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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bcr-Abl tyrosine kinase inhibitor induces apoptosis and erythroid differentiation of K562 cells. During this erythroid differentiation, c-Myc and cyclin D1 transcripts are transiently downregulated. Accordingly, we studied the effect of cyclin D1 overexpression on erythroid differentiation. After treatment with 250 nM STI571, 90% of K562 and 25% of K562/D1 cells underwent erythroid differentiation. The basal expression of glycophorin A in K562/D1 cells was markedly diminished compared with that by parental cells. STI571 treatment failed to induce glycophorin A expression in K562/D1 cells. During STI571 treatment, ERK activity was downregulated in parental cells, while it was constantly activated in K562/D1 cells. These results suggest that ectopic expression of cyclin D1 causes the resistance of K562 cells to erythroid differentiation by modulating ERK regulation.
...
PMID:Ectopic cyclin D1 expression blocks STI571-induced erythroid differentiation of K562 cells. 1512 Sep 40

Oncogenic mutations in ras genes frequently occur in patients with myeloid disorders, and in these patients erythropoiesis is often affected. Previously, we showed that expression of oncogenic H-ras in purified mouse primary fetal liver erythroid progenitors blocks terminal erythroid differentiation and supports erythropoietin (Epo)-independent proliferation. As a first step in understanding the underlying molecular mechanisms we examined the signaling pathways downstream of Ras in primary erythroid cells. We found that 3 major pathways are abnormally activated by oncogenic H-ras: Raf/ERK (extracellular signal-regulated kinase), phosphatidyl inositol 3 (PI3)-kinase/Akt, and RalGEF/RalA. However, only constitutive activation of the MEK (MAPK [mitogen-activated protein kinase]/ERK kinase)/ERK pathway alone could recapitulate all of the effects of oncogenic H-ras expression in blocking erythroid differentiation and inducing Epo-independent proliferation. Although expression of a constitutively active Akt kinase (ca.Akt) in erythroid progenitors does not significantly affect erythroid differentiation in the presence of Epo, coexpression of ca.Akt together with a constitutively active MEK causes prolonged Epo-independent proliferation of erythroid progenitors in addition to a block in differentiation. Moreover, the effects of oncogenic H-ras expression on primary erythroid cells are blocked by the addition of U0126, a specific inhibitor of MEK1 and MEK2, allowing normal terminal erythroid proliferation and differentiation. Our data suggest that the interruption of constitutive MEK/ERK signaling is a potential therapeutic strategy to correct impaired erythroid differentiation in patients with myeloid disorders.
...
PMID:Constitutive activation of the MEK/ERK pathway mediates all effects of oncogenic H-ras expression in primary erythroid progenitors. 1516 36

Gene-targeting experiments in transgenic mice have revealed an essential role for GATA-1 in the normal differentiation and development of erythroid cells. GATA-1 is phosphorylated in vivo on seven of its serine residues; the regulation and function of GATA-1 phosphorylation, however, is not understood. Here we demonstrate a role for MAP kinase (MAPK) signalling in the control of GATA-1 phosphorylation. We show that EGF-induced MAPK signalling results in the phosphorylation of ectopically expressed GATA-1 in COS cells. This phosphorylation can be positively or negatively regulated by genetic manipulation of the MAPK pathway through expression of constitutively activated, or dominant-negative, mutants of MAPK kinase (MAPKK), an upstream regulator of MAPK activity. In vitro phosphorylation experiments using purified MAPK and either recombinant GATA-1 or synthetic GATA-1 peptides suggest that GATA-1 is a MAPK substrate with MAPK phosphorylation occurring primarily on Ser26 and Ser178. We also show that GATA-1 is phosphorylated in factor-dependent haemopoietic progenitor cells in response to cytokine-induced signalling. Through the further use of a dominant-negative MAPKK mutant as well as chemical inhibitors of specific MAPKs, we identify ERK as an in vivo GATA-1 kinase. Finally, we demonstrate that mutation of serines 26 and 178 compromises the ability of GATA-1 to interact with the LIM-only protein LMO2 when both proteins are expressed in COS cells. These data implicate receptor-mediated signalling through the MAPK pathway as a control point in the regulation of transcription factor GATA-1.
...
PMID:Involvement of mitogen-activated protein kinase in the cytokine-regulated phosphorylation of transcription factor GATA-1. 1516 14

K562 cells can be induced to differentiate along the erythroid lineage by a variety of chemical compounds, including hemin, butyrate, cisplatin and ara-C. Differential signaling through MAP kinases has been suggested to be involved in this differentiation process. We have investigated the involvement of ERK activation/inhibition in hemin-, butyrate-, cisplatin- and ara-C-induced erythroid differentiation using the K562 cell line. ERK activity decreased for 2-4h after administration of either inducing agent. ERK was then activated by hemin and cisplatin, while ERK phosphorylation remained decreased during incubation with butyrate and ara-C. There was no activation of JNK or p38. The MEK-1 inhibitors UO126 or PD98059 induced erythroid differentiation in K562 cells and acted additively with butyrate. Inhibition of MEK-1 reduced the hemoglobin accumulation by hemin and cisplatin; erythroid differentiation by ara-C was unchanged. The results suggest that inhibition of signaling through ERK in K562 cells may be needed to enter the erythroid differentiation process, while after initiation both activation and inhibition of signaling through ERK enhance erythroid differentiation, which, however, is dependent on the inducing compound.
...
PMID:ERK signaling pathway is differentially involved in erythroid differentiation of K562 cells depending on time and the inducing agent. 1519 84

The aim of this study was to clarify the mechanisms that regulate hematopoietic cell expansion in vitro by identifying defined culture conditions. We report the results of experiments with CD34(+) cells from cord blood (CB, n = 13), bone marrow (BM, n = 4), and mobilized peripheral blood stem cells (PBSC, n = 5) using two combinations of cytokines: (A) granulocyte colony-stimulating factor (G-CSF), interleukin-3 (IL-3), interleukin-6 (IL-6), stem cell factor (SCF), erythropoietin (EPO), insulin-like growth factor-1 (IGF-1), basic fibroblast growth factor (FGF-b) and (B) combination A plus FLT3 ligand (FL) and megakaryocyte growth and development factor (PEG rhMGDF). Cultures of immunoselected CD34(+) cells were performed in serum-free liquid medium without serum substitutes. The area under the curve (AUC) obtained by plotting the logarithm of the total number of viable cells, CD34(+) cells, and CFC per well, toward the week of culture was used as an index of cell expansion. With CB, a significant difference was obtained between the two combinations of cytokines with regard to the total number of viable cells, GM-CFC, and CD34(+) cells. The difference between the two combinations of cytokines obtained with BM was significant with respect to the total number of viable cells and CD34(+) cells but not for the erythroid and myeloid progenitors. When CD34(+) cells from peripheral blood stem cells (PBSC) were cultured in presence of the two combinations of cytokines, the difference in terms of AUC was not statistically significant. Our data indicate additional effects in terms of proliferation and expansion of hematopoietic cells in serum-free conditions when FL and polyethylene glycol (PEG) rhMGDF are included in culture and suggest a differential activity of these cytokines on cells from different hematopoietic sources.
...
PMID:Effect of addition of FLT-3 ligand and megakaryocyte growth and development factor on hemopoietic cells in serum-free conditions. 1534 30

K562 cells can be used as a model of erythroid differentiation on being induced by hemin. We found that the level of annexin1 gene expression was notably increased during this indicated process. To test the hypothesis that annexin1 can regulate erythropoiesis, K562 cell clones in which annexin1 was stably increased and was knocked down by RNAi were established, respectively. With analysis by hemoglobin quantification, benzidine staining, and marker gene expression profile determination, we confirmed that hemin-induced erythroid differentiation of K562 cells was modestly stimulated by overexpression of annexin1 while it was significantly blocked by knock down of annexin1. Further studies revealed that the mechanisms of annexin1 regulation of the erythroid differentiation was partially related to the increased ERK phosphorylation and expression of p21(cip/waf), since specific inhibitor of MEK blocked the function of annexin1 in erythroid differentiation. We concluded that annexin1 exerted its erythropoiesis regulating effect by ERK pathway.
...
PMID:Annexin1 regulates the erythroid differentiation through ERK signaling pathway. 1588 23

The mammalian Rh (Rhesus) protein family belongs to the Amt/Mep (ammonia transporter/methylammonium permease)/Rh superfamily of ammonium transporters. Whereas RhCE, RhD and RhAG are erythroid specific, RhBG and RhCG are expressed in key organs associated with ammonium transport and metabolism. We have investigated the ammonium transport function of human RhBG and RhCG by comparing intracellular pH variation in wild-type and transfected HEK-293 (human embryonic kidney) cells and MDCK (Madin-Darby canine kidney) cells in the presence of ammonium (NH4+/NH3) gradients. Stopped-flow spectrofluorimetry analysis, using BCECF [2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein] as a pH-sensitive probe, revealed that all cells submitted to inwardly or outwardly directed ammonium gradients exhibited rapid alkalinization or acidification phases respectively, which account for ammonium movements in transfected and native cells. However, as compared with wild-type cells known to have high NH3 lipid permeability, RhBG- and RhCG-expressing cells exhibited ammonium transport characterized by: (i) a five to six times greater kinetic rate-constant; (ii) a weak temperature-dependence; and (iii) reversible inhibition by mercuric chloride (IC50: 52 microM). Similarly, when subjected to a methylammonium gradient, RhBG- and RhCG-expressing cells exhibited kinetic rate constants greater than those of native cells. However, these constants were five times higher for RhBG as compared with RhCG, suggesting a difference in substrate accessibility. These results, indicating that RhBG and RhCG facilitate rapid and low-energy-dependent bi-directional ammonium movement across the plasma membrane, favour the hypothesis that these Rh glycoproteins, together with their erythroid homologue RhAG [Ripoche, Bertrand, Gane, Birkenmeier, Colin and Cartron (2005) Proc. Natl. Acad. Sci. U.S.A. 101, 17222-17227] constitute a family of NH3 channels in mammalian cells.
...
PMID:Human Rhesus B and Rhesus C glycoproteins: properties of facilitated ammonium transport in recombinant kidney cells. 1592 23

Red blood cell development is primarily controlled by erythropoietin (EPO). Several studies have revealed the importance of EPO-R Y343 and Y479 for erythroid cell growth, differentiation, and survival. In order to isolate critical signaling proteins that bind to EPO-R, we initiated a Cloning of Ligand Target (COLT) screen using a murine embryonic day 16 phage library and a biotinylated EPO-R Y343 phosphopeptide. One of the clones isolated encodes Phospholipase C (PLC)gamma1. PLCgamma1 is rapidly tyrosine phosphorylated upon EPO stimulation and associates with EPO-R in an SH2-domain-dependent manner. Although PLCgamma1 bound EPO-R Y343, Y401, Y429, Y431, and Y479 in the COLT screen, PLCgamma1 required Y479 for association with EPO-R in Ba/F3-EPO-R cells. Studies have identified EPO-R Y479 as important for ERK activation. Since PI3-kinase binds EPO-R Y479, one group has suggested that ERK activation downstream of PI3-kinase accounts for the importance of this residue in EPO signaling. However, we show that inhibition of PI3-kinase does not abolish ERK activation. Furthermore, we demonstrate interaction of PLCgamma1 with Grb2 and SOS2. Hence, we have identified a novel adapter function for PLCgamma1 in EPO signaling in which recruitment of PLCgamma1 to EPO-R may lead to activation of the ERK pathway.
...
PMID:Erythropoietin receptor Y479 couples to ERK1/2 activation via recruitment of phospholipase Cgamma. 1595 1

Release of vascular endothelial growth factor (VEGF) and other candidate angiogenic factors such as basic fibroblast growth factor and transforming growth factor beta, may play a role in sustaining neoplastic cell proliferation and tumor growth. We evaluated VEGF expression and synthesis in the two erythromegakaryocytic cell lines B1647, HEL and one megakaryocytic cell line MO7 expressing erythroid markers. In this study RT-PCR was performed to evaluate VEGF expression and that of its receptor KDR; VEGF production was assayed by Elisa test and western blot analysis; sensitivity to VEGF was tested by thymidine incorporation. VEGF and its receptor KDR were expressed in B1647 and HEL, both as mRNAs and as proteins, while only KDR transcript was found in MO7 cells. Only B1647 and HEL cells showed a strong spontaneous proliferating activity. In fact, measurable amounts of VEGF were present in the unstimulated cell medium, thus suggesting an autocrine production of VEGF by B1647 and HEL cells, but not by MO7, which was inhibited in mRNA-silencing conditions. This production could not be further boosted by other growth factors, whereas it was inhibited by TGF-beta1. Finally, analysis of Shc signal transduction proteins following stimulation with VEGF indicated that only p46 was tyrosine phosphorylated. These data indicate that leukemic cells may be capable of autocrine production of VEGF which, in turn, maintains cell proliferation, possibly mediated by Shc p46 phosphorylation.
...
PMID:Constitutive and stimulated production of VEGF by human megakaryoblastic cell lines: effect on proliferation and signaling pathway. 1616 27

Alternative splicing of signaling proteins can contribute to the complexity of signaling networks. We find that expression of mouse RON, but not human RON, results in constitutive receptor autophosphorylation, ligand-independent activation of the mitogen-activated protein kinase pathway, and association of the receptor with c-Src. Using chimeric receptors, we mapped the region for this difference in signaling capacity of mouse and human RON to the juxtamembrane domain. Expression of these receptors in primary erythroid progenitor cells also demonstrated a functional difference in the ability of mouse and human RON to support erythropoietin-independent colony formation that mapped to the juxtamembrane domain. Splicing of the mouse RON receptor tyrosine kinase transcript results in the constitutive deletion of an exon used by all other known RON orthologs that encodes part of the juxtamembrane domain of the receptor. Mutational analysis indicated that the two tyrosines present in this region in human RON, one of which has been previously shown to be a c-Cbl binding site, are not responsible for this difference. However, deletion of this region in the context of human RON enhanced receptor phosphorylation, activation of mitogen-activated protein kinase, and association of c-Src at levels comparable with those observed with mouse RON. These data provide direct evidence that the divergence of exon usage among different species can generate a protein with novel activity and subsequently add to the complexity of cellular signaling regulation.
...
PMID:Altered exon usage in the juxtamembrane domain of mouse and human RON regulates receptor activity and signaling specificity. 1616 96


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

---