Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Steel factor (SF) is a growth and survival factor for hematopoietic cells. The receptor for SF, c-Kit, contains intrinsic tyrosine kinase activity, and binding of SF induces rapid tyrosine phosphorylation of several cellular proteins, including c-Kit itself. Activation of c-Kit is shown here to induce tyrosine phosphorylation of CRKL, and CRKL coprecipitated with c-Kit through an interaction that required the CRKL SH3 domains and not the SH2 domain. CRKL associated with c-Kit indirectly as part of a larger complex of proteins. Two proteins in this complex were identified as the p85 regulatory subunit of phosphatidylinositol 3-kinase (p85(PI3K)) and the proto-oncoprotein p120(CBL). Because p85(PI3K) is known to bind to the activated c-Kit receptor, the possibility that CRKL interacted with c-Kit indirectly through p85(PI3K) was investigated. Far Western blotting with a CRKL-SH3 glutathione S-transferase fusion protein showed that CRKL binds directly to p85(PI3K )in vitro. However, although a small amount of CRKL was preassociated with p85(PI3K), the interaction was increased after SF stimulation, suggesting that the interactions of these three proteins are complex. We conclude that SF induces the formation of a signaling complex potentially containing CRKL and p120(CBL), both of which bind to c-Kit through p85(PI3K). These data suggest that one function of CRKL in normal cells might be to recruit signaling molecules such as CBL into a complex with PI3K. Such complexes could be important in propagating signals involving PI3K such as gene expression and adhesion.
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PMID:Steel factor induces tyrosine phosphorylation of CRKL and binding of CRKL to a complex containing c-kit, phosphatidylinositol 3-kinase, and p120(CBL). 909 74

The presence and role of the c-kit protein was investigated in the mature sperm of the mouse. The c-kit monoclonal antibody (mAb) ACK2 reacted specifically with the acrosomal region and the principal piece of fixed noncapacitated sperm but did not react with the acrosome region in acrosome-reacted sperm. ACK2 significantly inhibited the acrosome reaction; this inhibition was relieved by the calcium ionophore A23187. The kit ligand stem cell factor (SCF) significantly increased the percentage of sperm undergoing acrosome reaction. This increase was partially inhibited by the calcium channel inhibitor (verapamil), the PI3k inhibitor (wortmannin), and the PLC inhibitor (U-73122). ACK2 predominantly recognized c-kit proteins of 33, 48, and 150 kDa by Western blotting of mouse sperm extracts. The 48- and 150-kDa protein bands were released into the media and tyrosine autophosphorylated at low basal levels during acrosome reaction. On stimulation with SCF, the level of c-kit phosphorylation increased significantly. These findings suggest that c-kit is present in mature sperm, and its binding to SCF may result in the activation of PLC gamma 1 and PI3K, leading to receptor autophosphorylation, and ultimately may play a role in capacitation and/or the acrosome reaction.
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PMID:The c-kit receptor and its possible signaling transduction pathway in mouse spermatozoa. 949 84

Kit, a tyrosine kinase growth factor receptor, and its ligand, stem cell factor (SCF), are commonly coexpressed in breast cancer. We have previously shown that MCF7 cells (that naturally express SCF) transfected with a c-kit expression vector exhibit enhanced growth in serum-free medium supplemented with IGF-1. Consequently, we wished to examine the interaction of Kit/SCF with additional growth factors important in the biology of breast cancer. MCF7 transfectants expressing Kit, cultured in serum-free medium supplemented with EGF, displayed more than twice the growth of controls at identical EGF concentrations. Similar responses were seen in the presence of heregulin alpha. The specificity of the Kit-mediated response was illustrated by a reduction in heregulin-stimulated growth in the presence of a monoclonal antibody directed against the Kit receptor. In addition, EGF- and heregulin-stimulated growth of the ZR75-1 cell line that naturally coexpresses Kit and SCF was also inhibited by the Kit blocking antibody. Preliminary investigations into the signal transduction pathways activated by these growth factors revealed that SCF activated both the Ras-MAP kinase and phosphatidyl-inositol-3-kinase (PI3 kinase) pathway. Both EGF and heregulin activated MAPK but to a lesser degree than SCF, and combination of SCF with these growth factors resulted in enhanced MAPK activation. Assessment of PI3K pathway activation using antiphospho-Akt antibodies revealed that EGF was a poor activator of Akt; activation of this pathway was markedly enhanced by the addition of SCF. Heregulin activated Akt and addition of SCF provided no further activation. Taken together these results suggest that coexpression of SCF and Kit may enhance responsiveness to erbB ligands by enhancing activation of the MAPK and PI3K pathways.
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PMID:Coexpression of c-kit and stem cell factor in breast cancer results in enhanced sensitivity to members of the EGF family of growth factors. 1063 12

HMG-CoA reductase inhibitors (statins) have been developed as lipid-lowering drugs and are well established to reduce morbidity and mortality from coronary artery disease. Here we demonstrate that statins potently augment endothelial progenitor cell differentiation in mononuclear cells and CD34-positive hematopoietic stem cells isolated from peripheral blood. Moreover, treatment of mice with statins increased c-kit(+)/Sca-1(+)--positive hematopoietic stem cells in the bone marrow and further elevated the number of differentiated endothelial progenitor cells (EPCs). Statins induce EPC differentiation via the PI 3-kinase/Akt (PI3K/Akt) pathway as demonstrated by the inhibitory effect of pharmacological PI3K blockers or overexpression of a dominant negative Akt construct. Similarly, the potent angiogenic growth factor VEGF requires Akt to augment EPC numbers, suggesting an essential role for Akt in regulating hematopoietic progenitor cell differentiation. Given that statins are at least as potent as VEGF in increasing EPC differentiation, augmentation of circulating EPC might importantly contribute to the well-established beneficial effects of statins in patients with coronary artery disease.
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PMID:HMG-CoA reductase inhibitors (statins) increase endothelial progenitor cells via the PI 3-kinase/Akt pathway. 1148 28

Stem cell factor (SCF) is essential for the development of primordial follicles. One of its functions is to prevent oocytes from apoptosis. However, the underlying mechanism remains largely unknown. By using cultured ovaries that are rich in primordial follicles, the anti-apoptotic action of SCF and the potential signal transduction pathways were investigated. The apoptosis was evaluated by means of in situ 3'-end labeling. The expressions of proteins were analyzed with immunohistochemistry and Western blot. The data showed that SCF significantly prevented oocytes from apoptosis in the cultured organs. Addition of a specific pharmacological inhibitor of PI3K abolished the anti-apoptotic action of SCF while that of a MEK inhibitor did not. The phosphorylation of two mitogen activated protein kinases (MAPKs) (p42 and p44) and AKT, the respective substrates of MEK and PI3K, were enhanced by SCF treatment. Not surprisingly, the MAPK activation occurred only in theca cells. The expressions of apoptosis-related gene products, the Bcl-2 family proteins, in response to SCF treatment were also investigated. While SCF up-regulated the expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, it did the opposite to the pro-apoptotic factor Bax. The PI3K inhibitor reversed the regulation of SCF on Bcl-xL and Bax but not on Bcl-2. Therefore, it seemed that SCF initiated an anti-apoptotic signal starting from its membrane receptor c-kit to Bcl-2 family members through PI3K/AKT and other signaling cascades in the oocytes of primordial follicles.
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PMID:Anti-apoptotic action of stem cell factor on oocytes in primordial follicles and its signal transduction. 1551 61

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.
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PMID:The Kasumi-1 cell line: a t(8;21)-kit mutant model for acute myeloid leukemia. 1562 9

Hepatocyte growth factor (HGF), a pleiotropic cytokine of mesenchymal origin promoting migration, proliferation, and survival in a wide spectrum of cells, can also modulate different biological responses in stem cells, but the mechanisms involved are not completely understood so far. In this context, we show that short-term exposure of mesenchymal stem cells (MSCs) to HGF can induce the activation of its cognate Met receptor and the downstream effectors ERK1/2, p38MAPK, and PI3K/Akt, while long-term exposure to HGF resulted in cytoskeletal rearrangement, cell migration, and marked inhibition of proliferation through the arrest in the G1-S checkpoint. When added to MSCs, the K252A tyrosine kinase inhibitor prevented HGF-induced responses. HGF's effect on MSC proliferation was reversed by p38 inhibitor SB203580, while the effects on cell migration were abrogated by PI3K inhibitor Wortmannin, suggesting that HGF acts through different pathways to determine its complex effects on MSCs. Prolonged treatment with HGF induced the expression of cardiac-specific markers (GATA-4, MEF2C, TEF1, desmin, alpha-MHC, beta-MHC, and nestin) with the concomitant loss of the stem cell markers nucleostemin, c-kit, and CD105.
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PMID:Hepatocyte growth factor effects on mesenchymal stem cells: proliferation, migration, and differentiation. 1610 5

Stem cell factor (SCF) is a highly expressed cytokine in the central nervous system. In the present study, we demonstrate a neuroprotective role for SCF and its tyrosine kinase receptor, c-kit, against camptothecin-induced apoptosis and glutamate excitotoxicity in rat cortical neurons. This protection was blocked by pharmacological or molecular inhibition of either the MEK/ERK or PI3K/Akt signaling pathways. The importance of these pathways was further confirmed by the activation of both ERK, in a MEK-dependent manner, and Akt, via PI3K. Activation of Akt increased the binding of the p50 and p65 subunits of NFkappaB, which was also important for neuroprotection. Akt inhibition prevented NFkappaB binding, suggesting a role for Akt in SCF-induced NFkappaB. Pharmacological inhibition of NFkappaB or dominant negative IkappaB also prevented neuroprotection by SCF. SCF up-regulated the anti-apoptotic genes, bcl-2 and bcl-xL in an NFkappaB-dependent manner. Together, these findings demonstrate a neuroprotective role for SCF in cortical neurons, an effect that was mediated by Akt and ERK, as well as NFkappaB-mediated gene transcription. SCF represents a novel therapeutic target in the treatment of neurodegenerative disease.
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PMID:Neuroprotection by stem cell factor in rat cortical neurons involves AKT and NFkappaB. 1618 9

Tyrosine kinases have been strongly implicated as therapeutic targets that influence the angiogenic process in growing tumors. In this study, we revealed that TKI-31 is a potent broad spectrum tyrosine kinase inhibitor, which inhibits vascular endothelial growth factor receptor 2 (VEGFR2), platelet-derived growth factor receptor beta (PDGFRbeta) and also inhibits kinases of other class, such as c-Kit and c-Src on molecular base, but showed no activity against vascular endothelial growth factor receptor 1 (VEGFR1) and epidermal growth factor receptor (EGFR). TKI-31 inhibits VEGF-induced phosphorylation of VEGFR2 in endothelial cells as well as PDGF(BB)-induced phosphorylation in fibroblast cells, and leading to the inhibition of down-stream signaling triggered by these receptors such as PI3K/Akt/mTOR, MAPK42/44(ERK) and paxillin. TKI-31 also inhibited VEGF-induced endothelial cells proliferation, migration and their differentiation into capillary-like tube formation. Its anti-angiogenic property was further confirmed by the inhibition of neovascularization on CAM, in vivo. These results collectively highlight the therapeutic potential of this compound for the treatment of solid tumors and other diseases where angiogenesis plays an important role.
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PMID:TKI-31 inhibits angiogenesis by combined suppression signaling pathway of VEGFR2 and PDGFRbeta. 1657 1

In concert with its ligand, the stem cell factor (SCF), the receptor tyrosine kinase c-Kit acts as a key signaling molecule for a number of cell types, including hematopoietic stem cells, mast cells, melanocytes and germ cells. Gain-of-function mutations in c-Kit have been described in a number of human cancers, including testicular germinomas, acute myeloid leukemia and gastrointestinal stromal tumors. Yet their contribution to neoplastic growth is incompletely understood. Now Kosmider et al report the acquisition of Kit mutations in 86% of late-stage eryhtroleukemias in Spi-1/PU.1 transgenic mice. Without Kit mutations, these mice suffer from a benign disease whose hallmark is erythropoietin-dependent expansion of undifferentiated red blood cell precursors. Newly acquired Kit mutations affect codon 814 or 818, and ectopic expression of these mutants in nonmalignant pro-erythroblasts confers erythropoietin independence and tumorigenicity. Using tyrosine kinase inhibitors PP1, PP2, and imatinib mesylate (a.k.a. Gleevac), the authors demonstrate that Kit mutations are important for the autonomous expansion of malignant cells via the MEK/Erk1/2 and PI3K/Akt pathways. These findings validate the notion that one differentiation-blocking (e.g., PU.1 activation) and one proliferative (e.g., c-Kit mutations) event are required for the development of frank leukemia.
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PMID:Kit-activating mutations in AML: lessons from PU.1-induced murine erythroleukemia. 1676 Jun 43


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