Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dual-specificity MAPK phosphatase MKP-1/CL100/DUSP1 is an inducible nuclear protein controlled by p44/42 MAPK (ERK1/2) in a negative feedback mechanism to inhibit kinase activity. Here, we report on the molecular basis for a novel positive feedback mechanism to sustain ERK activation by triggering MKP-1 proteolysis. Active ERK2 docking to the DEF motif (FXFP, residues 339-342) of N-terminally truncated MKP-1 in vitro initiated phosphorylation at the Ser(296)/Ser(323) domain, which was not affected by substituting Ala for Ser at Ser(359)/Ser(364). The DEF and Ser(296)/Ser(323) sites were essential for ubiquitin-mediated MKP-1 proteolysis stimulated by MKK1-ERK signaling in H293 cells, whereas the N-terminal domain and Ser(359)/Ser(364) sites were dispensable. ERK activation by serum increased the endogenous level of ubiquitinated phospho-Ser(296) MKP-1 and the degradation of MKP-1. Intriguingly, active ERK-promoted phospho-Ser(296) MKP-1 bound to SCF(Skp2) ubiquitin ligase in vivo and in vitro. Forced expression of Skp2 enhanced MKP-1 polyubiquitination and proteolysis upon ERK activation, whereas depletion of endogenous Skp2 suppressed such events. The kinetics of ERK signaling stimulated by serum correlated with the endogenous MKP-1 degradation rate in a Skp2-dependent manner. Thus, MKP-1 proteolysis can be achieved via ERK and SCF(Skp2) cooperation, thereby sustaining ERK activation.
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PMID:Cooperation of ERK and SCFSkp2 for MKP-1 destruction provides a positive feedback regulation of proliferating signaling. 1628 70

Gliosarcomas are rare and poorly characterized malignant brain tumors that exhibit a biphasic tissue pattern with areas of gliomatous and sarcomatous differentiation. These tumors are histological variants of glioblastoma, displaying a similar genetic profile and dismal prognosis. Up-regulation of PDGFR subfamily of tyrosine kinase members, PDGFR-alpha and c-Kit, and their intracellular effectors RAS/RAF/MAPK has a crucial role in the cancer development. In addition, signal transduction mediated by activating mutations of c-Kit and PDGFR can be effectively blocked by specific tyrosine kinase inhibitors, such as Imatinib mesylate. The aim of this study was to characterize the molecular alterations of PDGFR signaling in gliosarcomas. Six cases were analyzed by immunohistochemistry for the expression of PDGFR-alpha, c-Kit and their ligands PDGF-A and SCF, respectively. The cases were further evaluated for the presence of activating mutations of PDGFR-alpha (exons 12 and 18) and c-kit (exons 9, 11, 13, and 17), as well as B-RAF (exons 11 and 15). Expression of PDGF-A was found in all cases and co-expression of PDGFR-alpha was observed in three cases. Four cases showed expression of SCF, and c-Kit was observed only in one case that also expressed SCF. Generally, immunoreaction predominates in the glial component. The mutational analysis of PDGFR-alpha showed the presence of an IVS17-50insT intronic insertion in two cases, one of them also with a 2472C > T silent mutation; this silent mutation was also found in another case. Glioma cell line analysis of IVS17-50insT insertion showed no influence on PDGFR-alpha gene splicing. No mutations were detected in c-kit and B-RAF oncogenes. Our results indicate that activating mutations of PDGFR-alpha, c-kit and B-RAF are absent in gliosarcomas. Nevertheless, the presence of a PDGFR-a/PDGFA and c-Kit/SCF autocrine/paracrine stimulation loop in a proportion of cases, supports the potential role of specific tyrosine kinase inhibitors in the treatment of gliosarcomas.
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PMID:Molecular characterization of PDGFR-alpha/PDGF-A and c-KIT/SCF in gliosarcomas. 1637 64

The aim of this study was to investigate the biological characteristics of human bone marrow mesenchymal stem cells from bone marrow of different age donors. The experiments were divided into four groups by donors age, group A represented MSC derived from fetal bone marrow, group B represented MSC derived from bone marrow of 0-20 years old donors, group C represented MSC derived from bone marrow of 20-40 years old donors and group D represented MSC derived from bone marrow of donors older than 40. The growth, purification, proliferation and multipotential abilities of MSC in 4 groups were observed and their immunophenotypes were determined by flow-cytometry. The level of cytokines (IL-6, SCF, FLT-3L, SDF-1 and TGF-beta1) were assayed by ELISA method. Cell cycles were analyzed to show the proliferation index (PrI). MSCs derived from bone marrow of 4 groups were injected subcutaneous into NOD/SCID mouse to observe the safety. The results showed that different age donors bone marrow all gave rise to MSC. These cells were similar in morphology, antigenic phenotype, differentiation potential and cell cycle. The primary culture time of group B was shorter than other groups. The duration of passage 1 (P1) was 5.5 days, and the duration of P10 was 33 days, after P10 culture, (5.19 +/- 2.15) x 10(10) MSCs were obtained from 8 x 10(6) MNC of this group. The primary culture time of groups A, C, D were longer, the duration of P1 were 15, 7 and 13 days for group A, C and D respectively, and the duration of P10 was 50, 60 and 72 days for group A, C and D, respectively. After P10 culture, (4.98 +/- 2.08) x 10(10), (1.86 +/- 0.47) x 10(10), (0.64 +/- 0.22) x 10(10) MSCs were obtained from 8 x 10(6) MNC of group A, C and D respectively. The morphology of MSC of group A was longer and slender. The ability of expansion decreased after P15 for A group, P10 for B group and P8 for C and D groups. The levels of SCF, FLT3-L, IL-6 and SDF-1 in group B were higher than other groups. Karyotype analysis showed that MSCs from 4 groups were normal, and tumor-like tissues were not developed after cultured MSCs were inoculated in NOD/SCID mice. It is concluded that there was relationship between age and the biological characteristics of human bone marrow mesenchymal stem cells. For clinical use, especially in hematopoietic stem cell transplantation (HSCT), 0-20 years old donors were perfect MSCs donors who can provide sufficient MSCs in relatively short times. MSCs of group B can be used as stem cell source because the biological characteristics of MSCs of groups B are superior to that of other groups.
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PMID:[Age-related biological characteristics of human bone marrow mesenchymal stem cells from different age donors]. 1640 78

We established a leukemia cell line derived from therapy-related acute myeloid leukemia with the t(11;19) by xenotransplantation into the NOD/SCID mouse with IL-2Rgamma(c)-/- (NOG mouse). The cell line, TRL-01, could be serially transplanted from mouse to mouse and also grown in an adherence-dependent manner on a murine bone marrow stroma cell line, HESS-5. TRL-01 had the same immunophenotype as the original leukemia cells: positive for CD13, CD33, CD11a, CD18, CD29, CD49d, CD49e, CD54, CD62L, and CD117, and negative for CD3, CD4, CD8, CD19, CD34, CD41a, CD41b, CD135, and myeloperoxidase. Translocation (11;19)(q23;p13) in both the original sample and TRL-01 generated MLL-ENL chimeric transcripts joining exon 6 and exon 4, respectively, which has a novel isoform. In cultures of TRL-01, addition of GM-CSF, SCF, and G-CSF and adhesion to fibronectin-coated plates promoted transient proliferation and survival, although they did not support long-term culture. Subcutaneous injection caused a tumor to form only when HESS-5 was coinjected at the same site. These results suggest that TRL-01 is a useful cell line for studying not only the leukemia-related biology of MLL-ENL but also the intercellular association between leukemia and stroma.
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PMID:Establishment of a myeloid leukemia cell line, TRL-01, with MLL-ENL fusion gene. 1687 30

Activation through TCR/CD3-plus-CD28 induces primary T lymphocytes to enter S phase. Downregulation of cyclin-dependent kinase inhibitor p27(kip1) is critical in this process and is mediated by ubiquitin-targeted degradation of p27(kip1). Ubiquitination of p27(kip1) is performed by the SCF(skp2) ubiquitin ligase comprised of the core components Roc1, Cul1 and Skp1 and the substrate recognition components Skp2 and Cks1. Here we show that in primary human T lymphocytes, the SCF(skp2) core components Roc1, Cul1 and Skp1 are constitutively expressed, and their levels remain unchanged upon TCR/CD3-plus-CD28 costimulation. In contrast, the substrate recognition components Skp2 and Cks1 are almost undetectable in resting T cells and are transcriptionally induced upon costimulation. We determined that the SKP2 promoter lies directly upstream of the translational start site and contains binding sites for SP1, Elk-1 and E2F transcription factors. Mutagenesis of SP1 and Elk-1 sites abrogated TCR/CD3-plus-CD28-mediated SKP2 promoter-driven reporter activity, whereas mutagenesis of an E2F site enhanced reporter activity, suggesting that SKP2 promoter may act as a node of integration for mitogenic and anti-mitogenic signals. Thus, in primary T lymphocytes CD28 costimulation can directly regulate cell cycle progression by inducing transcription of the substrate recognition components of SCF(skp2) ubiquitin ligase that targets p27(kip1) for degradation.
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PMID:CD28 costimulation mediates transcription of SKP2 and CKS1, the substrate recognition components of SCFSkp2 ubiquitin ligase that leads p27kip1 to degradation. 1696 77

Tolerogenic dendritic cells (DCs) may be valuable in transplantation for silencing immune reaction. Macrophage colony-stimulating factor (M-CSF)/IL-4 induces differentiation of cord blood (CB) monocytes into DCs (M-DCs) with tolerogenic phenotype/function. We assessed whether factors produced by tolerogenic DCs could modulate hematopoiesis. TGF-beta1 added to CB M-DC cultures induced bona fide DC morphology (TGF-M-DCs), similar to that of DCs generated with TGF-beta and granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-4 (TGF-GM-DCs). Of conditioned media (CM) produced from TGF-M-DCs, TGF-GM-DCs, M-DCs, and GM-DCs, TGF-M-DC CM was the only one that enhanced SCF, Flt3 ligand, and TPO expansion of myeloid progenitor cells ex vivo. This effect was blocked by neutralizing anti-M-CSF Ab, but protein analysis of CM suggested that M-CSF alone was not manifesting enhanced expansion of myeloid progenitors. LPS-stimulated TGF-M-DCs induced T-cell tolerance/anergy as effectively as M-DCs. TGF-M-DCs secreted significantly lower concentrations of progenitor cell inhibitory cytokines and were less potent in activating T cells than TGF-GM-DCs. Functional differences between TGF-M-DCs and TGF-GM-DCs included enhanced responses to LPS-induced ERK, JNK, and P38 activation in TGF-M-DCs and their immune suppressive-skewed cytokine release profiles. TGF-M-DCs appear unique among culture-generated DCs in their capability for silencing immunity while promoting expansion of myeloid progenitors, events that may be of therapeutic value.
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PMID:TGF-beta combined with M-CSF and IL-4 induces generation of immune inhibitory cord blood dendritic cells capable of enhancing cytokine-induced ex vivo expansion of myeloid progenitors. 1758 53

E7080 is an orally active inhibitor of multiple receptor tyrosine kinases including VEGF, FGF and SCF receptors. In this study, we show the inhibitory activity of E7080 against SCF-induced angiogenesis in vitro and tumor growth of SCF-producing human small cell lung carcinoma H146 cells in vivo. E7080 inhibits SCF-driven tube formation of HUVEC, which express SCF receptor, KIT at the IC(50) value of 5.2 nM and it was almost identical for VEGF-driven one (IC(50) = 5.1 nM). To assess the role of SCF/KIT signaling in tumor angiogenesis, we evaluated the effect of imatinib, a selective KIT kinase inhibitor, on tumor growth of H146 cells in nude mice. Imatinib did not show the potent antitumor activity in vitro (IC(50) = 2,200 nM), because H146 cells did not express KIT. However, oral administration of imatinib at 160 mg/kg clearly slowed tumor growth of H146 cells in nude mice, accompanied by decreased microvessel density. Oral administration of E7080 inhibited tumor growth of H146 cells at doses of 30 and 100 mg/kg in a dose-dependent manner and caused tumor regression at 100 mg/kg. While anti-VEGF antibody also slowed tumor growth, it did not cause tumor regression. These results indicate that KIT signaling has a role in tumor angiogenesis of SCF-producing H146 cells, and E7080 causes regression of H146 tumors as a result of antiangiogenic activity mediated by inhibition of both KIT and VEGF receptor signaling. E7080 may provide therapeutic benefits in the treatment of SCF-producing tumors.
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PMID:E7080, a novel inhibitor that targets multiple kinases, has potent antitumor activities against stem cell factor producing human small cell lung cancer H146, based on angiogenesis inhibition. 1794 26

Cells were isolated from four human amniotic membranes, and their biological characteristics analyzed during ex vivo expansion. Morphologically homogenous populations of fibroblast-like cells were obtained from the second or third passage. Under the appropriate culture conditions, these human amniotic membrane-derived mesenchymal cells (HAM) were shown to differentiate into adipocytes, osteocytes, chondrocytes and neuronal cells, as visualized by Oil Red O, von Kossa, alcian blue, anti-Neu N, and anti-Gal C antibody staining, respectively. Immunophenotype analysis of HAM cells revealed the presence of antigens for SSEA-3, SSEA-4, collagen type-I, -II, -III, -IV, -XII, fibronectin, alpha-SMA, vimentin, desmin, cytokeratin18 (CK18), HCAM-1, fibroblast surface protein, and human leukocyte antigen (HLA) ABC. ICAM-1 protein was weakly detectable, and proteins of TRA-1-60, VCAM-1, von Willebrand factor, PECAM-1, and HLA DR were not detected. HAM cells reached senescence after 14.5+/-0.9 passages, over a period of 146.8+/-8.9 days, and underwent an average of 36.9 4.7 population doublings. RT-PCR analysis showed that all four HAM cell lines consistently expressed genes of Oct-4, Rex-1, SCF, NCAM, nestin, BMP-4, GATA-4, HNF-4alpha, vimentin, and CK18, regardless of the passage number. The genes of Brachyury, FGF-5, Pax-6, and BMP2 were never expressed. Strikingly, alpha-fetoprotein (alphaFP), HLA ABC, and HLA DR genes were expressed in an earlier passage but not expressed in later passages. Telomerase activity of two HAM lines was discernable upon the third passage. These observations strongly suggest that HAM might be immune-privileged and, thus, advantageous as therapeutic cells.
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PMID:Ex vivo characteristics of human amniotic membrane-derived stem cells. 1815 18

The transcription factor STAT1 has roles in development, homeostasis, cellular differentiation, and apoptosis and has been postulated to function as a tumor suppressor. STAT1 is activated by tyrosine or serine phosphorylation in response to specific cytokines or following a variety of stress-induced stimuli. STAT1 activity is carefully regulated to prevent sustained STAT1-mediated transcription, although the molecular mechanisms involved in the modulation of STAT1 stability are poorly understood. Here we show that activated STAT1 is degraded at the proteasome by a mechanism involving the F-box E3 ligase, SCF(betaTRCP). Active p42/p44 MAPK-ERK phosphorylates STAT1 on serine 727 and targets it for proteasomal degradation. SCF(betaTRCP) binds wild-type STAT1 but not the nonphosphorylatable mutant STAT1(S727A). Moreover, silencing betaTRCP expression or pharmacological inhibition of ERK activity stabilized STAT1 expression. These data suggest that constitutively active ERK may inappropriately degrade STAT1, with loss of its pro-apoptotic and tumor suppressor functions.
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PMID:ERK and the F-box protein betaTRCP target STAT1 for degradation. 2960 81

BCR-ABL is proposed to impair cell-cycle control by disabling p27, a tumor suppressor that inhibits cyclin-dependent kinases. We show that in cell lines p27 expression is inversely correlated with expression of SKP2, the F-box protein of SCF(SKP2) (SKP1/Cul1/F-box), the E3 ubiquitin ligase that promotes proteasomal degradation of p27. Inhibition of BCR-ABL kinase causes G(1) arrest, down-regulation of SKP2, and accumulation of p27. Ectopic expression of wild-type SKP2, but not a mutant unable to recognize p27, partially rescues cell-cycle progression. A similar regulation pattern is seen in cell lines transformed by FLT3-ITD, JAK2(V617F), and TEL-PDGFRbeta, suggesting that the SKP2/p27 conduit may be a universal target for leukemogenic tyrosine kinases. Mice that received transplants of BCR-ABL-infected SKP2(-/-) marrow developed a myeloproliferative syndrome but survival was significantly prolonged compared with recipients of BCR-ABL-expressing SKP2(+/+) marrow. SKP2(-/-) leukemic cells demonstrated higher levels of nuclear p27 than SKP2(+/+) counterparts, suggesting that the attenuation of leukemogenesis depends on increased p27 expression. Our data identify SKP2 as a crucial mediator of BCR-ABL-induced leukemogenesis and provide the first in vivo evidence that SKP2 promotes oncogenesis. Hence, stabilization of p27 by inhibiting its recognition by SCF(SKP2) may be therapeutically useful.
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PMID:Absence of SKP2 expression attenuates BCR-ABL-induced myeloproliferative disease. 1855 73


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