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

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neutrophils exposed to low concentrations of gram-negative lipopolysaccharide (LPS) become primed and have an increased oxidative response to a second stimulus (e.g., formyl-methionyl-leucyl-phenylalanine [fMLP]). In studies aimed at understanding newborn sepsis, we have shown that neutrophils of newborns are not primed in response to LPS. To further understand the processes involved in LPS-mediated priming of neutrophils, we explored the role of extracellular signal-related protein kinases (ERK 1 and 2) of the mitogen-activated protein kinase family. We found that LPS activated ERK 1 and 2 in cells of both adults and newborns and that activation was plasma dependent (maximal at > or =5%) through LPS-binding protein. Although fibronectin in plasma is required for LPS-mediated priming of neutrophils of adults assessed by fMLP-triggered oxidative burst, it was not required for LPS-mediated activation of ERK 1 and 2. LPS-mediated activation was dose and time dependent; maximal activation occurred with approximately 5 ng of LPS per ml and at 10 to 40 min. We used the inhibitor PD 98059 to study the role of ERK 1 and 2 in the LPS-primed fMLP-triggered oxidative burst. While Western blotting showed that 100 microM PD 98059 completely inhibited LPS-mediated ERK activation, oxidative response to fMLP by a chemiluminescence assay revealed that the same concentration inhibited the LPS-primed oxidative burst by only 40%. We conclude that in neutrophils, LPS-mediated activation of ERK 1 and 2 requires plasma and that this activation is not dependent on fibronectin. In addition, we found that the ERK pathway is not responsible for the lack of LPS priming in neutrophils of newborns but may be required for 40% of the LPS-primed fMLP-triggered oxidative burst in cells of adults.
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PMID:Activation of extracellular signal-related protein kinases 1 and 2 of the mitogen-activated protein kinase family by lipopolysaccharide requires plasma in neutrophils from adults and newborns. 1129 34

Blood vessels are continuously exposed to mechanical forces that lead to adaptive remodeling and atherosclerosis. Although there have been many studies characterizing the responses of vascular cells to mechanical stimuli, the precise mechanical characteristics of the forces applied to cells to elicit these responses are not clear. We designed a magnetic exposure system capable of producing a defined normal force on ferromagnetic beads that are specifically bound to cultured cells coated with extracellular matrix proteins or integrin-specific antibodies. Rat aortic smooth muscle cells were incubated with engineered fibronectin-coated ferromagnetic beads and then exposed to a magnetic field. With activation of extracellular signal-regulated mitogen-activated protein kinase 1/2 (ERK 1/2(MAPK)) used as a prototypical marker for cell responsiveness to mechanical forces, Western blot analysis demonstrated an increase in phosphorylated ERK 1/2(MAPK) expression reaching a maximal response of a 3.5-fold increase at a total force of approximately 2.5 pN per cell. The peak response occurred after 5 minutes of exposure and slowly decreased to baseline after 30 minutes. A cyclic, rather than static, force was required for this activation, and the frequency-response curve increased approximately 2-fold between 0.5 and 2.0 HZ: Vitronectin- and beta(3) antibody-coated beads showed a response nearly identical to those coated with engineered fibronectin, whereas forces applied to beads coated with alpha(2) and beta(1) antibodies did not significantly activate ERK 1/2(MAPK). Mechanical activation of the ERK 1/2(MAPK) system in rat aortic smooth muscle cells occurs through specific integrin receptors and requires a cyclic force with a magnitude estimated to be in the piconewton range.
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PMID:Integrin-mediated mechanotransduction in vascular smooth muscle cells: frequency and force response characteristics. 1130 89

The expression of vascular endothelial growth factor (VEGF) by breast tumors has been previously correlated with a poor prognosis in the pathogenesis of breast cancer. Furthermore, VEGF secretion is a prerequisite for tumor development. Although most of the effects of VEGF have been shown to be attributable to the stimulation of endothelial cells, we present evidence here that breast tumor cells are capable of responding to VEGF. We show that VEGF stimulation of T-47D breast cancer cells leads to changes in cellular signaling and invasion. VEGF increases the cellular invasion of T-47D breast cancer cells on Matrigel/ fibronectin-coated transwell membranes by a factor of two. Northern analysis for the expression of the known VEGF receptors shows the presence of moderate levels of Flt-1 and low levels of Flk-1/KDR mRNAs in a variety of breast cancer cell lines. T-47D breast cancer cells bind 125I-labeled VEGF with a Kd of 13 x 10(-9) M. VEGF induces the activation of the extracellular regulated kinases 1,2 as well as activation of phosphatidylinositol 3'-kinase, Akt, and Forkhead receptor L1. These findings in T-47D breast cancer cells strongly suggest an autocrine role for VEGF contributing to the tumorigenic phenotype.
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PMID:Role of vascular endothelial growth factor in the stimulation of cellular invasion and signaling of breast cancer cells. 1130 13

The activities of extracellular signal-regulated kinases (ERK1/ERK2) is required for proliferation of several types of cells. The performed analysis showed stimulation of ERK's by fetal calf serum (FCS) or fibronectin in the C3H 10T1/2 cell cultures at logarithmic phase of growth. The ERKs activity was not stimulated in confluent cells. This could not be accounted for a partial down regulation of ERK since its level was stable in both types of cells regardless of their density and kind of stimulation. Searching for ERK up-stream elements we studied the integrin receptor gene transcript by RT-PCR and focal adhesion kinase (FAK) by Western blotting and phosphorylation assays. It was found that FCS and fibronectin stimulated phosphorylating activity of FAK in the cells at the logarithmic phase of growth, but were inefficient in the confluent cells. RT-PCR showed the presence of alpha5 and beta1 integrin transcripts, and p125FAK was at the same level regardless of the type of stimulation. These data indicate that the ability of FAK to be activated plays an important role in ERK regulation and, in consequence in proliferation and growth inhibition during confluence.
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PMID:Signal transduction in confluent C3H 10T1/2 cells. The role of focal adhesion kinase. 1144 Jan 67

We report a method of purifying, characterizing and expanding endothelial cells (ECs) derived from CD133(+) bone marrow cells, a subset of CD34(+) haematopoietic progenitors. Isolated using immunomagnetic sorting (mean purity 90 +/- 5%), the CD133(+) bone marrow cells were grown on fibronectin-coated flasks in M199 medium supplemented with fetal bovine serum (FBS), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and insulin growth factor (IGF-1). The CD133(+) fraction contained 95 +/- 4% CD34(+) cells, 3 +/- 2% cells expressing VEGF receptor (VEGFR-2/KDR), but did not express von Willebrand factor (VWF), VE-cadherin, P1H12 or TE-7. After 3 weeks of culture, the cells formed a monolayer with a typical EC morphology and expanded 11 +/- 5 times. The cells were further purified using Ulex europaeus agglutinin-1 (UEA-1)-fluorescein isothiocyanate (FITC) and anti-FITC microbeads, and expanded with VEGF for a further 3 weeks. All of the cells were CD45(-) and CD14(-), and expressed several endothelial markers (UEA-1, VWF, P1H12, CD105, E-selectin, VCAM-1 and VE-cadherin) and typical Weibel-Palade bodies. They had a high proliferative potential (up to a 2400-fold increase in cell number after 3 weeks of culture) and the capacity to modulate cell surface antigens upon stimulation with inflammatory cytokines. Purified ECs were also co-cultivated with CD34(+) cells, in parallel with a purified fibroblastic cell monolayer. CD34(+) cells (10 x 10(5)) gave rise to 17,951 +/- 2422 CFU-GM colonies when grown on endothelial cells, and to 12,928 +/- 4415 CFU-GM colonies on fibroblast monolayers. The ECs also supported erythroid blast-forming unit (BFU-E) colonies better. These results suggest that bone marrow CD133(+) progenitor cells can give rise to highly purified ECs, which have a high proliferative capacity, can be activated by inflammatory cytokines and are superior to fibroblasts in supporting haematopoiesis. Our data support the hypothesis that endothelial cell progenitors are present in adult bone marrow and may contribute to neo-angiogenesis.
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PMID:Differentiation and expansion of endothelial cells from human bone marrow CD133(+) cells. 1172 32

In multiple myeloma (MM), migration is necessary for the homing of tumor cells to bone marrow (BM), for expansion within the BM microenvironment, and for egress into the peripheral blood. In the present study we characterize the role of vascular endothelial growth factor (VEGF) and beta(1) integrin (CD29) in MM cell migration. We show that protein kinase C (PKC) alpha is translocated to the plasma membrane and activated by adhesion of MM cells to fibronectin and VEGF. We identify beta(1) integrin modulating VEGF-triggered MM cell migration on fibronectin. We show that transient enhancement of MM cell adhesion to fibronectin triggered by VEGF is dependent on the activity of both PKC and beta(1) integrin. Moreover, we demonstrate that PKC alpha is constitutively associated with beta(1) integrin. These data are consistent with PKC alpha-dependent exocytosis of activated beta(1) integrin to the plasma membrane, where its increased surface expression mediates binding to fibronectin; conversely, catalytically active PKC alpha-driven internalization of beta(1) integrin results in MM cell de-adhesion. We show that the regulatory subunit of phosphatidylinositol (PI) 3-kinase (p85) is constitutively associated with FMS-like tyrosine kinase-1 (Flt-1). VEGF stimulates activation of PI 3-kinase, and both MM cell adhesion and migration are PI 3-kinase-dependent. Moreover, both VEGF-induced PI 3-kinase activation and beta(1) integrin-mediated binding to fibronectin are required for the recruitment and activation of PKC alpha. Time-lapse phase contrast video microscopy (TLVM) studies confirm the importance of these signaling components in VEGF-triggered MM cell migration on fibronectin.
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PMID:Vascular endothelial growth factor-induced migration of multiple myeloma cells is associated with beta 1 integrin- and phosphatidylinositol 3-kinase-dependent PKC alpha activation. 1175 5

Evidence suggests that the arachidonic acid metabolite of 12-lipoxygenase, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), not only mediates the effects of angiotensin II (AngII), but also has direct effects on hypertrophy and matrix protein production in vascular smooth muscle cells (VSMCs). This study is aimed at identifying the signaling pathways involved in these events. Treatment of porcine VSMCs with 12(S)-HETE led to the activation of Ras and p38 MAPK. It also stimulated phosphorylation, DNA-binding activity, and transactivation of the transcription factor cAMP response element (CRE)-binding protein. In addition, 12(S)-HETE induced transcription from a fibronectin promoter containing multiple CREs. AngII also induced transactivation of CRE-binding protein and transcription from the fibronectin promoter. A specific p38 MAPK inhibitor (SB202190) as well as a dominant-negative Ras mutant (Ras-N17) blocked both 12(S)-HETE and AngII effects. In addition, inhibitors of lipoxygenase also blocked AngII effects. Both 12(S)-HETE and AngII increased cellular hypertrophy with similar potency, and this was significantly blocked by SB202190. Stable overexpression of murine leukocyte-type 12/15-lipoxygenase in VSMCs increased the levels of cell-associated 12(S)-HETE as well as basal activity of both ERK and p38 MAPKs. Furthermore, these 12-lipoxygenase-overexpressing cells displayed significantly greater cellular hypertrophy relative to mock-transfected cells. These results show for the first time that oxidized lipids such as 12(S)-HETE can induce VSMC growth and matrix gene expression and mediate growth factor effects via activation of the Ras-MAPK pathway and key target transcription factors.
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PMID:The oxidized lipid and lipoxygenase product 12(S)-hydroxyeicosatetraenoic acid induces hypertrophy and fibronectin transcription in vascular smooth muscle cells via p38 MAPK and cAMP response element-binding protein activation. Mediation of angiotensin II effects. 1178 49

Cytosolic GTP-bound Ras has been shown to act as a dominant negative (DN) inhibitor of Ras by sequestering Raf in non-productive cytosolic complexes. Nevertheless, this distinct class of DN mutants has been neither well characterized nor extensively used to analyze Ras signaling. In contrast, DN Ras17N, which functions by blocking Ras guanine nucleotide exchange factors, has been well characterized and is widely used. Cytosolic GTP-bound Ras mutants could be used to inhibit particular Ras effectors by introducing additional mutations (T35S, E37G or Y40C) that permit them to associate selectively with and inhibit Raf, RalGDS, or phosphoinositide 3-kinase, respectively. When the wild-type Ras effector binding region is used, cytosolic Ras should associate with all Ras effectors, even those that are not yet identified, making these DN Ras mutants effective inhibitors of multiple Ras functions. We generated cytosolic GTP-bound H-, N-, and K-Ras, and we assessed their ability to inhibit Ras-induced phenotypes. In fibroblasts, cytosolic H-, N-, and K-Ras inhibited Ras-induced Elk-1 activation and focus formation, induced a flattened cell morphology, and increased adhesion to fibronectin through modulation of a beta(1)-subunit-containing integrin, thereby demonstrating that DN activity is not limited to a subset of Ras isoforms. We also generated cytosolic GTP-bound Ras effector domain mutants (EDMs), each of which reduced the ability of cytosolic GTP-bound Ras proteins to inhibit Elk-1 activation and to induce cell flattening, implicating multiple pathways in these phenotypes. In contrast, Ras-induced focus formation, platelet-derived growth factor (PDGF)-, or Ras-induced phospho-Akt levels and cell adhesion to fibronectin were affected by T35S and Y40C EDMs, whereas PDGF- or Ras-induced phospho-Erk levels were affected only by the T35S EDM, implying that a more limited set of Ras-mediated pathways participate in these phenotypes. These data constitute the first extensive characterization of this functionally distinct class of DN Ras inhibitor proteins.
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PMID:A distinct class of dominant negative Ras mutants: cytosolic GTP-bound Ras effector domain mutants that inhibit Ras signaling and transformation and enhance cell adhesion. 1179 8

Cas-family proteins have been implicated as signaling intermediaries in diverse processes including cellular attachment, motility, growth factor response, apoptosis and oncogenic transformation. The three defined Cas-family members (p130Cas, HEF1/Cas-L and Efs/Sin) are subject to multiple forms of regulation (including cell-cycle- and cell-attachment-mediated post-translational modification and cleavage) that complicate elucidation of the function of specific Cas proteins in defined biological processes. To explore the biological role of HEF1 further, we have developed a series of cell lines in which HEF1 production is regulated by an inducible promoter. In this system, HEF1 production rapidly induces changes in cellular morphology and motility, enhancing cell speed and haptotaxis towards fibronectin in a process partially dependent on intact ERK and p38 MAPK signaling pathways. Finally, cDNA expression array analysis and subsequent studies indicate that HEF1 production increases levels of mRNA transcripts encoding proteins that are associated with motility, cell transformation and invasiveness, including several metalloproteinases, MLCK, p160ROCK and ErbB2. Upregulation of such proteins suggests mechanisms through which misregulation of HEF1 may be involved in cancer progression.
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PMID:Dissection of HEF1-dependent functions in motility and transcriptional regulation. 1180 28

Tissue transglutaminase (tTG) has recently been established as a novel cell surface adhesion protein that binds with high affinity to fibronectin in the pericellular matrix. In this study, we have made use of this property to enhance the biocompatibility of poly(epsilon-caprolactone) (PCL), a biomaterial currently used in bone repair. Poly(epsilon-caprolactone) discs were first coated with fibronectin and then tTG. The surface localisation of the two proteins was confirmed using ELISA and the tTG shown to be active on the surface by incorporation of biotin cadaverine into the fibronectin coating. When human osteoblasts (HOBs) were seeded onto the coated polymer surfaces in serum free medium, the surface coated with fibronectin and then tTG showed an increase in the spreading of the cells as compared to the surface coated with fibronectin alone, when analysed using environmental scanning electron microscopy. The presence of tTG had no effect on HOB cell differentiation when analysed by determining alkaline phosphatase activity. The use of tTG as a novel adhesion protein in this way may therefore have considerable potential in forming a stable tissue/biomaterial interface for application in medical devices.
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PMID:Involvement of tissue transglutaminase in the stabilisation of biomaterial/tissue interfaces important in medical devices. 1182 48


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