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

---

Query: EC:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibition of signaling through Ras in BCR-ABL-positive pluripotent K562 cells leads to apoptosis and spontaneous differentiation. However, Ras-induced activation of the mitogen-activated protein kinase ERK has been suggested to play a critical role in either growth or differentiation in different model systems. We studied the role of ERK activation in the growth-promoting and anti-apoptotic effect of Ras and its involvement in hemin-induced nonterminal erythroid differentiation using the BCR-ABL-positive K562 cell line as a model. K562 cells were stably transfected with ERK1 or the dominant inhibitory mutant of ERK1 (ERK1-KR). Overexpression of ERK1-KR inhibited cell growth with an approximately fourfold increase in doubling time and induced apoptosis in K562 cells. Incubation with the MEK1 inhibitor UO126 inhibited cell growth and induced apoptosis in K562 cells in a dose-dependent manner as well. In the presence of exogenously added hemin, K562 cells differentiate into erythroblasts, as indicated by the production of large amounts of fetal hemoglobin. We examined the activation of MAP kinases during hemin-induced differentiation. The ERK1 and 2 activity increased within 2 h post hemin treatment and remained elevated for 24-48 h. During this time, fetal hemoglobin synthesis also increases from 0.8 to 10 pg/cell. There was no activation of JNK or p38 protein kinases. The hemin-induced accumulation of hemoglobin was inhibited in ERK1-KR overexpressing cells and was enhanced in the wild-type ERK1 transfectants. Our results suggest that ERK activation is involved in both growth and hemin-induced erythroid differentiation in the BCR-ABL-positive K562 cell line.
...
PMID:Role of ERK activation in growth and erythroid differentiation of K562 cells. 1126 76

This study examined the impact of the tyrosine kinase Lyn on erythropoietin-induced intracellular signaling in erythroid cells. In J2E erythroleukemic cells, Lyn coimmunoprecipitated with numerous proteins, including SHP-1, SHP-2, ras-GTPase-activating protein, signal transducers and activators of transcription (STAT) 5a, STAT5b, and mitogen-activated protein kinase; however, introduction of a dominant-negative Lyn (Y397F Lyn) inhibited the interaction of Lyn with all of these molecules except SHP-1. Cells containing the dominant-negative Lyn displayed altered intracellular phosphorylation patterns, including mitogen-actiated protein kinase, but not erythropoietin receptor, Janus-activated kinase (JAK) 2, or STAT5. As a consequence, erythropoietin-initiated differentiation and basal proliferation were severely impaired. Y397F Lyn reduced the protein levels of erythroid transcription factors erythroid Kruppel-like factor and GATA-1 up to 90%, which accounts for the inability of J2E cells expressing Y397F Lyn to synthesize hemoglobin. Although Lyn was shown to bind several sites on the cytoplasmic domain of the erythropoietin receptor, it was not activated when a receptor mutated at the JAK2 binding site was ectopically expressed in J2E cells indicating that JAK2 is the primary kinase in erythropoietin signaling and that Lyn is a secondary kinase. In normal erythroid progenitors, erythropoietin enhanced phosphorylation of Lyn; moreover, exogenous Lyn increased colony forming unit-erythroid, but not burst forming uniterythroid, colonies from normal progenitors, demonstrating a stage-specific effect of the kinase. Significantly, altering Lyn activity in J2E cells had a profound effect on the development of erythroleukemias in vivo: the mortality rate was markedly reduced and latent period extended when either wild-type Lyn or Y397F Lyn was introduced into these cells. Taken together, these data show that Lyn plays an important role in intracellular signaling in nontransformed and leukemic erythroid cells.
...
PMID:Maturation of erythroid cells and erythroleukemia development are affected by the kinase activity of Lyn. 1128 14

Stem cell factor (SCF) is a growth factor that promotes the survival, proliferation, and differentiation of hematopoietic cells. SCF and its receptor, Kit, are normally present in both cell surface and soluble forms. Both forms of Kit can bind SCF. However, the function of soluble Kit is unknown. In order to determine if soluble Kit can modulate SCF activity, we produced a fusion protein, Kit-Fc, comprised of the extracellular domain of murine Kit and the Fc portion of human IgG(1) and investigated its ability to bind 125I-SCF and to inhibit SCF-stimulated hematopoietic colony growth in vitro. Stable cell lines expressing Kit-Fc were generated and Kit-Fc was purified to greater than 95% purity. Scatchard analysis demonstrated that Kit-Fc binds iodinated SCF with high affinity (Kd 570 pM). Kit-Fc also bound to transmembrane SCF displayed on the surface of fibroblasts. The murine mast cell line IC2 was engineered to express murine Kit on the cell surface and was demonstrated to proliferate in the presence of SCF. Kit-Fc completely blocked SCF-stimulated proliferation of IC2-Kit cells, but not IL-3-stimulated growth of IC2-Kit cells, demonstrating the specificity of Kit-Fc. We investigated the ability of Kit-Fc to block SCF-stimulated murine hematopoietic colony growth. Kit-Fc blocked SCF-stimulated erythroid colony growth as effectively as a neutralizing anti-Kit monoclonal antibody, ACK2, but did not block erythropoietin-stimulated erythroid colony growth. Likewise, Kit-Fc blocked SCF-stimulated myeloid colony growth as effectively as ACK2 antibody, but did not block IL-3- or GM-CSF-stimulated myeloid colony growth. These results indicate that a form of soluble Kit binds SCF with high affinity, and can specifically block the ability of SCF to stimulate hematopoietic colony growth, suggesting that one function of soluble Kit may be to modulate SCF bioactivity.
...
PMID:Soluble Kit receptor blocks stem cell factor bioactivity in vitro. 1130 Nov 10

Erythropoietin (EPO) is a lineage-restricted growth factor that is required for erythroid proliferation and differentiation. EPO stimulates the phosphorylation and activation of p70 S6 kinase (p70 S6K), which is required for cell cycle progression. Here, the minimal cytoplasmic domains of the EPO receptor (EPO-R) required for p70 S6K activation were determined.Ba/F3 cells were stably transfected with wild-type (WT) EPO-R or EPO-R carboxyl-terminal deletion mutants, designated by the number of amino acids deleted from the cytoplasmic tail (-99, -131, -221). Transfected cells were growth factor deprived and then stimulated with EPO. p70 S6K, JAK2, IRS-2, and ERK1/2 phosphorylation/activation were examined. The ability of transfected 3-phosphoinositide-dependent protein kinase 1 (PDK1) to reconstitute p70 S6K phosphorylation in EPO-R mutants also was determined. Phosphorylation and activation of p70 S6K, JAK2, IRS-2, and ERK1/2 in Ba/F3 cells transfected with EPO-R-99 or EPO-R-99Y343F were similar to WT EPO-R. In contrast, EPO-dependent p70 S6K phosphorylation/activation, as well as IRS-2 and ERK1/2 phosphorylation, were minimal or absent in cells transfected with EPO-R-131 or EPO-R-221. JAK2 phosphorylation was reduced significantly in cells transfected with EPO-R-131 and abolished with EPO-R-221. To examine the role of PDK1, a kinase known to phosphorylate p70 S6K, Ba/F3 EPO-R-131 cells were transiently transfected with PDK1. WT constitutively active PDK1 restored p70 S6K phosphorylation in Ba/F3 EPO-R-131 cells but not in Ba/F3 EPO-R-221 cells. The results demonstrate that a minimal cytoplasmic subdomain of the EPO-R extending between -99 and -131 is required for p70 S6K phosphorylation and activation. The results also demonstrate that PDK1 is a critical component in this signaling pathway, which requires the presence of domains between -131 and -221 for its activation of p70 S6K.
...
PMID:A minimal cytoplasmic subdomain of the erythropoietin receptor mediates p70 S6 kinase phosphorylation. 1130 Nov 83

Erythropoietin (EPO) is the primary regulator of erythropoiesis, and promotes the survival, proliferation, and differentiation of erythroid progenitor cells. The EPO receptor belongs to the same family of receptors as growth hormone, granulocyte-colony stimulating factor, granulocyte macrophage-colony stimulating factor, and some interleukins. In the erythropoietic process, EPO induces homodimerization of the EPO receptor, which is located on the surface of erythroid progenitor cells. Dimerization activates the receptor-associated Janus kinase 2 via transphosphorylation. Specific tyrosines in the intracellular portion of the receptor are phosphorylated and serve as a docking site for intracellular proteins, including one of the signal transducers and activators of transcription (STAT5). This results in activating various cascades of signal transduction. STAT5 enters the nucleus on phosphorylation, inducing the transcription of erythroid genes. Phosphatases dephosphorylate Janus kinase 2 and downregulate the EPO receptor. Erythropoietin receptor activation seems to exert its effect by inhibiting apoptosis rather than by affecting the commitment of erythroid lineage, although the mechanism by which this occurs is as yet unclear. Anemia in cancer is associated with excessive production of cytokines that inhibit EPO synthesis, thereby interfering with the normal erythropoietic process, which leads to a reduction in red blood cells and the ability to oxygenate tissue.
...
PMID:The erythropoietin receptor. 1139 48

The granulocyte-derived hemoregulatory peptide pyroGlu-Glu-Asp-Cys-Lys = pEEDCK is known to keep hematopoietic cells quiescent. When oxidized to its dimeric form (pEEDCK)2, it activates growth of hematopoietic progenitors in association with stroma-derived cytokines. (pEEDCK)2 has a Cys-Cys motif which is also a typical feature of the macrophage inflammatory protein (MIP-1alpha). The present study was designed to analyze differences between the response of normal and leukemic progenitor cells to (pEEDCK)2 or MIP-1alpha. When long-term bone marrow cultures (LTBMCs) were incubated with (pEEDCK)2 or MIP-1alpha and/or cytokines, the stimulatory effect on colony-forming units-granulocyte/erythroid/macrophage/megakaryocyte of LTBMC from chronic myeloid leukemia (CML) patients was less than 50% compared to LTBMC from healthy humans. No difference in oncogene expression could be observed in LTBMC from CML patients regarding reduction of Philadelphia chromosome-associated transcription of the BCR-ABL gene. With respect to the expression of growth and differentiation-associated genes (Galpha16, 5-lipoxygenase, phospholipaseA2, c-kit, and CD34), which were analyzed from LTBMC by semiquantitative reverse transcriptase-polymerase chain reaction, the same transcription rate was observed in CML patients and healthy donors. However, two isoforms of a key enzyme of oxidative metabolism, carnitine palmitoyltransferase (CPT1A and CPT1B), showed 50-fold higher expression rates in LTBMC cells of healthy donors compared to CML patients. It is known that a decrease in oxidative metabolism is associated with an increase in redox equivalents in malignancy. This might result in a reduction of disulphide bonds in (pEEDCK)2 or MIP-1alpha, thus inducing a downregulation of these factors in bone marrow from CML patients.
...
PMID:Effect of the hemoregulatory peptide (pEEDCK)2 (pyroGlu-Glu-Asp-Cys-Lys)2 and MIP-1alpha is reduced in bone marrow cultures from patients with chronic myeloid leukemia (CML). 1146 52

Cellular trafficking of growth factor receptors, including cross-talk among receptors at the cell surface, may be important for signal transduction in normal hematopoietic cells. To test this idea, the signaling domain of Mpl (the thrombopoietin receptor) was targeted to the plasma membrane, or to the cytoplasm of murine marrow cells, and the ability of the cells to proliferate and differentiate in response to Mpl dimerized at the plasma membrane or free in the cytoplasm was assessed. Constructs encoding the signaling domain of Mpl linked to an FK506 binding protein domain (to permit dimerization by the membrane-permeable ligand AP20187) with or without a myristylation sequence (to target the receptor to the plasma membrane) and a hemagglutinin epitope tag were generated and introduced into murine marrow cells using a murine stem cell virus (MSCV)-based retroviral vector. Both populations of transduced marrow cells proliferated in Iscoves modified Dulbecco medium-10% FCS-100 nM AP20187 without exogenous growth factors for more than 100 days and achieved greater than a 10(7)-fold expansion of cells by day 50 (n = 4 transductions). Growth was dimerizer dependent, and myeloid, erythroid, and megakaryocytic progenitors were generated. Activation of Mpl either at the plasma membrane or in the cytoplasm allowed for the terminal maturation of transduced progenitor cells. Introduction of membrane-targeted or cytoplasmic Mpl into fetal liver cells from homozygous JAK2 knock-out mice or wild-type littermates demonstrated that both forms of Mpl require JAK2 for signaling. These data show that the activation of Mpl independent of its normal plasma membrane location can support production of the full range of normal hematopoietic progenitor cells in vitro.
...
PMID:Membrane localization is not required for Mpl function in normal hematopoietic cells. 1156 93

The receptor-associated protein tyrosine kinase janus-kinase 2 (JAK2) is essential for normal red cell development and for erythropoietin receptor (EpoR) signaling. JAK2(-/-) embryos are severely deficient in erythropoiesis and die at an early stage of development from fetal anemia. The binding of erythropoietin (Epo) to the EpoR triggers the activation of JAK2, the phosphorylation of the EpoR, and the initiation of the EpoR signaling cascade. In addition to Epo binding to its receptor, signaling pathways downstream of the EpoR can also be stimulated by the BCR-ABL oncoprotein. This study explored whether JAK2 is required for BCR-ABL-mediated stimulation of erythropoiesis. Here, it is shown that JAK2 is constitutively tyrosine phosphorylated in cultured and primary erythroid cells expressing BCR-ABL. However, BCR-ABL effectively supports normal erythroid proliferation, differentiation, and maturation in JAK2-deficient fetal liver cells. Using mutants of BCR-ABL, this study shows that certain signaling pathways activated by BCR-ABL segments distinct from its tyrosine kinase domain are essential for rescue of erythropoiesis in JAK2(-/-) progenitors. The consequences of these multiple signaling pathways for normal erythroid development are discussed.
...
PMID:Erythropoiesis in the absence of janus-kinase 2: BCR-ABL induces red cell formation in JAK2(-/-) hematopoietic progenitors. 1169 76

Stromal-derived factor 1 (SDF-1) is a -CXC- chemokine that plays a critical role in embryonic and adult hematopoiesis, and its specific receptor, CXCR4, has been implicated in stem cell homing. In this study, it is shown that the addition of SDF-1 to long-term cultures (LTCs) of normal human marrow can selectively, reversibly, and specifically block the S-phase entry of primitive quiescent erythroid and granulopoietic colony-forming cells (CFCs) present in the adherent layer. Conversely, addition of anti-SDF-1 antibody or SDF-1(G2), a specific CXCR4 antagonist, to preactivated human LTCs prevented both types of primitive CFCs from re-entering a quiescent state, demonstrating that endogenous SDF-1 contributes to the control of primitive CFC proliferation in the LTC system. Interestingly, SDF-1 failed to arrest the proliferation of primitive chronic myeloid leukemia CFCs in the adherent layer of LTCs containing normal marrow stromal cells. In vivo, injection of SDF-1 arrested the cycling of normal human LTC-initiating cells as well as primitive CFCs in the marrow of nonobese diabetic/severe combined immunodeficient mice engrafted with human cord blood cells. Conversely, injection of the antagonist, SDF-1(G2), reactivated the cycling of quiescent primitive human CFCs present in the marrow of mice engrafted with human marrow cells. These studies are the first to demonstrate a potential physiological role of SDF-1 in regulating the cell-cycle status of primitive hematopoietic cells and suggest that the deregulated cycling activity of primitive chronic myeloid leukemia (CML) cells is due to the BCR-ABL-mediated disruption of a pathway shared by multiple chemokine receptors.
...
PMID:Stromal-derived factor 1 inhibits the cycling of very primitive human hematopoietic cells in vitro and in NOD/SCID mice. 1180 78

The mammalian forkhead transcription factors, FOXO3a (FKHRL1), FOXO1a (FKHR) and FOXO4 (AFX) are negatively regulated by PKB/Akt kinase. In the present study we examined the engagement of forkhead family of transcription factors in erythropoietin (Epo)- and stem cell factor (SCF)-mediated signal transduction. Our data show that all three forkhead family members, FOXO3a, FOXO1a and FOXO4 are phosphorylated in human primary erythroid progenitors. Experiments performed to determine various upstream signaling pathways contributing to phosphorylation of forkhead family members show that only PI-3-kinase pathway is required for inactivation of FOXO3a. Our data also demonstrate that during Epo deprivation FOXO3a interacts with the transcriptional coactivator p300 and such interaction is disrupted by stimulation of cells with Epo. To determine the domains in FOXO3a, mediating its interaction with p300, we performed GST pull-down assays and found that the N-terminus region containing the first 52 amino acids was sufficient for binding p300. Finally, our data demonstrate that FOXO3a and FOXO1a are acetylated during growth factor deprivation and such acetylation is reversed by stimulation with Epo. Thus mammalian forkhead transcription factors are involved in Epo and SCF signaling in primary erythroid progenitors and may play a role in the induction of apoptotic and mitogenic signals.
...
PMID:Phosphorylation of forkhead transcription factors by erythropoietin and stem cell factor prevents acetylation and their interaction with coactivator p300 in erythroid progenitor cells. 1189 84


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---