Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cell migration is modulated by regulatory molecules such as growth factors, oncogenes, and the tumor suppressor PTEN. We previously described inhibition of cell migration by PTEN and restoration of motility by focal adhesion kinase (FAK) and p130 Crk-associated substrate (p130(Cas)). We now report a novel pathway regulating random cell motility involving Shc and mitogen-activated protein (MAP) kinase, which is downmodulated by PTEN and additive to a FAK pathway regulating directional migration. Overexpression of Shc or constitutively activated MEK1 in PTEN- reconstituted U87-MG cells stimulated integrin- mediated MAP kinase activation and cell migration. Conversely, overexpression of dominant negative Shc inhibited cell migration; Akt appeared uninvolved. PTEN directly dephosphorylated Shc. The migration induced by FAK or p130(Cas) was directionally persistent and involved extensive organization of actin microfilaments and focal adhesions. In contrast, Shc or MEK1 induced a random type of motility associated with less actin cytoskeletal and focal adhesion organization. These results identify two distinct, additive pathways regulating cell migration that are downregulated by tumor suppressor PTEN: one involves Shc, a MAP kinase pathway, and random migration, whereas the other involves FAK, p130(Cas), more extensive actin cytoskeletal organization, focal contacts, and directionally persistent cell motility. Integration of these pathways provides an intracellular mechanism for regulating the speed and the directionality of cell migration.
...
PMID:Shc and FAK differentially regulate cell motility and directionality modulated by PTEN. 1042 92

This study was initiated to identify signaling proteins used by the receptors for vascular endothelial cell growth factor KDR/Flk1, and Flt1. Two-hybrid cloning and immunoprecipitation from human umbilical vein endothelial cells (HUVEC) showed that KDR binds to and promotes the tyrosine phosphorylation of phospholipase Cgamma (PLCgamma). Neither placental growth factor, which activates Flt1, epidermal growth factor (EGF), or fibroblast growth factor (FGF) induced tyrosine phosphorylation of PLCgamma, indicating that KDR is uniquely important to PLCgamma activation in HUVEC. By signaling through KDR, VEGF promoted the tyrosine phosphorylation of focal adhesion kinase, induced activation of Akt, protein kinase Cepsilon (PKCepsilon), mitogen-activated protein kinase (MAPK), and promoted thymidine incorporation into DNA. VEGF activates PLCgamma, PKCepsilon, and phosphatidylinositol 3-kinase independently of one another. MEK, PLCgamma, and to a lesser extent PKC, are in the pathway through which KDR activates MAPK. PLCgamma or PKC inhibitors did not affect FGF- or EGF-mediated MAPK activation. MAPK/ERK kinase inhibition diminished VEGF-, FGF-, and EGF-promoted thymidine incorporation into DNA. However, blockade of PKC diminished thymidine incorporation into DNA induced by VEGF but not FGF or EGF. Signaling through KDR/Flk1 activates signaling pathways not utilized by other mitogens to induce proliferation of HUVEC.
...
PMID:Utilization of distinct signaling pathways by receptors for vascular endothelial cell growth factor and other mitogens in the induction of endothelial cell proliferation. 1067 53

The signal transduction pathways associated with neural cell adhesion molecule (NCAM)-induced neuritogenesis are only partially characterized. We here demonstrate that NCAM-induced neurite outgrowth depends on activation of p59(fyn), focal adhesion kinase (FAK), phospholipase Cgamma (PLCgamma), protein kinase C (PKC), and the Ras-mitogen-activated protein (MAP) kinase pathway. This was done using a coculture system consisting of PC12-E2 cells grown on fibroblasts, with or without NCAM expression, allowing NCAM-NCAM interactions resulting in neurite outgrowth. PC12-E2 cells were transiently transfected with expression plasmids encoding constitutively active forms of Ras, Raf, MAP kinase kinases MEK1 and 2, dominant negative forms of Ras and Raf, and the FAK-related nonkinase. Alternatively, PC12-E2 cells were submitted to treatment with antibodies to the fibroblast growth factor (FGF) receptor, inhibitors of the nonreceptor tyrosine kinase p59(fyn), PLC, PKC and MEK and an activator of PKC, phorbol-12-myristate-13-acetate (PMA). MEK2 transfection rescued cells treated with all inhibitors. The same was found for PMA treatment, except when cells concomitantly were treated with the MEK inhibitor. Arachidonic acid rescued cells treated with antibodies to the FGF receptor or the PLC inhibitor, but not cells in which the activity of PKC, p59(fyn), FAK, Ras, or MEK was inhibited. Interaction of NCAM with a synthetic NCAM peptide ligand, known to induce neurite outgrowth, was shown to stimulate phosphorylation of the MAP kinases extracellular signal-regulated kinases ERK1 and ERK2. The MAP kinase activation was sustained, because ERK1 and ERK2 were phosphorylated in PC12-E2 cells and primary hippocampal neurons even after 24 hr of cultivation on NCAM-expressing fibroblasts. Based on these results, we propose a model of NCAM signaling involving two pathways: NCAM-Ras-MAP kinase and NCAM-FGF receptor-PLCgamma-PKC, and we propose that PKC serves as the link between the two pathways activating Raf and thereby creating the sustained activity of the MAP kinases necessary for neuronal differentiation.
...
PMID:Neural cell adhesion molecule-stimulated neurite outgrowth depends on activation of protein kinase C and the Ras-mitogen-activated protein kinase pathway. 1070 99

Urokinase-type plasminogen activator (uPA) stimulates MCF-7 cell migration by binding to the UPA receptor and activating the Ras-extracellular signal-regulated kinase (Ras-ERK) signaling pathway. Studies presented here show that soluble uPA receptor and a peptide derived from the linker region between domains 1 and 2 of the uPA receptor also stimulate cellular migration via a mitogen-activated protein kinase/ERK kinase (MEK)-dependent pathway. Signaling proteins that function upstream of Ras in uPA- stimulated cells remain undefined. To address this problem, we transfected MCF-7 cells to express the noncatalytic carboxylterminal domain of focal adhesion kinase (FAK), FAK(Y397F), kinase-defective c-Src, or Shc FFF, all of which express dominant-negative activity. In each case, ERK phosphorylation and cellular migration in response to uPA were blocked. Both activities were rescued by co-transfecting the cells to express constitutively active MEK1, indicating that FAK, c-Src, and Shc are upstream of MEK. Shc was tyrosine-phosphorylated in uPA-treated cells. The level of phosphorylated Shc was increased within 1 min and remained increased for at least 30 min. Sos co-immunoprecipitated with Shc in cells that were treated with uPA for 1-2.5 min, probably reflecting the formation of Shc-Grb2/Sos complex; however, by 10 min, co-immunoprecipitation of Sos with Shc was no longer observed. Rapid dissociation of Sos from Shc represents a possible mechanism for the transient phosphorylation of ERK in uPA-treated MCF-7 cells.
...
PMID:Urokinase-type plasminogen activator stimulates the Ras/Extracellular signal-regulated kinase (ERK) signaling pathway and MCF-7 cell migration by a mechanism that requires focal adhesion kinase, Src, and Shc. Rapid dissociation of GRB2/Sps-Shc complex is associated with the transient phosphorylation of ERK in urokinase-treated cells. 1077 11

The rat pheochromocytoma cell line PC12 is extensively used as a model for studies of neuronal cell differentiation. These cells develop a sympathetic neuron-like phenotype when cultured in the presence of nerve growth factor. The present study was performed in order to assess the role of mouse GTK (previously named BSK/IYK), a cytoplasmic tyrosine kinase belonging to the Src family, for neurite outgrowth in PC12 cells. We report that PC12 cells stably overexpressing GTK exhibit a larger fraction of cells with neurites as compared with control cells, and this response is not accompanied by an increased ERK activity. Treatment of the cells with the MEK inhibitor PD98059 did not reduce the GTK-dependent increased in neurite outgrowth. GTK expression induces a nerve growth factor-independent Rap1 activation, probably through altered CrkII signaling. We observe increased CrkII complex formation with p130(Cas), focal adhesion kinase (FAK), and Shb in PC12-GTK cells. The expression of GTK also correlates with a markedly increased content of FAK, phosphorylation of the adaptor protein Shb, and an association between these two proteins. Transient transfection of GTK-overexpressing cells with RalGDS-RBD or Rap1GAP, inhibitors of the Rap1 pathway, reduces the GTK-dependent neurite outgrowth. These data suggest that GTK participates in a signaling pathway, perhaps involving Shb, FAK and Rap1, that induces neurite outgrowth in PC12 cells.
...
PMID:GTK, a Src-related tyrosine kinase, induces nerve growth factor-independent neurite outgrowth in PC12 cells through activation of the Rap1 pathway. Relationship to Shb tyrosine phosphorylation and elevated levels of focal adhesion kinase. 1087 15

Plasminogen activator inhibitor 1 (PAI-1) is a major inhibitor of urokinase-type plasminogen activator (uPA). In this study, we explored the role of PAI-1 in cell signaling. In MCF-7 cells, PAI-1 did not directly activate the mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase (ERK) 1 and ERK2, but instead altered the response to uPA so that ERK phosphorylation was sustained. This effect required the cooperative function of uPAR and the very low density lipoprotein receptor (VLDLr). When MCF-7 cells were treated with uPA-PAI-1 complex in the presence of the VLDLr antagonist, receptor-associated protein, or with uPA-PAI-1(R76E) complex, which binds to the VLDLr with greatly decreased affinity, transient ERK phosphorylation (<5 min) was observed, mimicking the uPA response. ERK phosphorylation was not induced by tissue-type plasminogen activator-PAI-1 complex or by uPA-PAI-1 complex in the presence of antibodies that block uPA binding to uPAR. uPA-PAI-1 complex induced tyrosine phosphorylation of focal adhesion kinase and Shc and sustained association of Sos with Shc, whereas uPA caused transient association of Sos with Shc. By sustaining ERK phosphorylation, PAI-1 converted uPA into an MCF-7 cell mitogen. This activity was blocked by receptor-associated protein and not observed with uPA-PAI-1(R76E) complex, demonstrating the importance of the VLDLr. uPA promoted the growth of other cells in which ERK phosphorylation was sustained, including beta3 integrin overexpressing MCF-7 cells and HT 1080 cells. The MEK inhibitor, PD098059, blocked the growth-promoting activity of uPA and uPA-PAI-1 complex in these cells. Our results demonstrate that PAI-1 may regulate uPA-initiated cell signaling by a mechanism that requires VLDLr recruitment. The kinetics of ERK phosphorylation in response to uPAR ligation determine the function of uPA and uPA-PAI-1 complex as growth promoters.
...
PMID:Plasminogen activator inhibitor 1 functions as a urokinase response modifier at the level of cell signaling and thereby promotes MCF-7 cell growth. 1126 65

Treatment of cultured human hepatoma HepG2 cells with the protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), results in an increase in tyrosine phosphorylation of several proteins, including the focal adhesion kinase (FAK) and paxillin using anti-phosphotyrosine Western blotting and immunoprecipitation. However, when cells are in suspension or in the presence of cytochalasin D which disrupts the intracellular network of actin microfilaments, TPA loses its ability to stimulate tyrosine phosphorylation of FAK and paxillin but it still activates mitogen-activated protein kinase (MAPK) and induces PKC translocation from cytosol to the membrane in HepG2 cells. On the other hand, PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, blocks TPA-induced MAPK activation but has no effect on TPA-induced tyrosine phosphorylation. Our findings suggest that TPA-induced tyrosine phosphorylation of FAK and paxillin in human hepatoma cells is PKC dependent and requires the integrity of the cell cytoskeleton but is uncoupled to the signal transduction pathway of PKC leading to the translocation of PKC and MAPK activation.
...
PMID:Protein kinase C-mediated tyrosine phosphorylation of paxillin and focal adhesion kinase requires cytoskeletal integrity and is uncoupled to mitogen-activated protein kinase activation in human hepatoma cells. 1128 49

Elevated focal adhesion kinase (FAK) expression in human tumor cells has been correlated with an increased cell invasion potential. In cell culture, studies with FAK-null fibroblasts have shown that FAK function is required for cell migration. To determine the role of elevated FAK expression in facilitating epidermal growth factor (EGF)-stimulated human adenocarcinoma (A549) cell motility, antisense oligonucleotides were used to reduce FAK protein expression >75%. Treatment of A549 cells with FAK antisense (ISIS 15421) but not a mismatched control (ISIS 17636) oligonucleotide resulted in reduced EGF-stimulated p130(Cas)-Src complex formation, c-Jun NH(2)-terminal kinase (JNK) activation, directed cell motility, and serum-stimulated cell invasion through Matrigel. Because residual FAK protein in ISIS 15421-treated A549 cells was highly phosphorylated at the Tyr-397/Src homology (SH)2 binding site, expression of the FAK COOH-terminal domain (FRNK) was also used as an inhibitor of FAK function. Adenoviral-mediated infection and expression of FRNK promoted FAK dephosphorylation at Tyr-397, resulted in reduced EGF-stimulated JNK as well as extracellular-regulated kinase 2 (ERK2) kinase activation, inhibited matrix metalloproteinase-9 (MMP-9) secretion, and potently blocked both random and EGF-stimulated A549 cell motility. Equivalent expression of a FRNK (S-1034) point-mutant that did not promote FAK dephosphorylation also did not affect EGF-stimulated signaling or cell motility. Dose-dependent reduction in EGF-stimulated A549 motility was observed with the PD98059 MEK1 inhibitor and the batimastat (BB-94) inhibitor of MMP activity, but not with the SB203580 inhibitor of p38 kinase. Finally, comparisons between normal, FAK-null, and FAK-reconstituted fibroblasts revealed that FAK enhanced EGF-stimulated JNK and ERK2 kinase activation that was required for cell motility. These data indicate that FAK functions as an important signaling platform to coordinate EGF-stimulated cell migration in human tumor cells and support a role for inhibitors of FAK expression or activity in the control of neoplastic cell invasion.
...
PMID:Inhibition of focal adhesion kinase expression or activity disrupts epidermal growth factor-stimulated signaling promoting the migration of invasive human carcinoma cells. 1158 39

The 29-kDa amino-terminal fibronectin fragment (FN-f) has a potent chondrolytic effect and is thought to be involved in cartilage degradation in arthritis. However, little is known about signal transduction pathways that are activated by FN-f. Here we demonstrated that FN-f induced nitric oxide (NO) production from human articular chondrocytes. Expression of inducible nitric-oxide synthase (iNOS) mRNA and NO production were observed at 6 and 48 h after FN-f treatment, respectively. Interleukin-1beta (IL-1beta) mRNA up-regulation was stimulated by FN-f in human chondrocytes. To address the possibility that FN-f-induced NO release is mediated by IL-1beta production, the effect of IL-1 receptor antagonist (IL-1ra) was determined. IL-1ra partially inhibited FN-f-induced NO release although it almost completely inhibited IL-1beta-induced NO release. Tyrosine phosphorylation of focal adhesion kinase was induced transiently by FN-f treatment. Blocking antibodies to alpha(5) or beta(1) integrin and Arg-Gly-Asp-containing peptides did not inhibit FN-f-induced NO production. PP2, a Src family kinase inhibitor, or cytochalasin D, which selectively disrupts the network of actin filaments, inhibited both FAK phosphorylation and NO production induced by FN-f, but the phosphatidylinositol 3-kinase inhibitor wortmannin had no effect. Analysis of mitogen-activated protein kinases (MAPK) showed activation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase, and p38 MAPK. High concentrations of SB203580, which inhibit both JNK and p38 MAPK, and PD98059 a selective inhibitor of MEK1/2 that blocks ERK activation, inhibited FN-f induced NO production. These data suggest that focal adhesion kinase and MAPK mediate FN-f induced activation of human articular chondrocytes.
...
PMID:Focal adhesion kinase and mitogen-activated protein kinases are involved in chondrocyte activation by the 29-kDa amino-terminal fibronectin fragment. 1167 48

Integrins, major adhesion receptors and angiotensin II activate extracellular signal-regulated kinase (ERK) pathways and result in a mitogenic response such as the proliferation of vascular smooth muscle cells (VSMCs). We investigated mechanisms of collaboration or synergism between integrins and angiotensin II involving ERK pathways in VSMCs. Integrin activation by cell adhesion to fibronectin increased the phosphorylation level of focal adhesion kinase (FAK) upstream of the ERK pathway. angiotensin II induced a high increase in the phosphorylation level of FAK with integrin activation, but not in suspended cells. Integrin activation increased phosphorylation levels of ERK kinase (MEK) and ERK phosphorylation as well. Angiotensin II-induced MEK and ERK phosphorylation were retained even in suspended cells. Furthermore, with integrin activation, angiotensin II induced a much larger increase in the phosphorylation levels of MEK and ERK. These results suggest that simultaneous stimulation of integrin and angiotensin II receptors cause synergistic interaction in the activation of ERK pathway, possibly via phosphorylation of FAK, which may play a critical role in angiotensin II-mediated mitogenic response in VSMCs.
...
PMID:Synergistic interaction of integrin and angiotensin II in activation of extracellular signal-regulated kinase pathways in vascular smooth muscle cells. 1181 61


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---