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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To characterize the production of stem cell factor (SCF, the ligand for the c-kit receptor protein) and its regulation by inflammatory cytokines and glucocorticoids, primary marrow stromal fibroblasts were isolated from normal individuals and two patients with Diamond-Blackfan anemia. Unstimulated normal marrow stromal fibroblasts constitutively expressed a low level of SCF mRNA (9 +/- 2 copies/cell [mean +/- SEM]), continually secreted soluble SCF into the supernatant of 1- to 5-day-old cultures (0.16 +/- 0.02 to 0.73 +/- 0.04 ng/mL per 10(6) cells, respectively), and expressed membrane-bound SCF. Stimulation with interleukin-1 beta (IL-1 beta) only modestly increased SCF mRNA levels, soluble SCF production at 24 hours, and membrane-bound SCF. In comparison, hydrocortisone or tumor necrosis factor alpha (TNF-alpha) exposure increased SCF mRNA levels 3.5- to four-fold above controls, but with different kinetics. The peak TNF-alpha effect was at 6 hours, with return to near control levels at 24 hours, whereas hydrocortisone induced maximal mRNA increases at 12 to 18 hours, and the levels remained high at 24 hours. Similarly, a sustained increase in soluble SCF production was detected during 1 to 5 days of hydrocortisone exposure (0.27 +/- 0.03 to 1.10 +/- 0.08 ng/mL per 10(6) cells), while TNF-alpha stimulation modestly increased the production of soluble SCF in 24-hour cultures only. Unstimulated normal marrow fibroblasts expressed predominantly the long species of alternatively spliced SCF mRNA, and the relative amounts of long and short mRNAs did not change after stimulation with IL-1 beta, hydrocortisone, or TNF-alpha. SCF production by marrow stromal fibroblasts from a symptomatic patient with Diamond-Blackfan anemia was equivalent to simultaneously studied normal marrow fibroblasts. In contrast, marrow fibroblasts from a Diamond-Blackfan anemia patient in untreated hematologic remission constitutively expressed high levels of SCF mRNA (21 +/- 4 copies/cell) and soluble protein (0.40 ng/mL per 10(6) cells at 24 hours). Together, these observations suggest that SCF is constitutively produced by fibroblasts in the human marrow microenvironment and that hydrocortisone induces a modest but sustained increase in SCF gene expression and protein production, compared to only a transient increase induced by TNF-alpha. In addition, these findings support the hypothesis that endogenous or corticosteroid-induced increases in the production of SCF could play a physiologic role in the clinical improvement of congenital anemia.
Exp Hematol 1995 Sep
PMID:Stem cell factor production by human marrow stromal fibroblasts. 754 39

Receptor tyrosine kinases are known to be important in growth and differentiation. We have recently found that c-kit, the tyrosine kinase receptor for steel factor, also regulates cell-matrix adhesion. Because Steel factor helps regulate cell migration and localization, this may be an important biologic function. Integrin adhesiveness is regulated within minutes by c-kit. The signaling pathways for tyrosine kinase stimulation of integrin adhesiveness and their relation to pathways that regulate growth and differentiation over much longer time periods remain uncharacterized. We have studied the effector pathways by which receptor tyrosine kinases regulate cell-matrix adhesion using wild-type and mutant forms of the platelet-derived growth factor (PDGF) receptor, which is closely related to c-kit. The PDGF receptor expressed in mast cells is as potent as c-kit in stimulating adhesion to fibronectin. We show that induction of adhesion is regulated through two independent pathways of phosphatidylinositol 3 kinase (PI3K) and phospholipase C-gamma 1 (PLC gamma)-protein kinase C by elimination of autophosphorylation sites required for activation of PI3K and PLC gamma or in combination with downregulation of protein kinase C or wortmannin. By contrast, a receptor mutated in both the PI3K and PLC gamma association sites can still stimulate mast cell growth, indicating a crucial role of these effector molecules in regulating adhesion rather than cell growth.
Blood 1995 Sep 15
PMID:Receptor tyrosine kinase stimulates cell-matrix adhesion by phosphatidylinositol 3 kinase and phospholipase C-gamma 1 pathways. 754 20

To determine the potential role of autocrine growth factor production in regulating primitive human hematopoietic cell development, we examined highly purified CD34+, c-Kit+ marrow mononuclear cells for expression of c-Kit ligand (KL) and stem cell tyrosine kinase 1 (stk1) ligand (STK1-L). Normal marrow mononuclear cells coexpressing CD34 and c-Kit were isolated by a combination of immunomagnetic bead isolation and fluorescence-activated cell sorting. Purified cells were then screened for expression of KL and stk1-L mRNA using a sensitive reverse transcription-polymerase chain reaction method. Using this approach, expression of both cytokine genes at the mRNA level was found in this highly enriched cell population. We then examined the functional significance of these mRNAs by inhibiting their expression with antisense (AS) oligodeoxynucleotides (ODN). In comparison to untreated or control ODN treated cells, inhibition of KL led to a 70% and 89% inhibition in burst-forming unit-erythroid (BFU-E) and colony-forming unit-Mix (CFU-Mix) colonies but had no significant effect on CFU-granulocyte-macrophage (CFU-GM) cloning efficiency. In contrast, inhibition of STK1-L alone had no effect on colony formation. However, when STK1-L AS ODN was combined with KL AS ODN, additive inhibition of CFU-GM and CFU-MIX but not of BFU-E colonies was observed. These findings, along with those of our previous studies showing inhibition of primitive hematopoietic cell growth with antisense ODN directed towards the stk1 receptor, suggest the possibility that both receptor/ligand axes regulate primitive hematopoietic cell growth via an autocrine growth loop.
Blood 1995 Sep 15
PMID:Expression and physiologic significance of Kit ligand and stem cell tyrosine kinase-1 receptor ligand in normal human CD34+, c-Kit+ marrow cells. 754 21

Previous studies indicate that c-Kit is required for postnatal melanocyte development. To understand the precise mechanisms of c-Kit dependence, we studied melanocyte development in newborn C57BL/6 mice by means of peritoneal injection of a monoclonal anti-c-Kit antibody (ACK2), which blocks c-Kit functions. The mice were injected once or more with ACK2 at various intervals after birth. In experiment 1, skin samples were examined on day 10 post-partum and in experiment 2 they were examined daily until day 10 post-partum. We studied melanocytes in the hair follicles, epidermis, and dermis by light and electron microscopy with dopa reactions and immunohistochemistry. Epidermal melanocytes in untreated mice were dopa negative and c-Kit positive on day 0 post-partum but became dopa positive soon thereafter. In ACK2-treated mice, the earlier the mice received ACK2 injections after birth, the fewer melanocytes they had, not only in the epidermis, but also in follicles. In these mice, melanocytes that had undergone apoptosis in the dermis and the follicles were detected ultrastructurally. Some appeared to have produced tyrosinase, because they had dopa-positive melanosomes. These results suggest that melanocytes in newborn mice are c-Kit dependent and undergo apoptosis when c-Kit receptors are blocked by ACK2 in the early days after birth. During this c-Kit-dependent period, melanocytes differentiate from dopa negative to positive and migrate from the epidermis to hair follicles.
J Invest Dermatol 1995 Sep
PMID:Effects of monoclonal anti-c-kit antibody (ACK2) on melanocytes in newborn mice. 754 1

To investigate the role of the receptor-type tyrosine kinase, c-kit and its ligand, stem cell factor (SCF) in T cell development, we analyzed c-kit (W/W) and SCF (SI/SI) deficient mice. We also engrafted wild-type or SCF-deficient fetal thymi onto wild-type recipient mice and analyzed the rate of proliferation by in vivo bromodeoxyuridine labeling. The results show that the most immature thymocyte compartment defined as CD3-CD4-CD8- is significantly reduced in SI/SI grafts and W/W thymi compared with wild-type counterparts. Also, the expansion rate of these immature thymocytes in SI/SI graft is reduced by -50%. These experiments provide direct evidence for an important role for c-kit-SCF interactions in expansion of very early thymocytes.
Immunity 1995 Sep
PMID:Intrathymically expressed c-kit ligand (stem cell factor) is a major factor driving expansion of very immature thymocytes in vivo. 755 96

During Xenopus gastrulation, platelet-derived growth factor (PDGF) receptor-alpha is expressed in involuting marginal zone cells which migrate over ectodermal cells expressing PDGF-A. To investigate the role of PDGF signalling during this process, we have generated a novel point mutant of PDGF receptor-alpha analogous to the W37 mutation of c-kit. This molecule is a specific, potent, dominant inhibitor of PDGF signalling in vivo. Injection of RNA encoding this protein into Xenopus embryos prevents closure of the blastopore, leads to abnormal gastrulation and a loss of anterior structures. Convergent extension is not inhibited in these embryos, but rather, involuting mesodermal cells fail to adhere to the overlying ectoderm. PDGF may therefore be required for mesodermal cell-substratum interaction.
Development 1995 Sep
PMID:PDGF signalling is required for gastrulation of Xenopus laevis. 755 34

To study cytokine regulation of the 5-lipoxygenase (5-LO)/leukotriene (LT) synthase pathway we have developed mouse bone marrow-derived mast cells (BMMC) that minimally express each protein of the pathway by using a novel culture system, lacking interleukin (IL)-3. When mouse bone marrow cells were cultured for 5 weeks with 100 ng/ml c-kit ligand (KL) and 10 units/ml IL-10, a population of > 95% mast cells was obtained. These cells generated 8.3 +/- 4.5 ng of LTC4/10(6) cells and 8.1 +/- 2.4 ng of prostaglandin (PG) D2/10(6) cells after IgE-dependent activation. When these BMMC were cultured for 2-5 weeks more with 100 units/ml IL-3 in the continued presence of KL and IL-10, the IgE-dependent generation of LTC4 and PGD2 increased to 212 +/- 36 and 25.5 +/- 8.6 ng/10(6) cells, respectively. The dramatic increase in the IgE-dependent generation of LTC4 in response to IL-3 was accompanied by a concomitant increase in expression of 5-LO and 5-LO-activating protein and preceded the increased expression of cytosolic phospholipase A2 and LTC4 synthase. The recognition that IL-3 up-regulates the expression of each protein of the 5-LO pathway for the generation of LTC4 contrasts with our recent finding that KL up-regulates the expression of cytosolic phospholipase A2, prostaglandin endoperoxide synthase-1, and hematopoietic PGD2 synthase and increases the IgE-dependent generation of PGD2 in BMMC developed from bone marrow with IL-3. Thus, developmentally segregated regulation of the prostanoid and cysteinyl leukotriene pathways in lineage-related committed mast cell progenitors reveals the pleiotropism of this effector cell of allergic inflammation, a cytokine/growth factor basis for preferential expression of pathways of eicosanoid biosynthesis, and the particular role of IL-3 in regulating the expression of the proteins of the 5-LO/LTC4 synthase pathway.
J Biol Chem 1995 Sep 29
PMID:Interleukin-3 regulates development of the 5-lipoxygenase/leukotriene C4 synthase pathway in mouse mast cells. 755 81

Both normal and leukaemic human megakaryocytopoiesis are stimulated by several cytokines, including stem cell factor, granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-3, GM-CSF/interleukin-3 fusion protein, interleukin-6, interleukin-11, basic fibroblast growth factor and thrombopoietin, but are inhibited by tumour necrosis factor-alpha, platelet factor 4, beta-thromboglobulin, thrombin, interleukin-4, interferon-alpha and interferon-gamma. Human megakaryoblastic leukaemia cell lines have common biological features, including high expression of the megakaryocytic specific antigen: CD41; high expression of the early myeloid antigens: CD34 and CD33; constitutive expression of interleukin-6 and platelet-derived growth factor; complex karyotype picture; expression of c-kit: the stem cell factor receptor; growth-dependency or -stimulation by stem cell factor, interleukin-3 and/or GM-CSF; megakaryoblastic differentiation by phorbol-myristate-acetate; and in vivo tumorigenicity in mice is associated with marked fibrosis. Only a few agents including phorbol-myristate-acetate; vitamin D3, interferon-alpha, interferon-beta 2, erythropoietin and thrombin have been reported to induce megakaryocytic differentiation in the human megakaryoblastic leukaemia cells.
Leuk Res 1995 Sep
PMID:Characteristic biological features of human megakaryoblastic leukaemia cell lines. 756 68

The proto-oncogene, c-kit, encodes a transmembrane tyrosine kinase receptor (KIT) and plays an important role in haemopoiesis. We have identified a 95 kD soluble form of KIT (S-KIT) in culture supernatant of human megakaryoblastic cell line, CMK. To study the physiological significance of S-KIT, we have established a sensitive sandwich ELISA system. Serum samples from healthy individuals contained detectable amounts of S-KIT. Next, we determined a total of 220 samples from 134 patients with haemopoietic disorders. A considerable number of patients with acute myeloid leukaemia (AML), especially those with more immature phenotypes (M0, M1 or M2) had elevated levels of serum S-KIT. Those levels decreased to the normal range after effective chemotherapy. In chronic myeloid leukaemia, patients with myeloid blastic crisis showed markedly elevated levels of serum S-KIT. In contrast, S-KIT levels decreased in cases with either acute or chronic lymphoid leukaemia. There was a tendency for patients with severe aplastic anaemia to show decreased levels, but it was not significant. In myelodysplastic syndrome, S-KIT levels appeared to vary by subsets, with higher concentration in more advanced forms of the disease. Although the functional role of S-KIT is not yet elucidated, these results suggest that the serum S-KIT levels may reflect the pathological states of various haematological disorders.
Br J Haematol 1995 Sep
PMID:Soluble c-kit molecule in serum from healthy individuals and patients with haemopoietic disorders. 757 39

We analysed c-Kit expression during erythroid differentiation using immunocytochemical staining and flow cytometric analysis. Burst-forming units-erythroid (BFU-E)-derived cell aggregates were identified in methylcellulose cultures containing human umbilical cord blood CD34+ cells and were stained by the indirect immunoalkaline phosphatase method. To investigate the changes in levels of cell-surface c-Kit expression, we subjected progenitor cells in liquid culture to flow cytometric analysis. In addition, the effects of stem cell factor (SCF) on cell-surface c-Kit expression were analysed in these two culture systems and the effects of SCF on erythroid colony formation were studied in a methylcellulose culture. c-Kit was expressed on the cell surface from BFU-E to erythroid precursors recognized morphologically as basophilic erythroblasts. Flow cytometric analysis showed that c-Kit expression increased until 6 d in liquid culture, and that decreased expression of c-Kit was associated with the increased expression of glycophorin A. Moreover, SCF increased the size of erythroid colonies when added at days 0, 4 and 8 in methylcellulose cultures. These results indicate that the c-Kit/SCF system still plays in proliferation of erythroid progenitor cells at the colony-forming units-erythroid stage. Finally, expression of c-Kit in erythroid progenitor cells cultured without SCF showed a diffuse pattern on the cell surface, whereas we observed positive c-Kit immunoreactivity in the region of the Golgi apparatus of these cells cultured with SCF. Flow cytometric analysis also showed that the levels of cell-surface c-Kit expression decreased in the presence of SCF. These results suggest that SCF induced down-modulation of cell-surface c-Kit expression, despite continuous synthesis of c-Kit protein.
Br J Haematol 1995 Sep
PMID:Changes in c-Kit expression and effects of SCF during differentiation of human erythroid progenitor cells. 757 48


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