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

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Query: EC:2.7.11.13 (protein kinase C)
49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Products of the ras gene family, termed p21ras, are GTP-binding proteins that have been implicated in signal transduction via receptors encoding tyrosine kinase domains. Recent findings have defined a superfamily of hemopoietin receptors that includes receptors for a number of interleukins and colony-stimulating factors. The intracellular portions of these receptors show only restricted homologies, have no tyrosine kinase domain, and provide no clues to the mode of signal transduction. However, in most cases the factors stimulate tyrosine phosphorylation. We demonstrate here that ligand-induced activation of the interleukin (IL)-2, IL-3, IL-5, and granulocyte-macrophage colony-stimulating factor receptors resulted in activation of p21ras in various hemopoietic cell lines. The only cytokine tested that binds to a hemopoietin receptor and that did not activate p21ras was IL-4. Activation of p21ras was also observed in response to Steel factor, which stimulates the endogenous tyrosine kinase activity of the c-kit receptor, as well as with phorbol esters, which activate protein kinase C. Experiments with protein kinase inhibitors implicated tyrosine kinase activity, but not protein kinase C activity, as the upstream signal in p21ras activation via these growth factor receptors. Attempts to demonstrate tyrosine phosphorylation of the p21ras GTPase-activating protein (GAP) were negative, suggesting that phosphorylation of GAP may not be the major mechanism for regulation of p21ras activity by tyrosine kinases.
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PMID:p21ras activation via hemopoietin receptors and c-kit requires tyrosine kinase activity but not tyrosine phosphorylation of p21ras GTPase-activating protein. 137 79

The c-kit ligand, KL, and its receptor, the proto-oncogene c-kit are encoded, respectively, at the steel (Sl) and white spotting (W) loci of the mouse. Both Sl and W mutations affect cellular targets in melanogenesis, gametogenesis, and hematopoiesis during development and in adult life. Although identified as a soluble protein, the predicted amino acid sequence of KL indicates that it is an integral transmembrane protein. We have investigated the relationship between the soluble and the cell associated forms of KL and the regulation of their expression. We show that the soluble form of KL is generated by efficient proteolytic cleavage from a transmembrane precursor, KL-1. An alternatively spliced version of KL-1, KL-2, in which the major proteolytic cleavage site is removed by splicing, is shown to produce a soluble biologically active form of KL as well, although with somewhat diminished efficiency. The protein kinase C inducer phorbol 12-myristate 13-acetate and the calcium ionophore A23187 were shown to induce the cleavage of both KL-1 and KL-2 at similar rates, suggesting that this process can be regulated differentially. Furthermore, proteolytic processing of both the KL-1 and KL-2 transmembrane protein products was shown to occur on the cell surface. The relative abundance of KL-1 and KL-2 is controlled in a tissue-specific manner. Sld, a viable steel allele, is shown to encode a biologically active secreted mutant KL protein. These results indicate an important function for both the soluble and the cell associate form of KL. The respective roles of the soluble and cell associated forms of KL in the proliferative and migratory functions of c-kit are discussed.
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PMID:Differential expression and processing of two cell associated forms of the kit-ligand: KL-1 and KL-2. 137 27

Human interleukin-9 (IL-9) was originally identified and cloned based on its stimulatory effect on proliferation of human myeloid cell line, M07e. IL-9 synergized with Steel factor, the ligand for the c-kit product, to stimulate M07e cell proliferation. To investigate potential mechanisms for this, IL-9 was assessed for effects on protein tyrosine kinase activities in M07e cells by immunoblotting with anti-phosphotyrosine monoclonal antibody; results were compared with those of Steel factor alone and in combination with IL-9, and those of 12-0-tetradecanoyl phorbol-13-acetate (TPA). Recombinant human IL-9 (10 ng/mL) rapidly and transiently induced or enhanced at least four tyrosine phosphorylated protein bands with molecular weights of 105, 97, 85, and 81 Kd. This tyrosine phosphorylation pattern was different from that generated by recombinant murine Steel factor or TPA stimulation and the combination of IL-9 and Steel factor did not change the IL-9-induced pattern. IL-9-induced tyrosine phosphorylated bands were completely blocked by treatment of IL-9 with anti-IL-9 antibody under conditions that also neutralized the synergistic effect of IL-9 with Steel factor on M07e cell proliferation. Genistein, a tyrosine kinase inhibitor, blocked phosphorylation of IL-9 and Steel factor-induced bands. Unlike Steel factor or TPA, IL-9 did not appear to stimulate phosphorylation of 42-Kd mitogen-activated protein (MAP) kinase or Raf-1, or enhance MAP kinase activity. MAP kinase and Raf-1 are serine/threonine kinases that are phosphorylated and activated by many growth factors and by agonists for protein kinase C. While the combination of IL-9 plus SLF did not appear to induce phosphorylation of new bands not already seen with either IL-9 or SLF alone, or enhance the phosphorylation of those bands seen with either cytokine alone, the results suggest that IL-9 activates specific and unique signal transduction pathways.
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PMID:Recombinant human interleukin-9 induces protein tyrosine phosphorylation and synergizes with steel factor to stimulate proliferation of the human factor-dependent cell line, M07e. 138 99

A panel of 164 continuous human leukemia-lymphoma cell lines was analyzed for expression of c-kit using Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). The c-kit transcripts were detectable in cell lines assigned to the myeloid (in 7 of 29 by Northern blotting and in 4 of 8 by RT-PCR), monocytic (in 1 of 24 by Northern blotting and in 3 of 6 by RT-PCR), erythroid (in 6 of 8 by Northern blotting and in 5 of 5 by RT-PCR), and megakaryoblastic (in 10 of 10 by Northern blotting) lineages, c-kit expression was not seen by Northern blotting or RT-PCR analysis in any of the 93 lymphoid leukemia, myeloma, or lymphoma cell lines. Treatment of four megakaryoblastic cell lines with protein kinase C activators (phorbol ester 12-O-tetradecanoylphorbol 13-acetate and Bryostatin 1) led to terminal differentiation as assessed by morphologic alterations, changes in the surface marker profile, and growth arrest. These effects were associated with enhanced c-kit mRNA expression. Exposure to all-trans retinoic acid down-regulated c-kit mRNA levels, while simultaneously causing morphologic alterations in all four cell lines. Stimulation with growth factors (interleukin-3, granulocyte macrophage-colony stimulating factor, and insulin-like growth factors I and II), used to assess any role of c-kit in proliferative processes, did not lead to significant upregulation or downregulation of c-kit expression. The finding of constitutive and high expression of c-kit mRNA in all megakaryoblastic leukemia cell lines and its modulation by various reagents might further contribute to the understanding of megakaryopoietic proliferation, differentiation, and leukemogenesis.
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PMID:c-kit expression in human megakaryoblastic leukemia cell lines. 751 41

The mast cell growth factor (MGF) affects migration, proliferation and differentiation of erythroid and myeloid progenitor cells by binding to a transmembrane receptor tyrosine kinase encoded by the c-Kit proto-oncogene. By using MGF-dependent human myeloid cell lines (M-07e and TF-1), here we show that a Kit-related 100 kDa protein is associated with the cell but it undergoes release into the medium upon treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C. Immunological analysis with a series of antibodies to Kit indicated that the released protein (p100Kit) contains the whole glycosylated extracellular portion of the transmembrane Kit protein (p145Kit). The secreted protein retained the ability to specifically bind MGF. Moreover, p100Kit was able to block the mitogenic effect of MGF on cultured M-07e cells, suggesting that the soluble protein may function as a physiological antagonist of MGF.
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PMID:Protein kinase C-dependent release of a functional whole extracellular domain of the mast cell growth factor (MGF) receptor by MGF-dependent human myeloid cells. 751 83

The murine interleukin-3 (IL-3) dependent cell line, B6SUtA1, which expresses high IL-3 receptor (IL-3R) numbers, was found to proliferate in a greater than additive fashion when grown in the presence of IL-3 and steel factor (SF). However, pretreatment of these cells with SF had no effect on the number of IL-3Rs expressed at the cell surface nor their affinity for IL-3. Interestingly, although, SF did induce the rapid and transient serine- and threonine-specific phosphorylation of the beta IL-3 subunit of the IL-3R. This serine/threonine phosphorylation was also observed with the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate, and both the 12-O-tetradecanoylphorbol-13-acetate- and SF-induced phosphorylation of the IL-3R could be inhibited with the highly specific protein kinase C inhibitor, bisindolylmaleimide (Compound 3), suggesting that SF might be stimulating this phosphorylation via protein kinase C. This SF-induced phosphorylation also occurred within 10 min of incubation at 4 degrees C, indicating that this might be a relatively early event in the c-kit signaling pathway. Last, this SF-induced phosphorylation of the IL-3R occurred in the presence of the tyrosine kinase inhibitor, genistein, at levels which blocked the autophosphorylation of c-kit. This suggests that c-kit might be capable of mediating this cross-talk phenomenon in the absence of its endogenous tyrosine kinase activity.
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PMID:Steel factor stimulates the serine/threonine phosphorylation of the interleukin-3 receptor. 751 84

The human c-kit receptor ligand, rhSCF, is the only cytokine known to be active on human mast cells, but its intracellular signal transduction pathway is still unknown. We compared the effect of rhSCF on intracellular Ca2+ levels in purified (> 70% pure) adult skin mast cells with two other immunologic stimuli, namely, anti-IgE and substance P. Both rhSCF (1 microgram/mL) and anti-IgE (3 micrograms/mL) induced a rapid (< 20 sec) and sustained (T1/2 for decay > 10 min) increase in free cytosolic Ca2+ concentration. In contrast, substance P (5 microM) elicited a very rapid (< 1 sec) and transient (T1/2 for decay congruent to 5 sec) rise in intracellular Ca2+ levels. Intracellular cAMP levels were then increased by pharmacologic means to examine the role of the cyclic nucleotide in controlling the Ca2+ response in skin mast cells. A combination of the general phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX) (200 microM) and the adenylate cyclase activator, forskolin (30 microM) was effective in inhibiting the Ca2+ response induced by rhSCF or anti-IgE (82 and 68% inhibition, respectively), while IBMX and forskolin alone were much less effective. The phosphodiesterase isozyme IV inhibitor, rolipram (10 microM), variably affected the increase in Ca2+ levels induced by anti-IgE, but it exerted a significant inhibitory activity on anti-IgE- or rhSCF-induced response in the presence of forskolin (30 micrograms/mL) (33 and 67%, respectively). Two different protein kinase C (PKC) activators TPA (200 nM) and bryostatin 1 (200 nM) similarly inhibited rhSCF- (22 and 32%, respectively) and anti-IgE-induced (24 and 32%) Ca2+ response. Finally, the kinase inhibitor genistein (30 micrograms/mL) was a somewhat more effective inhibitor of the rise in intracellular Ca2+ induced by rhSCF (100%) than that activated by anti-IgE (54%) (P < 0.05). These data indicate that rhSCF and anti-IgE may act on human mast cells through a common pathway to increase free cytosolic Ca2+ levels and this effect is similarly modulated by various drugs.
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PMID:Studies of the intracellular Ca2+ levels in human adult skin mast cells activated by the ligand for the human c-kit receptor and anti-IgE. 751 34

The receptor tyrosine kinase Kit and Kit ligand (KL), encoded at the murine white spotting (W) and steel (Sl) loci, respectively, function in hematopoiesis, melanogenesis, and gametogenesis. To understand the mechanism of turnover of Kit in mast cells, mutant receptors generated in vitro were heterologously expressed in Wsb/Wsh mast cells lacking endogenous c-kit expression, and the effects of mutations on KL-induced internalization and ubiquitination/degradation of Kit were studied. Upon binding of KL, KL.Kit receptor complexes were rapidly internalized, and the turnover was accelerated by ubiquitin-mediated degradation. Inactivation of the Kit kinase resulted in a reduced rate of internalization of KL.Kit complexes, degradation of kinase-inactive receptor complexes was relatively slow, and receptor ubiquitination was absent. But abolishment of KL-induced receptor association and activation of phosphatidylinositol 3'-kinase and of tyrosine 821 autophosphorylation did not affect KL-induced internalization and ubiquitination/degradation of Kit. Furthermore, Kit receptors can be down-regulated by proteolytic cleavage induced by either activation of protein kinase C or by isopropyl alcohol. In summary, KL-induced internalization of KL.Kit complexes and ubiquitination/degradation require an active kinase. By contrast, proteolytic cleavage of Kit mediated by protein kinase C activation is independent of kinase activity.
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PMID:Mechanism of down-regulation of c-kit receptor. Roles of receptor tyrosine kinase, phosphatidylinositol 3'-kinase, and protein kinase C. 752 1

In previous in vitro studies we found that contact between mouse primordial germ cells and other cell types (neighbouring somatic cells or established TM4 or STO cell lines) is crucial for supporting primordial germ cell survival and proliferation and for activating their motility. We have studied primordial germ cell adhesion to different cell monolayers (STO, TM4, COS and F9 cells) as an in vitro model for interactions between primordial germ cells and cellular substrates. The results suggest that these cell interactions are mediated by multiple mechanisms involving Steel factor and its receptor encoded by c-kit, carbohydrates and possibly other unknown factors. We find that Steel factor and leukaemia inhibitory factor are survival rather than proliferation factors for primordial germ cells. Both molecules prevent primordial germ cell death in culture by suppressing apoptosis. Morphological and molecular features of primordial germ cell apoptosis in vitro are reported. Activation of protein kinase C does not promote primordial germ cell proliferation, but compounds known to enhance intracellular levels of cAMP (i.e. dibutyryl cAMP and forskolin) markedly stimulate primordial germ cells to proliferate in culture. We have preliminary results indicating that neuropeptides PACAP-27 and PACAP-28 are possible physiological activators of adenylate cyclase in primordial germ cells.
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PMID:Interactions between migratory primordial germ cells and cellular substrates in the mouse. 753 Jun 18

We previously reported that the K562 cell line K562YO expressed a high level of the c-kit gene. In this study, we analyzed the mechanism of this expression and investigated the effects of the serine/threonine kinases such as protein kinase C (PKC) and cyclic adenosine 3',5'-monophosphate (cAMP)-dependent kinase (PKA) on it. The half-life of the c-kit mRNA in K562YO cells was greater than 10 hours, compared with 2 hours in the original K562 cells, which expressed a very low level of c-kit mRNA. This prolonged half-life can contribute to the high level of c-kit expression in K562YO cells. Cycloheximide (CHX), a protein synthesis inhibitor, caused increases in c-kit mRNA levels in K562YO cells. 12-O-tetradecanoylphorbol-13-acetate (TPA), by which PKC was activated at first and downregulated in a late phase, gradually decreased c-kit mRNA in K562YO cells until 9 hours and then returned to the control level 24 hours after treatment. TPA also rapidly decreased c-kit protein level on the membranes. In whole cells, c-kit protein was also decreased 6 hours after incubation with TPA. Calphostin C, a light-dependent PKC inhibitor, decreased c-kit mRNA levels within 30 minutes in a light-dependent manner. It also decreased c-kit protein in whole cells 2 hours after the addition. However, it increased the amount of c-kit protein on the cell surfaces. Dibutyryl cyclic AMP (dbc-AMP) increased c-kit mRNA as well as c-kit protein on membranes and in whole cells. Run-on transcriptional assay suggested that the agent (dbc-AMP) enhanced the transcription rate of the gene. These results suggest that c-kit protein on the membranes is downregulated by PKC activation and upregulated by PKC inhibition. In the whole cell lysate, c-kit proteins are decreased by PKC inhibition through downregulation of mRNA. On the other hand, the elevation of an intracellular cAMP level causes upregulation of both the mRNA and c-kit protein on membranes and in whole cells through enhanced transcription. Thus, c-kit gene expression is apparently modulated by PKC and PKA.
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PMID:High expression of c-kit in K562YO cells due to the prolonged half-life of its mRNA: the effects of modification with serine/threonine kinase signals. 753 32


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