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Nhu Ngoc Van T, Morris MC. Fluorescent Sensors of Protein Kinases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 113:217-74. [DOI: 10.1016/b978-0-12-386932-6.00006-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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52
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Li D, Fu TM, Nan J, Liu C, Li LF, Su XD. Structural basis for the autoinhibition of the C-terminal kinase domain of human RSK1. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:680-5. [DOI: 10.1107/s0907444912007457] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 02/19/2012] [Indexed: 01/28/2023]
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53
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Xue M, Xu M, Lu W, Huang J, Li H, Xu Y, Liu X, Zhao Z. Synthesis, activity evaluation, and docking analysis of barbituric acid aryl hydrazone derivatives as RSK2 inhibitors. J Enzyme Inhib Med Chem 2012; 28:747-52. [DOI: 10.3109/14756366.2012.681651] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Mengzhu Xue
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Minghao Xu
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Weiqiang Lu
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Jin Huang
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Honglin Li
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Yufang Xu
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Xiaofeng Liu
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
| | - Zhenjiang Zhao
- Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology,
Shanghai, China
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Tangredi MM, Ng FS, Jackson FR. The C-terminal kinase and ERK-binding domains of Drosophila S6KII (RSK) are required for phosphorylation of the protein and modulation of circadian behavior. J Biol Chem 2012; 287:16748-58. [PMID: 22447936 DOI: 10.1074/jbc.m111.315929] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A detailed structure/function analysis of Drosophila p90 ribosomal S6 kinase (S6KII) or its mammalian homolog RSK has not been performed in the context of neuronal plasticity or behavior. We previously reported that S6KII is required for normal circadian periodicity. Here we report a site-directed mutagenesis of S6KII and analysis of mutants, in vivo, that identifies functional domains and phosphorylation sites critical for the regulation of circadian period. We demonstrate, for the first time, a role for the S6KII C-terminal kinase that is independent of its known role in activation of the N-terminal kinase. Both S6KII C-terminal kinase activity and its ERK-binding domain are required for wild-type circadian period and normal phosphorylation status of the protein. In contrast, the N-terminal kinase of S6KII is dispensable for modulation of circadian period and normal phosphorylation of the protein. We also show that particular sites of S6KII phosphorylation, Ser-515 and Thr-732, are essential for normal circadian behavior. Surprisingly, the phosphorylation of S6KII residues, in vivo, does not follow a strict sequential pattern, as implied by certain cell-based studies of mammalian RSK protein.
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Affiliation(s)
- Michelle M Tangredi
- Department of Neuroscience, Center for Neuroscience Research, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Abstract
The RSK (90 kDa ribosomal S6 kinase) family comprises a group of highly related serine/threonine kinases that regulate diverse cellular processes, including cell growth, proliferation, survival and motility. This family includes four vertebrate isoforms (RSK1, RSK2, RSK3 and RSK4), and single family member orthologues are also present in Drosophila and Caenorhabditis elegans. The RSK isoforms are downstream effectors of the Ras/ERK (extracellular-signal-regulated kinase) signalling pathway. Significant advances in the field of RSK signalling have occurred in the past few years, including several new functions ascribed to the RSK isoforms, the discovery of novel protein substrates and the implication of different RSK isoforms in cancer. Collectively, these new findings increase the diversity of biological functions regulated by RSK, and highlight potential new directions of research. In the present paper, we review the structure, expression and activation mechanisms of the RSK isoforms, and discuss their physiological roles on the basis of established substrates and recent discoveries.
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Gawecka JE, Geerts D, Koster J, Caliva MJ, Sulzmaier FJ, Opoku-Ansah J, Wada RK, Bachmann AS, Ramos JW. PEA15 impairs cell migration and correlates with clinical features predicting good prognosis in neuroblastoma. Int J Cancer 2012; 131:1556-68. [PMID: 22213050 DOI: 10.1002/ijc.27415] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 12/09/2011] [Indexed: 12/29/2022]
Abstract
ERK and RSK2 drive proliferation and invasion of many cancers. Phosphoprotein enriched in astrocytes 15 (PEA15) binds ERK and RSK2 and high PEA15 levels can impair ERK- and RSK2-dependent transcription. PEA15 expression also inversely correlates with cell motility and invasiveness. We therefore tested PEA15 effects on neuroblastoma cells in vitro. We further analyzed PEA15 expression in the context of clinical and genetic features of neuroblastoma in tumor samples to determine its correlation with disease progression. Affymetrix microarray analysis was performed using 24 different neuroblastoma cell lines. Cell lines expressing low to intermediate levels of PEA15 were chosen for in vitro functional studies. The cell line results were verified by Affymetrix analysis of three different neuroblastic tumor types (total of 110 samples) PEA15 overexpression inhibited neuroblastoma migration in vitro. We verified that inhibition of motility required PEA15 interaction with its binding partners ERK and RSK2. Additionally, synthetic inhibitors of RSK2 suppressed integrin-dependent migration. PEA15 expression correlates with clinical parameters and a 25% increase in patient survival rate. The highest PEA15 levels were found in low stage, more differentiated and less metastatic neuroblastic tumors, and correlated with lack of MYCN amplification. PEA15 blocks neuroblastoma migration through inhibition of ERK/RSK2 signaling. PEA15 expression levels correlate with favorable clinical features suggesting that PEA15 limits metastatic progression of neuroblastoma. Thus, PEA15 and its partners ERK and RSK2 are potential targets for the development of new therapeutics to impede progression of minimal residual disease in patients with high-risk neuroblastoma.
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Affiliation(s)
- Joanna E Gawecka
- Cancer Biology Program, University of Hawai'i Cancer Center, University of Hawai'i at Manoa, Honolulu, HI 96813, USA
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Gao X, Chaturvedi D, Patel TB. Localization and retention of p90 ribosomal S6 kinase 1 in the nucleus: implications for its function. Mol Biol Cell 2011; 23:503-15. [PMID: 22130794 PMCID: PMC3268728 DOI: 10.1091/mbc.e11-07-0658] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ribosomal S6 kinase 1 (RSK1), which plays a critical role in cell survival and proliferation, contains a bipartite nuclear localization sequence that permits its entry into the nucleus. RSK1 is retained in the nucleus via its indirect interactions with AKAP95. Interference with its nuclear entry or retention decreases DNA synthesis. Ribosomal S6 kinase 1 (RSK1) belongs to a family of proteins with two kinase domains. Following activation in the cytoplasm by extracellular signal-regulated kinases (ERK1/2), it mediates the cell-proliferative, cell-growth, and survival-promoting actions of a number of growth factors and other agonists. These diverse biological actions of RSK1 involve regulation of both cytoplasmic and nuclear events. However, the mechanisms that permit nuclear accumulation of RSK1 remain unknown. Here, we show that phosphorylation of RSK1 on S221 is important for its dissociation from the type Iα regulatory subunit of protein kinase A (PKA) in the cytoplasm and that RSK1 contains a bipartite nuclear localization sequence that is necessary for its nuclear entry. Once inside, the active RSK1 is retained in the nucleus via its interactions with PKA catalytic subunit and AKAP95. Mutations of RSK1 that do not affect its activity but disrupt its entry into the nucleus or expression of AKAP95 forms that do not enter the nucleus inhibit the ability of active RSK1 to stimulate DNA synthesis. Our findings identify novel mechanisms by which active RSK1 accumulates in the nucleus and also provide new insights into how AKAP95 orchestrates cell cycle progression.
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Affiliation(s)
- Xianlong Gao
- Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
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58
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Abstract
Studies of epilepsy have mainly focused on the membrane proteins that control neuronal excitability. Recently, attention has been shifting to intracellular proteins and their interactions, signaling cascades and feedback regulation as they relate to epilepsy. The mTOR (mammalian target of rapamycin) signal transduction pathway, especially, has been suggested to play an important role in this regard. These pathways are involved in major physiological processes as well as in numerous pathological conditions. Here, involvement of the mTOR pathway in epilepsy will be reviewed by presenting; an overview of the pathway, a brief description of key signaling molecules, a summary of independent reports and possible implications of abnormalities of those molecules in epilepsy, a discussion of the lack of experimental data, and questions raised for the understanding its epileptogenic mechanism.
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Affiliation(s)
- Chang Hoon Cho
- Epilepsy Research Laboratory Department of Pediatrics Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
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59
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Activation and function of the MAPKs and their substrates, the MAPK-activated protein kinases. Microbiol Mol Biol Rev 2011; 75:50-83. [PMID: 21372320 DOI: 10.1128/mmbr.00031-10] [Citation(s) in RCA: 2150] [Impact Index Per Article: 165.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (α, β, γ, and δ), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries.
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60
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Egervári G, Márk Á, Hajdu M, Barna G, Sápi Z, Krenács T, Kopper L, Sebestyén A. Mitotic lymphoma cells are characterized by high expression of phosphorylated ribosomal S6 protein. Histochem Cell Biol 2011; 135:409-17. [DOI: 10.1007/s00418-011-0803-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/08/2011] [Indexed: 11/30/2022]
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61
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Cargnello M, Roux PP. Activation and Function of the MAPKs and Their Substrates, the MAPK-Activated Protein Kinases. Microbiol Mol Biol Rev 2011. [DOI: 78495111110.1128/mmbr.00031-10' target='_blank'>'"<>78495111110.1128/mmbr.00031-10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [78495111110.1128/mmbr.00031-10','', '10.1074/jbc.274.5.2893')">Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
78495111110.1128/mmbr.00031-10" />
Abstract
SUMMARYThe mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (α, β, γ, and δ), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries.
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Affiliation(s)
- Marie Cargnello
- Institute for Research in Immunology and Cancer, Université de Montréal, Montreal, Quebec, Canada
- Molecular Biology Program, Université de Montréal, Montreal, Quebec, Canada
| | - Philippe P. Roux
- Institute for Research in Immunology and Cancer, Université de Montréal, Montreal, Quebec, Canada
- Molecular Biology Program, Université de Montréal, Montreal, Quebec, Canada
- Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montreal, Quebec, Canada
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62
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Kroczynska B, Joshi S, Eklund EA, Verma A, Kotenko SV, Fish EN, Platanias LC. Regulatory effects of ribosomal S6 kinase 1 (RSK1) in IFNλ signaling. J Biol Chem 2011; 286:1147-56. [PMID: 21075852 PMCID: PMC3020721 DOI: 10.1074/jbc.m110.183566] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 11/12/2010] [Indexed: 01/11/2023] Open
Abstract
Although the mechanisms of generation of signals that control transcriptional activation of Type III IFN (IFNλ)-regulated genes have been identified, very little is known about the mechanisms by which the IFNλ receptor generates signals for mRNA translation of IFNλ-activated genes. We provide evidence that IFNλ activates the p90 ribosomal protein S6 kinase 1 (RSK1) and its downstream effector, initiation factor eIF4B. Prior to its engagement by the IFNλ receptor, the non-active form of RSK1 is present in a complex with the translational repressor 4E-BP1 in IFNλ-sensitive cells. IFNλ-inducible phosphorylation/activation of RSK1 results in its dissociation from 4E-BP1 at the same time that 4E-BP1 dissociates from eIF4E to allow formation of eIF4F and initiation of cap-dependent translation. Our studies demonstrate that such IFNλ-dependent engagement of RSK1 is essential for up-regulation of p21(WAF1/CIP1) expression, suggesting a mechanism for generation of growth-inhibitory responses. Altogether, our data provide evidence for a critical role for the activated RSK1 in IFNλ signaling.
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Affiliation(s)
- Barbara Kroczynska
- From the Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60611
| | - Sonali Joshi
- From the Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60611
| | - Elizabeth A. Eklund
- From the Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60611
| | - Amit Verma
- the Division of Hematology-Oncology, the Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Sergei V. Kotenko
- the Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103
| | - Eleanor N. Fish
- the Division of Cell and Molecular Biology, Toronto Research Institute, University Health Network and Department of Immunology, University of Toronto, Toronto M5G 2M1, Ontario, Canada, and
| | - Leonidas C. Platanias
- From the Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60611
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63
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Burkhard KA, Chen F, Shapiro P. Quantitative analysis of ERK2 interactions with substrate proteins: roles for kinase docking domains and activity in determining binding affinity. J Biol Chem 2010; 286:2477-85. [PMID: 21098038 DOI: 10.1074/jbc.m110.177899] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Extracellular signal-regulated kinase-1 and -2 (ERK1/2) proteins regulate a variety of cellular functions, including cell proliferation and differentiation, by interacting with and phosphorylating substrate proteins. Two docking sites, common docking (CD/ED) domain and F-site recruitment site (FRS), on ERK proteins have been identified. Specific interactions with the CD/ED domain and the FRS occur with substrates containing a docking site for ERK and JNK, LXL (DEJL) motif (D-domain) and a docking site for ERK, FXF (DEF) motif (F-site), respectively. However, the relative contributions of the ERK docking sites in mediating substrate interactions that allow efficient phosphate transfer are largely unknown. In these studies, we provide a quantitative analysis of ERK2 interactions with substrates using surface plasmon resonance to measure real time protein-protein interactions. ERK2 interacted with ELK-1 (DEF and DEJL motifs), RSK-1 (DEJL motif), and c-Fos (DEF motif) with K(D) values of 0.25, 0.15, and 0.97 μM, respectively. CD/ED domain mutations inhibited interactions with ELK-1 and RSK-1 by 6-fold but had no effect on interactions with c-Fos. Select mutations in FRS residues differentially inhibited ELK-1 or c-Fos interactions with ERK2 but had little effect on RSK-1 interactions. Mutations in both the ED and FRS docking sites completely inhibited ELK-1 interactions but had no effect on interactions with stathmin, an ERK substrate whose docking site is unknown. The phosphorylation status of ERK2 did not affect interactions with RSK-1 or c-Fos but did inhibit interactions with ELK-1 and stathmin. These studies provide a quantitative evaluation of specific docking domains involved in mediating interactions between ERK2 and protein substrates and define the contributions of these interactions to phosphate transfer.
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Affiliation(s)
- Kimberly A Burkhard
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, USA
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Abstract
IMPORTANCE OF THE FIELD p90 ribosomal S6 kinase 2 (RSK2) belongs to a Ser/Thr kinase family containing four members, RSK1 - 4, which play an essential role in a number of cellular functions including cell cycle, survival and proliferation. Recent advances reveal a crucial role of RSK2 in oncogenesis and tumor progression, making RSK2 an attractive therapeutic target for cancer treatment. AREA COVERED IN THIS REVIEW Recent findings identifying the role of RSK2 in human cancers, including hematopoietic malignancies and solid tumors. Therapeutic implications of targeting RSK2 are also discussed with regard to clinical circumstance. WHAT THE READER WILL GAIN A better understanding of molecular mechanisms underlying RSK2 activation and its contribution to human cancers and also insight into the development of novel targeted cancer therapy. TAKE HOME MESSAGE The significance of RSK2 in cancer cell survival, proliferation, invasion and tumor metastasis varies amongst human malignancies and depends on the signaling properties of the oncogenes and cellular microenvironment of the transformed cells. Thus, further exploitation of RSK2 signaling and its dynamic interaction with other crucial oncogenic and pro-metastatic pathways in different human malignancies is needed for more effective therapeutic interventions.
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Affiliation(s)
- Sumin Kang
- Emory University School of Medicine, Winship Cancer Institute of Emory, Department of Hematology and Medical Oncology, Atlanta, GA 30322, USA. ;
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Chandrakesan P, Ahmed I, Anwar T, Wang Y, Sarkar S, Singh P, Peleg S, Umar S. Novel changes in NF-{kappa}B activity during progression and regression phases of hyperplasia: role of MEK, ERK, and p38. J Biol Chem 2010; 285:33485-33498. [PMID: 20710027 DOI: 10.1074/jbc.m110.129353] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Utilizing the Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model, we measured hyperplasia and NF-κB activation during progression (days 6 and 12 post-infection) and regression (days 20-34 post-infection) phases of TMCH. NF-κB activity increased at progression in conjunction with bacterial attachment and translocation to the colonic crypts and decreased 40% by day 20. NF-κB activity at days 27 and 34, however, remained 2-3-fold higher than uninfected control. Expression of the downstream target gene CXCL-1/KC in the crypts correlated with NF-κB activation kinetics. Phosphorylation of cellular IκBα kinase (IKK)α/β (Ser(176/180)) was elevated during progression and regression of TMCH. Phosphorylation (Ser(32/36)) and degradation of IκBα, however, contributed to NF-κB activation only from days 6 to 20 but not at later time points. Phosphorylation of MEK1/2 (Ser(217/221)), ERK1/2 (Thr(202)/Tyr(204)), and p38 (Thr(180)/Tyr(182)) paralleled IKKα/β kinetics at days 6 and 12 without declining with regressing hyperplasia. siRNAs to MEK, ERK, and p38 significantly blocked NF-κB activity in vitro, whereas MEK1/2-inhibitor (PD98059) also blocked increases in MEK1/2, ERK1/2, and IKKα/β thereby inhibiting NF-κB activity in vivo. Cellular and nuclear levels of Ser(536)-phosphorylated (p65(536)) and Lys(310)-acetylated p65 subunit accompanied functional NF-κB activation during TMCH. RSK-1 phosphorylation at Thr(359)/Ser(363) in cellular/nuclear extracts and co-immunoprecipitation with cellular p65-NF-κB overlapped with p65(536) kinetics. Dietary pectin (6%) blocked NF-κB activity by blocking increases in p65 abundance and nuclear translocation thereby down-regulating CXCL-1/KC expression in the crypts. Thus, NF-κB activation persisted despite the lack of bacterial attachment to colonic mucosa beyond peak hyperplasia. The MEK/ERK/p38 pathway therefore seems to modulate sustained activation of NF-κB in colonic crypts in response to C. rodentium infection.
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Affiliation(s)
- Parthasarathy Chandrakesan
- From the Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Ishfaq Ahmed
- From the Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Tariq Anwar
- Centre for Molecular Biosciences, University of Ulster, BT52 1SA Coleraine, United Kingdom
| | - Yu Wang
- Departments of Internal Medicine, Galveston, Texas 77555
| | - Shubhashish Sarkar
- Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Pomila Singh
- Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555
| | - Sara Peleg
- Department of Endocrine Neoplasia and Hormone Disorder Research, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Shahid Umar
- From the Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
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Pérez-Pérez A, Gambino Y, Maymó J, Goberna R, Fabiani F, Varone C, Sánchez-Margalet V. MAPK and PI3K activities are required for leptin stimulation of protein synthesis in human trophoblastic cells. Biochem Biophys Res Commun 2010; 396:956-60. [DOI: 10.1016/j.bbrc.2010.05.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 05/06/2010] [Indexed: 11/28/2022]
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Peng C, Cho YY, Zhu F, Xu YM, Wen W, Ma WY, Bode AM, Dong Z. RSK2 mediates NF-{kappa}B activity through the phosphorylation of IkappaBalpha in the TNF-R1 pathway. FASEB J 2010; 24:3490-9. [PMID: 20385620 DOI: 10.1096/fj.09-151290] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The ribosomal S6 kinase 2 (RSK2) is a well-known serine/threonine kinase and a member of the p90 ribosomal S6 kinase (p90RSK) family of proteins. It is activated downstream of the MEK/ERKs cascade by mitogenic stimuli such as EGF or TPA. Here, we show that RSK2 is activated by treatment with tumor necrosis factor-alpha (TNF-alpha) and directly phosphorylates IkappaBalpha at Ser-32, leading to IkappaBalpha degradation. The phosphorylation of IkappaBalpha promotes the activation and translocation of the nuclear factor-kappaB (NF-kappaB) subunits p65 and p50 to the nucleus. The net result is an increased NF-kappaB activity, which serves as a mechanism for RSK2 blockade of TNF-alpha-induced apoptosis and enhanced cell survival.
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Affiliation(s)
- Cong Peng
- The Hormel Institute, University of Minnesota, 801 16th Ave N.E., Austin, MN 55912, USA
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Xylourgidis N, Fornerod M. Acting out of character: regulatory roles of nuclear pore complex proteins. Dev Cell 2009; 17:617-25. [PMID: 19922867 DOI: 10.1016/j.devcel.2009.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nuclear pore complexes (NPCs) mediate all selective bidirectional transport between the nucleus and the cytoplasm. Additional functions for NPCs and their constituent proteins (nucleoporins) are emerging, some independent of classical transport. Specifically, enzymatic activities at the NPC regulate nucleocytoplasmic transport and use the NPC as a regulatory scaffold. Also, nucleoporins may regulate gene expression by contacting chromatin. Discriminating between effects on transport, scaffolding, and gene expression is a major challenge in understanding the role of the NPC in signaling and development.
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Affiliation(s)
- Nikos Xylourgidis
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands
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70
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Pan C, Olsen JV, Daub H, Mann M. Global effects of kinase inhibitors on signaling networks revealed by quantitative phosphoproteomics. Mol Cell Proteomics 2009; 8:2796-808. [PMID: 19651622 PMCID: PMC2816010 DOI: 10.1074/mcp.m900285-mcp200] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 07/29/2009] [Indexed: 01/14/2023] Open
Abstract
Aberrant signaling causes many diseases, and manipulating signaling pathways with kinase inhibitors has emerged as a promising area of drug research. Most kinase inhibitors target the conserved ATP-binding pocket; therefore specificity is a major concern. Proteomics has previously been used to identify the direct targets of kinase inhibitors upon affinity purification from cellular extracts. Here we introduce a complementary approach to evaluate the effects of kinase inhibitors on the entire cell signaling network. We used triple labeling SILAC (stable isotope labeling by amino acids in cell culture) to compare cellular phosphorylation levels for control, epidermal growth factor stimulus, and growth factor combined with kinase inhibitors. Of thousands of phosphopeptides, less than 10% had a response pattern indicative of targets of U0126 and SB202190, two widely used MAPK inhibitors. Interestingly, 83% of the growth factor-induced phosphorylation events were affected by either or both inhibitors, showing quantitatively that early signaling processes are predominantly transmitted through the MAPK cascades. In contrast to MAPK inhibitors, dasatinib, a clinical drug directed against BCR-ABL, which is the cause of chronic myelogenous leukemia, affected nearly 1,000 phosphopeptides. In addition to the proximal effects on ABL and its immediate targets, dasatinib broadly affected the downstream MAPK pathways. Pathway mapping of regulated sites implicated a variety of cellular functions, such as chromosome remodeling, RNA splicing, and cytoskeletal organization, some of which have been described in the literature before. Our assay is streamlined and generic and could become a useful tool in kinase drug development.
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Affiliation(s)
- Cuiping Pan
- From the Departments of ‡Proteomics and Signal Transduction and
| | - Jesper V. Olsen
- From the Departments of ‡Proteomics and Signal Transduction and
- §Department of Proteomics, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Henrik Daub
- ¶Molecular Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18, D-82152 Martinsried near Munich, Germany and
| | - Matthias Mann
- From the Departments of ‡Proteomics and Signal Transduction and
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71
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Structural diversity of the active N-terminal kinase domain of p90 ribosomal S6 kinase 2. PLoS One 2009; 4:e8044. [PMID: 19956600 PMCID: PMC2779450 DOI: 10.1371/journal.pone.0008044] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 10/19/2009] [Indexed: 11/19/2022] Open
Abstract
The p90 ribosomal protein kinase 2 (RSK2) is a highly expressed Ser/Thr kinase activated by growth factors and is involved in cancer cell proliferation and tumor promoter-induced cell transformation. RSK2 possesses two non-identical kinase domains, and the structure of its N-terminal domain (NTD), which is responsible for phosphorylation of a variety of substrates, is unknown. The crystal structure of the NTD RSK2 was determined at 1.8 Å resolution in complex with AMP-PNP. The N-terminal kinase domain adopted a unique active conformation showing a significant structural diversity of the kinase domain compared to other kinases. The NTD RSK2 possesses a three-stranded βB-sheet inserted in the N-terminal lobe, resulting in displacement of the αC-helix and disruption of the Lys-Glu interaction, classifying the kinase conformation as inactive. The purified protein was phosphorylated at Ser227 in the T-activation loop and exhibited in vitro kinase activity. A key characteristic is the appearance of a new contact between Lys216 (βB-sheet) and the β-phosphate of AMP-PNP. Mutation of this lysine to alanine impaired both NTDs in vitro and full length RSK2 ex vivo activity, emphasizing the importance of this interaction. Even though the N-terminal lobe undergoes structural re-arrangement, it possesses an intact hydrophobic groove formed between the αC-helix, the β4-strand, and the βB-sheet junction, which is occupied by the N-terminal tail. The presence of a unique βB-sheet insert in the N-lobe suggests a different type of activation mechanism for RSK2.
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72
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Burkhard K, Smith S, Deshmukh R, MacKerell AD, Shapiro P. Development of extracellular signal-regulated kinase inhibitors. Curr Top Med Chem 2009; 9:678-89. [PMID: 19689374 DOI: 10.2174/156802609789044416] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Activation of the extracellular signal-regulated kinase (ERK) signaling pathway has been implicated in mediating a diverse array of cellular functions including cell differentiation, proliferation, and inflammatory responses. In this review, we will discuss approaches to identify inhibitors of ERK proteins through targeting ATP-dependent and ATP-independent mechanisms. Given the diversity of ERK substrates and the importance of ERK signaling in normal cell functions, emphasis will be placed on the methods for identifying small molecular weight compounds that are substrate selective through ATP-independent interactions and potentially relevant to inflammatory processes. The approach for selective targeting of ERK substrates takes advantage of the basic understanding of unique ERK docking domains that are thought to interact with specific amino acid sequences on substrate proteins. Computer aided drug design (CADD) can facilitate the high throughput screening of millions of compounds with the potential for selective interactions with ERK docking domains and disruption of substrate interactions. As such, the CADD approach significantly reduces the number of compounds that will be evaluated in subsequent biological assays and greatly increases the hit rate of biologically active compounds. The potentially active compounds are evaluated for ERK protein binding using spectroscopic and structural biology methods. Compounds that show ERK interactions are then tested for their ability to inhibit substrate interactions and phosphorylation as well as ERK-dependent functions in whole organism or cell-based assays. Finally, the relevance of substrate-selective ERK inhibitors in the context of inflammatory disease will be discussed.
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Affiliation(s)
- Kimberly Burkhard
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
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73
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Abstract
Severe acute respiratory syndrome (SARS) is a respiratory illness with variable symptoms that was recognized as the first near-pandemic infectious disease of the twenty-first century. A novel human coronavirus, named SARS coronavirus (SARS-CoV), derived from SARS patients was reported as the etiologic agent of SARS. Studying the signaling pathways of SARS-infected cells is key to understanding the molecular mechanism of SARS viral infection. Cell death is observed in cultured Vero E6 cells after SARS-CoV infection. From SARS-CoV infection to cell death, p38 mitogen-activated protein kinase (MAPK) is a key participant in the determination of cell death and survival. Two signaling pathways comprising signal transducer and activator of transcription 3 (STAT3) and p90 ribosomal S6 kinase (p90RSK) are downstream of p38 MAPK. AKT and JNK (Jun NH2-terminal kinase) signaling pathways are important to establish persistent infection of SARS-CoV in Vero E6 cells. Expression studies of SARS-CoV proteins indicate that the viral proteins are able to activate signaling pathways of host cells. The study of signaling pathways in SARS-CoV patients is difficult to perform compared with in vitro studies due to the effects of the human immune system. This review highlights recent progress in characterizing signal transduction pathways in SARS-CoV-infected cells in vitro and in vivo.
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74
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Gao X, Patel TB. Regulation of protein kinase A activity by p90 ribosomal S6 kinase 1. J Biol Chem 2009; 284:33070-8. [PMID: 19808666 DOI: 10.1074/jbc.m109.058453] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we reported that the catalytic subunit of cAMP-dependent protein kinase (PKAc) binds to the active p90 ribosomal S6 kinase 1 (RSK1) (Chaturvedi, D., Poppleton, H. M., Stringfield, T., Barbier, A., and Patel, T. B. (2006) Mol. Cell. Biol. 26, 4586-4600). Herein, by overexpressing hemagglutinin-tagged RSK1 fragments in HeLa cells we have identified the region of RSK1 that is responsible for the interaction with PKAc. PKAc bound to the last 13 amino acids of RSK1, which overlaps the Erk1/2 docking site. This interaction between PKAc and RSK1 required the phosphorylation of Ser-732 in the C terminus of RSK1. Depending upon its phosphorylation status, RSK1 switched interactions between Erk1/2 and PKAc. In addition, a peptide corresponding to the last 13 amino acids of RSK1 with substitution of Ser-732 with Glu (peptide E), but not Ala (peptide A), decreased interactions between endogenous active RSK1 and PKAc. RSK1 attenuated the ability of cAMP to activate PKA in vitro and this modulation was abrogated by peptide E, but not by peptide A. Similarly, in intact cells, cAMP-mediated phosphorylation of Bcl-xL/Bcl-2-associated death promoter on Ser-115, the PKA site, was reduced when RSK1 was activated by epidermal growth factor, and this effect was blocked by peptide E, but not by peptide A. These findings demonstrate that interactions between endogenous RSK1 and PKAc in intact cells regulate the ability of cAMP to activate PKA and identify a novel mechanism by which PKA activity is regulated by the Erk1/2 pathway.
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Affiliation(s)
- Xianlong Gao
- Department of Pharmacology and Experimental Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153, USA
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75
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Extracellular signal-regulated kinase 1 (ERK1) and ERK2 play essential roles in osteoblast differentiation and in supporting osteoclastogenesis. Mol Cell Biol 2009; 29:5843-57. [PMID: 19737917 DOI: 10.1128/mcb.01549-08] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Osteoblasts and chondrocytes arise from common osteo-chondroprogenitor cells. We show here that inactivation of ERK1 and ERK2 in osteo-chondroprogenitor cells causes a block in osteoblast differentiation and leads to ectopic chondrogenic differentiation in the bone-forming region in the perichondrium. Furthermore, increased mitogen-activated protein kinase signaling in mesenchymal cells enhances osteoblast differentiation and inhibits chondrocyte differentiation. These observations indicate that extracellular signal-regulated kinase 1 (ERK1) and ERK2 play essential roles in the lineage specification of mesenchymal cells. The inactivation of ERK1 and ERK2 resulted in reduced beta-catenin expression, suggesting a role for canonical Wnt signaling in ERK1 and ERK2 regulation of skeletal lineage specification. Furthermore, inactivation of ERK1 and ERK2 significantly reduced RANKL expression, accounting for a delay in osteoclast formation. Thus, our results indicate that ERK1 and ERK2 not only play essential roles in the lineage specification of osteo-chondroprogenitor cells but also support osteoclast formation in vivo.
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76
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Chaturvedi D, Cohen MS, Taunton J, Patel TB. The PKARIalpha subunit of protein kinase A modulates the activation of p90RSK1 and its function. J Biol Chem 2009; 284:23670-81. [PMID: 19570980 DOI: 10.1074/jbc.m109.032813] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we showed that interactions between p90(RSK1) (RSK1) and the subunits of type I protein kinase A (PKA) regulate the activity of PKA and cellular distribution of active RSK1 (Chaturvedi, D., Poppleton, H. M., Stringfield, T., Barbier, A., and Patel, T. B. (2006) Mol. Cell Biol. 26, 4586-4600). Here we examined the role of the PKARIalpha subunit of PKA in regulating RSK1 activation and cell survival. In mouse lung fibroblasts, silencing of the PKARIalpha increased the phosphorylation and activation of RSK1, but not of RSK2 and RSK3, in the absence of any stimulation. Silencing of PKARIalpha also decreased the nuclear accumulation of active RSK1 and increased its cytoplasmic content. The increased activation of RSK1 in the absence of any agonist and changes in its subcellular redistribution resulted in increased phosphorylation of its cytoplasmic substrate BAD and increased cell survival. The activity of PKA and phosphorylation of BAD (Ser-155) were also enhanced when PKARIalpha was silenced, and this, in part, contributed to increased cell survival in unstimulated cells. Furthermore, we show that RSK1, PKA subunits, D-AKAP1, and protein phosphatase 2A catalytic subunit (PP2Ac) exist in a complex, and dissociation of RSK1 from D-AKAP1 by either silencing of PKARIalpha, depletion of D-AKAP1, or by using a peptide that competes with PKARIalpha for binding to AKAPs, decreased the amount of PP2Ac in the RSK1 complex. We also demonstrate that PP2Ac is one of the phosphatases that dephosphorylates RSK, but not ERK1/2. Thus, in unstimulated cells, the increased phosphorylation and activation of RSK1 after silencing of PKARIalpha or depletion of D-AKAP1 are due to decreased association of PP2Ac in the RSK1 complex.
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Affiliation(s)
- Deepti Chaturvedi
- Department of Pharmacology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153, USA
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77
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Pérez-Pérez A, Maymó J, Gambino Y, Dueñas JL, Goberna R, Varone C, Sánchez-Margalet V. Leptin stimulates protein synthesis-activating translation machinery in human trophoblastic cells. Biol Reprod 2009; 81:826-32. [PMID: 19553602 DOI: 10.1095/biolreprod.109.076513] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Leptin was originally considered as an adipocyte-derived signaling molecule for the central control of metabolism. However, pleiotropic effects of leptin have been identified in reproduction and pregnancy, particularly in placenta, where it may work as an autocrine hormone, mediating angiogenesis, growth, and immunomodulation. Leptin receptor (LEPR, also known as Ob-R) shows sequence homology to members of the class I cytokine receptor (gp130) superfamily. In fact, leptin may function as a proinflammatory cytokine. We have previously found that leptin is a trophic and mitogenic factor for trophoblastic cells. In order to further investigate the mechanism by which leptin stimulates cell growth in JEG-3 cells and trophoblastic cells, we studied the phosphorylation state of different proteins of the initiation stage of translation and the total protein synthesis by [(3)H]leucine incorporation in JEG-3 cells. We have found that leptin dose-dependently stimulates the phosphorylation and activation of the translation initiation factor EIF4E as well as the phosphorylation of the EIF4E binding protein EIF4EBP1 (PHAS-I), which releases EIF4E to form active complexes. Moreover, leptin dose-dependently stimulates protein synthesis, and this effect can be partially prevented by blocking mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PIK3) pathways. In conclusion, leptin stimulates protein synthesis, at least in part activating the translation machinery, via the activation of MAPK and PIK3 pathways.
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Affiliation(s)
- Antonio Pérez-Pérez
- Departamento de Bioquímica Médica y Biología Molecular, Hospital Universitario Virgen Macarena, Universidad de Sevilla, Seville, Spain
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78
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Kuang E, Wu F, Zhu F. Mechanism of sustained activation of ribosomal S6 kinase (RSK) and ERK by kaposi sarcoma-associated herpesvirus ORF45: multiprotein complexes retain active phosphorylated ERK AND RSK and protect them from dephosphorylation. J Biol Chem 2009; 284:13958-13968. [PMID: 19304659 DOI: 10.1074/jbc.m900025200] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
As obligate intracellular parasites, viruses exploit diverse cellular signaling machineries, including the mitogen-activated protein-kinase pathway, during their infections. We have demonstrated previously that the open reading frame 45 (ORF45) of Kaposi sarcoma-associated herpesvirus interacts with p90 ribosomal S6 kinases (RSKs) and strongly stimulates their kinase activities ( Kuang, E., Tang, Q., Maul, G. G., and Zhu, F. (2008) J. Virol. 82, 1838-1850 ). Here, we define the mechanism by which ORF45 activates RSKs. We demonstrated that binding of ORF45 to RSK increases the association of extracellular signal-regulated kinase (ERK) with RSK, such that ORF45, RSK, and ERK formed high molecular mass protein complexes. We further demonstrated that the complexes shielded active pERK and pRSK from dephosphorylation. As a result, the complex-associated RSK and ERK were activated and sustained at high levels. Finally, we provide evidence that this mechanism contributes to the sustained activation of ERK and RSK in Kaposi sarcoma-associated herpesvirus lytic replication.
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Affiliation(s)
- Ersheng Kuang
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4370
| | - Fayi Wu
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4370
| | - Fanxiu Zhu
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4370.
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79
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Multiple ERK substrates execute single biological processes in Caenorhabditis elegans germ-line development. Proc Natl Acad Sci U S A 2009; 106:4776-81. [PMID: 19264959 DOI: 10.1073/pnas.0812285106] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RAS-extracellular signal regulated kinase (ERK) signaling governs multiple aspects of cell fate specification, cellular transitions, and growth by regulating downstream substrates through phosphorylation. Understanding how perturbations to the ERK signaling pathway lead to developmental disorders and cancer hinges critically on identification of the substrates. Yet, only a limited number of substrates have been identified that function in vivo to execute ERK-regulated processes. The Caenorhabditis elegans germ line utilizes the well-conserved RAS-ERK signaling pathway in multiple different contexts. Here, we present an integrated functional genomic approach that identified 30 ERK substrates, each of which functions to regulate one or more of seven distinct biological processes during C. elegans germ-line development. Our results provide evidence for three themes that underlie the robustness and specificity of biological outcomes controlled by ERK signaling in C. elegans that are likely relevant to ERK signaling in other organisms: (i) multiple diverse ERK substrates function to control each individual biological process; (ii) different combinations of substrates function to control distinct biological processes; and (iii) regulatory feedback loops between ERK and its substrates help reinforce or attenuate ERK activation. Substrates identified here have conserved orthologs in humans, suggesting that insights from these studies will contribute to our understanding of human diseases involving deregulated ERK activity.
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80
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Fibroblast growth factor receptor 3 associates with and tyrosine phosphorylates p90 RSK2, leading to RSK2 activation that mediates hematopoietic transformation. Mol Cell Biol 2009; 29:2105-17. [PMID: 19223461 DOI: 10.1128/mcb.00998-08] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dysregulation of the receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) plays a pathogenic role in a number of human hematopoietic malignancies and solid tumors. These include t(4;14) multiple myeloma associated with ectopic expression of FGFR3 and t(4;12)(p16;p13) acute myeloid leukemia associated with expression of a constitutively activated fusion tyrosine kinase, TEL-FGFR3. We recently reported that FGFR3 directly tyrosine phosphorylates RSK2 at Y529, which consequently regulates RSK2 activation. Here we identified Y707 as an additional tyrosine in RSK2 that is phosphorylated by FGFR3. Phosphorylation at Y707 contributes to RSK2 activation, through a putative disruption of the autoinhibitory alphaL-helix on the C terminus of RSK2, unlike Y529 phosphorylation, which facilitates ERK binding. Moreover, we found that FGFR3 interacts with RSK2 through residue W332 in the linker region of RSK2 and that this association is required for FGFR3-dependent phosphorylation of RSK2 at Y529 and Y707, as well as the subsequent RSK2 activation. Furthermore, in a murine bone marrow transplant assay, genetic deficiency in RSK2 resulted in a significantly delayed and attenuated myeloproliferative syndrome induced by TEL-FGFR3 as compared with wild-type cells, suggesting a critical role of RSK2 in FGFR3-induced hematopoietic transformation. Our current and previous findings represent a paradigm for tyrosine phosphorylation-dependent regulation of serine-threonine kinases.
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81
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Brami-Cherrier K, Roze E, Girault JA, Betuing S, Caboche J. Role of the ERK/MSK1 signalling pathway in chromatin remodelling and brain responses to drugs of abuse. J Neurochem 2009; 108:1323-35. [PMID: 19183268 DOI: 10.1111/j.1471-4159.2009.05879.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Drugs of abuse induce neuroadaptations through regulation of gene expression. Although much attention has focused on transcription factor activities, new concepts have recently emerged on the role of chromatin remodelling as a prerequisite for regulation of gene expression in neurons. Thus, for transcription to occur, chromatin must be decondensed, a dynamic process that depends on post-translational modifications of histones. We review here these modifications with a particular emphasis on the role of histone H3 phosphorylation at the promoter of specific genes, including c-fos and c-jun. We trace the signalling pathways involved in H3 phosphorylation and provide evidence for a role of mitogen and stress-activated protein kinase-1 (MSK1) downstream from the MAPK/extracellular-signal regulated kinase (ERK) cascade. In response to cocaine, MSK1 controls an early phase of histone H3 phosphorylation at the c-fos promoter in striatal neurons. MSK1 action may be potentiated by the concomitant inhibition of protein phosphatase 1 by nuclear translocation of dopamine- and cAMP-regulated phosphoprotein Mr = 32 000. H3 phosphorylation by MSK1 is critically involved in c-fos transcription, and cocaine-induced locomotor sensitization. Thus, ERK plays a dual role in gene regulation and drug addiction by direct activation of transcription factors and by chromatin remodelling.
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Affiliation(s)
- Karen Brami-Cherrier
- UMR 7102, CNRS, Laboratoire de Neurobiologie des Processus Adaptatifs, [corrected] Université Pierre et Marie Curie-Paris-6, Paris, France
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82
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Marques Pereira P, Gruss M, Braun K, Foos N, Pannetier S, Hanauer A. Dopaminergic system dysregulation in themrsk2_KO mouse, an animal model of the Coffin-Lowry syndrome. J Neurochem 2008; 107:1325-34. [DOI: 10.1111/j.1471-4159.2008.05703.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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83
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Anjum R, Blenis J. The RSK family of kinases: emerging roles in cellular signalling. Nat Rev Mol Cell Biol 2008; 9:747-58. [PMID: 18813292 DOI: 10.1038/nrm2509] [Citation(s) in RCA: 570] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The 90 kDa ribosomal S6 kinase (RSK) family of proteins is a group of highly conserved Ser/Thr kinases that regulate diverse cellular processes, such as cell growth, cell motility, cell survival and cell proliferation. RSKs are downstream effectors of the Ras-extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) signalling cascade. Significant advances in the field of RSK and ERK/MAPK signalling have occurred in the past few years, including biological insights and the discovery of novel substrates and new RSK regulatory mechanisms. Collectively, these data expand the current models of RSK signalling and highlight potential directions of research in RSK-mediated survival, growth, proliferation and migration.
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Affiliation(s)
- Rana Anjum
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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84
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Eisinger-Mathason TSK, Andrade J, Groehler AL, Clark DE, Muratore-Schroeder TL, Pasic L, Smith JA, Shabanowitz J, Hunt DF, Macara IG, Lannigan DA. Codependent functions of RSK2 and the apoptosis-promoting factor TIA-1 in stress granule assembly and cell survival. Mol Cell 2008; 31:722-36. [PMID: 18775331 DOI: 10.1016/j.molcel.2008.06.025] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 02/21/2008] [Accepted: 06/06/2008] [Indexed: 10/21/2022]
Abstract
Stress granules aid cell survival in response to environmental stressors by acting as sites of translational repression. We report an unanticipated link between stress granules and the serine/threonine kinase RSK2. In stressed breast cells, endogenous RSK2 colocalizes in granules with TIA-1 and poly(A)-binding protein 1, and the sequestration of RSK2 and TIA-1 exhibits codependency. The RSK2 N-terminal kinase domain controls the direct interaction with the prion-related domain of TIA-1. Silencing RSK2 decreases cell survival in response to stress. Mitogen releases RSK2 from the stress granules and permits its nuclear import via a nucleocytoplasmic shuttling sequence in the C-terminal domain. Nuclear accumulation is dependent on TIA-1. Surprisingly, nuclear localization of RSK2 is sufficient to enhance proliferation through induction of cyclin D1, in the absence of other active signaling pathways. Hence, RSK2 is a pivotal factor linking the stress response to survival and proliferation.
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85
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Cao X, Tanis KQ, Koleske AJ, Colicelli J. Enhancement of ABL kinase catalytic efficiency by a direct binding regulator is independent of other regulatory mechanisms. J Biol Chem 2008; 283:31401-7. [PMID: 18796434 DOI: 10.1074/jbc.m804002200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
ABL family tyrosine kinases are tightly regulated by autoinhibition and phosphorylation mechanisms. These kinases maintain an inactive conformation through intramolecular interactions involving SH3 and SH2 domains. RIN1, a downstream effector of RAS, binds to the ABL SH3 and SH2 domains and stimulates ABL tyrosine kinase activity. RIN1 binding to the ABL2 kinase resulted in a large decrease in Km and a small increase in Vmax toward an ABL consensus substrate peptide. The enzyme efficiency (k(cat)/Km) was increased more than 5-fold by RIN1. In addition, RIN1 strongly enhanced ABL-mediated phosphorylation of CRK, PSTPIP1, and DOK1, all established ABL substrates but with unique protein structures and distinct target sequences. Importantly RIN1-mediated stimulation of ABL kinase activity was independent of activation by SRC-mediated phosphorylation. RIN1 increased the kinase activity of both ABL1 and ABL2, and this occurred in the presence or absence of ABL regulatory domains outside the SH3-SH2-tyrosine kinase domain core. We further demonstrate that a catalytic site mutation associated with broad drug resistance, ABL1T315I, remains responsive to stimulation by RIN1. These findings are consistent with an allosteric kinase activation mechanism by which RIN1 binding promotes a more accessible ABL catalytic site through relief of autoinhibition. Direct disruption of RIN1 binding may therefore be a useful strategy to suppress the activity of normal and oncogenic ABL, including inhibitor-resistant mutants that confound current therapeutic strategies. Stimulation through derepression may be applicable to many other tyrosine kinases autoinhibited by coupled SH3 and SH2 domains.
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Affiliation(s)
- Xiaoqing Cao
- Department of Biological Chemistry, Molecular Biology Institute, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA
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86
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Extracellular signal-regulated kinase 2 (ERK2) phosphorylation sites and docking domain on the nuclear pore complex protein Tpr cooperatively regulate ERK2-Tpr interaction. Mol Cell Biol 2008; 28:6954-66. [PMID: 18794356 DOI: 10.1128/mcb.00925-08] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Identifying direct substrates of mitogen-activated protein kinases (MAPKs) and understanding how those substrates are selected is central to understanding how these ubiquitously activated enzymes generate diverse biological responses. In previous work, we identified several new candidate substrates for the MAPK ERK2 (extracellular signal-regulated kinase 2), including the nuclear pore complex protein Tpr (translocated promoter region). In this report, we identify sites on Tpr for ERK2 phosphorylation and binding and demonstrate their functional interaction. ERK2 phosphorylation and dimerization are necessary for ERK2-Tpr binding, and this occurs through a DEF (docking site for ERK2, FXF) domain on Tpr. Surprisingly, the DEF domain and the phosphorylation sites displayed positive cooperativity to promote ERK2 binding to Tpr, in contrast to substrates where phosphorylation reduces binding. Ectopic expression or depletion of Tpr resulted in decreased movement of activated ERK2 from the cytoplasm to the nucleus, implying a role for Tpr in ERK2 translocation. Collectively, the data provide direct evidence that a component of the nuclear pore complex is a bona fide substrate of ERK2 in vivo and that activated ERK2 stably associates with this substrate after phosphorylation, where it could play a continuing role in nuclear pore function. We propose that Tpr is both a substrate and a scaffold for activated ERKs.
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87
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Lu Z, Abe JI, Taunton J, Lu Y, Shishido T, McClain C, Yan C, Xu SP, Spangenberg TM, Xu H. Reactive oxygen species-induced activation of p90 ribosomal S6 kinase prolongs cardiac repolarization through inhibiting outward K+ channel activity. Circ Res 2008; 103:269-78. [PMID: 18599872 DOI: 10.1161/circresaha.107.166678] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
p90 ribosomal S6 kinase (p90RSK) is activated in cardiomyopathies caused by conditions such as ischemia/reperfusion injury and diabetes mellitus in which prolongation of cardiac repolarization and frequent arrhythmias are common. Molecular mechanisms underlying the electric remodeling in cardiac diseases are largely unknown. In the present study, we determined the role of p90RSK activation in the modulation of voltage-gated K+ channel activity determining cardiac repolarization. Mice with increased cardiac p90RSK activity due to transgenic expression of p90RSK (p90RSK-Tg) had prolongation of QT intervals and of ventricular myocyte action potential durations. Fast transient outward K+ current (I(to,f)), slow delayed outward K+ current (I(K,slow)), and steady-state K+ current (I(SS)) were significantly decreased in p90RSK-Tg mouse ventricular myocytes. mRNA levels of Kv4.3, Kv4.2, Kv1.5, Kv2.1, and KChIP2 from ventricles between p90RSK-Tg and nontransgenic littermate control mice were similar, as assessed by quantitative reverse transcriptase-polymerase chain reaction, indicating that p90RSK regulates voltage-gated K+ channels through posttranslational modification. Kv4.3- and Kv1.5- rather than Kv4.2- and Kv2.1-encoded channels in HEK 293 cells were inhibited by p90RSK. In vitro phosphorylation analysis showed that Kv4.3 was phosphorylated by p90RSK at 2 conserved sites, Ser516 and Ser550. p90RSK expression significantly inhibited Kv4.3- and Kv4.3 and KChIP2-encoded channel activities in HEK 293 cells, whereas p90RSK's effects were blocked by amino acid mutation(s) at phosphorylation site(s) in Kv4.3. Hydrogen peroxide, a mediator of induced cardiac p90RSK activation in ischemia/reperfusion injury and diabetes mellitus, had effects similar to those of p90RSK on Kv4.3- or Kv4.3- and KChIP2-encoded channels. Fluoromethylketone, a specific p90RSK inhibitor, abolished hydrogen peroxide effects. These findings indicate that p90RSK activation is critical for reactive oxygen species-mediated inhibition of voltage-gated K+ channel activity and leads to prolongation of cardiac repolarization.
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Affiliation(s)
- Zhibo Lu
- Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA
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88
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Miura K, Imaki J. Identification of ERK2-binding domain of EBITEIN1, a novel ERK2-binding protein. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1319-25. [PMID: 18590835 DOI: 10.1016/j.bbapap.2008.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 04/24/2008] [Accepted: 05/27/2008] [Indexed: 12/12/2022]
Abstract
We recently cloned a cDNA encoding a novel extracellular signal-regulated kinase 2 (ERK2) binding protein, EBITEIN1, by yeast two-hybrid screening. In this study, we further characterized EBITEIN1. Binding experiments using various deletion mutants identified a 40-amino acid minimal sequence for binding ERK2. Binding experiments using substitution mutants indicated the crucial role of arginine residues in this sequence. Based on empirical and bioinformatic analyses, we propose two domains in EBITEIN1. One is the minimal sequence for binding ERK2 (EB domain) and the other is the EBITEIN1 C-terminal domain (ECT domain). These results might pave the way for further empirical and bioinformatic analyses of EBITEIN1- and ERK2-mediated events.
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Affiliation(s)
- Kenji Miura
- Department of Developmental Anatomy and Regenerative Biology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
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89
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Goplen N, Gorska MM, Stafford SJ, Rozario S, Guo L, Liang Q, Alam R. A phosphosite screen identifies autocrine TGF-beta-driven activation of protein kinase R as a survival-limiting factor for eosinophils. THE JOURNAL OF IMMUNOLOGY 2008; 180:4256-64. [PMID: 18322238 DOI: 10.4049/jimmunol.180.6.4256] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The differential usage of signaling pathways by chemokines and cytokines in eosinophils is largely unresolved. In this study, we investigate signaling similarities and differences between CCL11 (eotaxin) and IL-5 in a phosphosite screen of human eosinophils. We confirm many previously known pathways of cytokine and chemokine signaling and elucidate novel phosphoregulation in eosinophils. The signaling molecules that were stimulated by both agents were members of the ERK1/2 and p38 MAPK pathways and their downstream effectors such as RSK and MSK1/2. Both agents inhibited S6 kinase, protein kinase Cepsilon, and glycogen synthase kinase 3 alpha and beta. The molecules that were differentially regulated include STATs and protein kinase R (PKR). One of the chief findings in this investigation was that PKR and eukaryotic initiation factor 2alpha are phosphorylated under basal conditions in eosinophils and neutrophils. This basal phosphorylation was linked to autocrine secretion of TGF-beta in eosinophils. TGF-beta directly activates PKR in eosinophils. Basal phosphorylation of PKR was inhibited by incubation of eosinophils with a neutralizing anti-TGF-beta Ab suggesting its physiological importance. We show that inhibition of PKR activity prolongs eosinophil survival. The eosinophil survival factor IL-5 strongly suppresses phosphorylation of PKR. The biological relevance of IL-5 inhibition of phospho-PKR was established by the observation that ex vivo bone marrow-derived eosinophils from OVA-immunized mice had no PKR phosphorylation in contrast to the high level of phosphorylation in sham-immunized mice. Together, our findings suggest that survival of eosinophils is in part controlled by basal activation of PKR through autocrine TGF-beta and that this could be modulated by a Th2 microenvironment in vivo.
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Affiliation(s)
- Nicholas Goplen
- National Jewish Medical and Research Center, Denver, CO 80206, USA
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90
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Abstract
MAP kinases transduce signals that are involved in a multitude of cellular pathways and functions in response to a variety of ligands and cell stimuli. Aberrant or inappropriate functions of MAPKs have now been identified in diseases ranging from cancer to inflammatory disease to obesity and diabetes. In many cell types, the MAPKs ERK1/2 are linked to cell proliferation. ERK1/2 are thought to play a role in some cancers, because mutations in Ras and B-Raf, which can activate the ERK1/2 cascade, are found in many human tumors. Abnormal ERK1/2 signaling has also been found in polycystic kidney disease, and serious developmental disorders such as cardio-facio-cutaneous syndrome arise from mutations in components of the ERK1/2 cascade. ERK1/2 are essential in well-differentiated cells and have been linked to long-term potentiation in neurons and in maintenance of epithelial polarity. Additionally, ERK1/2 are important for insulin gene transcription in pancreatic beta cells, which produce insulin in response to increases in circulating glucose to permit efficient glucose utilization and storage in the organism. Nutrients and hormones that induce or repress insulin secretion activate and/or inhibit ERK1/2 in a manner that reflects the secretory demand on beta cells. Disturbances in this and other regulatory pathways may result in the contribution of ERK1/2 to the etiology of certain human disorders.
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91
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Malakhova M, Tereshko V, Lee SY, Yao K, Cho YY, Bode A, Dong Z. Structural basis for activation of the autoinhibitory C-terminal kinase domain of p90 RSK2. Nat Struct Mol Biol 2008; 15:112-3. [PMID: 18084304 PMCID: PMC2864125 DOI: 10.1038/nsmb1347] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Accepted: 10/15/2007] [Indexed: 11/08/2022]
Abstract
The X-ray structure at 2.0-A resolution of the p90 ribosomal S6 kinase 2 C-terminal kinase domain revealed a C-terminal autoinhibitory alphaL-helix that was embedded in the kinase scaffold and determines the inactive kinase conformation. We suggest a mechanism of activation through displacement of the alphaL-helix and rearrangement of the conserved residue Glu500, as well as the reorganization of the T-loop into the active conformation.
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Affiliation(s)
- Margarita Malakhova
- The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, Minnesota 55912, USA
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92
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Kang S, Dong S, Guo A, Ruan H, Lonial S, Khoury HJ, Gu TL, Chen J. Epidermal growth factor stimulates RSK2 activation through activation of the MEK/ERK pathway and src-dependent tyrosine phosphorylation of RSK2 at Tyr-529. J Biol Chem 2007; 283:4652-7. [PMID: 18156174 DOI: 10.1074/jbc.m709673200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ser/Thr kinase ribosomal S6 kinase 2 (RSK2) has been demonstrated to phosphorylate transcription factor CREB (cyclic AMP-responsive-binding protein) and histone H3 in response to mitogenic stimulation by epidermal growth factor (EGF). EGF activates the MEK/ERK pathway to activate RSK2. We recently reported that receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) directly tyrosine phosphorylates RSK2 at Tyr-529, which consequently regulates RSK2 activation by facilitating inactive ERK binding to RSK2 that is required for ERK-dependent phosphorylation and activation of RSK2 (Kang, S., Dong, S., Gu, T. L., Guo, A., Cohen, M. S., Lonial, S., Khoury, H. J., Fabbro, D., Gilliland, D. G., Bergsagel, P. L., Taunton, J., Polakiewicz, R. D., and Chen, J. (2007) Cancer Cell 12, 201-214). Here we report that upon treatment of EGF, RSK2 was tyrosine-phosphorylated at Tyr-529 and activated in 293T and COS7 cells that do not express FGFR3. In contrast to FGFR3, the receptor tyrosine kinase EGF receptor did not directly phosphorylate RSK2 at Tyr-529 in an in vitro kinase assay using recombinant RSK2 and active EGF receptor or FGFR3. By mass spectroscopy-based studies, we identified Src tyrosine kinase family members Src and Fyn as upstream kinases of RSK2 Tyr-529. Treatment of Src inhibitor PP2 effectively attenuated EGF-dependent activation and Tyr-529 phosphorylation of RSK2, suggesting that Src family members are the kinases that phosphorylate RSK2 at Tyr-529 in response to EGF. Src and Fyn were able to directly phosphorylate RSK2 at Tyr-529 in the in vitro kinase assay. In vitro reconstitution of Tyr-529 phosphorylation by Src in glutathione S-transferase-tagged RSK2 enhanced inactive ERK binding to RSK2 wild type, but not the Y529F mutant. Together, our findings suggest that Src-dependent phosphorylation at Tyr-529 facilitates inactive ERK binding to RSK2, which might be a general requirement for RSK2 activation by EGF through the MEK/ERK pathway.
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Affiliation(s)
- Sumin Kang
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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93
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Martin MC, Allan LA, Mancini EJ, Clarke PR. The docking interaction of caspase-9 with ERK2 provides a mechanism for the selective inhibitory phosphorylation of caspase-9 at threonine 125. J Biol Chem 2007; 283:3854-65. [PMID: 18083711 DOI: 10.1074/jbc.m705647200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Caspase-9 plays a critical role in the initiation of apoptosis by the mitochondrial pathway. Activation of caspase-9 is inhibited by phosphorylation at Thr(125) by ERK1/2 MAPKs in response to growth factors. Here, we show that phosphorylation of this site is specific for these classical MAPKs and is not strongly induced when JNK and p38alpha/beta MAPKs are activated by anisomycin. By deletion and mutagenic analysis, we identify domains in caspase-9 and ERK2 that mediate their interaction. Binding of ERK2 to caspase-9 and subsequent phosphorylation of caspase-9 requires a basic docking domain (D domain) in the N-terminal prodomain of the caspase. Mutational analysis of ERK2 reveals a (157)TTCD(160) motif required for recognition of caspase-9 that acts independently of the putative common docking domain. Molecular modeling supports the conclusion that Arg(10) in the D domain of caspase-9 interacts with Asp(160) in the TTCD motif of ERK2. Differences in the TTCD motif in other MAPK family members could account for the selective recognition of caspase-9 by ERK1/2. This selectivity may be important for the antiapoptotic role of classical MAPKs in contrast to the proapoptotic roles of stress-activated MAPKs.
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Affiliation(s)
- Morag C Martin
- Biomedical Research Centre, Ninewells Hospital and Medical School, Level 5, University of Dundee, Dundee DD1 9SY, United Kingdom
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94
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Abstract
The ERK pathway responds to extracellular stimuli and oncogenes by modulating cellular processes, including transcription, adhesion, survival, and proliferation. ERK has diverse substrates that carry out these functions. The processes that are modulated are determined in part by the substrates that ERK phosphorylates. We demonstrate that PEA-15 (phosphoprotein enriched in astrocytes, 15 kDa) targets ERK to RSK2 and thereby enhances RSK2 activation. PEA-15 independently bound ERK and RSK2 and increased ERK association with RSK2 in a concentration-dependent manner. PEA-15 increased RSK2 activity and CREB-mediated transcription, and this process was regulated by phosphorylation of PEA-15. Finally, phorbol ester stimulation of PEA-15-null lymphocytes resulted in impaired RSK2 activation that was rescued by exogenous PEA-15 expression. Therefore, PEA-15 functions as a scaffold to enhance ERK activation of RSK2, and this activity is regulated by phosphorylation. Thus, PEA-15 can integrate signal transduction to provide a specific physiological outcome from activation of the multipotent ERK MAP kinase pathway.
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95
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Akella R, Moon TM, Goldsmith EJ. Unique MAP Kinase binding sites. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1784:48-55. [PMID: 18068683 DOI: 10.1016/j.bbapap.2007.09.016] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 08/22/2007] [Accepted: 09/21/2007] [Indexed: 12/20/2022]
Abstract
Map kinases are drug targets for autoimmune disease, cancer, and apoptosis-related diseases. Drug discovery efforts have developed MAP kinase inhibitors directed toward the ATP binding site and neighboring "DFG-out" site, both of which are targets for inhibitors of other protein kinases. On the other hand, MAP kinases have unique substrate and small molecule binding sites that could serve as inhibition sites. The substrate and processing enzyme D-motif binding site is present in all MAP kinases, and has many features of a good small molecule binding site. Further, the MAP kinase p38alpha has a binding site near its C-terminus discovered in crystallographic studies. Finally, the MAP kinases ERK2 and p38alpha have a second substrate binding site, the FXFP binding site that is exposed in active ERK2 and the D-motif peptide induced conformation of MAP kinases. Crystallographic evidence of these latter two binding sites is presented.
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Affiliation(s)
- Radha Akella
- Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-8816, USA
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96
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Cho YY, Yao K, Kim HG, Kang BS, Zheng D, Bode AM, Dong Z. Ribosomal S6 kinase 2 is a key regulator in tumor promoter induced cell transformation. Cancer Res 2007; 67:8104-12. [PMID: 17804722 PMCID: PMC2822657 DOI: 10.1158/0008-5472.can-06-4668] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ribosomal S6 kinase 2 (RSK2), a member of the p90(RSK) (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extracellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances cell survival. However, the roles of RSK2 in cell transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of cell transformation. When cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2(-/-) mouse embryonic fibroblasts (MEFs) compared with RSK2(+/+) MEFs. Moreover, RSK2(-/-) MEFs accumulated at the G(1) phase of the cell cycle under normal cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent cell transformation assay (soft agar), stable expression of RSK2 in JB6 cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (Ras(G12V))-induced foci formation in NIH3T3 cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser(10)). These results showed that RSK2 is a key regulator for cell transformation induced by tumor promoters such as EGF and TPA.
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Affiliation(s)
- Yong-Yeon Cho
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
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97
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Ikuta M, Kornienko M, Byrne N, Reid JC, Mizuarai S, Kotani H, Munshi SK. Crystal structures of the N-terminal kinase domain of human RSK1 bound to three different ligands: Implications for the design of RSK1 specific inhibitors. Protein Sci 2007; 16:2626-35. [PMID: 17965187 DOI: 10.1110/ps.073123707] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The p90 ribosomal S6 kinases (RSKs) also known as MAPKAP-Ks are serine/threonine protein kinases that are activated by ERK or PDK1 and act as downstream effectors of mitogen-activated protein kinase (MAPK). RSK1, a member of the RSK family, contains two distinct kinase domains in a single polypeptide chain, the regulatory C-terminal kinase domain (CTKD) and the catalytic N-terminal kinase domain (NTKD). Autophosphorylation of the CTKD leads to activation of the NTKD that subsequently phosphorylates downstream substrates. Here we report the crystal structures of the unactivated RSK1 NTKD bound to different ligands at 2.0 A resolution. The activation loop and helix alphaC, key regulatory elements of kinase function, are disordered. The DFG motif of the inactive RSK1 adopts an "active-like" conformation. The beta-PO(4) group in the AMP-PCP complex adopts a unique conformation that may contribute to inactivity of the enzyme. Structures of RSK1 ligand complexes offer insights into the design of novel anticancer agents and into the regulation of the catalytic activity of RSKs.
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Affiliation(s)
- Mari Ikuta
- Department of Structural Biology, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. mari_ikuta@.merck.com
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98
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Fernandes N, Bailey DE, Vanvranken DL, Allbritton NL. Use of docking peptides to design modular substrates with high efficiency for mitogen-activated protein kinase extracellular signal-regulated kinase. ACS Chem Biol 2007; 2:665-73. [PMID: 17918909 PMCID: PMC2597387 DOI: 10.1021/cb700158q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The mitogen-activated protein kinase extracellular regulated kinase (ERK) plays a key role in the regulation of cellular proliferation. Mutations in the ERK cascade occur in 30% of malignant tumors. Thus understanding how the kinase identifies its cognate substrates as well as monitoring the activity of ERK is central to cancer research and therapeutic development. ERK binds to its protein targets, both downstream substrates and upstream activators, via a binding site distinct from the catalytic site of ERK. The substrate sequences that bind, or dock, to these sites on ERK influence the efficiency of phosphorylation. For this reason, simple peptide substrates containing only phosphorylation sequences typically possess low efficiencies for ERK. Appending short docking peptides derived from full-length protein substrates and activators of ERK to a phosphorylation sequence increased the affinity of ERK for the phosphorylation sequence by as much as 200-fold while only slightly diminishing the maximal velocity of the reaction. The efficiency of the phosphorylation reaction was increased by up to 150-fold, while the specificity of the substrate for ERK was preserved. Simple modular peptide substrates, which can be easily tailored to possess high phosphorylation efficiencies, will enhance our understanding of the regulation of ERK and provide a tool for the development of new kinase assays.
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Affiliation(s)
- Neychelle Fernandes
- Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697, USA
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99
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Abstract
During T-cell activation, a number of cytokine-activated signaling cascades, including the Jak-STAT, phosphoinositol 3-kinase (PI 3-kinase), and mitogen-activated protein kinase (MAPK) pathways, play important roles in modulating the expression of target genes and mediating a cellular response. We now report that interleukin 2 (IL-2) and IL-15, but not IL-7, rapidly activate the p90 ribosomal S6 kinases, Rsk1 and Rsk2, in human T lymphocytes. Surprisingly, mouse spleen T cells transduced with either the wild-type or a dominant-negative (DN) Rsk2-expressing retrovirus could not be recovered, in contrast to the normal survival of T cells transduced with retroviruses expressing wild-type or DN mutants of Rsk1 or Rsk3. Examination of Rsk2 knockout (KO) mice revealed normal T-cell development, but these T cells had delayed cell-cycle progression and lower production of IL-2 in response to anti-CD3 and anti-CD28 stimulation in vitro. Moreover, Rsk2 KO mice had defective homeostatic T-cell expansion following sublethal irradiation in vivo, which is known to involve T-cell receptor (TCR), IL-2, and/or IL-15 signals, each of which we demonstrate can rapidly and potently activate Rsk2 in mouse T cells. These results indicate an essential nonredundant role of Rsk2 in T-cell activation.
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100
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Pan Q, Zhang ZB, Zhang X, Shi J, Chen YX, Han ZG, Xie WF. Gene expression profile analysis of the spontaneous reversal of rat hepatic fibrosis by cDNA microarray. Dig Dis Sci 2007; 52:2591-600. [PMID: 17805973 DOI: 10.1007/s10620-006-9676-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Accepted: 11/07/2006] [Indexed: 01/28/2023]
Abstract
Our aim was to gain insight into the gene expression profile during hepatic fibrosis autoreversal. Spontaneous recovery from hepatic fibrosis was created in SD rats by CCl(4) exposure for 8 weeks and then withdrawal for 6 weeks. Then differentially expressed genes during regression of fibrosis were analyzed using cDNA microarray. Results obtained were further subjected to hierarchical clustering and validated by semiquantitative RT-PCR. Expression of Mapk1 and Rps6ka1, which are critical members of the mitogen-activated protein kinase (MAPK) signaling pathway, was also investigated by Northern blot and immunohistochemistry. Microarray hybridization identified 254 genes differentially expressed throughout resolution of fibrosis. Being verified by RT-PCR, up- or down-regulated genes were classified into various groups according to clustering and function: (1) metabolic enzymes, (2) facilitated diffusion proteins/transporters/symporters, (3) gastrointestinal hormones/receptors, (4) lipoproteins/fatty acid binding proteins, (5) transcription factors/nuclear factors, and (6) the MAPK signaling pathway. The mRNA level of Mapk1 increased greatly as hepatic fibrosis reversed. Meanwhile Mapk1 and Rps6ka1 were proven to be expressed in hepatocytes and absent from mesenchymal cells. Six groups of genes exhibit a close relation to the recovery of CCl(4)-induced hepatic fibrosis. The MAPK signaling-dependent pathway, representing one of the gene groups, may contribute to the reversal of hepatic fibrosis.
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Affiliation(s)
- Qin Pan
- Department of Gastroenterology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, PRC
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