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:2.7.11.24 (mitogen-activated protein kinase)
95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A critical issue in understanding receptor tyrosine kinase signaling is the individual contribution of diverse signaling pathways in regulating cellular growth, survival, and migration. We generated a functionally and biochemically inert c-Kit receptor that lacked the binding sites for seven early signaling pathways. Restoring the Src family kinase (SFK) binding sites in the mutated c-Kit receptor restored cellular survival and migration but only partially rescued proliferation and was associated with the rescue of the Ras/mitogen-activated protein kinase, Rac/JNK kinase, and phosphatidylinositol 3-kinase (PI-3 kinase)/Akt pathways. In contrast, restoring the PI-3 kinase binding site in the mutated receptor did not affect cellular proliferation but resulted in a modest correction in cell survival and migration, despite a complete rescue in the activation of the PI-3 kinase/Akt pathway. Surprisingly, restoring the binding sites for Grb2, Grb7, or phospholipase C-gamma had no effect on cellular growth or survival, migration, or activation of any of the downstream signaling pathways. These results argue that SFKs play a unique role in the control of multiple cellular functions and in the activation of distinct biochemical pathways via c-Kit.
...
PMID:c-Kit-mediated overlapping and unique functional and biochemical outcomes via diverse signaling pathways. 1472 82

Loss-of-function mutations in the murine dominant white spotting/c-kit locus affect a diverse array of biological processes and cell lineages and cause a range of phenotypes, including severe anemia, defective pigmentation, sterility, mast cell deficits, a lack of interstitial cells of Cajal, spatial learning memory deficits, and defects in peripheral nerve regeneration. Here we show that tyrosine residues 567 and 569 in the juxtamembrane (Jx) domain of the murine Kit receptor tyrosine kinase are crucial for the function of Kit in melanogenesis and mast cell development, but are dispensable for the normal development of erythroid, interstitial cells of Cajal and germ cells. Furthermore, adult mice lacking both tyrosines exhibit splenomegaly, dysregulation of B-cell and megakaryocyte development, and enlarged stomachs. Analysis of signal transduction events induced by the mutant receptors after ligand stimulation indicates that Jx tyrosine mutations diminish receptor autophosphorylation and selectively attenuate activation of extracellular signal-regulated kinase/mitogen-activated protein kinases. Together, these observations demonstrate that the Jx domain of Kit plays a cell-type specific regulatory role in vivo and illustrate how engineered mutations in Kit can be used to understand the complex biological and molecular events that result from activating a receptor tyrosine kinase.
...
PMID:Targeted mutations of the juxtamembrane tyrosines in the Kit receptor tyrosine kinase selectively affect multiple cell lineages. 1506 26

The B-Raf(V599E)-mediated constitutive activation of ERK1/2 is involved in establishing the transformed phenotype of some uveal melanoma cells (Calipel, A., Lefevre, G., Pouponnot, C., Mouriaux, F., Eychene, A., and Mascarelli, F. (2003) J. Biol. Chem. 278, 42409-42418). We have shown that stem cell factor (SCF) is involved in the proliferation of normal uveal melanocytes and that c-Kit is expressed in 75% of primary uveal melanomas. This suggests that the acquisition of autonomous growth during melanoma progression may involve the SCF/c-Kit axis. We used six human uveal melanoma tumor-derived cell lines and normal uveal melanocytes to characterize the SCF/c-Kit system and to assess its specific role in transformation. We investigated the possible roles of activating mutations in c-KIT, the overexpression of this gene, and ligand-dependent c-Kit overactivation in uveal melanoma cell tumorigenesis. Four cell lines (92.1, SP6.5, Mel270, and TP31) expressed both SCF and c-Kit, and none harbored the c-KIT mutations in exons 9, 11, 13, and 17 that have been shown to induce SCF-independent c-Kit activation. Melanoma cell proliferation was strongly inhibited by small interfering RNA-mediated depletion of c-Kit in these cells, despite the presence of (V599E)B-Raf in SP6.5 and TP31 cells. We characterized the signaling pathways involved in SCF/c-Kit-mediated cell growth and survival in normal and tumoral melanocytes and found that constitutive ERK1/2 activation played a key role in both the SCF/c-Kit autocrine loop and the gain of function of (V599E)B-Raf for melanoma cell proliferation and transformation. We also provide the first evidence that Glivec/STI571, a c-Kit tyrosine kinase inhibitor, could be used to treat uveal melanomas.
...
PMID:Roles of stem cell factor/c-Kit and effects of Glivec/STI571 in human uveal melanoma cell tumorigenesis. 1514 34

Eosinophil-mediated diseases, such as allergic asthma, eosinophilic fasciitis, and certain hypersensitivity pulmonary disorders, are characterized by eosinophil infiltration and tissue injury. Mast cells and T cells often colocalize to these areas. Recent data suggest that mast cells can contribute to eosinophil-mediated inflammatory responses. Activation of mast cells can occur by antigen and immunoglobulin E (IgE) via the high-affinity receptor (FcepsilonRI) for IgE. The liberation of proteases, leukotrienes, lipid mediators, and histamine can contribute to tissue inflammation and allow recruitment of eosinophils to tissue. In addition, the synthesis and expression of a plethora of cytokines and chemokines (such as granulocyte-macrophage colony-stimulating factor [GM-CSF], interleukin-1 [IL-1], IL-3, IL-5, tumor necrosis factor-alpha [TNF-alpha], and the chemokines IL-8, regulated upon activation normal T cell expressed and secreted [RANTES], monocyte chemotactic protein-1 [MCP-1], and eotaxin) by mast cells can influence eosinophil biology. Stem cell factor (SCF)-c-kit, cytokine-cytokine receptor, and chemokine-chemokine receptor (CCR3) interactions leading to nuclear factor kappaB (NF-kappaB), mitogen-activated protein kinase (MAPK) expression, and other signaling pathways can modulate eosinophil function. Eosinophil hematopoiesis, activation, survival, and elaboration of mediators can all be regulated thus by mast cells in tissue. Moreover, because eosinophils can secrete SCF, eosinophils can regulate mast cell function in a paracrine manner. This two-way interaction between eosinophils and mast cells can pave the way for chronic inflammatory responses in a variety of human diseases. This review summarizes this pivotal interaction between human mast cells and eosinophils.
...
PMID:The role of human mast cell-derived cytokines in eosinophil biology. 1515 10

Most gastrointestinal stromal tumors (GISTs) have gain-of-function mutations of the c-kit gene. Previously, we found 2 types of gain-of-function mutation of the PDGFRA gene, Val561 to Asp and Asp842 to Val, in about half of GISTs without c-kit gene mutations. Although the inhibitory effect of imatinib on various types of activating mutant KIT has been well examined, that on the activating mutant PDGFRA has not been fully investigated. In the present study, we examined the effect of imatinib on autophosphorylation of mutant PDGFRA, phosphorylation of MAPK and of Akt and in vitro cell proliferation using murine Ba/F3 cells stably transfected with one of the 2 murine-type mutated PDGFRA cDNAs. Imatinib almost completely inhibited autophosphorylation of mutant PDGFRA, phosphorylation of MAPK and Akt as well as in vitro cell proliferation at the concentration of 0.01 microM in cells expressing mutant PDGFRA with Val561 to Asp. However, in cells expressing mutant PDGFRA with Asp842 to Val, imatinib almost completely inhibited autophosphorylation of mutant PDGFRA and phosphorylation of MAPK and Akt at 1.0 microM. The concentration contributing to complete inhibition of in vitro cell proliferation was 10 microM. Ba/F3 cells expressing mutant PDGFRA are a good model to investigate the mechanism of cell proliferation or growth inhibition by imatinib in mutant PDGFRA-driven cells.
...
PMID:Different inhibitory effect of imatinib on phosphorylation of mitogen-activated protein kinase and Akt and on proliferation in cells expressing different types of mutant platelet-derived growth factor receptor-alpha. 1522 57

Members of the homeobox family of transcription factors are major regulators of hematopoiesis. Overexpression of either HOXB4 or HOXA9 in primitive marrow cells enhances the expansion of hematopoietic stem cells (HSCs). However, little is known of how expression or function of these proteins is regulated during hematopoiesis under physiological conditions. In our previous studies we demonstrated that thrombopoietin (TPO) enhances levels of HOXB4 mRNA in primitive hematopoietic cells (K. Kirito, N. Fox, and K. Kaushansky, Blood 102:3172-3178, 2003). To extend our studies, we investigated the effects of TPO on HOXA9 in this same cell population. Although overall levels of the transcription factor were not affected, we found that TPO induced the nuclear import of HOXA9 both in UT-7/TPO cells and in primitive Sca-1(+)/c-kit(+)/Gr-1(-) hematopoietic cells in a mitogen-activated protein kinase-dependent fashion. TPO also controlled MEIS1 expression at mRNA levels, at least in part due to phosphatidylinositol 3-kinase activation. Collectively, TPO modulates the function of HOXA9 by leading to its nuclear translocation, likely mediated by effects on its partner protein MEIS1, and potentially due to two newly identified nuclear localization signals. Our data suggest that TPO controls HSC development through the regulation of multiple members of the Hox family of transcription factors through multiple mechanisms.
...
PMID:Thrombopoietin induces HOXA9 nuclear transport in immature hematopoietic cells: potential mechanism by which the hormone favorably affects hematopoietic stem cells. 1525 42

The Kasumi-1 cell line is an intensively investigated model system of Acute Myeloid Leukemia with t(8;21) translocation, that represents 1 of the 2 main subtypes of Core Binding Factor Leukemia (CBFL). Since establishment in 1991 the Kasumi-1 cell line has provided the tool to study the peculiar molecular, morphologic, immunophenotypic findings of AML with t(8;21) and the functional consequences of the AML1-ETO fusion oncogene on myeloid differentiation. Leukemogenesis involves multiple genetic changes and, as suggested by murine experiments and other findings in humans, AML1-ETO expression may not be sufficient for full blown leukemia. In agreement with the "two hits" model of leukemogenesis, based on the cooperation between 1 class of mutations that impair hematopoietic differentiation and a second class of mutations that confer a proliferative and/or survival advantage to hematopoietic progenitors an activating mutation in the tyrosine kinase domain of the c-kit gene was identified in the AML1/ETO expressing Kasumi-1 cell line. The dosage of the Asn822Lys mutated allele was shown to be about 5-fold compared to the normal allele and c-kit amplification was found to map to minute 4cen-q11 marker chromosomes, likely derived from the extra chromosome 4 recorded in the newly established cell line. The combination of t(8;21) and trisomy 4 leading to enhanced dosage of a mutated kit allele is a feature of a few CBFL patients reproduced by the Kasumi-1 cell model. The Kasumi-1 cell line, paralleling the commitment stage of CBF leukemia also provides a valuable resource to investigate the effect of tyrosine kinase kit mutant on the main KIT-regulated signal transduction pathways, i.e. MAPK, PI3K/AKT and STAT3 and the diverse inhibitory effect exerted by STI 571 on these KIT mutant activated pathways. PI3K-dependent activation of AKT and STAT activation was observed in Kasumi-1 cells. Contrary to the expectations for an amplified tyrosine kinase kit mutant, we found that STI 571 inhibited KIT Asn822Lys tyrosine phosphorylation and downstream JNK and STAT3 effectors in Kasumi-1 cells, but had no effect on constitutive activation of AKT, suggesting that signaling by tyrosine kinases other than KIT may be responsible for its activation in Kasumi-1 cells. Independent findings on the same model system provide complementary insights into designing strategies for treatment of CBF leukemia associated with mutations in the KIT catalytic domain.
...
PMID:The Kasumi-1 cell line: a t(8;21)-kit mutant model for acute myeloid leukemia. 1562 9

We investigated the effect of SCF, a c-kit ligand, on the radiosensitivity of HL60 cells. X-ray-induced apoptosis in HL60 cells was significantly lower in the presence of SCF than in the absence of SCF. This attenuation of X-ray-induced apoptosis by SCF was abolished by PD98059 (an ERK inhibitor), but not by wortmannin (a PI3-K inhibitor) or GF109203X (a PKC inhibitor). The expression of phospho-ERK1/2 (active form) and the ERK1/2-regulated expression of survivin were found to increase in cells treated with X irradiation and SCF. However, X irradiation alone induced down-regulation of the expression of phospho-ERK1/2. Our findings suggest that activation of c-kit by SCF confers radioresistance through up-regulation of ERK-dependent survivin expression in HL60 cells.
...
PMID:Activation of c-kit by stem cell factor induces radioresistance to apoptosis through ERK-dependent expression of survivin in HL60 cells. 1563 66

The development of in vitro models for testicular toxicity may provide important tools for investigating specific mechanisms of toxicity in the testis. Although various systems have been reported, their application in toxicological studies has been limited by the poor ability to replicate the complex biochemical, molecular, and functional interactions observed in the testis. In the present study, we evaluated a significantly improved Sertoli cell/gonocyte co-culture (SGC) system that employs a 3-dimensional extracellular matrix Matrigel (ECM) applied as an overlay instead of a substratum. We explored the dose- and time-dependent effects of the addition of such an ECM overlay on cytoskeletal and morphological changes in the SGC system, and the resulting effects on cellular integrity. Furthermore, we correlated the latter effects with the ECM-dependent modulation of stress and survival signaling pathways and, most critically, the expression levels of the spermatogonia-specific protein, c-Kit. Finally, we applied this co-culture system to investigate the dose- and time-dependent effects on the morphology and induction of apoptosis of cadmium. We observed that the dose-dependent addition of an ECM overlay led to an enhanced attachment of Sertoli cells and facilitated the establishment of SGC communication and cytoskeletal structure, with a dramatic improvement in cell viability. The latter was consistent with the observed dose- and time-dependent modulation of both stress signaling pathways (SAPK/JNK) and survival signaling pathways (ERK and AKT) in the presence of the ECM overlay. Furthermore, the dose-dependent stabilization of c-Kit protein expression confirmed the functional integrity of this co-culture system. We conclude that this modified SGC system will provide investigators with a simple, efficient, and highly reproducible alternative in the screen for testicular cell-specific cytotoxicity and the assessment of molecular mechanisms associated with both normal development and reproductive toxicity induced by environmental toxicants.
...
PMID:Essential role of extracellular matrix (ECM) overlay in establishing the functional integrity of primary neonatal rat Sertoli cell/gonocyte co-cultures: an improved in vitro model for assessment of male reproductive toxicity. 1565 72

Intercellular adhesion molecule-1 (ICAM-1) has been shown to play crucial roles in mast cell interaction with other inflammatory cells and recruitment into the inflamed tissue. In the present study, human mast cell line-1 (HMC-1) was stimulated with different cytokines including stem cell factor (SCF), tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-13, IL-18, and IL-25. Cell-surface expression of ICAM-1 was assessed by flow cytometry. To elucidate the intracellular signal transduction regulating the ICAM-1 expression, phosphorylated extracellular signal-regulated kinase (ERK), phosphorylated p38 mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-kappaB translocation were assessed by enzyme-linked immunosorbent assay. Results showed that SCF, TNF-alpha, and IL-13 but not IL-18 and IL-25 could up-regulate the surface expression of ICAM-1 on HMC-1 cells. A synergistic effect of SCF and TNF-alpha on ICAM-1 expression was demonstrated. This synergistic effect was shown to be dose-dependently enhanced by SCF but not TNF-alpha. Results indicated that SCF activated ERK, and TNF-alpha activated the p38 MAPK and NF-kappaB pathway. Selective inhibitor of ERK, PD098059, and c-kit inhibitors, STI571 and PP1, suppressed the combined SCF and TNF-alpha-induced ICAM-1 expression. BAY117082 but not SB203580, which are the inhibitors of NF-kappaB and p38 MAPK, respectively, suppressed the TNF-alpha-induced ICAM-1 expression. Therefore, SCF and TNF-alpha acted through ERK and the NF-kappaB pathway to regulate the ICAM-1 expression and elicited the synergistic effect. In conclusion, our results provide insight for cross-talk between different signaling pathways that can help in understanding the fine control of adhesion molecule expression under the concerted effects of cytokines.
...
PMID:Synergistic effect of SCF and TNF-alpha on the up-regulation of cell-surface expression of ICAM-1 on human leukemic mast cell line (HMC)-1 cells. 1580 27


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

---