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Mendes AI, Matos P, Moniz S, Jordan P. Protein kinase WNK1 promotes cell surface expression of glucose transporter GLUT1 by regulating a Tre-2/USP6-BUB2-Cdc16 domain family member 4 (TBC1D4)-Rab8A complex. J Biol Chem 2010; 285:39117-26. [PMID: 20937822 DOI: 10.1074/jbc.m110.159418] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One mechanism by which mammalian cells regulate the uptake of glucose is the number of glucose transporter proteins (GLUT) present at the plasma membrane. In insulin-responsive cells types, GLUT4 is released from intracellular stores through inactivation of the Rab GTPase activating protein Tre-2/USP6-BUB2-Cdc16 domain family member 4 (TBC1D4) (also known as AS160). Here we describe that TBC1D4 forms a protein complex with protein kinase WNK1 in human embryonic kidney (HEK293) cells. We show that WNK1 phosphorylates TBC1D4 in vitro and that the expression levels of WNK1 in these cells regulate surface expression of the constitutive glucose transporter GLUT1. WNK1 was found to increase the binding of TBC1D4 to regulatory 14-3-3 proteins while reducing its interaction with the exocytic small GTPase Rab8A. These effects were dependent on the catalytic activity because expression of a kinase-dead WNK1 mutant had no effect on binding of 14-3-3 and Rab8A, or on surface GLUT1 levels. Together, the data describe a pathway regulating constitutive glucose uptake via GLUT1, the expression level of which is related to several human diseases.
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Affiliation(s)
- Ana Isabel Mendes
- Department of Genetics, National Health Institute, Dr. Ricardo Jorge, Lisbon 1649-016, Portugal
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252
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14-3-3 binding to LRRK2 is disrupted by multiple Parkinson's disease-associated mutations and regulates cytoplasmic localization. Biochem J 2010; 430:393-404. [PMID: 20642453 PMCID: PMC2932554 DOI: 10.1042/bj20100483] [Citation(s) in RCA: 310] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
LRRK2 (leucine-rich repeat protein kinase 2) is mutated in a significant number of Parkinson's disease patients, but still little is understood about how it is regulated or functions. In the present study we have demonstrated that 14-3-3 protein isoforms interact with LRRK2. Consistent with this, endogenous LRRK2 isolated from Swiss 3T3 cells or various mouse tissues is associated with endogenous 14-3-3 isoforms. We have established that 14-3-3 binding is mediated by phosphorylation of LRRK2 at two conserved residues (Ser910 and Ser935) located before the leucine-rich repeat domain. Our results suggests that mutation of Ser910 and/or Ser935 to disrupt 14-3-3 binding does not affect intrinsic protein kinase activity, but induces LRRK2 to accumulate within discrete cytoplasmic pools, perhaps resembling inclusion bodies. To investigate links between 14-3-3 binding and Parkinson's disease, we studied how 41 reported mutations of LRRK2 affected 14-3-3 binding and cellular localization. Strikingly, we found that five of the six most common pathogenic mutations (R1441C, R1441G, R1441H, Y1699C and I2020T) display markedly reduced phosphorylation of Ser910/Ser935 thereby disrupting interaction with 14-3-3. We have also demonstrated that Ser910/Ser935 phosphorylation and 14-3-3 binding to endogenous LRRK2 is significantly reduced in tissues of homozygous LRRK2(R1441C) knock-in mice. Consistent with 14-3-3 regulating localization, all of the common pathogenic mutations displaying reduced 14-3-3-binding accumulated within inclusion bodies. We also found that three of the 41 LRRK2 mutations analysed displayed elevated protein kinase activity (R1728H, ~2-fold; G2019S, ~3-fold; and T2031S, ~4-fold). These results provide the first evidence suggesting that 14-3-3 regulates LRRK2 and that disruption of the interaction of LRRK2 with 14-3-3 may be linked to Parkinson's disease.
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253
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Ren HZ, Pan GQ, Wang JS, Wen JF, Wang KS, Luo GQ, Shan XZ. Reduced stratifin expression can serve as an independent prognostic factor for poor survival in patients with esophageal squamous cell carcinoma. Dig Dis Sci 2010; 55:2552-60. [PMID: 20108042 DOI: 10.1007/s10620-009-1065-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 11/20/2009] [Indexed: 12/20/2022]
Abstract
UNLABELLED Stratifin plays an important role in cancer biology by interfering with intracellular signalling pathways and cell-cycle checkpoints. Decreased expression of stratifin gene has been reported to be a poor prognostic indicator in a variety of human malignant tumors. AIM To clarify the role and prognostic significance of stratifin in esophageal squamous cell carcinoma (ESCC). METHODS The alteration of stratifin messenger RNA (mRNA) and protein was analyzed by reverse-transcription and quantitative real-time polymerase chain reaction (QRT-PCR) and Western blotting in 20 paired ESCC and nonneoplastic esophageal mucosa tissues, respectively. Then, immunohistochemistry (IHC) was used to evaluate expression of stratifin in tissues of 148 ESCC patients (including the former 20 pairs of tissues) and correlate it with clinicopathological parameters and prognosis of ESCC patients. RESULTS The stratifin level of mRNA and protein was markedly downregulated in ESCC tissue compared with in corresponding nonneoplastic esophageal epithelium (P<0.05). Similarly, the positive rate of stratifin protein expression was lower in the esophageal cancer than in paired nonneoplastic esophageal epithelium as detected by IHC (P=0.007). Statistically, the downregulation of stratifin expression was correlated with tumor infiltration depth (P=0.003), lymph node metastasis (P=0.008), distant metastasis (P=0.013), and lymphovascular invasion (P=0.007) of ESCC. Furthermore, the reduced stratifin expression was associated with shorter 5-year survival rate of ESCC patients after curative surgery (P<0.0001). On the basis of univariate and multivariate Cox regression analysis, we found that reduced stratifin expression, T4 stage, lymph node metastasis, and distant metastasis were independent risk factors for worse prognosis in ESCC patients. CONCLUSION The present report indicates that stratifin could be a useful indicator for prognosis of this disease, as well as a potential target for more effective therapy.
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MESH Headings
- 14-3-3 Proteins/analysis
- 14-3-3 Proteins/genetics
- Adult
- Aged
- Biomarkers, Tumor/analysis
- Biomarkers, Tumor/genetics
- Blotting, Western
- Carcinoma, Squamous Cell/chemistry
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/mortality
- Carcinoma, Squamous Cell/secondary
- Carcinoma, Squamous Cell/surgery
- Chi-Square Distribution
- Down-Regulation
- Esophageal Neoplasms/chemistry
- Esophageal Neoplasms/genetics
- Esophageal Neoplasms/mortality
- Esophageal Neoplasms/pathology
- Esophageal Neoplasms/surgery
- Esophagectomy
- Exonucleases/analysis
- Exonucleases/genetics
- Exoribonucleases
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Immunohistochemistry
- Kaplan-Meier Estimate
- Lymphatic Metastasis
- Male
- Middle Aged
- Neoplasm Invasiveness
- Neoplasm Staging
- Predictive Value of Tests
- Proportional Hazards Models
- RNA, Messenger/analysis
- Reverse Transcriptase Polymerase Chain Reaction
- Risk Assessment
- Risk Factors
- Time Factors
- Treatment Outcome
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Affiliation(s)
- Hong-Zheng Ren
- Department of Pathology, Xiangya Basic Medical College, Central South University, Changsha, China
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254
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Yu D, dos Santos CO, Zhao G, Jiang J, Amigo JD, Khandros E, Dore LC, Yao Y, D'Souza J, Zhang Z, Ghaffari S, Choi J, Friend S, Tong W, Orange JS, Paw BH, Weiss MJ. miR-451 protects against erythroid oxidant stress by repressing 14-3-3zeta. Genes Dev 2010; 24:1620-33. [PMID: 20679398 DOI: 10.1101/gad.1942110] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The bicistronic microRNA (miRNA) locus miR-144/451 is highly expressed during erythrocyte development, although its physiological roles are poorly understood. We show that miR-144/451 ablation in mice causes mild erythrocyte instability and increased susceptibility to damage after exposure to oxidant drugs. This phenotype is deeply conserved, as miR-451 depletion synergizes with oxidant stress to cause profound anemia in zebrafish embryos. At least some protective activities of miR-451 stem from its ability to directly suppress production of 14-3-3zeta, a phospho-serine/threonine-binding protein that inhibits nuclear accumulation of transcription factor FoxO3, a positive regulator of erythroid anti-oxidant genes. Thus, in miR-144/451(-/-) erythroblasts, 14-3-3zeta accumulates, causing partial relocalization of FoxO3 from nucleus to cytoplasm with dampening of its transcriptional program, including anti-oxidant-encoding genes Cat and Gpx1. Supporting this mechanism, overexpression of 14-3-3zeta in erythroid cells and fibroblasts inhibits nuclear localization and activity of FoxO3. Moreover, shRNA suppression of 14-3-3zeta protects miR-144/451(-/-) erythrocytes against peroxide-induced destruction, and restores catalase activity. Our findings define a novel miRNA-regulated pathway that protects erythrocytes against oxidant stress, and, more generally, illustrate how a miRNA can influence gene expression by altering the activity of a key transcription factor.
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Affiliation(s)
- Duonan Yu
- Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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255
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Kerrigan JJ, Xie Q, Ames RS, Lu Q. Production of protein complexes via co-expression. Protein Expr Purif 2010; 75:1-14. [PMID: 20692346 DOI: 10.1016/j.pep.2010.07.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 07/22/2010] [Accepted: 07/31/2010] [Indexed: 12/21/2022]
Abstract
Multi-protein complexes are involved in essentially all cellular processes. A protein's function is defined by a combination of its own properties, its interacting partners, and the stoichiometry of each. Depending on binding partners, a transcription factor can function as an activator in one instance and a repressor in another. The study of protein function or malfunction is best performed in the relevant context. While many protein complexes can be reconstituted from individual component proteins after being produced individually, many others require co-expression of their native partners in the host cells for proper folding, stability, and activity. Protein co-expression has led to the production of a variety of biological active complexes in sufficient quantities for biochemical, biophysical, structural studies, and high throughput screens. This article summarizes examples of such cases and discusses critical considerations in selecting co-expression partners, and strategies to achieve successful production of protein complexes.
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Affiliation(s)
- John J Kerrigan
- Biological Reagents & Assay Development, Platform Technology & Science, GlaxoSmithKline R&D, 1250 South Collegeville Road, Collegeville, PA 19426, USA
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256
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Sugden C, Ross S, Bloomfield G, Ivens A, Skelton J, Mueller-Taubenberger A, Williams JG. Two novel Src homology 2 domain proteins interact to regulate dictyostelium gene expression during growth and early development. J Biol Chem 2010; 285:22927-35. [PMID: 20457612 PMCID: PMC2906285 DOI: 10.1074/jbc.m110.139733] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Indexed: 01/01/2023] Open
Abstract
There are 13 Dictyostelium Src homology 2 (SH2) domain proteins, almost 10-fold fewer than in mammals, and only three are functionally unassigned. One of these, LrrB, contains a novel combination of protein interaction domains: an SH2 domain and a leucine-rich repeat domain. Growth and early development appear normal in the mutant, but expression profiling reveals that three genes active at these stages are greatly underexpressed: the ttdA metallohydrolase, the abcG10 small molecule transporter, and the cinB esterase. In contrast, the multigene family encoding the lectin discoidin 1 is overexpressed in the disruptant strain. LrrB binds to 14-3-3 protein, and the level of binding is highest during growth and decreases during early development. Comparative tandem affinity purification tagging shows that LrrB also interacts, via its SH2 domain and in a tyrosine phosphorylation-dependent manner, with two novel proteins: CldA and CldB. Both of these proteins contain a Clu domain, a >200-amino acid sequence present within highly conserved eukaryotic proteins required for correct mitochondrial dispersal. A functional interaction of LrrB with CldA is supported by the fact that a cldA disruptant mutant also underexpresses ttdA, abcG10, and cinB. Significantly, CldA is itself one of the three functionally unassigned SH2 domain proteins. Thus, just as in metazoa, but on a vastly reduced numerical scale, an interacting network of SH2 domain proteins regulates specific Dictyostelium gene expression.
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Affiliation(s)
- Christopher Sugden
- From the
School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, United Kingdom
| | - Susan Ross
- From the
School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, United Kingdom
| | - Gareth Bloomfield
- the
Wellcome Trust Sanger Institute, Hinxton CB10 1SA, United Kingdom
| | - Alasdair Ivens
- the
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom, and
| | - Jason Skelton
- the
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom, and
| | - Annette Mueller-Taubenberger
- the
Institute for Cell Biology and Center for Integrated Protein Science, Munich, Ludwig Maximilians University, Schillerstrasse 42, D-80336 Munich, Germany
| | - Jeffrey G. Williams
- From the
School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, United Kingdom
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257
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Pozuelo-Rubio M. Proteomic and biochemical analysis of 14-3-3-binding proteins during C2-ceramide-induced apoptosis. FEBS J 2010; 277:3321-42. [DOI: 10.1111/j.1742-4658.2010.07730.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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258
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Jeong EA, Jeon BT, Kim JB, Kim JS, Cho YW, Lee DH, Kim HJ, Kang SS, Cho GJ, Choi WS, Roh GS. Phosphorylation of 14-3-3ζ at serine 58 and neurodegeneration following kainic acid-induced excitotoxicity. Anat Cell Biol 2010; 43:150-6. [PMID: 21189996 PMCID: PMC2998790 DOI: 10.5115/acb.2010.43.2.150] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 05/28/2010] [Accepted: 05/31/2010] [Indexed: 11/27/2022] Open
Abstract
Oxidative stress-induced cell death leads to phosphorylation of 14-3-3ζ at serine 58. 14-3-3ζ is detected at significant levels in cerebrospinal fluid after kainic acid (KA)-induced seizures. Here we examined temporal changes in 14-3-3ζ phosphorylation in the hippocampus and amygdala of mice after KA treatment. Mice were killed at 2, 6, 24, or 48 h after KA (30 mg/kg) injection. We observed an increase in TUNEL and Fluoro-Jade B (FJB)-stained neurons in the hippocampus and amygdala of KA-treated mice. Phospho (p)-14-3-3ζ and p-JNK expression was increased in the hippocampus 2 and 6 h after KA treatment, respectively. In immunohistochemical analysis, p-14-3-3ζ-positive cells were present in the CA3 region of the hippocampus and the central nucleus of amygdala (CeA) of KA-treated mice. Thus, phosphorylation of 14-3-3ζ at serine 58 may play an important role in KA-induced hippocampal and amygdaloid neuronal damage.
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Affiliation(s)
- Eun Ae Jeong
- Department of Anatomy and Neurobiology, Institute of Health Sciences, Medical Research Center for Neural Dysfunction, Biomedical Center (BK21), Gyeongsang National University School of Medicine, Jinju, Korea
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259
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Rezabkova L, Boura E, Herman P, Vecer J, Bourova L, Sulc M, Svoboda P, Obsilova V, Obsil T. 14-3-3 protein interacts with and affects the structure of RGS domain of regulator of G protein signaling 3 (RGS3). J Struct Biol 2010; 170:451-61. [DOI: 10.1016/j.jsb.2010.03.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 03/12/2010] [Accepted: 03/22/2010] [Indexed: 11/30/2022]
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260
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Veisova D, Rezabkova L, Stepanek M, Novotna P, Herman P, Vecer J, Obsil T, Obsilova V. The C-terminal segment of yeast BMH proteins exhibits different structure compared to other 14-3-3 protein isoforms. Biochemistry 2010; 49:3853-61. [PMID: 20384366 DOI: 10.1021/bi100273k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Yeast 14-3-3 protein isoforms BMH1 and BMH2 possess a distinctly variant C-terminal tail which differentiates them from the isoforms of higher eukaryotes. Their C-termini are longer and contain a polyglutamine stretch of unknown function. It is now well established that the C-terminal segment of 14-3-3 proteins plays an important regulatory role by functioning as an autoinhibitor which occupies the ligand binding groove and blocks the binding of inappropriate ligands. Whether the same holds true or not for the yeast isoforms is unclear. Therefore, we investigated the conformational behavior of the C-terminal segment of BMH proteins using various biophysical techniques. Dynamic light scattering, sedimentation velocity, time-resolved fluorescence anisotropy decay, and size exclusion chromatography measurements showed that the molecules of BMH proteins are significantly larger compared to the human 14-3-3zeta isoform. On the other hand, the sedimentation analysis confirmed that BMH proteins form dimers. Time-resolved tryptophan fluorescence experiments revealed no dramatic structural changes of the C-terminal segment upon the ligand binding. Taken together, the C-terminal segment of BMH proteins adopts a widely opened and extended conformation that makes difficult its folding into the ligand binding groove, thus increasing the apparent molecular size. It seems, therefore, that the C-terminal segment of BMH proteins does not function as an autoinhibitor.
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Affiliation(s)
- Dana Veisova
- Institute of Physiology, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic
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261
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Electrostatic interactions play a minor role in the binding of ExoS to 14-3-3 proteins. Biochem J 2010; 427:217-24. [PMID: 20144150 DOI: 10.1042/bj20100043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
14-3-3 proteins belong to a family of conserved molecules expressed in all eukaryotic cells that play an important role in a multitude of signalling pathways. 14-3-3 proteins bind either to phosphoserine/phosphothreonine residues or to sequence-specific non-phosphorylated motifs in more than 200 interaction partners [Pozuelo Rubio, Geraghty, Wong, Wood, Campbell, Morrice and Mackintosh (2004) Biochem. J. 379, 395-408]. These interactions result in cell-cycle regulation, apoptosis, stress responses, cell metabolism and malignant transformation. One example of a phosphorylation-independent interaction is the binding of 14-3-3 to ExoS (exoenzyme S), a bacterial ADP-ribosyltransferase toxin of Pseudomonas aeruginosa. In the present study, we have utilized additional biochemical and infection analyses to define further the structural basis of the interaction between ExoS and 14-3-3. An ExoS leucine-substitution mutant dramatically reduced the interaction potential with 14-3-3 suggesting that Leu422, Leu423, Leu426 and Leu428 of ExoS are important for its interaction with 14-3-3, its enzymatic activity and cytotoxicity. However, ExoS substitution mutants of residues that interact with 14-3-3 through an electrostatic interaction, such as Ser416, His418, Asp424 and Asp427, showed no reduction in their interaction potential with 14-3-3. These ExoS substitution mutants were also as aggressive as wild-type ExoS at inducing cell death and to modify endogenous ExoS target within the cell. In conclusion, electrostatic interaction between ExoS and 14-3-3 via polar residues (Ser416, His418, Asp424 and Asp427) appears to be of secondary importance. Thus the interaction between the 'roof' of the groove of 14-3-3 and ExoS relies more on hydrophobic interaction forces, which probably contributes to induce cell death after ExoS infection and activation.
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262
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Woodcock SA, Jones RC, Edmondson RD, Malliri A. A modified tandem affinity purification technique identifies that 14-3-3 proteins interact with Tiam1, an interaction which controls Tiam1 stability. J Proteome Res 2010; 8:5629-41. [PMID: 19899799 DOI: 10.1021/pr900716e] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The Rac-specific GEF (guanine-nucleotide exchange factor) Tiam1 has important functions in multiple cellular processes including proliferation, apoptosis and adherens junction maintenance. Here we describe a modified tandem affinity purification (TAP) technique that we have applied to specifically enrich Tiam1-containing protein complexes from mammalian cells. Using this technique in conjunction with LC-MS/MS mass spectrometry, we have identified additional Tiam1-interacting proteins not seen with the standard technique, and have identified multiple 14-3-3 family members as Tiam1 interactors. We confirm the Tiam1/14-3-3 protein interaction by GST-pulldown and coimmunoprecipitation experiments, show that it is phosphorylation-dependent, and that they colocalize in cells. The interaction is largely dependent on the N-terminal region of Tiam1; within this region, there are four putative phospho-serine-containing 14-3-3 binding motifs, and we confirm that two of them (Ser172 and Ser231) are phosphorylated in cells using mass spectrometry. Moreover, we show that phosphorylation at three of these motifs (containing Ser60, Ser172 and Ser231) is required for the binding of 14-3-3 proteins to this region of Tiam1. We show that phosphorylation of these sites does not affect Tiam1 activity; significantly however, we demonstrate that phosphorylation of the Ser60-containing motif is required for the degradation of Tiam1. Thus, we have established and proven methodology that allows the identification of additional protein-protein interactions in mammalian cells, resulting in the discovery of a novel mechanism of regulating Tiam1 stability.
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Affiliation(s)
- Simon A Woodcock
- Cell Signalling Group, Cancer Research UK Paterson Institute for Cancer Research, University of Manchester, Manchester, M20 4BX, United Kingdom.
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263
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Liang S, Xu Y, Shen G, Liu Q, Zhao X, Xu Z, Xie X, Gong F, Li R, Wei Y. Quantitative protein expression profiling of 14-3-3 isoforms in human renal carcinoma shows 14-3-3 epsilon is involved in limitedly increasing renal cell proliferation. Electrophoresis 2010; 30:4152-62. [PMID: 19960480 DOI: 10.1002/elps.200900249] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
14-3-3 proteins regulate many cellular processes that are implicated in cancer development, and the seven 14-3-3 isoforms have different expression level and isoform-specific roles in different tumors. However, the biological functions of 14-3-3 proteins and their correlations with renal carcinoma have not been investigated so far. In our study, the expression profiles and functional characterization of 14-3-3 proteins were discovered by a sensitive stable isotope labeling with amino acids in cell culture based quantitative proteomics analysis in human renal carcinoma tissues. We found that 14-3-3epsilon was up-regulated with 1.44-fold changes in renal cancerous tissues compared with that in counterpart kidney tissues, and 14-3-3sigma was almost not detected in both tissues due to its DNA highly methylated in our previous reports. The other five isoforms almost have similar expression level in two states of renal tissues. The following RT-PCR, Western blot and immunohistochemistry analysis for specific 14-3-3 isoform expression were all consistent with the quantitative proteomic data. Furthermore, the overexpression of 14-3-3epsilon in vitro can limitedly prompt the abnormal growth of renal tumor cells.
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Affiliation(s)
- Shufang Liang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu 610041, PR China.
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264
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Ren F, Zhang L, Jiang J. Hippo signaling regulates Yorkie nuclear localization and activity through 14-3-3 dependent and independent mechanisms. Dev Biol 2010; 337:303-12. [PMID: 19900439 PMCID: PMC2812623 DOI: 10.1016/j.ydbio.2009.10.046] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 10/13/2009] [Accepted: 10/31/2009] [Indexed: 01/15/2023]
Abstract
The Hippo (Hpo) signaling pathway controls cell growth, proliferation and apoptosis in both Drosophila and vertebrates. In Drosophila, Hpo signaling regulates gene expression by inhibiting a transcription complex consisting of the transcriptional coactivator Yorkie (Yki) and the TEAD/TEF family of transcription factor Scalloped (Sd). Here we provide genetic evidence that both isoforms of 14-3-3, 14-3-3varepsilon and 14-3-3zeta, regulate Yki activity through modulating its subcellular localization. Inactivation of 14-3-3 by RNAi or genetic mutations enhanced whereas overexpression of 14-3-3 suppressed tissue overgrowth induced by Yki overexpression. Loss of 14-3-3 resulted in the accumulation of Yki in the nucleus. We found that regulation of Yki by 14-3-3 was mediated by phosphorylation of Yki at S168. In addition, we found that Hpo signaling also inhibited Yki nuclear localization and activity by phosphorylating Yki at S111 and S250, and this inhibition appears to be independent of 14-3-3. Finally, we provided evidence that Hpo signaling restricted Yki nuclear localization depending on CRM1-mediated nuclear export.
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Affiliation(s)
- Fangfang Ren
- Department of Developmental Biology, University of Texas, Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lei Zhang
- Department of Developmental Biology, University of Texas, Southwestern Medical Center, Dallas, TX 75390, USA
- Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 20031, China
| | - Jin Jiang
- Department of Developmental Biology, University of Texas, Southwestern Medical Center, Dallas, TX 75390, USA
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265
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Larance M, Rowland AF, Hoehn KL, Humphreys DT, Preiss T, Guilhaus M, James DE. Global phosphoproteomics identifies a major role for AKT and 14-3-3 in regulating EDC3. Mol Cell Proteomics 2010; 9:682-94. [PMID: 20051463 DOI: 10.1074/mcp.m900435-mcp200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin plays an essential role in metabolic homeostasis in mammals, and many of the underlying biochemical pathways are regulated via the canonical phosphatidylinositol 3-kinase/AKT pathway. To identify novel metabolic actions of insulin, we conducted a quantitative proteomics analysis of insulin-regulated 14-3-3-binding proteins in muscle cells. These studies revealed a novel role for insulin in the post-transcriptional regulation of mRNA expression. EDC3, a component of the mRNA decay and translation repression pathway associated with mRNA processing bodies, was shown to be phosphorylated by AKT downstream of insulin signaling. The major insulin-regulated site was mapped to Ser-161, and phosphorylation at this site led to increased 14-3-3 binding. Functional studies indicated that induction of 14-3-3 binding to EDC3 causes morphological changes in processing body structures, inhibition of microRNA-mediated mRNA post-transcriptional regulation, and alterations in the protein- protein interactions of EDC3. These data highlight an important new arm of the insulin signaling cascade in the regulation of mRNA utilization.
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Affiliation(s)
- Mark Larance
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, Australia.
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266
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Speth C, Jaspert N, Marcon C, Oecking C. Regulation of the plant plasma membrane H+-ATPase by its C-terminal domain: what do we know for sure? Eur J Cell Biol 2009; 89:145-51. [PMID: 20034701 DOI: 10.1016/j.ejcb.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: 11/26/2022] Open
Abstract
The plant plasma membrane H(+)-ATPase is kept at a low activity level by its C-terminal domain, the inhibitory function of which is thought to be mediated by two regions (region I and II) interacting with cytoplasmic domains essential for the catalytic cycle. The activity of the enzyme is well known to be regulated by 14-3-3 proteins, the association of which requires phosphorylation of the penultimate H(+)-ATPase residue, but can be abolished by phosphorylation of residues close-by. The current knowledge about H(+)-ATPase regulation is briefly summed up here, combined with data that query some of the above statements. Expression of various C-terminal deletion constructs of PMA2, a H(+)-ATPase isoform from Nicotiana plumbaginifolia, in yeast indicates that three regions, which do not correspond to regions I or II, contribute to autoinhibition. Their individual and combined action can be abolished by (mimicking) phosphorylation of three threonine residues located within or close to these regions. With respect to the wild-type PMA2, mimicking phosphorylation of two of these residues increases enzyme activity. However, constitutive activation of wild-type PMA2 requires 14-3-3 association. Altogether, the data suggest that regulation of the plant H(+)-ATPase occurs in progressive steps, mediated by several protein kinases and phosphatases, thus allowing gradual as well as fine-tuned adjustment of its activity. Moreover, mating-based split ubiquitin assays indicate a complex interplay between the C-terminal domain and the rest of the enzyme. Notably, their tight contact does not seem to be the cause of the inactive state of the enzyme.
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Affiliation(s)
- Corinna Speth
- Center for Plant Molecular Biology - Plant Physiology, University of Tübingen, Auf der Morgenstelle 5, 72076 Tübingen, Germany
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267
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Cockrell LM, Puckett MC, Goldman EH, Khuri FR, Fu H. Dual engagement of 14-3-3 proteins controls signal relay from ASK2 to the ASK1 signalosome. Oncogene 2009; 29:822-30. [PMID: 19935702 DOI: 10.1038/onc.2009.382] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Faithful and efficient transmission of biological signals through mitogen-activated protein kinase (MAPK) pathways requires engagement of highly regulated cellular machinery in response to diverse environmental cues. Here, we report a novel mechanism controlling signal relay between two MAP3Ks, apoptosis signal-regulating kinase (ASK) 1 and ASK2. We show that ASK2 specifically interacts with 14-3-3 proteins through phosphorylated S964. Although a 14-3-3-binding defective mutant of ASK1 (S967A) has no effect on the ASK2/14-3-3 interaction, both overexpression of the analogous ASK2 (S964A) mutant and knockdown of ASK2 dramatically reduced the amount of ASK1 complexed with 14-3-3. These data suggest a dominant role of ASK2 in 14-3-3 control of ASK1 function. Indeed, ASK2 S964A-induced dissociation of 14-3-3 from ASK1 correlated with enhanced phosphorylation of ASK1 at T838 and increased c-Jun N-terminal kinase phosphorylation, the two biological readouts of ASK1 activation. Our results suggest a model in which upstream signals couple ASK2 S964 phosphorylation to the ASK1 signalosome through dual engagement of 14-3-3.
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Affiliation(s)
- L M Cockrell
- Program in Molecular and Systems Pharmacology of the Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322, USA
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268
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Rajagopalan S, Sade RS, Townsley FM, Fersht AR. Mechanistic differences in the transcriptional activation of p53 by 14-3-3 isoforms. Nucleic Acids Res 2009; 38:893-906. [PMID: 19933256 PMCID: PMC2817464 DOI: 10.1093/nar/gkp1041] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
p53 maintains genome integrity by initiating the transcription of genes involved in cell-cycle arrest, senescence, apoptosis and DNA repair. The activity of p53 is regulated by both post-translational modifications and protein–protein interactions. p53 that has been phosphorylated at S366, S378 and T387 binds 14-3-3 proteins in vitro. Here, we show that these sites are potential 14-3-3 binding sites in vivo. Epsilon (ε) and gamma (γ) isoforms required phosphorylation at either of these sites for efficient interaction with p53, while for sigma (σ) and tau (τ) these sites are dispensable. Further, σ and τ bound more weakly to p53 C-terminal phosphopeptides than did ε and γ. However, the four isoforms bound tightly to di-phosphorylated p53 C-terminal peptides than did the mono-phosphorylated counterparts. Interestingly, all the isoforms studied transcriptionally activated wild-type p53. σ and τ stabilized p53 levels in cells, while ε and γ stimulated p53-DNA binding activity in vitro. Overall, the results suggest that structurally and functionally similar 14-3-3 isoforms may exert their regulatory potential on p53 through different mechanisms. We discuss the isoform-specific roles of 14-3-3 in p53 stabilization and activation of specific-DNA binding.
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269
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Benz C, Engstler M, Hillmer S, Clayton C. Depletion of 14-3-3 proteins in bloodstream-form Trypanosoma brucei inhibits variant surface glycoprotein recycling. Int J Parasitol 2009; 40:629-34. [PMID: 19925803 DOI: 10.1016/j.ijpara.2009.10.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 10/14/2009] [Accepted: 10/27/2009] [Indexed: 02/03/2023]
Abstract
Bloodstream-form Trypanosoma brucei have two 14-3-3 proteins, which are required for parasite multiplication. We here describe the effects of 14-3-3 depletion on vesicular transport of variant surface glycoprotein (VSG). 14-3-3 depletion had no detectable effect on de novo synthesis and trafficking of VSG to the cell surface, or on VSG endocytosis. Despite strong inhibition of cell division, the flagellar pocket was not enlarged and the ultrastructure of internal organelles appeared normal. The Rab11-positive recycling endosome compartment was, however, fivefold smaller than normal, and the rate of return of recycling VSG to the surface was correspondingly reduced. Down-regulating 14-3-3 also prevented enlargement of the flagellar pocket by clathrin depletion. These results suggest that there is a remarkably specific requirement for 14-3-3 in normal functioning of the Rab11-positive recycling endosome compartment.
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Affiliation(s)
- Corinna Benz
- Zentrum für Molekulare Biologie der Universität Heidelberg, ZMBH-DKFZ Alliance, Im Neuenheimer Feld 282, D69120 Heidelberg, Germany
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270
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Molecular characterisation of MEK1/2- and MKK3/6-like mitogen-activated protein kinase kinases (MAPKK) from the fox tapeworm Echinococcus multilocularis. Int J Parasitol 2009; 40:555-67. [PMID: 19887070 DOI: 10.1016/j.ijpara.2009.10.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/15/2009] [Accepted: 10/16/2009] [Indexed: 11/22/2022]
Abstract
Mitogen-activated protein kinase kinases (MAPKKs) are essential components of evolutionary conserved signalling modules that regulate a variety of fundamental cellular processes in response to environmental stimuli. To date, no MAPKK ortholog has been characterised in free-living or parasitic flatworm species. Here, we report the identification and molecular characterisation of two such molecules in the human parasitic cestode Echinococcus multilocularis, the causative agent of alveolar echinococcosis. Using degenerative PCR approaches as well as 3'- and 5'-rapid amplification of cDNA ends (RACE), the cDNAs encoding two different E. multilocularis MAPKKs, EmMKK1 and EmMKK2, have been identified and fully cloned. Structurally, EmMKK1 and EmMKK2 closely resemble members of the MKK3/6- and the MEK1/2-MAPKK sub-families, respectively, from a variety of vertebrate and invertebrate organisms, and contain all catalytically important residues of MAPKKs at the corresponding positions. By reverse transcriptase-PCR analyses, expression of the EmMKK2-encoding gene, emmkk2, was observed in the larval stages, metacestode and protoscolex while emmkk1 displayed a protoscolex-specific expression pattern. In yeast two-hybrid analyses, EmMKK1 strongly interacted with the previously identified Echinococcus MAPKK kinase EmRaf but not with the Erk-like MAP kinase EmMPK1 or the p38-like MAP kinase EmMPK2. EmMKK2, on the other hand, not only interacted with EmRaf and a member of the parasite's 14-3-3 protein family, but also with EmMPK1, which was confirmed by co-immunoprecipitation assays. Incubation of in vitro cultivated metacestode vesicles with small-molecule inhibitors of Raf- and MEK-kinases resulted in a marked de-phosphorylation of EmMPK1 and negatively affected parasite growth, but was ineffective in vesicle killing. Taken together, our results define EmRaf, EmMKK2 and EmMPK1 as the three components of the Erk-like E. multilocularis MAPK cascade module and provide a solid basis for further investigations into the role of Erk-like MAPK signalling in parasite development and stem cell function.
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271
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Yang X, Wang W, Coleman M, Orgil U, Feng J, Ma X, Ferl R, Turner JG, Xiao S. Arabidopsis 14-3-3 lambda is a positive regulator of RPW8-mediated disease resistance. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 60:539-50. [PMID: 19624472 DOI: 10.1111/j.1365-313x.2009.03978.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The RPW8 locus from Arabidopsis thaliana Ms-0 includes two functional paralogous genes (RPW8.1 and RPW8.2) and confers broad-spectrum resistance via the salicylic acid-dependent signaling pathway to the biotrophic fungal pathogens Golovinomyces spp. that cause powdery mildew diseases on multiple plant species. To identify proteins involved in regulation of the RPW8 protein function, a yeast two-hybrid screen was performed using RPW8.2 as bait. The 14-3-3 isoform lambda (designated GF14lambda) was identified as a potential RPW8.2 interactor. The RPW8.2-GF14lambda interaction was specific and engaged the C-terminal domain of RPW8.2, which was confirmed by pulldown assays. The physiological impact of the interaction was revealed by knocking down GF14lambda by T-DNA insertion, which compromised basal and RPW8-mediated resistance to powdery mildew. In addition, over-expression of GF14lambda resulted in hypersensitive response-like cell death and enhanced resistance to powdery mildew via the salicylic acid-dependent signaling pathway. The results from this study suggest that GF14lambda may positively regulate the RPW8.2 resistance function and play a role in enhancing basal resistance in Arabidopsis.
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Affiliation(s)
- Xiaohua Yang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Rockville, MD 20850, USA
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272
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Alvarado ME, Wasserman M. Analysis of phosphorylated proteins and inhibition of kinase activity during Giardia intestinalis excystation. Parasitol Int 2009; 59:54-61. [PMID: 19861170 DOI: 10.1016/j.parint.2009.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2009] [Revised: 10/08/2009] [Accepted: 10/10/2009] [Indexed: 11/24/2022]
Abstract
The parasite Giardia intestinalis undergoes a differentiation process that allows it to infect its mammal host. That process is excystation. We examined the importance of protein phosphorylation during the passage from cyst to trophozoite. Cysts obtained from patients with giardiasis were excysted in vitro and the soluble cytoplasmic proteins were analyzed during the three phases of the process, using a specific staining for phosphoproteins. We found two phosphorylated proteins and identified them with MALDI-TOF as 14-3-3 and Hsp70. Modifications were detected in both proteins, which could indicate a role in differentiation of the parasite. In addition, the inhibition of serine-threonine kinases during excystation specifically affected the cytokinesis of the excyzoite, thus inhibiting the completion of trophozoite formation.
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Affiliation(s)
- Magda E Alvarado
- Laboratorio de Investigaciones Básicas en Bioquímica, Departamento de Química, Universidad Nacional de Colombia, Bogotá calle 44 No 45-67 Bloque 10 nivel 4 Unidad Camilo Torres, Colombia
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273
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Herding Hippos: regulating growth in flies and man. Curr Opin Cell Biol 2009; 21:837-43. [PMID: 19846288 DOI: 10.1016/j.ceb.2009.09.010] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 09/17/2009] [Accepted: 09/21/2009] [Indexed: 01/15/2023]
Abstract
Control of cell number requires the coordinate regulation of cell proliferation and cell death. Studies in both the fly and mouse have identified the Hippo kinase pathway as a key signaling pathway that controls cell proliferation and apoptosis. Several studies have implicated the Hippo pathway in a variety of cancers. Recent studies have also revealed a role for the Hippo pathway in the control of cell fate decisions during development. In this review, we will cover the current model of Hippo signaling in development. We will explore the differences between the Hippo pathway in invertebrates and mammals, and focus on recent advances in understanding how this conserved pathway is regulated.
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274
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Abstract
Antigen receptors on the surface of B lymphocytes trigger adaptive immune responses after encountering their cognate antigens but also control a series of antigen-independent checkpoints during B cell development. These physiological processes are regulated by the expression and function of cell surface receptors, intracellular signaling molecules, and transcription factors. The function of these proteins can be altered by a dynamic array of post-translational modifications, using two interconnected mechanisms. These modifications can directly induce an altered conformational state in the protein target of the modification itself. In addition, they can create new binding sites for other protein partners, thereby contributing to where and when such multiple protein assemblies are activated within cells. As a new type of post-transcriptional regulator, microRNAs have emerged to influence the development and function of B cells by affecting the expression of target mRNAs.
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275
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Bokoch GM, Diebold B, Kim JS, Gianni D. Emerging evidence for the importance of phosphorylation in the regulation of NADPH oxidases. Antioxid Redox Signal 2009; 11:2429-41. [PMID: 19358632 PMCID: PMC2821133 DOI: 10.1089/ars.2009.2590] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The NADPH oxidase (Nox) enzyme family generates reactive oxygen species (ROS) that contribute to cell signaling, innate immune responses, proliferation, and transcription. The signaling mechanisms that regulate this important enzyme family are only beginning to be understood. Evidence is emerging which suggests that phosphorylation of Nox and/or their regulatory components may be important means of modulating their activity. We describe here the evidence for Nox regulation through the action of kinases, and speculate on how such regulatory mechanisms might contribute to the development of pathological disease states.
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Affiliation(s)
- Gary M Bokoch
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA.
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276
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Sun S, Wong EWP, Li MWM, Lee WM, Cheng CY. 14-3-3 and its binding partners are regulators of protein-protein interactions during spermatogenesis. J Endocrinol 2009; 202:327-36. [PMID: 19366886 PMCID: PMC2804912 DOI: 10.1677/joe-09-0041] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During spermatogenesis, spermiation takes place at the adluminal edge of the seminiferous epithelium at stage VIII of the epithelial cycle during which fully developed spermatids (i.e. spermatozoa) detach from the epithelium in adult rat testes. This event coincides with the migration of preleptotene/leptotene spermatocytes across the blood-testis barrier from the basal to the apical (or adluminal) compartment. At stage XIV of the epithelial cycle, Pachytene spermatocytes (diploid, 2n) differentiate into diplotene spermatocytes (tetraploid, 4n) in the apical compartment of the epithelium, which begin meiosis I to be followed by meiosis II to form spermatids (haploid, 1n) at stage XIV of the epithelial cycle. These spermatids, in turn, undergo extensive morphological changes and traverse the seminiferous epithelium until they differentiate into elongated spermatids. Thus, there are extensive changes at the Sertoli-Sertoli and Sertoli-germ cell interface via protein 'coupling' and 'uncoupling' between cell adhesion protein complexes, as well as changes in interactions between integral membrane proteins and their peripheral adaptors, regulatory protein kinases and phosphatases, and the cytoskeletal proteins. These precisely coordinated protein-protein interactions affect cell adhesion and cell movement. In this review, we focus on the 14-3-3 protein family, whose members have different binding partners in the seminiferous epithelium. Recent studies have illustrated that 14-3-3 affects protein-protein interactions in the seminiferous epithelium, and regulates cell adhesion possibly via its effects on intracellular protein trafficking and cell-polarity proteins. This review provides a summary on the latest findings regarding the role of 14-3-3 family of proteins and their potential implications on spermatogenesis. We also highlight research areas that deserve attentions by investigators.
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Affiliation(s)
- Shengyi Sun
- The Mary M Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10065, USA
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277
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Medina A, Brown E, Carr N, Ghahary A. Circulating monocytes have the capacity to be transdifferentiated into keratinocyte-like cells. Wound Repair Regen 2009; 17:268-77. [PMID: 19320896 DOI: 10.1111/j.1524-475x.2009.00457.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Transdifferentiation is a process in which the original commitment of a cell is changed to give rise to unexpected peripheral mature cells. Our previous report showed that circulating stem cells can generate keratinocyte-like cells (KLCs). However, it remains to be determined whether or not other peripheral blood mononuclear cells (PBMC) subsets have the potential to follow the same cell fate. In this study, the cell transdifferentiation of circulating CD14(+) monocytes into KLCs and their regulatory effect on matrix metalloproteinase-1 (MMP-1) expression in dermal fibroblasts were evaluated. The results showed that monocytes isolated from peripheral blood mononuclear cells have the capacity to generate KLCs. These transdifferentiated cells exhibited, along with a keratinocyte-like morphology, a characteristic profile consisting in stratifin(+), cytokeratins(+) (types I and II), CD14(low), and involucrin(+) on day 21 in culture. Similar to keratinocyte-conditioned media, KLC-derived conditioned media were able to induce an increase in the MMP-1 expression in dermal fibroblasts. This effect was significantly reduced by using 14-3-3 protein-depleted KLC-conditioned media. Our findings show the potential transdifferentiation of circulating CD14(+) monocytes into KLCs and their regulatory effect on MMP-1 expression in dermal fibroblasts.
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Affiliation(s)
- Abelardo Medina
- BC Professional Fire Fighters' Burn/Wound Healing Laboratory, Vancouver, Canada
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278
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van Heusden GPH. 14-3-3 Proteins: insights from genome-wide studies in yeast. Genomics 2009; 94:287-93. [PMID: 19631734 DOI: 10.1016/j.ygeno.2009.07.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 07/10/2009] [Accepted: 07/16/2009] [Indexed: 10/20/2022]
Abstract
14-3-3 proteins form a family of highly conserved, acidic, dimeric proteins. These proteins have been identified in all eukaryotic species investigated, often in multiple isoforms, up to 13 in the plant Arabidopsis thaliana. Hundreds of proteins, from diverse eukaryotic organisms, implicated in numerous cellular processes, have been identified as binding partners of 14-3-3 proteins. Therefore, the major activity of 14-3-3 proteins seems to be its ability to bind other intracellular proteins. Binding to 14-3-3 proteins may result in a conformational change of the protein required for its full activity or for inhibition of its activity, in interaction between two binding partners or in a different subcellular localization. Most of these interactions take place after phosphorylation of the binding partners. These observations suggest a major role of 14-3-3 proteins in regulatory networks. Here, the information on 14-3-3 proteins gathered from several genome- and proteome-wide studies in the yeast Saccharomyces cerevisiae is reviewed. In particular, the protein kinases responsible for the phosphorylation of 14-3-3 binding partners, phosphorylation of 14-3-3 proteins themselves, the transcriptional regulation of the 14-3-3 genes, and the role of 14-3-3 proteins in transcription are addressed. These large scale studies may help understand the function of 14-3-3 proteins at a cellular level rather than at the level of a single process.
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Affiliation(s)
- G Paul H van Heusden
- Section Molecular and Developmental Genetics, Institute of Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
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279
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Kuzelová K, Grebenová D, Pluskalová M, Kavan D, Halada P, Hrkal Z. Isoform-specific cleavage of 14-3-3 proteins in apoptotic JURL-MK1 cells. J Cell Biochem 2009; 106:673-81. [PMID: 19173300 DOI: 10.1002/jcb.22061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The proteins of 14-3-3 family are substantially involved in the regulation of many biological processes including the apoptosis. We studied the changes in the expression of five 14-3-3 isoforms (beta, gamma, epsilon, tau, and zeta) during the apoptosis of JURL-MK1 and K562 cells. The expression level of all these proteins markedly decreased in relation with the apoptosis progression and all isoforms underwent truncation, which probably corresponds to the removal of several C-terminal amino acids. The observed 14-3-3 modifications were partially blocked by caspase-3 inhibition. In addition to caspases, a non-caspase protease is likely to contribute to 14-3-3's cleavage in an isoform-specific manner. While 14-3-3 gamma seems to be cleaved mainly by caspase-3, the alternative mechanism is essentially involved in the case of 14-3-3 tau, and a combined effect was observed for the isoforms epsilon, beta, and zeta. We suggest that the processing of 14-3-3 proteins could form an integral part of the programmed cell death or at least of some apoptotic pathways.
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Affiliation(s)
- Katerina Kuzelová
- Department of Cellular Biochemistry, Institute of Hematology and Blood Transfusion, Prague 2, Czech Republic.
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280
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Rampakakis E, Arvanitis DN, Di Paola D, Zannis-Hadjopoulos M. Metazoan origins of DNA replication: regulation through dynamic chromatin structure. J Cell Biochem 2009; 106:512-20. [PMID: 19173303 DOI: 10.1002/jcb.22070] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
DNA replication in eukaryotes is initiated at multiple replication origins distributed over the entire genome, which are normally activated once per cell cycle. Due to the complexity of the metazoan genome, the study of metazoan replication origins and their activity profiles has been less advanced than in simpler genome systems. DNA replication in eukaryotes involves many protein-protein and protein-DNA interactions, occurring in multiple stages. As in prokaryotes, control over the timing and frequency of initiation is exerted at the initiation site. A prerequisite for understanding the regulatory mechanisms of eukaryotic DNA replication is the identification and characterization of the cis-acting sequences that serve as replication origins and the trans-acting factors (proteins) that interact with them. Furthermore, in order to understand how DNA replication may become deregulated in malignant cells, the distinguishing features between normal and malignant origins of DNA replication as well as the proteins that interact with them must be determined. Based on advances that were made using simple genome model systems, several proteins involved in DNA replication have been identified. This review summarizes the current findings about metazoan origins of DNA replication and their interacting proteins as well as the role of chromatin structure in their regulation. Furthermore, progress in origin identification and isolation procedures as well as potential mechanisms to inhibit their activation in cancer development and progression are discussed.
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Affiliation(s)
- E Rampakakis
- Department of Biochemistry, Goodman Cancer Centre, Montreal, Quebec, Canada
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281
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Serine 58 of 14-3-3zeta is a molecular switch regulating ASK1 and oxidant stress-induced cell death. Mol Cell Biol 2009; 29:4167-76. [PMID: 19451227 DOI: 10.1128/mcb.01067-08] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Oxidant stress is a ubiquitous stressor with negative impacts on multiple cell types. ASK1 is a central mediator of oxidant injury, but while mechanisms of its inhibition, such as sequestration by 14-3-3 proteins and thioredoxin, have been identified, mechanisms of activation have remained obscure and the signaling pathways regulating this are not clear. Here, we report that phosphorylation of 14-3-3zeta at serine 58 (S58) is dynamically regulated in the cell and that the phosphorylation status of S58 is a critical factor regulating oxidant stress-induced cell death. Phosphorylation of S58 releases ASK1 from 14-3-3zeta, and ASK1 then activates stress-activated protein kinases, leading to cell death. While several members of the mammalian sterile 20 (Mst) family of kinases can phosphorylate S58 when overexpressed, we identify Ste20/oxidant stress response kinase 1 (SOK-1), an Mst family member known to be activated by oxidant stress, as a central endogenous regulator of S58 phosphorylation and thereby of ASK1-mediated cell death. Our findings identify a novel pathway that regulates ASK1 activation and oxidant stress-induced cell death.
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282
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Silhan J, Vacha P, Strnadova P, Vecer J, Herman P, Sulc M, Teisinger J, Obsilova V, Obsil T. 14-3-3 protein masks the DNA binding interface of forkhead transcription factor FOXO4. J Biol Chem 2009; 284:19349-60. [PMID: 19416966 DOI: 10.1074/jbc.m109.002725] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The role of 14-3-3 proteins in the regulation of FOXO forkhead transcription factors is at least 2-fold. First, the 14-3-3 binding inhibits the interaction between the FOXO and the target DNA. Second, the 14-3-3 proteins prevent nuclear reimport of FOXO factors by masking their nuclear localization signal. The exact mechanisms of these processes are still unclear, mainly due to the lack of structural data. In this work, we used fluorescence spectroscopy to investigate the mechanism of the 14-3-3 protein-dependent inhibition of FOXO4 DNA-binding properties. Time-resolved fluorescence measurements revealed that the 14-3-3 binding affects fluorescence properties of 5-(((acetylamino)ethyl)amino) naphthalene-1-sulfonic acid moiety attached at four sites within the forkhead domain of FOXO4 that represent important parts of the DNA binding interface. Observed changes in 5-(((acetylamino)ethyl)amino) naphthalene-1-sulfonic acid fluorescence strongly suggest physical contacts between the 14-3-3 protein and labeled parts of the FOXO4 DNA binding interface. The 14-3-3 protein binding, however, does not cause any dramatic conformational change of FOXO4 as documented by the results of tryptophan fluorescence experiments. To build a realistic model of the FOXO4.14-3-3 complex, we measured six distances between 14-3-3 and FOXO4 using Förster resonance energy transfer time-resolved fluorescence experiments. The model of the complex suggests that the forkhead domain of FOXO4 is docked within the central channel of the 14-3-3 protein dimer, consistent with our hypothesis that 14-3-3 masks the DNA binding interface of FOXO4.
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Affiliation(s)
- Jan Silhan
- Departments of Physical and Macromolecular Chemistry, Charles University, 12843 Prague
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283
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Li Y, Kang X, Guo K, Li X, Gao D, Cui J, Sun L, Yang P, Liu Y. Proteome alteration of early-stage differentiation of mouse embryonic stem cells into hepatocyte-like cells. Electrophoresis 2009; 30:1431-40. [DOI: 10.1002/elps.200800836] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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284
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Abstract
AMP-activated protein kinase (AMPK) is a key regulator of cellular and whole-body energy homeostasis. Recently, 12 AMPK-related kinases (BRSK1, BRSK2, NUAK1, NUAK2, QIK, QSK, SIK, MARK1, MARK2, MARK3, MARK4 and MELK) were identified that are closely related by sequence homology to the catalytic domain of AMPK. The protein kinase LKB1 acts as a master upstream kinase activating AMPK and 11 of the AMPK-related kinases by phosphorylation of a conserved threonine residue in their T-loop region. Further sequence analyses have identified the eight-member SNRK kinase family as distant relatives of AMPK. However, only one of these is phosphorylated and activated by LKB1. Although much is known about AMPK, many of the AMPK-related kinases remain largely uncharacterized. This review outlines the general similarities in structure and function of the AMPK-related kinases before examining the specific characteristics of each, including a brief discussion of the SNRK family.
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Affiliation(s)
- N J Bright
- Cellular Stress Group, MRC Clinical Sciences Centre, London, UK
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285
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Interaction of hookworm 14-3-3 with the forkhead transcription factor DAF-16 requires intact Akt phosphorylation sites. Parasit Vectors 2009; 2:21. [PMID: 19393088 PMCID: PMC2683825 DOI: 10.1186/1756-3305-2-21] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 04/24/2009] [Indexed: 01/29/2023] Open
Abstract
Background Third-stage infective larvae (L3) of hookworms are in an obligatory state of developmental arrest that ends upon entering the definitive host, where they receive a signal that re-activates development. Recovery from the developmentally arrested dauer stage of Caenorhabditis elegans is analogous to the resumption of development during hookworm infection. Insulin-like signaling (ILS) mediates recovery from arrest in C. elegans and activation of hookworm dauer L3. In C. elegans, phosphorylation of the forkhead transcription factor DAF-16 in response to ILS creates binding cites for the 14-3-3 protein Ce-FTT-2, which translocates DAF-16 out of the nucleus, resulting in resumption of reproductive development. Results To determine if hookworm 14-3-3 proteins play a similar role in L3 activation, hookworm FTT-2 was identified and tested for its ability to interact with A. caninum DAF-16 in vitro. The Ac-FTT-2 amino acid sequence was 91% identical to the Ce-FTT-2, and was most closely related to FTT-2 from other nematodes. Ac-FTT-2 was expressed in HEK 293T cells, and was recognized by an antibody against human 14-3-3β isoform. Reciprocal co-immunoprecipitations using anti-epitope tag antibodies indicated that Ac-FTT-2 interacts with Ac-DAF-16 when co-expressed in serum-stimulated HEK 293T cells. This interaction requires intact Akt consensus phosphorylation sites at serine107 and threonine312, but not serine381. Ac-FTT-2 was undetectable by Western blot in excretory/secretory products from serum-stimulated (activated) L3 or adult A. caninum. Conclusion The results indicate that Ac-FTT-2 interacts with DAF-16 in a phosphorylation-site dependent manner, and suggests that Ac-FTT-2 mediates activation of L3 by binding Ac-DAF-16 during hookworm infection.
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286
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Abstract
The co-activator Yorkie (Yki) mediates transcriptional regulation effected by the Drosophila Fat-Warts (Wts)-Hippo (Hpo) pathways. Yki is inhibited by Wts-mediated phosphorylation, and a Wts phosphorylation site at Ser168 has been identified. Here we identify two additional Wts phosphorylation sites on Yki, and examine the respective contribution of all three sites to Yki nuclear localization and activity. Our results show that although Ser168 is the most critical site, all three phosphorylation sites influence Yki localization and activity in vivo, and can be sites of regulation by Wts. Thus, investigations of the role of Yki and its mammalian homolog Yes-associated protein (YAP) in development and oncogenesis should include evaluations of additional sites. The WW domains of Yki are not required for its phosphorylation, but instead are positively required for its activity. We also identify two potential sites of phosphorylation by an unknown kinase, which could influence phosphorylation of Ser168 by Wts, suggesting that there are additional mechanisms for regulating Yki/YAP activity.
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287
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Szczerba MW, Britto DT, Kronzucker HJ. K+ transport in plants: physiology and molecular biology. JOURNAL OF PLANT PHYSIOLOGY 2009; 166:447-66. [PMID: 19217185 DOI: 10.1016/j.jplph.2008.12.009] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Revised: 11/10/2008] [Accepted: 12/10/2008] [Indexed: 05/06/2023]
Abstract
Potassium (K(+)) is an essential nutrient and the most abundant cation in plant cells. Plants have a wide variety of transport systems for K(+) acquisition, catalyzing K(+) uptake across a wide spectrum of external concentrations, and mediating K(+) movement within the plant as well as its efflux into the environment. K(+) transport responds to variations in external K(+) supply, to the presence of other ions in the root environment, and to a range of plant stresses, via Ca(2+) signaling cascades and regulatory proteins. This review will summarize the molecular identities of known K(+) transporters, and examine how this information supports physiological investigations of K(+) transport and studies of plant stress responses in a changing environment.
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Affiliation(s)
- Mark W Szczerba
- Department of Plant Sciences, University of California, Davis, 1 Shields Ave., Davis, CA 95616, USA.
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288
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Hunter RW, Mackintosh C, Hers I. Protein kinase C-mediated phosphorylation and activation of PDE3A regulate cAMP levels in human platelets. J Biol Chem 2009; 284:12339-48. [PMID: 19261611 DOI: 10.1074/jbc.m807536200] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The elevation of [cAMP](i) is an important mechanism of platelet inhibition and is regulated by the opposing activity of adenylyl cyclase and phosphodiesterase (PDE). In this study, we demonstrate that a variety of platelet agonists, including thrombin, significantly enhance the activity of PDE3A in a phosphorylation-dependent manner. Stimulation of platelets with the PAR-1 agonist SFLLRN resulted in rapid and transient phosphorylation of PDE3A on Ser(312), Ser(428), Ser(438), Ser(465), and Ser(492), in parallel with the PKC (protein kinase C) substrate, pleckstrin. Furthermore, phosphorylation and activation of PDE3A required the activation of PKC, but not of PI3K/PKB, mTOR/p70S6K, or ERK/RSK. Activation of PKC by phorbol esters also resulted in phosphorylation of the same PDE3A sites in a PKC-dependent, PKB-independent manner. This was further supported by the finding that IGF-1, which strongly activates PI3K/PKB, but not PKC, did not regulate PDE3A. Platelet activation also led to a PKC-dependent association between PDE3A and 14-3-3 proteins. In contrast, cAMP-elevating agents such as PGE(1) and forskolin-induced phosphorylation of Ser(312) and increased PDE3A activity, but did not stimulate 14-3-3 binding. Finally, complete antagonism of PGE(1)-evoked cAMP accumulation by thrombin required both G(i) and PKC activation. Together, these results demonstrate that platelet activation stimulates PKC-dependent phosphorylation of PDE3A on Ser(312), Ser(428), Ser(438), Ser(465), and Ser(492) leading to a subsequent increase in cAMP hydrolysis and 14-3-3 binding.
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Affiliation(s)
- Roger W Hunter
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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289
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Paul AL, Liu L, McClung S, Laughner B, Chen S, Ferl RJ. Comparative Interactomics: Analysis of Arabidopsis 14-3-3 Complexes Reveals Highly Conserved 14-3-3 Interactions between Humans and Plants. J Proteome Res 2009; 8:1913-24. [DOI: 10.1021/pr8008644] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Anna-Lisa Paul
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
| | - Li Liu
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
| | - Scott McClung
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
| | - Beth Laughner
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
| | - Sixue Chen
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
| | - Robert J. Ferl
- Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, Department of Botany, University of Florida, Gainesville, Florida 32611, and Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida 32610-3622
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290
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Díaz-Moreno I, Hollingworth D, Frenkiel TA, Kelly G, Martin S, Howell S, García-Mayoral M, Gherzi R, Briata P, Ramos A. Phosphorylation-mediated unfolding of a KH domain regulates KSRP localization via 14-3-3 binding. Nat Struct Mol Biol 2009; 16:238-46. [PMID: 19198587 PMCID: PMC2858377 DOI: 10.1038/nsmb.1558] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 01/13/2009] [Indexed: 12/20/2022]
Abstract
The AU-rich element (ARE)-mediated mRNA-degradation activity of the RNA binding K-homology splicing regulator protein (KSRP) is regulated by phosphorylation of a serine within its N-terminal KH domain (KH1). In the cell, phosphorylation promotes the interaction of KSRP and 14-3-3zeta protein and impairs the ability of KSRP to promote the degradation of its RNA targets. Here we examine the molecular details of this mechanism. We report that phosphorylation leads to the unfolding of the structurally atypical and unstable KH1, creating a site for 14-3-3zeta binding. Using this site, 14-3-3zeta discriminates between phosphorylated and unphosphorylated KH1, driving the nuclear localization of KSRP. 14-3-3zeta -KH1 interaction regulates the mRNA-decay activity of KSRP by sequestering the protein in a separate functional pool. This study demonstrates how an mRNA-degradation pathway is connected to extracellular signaling networks through the reversible unfolding of a protein domain.
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Affiliation(s)
- Irene Díaz-Moreno
- Molecular Structure Division, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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291
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Belli N, Faleiros R, Firmino K, Masui D, Leone F, McNamara J, Furriel R. Na,K-ATPase activity and epithelial interfaces in gills of the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae). Comp Biochem Physiol A Mol Integr Physiol 2009; 152:431-9. [DOI: 10.1016/j.cbpa.2008.11.017] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 11/19/2008] [Accepted: 11/20/2008] [Indexed: 11/27/2022]
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292
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Liang S, Yu Y, Yang P, Gu S, Xue Y, Chen X. Analysis of the protein complex associated with 14-3-3 epsilon by a deuterated-leucine labeling quantitative proteomics strategy. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:627-34. [DOI: 10.1016/j.jchromb.2009.01.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 01/06/2009] [Accepted: 01/07/2009] [Indexed: 10/21/2022]
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293
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Zuzarte M, Heusser K, Renigunta V, Schlichthörl G, Rinné S, Wischmeyer E, Daut J, Schwappach B, Preisig-Müller R. Intracellular traffic of the K+ channels TASK-1 and TASK-3: role of N- and C-terminal sorting signals and interaction with 14-3-3 proteins. J Physiol 2009; 587:929-52. [PMID: 19139046 PMCID: PMC2673767 DOI: 10.1113/jphysiol.2008.164756] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2008] [Accepted: 01/08/2009] [Indexed: 01/03/2023] Open
Abstract
The two-pore-domain potassium channels TASK-1 (KCNK3) and TASK-3 (KCNK9) modulate the electrical activity of neurons and many other cell types. We expressed TASK-1, TASK-3 and related reporter constructs in Xenopus oocytes, mammalian cell lines and various yeast strains to study the mechanisms controlling their transport to the surface membrane and the role of 14-3-3 proteins. We measured potassium currents with the voltage-clamp technique and fused N- and C-terminal fragments of the channels to various reporter proteins to study changes in subcellular localisation and surface expression. Mutational analysis showed that binding of 14-3-3 proteins to the extreme C-terminus of TASK-1 and TASK-3 masks a tri-basic motif, KRR, which differs in several important aspects from canonical arginine-based (RxR) or lysine-based (KKxx) retention signals. Pulldown experiments with GST fusion proteins showed that the KRR motif in the C-terminus of TASK-3 channels was able to bind to COPI coatomer. Disabling the binding of 14-3-3, which exposes the KRR motif, caused localisation of the GFP-tagged channel protein mainly to the Golgi complex. TASK-1 and TASK-3 also possess a di-basic N-terminal retention signal, KR, whose function was found to be independent of the binding of 14-3-3. Suppression of channel surface expression with dominant-negative channel mutants revealed that interaction with 14-3-3 has no significant effect on the dimeric assembly of the channels. Our results give a comprehensive description of the mechanisms by which 14-3-3 proteins, together with N- and C-terminal sorting signals, control the intracellular traffic of TASK-1 and TASK-3.
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Affiliation(s)
- Marylou Zuzarte
- Institute of Physiology, Marburg University, Deutschhausstrasse 2, 35037 Marburg, Germany
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294
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Phosphorylation-dependent binding of 14-3-3 terminates signalling by the Gab2 docking protein. EMBO J 2009; 27:2305-16. [PMID: 19172738 DOI: 10.1038/emboj.2008.159] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Grb2-associated binder (Gab)2 functions downstream of a variety of receptor and cytoplasmic tyrosine kinases as a docking platform for specific signal transducers and performs important functions in both normal physiology and oncogenesis. Gab2 signalling is promoted by its association with specific receptors through the adaptor Grb2. However, the molecular mechanisms that attenuate Gab2 signals have remained unclear. We now demonstrate that growth factor-induced phosphorylation of Gab2 on two residues, S210 and T391, leads to recruitment of 14-3-3 proteins. Together, these events mediate negative-feedback regulation, as Gab2(S210A/T391A) exhibits sustained receptor association and signalling and promotes cell proliferation and transformation. Importantly, introduction of constitutive 14-3-3-binding sites into Gab2 renders it refractory to receptor activation, demonstrating that site-selective binding of 14-3-3 proteins is sufficient to terminate Gab2 signalling. Furthermore, this is associated with reduced binding of Grb2. This leads to a model where signal attenuation occurs because 14-3-3 promotes dissociation of Gab2 from Grb2, and thereby uncouples Gab2 from the receptor complex. This represents a novel regulatory mechanism with implications for diverse tyrosine kinase signalling systems.
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295
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Barry EF, Felquer FA, Powell JA, Biggs L, Stomski FC, Urbani A, Ramshaw H, Hoffmann P, Wilce MC, Grimbaldeston MA, Lopez AF, Guthridge MA. 14-3-3:Shc scaffolds integrate phosphoserine and phosphotyrosine signaling to regulate phosphatidylinositol 3-kinase activation and cell survival. J Biol Chem 2009; 284:12080-90. [PMID: 19218246 DOI: 10.1074/jbc.m807637200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Integrated cascades of protein tyrosine and serine/threonine phosphorylation play essential roles in transducing signals in response to growth factors and cytokines. How adaptor or scaffold proteins assemble signaling complexes through both phosphotyrosine and phosphoserine/threonine residues to regulate specific signaling pathways and biological responses is unclear. We show in multiple cell types that endogenous 14-3-3zeta is phosphorylated on Tyr(179) in response to granulocyte macrophage colony-stimulating factor. Importantly, 14-3-3zeta can function as an intermolecular bridge that couples to phosphoserine residues and also directly binds the SH2 domain of Shc via Tyr(179). The assembly of these 14-3-3:Shc scaffolds is specifically required for the recruitment of a phosphatidylinositol 3-kinase signaling complex and the regulation of CTL-EN cell survival in response to cytokine. The biological significance of these findings was further demonstrated using primary bone marrow-derived mast cells from 14-3-3zeta(-/-) mice. We show that cytokine was able to promote Akt phosphorylation and viability of primary mast cells derived from 14-3-3zeta(-/-) mice when reconstituted with wild type 14-3-3zeta, but the Akt phosphorylation and survival response was reduced in cells reconstituted with the Y179F mutant. Together, these results show that 14-3-3:Shc scaffolds can act as multivalent signaling nodes for the integration of both phosphoserine/threonine and phosphotyrosine pathways to regulate specific cellular responses.
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Affiliation(s)
- Emma F Barry
- Cell Growth and Differentiation Laboratory, Division of Human Immunology, Hanson Institute, Institute of Medical and Veterinary Science, Frome Road, Adelaide, South Australia 5000, Australia
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296
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Acuto O, Di Bartolo V, Michel F. Tailoring T-cell receptor signals by proximal negative feedback mechanisms. Nat Rev Immunol 2009; 8:699-712. [PMID: 18728635 DOI: 10.1038/nri2397] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The T-cell receptor (TCR) signalling machinery is central in determining the response of a T cell (establishing immunity or tolerance) following exposure to antigen. This process is made difficult by the narrow margin of self and non-self discrimination, and by the complexity of the genetic programmes that are induced for each outcome. Recent studies have identified novel negative feedback mechanisms that are rapidly induced by TCR engagement and that have key roles in the regulation of signal triggering and propagation. In vitro and in vivo data suggest that they are important in determining ligand discrimination by the TCR and in regulating signal output in response to antigen.
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Affiliation(s)
- Oreste Acuto
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
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297
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Chevalier D, Morris ER, Walker JC. 14-3-3 and FHA domains mediate phosphoprotein interactions. ANNUAL REVIEW OF PLANT BIOLOGY 2009; 60:67-91. [PMID: 19575580 DOI: 10.1146/annurev.arplant.59.032607.092844] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Many aspects of plant growth and development require specific protein interactions to carry out biochemical and cellular functions. Several proteins mediate these interactions, two of which specifically recognize phosphoproteins: 14-3-3 proteins and proteins with FHA domains. These are the only phosphobinding domains identified in plants. Both domains are present in animals and plants, and are used by plant proteins to regulate metabolic, developmental, and signaling pathways. 14-3-3s regulate sugar metabolism, proton gradients, and control transcription factor localization. FHA domains are modular domains often found in multidomain proteins that are involved in signal transduction and plant development.
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Affiliation(s)
- David Chevalier
- Division of Biological Sciences and Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, USA
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298
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Prescott GR, Jenkins RE, Walsh CM, Morgan A. Phosphorylation of cysteine string protein on Serine 10 triggers 14-3-3 protein binding. Biochem Biophys Res Commun 2008; 377:809-14. [DOI: 10.1016/j.bbrc.2008.10.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 10/11/2008] [Indexed: 10/21/2022]
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299
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Sunyer B, Diao WF, Kang SU, An G, Boddul S, Lubec G. Cognitive Enhancement by SGS742 in OF1 Mice Is Linked to Specific Hippocampal Protein Expression. J Proteome Res 2008; 7:5237-53. [DOI: 10.1021/pr800594b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Berta Sunyer
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Wei-Fei Diao
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Sung Ung Kang
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gunyong An
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Sanjay Boddul
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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300
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Du Y, Khuri FR, Fu H. A homogenous luminescent proximity assay for 14-3-3 interactions with both phosphorylated and nonphosphorylated client peptides. CURRENT CHEMICAL GENOMICS 2008; 2:40-7. [PMID: 20161842 PMCID: PMC2803432 DOI: 10.2174/1875397300802010040] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Revised: 09/01/2008] [Accepted: 09/02/2008] [Indexed: 01/03/2023]
Abstract
The 14-3-3 proteins are a family of dimeric eukaryotic proteins that mediate both phosphorylation-dependent and -independent protein-protein interactions. Through these interactions, 14-3-3 proteins participate in the regulation of a wide range of cellular processes, including cell proliferation, cell cycle progression, and apoptosis. Because of their fundamental importance, 14-3-3 proteins have also been implicated in a variety of diseases, including cancer and neurodegenerative disorders. In order to monitor 14-3-3/client protein interactions for the discovery of small molecule 14-3-3 modulators, we have designed and optimized 14-3-3 protein binding assays based on the amplified luminescent proximity homogeneous assay (AlphaScreen) technology. Using the interaction of 14-3-3 with a phosphorylated Raf-1 peptide and a nonphosphorylated R18 peptide as model systems, we have established homogenous “add-and-measure” high-throughput screening assays. Both assays achieved robust performance with S/B ratios above 7 and Z’ factors above 0.7. Application of the known antagonistic peptides in our studies further validated the assay for screening of chemical compound libraries to identify small molecules that can modulate 14-3-3 protein-protein interactions.
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Affiliation(s)
- Yuhong Du
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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