scholarly journals Phosphorylation-dependent translocation of sphingosine kinase to the plasma membrane drives its oncogenic signalling

2004 ◽  
Vol 201 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Stuart M. Pitson ◽  
Pu Xia ◽  
Tamara M. Leclercq ◽  
Paul A.B. Moretti ◽  
Julia R. Zebol ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Catalytic Activity ◽  
Mammalian Cells ◽  
Phosphorylation Site ◽  
Sphingosine Kinase ◽  
Direct Consequence ◽  
Oncogenic Signaling ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Sphingosine 1 Phosphate

Sphingosine kinase (SK) 1 catalyzes the formation of the bioactive lipid sphingosine 1-phosphate, and has been implicated in several biological processes in mammalian cells, including enhanced proliferation, inhibition of apoptosis, and oncogenesis. Human SK (hSK) 1 possesses high instrinsic catalytic activity which can be further increased by a diverse array of cellular agonists. We have shown previously that this activation occurs as a direct consequence of extracellular signal–regulated kinase 1/2–mediated phosphorylation at Ser225, which not only increases catalytic activity, but is also necessary for agonist-induced translocation of hSK1 to the plasma membrane. In this study, we report that the oncogenic effects of overexpressed hSK1 are blocked by mutation of the phosphorylation site despite the phosphorylation-deficient form of the enzyme retaining full instrinsic catalytic activity. This indicates that oncogenic signaling by hSK1 relies on a phosphorylation-dependent function beyond increasing enzyme activity. We demonstrate, through constitutive localization of the phosphorylation-deficient form of hSK1 to the plasma membrane, that hSK1 translocation is the key effect of phosphorylation in oncogenic signaling by this enzyme. Thus, phosphorylation of hSK1 is essential for oncogenic signaling, and is brought about through phosphorylation-induced translocation of hSK1 to the plasma membrane, rather than from enhanced catalytic activity of this enzyme.

Role of extracellular signal-regulated kinase (ERK) signaling in nucleotide excision repair and genotoxicity in response to As(III) and Pb(II)

2008 ◽  
Vol 80 (12) ◽  
pp. 2735-2750
Author(s):  
Ju-Pi Li ◽  
Chun-Yu Wang ◽  
Yen-An Tang ◽  
Yun-Wei Lin ◽  
Jia-Ling Yang
Keyword(s):  
Signaling Pathways ◽  
Nucleotide Excision Repair ◽  
Mammalian Cells ◽  
Excision Repair ◽  
Erk Signaling ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Nucleotide Excision

Arsenic and lead can induce genetic injuries and epigenetic signaling pathways in cultured mammalian cells. To test whether signaling pathways affect the extent of genetic injuries, we explored the impacts of extracellular signal-regulated kinase 1 and 2 (ERK) on nucleotide excision repair (NER), cytotoxicity, and genotoxicity following sodium arsenite [As(III)] and lead acetate [Pb(II)]. Sustained ERK activation was observed in human cells exposed to As(III) and Pb(II). As(III) inhibited the cellular NER synthesis capability; conversely, Pb(II) stimulated it. ERK activation contributed to the As(III)-induced NER inhibition and micronucleus formation. In contrast, this signal was required for inducing cellular NER activity and preventing mutagenesis following Pb(II). ERK activation by Pb(II) was dependent on protein kinase C (PKCα) that also exhibited anti-mutagenicity. Enforced expression of ERK signaling markedly elevated the cellular NER activity, which was suppressed by As(III). Nonetheless, ERK activation could counteract the cytotoxicity caused by these two metals. Together, the results indicate that pro-survival ERK signaling exhibits dual and opposing impacts on NER process following As(III) and Pb(II) exposures. The findings also suggest that ERK is an important epigenetic signaling in the determination of metal genotoxicity.

scholarly journals Extracellular Signal-Regulated Kinase Induces the Megakaryocyte GPIIb/CD41 Gene through MafB/Kreisler

2004 ◽  
Vol 24 (10) ◽  
pp. 4534-4545 ◽  
Author(s):  
Joel R. Sevinsky ◽  
Anne M. Whalen ◽  
Natalie G. Ahn
Keyword(s):  
Gene Expression ◽  
Mammalian Cells ◽  
Transcriptional Start Site ◽  
Dominant Negative ◽  
Proximal Promoter ◽  
Specific Gene ◽  
Promoter Regulation ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Megakaryocyte Differentiation

ABSTRACT Extracellular signal-regulated kinase (ERK) facilitates cell cycle progression in most mammalian cells, but in certain cell types prolonged signaling through this pathway promotes differentiation and lineage-specific gene expression through mechanisms that are poorly understood. Here, we characterize the transcriptional regulation of platelet GPIIb integrin (CD41) by ERK during megakaryocyte differentiation. ERK-dependent transactivation involves the proximal promoter of GPIIb within 114 bp upstream of the transcriptional start site. GATA, Ets, and Sp1 consensus sequences within this region are each necessary and function combinatorially in ERK-activated transcription. MafB/Kreisler is induced in response to ERK and synergizes with GATA and Ets to enhance transcription from the proximal promoter. The requirement for MafB in promoter regulation is demonstrated by inhibition of transactivation following dominant-negative or antisense suppression of MafB function. Thus, ERK promotes megakaryocyte differentiation by coordinate regulation of nuclear factors that synergize in GPIIb promoter regulation. These results establish a novel role for MafB as a regulator of ERK-induced gene expression.

scholarly journals The Transcription Factor GATA4 Is Activated by Extracellular Signal-Regulated Kinase 1- and 2-Mediated Phosphorylation of Serine 105 in Cardiomyocytes

2001 ◽  
Vol 21 (21) ◽  
pp. 7460-7469 ◽  
Author(s):  
Qiangrong Liang ◽  
Russell J. Wiese ◽  
Orlando F. Bueno ◽  
Yan-Shan Dai ◽  
Bruce E. Markham ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Phosphorylation Site ◽  
Dominant Negative ◽  
Site Directed Mutagenesis ◽  
Mitogen Activated Protein Kinase ◽  
Cardiomyocyte Hypertrophy ◽  
Hypertrophic Growth ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

ABSTRACT The zinc finger-containing transcription factor GATA4 has been implicated as a critical regulator of multiple cardiac-expressed genes as well as a regulator of inducible gene expression in response to hypertrophic stimulation. Here we demonstrate that GATA4 is itself regulated by the mitogen-activated protein kinase signaling cascade through direct phosphorylation. Site-directed mutagenesis and phospho-specific GATA4 antiserum revealed serine 105 as the primary site involved in agonist-induced phosphorylation of GATA4. Infection of cultured cardiomyocytes with an activated MEK1-expressing adenovirus induced robust phosphorylation of serine 105 in GATA4, while a dominant-negative MEK1-expressing adenovirus blocked agonist-induced phosphorylation of serine 105, implicating extracellular signal-regulated kinase (ERK) as a GATA4 kinase. Indeed, bacterially purified ERK2 protein directly phosphorylated purified GATA4 at serine 105 in vitro. Phosphorylation of serine 105 enhanced the transcriptional potency of GATA4, which was sensitive to U0126 (MEK1 inhibitor) but not SB202190 (p38 inhibitor). Phosphorylation of serine 105 also modestly enhanced the DNA binding activity of bacterially purified GATA4. Finally, induction of cardiomyocyte hypertrophy with an activated MEK1-expressing adenovirus was blocked with a dominant-negative GATA4-engrailed-expressing adenovirus. These results suggest a molecular pathway whereby MEK1-ERK1/2 signaling regulates cardiomyocyte hypertrophic growth through the transcription factor GATA4 by direct phosphorylation of serine 105, which enhances DNA binding and transcriptional activation.

scholarly journals Phosphorylation of Rac1 T108 by Extracellular Signal-Regulated Kinase in Response to Epidermal Growth Factor: a Novel Mechanism To Regulate Rac1 Function

2013 ◽  
Vol 33 (22) ◽  
pp. 4538-4551 ◽  
Author(s):  
Junfeng Tong ◽  
Laiji Li ◽  
Barbara Ballermann ◽  
Zhixiang Wang
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Rho Gtpases ◽  
Fluorescent Protein ◽  
Phosphorylation Site ◽  
Kinase Assay ◽  
Nucleotide Exchange ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Epidermal Growth

Accumulating evidence has implicated Rho GTPases, including Rac1, in many aspects of cancer development. Recent findings suggest that phosphorylation might further contribute to the tight regulation of Rho GTPases. Interestingly, sequence analysis of Rac1 shows that Rac1 T108 within the106PNTP109motif is likely an extracellular signal-regulated kinase (ERK) phosphorylation site and that Rac1 also has an ERK docking site,183KKRKRKCLLL192(D site), at the C terminus. Indeed, we show here that both transfected and endogenous Rac1 interacts with ERK and that this interaction is mediated by its D site. Green fluorescent protein (GFP)-Rac1 is threonine (T) phosphorylated in response to epidermal growth factor (EGF), and EGF-induced Rac1 threonine phosphorylation is dependent on the activation of ERK. Moreover, mutant Rac1 with the mutation of T108 to alanine (A) is not threonine phosphorylated in response to EGF.In vitroERK kinase assay further shows that pure active ERK phosphorylates purified Rac1 but not mutant Rac1 T108A. We also show that Rac1 T108 phosphorylation decreases Rac1 activity, partially due to inhibiting its interaction with phospholipase C-γ1 (PLC-γ1). T108 phosphorylation targets Rac1 to the nucleus, which isolates Rac1 from other guanine nucleotide exchange factors (GEFs) and hinders Rac1's role in cell migration. We conclude that Rac1 T108 is phosphorylated by ERK in response to EGF, which plays an important role in regulating Rac1.

scholarly journals Glycogen Synthase Kinase 3- and Extracellular Signal-Regulated Kinase-Dependent Phosphorylation of Paxillin Regulates Cytoskeletal Rearrangement

2006 ◽  
Vol 26 (7) ◽  
pp. 2857-2868 ◽  
Author(s):  
Xinming Cai ◽  
Min Li ◽  
Julie Vrana ◽  
Michael D. Schaller
Keyword(s):  
Glycogen Synthase ◽  
Phosphorylation Site ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Raw264.7 Cells ◽  
Extracellular Signal Regulated Kinase ◽  
Cytoskeletal Rearrangement ◽  
Extracellular Signal ◽  
And Migration ◽  
Stimulating Factor

ABSTRACT Paxillin is a 68-kDa focal adhesion-associated protein that plays an important role in controlling cell spreading and migration. Phosphorylation of paxillin regulates its biological activity and thus has warranted investigation. Serine 126 and serine 130 were previously identified as two major extracellular signal-regulated kinase (ERK)-dependent phosphorylation sites in Raf-transformed fibroblasts. Here serine 126 is identified as a phosphorylation site induced by lipopolysaccharide (LPS) stimulation of RAW264.7 cells. A number of other stimuli, including adhesion and colony-stimulating factor, induce serine 126 phosphorylation in RAW264.7 cells, and nerve growth factor (NGF) treatment induces serine 126 phosphorylation in PC12 cells. The kinase responsible for phosphorylation of this site is identified as glycogen synthase kinase 3 (GSK-3). Interestingly, this GSK-3-dependent phosphorylation is regulated via an ERK-dependent priming mechanism, i.e., phosphorylation of serine 130. Phosphorylation of S126/S130 was required to promote spreading in paxillin null cells, and LPS-induced spreading of RAW264.7 cells was inhibited by expression of the paxillin S126A/S130A mutant. Furthermore, this mutant also retarded NGF-induced PC12 cell neurite outgrowth. Hence, phosphorylation of paxillin on serines 126 and 130, which is mediated by an ERK/GSK-3 dual-kinase mechanism, plays an important role in cytoskeletal rearrangement.

scholarly journals Genetic Demonstration of a Redundant Role of Extracellular Signal-Regulated Kinase 1 (ERK1) and ERK2 Mitogen-Activated Protein Kinases in Promoting Fibroblast Proliferation

2010 ◽  
Vol 30 (12) ◽  
pp. 2918-2932 ◽  
Author(s):  
Laure Voisin ◽  
Marc K. Saba-El-Leil ◽  
Catherine Julien ◽  
Christophe Frémin ◽  
Sylvain Meloche
Keyword(s):  
Cell Proliferation ◽  
Mammalian Cells ◽  
Replicative Senescence ◽  
The Other ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
The Individual ◽  
Redundant Role

ABSTRACT The extracellular signal-regulated kinase 1 and 2 (ERK1/2) mitogen-activated protein (MAP) kinase signaling pathway plays an important role in the proliferative response of mammalian cells to mitogens. However, the individual contribution of the isoforms ERK1 and ERK2 to cell proliferation control is unclear. The two ERK isoforms have similar biochemical properties and recognize the same primary sequence determinants on substrates. On the other hand, analysis of mice lacking individual ERK genes suggests that ERK1 and ERK2 may have evolved unique functions. In this study, we used a robust genetic approach to analyze the individual functions of ERK1 and ERK2 in cell proliferation using genetically matched primary embryonic fibroblasts. We show that individual loss of either ERK1 or ERK2 slows down the proliferation rate of fibroblasts to an extent reflecting the expression level of the kinase. Moreover, RNA interference-mediated silencing of ERK1 or ERK2 expression in cells genetically disrupted for the other isoform similarly reduces cell proliferation. We generated fibroblasts genetically deficient in both Erk1 and Erk2. Combined loss of ERK1 and ERK2 resulted in a complete arrest of cell proliferation associated with G1 arrest and premature replicative senescence. Together, our findings provide compelling genetic evidence for a redundant role of ERK1 and ERK2 in promoting cell proliferation.

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