Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated activation of mitogen-activated protein kinase (MAPK) subtype cascades in human neutrophils stimulated by IL-1beta. IL-1beta induced phosphorylation and activation of p38 MAPK and phosphorylation of MAPK kinase-3/6 (MKK3/6). Maximal activation of p38 MAPK was obtained by stimulation of cells with 300 U/ml IL-1beta for 10 min. Extracellular signal-regulated kinase (ERK) was faintly phosphorylated and c-Jun N-terminal kinase (JNK) was not phosphorylated by IL-1beta. IL-1beta primed neutrophils for enhanced release of superoxide (O(2)(-)) stimulated by FMLP in parallel with increased phosphorylation of p38 MAPK. IL-1beta also induced O(2)(-) release and up-regulation of CD11b and CD15, and both responses were inhibited by SB203580 (p38 MAPK inhibitor), suggesting that p38 MAPK activation mediates IL-1beta-induced O(2)(-) release and up-regulation of CD11b and CD15. Combined stimulation of neutrophils with IL-1beta and G-CSF, a selective activator of the ERK cascade, resulted in the additive effects when the priming effect and phosphorylation of p38 MAPK and ERK were assessed. IL-1beta induced phosphorylation of ERK and JNK as well as p38 MAPK in human endothelial cells. These findings suggest that 1) in human neutrophils the MKK3/6-p38 MAPK cascade is selectively activated by IL-1beta and activation of this cascade mediates IL-1beta-induced O(2)(-) release and up-regulation of CD11b and CD15, and 2) the IL-1R-p38 MAPK pathway and the G-CSF receptor-ERK pathway work independently for activation of neutrophils.
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PMID:Selective activation of p38 mitogen-activated protein kinase cascade in human neutrophils stimulated by IL-1beta. 1169 72

The granulocyte colony-stimulating factor receptor (G-CSFR) regulates the proliferation, differentiation and survival of neutrophilic progenitor cells. In these studies, we introduced mutant G-CSFRs with cytoplasmic domains truncated approximately every 30 amino acids from the C-terminus into interleukin-3 (IL-3)-dependent myeloid LGM-1 cells. The G-CSFR membrane proximal region containing the Box 2 homology sequence was determined to be critical for proliferative signaling, as well as for activation of Janus kinase (JAK2) and p44/42 mitogen-activated protein kinase (MAPK) following G-CSF stimulation. In the presence of increasing concentrations of JAK2 or p44/42 MAPK inhibitors, LGM-1 cells expressing the full-length G-CSFR exhibited a decreased capacity to proliferate in response to G-CSF. These results demonstrate that JAK2 and p44/42 MAPK activation is involved in proliferative signaling through the G-CSFR membrane proximal region containing the Box 2 homology sequence.
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PMID:Distinct region of the granulocyte colony-stimulating factor receptor mediates proliferative signaling through activation of Janus kinase 2 and p44/42 mitogen-activated protein kinase. 1181 52

Activation of the MEK/ERK/MAP kinase signaling pathway promotes the proliferation and survival of hematopoietic cells. The kinases MEK-1, MEK-2, ERK-1/MAPK and ERK-2/MAPK are activated by phosphorylation at specific sites, and these events can be monitored using phospho-specific antibodies. In this report we examined the importance of the MEK/ERK/MAP kinase pathway in the monocytic and granulocytic differentiation of myeloid cell lines. Induction of monocytic differentiation in HL-60 cells by treatment with phorbol 12-myristate 13-acetate (PMA) led to rapid and sustained activation of MEK-1/-2, ERK-1/MAPK and ERK-2/MAPK, while induction of granulocytic differentiation by retinoic acid (RA) caused similar activation of MEK-1/-2 and ERK-2/MAPK, but not ERK-1/MAPK. The total levels of these kinases were not affected during the course of differentiation along either pathway. Pretreatment of cells with 5 microM of the MEK-1/-2-specific inhibitor U0126 abrogated PMA- or RA-induced activation of ERK-1/MAPK and ERK-2/MAPK. Importantly, pretreatment of HL-60 cells with U0126 was found to potently inhibit both monocytic and granulocytic differentiation, as assessed by cytochemical staining for non-specific esterase or nitroblue tetrazolium reduction, flow cytometric analysis of myeloid surface markers, and immunoblotting for the cell cycle inhibitor p21 WAF1/Cip1. Similar results were seen in U937 cells, where U0126 inhibited PMA-induced monocytic differentiation, and in 32D cells, where G-CSF-induced granulocytic differentiation was inhibited by U0126 pretreatment. Additional experiments revealed that inhibition of MEK-1/-2 in HL-60 cells resulted in nearly complete inhibition of differentiation-induced cell death during monocytic differentiation. By contrast, U0126 only partially inhibited cell death resulting from granulocytic differentiation. Taken together, our findings demonstrate that the MEK/ERK/MAP kinase signaling pathway is activated, and plays a critical role, during both monocytic and granulocytic differentiation of myeloid cell lines.
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PMID:Importance of MEK-1/-2 signaling in monocytic and granulocytic differentiation of myeloid cell lines. 1196 Mar 50

Neutrophils from patients with myelodysplastic syndrome (MDS) show a disturbed differentiation pattern and are generally dysfunctional. To study these defects in more detail, we investigated reactive-oxygen species (ROS) production and F-actin polymerization in neutrophils from MDS patients and healthy controls and the involvement of N-formyl-L-methionyl-L-lucyl-L-phenylaline (fMLP) and granulocyte macrophage-colony-stimulating factor (GM-CSF)-stimulated signal transduction pathways. Following fMLP stimulation, similar levels of respiratory burst, F-actin polymerization, and activation of the small GTPase Rac2 were demonstrated in MDS and normal neutrophils. However, GM-CSF and G-CSF priming of ROS production were significantly decreased in MDS patients. We subsequently investigated the signal transduction pathways involved in ROS generation and demonstrated that fMLP-stimulated ROS production was inhibited by the phosphatidylinositol 3 kinase (PI3K) inhibitor LY294002, but not by the MAPK/ERK kinase (MEK) inhibitor U0126. In contrast, ROS production induced by fMLP stimulation of GM-CSF-primed cells was inhibited by LY294002 and U0126. This coincides with enhanced protein kinase B (PKB/Akt) phosphorylation that was PI3K dependent and enhanced extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) phosphorylation that was PI3K independent. We demonstrated higher protein levels of the PI3K subunit p110 in neutrophils from MDS patients and found that though the fMLP-induced phosphorylation of PKB/Akt and ERK1/2 could also be enhanced by pretreatment with GM-CSF in these patients, the degree and kinetics of PKB/Akt and ERK1/2 phosphorylation were significantly disturbed. These defects were observed despite a normal GM-CSF-induced signal transducer and activator of transcription 5 (STAT5) phosphorylation. Our results indicate that the reduced priming of neutrophil ROS production in MDS patients might be caused by a disturbed convergence of the fMLP and GM-CSF signaling routes.
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PMID:Decreased phosphorylation of protein kinase B and extracellular signal-regulated kinase in neutrophils from patients with myelodysplasia. 1252 94

We have evaluated the contribution of intracellular tyrosine residues of the granulocyte colony-stimulating factor receptor (GCSF-R) to its signaling and cellular outcomes. We began with stable BaF3 cell lines overexpressing wild-type or mutant GCSF-Rs. When all four intracellular tyrosines of the GCSF-R were replaced with phenylalanine (FFFF GCSF-R), cell proliferation and survival were compromised. Replacement of only the membrane-distal tyrosine (YYYF GCSF-R) also showed reduced survival following a GCSF withdrawal/replacement protocol, suggesting a role for this tyrosine. Proliferation by FFFY GCSF-R cells was attenuated by approximately 70%. In evaluating the biochemical steps involved in signaling, we then showed that the membrane-distal tyrosine was necessary and sufficient for c-Jun N-terminal kinase (JNK) activation. With the use of a cell-permeable JNK-inhibitory peptide, JNK was implicated in the proliferation of the FFFY GCSF-R mutant. To further define the events linking the membrane-distal tyrosine and JNK activation, the Src homology 2 domains of Shc, Grb2, and 3BP2 were shown to bind the full-length GCSF-R and a phosphopeptide encompassing the membrane-distal tyrosine. When binding to variant phosphopeptides based on this membrane-distal tyrosine was tested, altering the amino acids immediately following the phosphotyrosine could selectively abolish the interaction with Shc or Grb2, or the binding to both Grb2 and 3BP2. When these changes were introduced into the full-length GCSF-R and new cell lines created, only the mutant that did not interact with Grb2 and 3BP2 did not activate JNK. Our results suggest that direct binding of Shc by the GCSF-R is not essential for JNK activation.
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PMID:Contribution of the membrane-distal tyrosine in intracellular signaling by the granulocyte colony-stimulating factor receptor. 1455 62

The granulocyte colony-stimulating factor receptor (G-CSFR) transduces intracellular signals for myeloid cell proliferation, survival, and differentiation through the recruitment of nonreceptor protein tyrosine kinases Lyn and janus kinase 2 (Jak2). This results in the tyrosine phosphorylation of a small set of positive and negative adapters and effectors. Grb2-associated binder-2 (Gab2) is a newly described adapter molecule, preferentially expressed in hematopoietic cells and associated with phosphatidylinositol 3 (PI3) kinase. Studies suggest that Gab2 plays both positive and negative roles in cytokine receptor signaling. To investigate the role Gab2 plays in G-CSF receptor-mediated signaling, we have analyzed its activation state and correlated that with wild-type and mutant G-CSF receptors stably expressed in the murine factor-dependent Ba/F3 cell lines. G-CSF-induced tyrosine phosphorylation of Gab2 occurred in the wild-type and single Y-to-F mutants (Y704F, Y729F, and Y744F), but not in the ADA and W650R loss-of-function mutants. Cells expressing truncated proximal G-CSFR, the tyrosine-null (Y4F) G-CSFR, or Y764F mutant receptors had decreased phosphorylation of Gab2. Specific inhibitors of Src kinase (PD173 and PP1) but not Jak2 kinase (AG490) blocked Gab2 phosphorylation. Phosphorylation of Gab2 occurred in wild-type, but not Lyn-deficient, G-CSFR-transfected DT40 B cells. These data propose that Lyn, not Jak2, phosphorylates Gab2 and that maximal phosphorylation of Gab2 requires Y764, a Grb2-binding site. Serine phosphorylation of Akt, a marker of PI3-kinase activity, was detected in both wild-type and truncated proximal domain receptors, but not in the ADA and W650R mutants. Levels of phospho-Akt and phospho-extracellular signal-regulated kinase (phospho-ERK) were greater in proximal truncated than in wild-type G-CSFR cells, suggesting that Gab2 is dissociated from PI3 kinase or ERK activities. Overexpression of Gab2 enhanced the phosphorylation state of Akt, but not of ERK. This inhibited the proliferation of wild-type and truncated G-CSFR-transfected Ba/F3 cells and enhanced their myeloid differentiation. All together, these data indicate that G-CSF treatment leads to Lyn-mediated tyrosine phosphorylation of Gab2, which may serve as an important intermediate of enhanced Akt activity and myeloid differentiation, not growth/survival response.
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PMID:G-CSF-induced tyrosine phosphorylation of Gab2 is Lyn kinase dependent and associated with enhanced Akt and differentiative, not proliferative, responses. 1465 92

PBK/TOPK is a recently identified 322 amino acid serine/threonine kinase that is phosphorylated during mitosis and may include p38 MAPK among its targets. Previous work has shown up-regulated expression of PBK/TOPK mRNA in a variety of tumor cell lines and fetal tissues, suggesting a role for this kinase in malignant cell proliferation. In this paper, PBK/TOPK protein expression was examined in a variety of primary hematologic neoplasms: PBK/TOPK was readily detected in 9 of 12 AML samples (75%), in 3 of 3 ALL samples, and in 1 sample each of a plasmacytoma and blastic type mantle cell lymphoma where it was strongly expressed. In contrast, PBK/TOPK was only weakly expressed in 2 samples of G-CSF-mobilized peripheral blood stem cells that were enriched in CD34+ progenitors by immunoselection. Furthermore, when HL-60 myeloid leukemic cells were differentiated with phorbol ester (TPA), PBK/TOPK protein expression was strongly down-regulated by 24 h. Under these same conditions, phosphorylated c-Myc was rapidly down-regulated (by 4 h), while the levels of cyclin D1 and phosphorylated p38 were constant. Notably, of 5 clinical samples that strongly expressed PBK/TOPK, 4 also strongly expressed phosphorylated c-Myc, while only 1 of 3 PBK/TOPK negative samples expressed phosphorylated c-Myc. These data show that PBK/TOPK protein is up-regulated in a variety of hematologic malignancies and may be involved in leukemic cell growth. Additional studies are warranted to determine if PBK/TOPK would be a valuable target for novel therapeutics. To this end, we also describe the derivation of clones of 293 (human embryonic kidney) cells, which carry an inducible kinase-defective mutant of PBK/TOPK. This model may be useful for studying the effects of down-regulated PBK/TOPK function.
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PMID:Protein expression of PDZ-binding kinase is up-regulated in hematologic malignancies and strongly down-regulated during terminal differentiation of HL-60 leukemic cells. 1475 41

It is known that Notch activation promotes the self-renewal of hematopoietic cells. However, we have previously found that the growth of a myeloid leukemia cell line, OCI/AML-6, was suppressed by Notch activation induced by stimulation with a recombinant Notch ligand, Delta-1 protein. We recently found that the growth of another leukemia cell line, THP-1, was also suppressed by the ligands Delta-1 and Jagged-1. In this study, we tried to clarify the cellular and molecular mechanism of the growth suppression induced by Notch activation. Flow cytometric analysis showed that Delta-1 stimulation increased the expression of differentiation markers such as CD11b and CD13 while it decreased the expression of CD117 (c-KIT), a marker for primitive cells in THP-1 cells. In OCI/AML-6 cells, Delta-1 stimulation decreased the expression of CD11b and CD14 and increased CD34 expression. Namely, Delta-1 showed the opposite effects on the differentiation markers of each cell line. Delta-1 stimulation did not increase the binding of annexin V, a marker for apoptotic cells in either cell line. Since the growth of myeloid cells is regulated by MAP kinase and JAK/STAT pathways, we investigated the effects of the ligand stimulation on these pathways. Delta-1 stimulation did not induce the phosphorylation of ERK1/2 and STAT3 proteins in either cell line. Pre-exposure to Delta-1 did not affect the phosphorylation of ERK1/2 and STAT3 induced by G-CSF in OCI/AML-6 cells, either. Namely, it is thought that these pathways are not involved in the growth suppression caused by Notch ligands. Our study revealed several findings on Notch function. However, the precise mechanism remains to be elucidated.
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PMID:Cellular analysis of growth suppression induced by the Notch ligands, Delta-1 and Jagged-1 in two myeloid leukemia cell lines. 1525 69

Use of all-trans-retinoic acid (ATRA) in combinatorial differentiation therapy of acute promyelocytic leukemia (APL) results in exceptional cure rates. However, potent cell differentiation effects of ATRA are so far largely restricted to this disease and long-term survival rates in non-APL acute myelogeneous leukemia (AML) remain unacceptably poor, requiring development of novel therapeutic strategies. We demonstrate here that myelomonocytic growth factors (granulocyte colony-stimulating factor [G-CSF] and/or granulocyte macrophage colony-stimulating factor [GM-CSF]) potentiate differentiation effects of ATRA in different AML cell lines and primary cells from patients with myeloid leukemia. The ligand-dependent activities of endogenous and transiently expressed retinoic acid receptor alpha (RARalpha) isoforms can be potentiated by G/GM-CSF in U-937 cells and correlate with increased expression of ATRA-inducible RARalpha2 isoform. Specific inhibitors of mitogen mitogen-activated protein kinase (MAPK) (MEK)-1/-2 or p38 extracellular signal-related kinase (ERK) kinase diminish the ATRA as well as ATRA and G/GM-CSF-induced activation of the RARalpha proteins and decreased the differentiation-induced decline in cell numbers. Our data demonstrate that acting, at least in part, via the MAP kinase pathways, myelomonocytic growth factors enhance ATRA-dependent activation of the RARalpha isoforms and maturation of myeloid leukemia cells. These results suggest that combinatorial use of these agents may be effective in differentiation therapy of AML.
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PMID:Retinoids and myelomonocytic growth factors cooperatively activate RARA and induce human myeloid leukemia cell differentiation via MAP kinase pathways. 1533 53

The modifying effects of a Kunitz trypsin inhibitor (KTI) and a Bowman-Birk trypsin inhibitor (BBI), purified from soybean trypsin inhibitor, as dietary supplements on experimental and spontaneous pulmonary metastasis of murine Lewis lung carcinoma 3LL cells as well as peritoneal disseminated metastasis model in human ovarian cancer HRA cells were investigated in i.v., s.c. and i.p. injection models in mice. Seven groups of female C57BL/6 or nude mice were fed a basal diet (control group) or the basal diet supplemented with KTI or BBI (5, 15, or 50 g/kg). Here we show that, in an in vivo spontaneous metastasis assay, the diet supplementation with KTI (15 and 50 g/kg), but not with BBI, for 28 days immediately after s.c. tumor cell inoculation significantly inhibited the formation of lung metastasis in C57BL/6 mice in a dose-dependent manner. The inhibition of lung metastasis was not due to direct antitumor effects of KTI. In an in vivo experimental metastasis assay, the diet supplementation with KTI or BBI for 21 days after i.v. tumor cell inoculation did not reduce the number of lung tumor colonies. In addition, KTI (15 or 50 g/kg) treatment in a peritoneal disseminated metastasis model of HRA cells resulted in a 40% reduction in total tumor burden when compared with control animals. Immunoblot analysis revealed that KTI specifically reduced expression of uPA protein as well as phosphorylation of MAP kinase and PI3 kinase proteins in the cells stimulated with agonists (G-CSF for 3LL cells or TGF-beta1 for HRA cells). These results suggest that dietary supplementation of KTI more efficiently regulates the mechanism involved in the entry into vascular circulation of tumor cells (intravasation) than in extravasation during the metastatic process. KTI treatment may also be beneficial for ovarian cancer patients with or at risk for peritoneal disseminated metastasis; it greatly reduces tumor burden in part by inhibiting phosphorylation of MAP kinase and PI3 kinase, leading to suppression of uPA expression.
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PMID:Suppressing effects of dietary supplementation of soybean trypsin inhibitor on spontaneous, experimental and peritoneal disseminated metastasis in mouse model. 1538 80


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