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)

The stem cell factor (SCF) is a polypeptide ligand that is essential for the development of germ cells, hematopoietic progenitor cells, and melanocyte precursors. It binds to a tyrosine kinase membrane receptor that is encoded by the c-kit proto-oncogene. We have constructed an expression vector that directs the synthesis of the entire extracellular ligand-binding domain of the Kit/SCF receptor. When expressed and amplified in Chinese hamster ovary cells, a secreted 90-kDa glycoprotein could be harvested from the growth medium of the cells in a soluble form. This extracellular portion of the Kit/SCF receptor, denoted Kit-X, was recognized by antibodies specific to the SCF receptor; and when injected into animals, it raised antibodies that were reactive with the complete membrane form of the receptor. Direct binding and covalent cross-linking of radiolabeled SCF showed that Kit-X fully retained high affinity ligand binding and also underwent efficient dimerization in the presence of the ligand. The capacity of Kit-X to act as an antagonist of SCF was assayed on cultured cells that overexpress the receptor. Simultaneous addition of SCF and Kit-X to these cells resulted in a stoichiometric inhibition of SCF binding and a consequent decrease in autophosphorylation of the SCF receptor on tyrosine residues. The inhibition extended to later SCF-mediated responses, including the association of the receptor with phosphatidylinositol 3'-kinase and coupling to the Raf1 protein kinase. These results indicate that the recombinant ectodomain of the Kit-SCF receptor can be used as a specific antagonist of SCF actions and may enable detailed molecular analysis of ligand-receptor interactions.
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PMID:A recombinant ectodomain of the receptor for the stem cell factor (SCF) retains ligand-induced receptor dimerization and antagonizes SCF-stimulated cellular responses. 137 32

The proto-oncogene c-kit encodes a transmembrane kinase which is related to the receptors for colony-stimulating factor type 1 and platelet-derived growth factor, as well as to the immunoglobulin superfamily. Antibodies specific for the kinase domain of the P80 gag-kit protein of the Hardy-Zuckerman 4 feline sarcoma virus were prepared. These kit-specific antibodies were used to identify and characterize the c-kit protein in cat brain tissue. The c-kit protein product displays an autophosphorylating activity in immune complex kinase assays, and, in turn, this activity was used to identify the c-kit protein in different tissues. In cat brain, a single 145-kilodalton (kDa) glycoprotein was detected. Its N-linked carbohydrates were found to be sensitive to digestion with the endoglycosidases (neuraminidase, endoglycosidase F, and endoglycosidase H), indicating hybrid and/or complex and high-mannose structures. A partial purification of the c-kit protein was achieved by wheat germ agglutinin affinity chromatography, and the autophosphorylating activity of the partially purified c-kit protein was characterized and found to be specific for tyrosine. The kit antibodies cross-react with the murine c-kit protein product, and variant c-kit proteins in different mouse tissues were identified, with sizes of about 145 kDa (brain), 160 kDa (spleen), and 150 kDa (testis).
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PMID:c-kit protein, a transmembrane kinase: identification in tissues and characterization. 246 68

A purified opioid-binding protein has been characterized by cDNA cloning. The cDNA sequence predicts an extracellularly located glycoprotein of 345 amino acids. This protein does not possess a membrane-spanning domain but contains a C-terminal hydrophobic sequence characteristic of membrane attachment by a phosphatidylinositol linkage. It displays homology to the immunoglobulin protein superfamily, featuring three domains that resemble disulfide-bonded constant regions. More specifically, the protein is most homologous to a subfamily of proteins which includes the neural cell adhesion molecule (NCAM) and myelin-associated glycoprotein (MAG) and one subgroup of the tyrosine kinase growth factor receptors comprising the platelet-derived growth factor receptor (PDGF R), the colony-stimulating factor 1 receptor (CSF-1 R) and the c-kit protooncogene. These sequence homologies suggest that the protein could be involved in either cell recognition and adhesion, peptidergic ligand binding or both.
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PMID:Molecular characterization of a new immunoglobulin superfamily protein with potential roles in opioid binding and cell contact. 272 89

The stem cell factor is a glycoprotein hormone which regulates the proliferation and differentiation of primitive hematopoietic cells through its interaction with a tyrosine kinase transmembrane receptor which is encoded by the c-kit proto-oncogene. To examine whether a murine c-kit receptor can be functional in murine interleukin-3 (mIL-3)-dependent hematopoietic cell line, we introduced the murine c-kit cDNA into mIL-3-dependent pro-B cell line Ba/F3. One of the resulting clones, Ba/F3 clone BF-K96, expressed the 140 kDa protein recognized by anti-c-kit monoclonal antibody and the expressed c-kit receptor protein on the cell surface bound to a radiolabeled soluble form of murine stem cell factor (mSCF) with high affinity. BF-K96 clone expressing the c-kit receptor could proliferate in response to mSCF in the absence of mIL-3. The cell clone could also grow in co-culture with mouse 3T3 cells which are endogeneously expressing a membrane-associated type of mSCF on their cell surfaces. These findings demonstrate that the c-kit receptor expressed on mIL-3-dependent hematopoietic cell line Ba/F3 transduce the mSCF-dependent growth signal, indicating that established cell clone will provide a unique cellular system for the study of SCF/c-kit signal transduction mechanism.
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PMID:The c-kit receptor transduces the stem cell factor-triggered growth signal in murine interleukin-3-dependent cell line. 753 63

A monoclonal hamster antibody (K-1) specific for a 161-kD mast cell surface glycoprotein was derived. p161 is expressed on normal and cultured mast cells and on some macrophages, but not on basophils or other hematopoietic cells. A population of Fc epsilon Rneg cells expressing p161 was found in short term cultures of bone marrow cells grown in interleukin (IL)-3. These cells were purified and propagated for extended periods in IL-3. They express c-kit and Fc gamma RII/III, contain alcian blue-positive granules and histamine, and secrete IL-3 in response to ionomycin treatment. Their morphology is consistent with that of mast cells. We propose that they represent Fc epsilon RIneg mast cells that can be detected and purified because of their p161 expression.
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PMID:Identification of Fc epsilon RIneg mast cells in mouse bone marrow cell cultures. Use of a monoclonal anti-p161 antibody. 762 14

Interleukin-3 (IL-3) regulates growth and differentiation of multipotential as well as lineage-committed progenitor cells. The human IL-3 receptor (IL-3R) consists of the alpha and common beta (beta c) subunits. The alpha subunit (IL-3R alpha) is specific for IL-3 and binds IL-3 with low affinity. In contrast, the beta c subunit does not bind any cytokine by itself, but forms a high-affinity receptor with IL-3R alpha. As the same beta c subunit also forms high-affinity receptors for IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) with the respective cytokine-specific alpha subunit, the expression of the alpha subunits is responsible for specificity of cytokines. To examine the expression of IL-3R alpha, we have developed a monoclonal antibody (MoAb), N3A. N3A specifically bound to cells expressing IL-3R alpha and immunoprecipitated a 75 Kd glycoprotein, which became 43 Kd on N-glycosidase digestion. N3A and an anti-beta c antibody, CRS1, were used in double color fluorescence-activated cell sorter (FACS) staining with several lineage markers to see the IL-3R expression pattern in peripheral blood (PB), cord blood (CB), and bone marrow (BM) cells. Both IL-3R subunits were expressed on myeloid cell lineages (CD13+, CD14+, CD15Lo, or CD33+). To further study the IL-3R expression on hematopoietic progenitor cells, the CD34+ populations were isolated from both BM and CB cells. Those populations showed positive staining profiles with the N3A MoAb and were weakly stained with the CRS1 MoAb. Furthermore, anti c-kit antibody staining of the CD34+ fraction from CB, but not from BM, showed two intensities and the IL-3R alpha expression seemed to be higher in a fraction of low c-kit expression. Because IL-1, IL-6, G-CSF, stem cell factor (SCF), interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha are known to enhance IL-3-dependent colony formation, we have examined whether this enhancement could be correlated with upregulation of the IL-3R expression. Incubation of CD34+ cells with TNF-alpha for 2 days significantly increased the level of beta c and G-CSF increased the number of cells with high level expression of alpha, while other factors did not affect the IL-3R expression. Thus, different cytokines appear to have different mechanisms for enhancement of IL-3-dependent proliferation.
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PMID:Expression and factor-dependent modulation of the interleukin-3 receptor subunits on human hematopoietic cells. 768 90

Erythropoietin (EPO) is the primary humoral regulator of erythropoiesis and no other factor has previously been reported to support proliferation and terminal maturation of erythroid cells from hemopoietic stem cells. Here we show that stimulation of glycoprotein (gp130) by a combination of recombinant human soluble interleukin 6 receptor (sIL-6R) and IL-6 but not sIL-6R or IL-6 alone can support proliferation, differentiation, and terminal maturation of erythroid cells in the absence of EPO from purified human CD34+ cells in suspension culture containing stem cell factor (SCF). A number of erythroid bursts and mixed erythroid colonies also developed in methylcellulose culture under the same combination. The addition of anti-gp130 monoclonal antibodies but not anti-EPO antibody to the same culture completely abrogated the generation of erythroid cells. These results clearly demonstrate that mature erythroid cells can be emerged from hemopoietic progenitors without EPO in vitro. Together with the previous reports that human sera contain detectable levels of sIL-6R, IL-6, and SCF, current data suggest that gp130 signaling in association with c-kit activation may play a role in human erythropoiesis in vivo.
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PMID:Erythropoietin-independent erythrocyte production: signals through gp130 and c-kit dramatically promote erythropoiesis from human CD34+ cells. 864 88

The biological effects of c-kit ligand (stem-cell factor: SCF) on an immortalized human megakaryocytic cell line (CMK) was evaluated using methods including the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, surface marker analysis, DNA cell-cycle analysis and immunoblotting. SCF stimulated the growth of CMK cells. Incubation with SCF resulted in increased expression of IIb/IIIa platelet-related glycoprotein (gpIIb, IIIa), indicating enhanced differentiation of CMK cells. Treatment of CMK cells with SCF resulted in a decrease in the subpopulation in the G1 phase, with a reciprocal increase in those in the S phase and the G2 + M phase. Moreover, SCF significantly increased cellular expression of cyclin A, a regulatory subunit of cyclin-dependent protein kinase (CDK), and the ratio of phosphorylated/dephosphorylated retinoblastoma gene product (RB protein). These results suggest that SCF stimulates the growth and differentiation of megakaryocytic cells possibly through mechanisms related to the activation of cell-cycle-dependent serine/threonine kinase and inactivation of the nuclear tumor-suppressor gene product.
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PMID:Stem-cell factor regulates the expression of cyclin A and retinoblastoma gene product in the growth and differentiation pathway of human megakaryocytic cells. 869 43

Three-color flow cytometry was used to analyze the coexpression of surface antigens on megakaryocytes (MKs) developing in liquid cultures of enriched CD34+ cells purified from cord blood. Cells were cultured in serum-replete medium supplemented with interleukin 3 (IL-3), stem cell factor and IL-6. During two weeks of culture, total cells increased 76 +/- 36-fold. CD34+ cells maximally expanded between days 2 and 4, and then gradually decreased to their original input numbers by day 14. As CD34+ cells declined, MKs, defined as glycoprotein (GP) IIbIIIa+ cells, steadily increased in culture 20.9 +/- 18.3-fold. Megakaryopoiesis was further defined by monitoring the expression of GPs IIb, IIIa, Ib, IbIX, and IIIb and c-kit antigen. Increased expression of GPs IIbIIIa and IIb occurred earliest in culture, followed by IIIa and Ib, and then IbIX. Expression of IIIb, also found on monocytes, did not parallel that of the other antigens except when coexpressed on IIbIIIa+ cells. c-kit expression paralleled that of CD34 until the second week of culture when expression was high on nonMKs. Each of these antigens was coexpressed on CD34+ cells and identified a subset of late MK progenitors that increased steadily in culture. Triplelabeled cells expressing CD34, IIbIIIa and a third MK-related antigen were seen at all times. Polyploid MKs of up to 32N were observed during the second week of culture. Multiparametric flow cytometry proved to be a rapid, sensitive and specific method for quantitating the changes in antigen expression of differentiating MKs.
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PMID:Flow cytometric analysis of megakaryocyte-associated antigens on CD34 cells and their progeny in liquid culture. 872 98

Interleukin 11 (IL-11) is a newly identified hematopoietic growth factor that exerts its primary effect on megakaryocyte maturation and platelet production. It has a unique receptor, signaling by which is mediated by the glycoprotein (GP) 130 pathway. IL-11 is synergistic with stem-cell factor (c-kit ligand) in vitro, enhancing proliferation of primitive hematopoietic stem cells, and has been shown to be critical to the process of polyploidization and maturation. In preclinical models, IL-11 was shown to enhance platelet recovery following intensive chemotherapy, and in murine bone-marrow transplant models it accelerates the recovery of all hematopoietic lineages. Nonhuman primate studies have demonstrated a dose-related thrombopoietic effect; however, no myeloid effect has been observed. In clinical phase I trials, subcutaneous IL-11 was well tolerated and induced a dose-related thrombopoietic effect in women with breast cancer. IL-11 at doses of > 25 micrograms/kg per day appeared to reduce the severity of chemotherapy-induced thrombocytopenia. In a randomized phase II trial, IL-11 at 50 micrograms/kg reduced the requirement for platelet transfusions as compared with that in placebotreated controls. IL-11 is an interesting factor; however, further studies are needed to confirm its activity and are in progress.
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PMID:Thrombopoietic activity of recombinant human interleukin 11 in cancer patients receiving chemotherapy. 876 26


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