scholarly journals Kinetic and biochemical correlation between sustained p44ERK1 (44 kDa extracellular signal-regulated kinase 1) activation and lysophosphatidic acid-stimulated DNA synthesis in Rat-1 cells

1996 ◽  
Vol 320 (1) ◽  
pp. 237-245 ◽  
Author(s):  
Simon J. COOKOnyx ◽  
Frank McCORMICK
Keyword(s):  
Dna Synthesis ◽  
Pertussis Toxin ◽  
Lysophosphatidic Acid ◽  
Peak Response ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Herbimycin A ◽  
Extracellular Signal ◽  
Sustained Activation

Rat-1 fibroblasts were used to study the role of the sustained activation of extracellular signal-regulated kinase 1 (ERK1) in lysophosphatidic acid (LPA)-stimulated mitogenic signalling. Mitogenic doses of LPA, like serum, stimulated biphasic, sustained, ERK activation that persisted towards the G1/S boundary. The EC50 for LPA-stimulated ERK activation after 10 min, the time of peak response, was 2 orders of magnitude to the left of that for the sustained response after 3 h or that for DNA synthesis after 22 h, with the result that non-mitogenic doses stimulated a maximal peak response but no second phase. To complement these studies, we examined the role of different signal pathways in regulating the sustained and acute phases of ERK activation using defined biochemical inhibitors and mimetics. Activation of protein kinase C and Ca2+ fluxes played a minor and transient role in regulation of ERK1 activity by LPA in Rat-1 cells. Sustained ERK1 activation stimulated by LPA was completely inhibited by pertussis toxin, whereas the early peak response was only partly affected; this is correlated with the specific inhibition of LPA-stimulated DNA synthesis by pertussis toxin. The selective tyrosine kinase inhibitor herbimycin A completely inhibited sustained ERK1 activation by LPA but, again, the early phase of the response was only partially inhibited. In addition, low doses of staurosporine inhibited ERK1 activation by LPA. The effects of herbimycin A and staurosporine were selective for the response to LPA but did not affect that to epidermal growth factor. The results suggest a strong correlation between sustained ERK1 activation and DNA synthesis in LPA-stimulated Rat-1 cells. Furthermore, the two discrete phases of ERK activation by LPA are regulated by a combination of at least two different signalling pathways; the sustained activation of ERK1 in Rat-1 cells proceeds via a Gi- or Go-mediated pathway which may also involve a tyrosine kinase.

Constitutive Activation of Extracellular Signal-Regulated Kinase in Human Acute Leukemias: Combined Role of Activation of MEK, Hyperexpression of Extracellular Signal-Regulated Kinase, and Downregulation of a Phosphatase, PAC1

Blood ◽  
1999 ◽  
Vol 93 (11) ◽  
pp. 3893-3899 ◽  
Author(s):  
Seong-Cheol Kim ◽  
Jee-Sook Hahn ◽  
Yoo-Hong Min ◽  
Nae-Choon Yoo ◽  
Yun-Woong Ko ◽  
...  
Keyword(s):  
Acute Leukemia ◽  
Immunoblot Analysis ◽  
Kinase Assay ◽  
Hematopoietic Tissue ◽  
Acute Leukemias ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Constitutive Activation ◽  
Extracellular Signal

Abstract Extracellular signal-regulated kinase (ERK) is an important intermediate in signal transduction pathways that are initiated by many types of cell surface receptors. It is thought to play a pivotal role in integrating and transmitting transmembrane signals required for growth and differentiation. Constitutive activation of ERK in fibroblasts elicits oncogenic transformation, and recently, constitutive activation of ERK has been observed in some human malignancies, including acute leukemia. However, mechanisms underlying constitutive activation of ERK have not been well characterized. In this study, we examined the activation of ERK in 79 human acute leukemia samples and attempted to find factors contributing to constitutive ERK activation. First, we showed that ERK and MEK were constitutively activated in acute leukemias by in vitro kinase assay and immunoblot analysis. However, in only one half of the studied samples, the pattern of ERK activation was similar to that of MEK activation. Next, by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblot analysis, we showed hyperexpression of ERK in a majority of acute leukemias. In 17 of 26 cases (65.4%) analyzed by immunoblot, the pattern of ERK expression was similar to that of ERK activation. The fact of constitutive activation of ERK in acute leukemias suggested to us the possibility of an abnormal downregulation mechanism of ERK. Therefore, we examined PAC1, a specific ERK phosphatase predominantly expressed in hematopoietic tissue and known to be upregulated at the transcription level in response to ERK activation. Interestingly, in our study, PAC1 gene expression in acute leukemias showing constitutive ERK activation was significantly lower than that in unstimulated, normal bone marrow (BM) samples showing minimal or no ERK activation (P = .002). Also, a significant correlation was observed between PAC1 downregulation and phosphorylation of ERK in acute leukemias (P= .002). Finally, by further analysis of 26 cases, we showed that a complementary role of MEK activation, ERK hyperexpression, and PAC1 downregulation could contribute to determining the constitutive activation of ERK in acute leukemia. Our results suggest that ERK is constitutively activated in a majority of acute leukemias, and in addition to the activation of MEK, the hyperexpression of ERK and downregulation of PAC1 also contribute to constitutive ERK activation in acute leukemias.

scholarly journals The Tyrosine Phosphatase SHP-2 Is Required for Sustained Activation of Extracellular Signal-Regulated Kinase and Epithelial Morphogenesis Downstream from the Met Receptor Tyrosine Kinase

2000 ◽  
Vol 20 (22) ◽  
pp. 8513-8525 ◽  
Author(s):  
Christiane R. Maroun ◽  
Monica A. Naujokas ◽  
Marina Holgado-Madruga ◽  
Albert J. Wong ◽  
Morag Park
Keyword(s):  
Growth Factor ◽  
Tyrosine Phosphatase ◽  
Epithelial Morphogenesis ◽  
Met Receptor ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Transient Activation ◽  
Extracellular Signal ◽  
Positive Modulator ◽  
Sustained Activation

ABSTRACT Epithelial morphogenesis is critical during development and wound healing, and alterations in this program contribute to neoplasia. Met, the hepatocyte growth factor (HGF) receptor, promotes a morphogenic program in epithelial cell lines in matrix cultures. Previous studies have identified Gab1, the major phosphorylated protein following Met activation, as important for the morphogenic response. Gab1 is a docking protein that couples the Met receptor with multiple signaling proteins, including phosphatidylinositol-3 kinase, phospholipase Cγ, the adapter protein Crk, and the tyrosine specific phosphatase SHP-2. HGF induces sustained phosphorylation of Gab1 and sustained activation of extracellular signal-regulated kinase (Erk) in epithelial Madin-Darby canine kidney cells. In contrast, epidermal growth factor fails to promote a morphogenic program and induces transient Gab1 phosphorylation and Erk activation. To elucidate the Gab1-dependent signals required for epithelial morphogenesis, we undertook a structure-function approach and demonstrate that association of Gab1 with the tyrosine phosphatase SHP-2 is required for sustained Erk activation and for epithelial morphogenesis downstream from the Met receptor. Epithelial cells expressing a Gab1 mutant protein unable to recruit SHP-2 elicit a transient activation of Erk in response to HGF. Moreover, SHP-2 catalytic activity is required, since the expression of a catalytically inactive SHP-2 mutant, C/S, abrogates sustained activation of Erk and epithelial morphogenesis by the Met receptor. These data identify SHP-2 as a positive modulator of Erk activity and epithelial morphogenesis downstream from the Met receptor.

ET-1 stimulates ERK signaling pathway through sequential activation of PKC and Src in rat myometrial cells

2002 ◽  
Vol 283 (1) ◽  
pp. C251-C260 ◽  
Author(s):  
Philippe Robin ◽  
Isaline Boulven ◽  
Christine Desmyter ◽  
Simone Harbon ◽  
Denis Leiber
Keyword(s):  
Phorbol Ester ◽  
Pertussis Toxin ◽  
Receptor Subtype ◽  
Dependent Manner ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Myometrial Cells ◽  
Kinase C ◽  
Extracellular Signal ◽  
Sequential Activation

In this study, we analyzed in rat myometrial cells the signaling pathways involved in the endothelin (ET)-1-induced extracellular signal-regulated kinase (ERK) activation required for the induction of DNA synthesis. We found that inhibition of protein kinase C (PKC) by Ro-31–8220 abolished ERK activation. Inhibition of phospholipase C (PLC) by U-73122 or of phosphoinositide (PI) 3-kinase by wortmannin partially reduced ERK activation. A similar partial inhibition was observed after treatment with pertussis toxin or PKC downregulation by phorbol ester treatment. The effect of wortmannin was additive with that produced by PKC downregulation but not with that due to pertussis toxin. These results suggest that both diacylglycerol-sensitive PKC, activated by PLC products, and diacylglycerol-insensitive PKC, possibly activated by a Gi-PI 3-kinase-dependent process, are involved in ET-1-induced ERK activation. These two pathways were found to be activated mainly through the ETA receptor subtype. ET-1 and phorbol ester stimulated Src activity in a PKC-dependent manner, both responses being abolished in the presence of Ro-31–8220. Inhibition of Src kinases by PP1 abrogated phorbol ester- and ET-1-induced ERK activation. Finally, ET-1 activated Ras in a PP1- and Ro-31–8220-sensitive manner. Altogether, our results indicate that ET-1 induces ERK activation in rat myometrial cells through the sequential stimulation of PKC, Src, and Ras.

MEK1 is required for PDGF-induced ERK activation and DNA synthesis in tracheal myocytes

1997 ◽  
Vol 272 (3) ◽  
pp. L558-L565 ◽  
Author(s):  
A. Y. Karpova ◽  
M. K. Abe ◽  
J. Li ◽  
P. T. Liu ◽  
J. M. Rhee ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Active Form ◽  
Dominant Negative ◽  
Airway Smooth Muscle Cells ◽  
Dependent Manner ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Erk2 Activation ◽  
Constitutively Active

We tested whether activation of mitogen-activated protein kinase/ extracellular signal-regulated kinase kinase-1 (MEK1) is required and sufficient for extracellular signal-regulated kinase (ERK) activation in airway smooth muscle cells. First, we transiently cotransfected bovine tracheal myocytes with an epitope-tagged ERK2 and a dominant-negative or a constitutively active form of the gene encoding MEK1 and assessed ERK2 activation by in vitro phosphorylation assay. Expression of the dominant-negative MEK1 inhibited platelet-derived growth factor (PDGF)-induced ERK2 activation, whereas expression of the constitutively active MEK1 induced ERK2 activation, suggesting that MEK1 is required and sufficient for ERK activation in these cells. Next, we assessed the effect of PD-98059, a synthetic MEK inhibitor, on PDGF-induced MEK1 and ERK activation. PD-98059 (10 microM) inhibited MEK1 and ERK activation, confirming that MEK1 is required for ERK activation in bovine tracheal myocytes. PD-98059 had no effect on Src or Raf-1 activity, evidence that PD-98059 is a specific inhibitor of MEK in this system. Finally, PD-98059 reduced PDGF-induced [(3)H]thymidine incorporation in a concentration-dependent manner, suggesting that catalytic activation of MEK1 and ERKs is required for DNA synthesis. We conclude that MEK1 is required for PDGF-induced ERK activation in bovine tracheal myocytes and that MEK1 and ERKs are required for PDGF-induced DNA synthesis in these cells.

Constitutive Activation of Extracellular Signal-Regulated Kinase in Human Acute Leukemias: Combined Role of Activation of MEK, Hyperexpression of Extracellular Signal-Regulated Kinase, and Downregulation of a Phosphatase, PAC1

Blood ◽  
1999 ◽  
Vol 93 (11) ◽  
pp. 3893-3899 ◽  
Author(s):  
Seong-Cheol Kim ◽  
Jee-Sook Hahn ◽  
Yoo-Hong Min ◽  
Nae-Choon Yoo ◽  
Yun-Woong Ko ◽  
...  
Keyword(s):  
Acute Leukemia ◽  
Immunoblot Analysis ◽  
Kinase Assay ◽  
Hematopoietic Tissue ◽  
Acute Leukemias ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Constitutive Activation ◽  
Extracellular Signal

Extracellular signal-regulated kinase (ERK) is an important intermediate in signal transduction pathways that are initiated by many types of cell surface receptors. It is thought to play a pivotal role in integrating and transmitting transmembrane signals required for growth and differentiation. Constitutive activation of ERK in fibroblasts elicits oncogenic transformation, and recently, constitutive activation of ERK has been observed in some human malignancies, including acute leukemia. However, mechanisms underlying constitutive activation of ERK have not been well characterized. In this study, we examined the activation of ERK in 79 human acute leukemia samples and attempted to find factors contributing to constitutive ERK activation. First, we showed that ERK and MEK were constitutively activated in acute leukemias by in vitro kinase assay and immunoblot analysis. However, in only one half of the studied samples, the pattern of ERK activation was similar to that of MEK activation. Next, by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblot analysis, we showed hyperexpression of ERK in a majority of acute leukemias. In 17 of 26 cases (65.4%) analyzed by immunoblot, the pattern of ERK expression was similar to that of ERK activation. The fact of constitutive activation of ERK in acute leukemias suggested to us the possibility of an abnormal downregulation mechanism of ERK. Therefore, we examined PAC1, a specific ERK phosphatase predominantly expressed in hematopoietic tissue and known to be upregulated at the transcription level in response to ERK activation. Interestingly, in our study, PAC1 gene expression in acute leukemias showing constitutive ERK activation was significantly lower than that in unstimulated, normal bone marrow (BM) samples showing minimal or no ERK activation (P = .002). Also, a significant correlation was observed between PAC1 downregulation and phosphorylation of ERK in acute leukemias (P= .002). Finally, by further analysis of 26 cases, we showed that a complementary role of MEK activation, ERK hyperexpression, and PAC1 downregulation could contribute to determining the constitutive activation of ERK in acute leukemia. Our results suggest that ERK is constitutively activated in a majority of acute leukemias, and in addition to the activation of MEK, the hyperexpression of ERK and downregulation of PAC1 also contribute to constitutive ERK activation in acute leukemias.

scholarly journals Gonadotropin-Releasing Hormone Pulse Frequency-Dependent Activation of Extracellular Signal-Regulated Kinase Pathways in Perifused LβT2 Cells

Endocrinology ◽  
2005 ◽  
Vol 146 (12) ◽  
pp. 5503-5513 ◽  
Author(s):  
Haruhiko Kanasaki ◽  
Gregoy Y. Bedecarrats ◽  
Kyung-Yoon Kam ◽  
Shuyun Xu ◽  
Ursula B. Kaiser
Keyword(s):  
Pulse Frequency ◽  
Frequency Dependent ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Erk Phosphorylation ◽  
Extracellular Signal ◽  
Gnrh Release ◽  
The Difference ◽  
Stimulation Of

The pattern of GnRH release is associated with differential synthesis and release of LH and FSH. Using a perifusion system, we previously reported that stimulation of the LβT2 cell line with varying GnRH pulse frequencies resulted in differential stimulation of LHβ and FSHβ gene transcription, analogous to previous observations in primary gonadotropes. In the present study, we investigated the patterns of MAPK activation by GnRH and the role of MAPK in mediating the frequency-dependent effects. In static culture, ERK activation in LβT2 cells stimulated with continuous GnRH (10 nm) was maximal by 10 min and persisted for up to 6 h, with a return to basal levels by 20 h. In contrast, stimulation with continuous GnRH (10 nm) in perifused cells resulted in a more sustained activation of ERK. To investigate the effects of GnRH pulse frequency on ERK activation, perifused LβT2 cells were stimulated with pulsatile GnRH at a frequency of one pulse every 30 min or one pulse every 2 h for 20 h (10 nm, 5 min/pulse). After the final GnRH pulse, cells were lysed at frequent intervals and levels of ERK phosphorylation were measured. Under high-frequency conditions, ERK activation was maximal 10 min after the GnRH pulse and returned to baseline levels by 20 min. In contrast, under lower GnRH pulse frequency conditions, ERK activation occurred more rapidly and activation was more sustained, with a slower rate of ERK dephosphorylation. These changes resulted in different levels of nuclear phosphorylated ERK. Blockade of ERK activation abolished GnRH-dependent activation of LHβ and FSHβ transcription at both high and low pulse frequencies. These results demonstrate that in perifused LβT2 cells, distinct patterns of ERK activation/inactivation are regulated by GnRH pulse frequency, and the difference in ERK activation may be important for GnRH pulse frequency-dependent differential stimulation of LHβ and FSHβ gene expression.

ERK5 and its role in tumour development

2012 ◽  
Vol 40 (1) ◽  
pp. 251-256 ◽  
Author(s):  
Pamela A. Lochhead ◽  
Rebecca Gilley ◽  
Simon J. Cook
Keyword(s):  
Mitogen Activated Protein Kinase ◽  
Invasion And Migration ◽  
Extracellular Signal Regulated Kinase ◽  
Protein Levels ◽  
Extracellular Signal ◽  
Mapk Signalling ◽  
Mitogen Activated Protein ◽  
Tumour Cell Invasion ◽  
And Migration

The MEK5 [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase 5]/ERK5 pathway is the least well studied MAPK signalling module. It has been proposed to play a role in the pathology of cancer. In the present paper, we review the role of the MEK5/ERK5 pathway using the ‘hallmarks of cancer’ as a framework and consider how this pathway is deregulated. As well as playing a key role in endothelial cell survival and tubular morphogenesis during tumour neovascularization, ERK5 is also emerging as a regulator of tumour cell invasion and migration. Several oncogenes can stimulate ERK5 activity, and protein levels are increased by a novel amplification at chromosome locus 17p11 and by down-regulation of the microRNAs miR-143 and miR-145. Together, these finding underscore the case for further investigation into understanding the role of ERK5 in cancer.

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