to 60%, respectively. Tryptase also increased c-fos transcription as quantified in polymerase chain reactions. In concentrations that caused similar increases in DNA synthesis, tryptase and platelet-derived growth factor (PDGF-BB) increased ERK activity (and c-fos transcription) with markedly different kinetics, the tryptase-induced responses being slower in onset and more sustained. We conclude that tryptase-induced mitogenesis in airway smooth-muscle cells requires activation of ERK1 and 2; that these responses depend partially, but not completely, upon tryptase's properties as a protease; and that they are slower in onset and more sustained than those induced by PDGF-BB.
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PMID:Mast cell tryptase activates extracellular-regulated kinases (p44/p42) in airway smooth-muscle cells: importance of proteolytic events, time course, and role in mediating mitogenesis. 1115 48

The mast cell product tryptase, via protease-activated receptor 2 (PAR2), induces cyclooxygenase-2 (COX2) and 15-deoxy-prostaglandin J2 (15d-PGJ2) synthesis. 15d-PGJ2, through the nuclear peroxisome proliferator activated receptor gamma (PPARgamma), subsequently causes fibroblast proliferation. In this study we attempted to determine initial events of the tryptase/PAR2 signaling pathway leading to COX2 induction and fibroblast proliferation. In human fibroblasts (HFFF2), cDNA array, RT-PCR and Western blotting studies demonstrated that tryptase, but not 15d-PGJ2, up-regulates c-jun, c-fos and COX2 expression, and phosphorylates the extracellular signal-regulated kinase isoforms 1 and 2 (erk1/2). Furthermore, tryptase effects on erk1/2, c-jun, c-fos, COX2 and cell proliferation were prevented by PD98059, an inhibitor of the mitogen-activated protein kinase kinase (MEK). Other kinases [P38, stress-activated protein kinase/c-jun N-terminal kinase (SAPK/JUNK), erk5], intracellular Ca(2+) or cAMP were not affected by tryptase/PAR2. Our study identifies crucial intracellular events leading to induction of COX2 and fibroblast proliferation, i.e. a cornerstone of fibrosis.
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PMID:The action of the mast cell product tryptase on cyclooxygenase-2 (COX2) and subsequent fibroblast proliferation involves activation of the extracellular signal-regulated kinase isoforms 1 and 2 (erk1/2). 1560 29

We found that striptease-positive mast cells were abundant in the invasive front of human colon adenocarcinoma by examining 30 cases. Because tryptase has been suggested to be the agonist proteinase for protease-activated receptor-2 (PAR-2), we investigated the effects of stimulation of PAR-2 by tryptase on the cell signaling and proliferation of DLD-1, a human colon carcinoma cell line. PAR-2 stimulation by tryptase induced the increase in [Ca(2+)](i), which was desensitized by the prior application of PAR-2 activating peptide (AP). The proliferative responses of DLD-1 to tryptase and PAR-2 AP were associated with the phosphorylation of MEK and MAP kinase. Inhibition of MEK by PD98059 completely inhibited the proliferation-enhancing effects of tryptase and PAR-2 AP as well as phosphorylation of MAP kinase. Moreover, tryptase and PAR-2 AP stimulated the production of prostaglandin E2 and the inhibition of prostaglandin synthesis by indomethacin or NS398 resulted in the complete inhibition of the proliferative responses to tryptase and PAR-2 AP. Furthermore, the tryptase-stimulated proliferation of DLD-1 was concentration-dependently inhibited by nafamostat mesilate, a specific inhibitor of tryptase. These results as a whole indicated that tryptase has proliferative effects on DLD-1 through cyclooxygenase- and MAP kinase-dependent manners acting on PAR-2 by its proteolytic activity.
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PMID:Mast cell tryptase stimulates DLD-1 carcinoma through prostaglandin- and MAP kinase-dependent manners. 1609 13

Human airway trypsin-like protease (HAT) was isolated from airway secretions and localized to bronchial epithelial cells by immunohistochemistry. In the present study, we examined whether HAT could stimulate DNA synthesis and proliferation of primary human bronchial fibroblasts (HBF). HAT significantly stimulated the proliferation of HBF by 20-55%, a level similar to that of the mitogenic activity of lung mast cell tryptase (MCT). HAT also stimulated the incorporation of [3H]thymidine in HBF, and this HAT-induced DNA synthesis was abolished by leupeptin. Protease-activated receptor-2 (PAR-2) mRNA was expressed and localized to the cell surface in HBF. PAR-2 activating peptide (AP) also enhanced DNA synthesis, and both HAT and PAR-2 AP induced receptor internalization, similar to the response to trypsin. Pretreatment of HBF with anti-PAR-2 antibody significantly suppressed both HAT and PAR-2 AP-induced DNA synthesis. In addition, HAT and PAR-2 AP induced intracellular Ca2+ mobilization in HBF. The HAT-induced increase in Ca2+ was desensitized by pretreatment with trypsin or PAR-2 AP. U0126, a specific MAPK inhibitor, completely inhibited HAT-induced DNA synthesis as well as HAT-induced phosphorylation of MAPK. The effect of HAT and MCT together was additive, whereas the effect of HAT and insulin together on HBF DNA synthesis was synergistic. These results indicate that HAT stimulates fibroblast proliferation in bronchial airways through a PAR-2-dependent MEK-MAPK mediated pathway and that HAT is linked to airway processes involving fibroblasts.
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PMID:Human airway trypsin-like protease stimulates human bronchial fibroblast proliferation in a protease-activated receptor-2-dependent pathway. 1619 37