101
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Dumaz N, Marais R. Integrating signals between cAMP and the RAS/RAF/MEK/ERK signalling pathways. Based on the anniversary prize of the Gesellschaft für Biochemie und Molekularbiologie Lecture delivered on 5 July 2003 at the Special FEBS Meeting in Brussels. FEBS J 2005; 272:3491-504. [PMID: 16008550 DOI: 10.1111/j.1742-4658.2005.04763.x] [Citation(s) in RCA: 237] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the hallmarks of cAMP is its ability to inhibit proliferation in many cell types, but stimulate proliferation in others. Clearly cAMP has cell type specific effects and the outcome on proliferation is largely attributed to crosstalk from cAMP to the RAS/RAF/mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK pathway. We review the crosstalk between these two ancient and conserved pathways, describing the molecular mechanisms underlying the interactions between these pathways and discussing their possible biological importance.
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Affiliation(s)
- Nicolas Dumaz
- Signal Transduction Team, Cancer Research UK Centre for Cell and Molecular Biology, The Institute of Cancer Research, London, UK
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102
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Tárrega C, Ríos P, Cejudo-Marín R, Blanco-Aparicio C, van den Berk L, Schepens J, Hendriks W, Tabernero L, Pulido R. ERK2 shows a restrictive and locally selective mechanism of recognition by its tyrosine phosphatase inactivators not shared by its activator MEK1. J Biol Chem 2005; 280:37885-94. [PMID: 16148006 DOI: 10.1074/jbc.m504366200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The two regulatory residues that control the enzymatic activity of the mitogen-activated protein (MAP) kinase ERK2 are phosphorylated by the unique MAP kinase kinases MEK1/2 and dephosphorylated by several tyrosine-specific and dual specificity protein phosphatases. Selective docking interactions facilitate these phosphorylation and dephosphorylation events, controlling the specificity and duration of the MAP kinase activation-inactivation cycles. We have analyzed the contribution of specific residues of ERK2 in the physical and functional interaction with the ERK2 phosphatase inactivators PTP-SL and MKP-3 and with its activator MEK1. Single mutations in ERK2 that abrogated the dephosphorylation by endogenous tyrosine phosphatases from HEK293 cells still allowed efficient phosphorylation by endogenous MEK1/2. Discrete ERK2 mutations at the ERK2 docking groove differentially affected binding and inactivation by PTP-SL and MKP-3. Remarkably, the cytosolic retention of ERK2 by its activator MEK1 was not affected by any of the analyzed ERK2 single amino acid substitutions. A chimeric MEK1 protein, containing the kinase interaction motif of PTP-SL, bound tightly to ERK2 through its docking groove and behaved as a gain-of-function MAP kinase kinase that hyperactivated ERK2. Our results provide evidence that the ERK2 docking groove is more restrictive and selective for its tyrosine phosphatase inactivators than for MEK1/2 and indicate that distinct ERK2 residues modulate the docking interactions with activating and inactivating effectors.
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Affiliation(s)
- Céline Tárrega
- Centro de Investigación Príncipe Felipe, Valencia, Spain
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103
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Echevarria D, Belo JA, Martinez S. Modulation of Fgf8 activity during vertebrate brain development. ACTA ACUST UNITED AC 2005; 49:150-7. [PMID: 16111545 DOI: 10.1016/j.brainresrev.2004.12.035] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Accepted: 12/16/2004] [Indexed: 11/19/2022]
Abstract
In recent years much emphasis has been placed on investigation of the precise control of FGF signaling during brain development. Such control is achieved in part by regulatory elements that determine the domains and levels of expression of genes coding for the diverse FGF ligands via specific molecular signaling pathways. There is new knowledge on the operation of such mechanisms in regions of the neural tube involved in the correct patterning of adjacent territories (known as secondary organizers of neural tube pattern). In the present minireview we intend to summarize recent evidence and emerging conclusions on potent modulators that govern the activity of Fgf8 signals in the developing vertebrate brain, focusing our attention on the best known secondary organizer, the isthmic organizer.
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Affiliation(s)
- Diego Echevarria
- Institute of Neuroscience, University Miguel Hernandez (UMH-CSIC), Carretera de Valencia (N332), San Juan, Alicante 03550, Spain.
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104
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Nyunoya T, Monick MM, Powers LS, Yarovinsky TO, Hunninghake GW. Macrophages Survive Hyperoxia via Prolonged ERK Activation Due to Phosphatase Down-regulation. J Biol Chem 2005; 280:26295-302. [PMID: 15901735 DOI: 10.1074/jbc.m500185200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Macrophages exposed to hyperoxia in the lung continue to survive for prolonged periods. We previously reported (Nyunoya, T., Powers, L. S., Yarovinsky, T. O., Butler, N. S., Monick, M. M., and Hunninghake, G. W. (2003) J. Biol. Chem. 278, 36099-36106) that hyperoxia induces cell cycle arrest and sustained extracellular signal-related kinase (ERK) activity in macrophages. In this study, we determined the mechanisms of hyperoxia-induced ERK activation and how ERK activity plays a pro-survival role in hyperoxia-exposed cells. Inhibition of ERK activity decreased survival of hyperoxia-exposed macrophages. This was due, at least in part, to down-regulation of the pro-apoptotic Bcl-2 family member, BimEL. In determining the mechanism of ERK activation by hyperoxia, we found that ERK activation was not associated with hyperoxia-induced activation of the upstream ERK kinase mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2. When we examined the ability of whole cell lysates from hyperoxia-exposed cells to dephosphorylate purified phosphorylated ERK, we found decreased ERK-directed phosphatase activity. Two particular ERK-directed phosphatases (protein phosphatase 2A and MAPK phosphatase-3) demonstrated decreased activity in hyperoxia-exposed cells. Moreover, whole cell lysates from normoxia-exposed cells depleted of PP2A or MAPK phosphatase-3 were also less able to dephosphorylate ERK. These data demonstrate that, in hyperoxia-exposed macrophages, sustained activation of ERK due to phosphatase down-regulation permits macrophage survival via effects on the balance between pro- and anti-apoptotic Bcl-2 family proteins.
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Affiliation(s)
- Toru Nyunoya
- Division of Pulmonary, Critical Care, and Occupational Medicine, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242, USA.
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105
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Bruno KS, Tenjo F, Li L, Hamer JE, Xu JR. Cellular localization and role of kinase activity of PMK1 in Magnaporthe grisea. EUKARYOTIC CELL 2005; 3:1525-32. [PMID: 15590826 PMCID: PMC539019 DOI: 10.1128/ec.3.6.1525-1532.2004] [Citation(s) in RCA: 228] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A mitogen-activated protein (MAP) kinase gene, PMK1, is known to regulate appressorium formation and infectious hyphal growth in the rice blast fungus Magnaporthe grisea. In this study, we constructed a green fluorescent protein gene-PMK1 fusion (GFP-PMK1) to examine the expression and localization of PMK1 in M. grisea during infection-related morphogenesis. The GFP-PMK1 fusion encoded a functional protein that complemented the defect of the pmk1 deletion mutant in appressorium formation and plant infection. Although a weak GFP signal was detectable in vegetative hyphae, conidia, and germ tubes, the expression of GFP-Pmk1 was increased in appressoria and developing conidia. Nuclear localization of GFP-Pmk1 proteins was observed in a certain percentage of appressoria. A kinase-inactive allele and a nonphosphorylatable allele of PMK1 were constructed by site-directed mutagenesis. Expression of these mutant PMK1 alleles did not complement the pmk1 deletion mutant. These data confirm that kinase activity and activation of PMK1 by the upstream MAP kinase kinase are required for appressorium formation and plant infection in M. grisea. When overexpressed with the RP27 promoter in the wild-type strain, both the kinase-inactive and nonphosphorylatable PMK1 fusion proteins caused abnormal germ tube branching. Overexpression of these PMK1 mutant alleles may interfere with the function of native PMK1 during appressorium formation.
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Affiliation(s)
- Kenneth S Bruno
- Department of Botany and Plant Pathology, Lilly Hall, Purdue University, West Lafayette, IN 47907, USA
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106
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Abstract
With a better understanding of the cellular stress response, it has become evident that catalytic modules consisting of kinases that mediate the activation of downstream effector components are subject to multiple layers of regulation. Such regulatory mechanisms are not limited to those involving scaffold proteins or protein phosphatases, and they appear to include a growing number of modifications by ubiquitin and ubiquitin-like proteins. The role of ubiquitin in the regulation of mitogen-activated protein kinase (MAPK) emerges as a paradigm for understanding the role of ubiquitination in regulating other signal transduction pathways. Ubiquitination influences signal diversification and limits the duration of the signal through its role in the assembly of protein kinase complexes, subcellular localization, and the actual degradation of the kinase or its substrate. This review summarizes our current understanding of the roles of ubiquitin in regulating MAPK signaling.
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Affiliation(s)
- Aaron Laine
- Signal Transduction Program, The Burnham Institute, La Jolla, CA 92037, USA
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107
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Anguelova E, Beuvon F, Leonard N, Chaverot N, Varlet P, Couraud PO, Daumas-Duport C, Cazaubon S. Functional endothelin ET B receptors are selectively expressed in human oligodendrogliomas. ACTA ACUST UNITED AC 2005; 137:77-88. [PMID: 15950764 DOI: 10.1016/j.molbrainres.2005.02.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 02/03/2005] [Accepted: 02/13/2005] [Indexed: 11/19/2022]
Abstract
Endothelin-1 (ET-1), a vasoactive and mitogenic peptide mainly produced by vascular endothelial cells, may be involved in the progression of several human tumors. Here, we present an immunohistochemical analysis of the expression pattern of ET-1 receptor subtypes (ET(A)-R and ET(B)-R) and a functional study of their potential role in human oligodendrogliomas and oligoastrocytomas. By comparison, we assessed the corresponding expression patterns of glioblastomas. Interestingly, a nuclear localization of ET-1 receptor subtypes (associated or not with a cytoplasmic labeling) was constantly observed in tumor cells from all three glioma types. Moreover, we noted a distinct receptor distribution in the different gliomas: a nuclear expression of ET(B)-R by tumor cells was found to be restricted to oligodendrogliomas and oligoastrocytomas, while a nuclear expression of ET(A)-R was only detected in tumor cells from some glioblastomas. Using primary cultures of oligodendroglial tumor cells, we confirmed the selective expression of nuclear ET(B)-R, together with a plasma membrane expression, and further demonstrated that this receptor was functionally coupled to intracellular signaling pathways known to be involved in cell survival and/or proliferation: extracellular signal-regulated kinase and focal adhesion kinase activation, actin cytoskeleton reorganization. In addition, impairment of ET(B)-R activation in these cells by in vitro treatment with an ET(B)-R-specific antagonist induced cell death. These data point to ET-1 as a possible survival factor for oligodendrogliomas via ET(B)-R activation and suggest that ET(B)-R-specific antagonists might constitute a potential therapeutic alternative for oligodendrogliomas.
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Affiliation(s)
- E Anguelova
- Department of Cell Biology, Institut Cochin, INSERM U567, CNRS UMR 8104, IFR116, 22 rue Méchain, 75014 Paris, France
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108
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Takekawa M, Tatebayashi K, Saito H. Conserved Docking Site Is Essential for Activation of Mammalian MAP Kinase Kinases by Specific MAP Kinase Kinase Kinases. Mol Cell 2005; 18:295-306. [PMID: 15866172 DOI: 10.1016/j.molcel.2005.04.001] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Revised: 03/09/2005] [Accepted: 04/05/2005] [Indexed: 11/29/2022]
Abstract
Mammalian mitogen-activated protein kinase (MAPK) cascades control various cellular events, ranging from cell growth to apoptosis, in response to external stimuli. A conserved docking site, termed DVD, is found in the mammalian MAP kinase kinases (MAPKKs) belonging to the three major subfamilies, namely MEK1, MKK4/7, and MKK3/6. The DVD sites bind to their specific upstream MAP kinase kinase kinases (MAPKKKs), including MTK1 (MEKK4), ASK1, TAK1, TAO2, MEKK1, and Raf-1. DVD site is a stretch of about 20 amino acids immediately on the C-terminal side of the MAPKK catalytic domain. Mutations in the DVD site strongly inhibited MAPKKs from binding to, and being activated by, their specific MAPKKKs, both in vitro and in vivo. DVD site mutants could not be activated by various external stimuli in vivo. Synthetic DVD oligopeptides inhibited specific MAPKK activation, both in vitro and in vivo, demonstrating the critical importance of the DVD docking in MAPK signaling.
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Affiliation(s)
- Mutsuhiro Takekawa
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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109
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Agassandian M, Zhou J, Tephly LA, Ryan AJ, Carter AB, Mallampalli RK. Oxysterols inhibit phosphatidylcholine synthesis via ERK docking and phosphorylation of CTP:phosphocholine cytidylyltransferase. J Biol Chem 2005; 280:21577-87. [PMID: 15788406 DOI: 10.1074/jbc.m412409200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Surfactant deficiency contributes to acute lung injury and may result from the elaboration of bioactive lipids such as oxysterols. We observed that the oxysterol 22-hydroxycholesterol (22-HC) in combination with its obligate partner, 9-cis-retinoic acid (9-cis-RA), decreased surfactant phosphatidylcholine (PtdCho) synthesis by increasing phosphorylation of the regulatory enzyme CTP:phosphocholine cytidylyltransferase-alpha (CCTalpha). Phosphorylation of CCTalpha decreased its activity. 22-HC/9-cis-RA inhibition of PtdCho synthesis was blocked by PD98059 or dominant-negative ERK (p42 kinase). Overexpression of constitutively active MEK1, the kinase upstream of p42 kinase, increased CCTalpha phosphorylation. Expression of truncated CCTalpha mutants lacking proline-directed sites within the C-terminal phosphorylation domain partially blocked oxysterol-mediated inhibition of PtdCho synthesis. Mutagenesis of Ser315 within CCTalpha was both required and sufficient to confer significant resistance to 22-HC/9-cis-RA inhibition of PtdCho synthesis. A novel putative ERK-docking domain N-terminal to this phosphoacceptor site was mapped within the CCTalpha membrane-binding domain (residues 287-300). The results are the first demonstration of a physiologically relevant phosphorylation site and docking domain within CCTalpha that serve as targets for ERKs, resulting in inhibition of surfactant synthesis.
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Affiliation(s)
- Marianna Agassandian
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City 52242, USA
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110
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Price DM, Chik CL, Terriff D, Weller J, Humphries A, Carter DA, Klein DC, Ho AK. Mitogen-activated protein kinase phosphatase-1 (MKP-1): >100-fold nocturnal and norepinephrine-induced changes in the rat pineal gland. FEBS Lett 2005; 577:220-6. [PMID: 15527789 DOI: 10.1016/j.febslet.2004.09.083] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Accepted: 09/15/2004] [Indexed: 11/21/2022]
Abstract
The norepinephrine-driven increase in mitogen-activated protein kinase (MAPK) activity is part of the mechanism that regulates arylalkylamine N-acetyltransferase (AA-NAT) activity in the rat pineal gland. We now report a marked nocturnal increase in the expression of a MAPK phosphatase, MAP kinase phosphatase-1 (MKP-1), that was blocked by maintaining animals in constant light or treatment with propranolol. MKP-1 expression was regulated by norepinephrine acting through both alpha- and beta-adrenergic receptors. These results establish a nocturnal increase in pineal MKP-1 expression that is under the control of a photoneural system. Because substrates of MKP-1 can influence AA-NAT activity, our findings suggest the involvement of MKP-1 in the regulation of the nocturnal AA-NAT signal.
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Affiliation(s)
- Donald M Price
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alta., Canada T6G 2H7
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111
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Mandl M, Slack DN, Keyse SM. Specific inactivation and nuclear anchoring of extracellular signal-regulated kinase 2 by the inducible dual-specificity protein phosphatase DUSP5. Mol Cell Biol 2005; 25:1830-45. [PMID: 15713638 PMCID: PMC549372 DOI: 10.1128/mcb.25.5.1830-1845.2005] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 09/24/2004] [Accepted: 11/30/2004] [Indexed: 11/20/2022] Open
Abstract
The mechanisms which determine the nuclear accumulation and inactivation of the extracellular signal-regulated kinase 1 (ERK1) or ERK2 mitogen-activated protein (MAP) kinases are poorly understood. Here we demonstrate that DUSP5, an inducible nuclear phosphatase, interacts specifically with ERK2 via a kinase interaction motif (KIM) within its amino-terminal noncatalytic domain. This binding determines the substrate specificity of DUSP5 in vivo, as it inactivates ERK2 but not Jun N-terminal protein kinase or p38 MAP kinase. Using green fluorescent protein fusions, we identify within this same domain of DUSP5 a functional nuclear localization signal (NLS) which functions independently of the KIM. Moreover, we demonstrate that the expression of DUSP5 causes both nuclear translocation and sequestration of inactive ERK2. Nuclear anchoring is ERK2 specific and requires both interactions between the DUSP5 KIM and the common docking site of ERK2 and a functional NLS within DUSP5. Finally, the expression of a catalytically inactive mutant of DUSP5 also tethers ERK2 within the nucleus. Furthermore, this nuclear ERK2 is phosphorylated by MAP kinase kinase in response to growth factors and also activates transcription factor Elk-1. We conclude that DUSP5 is an inducible nuclear ERK-specific MAP kinase phosphatase that functions as both an inactivator of and a nuclear anchor for ERK2 in mammalian cells. In addition, our data indicate that the cytoplasm may not be an exclusive site of MAP kinase activation.
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Affiliation(s)
- Margret Mandl
- Cancer Research UK, Molecular Pharmacology Unit, Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, United Kingdom
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112
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Ramsay RG, Ciznadija D, Sicurella C, Reyes N, Mitchelhill K, Darcy PK, D'Abaco G, Mantamadiotis T. Colon Epithelial Cell Differentiation Is Inhibited by Constitutive c-Myb Expression or Mutant APC Plus Activated RAS. DNA Cell Biol 2005; 24:21-9. [PMID: 15684716 DOI: 10.1089/dna.2005.24.21] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Blocked differentiation is a hallmark of cancer cells and the restoration of differentiation programs in vivo is an actively pursued clinical aim. Understanding the key regulators of cyto-differentiation may focus therapies on molecules that reactivate this process. c-myb expression declines rapidly when human colon cancer epithelial cells are induced to differentiate with the physiologically relevant short-chain fatty acid, sodium butyrate. These cells show increased expression of alkaline phosphatase and cytokeratin 8. Similarly, murine Immorto-epithelial cells derived from wild-type colon cells also show c-myb mRNA declines when induced to differentiate with sodium butyrate. Immorto-cells harboring a single APC mutation are indistinguishable from wild-type cells with regard to differentiation, while addition of activated RAS alone markedly enhances differentiation. In marked contrast, complete differentiation arrest occurs when both APC and RAS are mutated. Expression of MybER, a 4-hydroxytamoxifen-activatable form of c-Myb, blocks differentiation in wildtype and APC mutant Immorto-cell lines as well as LIM1215 human colon carcinoma cells. These data identify two pathways of oncogenic change that lead to retarded epithelial cell differentiation, one involving the presence of a single APC mutation in conjunction with activated RAS or alternatively constitutive c-myb expression.
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Affiliation(s)
- Robert G Ramsay
- Differentiation and Transcription Laboratory, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, University of Melbourne, Australia.
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113
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Poliakov A, Cotrina M, Wilkinson DG. Diverse roles of eph receptors and ephrins in the regulation of cell migration and tissue assembly. Dev Cell 2004; 7:465-80. [PMID: 15469835 DOI: 10.1016/j.devcel.2004.09.006] [Citation(s) in RCA: 339] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Eph receptor tyrosine kinases and ephrins have key roles in regulation of the migration and adhesion of cells required to form and stabilize patterns of cell organization during development. Activation of Eph receptors or ephrins can lead either to cell repulsion or to cell adhesion and invasion, and recent work has found that cells can switch between these distinct responses. This review will discuss biochemical mechanisms and developmental roles of the diverse cell responses controlled by Eph receptors and ephrins.
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Affiliation(s)
- Alexei Poliakov
- Division of Developmental Neurobiology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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114
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Burack WR, Shaw AS. Live Cell Imaging of ERK and MEK: simple binding equilibrium explains the regulated nucleocytoplasmic distribution of ERK. J Biol Chem 2004; 280:3832-7. [PMID: 15546878 DOI: 10.1074/jbc.m410031200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In response to epidermal growth factor (EGF), the mitogen-activated protein kinase ERK2 translocates into the nucleus. To probe the mechanisms regulating the subcellular localization of ERK2, we used live cell imaging to examine the interaction between MEK1 and ERK2. Fluorescence resonance energy transfer (FRET) studies show that MEK1 and ERK2 directly interact and demonstrate that this interaction in the cytoplasm is largely responsible for cytoplasmic retention of ERK2. Stimulation with EGF caused loss of FRET as ERK separated from MEK and moved into the nucleus. FRET was recovered as ERK returned to the cytosol, indicating ERK reassociation with MEK in the cytoplasm. The EGF-induced transit of ERK through the nucleus was complete within 20 min, and there was no significant movement of MEK into the nucleus. Fluorescence recovery after photobleaching experiments was used to assess the rate of movement of MEK and ERK. The steady-state rate of ERK entry into the nucleus in resting cells was energy-independent and greater than the rate of ERK entry upon EGF stimulation. This suggests that the rate constant for ERK transport across the nuclear membrane is not limiting nuclear entry. Thus, we suggest that the movement of ERK into and out of the nucleus in response to agonist occurs primarily by diffusion and is controlled by interactions with binding partners in the cytosol and nucleus. No evidence of ERK dimerization was detected by FRET methods; the kinetics for nucleocytoplasmic transport were unaffected by mutations in the ERK putative dimerization domain.
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Affiliation(s)
- W Richard Burack
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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115
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Abstract
Protein kinases, particularly mitogen-activated protein kinases and receptor-tyrosine kinases play crucial roles in mammalian cellular metabolism by regulating intracellular signaling pathways that control proliferation, differentiation, cytokine gene induction and cytokine responsiveness, matrix metalloproteinase gene expression, mechanical transduction, as well as programmed cell death (apoptosis). Many of these pathways are also important components of cartilage homeostasis because alterations in intracellular signaling pathways appear to play a prominent role in chondrocyte dysfunction that is part of osteoarthritis pathogenesis and disease progression. Several mitogen-activated protein kinases and receptor-tyrosine kinases have been characterized as participating in chondrocyte signaling pathways. They are c-Jun-amino-terminal protein kinase, p38 kinase, extracellular signal-regulated protein kinase, and Ror2. Janus kinases and signal transducers and activators of transcription factors (Janus kinase/signal transducers and activators of transcription pathway) are also implicated in modulating the chondrogenic phenotype. Mitogen-activated protein kinase activation is required for their role as phosphorylating enzymes. Activation results from mitogen-activated protein kinase phosphorylation carried out by at least seven upstream kinases known as mitogen-activated protein kinase kinases. Additional upstream kinases (for example, MKKKKs and MKKKs) often require low molecular weight GTP-binding proteins to mediate the mitogen-activated protein-kinase kinases cascade. Identifying the functions of mitogen-activated protein kinases in normal and aging cartilage and the extent to which mitogen-activated protein kinases may be altered in osteoarthritis cartilage and synovium will be critical for developing novel therapies for osteoarthritis management.
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Affiliation(s)
- Charles J Malemud
- Department of Medicine, Case Western Reserve University School of Medicine, University Hospitals of Cleveland, Cleveland, OH 44106, USA.
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116
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Karlsson M, Mathers J, Dickinson RJ, Mandl M, Keyse SM. Both nuclear-cytoplasmic shuttling of the dual specificity phosphatase MKP-3 and its ability to anchor MAP kinase in the cytoplasm are mediated by a conserved nuclear export signal. J Biol Chem 2004; 279:41882-91. [PMID: 15269220 DOI: 10.1074/jbc.m406720200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MAP kinase phosphatase (MKP)-3 is a cytoplasmic dual specificity protein phosphatase that specifically binds to and inactivates the ERK1/2 MAP kinases in mammalian cells. However, the molecular basis of the cytoplasmic localization of MKP-3 or its physiological significance is unknown. We have used MKP-3-green fluorescent protein fusions in conjunction with leptomycin B to show that the cytoplasmic localization of MKP-3 is mediated by a chromosome region maintenance-1 (CRM1)-dependent nuclear export pathway. Furthermore, the nuclear translocation of MKP-3 seen in the presence of leptomycin B is mediated by an active process, indicating that MKP-3 shuttles between the nucleus and cytoplasm. The amino-terminal noncatalytic domain of MKP-3 is both necessary and sufficient for nuclear export of the phosphatase and contains a single functional leucine-rich nuclear export signal (NES). Even though this domain of the protein also mediates the binding of MKP-3 to MAP kinase, we show that mutations of the kinase interaction motif which abrogate ERK2 binding do not affect MKP-3 localization. Conversely, mutation of the NES does not affect either the binding or phosphatase activity of MKP-3 toward ERK2, indicating that the kinase interaction motif and NES function independently. Finally, we demonstrate that the ability of MKP-3 to cause the cytoplasmic retention of ERK2 requires both a functional kinase interaction motif and NES. We conclude that in addition to its established function in the regulated dephosphorylation and inactivation of MAP kinase, MKP-3 may also play a role in determining the subcellular localization of its substrate. Our results reinforce the idea that regulatory proteins such as MKP-3 may play a key role in the spatio-temporal regulation of MAP kinase activity.
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Affiliation(s)
- Maria Karlsson
- Cancer Research UK Molecular Pharmacology Unit, Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, United Kingdom
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117
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Torii S, Kusakabe M, Yamamoto T, Maekawa M, Nishida E. Sef is a spatial regulator for Ras/MAP kinase signaling. Dev Cell 2004; 7:33-44. [PMID: 15239952 DOI: 10.1016/j.devcel.2004.05.019] [Citation(s) in RCA: 215] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Revised: 05/06/2004] [Accepted: 05/11/2004] [Indexed: 01/27/2023]
Abstract
Spatiotemporal control of the Ras/ERK MAP kinase signaling pathway is among the key mechanisms for regulating a wide variety of cellular processes. In this study, we report that human Sef (hSef), a recently identified inhibitor whose action mechanism has not been fully defined, acts as a molecular switch for ERK signaling by specifically blocking ERK nuclear translocation without inhibiting its activity in the cytoplasm. Thus, hSef binds to activated forms of MEK, inhibits the dissociation of the MEK-ERK complex, and blocks nuclear translocation of activated ERK. Consequently, hSef inhibits phosphorylation and activation of the nuclear ERK substrate Elk-1, while it does not affect phosphorylation of the cytoplasmic ERK substrate RSK2. Downregulation of endogenous hSef by hSef siRNA enhances the stimulus-induced ERK nuclear translocation and the activity of Elk-1. These results thus demonstrate that hSef acts as a spatial regulator for ERK signaling by targeting ERK to the cytoplasm.
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Affiliation(s)
- Satoru Torii
- Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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118
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Kyosseva SV. The role of the extracellular signal-regulated kinase pathway in cerebellar abnormalities in schizophrenia. THE CEREBELLUM 2004; 3:94-9. [PMID: 15233576 DOI: 10.1080/14734220410029164] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent postmortem and functional imaging studies have revealed that cerebellar abnormalities may play a role in the pathophysiology of schizophrenia. Cerebellum is a part of the cortical-subcortical-cerebellar circuitry that is involved in higher cognitive functions. Deficits in cognition, including information, executive functions, attention, emotion, and memory have been described in patients with schizophrenia. Given the pivotal role of mitogen-activated protein (MAP) kinase pathways in regulation of neuronal function and especially the role of extracellular-signal regulated kinase (ERK) in synaptic plasticity, cell survival, learning and memory, the importance of MAP kinases in schizophrenia is being increasingly recognized. In this mini-review is summarized recent evidence from human postmortem studies and the phencyclidine (PCP) pharmacological model of schizophrenia that ERK signaling pathway could contribute to the pathogenic events that occur in the cerebellum in schizophrenia.
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Affiliation(s)
- Svetlana V Kyosseva
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
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119
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Abstract
The ERK cascade is activated by hormones, cytokines, and growth factors that result in either proliferation or growth arrest depending on the duration and intensity of the ERK activation. Here we provide evidence that the MEK1/ERK module preferentially provides proliferative signals, whereas the MEK2/ERK module induces growth arrest at the G1/S boundary. Depletion of either MEK subtype by RNA interference generated a unique phenotype. The MEK1 knock down led to p21cip1 induction and to the appearance of cells with a senescence-like phenotype. Permanent ablation of MEK1 resulted in reduced colony formation potential, indicating the importance of MEK1 for long term proliferation and survival. MEK2 deficiency, in contrast, was accompanied by a massive induction of cyclin D expression and, thus, CDK4/6 activation followed by nucleophosmin hyperphosphorylation and centrosome over-amplification. Our results suggest that the two MEK subtypes have distinct ways to contribute to a regulated ERK activity and cell cycle progression.
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Affiliation(s)
- Siegfried Ussar
- Boehringer Ingelheim Austria GmbH, Dr. Boehringer Gasse 5-11, A-1121 Vienna
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120
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Bose C, Bhuvaneswaran C, Udupa KB. Altered mitogen-activated protein kinase signal transduction in human skin fibroblasts during in vitro aging: differential expression of low-density lipoprotein receptor. J Gerontol A Biol Sci Med Sci 2004; 59:126-35. [PMID: 14999025 DOI: 10.1093/gerona/59.2.b126] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The purpose of the study was to investigate the correlation of low-density lipoprotein receptor (LDLr) and mitogen-activated protein kinases (MAPK) in fibroblasts after serial passage in vitro. We used early-passage ( approximately 20 mean population division, MPD) and late-passage ( approximately 60 MPD) human skin fibroblasts to study the LDLr expression and MAPK at basal and after interleukin-1beta (IL-1beta) stimulation. We found a reduced LDLr expression in late-passage fibroblasts in comparison with early-passage fibroblasts, and late-passage fibroblasts showed a delayed induction of MAPK after IL-1beta stimulation, confirmed by the delay in translocation of MAPK from cytoplasmic to nuclear fraction. Using two specific inhibitors of MAPK, we could show a reduced LDLr expression in early-passage fibroblasts, indicating a direct relationship between MAPK signaling and LDLr expression. We conclude that one of the reasons for reduced LDLr gene expression in late passage fibroblast is related to MAPK signaling.
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Affiliation(s)
- Chhanda Bose
- Donald W. Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences and Medical Research, Central Arkansas Veterans Healthcare System, Little Rock, USA
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121
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Abstract
The fibroblast growth factors (FGFs) represent a large family of ligands that activate signal transduction pathways leading to diverse biological responses, including many involved in various processes during development. Here, we discuss the discovery of a subset of conserved FGF target genes that encode feedback regulators of FGF signaling itself. Members of the Sprouty, Sef, and mitogen-activated protein kinase phosphatase families are negative modulators of FGF signaling, whereas positive factors that promote FGF signaling include the ETS transcription factors ERM and PEA3 and the transmembrane protein XFLRT3. These molecules affect the FGF signaling cascade at different levels to regulate the final output of the pathway. This multilayered regulation suggests that precise adjustment of FGF signaling is critical in development.
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Affiliation(s)
- Michael Tsang
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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122
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Lee J, Rudd JJ, Macioszek VK, Scheel D. Dynamic changes in the localization of MAPK cascade components controlling pathogenesis-related (PR) gene expression during innate immunity in parsley. J Biol Chem 2004; 279:22440-8. [PMID: 15001572 DOI: 10.1074/jbc.m401099200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The activation of mitogen-activated protein kinase (MAPK) cascades is an important mechanism for stress adaptation through the control of gene expression in mammals, yeast, and plants. MAPK activation has emerged as a common mechanism by which plants trigger pathogen defense responses following innate immune recognition of potential microbial pathogens. We are studying the non-host plant defense response of parsley to attempted infection by Phytophthora species using an experimental system of cultured parsley cells and the Phytophthora-derived Pep-13 peptide elicitor. Following receptor-mediated recognition of this peptide, parsley cells trigger a multifaceted innate immune response, involving the activation of three MAPKs that have been shown to function in the oxidative burst-independent activation of defense gene expression. Using this same experimental model we now report the identification of a MAPK kinase (MAPKK) that functions upstream in this pathway. This kinase, referred to as PcMKK5 based on sequence similarity to Arabidopsis thaliana AtMKK5, is activated in parsley cells following Pep-13 treatment and functions as an in vivo activator of all three MAPKs previously shown to be involved in this response. Gain- and loss-of-function mutant versions of PcMKK5, when used in protoplast co-transfection assays, demonstrated that kinase activity of PcMKK5 is required for PR gene promoter activation following Pep-13 treatment. Furthermore, using specific antibodies and immunofluorescent labeling, we demonstrate that activation of MAPKs in parsley cells correlates with an increase in their nuclear localization, which is not detectable for activated PcMKK5. These results suggest that activation of gene expression through MAPK cascades during innate immune responses in plants involves dynamic changes in the localization of the proteins involved, which may reflect the distribution of key protein substrates for the activated MAPKs.
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Affiliation(s)
- Justin Lee
- Department of Stress and Developmental Biology, Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle (Saale), Germany
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123
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Bulayeva NN, Gametchu B, Watson CS. Quantitative measurement of estrogen-induced ERK 1 and 2 activation via multiple membrane-initiated signaling pathways. Steroids 2004; 69:181-92. [PMID: 15072920 PMCID: PMC1201430 DOI: 10.1016/j.steroids.2003.12.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2003] [Revised: 11/24/2003] [Accepted: 12/16/2003] [Indexed: 12/20/2022]
Abstract
Estradiol (E2) and other steroids have recently been shown to initiate various intracellular signaling cascades from the plasma membrane, including those stimulating mitogen-activated protein kinases (MAPKs), and particularly extracellular-regulated kinases (ERKs). In this study we demonstrated the ability of E2 to activate ERKs in the GH3/B6/F10 pituitary tumor cell line, originally selected for its enhanced expression of membrane estrogen receptor-alpha (mERalpha). We compared E2 to its cell-impermeable analog (E2 conjugated to peroxidase, E2-P), and to the synthetic estrogen diethylstilbestrol (DES). Time-dependent ERK activation was quantified with a novel fixed cell-based immunoassay developed to efficiently determine activation by multiple compounds over multiple parameters. Both E2 and DES produced bimodal responses, but with distinctly different time courses of enzyme phosphorylation (activation) and inactivation; E2-P induced a monophasic ERK activation. E2 also phosphorylated ERKs in concentration-dependent manner with two concentration optima (10(-14) and 10(-8)M). Inhibitors were employed to determine pathway (ER, EGFR, membrane organization, PI3 kinase, Src kinase, Ca2+) involvement and timing of pathway activations; all affected ERK activation as early as 3-6 min, suggesting simultaneous, not sequential, activation. Therefore, E2 and other estrogenic compounds can produce rapid ERK phosphorylations via nongenomic pathways, using more than one pathway for signal generation.
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Affiliation(s)
- Nataliya N. Bulayeva
- Department of Human Biological Chemistry & Genetics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Bahiru Gametchu
- National Institutes of Health (NIH), 6701 Rockledge Drive, Bethesda, MD 20892, USA
| | - Cheryl S. Watson
- Department of Human Biological Chemistry & Genetics, University of Texas Medical Branch, Galveston, TX 77555, USA
- * Corresponding author. Tel./fax: +1-409-772-2382. E-mail address: (C.S. Watson)
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124
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Sinnett-Smith J, Zhukova E, Hsieh N, Jiang X, Rozengurt E. Protein kinase D potentiates DNA synthesis induced by Gq-coupled receptors by increasing the duration of ERK signaling in swiss 3T3 cells. J Biol Chem 2004; 279:16883-93. [PMID: 14963034 DOI: 10.1074/jbc.m313225200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Protein kinase D (PKD) potentiates cellular DNA synthesis in response to G protein-coupled receptor (GPCR) agonists but the mechanism(s) involved has not been elucidated. Here, we examined whether PKD overexpression in Swiss 3T3 cells regulates the activation/inactivation kinetics of the extracellular-regulated protein kinase (ERK) in response to the mitogenic GPCR agonists bombesin and vasopressin. Addition of bombesin or vasopressin to Swiss 3T3 cells overexpressing PKD induced a striking increase in the duration of MEK/ERK/RSK activation as compared with cultures of either control Swiss 3T3 cells or Swiss 3T3 cells expressing a kinase-inactive PKD mutant. In contrast, the duration of ERK activation in response to epidermal growth factor, which acts via protein kinase C/PKD-independent pathways, was not increased. Furthermore, bombesin or vasopressin promoted a striking increase in phosphorylation (at Ser-374) and accumulation of c-Fos (the c-fos proto-oncogene product) in Swiss 3T3 cells overexpressing wild-type (but not kinase-inactive) PKD. Inhibition of the sustained phase of ERK/RSK activation abrogated the increase in c-Fos accumulation and DNA synthesis induced by bombesin or vasopressin in PKD-overexpressing cells. Our results demonstrate that PKD selectively potentiates mitogenesis induced by bombesin or vasopressin in Swiss 3T3 cells by increasing the duration of MEK/ERK/RSK signaling.
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Affiliation(s)
- James Sinnett-Smith
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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125
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Sarjeant JM, Lawrie A, Kinnear C, Yablonsky S, Leung W, Massaeli H, Prichett W, Veinot JP, Rassart E, Rabinovitch M. Apolipoprotein D inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell proliferated by preventing translocation of phosphorylated extracellular signal regulated kinase 1/2 to the nucleus. Arterioscler Thromb Vasc Biol 2003; 23:2172-7. [PMID: 14551159 DOI: 10.1161/01.atv.0000100404.05459.39] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Elevated apolipoprotein D (apoD) levels are associated with reduced proliferation of cancer cells. We therefore investigated whether apoD, which occurs free or associated with HDL, suppresses vascular smooth muscle cell (VSMC) proliferation, which is related to the pathobiology of disease. METHODS AND RESULTS Intense immunoreactivity for apoD was observed in human atherosclerotic plaque but not in normal coronary artery. However, an increase in apoD mRNA was seen in quiescent relative to proliferating fetal lamb aortic VSMCs, and in the rat aortic VSMC line (A10), we demonstrated uptake of apoD from serum. Stable transfection of apoD in A10 cells in the absence of serum did not influence VSMC proliferation assessed by [3H]-thymidine incorporation. ApoD, administered at a dose of 100 ng/mL, completely inhibited basal as well as platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation (P<0.01) but had no effect on fibroblast growth factor-induced VSMC proliferation. ApoD did not suppress PDGF-BB or fibroblast growth factor-2-induced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 but selectively inhibited PDGF-BB-mediated ERK1/2 nuclear translocation. CONCLUSIONS Our data suggest that apoD selectively modulates the proliferative response of VSMC to growth factors by a mechanism related to nuclear translocation of ERK1/2.
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MESH Headings
- Animals
- Aorta
- Apolipoproteins/biosynthesis
- Apolipoproteins/genetics
- Apolipoproteins/pharmacology
- Apolipoproteins/physiology
- Apolipoproteins D
- Arteriosclerosis/metabolism
- Becaplermin
- Cell Division/drug effects
- Cell Division/genetics
- Cell Division/physiology
- Cells, Cultured
- Coronary Vessels/chemistry
- Coronary Vessels/pathology
- Coronary Vessels/physiology
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/metabolism
- Muscle, Smooth, Vascular/chemistry
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/metabolism
- Phosphorylation/drug effects
- Platelet-Derived Growth Factor/antagonists & inhibitors
- Platelet-Derived Growth Factor/physiology
- Protein Transport/drug effects
- Protein Transport/physiology
- Proto-Oncogene Proteins c-sis
- RNA, Messenger/biosynthesis
- RNA, Messenger/metabolism
- Rats
- Sheep
- Transfection
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Affiliation(s)
- Jennifer M Sarjeant
- Cardiovascular Research Program, The Hospital for Sick Children, and the Department of Pediatrics, University of Toronto
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