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Homan CC, Kumar R, Nguyen LS, Haan E, Raymond FL, Abidi F, Raynaud M, Schwartz CE, Wood SA, Gecz J, Jolly LA. Mutations in USP9X are associated with X-linked intellectual disability and disrupt neuronal cell migration and growth. Am J Hum Genet 2014; 94:470-8. [PMID: 24607389 DOI: 10.1016/j.ajhg.2014.02.004] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 02/13/2014] [Indexed: 11/17/2022] Open
Abstract
With a wealth of disease-associated DNA variants being recently reported, the challenges of providing their functional characterization are mounting. Previously, as part of a large systematic resequencing of the X chromosome in 208 unrelated families with nonsyndromic X-linked intellectual disability, we identified three unique variants (two missense and one protein truncating) in USP9X. To assess the functional significance of these variants, we took advantage of the Usp9x knockout mouse we generated. Loss of Usp9x causes reduction in both axonal growth and neuronal cell migration. Although overexpression of wild-type human USP9X rescued these defects, all three USP9X variants failed to rescue axonal growth, caused reduced USP9X protein localization in axonal growth cones, and (in 2/3 variants) failed to rescue neuronal cell migration. Interestingly, in one of these families, the proband was subsequently identified to have a microdeletion encompassing ARID1B, a known ID gene. Given our findings it is plausible that loss of function of both genes contributes to the individual's phenotype. This case highlights the complexity of the interpretations of genetic findings from genome-wide investigations. We also performed proteomics analysis of neurons from both the wild-type and Usp9x knockout embryos and identified disruption of the cytoskeleton as the main underlying consequence of the loss of Usp9x. Detailed clinical assessment of all three families with USP9X variants identified hypotonia and behavioral and morphological defects as common features in addition to ID. Together our data support involvement of all three USP9X variants in ID in these families and provide likely cellular and molecular mechanisms involved.
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Affiliation(s)
- Claire C Homan
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia
| | - Raman Kumar
- Women's and Children's Health Research Institute, North Adelaide, SA 5006, Australia; Discipline of Medicine, University of Adelaide, Adelaide, SA 5005, Australia; School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia
| | - Lam Son Nguyen
- School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia
| | - Eric Haan
- School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia; South Australian Clinical Genetics Service, SA Pathology at Women's and Children's Hospital, North Adelaide, SA 5006, Australia
| | - F Lucy Raymond
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Fatima Abidi
- J.C. Self Research Institute, Greenwood Genetics Centre, Greenwood, SC 29646, USA
| | - Martine Raynaud
- CHRU de Tours, Service de Génétique, Tours 37000, France; Inserm U930, UMR Imagerie et Cerveau, Tours 37000, France
| | - Charles E Schwartz
- J.C. Self Research Institute, Greenwood Genetics Centre, Greenwood, SC 29646, USA
| | - Stephen A Wood
- Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Jozef Gecz
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia; Women's and Children's Health Research Institute, North Adelaide, SA 5006, Australia; School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia; Robinson Institute, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Lachlan A Jolly
- School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia; Robinson Institute, University of Adelaide, Adelaide, SA 5005, Australia.
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252
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Roy LO, Poirier MB, Fortin D. Transforming growth factor-beta and its implication in the malignancy of gliomas. Target Oncol 2014; 10:1-14. [PMID: 24590691 DOI: 10.1007/s11523-014-0308-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 02/18/2014] [Indexed: 12/13/2022]
Abstract
Malignant gliomas are the most common type of primary malignant brain tumors. They are characterized by enhanced growing capabilities, neoangiogenic proliferation, and extensive infiltration of the brain parenchyma, which make their complete surgical resection impossible. Together with transient and refractory responses to standard therapy, these aggressive neoplasms are incurable and present a median survival of 12 to 14 months. Transforming growth factor-beta (TGF-β) is a pleiotropic cytokine of which two of the three isoforms expressed in humans have been shown to be overexpressed proportionally to the histologic grade of glioma malignancy. The increase of chromosomal aberrations and genetic mutations observed in glioma cells turns TGF-β into an oncogene. For that reason, it plays critical roles in glioma progression through induction of several genes implicated in many carcinogenic processes such as proliferation, angiogenesis, and invasion. Consequently, investigators have begun developing innovative therapeutics targeting this growth factor or its signaling pathway in an attempt to hinder TGF-β's appalling effects in order to refine the treatment of malignant gliomas and improve their prognosis. In this paper, we extensively review the TGF-β-induced oncogenic pathways and discuss the diverse new molecules targeting this growth factor.
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Affiliation(s)
- Laurent-Olivier Roy
- Department of Pharmacology, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, Quebec, J1H 5N4, Canada
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253
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Xue J, Lin X, Chiu WT, Chen YH, Yu G, Liu M, Feng XH, Sawaya R, Medema RH, Hung MC, Huang S. Sustained activation of SMAD3/SMAD4 by FOXM1 promotes TGF-β-dependent cancer metastasis. J Clin Invest 2014; 124:564-79. [PMID: 24382352 DOI: 10.1172/jci71104] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/18/2013] [Indexed: 12/22/2022] Open
Abstract
A key feature of TGF-β signaling activation in cancer cells is the sustained activation of SMAD complexes in the nucleus; however, the drivers of SMAD activation are poorly defined. Here, using human and mouse breast cancer cell lines, we found that oncogene forkhead box M1 (FOXM1) interacts with SMAD3 to sustain activation of the SMAD3/SMAD4 complex in the nucleus. FOXM1 prevented the E3 ubiquitin-protein ligase transcriptional intermediary factor 1 γ (TIF1γ) from binding SMAD3 and monoubiquitinating SMAD4, which stabilized the SMAD3/SMAD4 complex. Loss of FOXM1 abolished TGF-β-induced SMAD3/SMAD4 formation. Moreover, the interaction of FOXM1 and SMAD3 promoted TGF-β/SMAD3-mediated transcriptional activity and target gene expression. We found that FOXM1/SMAD3 interaction was required for TGF-β-induced breast cancer invasion, which was the result of SMAD3/SMAD4-dependent upregulation of the transcription factor SLUG. Importantly, the function of FOXM1 in TGF-β-induced invasion was not dependent on FOXM1's transcriptional activity. Knockdown of SMAD3 diminished FOXM1-induced metastasis. Furthermore, FOXM1 levels correlated with activated TGF-β signaling and metastasis in human breast cancer specimens. Together, our data indicate that FOXM1 promotes breast cancer metastasis by increasing nuclear retention of SMAD3 and identify crosstalk between FOXM1 and TGF-β/SMAD3 pathways. This study highlights the critical interaction of FOXM1 and SMAD3 for controlling TGF-β signaling during metastasis.
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254
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Isono E, Nagel MK. Deubiquitylating enzymes and their emerging role in plant biology. FRONTIERS IN PLANT SCIENCE 2014; 5:56. [PMID: 24600466 PMCID: PMC3928566 DOI: 10.3389/fpls.2014.00056] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 02/05/2014] [Indexed: 05/18/2023]
Abstract
Ubiquitylation is a reversible post-translational modification that is involved in various cellular pathways and that thereby regulates various aspects of plant biology. For a long time, functional studies of ubiquitylation have focused on the function of ubiquitylating enzymes, especially the E3 ligases, rather than deubiquitylating enzymes (DUBs) or ubiquitin isopeptidases, enzymes that hydrolyze ubiquitin chains. One reason may be the smaller number of DUBs in comparison to E3 ligases, implying the broader substrate specificities of DUBs and the difficulties to identify the direct targets. However, recent studies have revealed that DUBs also actively participate in controlling cellular events and thus play pivotal roles in plant development and growth. DUBs are also essential for processing ubiquitin precursors and are important for recycling ubiquitin molecules from target proteins prior to their degradation and thereby maintaining the free ubiquitin pool in the cell. Here, we will discuss the five different DUB families (USP/UBP, UCH, JAMM, OTU, and MJD) and their known biochemical and physiological roles in plants.
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Affiliation(s)
- Erika Isono
- *Correspondence: Erika Isono, Department of Plant Systems Biology, Technische Universität München, Emil-Ramann-Strasse 4, D-85354 Freising, Germany e-mail:
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255
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Platta HW, Hagen S, Reidick C, Erdmann R. The peroxisomal receptor dislocation pathway: to the exportomer and beyond. Biochimie 2013; 98:16-28. [PMID: 24345375 DOI: 10.1016/j.biochi.2013.12.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 12/05/2013] [Indexed: 12/29/2022]
Abstract
The biogenesis of peroxisomes is an ubiquitin-dependent process. In particular, the import of matrix proteins into the peroxisomal lumen requires the modification of import receptors with ubiquitin. The matrix proteins are synthesized on free polyribosomes in the cytosol and are recognized by import receptors via a peroxisomal targeting sequence (PTS). Subsequent to the transport of the receptor/cargo-complex to the peroxisomal membrane and the release of the cargo into the peroxisomal lumen, the PTS-receptors are exported back to the cytosol for further rounds of matrix protein import. The exportomer represents the molecular machinery required for the retrotranslocation of the PTS-receptors. It comprises enzymes for the ubiquitination as well as for the ATP-dependent extraction of the PTS-receptors from the peroxisomal membrane. Furthermore, recent evidence indicates a mechanistic interconnection of the ATP-dependent removal of the PTS-receptors with the translocation of the matrix protein into the organellar lumen. Interestingly, the components of the peroxisomal exportomer seem also to be involved in cellular tasks that are distinct from the ubiquitination and dislocation of the peroxisomal PTS-receptors. This includes work that indicates a central function of this machinery in the export of peroxisomal matrix proteins in plants, while a subset of exportomer components is involved in the meiocyte formation in some fungi, the peroxisome-chloroplast contact during photorespiration in plants and possibly even the selective degradation of peroxisomes via pexophagy. In this review, we want to discuss the central role of the exportomer during matrix protein import, but also highlight distinct roles of exportomer constituents in additional cellular processes. This article is part of a Special Issue entitled: Peroxisomes: biogenesis, functions and diseases.
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Affiliation(s)
- Harald W Platta
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
| | - Stefanie Hagen
- Systembiochemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Christina Reidick
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Ralf Erdmann
- Systembiochemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
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256
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Kulkarni A, Oza J, Yao M, Sohail H, Ginjala V, Tomas-Loba A, Horejsi Z, Tan AR, Boulton SJ, Ganesan S. Tripartite Motif-containing 33 (TRIM33) protein functions in the poly(ADP-ribose) polymerase (PARP)-dependent DNA damage response through interaction with Amplified in Liver Cancer 1 (ALC1) protein. J Biol Chem 2013; 288:32357-32369. [PMID: 23926104 PMCID: PMC3820871 DOI: 10.1074/jbc.m113.459164] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 08/06/2013] [Indexed: 12/17/2022] Open
Abstract
Activation of poly(ADP-ribose) polymerase (PARP) near sites of DNA breaks facilitates recruitment of DNA repair proteins and promotes chromatin relaxation in part through the action of chromatin-remodeling enzyme Amplified in Liver Cancer 1 (ALC1). Through proteomic analysis we find that ALC1 interacts after DNA damage with Tripartite Motif-containing 33 (TRIM33), a multifunctional protein implicated in transcriptional regulation, TGF-β signaling, and tumorigenesis. We demonstrate that TRIM33 is dynamically recruited to DNA damage sites in a PARP1- and ALC1-dependent manner. TRIM33-deficient cells show enhanced sensitivity to DNA damage and prolonged retention of ALC1 at sites of DNA breaks. Conversely, overexpression of TRIM33 alleviates the DNA repair defects conferred by ALC1 overexpression. Thus, TRIM33 plays a role in PARP-dependent DNA damage response and regulates ALC1 activity by promoting its timely removal from sites of DNA damage.
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Affiliation(s)
- Atul Kulkarni
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Jay Oza
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Ming Yao
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Honeah Sohail
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Vasudeva Ginjala
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Antonia Tomas-Loba
- the DNA Damage Response Laboratory, London Research Institute, Clare Hall, South Mimms, EN6 3LD Herts, United Kingdom
| | - Zuzana Horejsi
- the DNA Damage Response Laboratory, London Research Institute, Clare Hall, South Mimms, EN6 3LD Herts, United Kingdom
| | - Antoinette R Tan
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903
| | - Simon J Boulton
- the DNA Damage Response Laboratory, London Research Institute, Clare Hall, South Mimms, EN6 3LD Herts, United Kingdom
| | - Shridar Ganesan
- From the Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903.
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257
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258
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Wickramasekera NT, Das GM. Tumor suppressor p53 and estrogen receptors in nuclear-mitochondrial communication. Mitochondrion 2013; 16:26-37. [PMID: 24177747 DOI: 10.1016/j.mito.2013.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 10/04/2013] [Accepted: 10/22/2013] [Indexed: 01/09/2023]
Abstract
Several gene transcription regulators considered solely localized within the nuclear compartment are being reported to be present in the mitochondria as well. There is growing interest in the role of mitochondria in regulating cellular metabolism in normal and disease states. Various findings demonstrate the importance of crosstalk between nuclear and mitochondrial genomes, transcriptomes, and proteomes in regulating cellular functions. Both tumor suppressor p53 and estrogen receptor (ER) were originally characterized as nuclear transcription factors. In addition to their individual roles as regulators of various genes, these two proteins interact resulting in major cellular consequences. In addition to its nuclear role, p53 has been localized to the mitochondria where it executes various transcription-independent functions. Likewise, ERs are reported to be present in mitochondria; however their functional roles remain to be clearly defined. In this review, we provide an integrated view of the current knowledge of nuclear and mitochondrial p53 and ERs and how it relates to normal and pathological physiology.
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Affiliation(s)
- Nadi T Wickramasekera
- Department of Pharmacology and Therapeutics, Center for Genetics and Pharmacology, Roswell Park Cancer Institute, Elm & Carlton Streets, Buffalo, NY 14263, United States
| | - Gokul M Das
- Department of Pharmacology and Therapeutics, Center for Genetics and Pharmacology, Roswell Park Cancer Institute, Elm & Carlton Streets, Buffalo, NY 14263, United States.
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259
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Imamura T, Oshima Y, Hikita A. Regulation of TGF-β family signalling by ubiquitination and deubiquitination. J Biochem 2013; 154:481-9. [PMID: 24165200 DOI: 10.1093/jb/mvt097] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Members of the transforming growth factor-β (TGF-β) family, including TGF-βs, activin and bone morphogenetic proteins (BMPs), are multifunctional proteins that regulate a wide variety of cellular responses, such as proliferation, differentiation, migration and apoptosis. TGF-β family signalling is mainly mediated by membranous serine/threonine kinase receptors and intracellular Smad proteins. This signalling is tightly regulated by various post-translational modifications including ubiquitination. Several E3 ubiquitin ligases play a crucial role in the recognition and ubiquitin-dependent degradation of TGF-β family receptors, Smad proteins and their interacted proteins to regulate positively and negatively TGF-β family signalling. In contrast, non-degradative ubiquitin modifications also regulate TGF-β family signalling. Recently, in addition to protein ubiquitination, deubiquitination by deubiquitinating enzymes has been reported to control TGF-β family signalling pathways. Interestingly, more recent studies suggest that TGF-β signalling is not only regulated via ubiquitination and/or deubiquitination, but also it relies on ubiquitination for its effect on other pathways. Thus, ubiquitin modifications play key roles in TGF-β family signal transduction and cross-talk between TGF-β family signalling and other signalling pathways. Here, we review the current understandings of the positive and negative regulatory mechanisms by ubiquitin modifications that control TGF-β family signalling.
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Affiliation(s)
- Takeshi Imamura
- Department of Molecular Medicine for Pathogenesis, Ehime University Graduate School of Medicine; Division of Bio-imaging, Proteo-Science Center, Ehime University; Translational Research Center, Ehime University Hospital; and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Shitsukawa, Toon, Ehime 791-0295, Japan
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260
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Salazar VS, Zarkadis N, Huang L, Watkins M, Kading J, Bonar S, Norris J, Mbalaviele G, Civitelli R. Postnatal ablation of osteoblast Smad4 enhances proliferative responses to canonical Wnt signaling through interactions with β-catenin. J Cell Sci 2013; 126:5598-609. [PMID: 24101723 DOI: 10.1242/jcs.132233] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Canonical Wnt (cWnt) signaling through β-catenin regulates osteoblast proliferation and differentiation to enhance bone formation. We previously reported that osteogenic action of β-catenin is dependent on BMP signaling. Here, we further examined interactions between cWnt and BMP in bone. In osteoprogenitors stimulated with BMP2, β-catenin localizes to the nucleus, physically interacts with Smad4, and is recruited to DNA-binding transcription complexes containing Smad4, R-Smad1/5 and TCF4. Furthermore, Tcf/Lef-dependent transcription, Ccnd1 expression and proliferation all increase when Smad4, 1 or 5 levels are low, whereas TCF/Lef activities decrease when Smad4 expression is high. The ability of Smad4 to antagonize transcription of Ccnd1 is dependent on DNA-binding activity but Smad4-dependent transcription is not required. In mice, conditional deletion of Smad4 in osterix(+) cells increases mitosis of cells on trabecular bone surfaces as well as in primary osteoblast cultures from adult bone marrow and neonatal calvaria. By contrast, ablation of Smad4 delays differentiation and matrix mineralization by primary osteoblasts in response to Wnt3a, indicating that loss of Smad4 perturbs the balance between proliferation and differentiation in osteoprogenitors. We propose that Smad4 and Tcf/Lef transcription complexes compete for β-catenin, thus restraining cWnt-dependent proliferative signals while favoring the matrix synthesizing activity of osteoblasts.
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Affiliation(s)
- Valerie S Salazar
- Department of Internal Medicine, Division of Bone and Mineral Disease, Washington University School of Medicine, 660 South Euclid, Campus Box 8301, Saint Louis, MO 63110, USA
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261
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Wu Y, Wang Y, Yang XH, Kang T, Zhao Y, Wang C, Evers BM, Zhou BP. The deubiquitinase USP28 stabilizes LSD1 and confers stem-cell-like traits to breast cancer cells. Cell Rep 2013; 5:224-36. [PMID: 24075993 DOI: 10.1016/j.celrep.2013.08.030] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 06/28/2013] [Accepted: 08/15/2013] [Indexed: 10/26/2022] Open
Abstract
LSD1 is a critical chromatin modulator that controls cellular pluripotency and differentiation through the demethylation of H3K4me1/2. Overexpression of LSD1 has been observed in many types of tumors and is correlated with its oncogenic effects in tumorigenesis. However, the mechanism leading to LSD1 upregulation in tumors remains unclear. Using an unbiased siRNA screening against all the human deubiquitinases, we identified USP28 as a bona fide deubiquitinase of LSD1. USP28 interacted with and stabilized LSD1 via deubiquitination. USP28 overexpression correlated with LSD1 upregulation in multiple cancer cell lines and breast tumor samples. Knockdown of USP28 resulted in LSD1 destabilization, leading to the suppression of cancer stem cell (CSC)-like characteristics in vitro and inhibition of tumorigenicity in vivo, which can be rescued by ectopic LSD1 expression. Our study reveals a critical mechanism underlying the epigenetic regulation by USP28 and provides another treatment approach against breast cancer.
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Affiliation(s)
- Yadi Wu
- Department of Molecular and Biomedical Pharmacology, University of Kentucky, College of Medicine, Lexington, KY 40506, USA; Markey Cancer Center, University of Kentucky, College of Medicine, Lexington, KY 40506, USA.
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262
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A mechanical checkpoint controls multicellular growth through YAP/TAZ regulation by actin-processing factors. Cell 2013; 154:1047-1059. [PMID: 23954413 DOI: 10.1016/j.cell.2013.07.042] [Citation(s) in RCA: 1132] [Impact Index Per Article: 102.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 07/16/2013] [Accepted: 07/26/2013] [Indexed: 01/13/2023]
Abstract
Key cellular decisions, such as proliferation or growth arrest, typically occur at spatially defined locations within tissues. Loss of this spatial control is a hallmark of many diseases, including cancer. Yet, how these patterns are established is incompletely understood. Here, we report that physical and architectural features of a multicellular sheet inform cells about their proliferative capacity through mechanical regulation of YAP and TAZ, known mediators of Hippo signaling and organ growth. YAP/TAZ activity is confined to cells exposed to mechanical stresses, such as stretching, location at edges/curvatures contouring an epithelial sheet, or stiffness of the surrounding extracellular matrix. We identify the F-actin-capping/severing proteins Cofilin, CapZ, and Gelsolin as essential gatekeepers that limit YAP/TAZ activity in cells experiencing low mechanical stresses, including contact inhibition of proliferation. We propose that mechanical forces are overarching regulators of YAP/TAZ in multicellular contexts, setting responsiveness to Hippo, WNT, and GPCR signaling.
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263
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Boatman S, Barrett F, Satishchandran S, Jing L, Shestopalov I, Zon LI. Assaying hematopoiesis using zebrafish. Blood Cells Mol Dis 2013; 51:271-6. [PMID: 23916372 DOI: 10.1016/j.bcmd.2013.07.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 07/02/2013] [Indexed: 11/26/2022]
Abstract
The zebrafish has become a commonly used model for studying hematopoiesis as a result of its unique attributes. Zebrafish are highly suitable for large-scale genetic and chemical screens compared to other vertebrate systems. It is now possible to analyze hematopoietic lineages in zebrafish and validate cell function via transplantation assays. Here, we review advancements over the past decade in forward genetic screens, chemical screens, fluorescence-activated cell sorting analysis, and transplantation assays. Integrating these approaches enables new chemical and genetic screens that assay cell function within the hematopoietic system. Studies in zebrafish will continue to contribute and expand our knowledge about hematopoiesis, and develop novel treatments for clinical applications.
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Affiliation(s)
- Sonja Boatman
- Stem Cell Program and Division of Hematology/Oncology, Children's Hospital Boston, Harvard Medical School, Boston, MA, USA
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264
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Ettahar A, Ferrigno O, Zhang MZ, Ohnishi M, Ferrand N, Prunier C, Levy L, Bourgeade MF, Bieche I, Romero DG, Colland F, Atfi A. Identification of PHRF1 as a tumor suppressor that promotes the TGF-β cytostatic program through selective release of TGIF-driven PML inactivation. Cell Rep 2013; 4:530-41. [PMID: 23911286 DOI: 10.1016/j.celrep.2013.07.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 04/17/2013] [Accepted: 07/08/2013] [Indexed: 11/16/2022] Open
Abstract
The homeodomain protein TGIF (TG-interacting factor) restricts TGF-β/Smad cytostatic signaling by interfering with the nucleocytoplasmic transit of the tumor suppressor cPML. Here, we identify PHRF1 as a ubiquitin ligase that enforces TGIF decay by driving its ubiquitination at lysine 130. In so doing, PHRF1 ensures redistribution of cPML into the cytoplasm, where it associates with SARA and coordinates activation of Smad2 by the TGF-β receptor. The PHRF1 gene resides within the tumor suppressor locus 11p15.5, which displays frequent loss in a wide variety of malignancies, including breast cancer. Remarkably, we found that the PHRF1 gene is deleted or silenced in a high proportion of human breast cancer samples and cancer cell lines. Reconstitution of PHRF1 into deficient cells impeded their propensity to form tumors in vivo, most likely because of the reemergence of TGF-β responsiveness. These findings unveil a paradigm behind inactivation of the cPML tumor suppressor network in human malignancies.
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Affiliation(s)
- Asma Ettahar
- Laboratory of Cell Signaling and Carcinogenesis, INSERM UMRS938, 184 Rue du Faubourg St-Antoine, 75571 Paris, France
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265
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Loss of Usp9x disrupts cortical architecture, hippocampal development and TGFβ-mediated axonogenesis. PLoS One 2013; 8:e68287. [PMID: 23861879 PMCID: PMC3702552 DOI: 10.1371/journal.pone.0068287] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Accepted: 05/28/2013] [Indexed: 01/17/2023] Open
Abstract
The deubiquitylating enzyme Usp9x is highly expressed in the developing mouse brain, and increased Usp9x expression enhances the self-renewal of neural progenitors in vitro. USP9X is a candidate gene for human neurodevelopmental disorders, including lissencephaly, epilepsy and X-linked intellectual disability. To determine if Usp9x is critical to mammalian brain development we conditionally deleted the gene from neural progenitors, and their subsequent progeny. Mating Usp9xloxP/loxP mice with mice expressing Cre recombinase from the Nestin promoter deleted Usp9x throughout the entire brain, and resulted in early postnatal lethality. Although the overall brain architecture was intact, loss of Usp9x disrupted the cellular organization of the ventricular and sub-ventricular zones, and cortical plate. Usp9x absence also led to dramatic reductions in axonal length, in vivo and in vitro, which could in part be explained by a failure in Tgf-β signaling. Deletion of Usp9x from the dorsal telencephalon only, by mating with Emx1-cre mice, was compatible with survival to adulthood but resulted in reduction or loss of the corpus callosum, a dramatic decrease in hippocampal size, and disorganization of the hippocampal CA3 region. This latter phenotypic aspect resembled that observed in Doublecortin knock-out mice, which is an Usp9x interacting protein. This study establishes that Usp9x is critical for several aspects of CNS development, and suggests that its regulation of Tgf-β signaling extends to neurons.
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Al-Salihi MA, Herhaus L, Sapkota GP. Regulation of the transforming growth factor β pathway by reversible ubiquitylation. Open Biol 2013; 2:120082. [PMID: 22724073 PMCID: PMC3376735 DOI: 10.1098/rsob.120082] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 04/25/2012] [Indexed: 12/20/2022] Open
Abstract
The transforming growth factor β (TGFβ) signalling pathway plays a central role during embryonic development and in adult tissue homeostasis. It regulates gene transcription through a signalling cascade from cell surface receptors to intracellular SMAD transcription factors and their nuclear cofactors. The extent, duration and potency of signalling in response to TGFβ cytokines are intricately regulated by complex biochemical processes. The corruption of these regulatory processes results in aberrant TGFβ signalling and leads to numerous human diseases, including cancer. Reversible ubiquitylation of pathway components is a key regulatory process that plays a critical role in ensuring a balanced response to TGFβ signals. Many studies have investigated the mechanisms by which various E3 ubiquitin ligases regulate the turnover and activity of TGFβ pathway components by ubiquitylation. Moreover, recent studies have shed new light into their regulation by deubiquitylating enzymes. In this report, we provide an overview of current understanding of the regulation of TGFβ signalling by E3 ubiquitin ligases and deubiquitylases.
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Affiliation(s)
- Mazin A Al-Salihi
- Medical Research Council-Protein Phosphorylation Unit, Sir James Black Centre, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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267
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Al-Salihi MA, Herhaus L, Macartney T, Sapkota GP. USP11 augments TGFβ signalling by deubiquitylating ALK5. Open Biol 2013; 2:120063. [PMID: 22773947 PMCID: PMC3390794 DOI: 10.1098/rsob.120063] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/31/2012] [Indexed: 12/20/2022] Open
Abstract
The TGFβ receptors signal through phosphorylation and nuclear translocation of SMAD2/3. SMAD7, a transcriptional target of TGFβ signals, negatively regulates the TGFβ pathway by recruiting E3 ubiquitin ligases and targeting TGFβ receptors for ubiquitin-mediated degradation. In this report, we identify a deubiquitylating enzyme USP11 as an interactor of SMAD7. USP11 enhances TGFβ signalling and can override the negative effects of SMAD7. USP11 interacts with and deubiquitylates the type I TGFβ receptor (ALK5), resulting in enhanced TGFβ-induced gene transcription. The deubiquitylase activity of USP11 is required to enhance TGFβ-induced gene transcription. RNAi-mediated depletion of USP11 results in inhibition of TGFβ-induced SMAD2/3 phosphorylation and TGFβ-mediated transcriptional responses. Central to TGFβ pathway signalling in early embryogenesis and carcinogenesis is TGFβ-induced epithelial to mesenchymal transition. USP11 depletion results in inhibition of TGFβ-induced epithelial to mesenchymal transition.
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Affiliation(s)
- Mazin A Al-Salihi
- Medical Research Council - Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dow St., Dundee DD1 5EH, UK
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268
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Bondy C, Bakalov VK, Cheng C, Olivieri L, Rosing DR, Arai AE. Bicuspid aortic valve and aortic coarctation are linked to deletion of the X chromosome short arm in Turner syndrome. J Med Genet 2013; 50:662-5. [PMID: 23825392 PMCID: PMC3786649 DOI: 10.1136/jmedgenet-2013-101720] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background Congenital heart disease (CHD) is a cardinal feature of X chromosome monosomy, or Turner syndrome (TS). Haploinsufficiency for gene(s) located on Xp have been implicated in the short stature characteristic of the syndrome, but the chromosomal region related to the CHD phenotype has not been established. Design We used cardiac MRI to diagnose cardiovascular abnormalities in four non-mosaic karyotype groups based on 50-metaphase analyses: 45,X (n=152); 46,X,del(Xp) (n=15); 46,X,del(Xq) (n=4); and 46,X,i(Xq) (n=14) from peripheral blood cells. Results Bicuspid aortic valves (BAV) were found in 52/152 (34%) 45,X study subjects and aortic coarctation (COA) in 19/152 (12.5%). Isolated anomalous pulmonary veins (APV) were detected in 15/152 (10%) for the 45,X study group, and this defect was not correlated with the presence of BAV or COA. BAVs were present in 28.6% of subjects with Xp deletions and COA in 6.7%. APV were not found in subjects with Xp deletions. The most distal break associated with the BAV/COA trait was at cytologic band Xp11.4 and ChrX:41,500 000. One of 14 subjects (7%) with the 46,X,i(Xq) karyotype had a BAV and no cases of COA or APV were found in this group. No cardiovascular defects were found among four patients with Xq deletions. Conclusions The high prevalence of BAV and COA in subjects missing only the X chromosome short arm indicates that haploinsufficiency for Xp genes contributes to abnormal aortic valve and aortic arch development in TS.
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Affiliation(s)
- Carolyn Bondy
- Section on Epigenetics and Development, National Institute of Child Health and Human Development, Bethesda, Maryland, USA
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269
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Shimmi O, Newfeld SJ. New insights into extracellular and post-translational regulation of TGF-β family signalling pathways. J Biochem 2013; 154:11-9. [PMID: 23698094 PMCID: PMC3693483 DOI: 10.1093/jb/mvt046] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Accepted: 05/08/2013] [Indexed: 01/19/2023] Open
Abstract
Members of the transforming growth factor-β (TGF-β) family of secreted proteins are present in all multicellular animals. TGF-β proteins are versatile intercellular signalling molecules that orchestrate cell fate decisions during development and maintain homeostasis in adults. The Smad family of signal transducers implements TGF-β signals in responsive cells. Given the ability of TGF-β ligands to induce dramatic responses in target cells, numerous regulatory mechanisms exist to prevent unintended consequences. Here we review new reports of extracellular and post-translational regulation in Drosophila and vertebrates. Extracellular topics include the regulation of TGF-β signalling range and the coordination between tissue morphogenesis and TGF-β signalling. Post-translational topics include the regulation of TGF-β signal transduction by Gsk3-β phosphorylation of Smads and by cycles of Smad mono- and deubiquitylation. Extension of the ubiquitylation data to the Hippo pathway is also discussed.
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Affiliation(s)
- Osamu Shimmi
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland and School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | - Stuart J. Newfeld
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland and School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
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270
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Fattet L, Ay AS, Bonneau B, Jallades L, Mikaelian I, Treilleux I, Gillet G, Hesling C, Rimokh R. TIF1γ requires sumoylation to exert its repressive activity on TGFβ signaling. J Cell Sci 2013; 126:3713-23. [PMID: 23788427 DOI: 10.1242/jcs.126748] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
TIF1γ, a new regulator of TGFβ signaling, inhibits the Smad4-mediated TGFβ response by interaction with Smad2/3 or ubiquitylation of Smad4. We have shown that TIF1γ participates in TGFβ signaling as a negative regulator of Smad4 during the TGFβ-induced epithelial-to-mesenchymal transition (EMT) in mammary epithelial cells, and during terminal differentiation of mammary alveolar epithelial cells and lactation. We demonstrate here that TIF1γ is sumoylated and interacts with Ubc9, the only known SUMO-conjugating enzyme. Four functional sumoylation sites lie within the middle domain of TIF1γ, the Smad interaction domain. We show that a sumoylation-defective TIF1γ mutant significantly reduces TIF1γ inhibition of Smad complexes and that of the Smad-mediated TGFβ transcriptional response. Moreover, chromatin immunoprecipitation experiments indicate that TIF1γ sumoylation is required to limit Smad4 binding on the PAI-1 TGFβ target gene promoter. Ectopic expression of TIF1γ in mammary epithelial cells inhibits TGFβ-induced EMT, an effect relieved by expression of non-sumoylated TIF1γ. Taken together, our results identify a new TGFβ regulatory layer, whereby sumoylation strengthens the TIF1γ repressive action on canonical TGFβ signaling.
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Affiliation(s)
- Laurent Fattet
- Inserm U1052, Centre de Recherche en Cancérologie de Lyon, 69373 Lyon, Cedex 08, France
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271
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Falk S, Joosten E, Kaartinen V, Sommer L. Smad4 and Trim33/Tif1γ redundantly regulate neural stem cells in the developing cortex. ACTA ACUST UNITED AC 2013; 24:2951-63. [PMID: 23765158 DOI: 10.1093/cercor/bht149] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
During central nervous system (CNS) development, proliferation and differentiation of neural stem cells (NSCs) have to be regulated in a spatio-temporal fashion. Here, we report different branches of the transforming growth factor β (TGFβ) signaling pathway to be required for the brain area-specific control of NSCs. In the midbrain, canonical TGFβ signaling via Smad4 regulates the balance between proliferation and differentiation of NSCs. Accordingly, Smad4 deletion resulted in horizontal expansion of NSCs due to increased proliferation, decreased differentiation, and decreased cell cycle exit. In the developing cortex, however, ablation of Smad4 alone did not have any effect on proliferation and differentiation of NSCs. In contrast, concomitant mutation of both Smad4 and Trim33 led to an increase in proliferative cells in the ventricular zone due to decreased cell cycle exit, revealing a functional redundancy of Smad4 and Trim33. Furthermore, in Smad4-Trim33 double mutant embryos, cortical NSCs generated an excess of deep layer neurons concurrent with a delayed and reduced production of upper layer neurons and, in addition, failed to undergo the neurogenic to gliogenic switch at the right developmental stage. Thus, our data disclose that in different regions of the developing CNS different aspects of the TGFβ signaling pathway are required to ensure proper development.
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Affiliation(s)
- Sven Falk
- Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland, Current address: Helmholtz Center Munich, German Research Center for Environmental Health, Institute for Stem Cell Research, D-85764 Neuherberg, Germany
| | - Esméé Joosten
- Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Vesa Kaartinen
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA and
| | - Lukas Sommer
- Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland
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272
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Regulation of T cell function by the ubiquitin-specific protease USP9X via modulating the Carma1-Bcl10-Malt1 complex. Proc Natl Acad Sci U S A 2013; 110:9433-8. [PMID: 23690623 DOI: 10.1073/pnas.1221925110] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The ubiquitin conjugation system plays an important role in immune regulation; however, the ubiquitin-specific proteases (USPs) that carry out deubiquitination of cellular substrates are poorly understood. Here we show that in vivo knockdown of the deubiquitinating enzyme USP9X attenuates T-cell proliferation. In addition, naïve CD4(+) T cells from USP9X knockdown chimeric mice display decreased cytokine production and T helper cell differentiation in vitro, which we confirmed in vivo by performing adoptive transfer of transgenic T cells and subsequent immunization. USP9X silencing in both a human T-cell line and mouse primary T cells reduced T-cell receptor (TCR) signaling-induced NF-κB activation. Mechanistically, USP9X interacts with Bcl10 of the Carma1-Bcl10-Malt1 (CBM) complex and removes the TCR-induced ubiquitin chain from Bcl10, which facilitates the association of Carma1 with Bcl0-Malt1. These results demonstrate that USP9X is a crucial positive regulator of the TCR signaling pathway and is required for T-cell function through the modulation of CBM complex formation.
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273
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The SOX2-interactome in brain cancer cells identifies the requirement of MSI2 and USP9X for the growth of brain tumor cells. PLoS One 2013; 8:e62857. [PMID: 23667531 PMCID: PMC3647065 DOI: 10.1371/journal.pone.0062857] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 03/26/2013] [Indexed: 12/16/2022] Open
Abstract
Medulloblastomas and glioblastomas, the most common primary brain tumors in children and adults, respectively, are extremely difficult to treat. Efforts to identify novel proteins essential for the growth of these tumors may help to further our understanding of the biology of these tumors, as well as, identify targets for future therapies. The recent identification of multiple transcription factor-centric protein interaction landscapes in embryonic stem cells has identified numerous understudied proteins that are essential for the self-renewal of these stem cells. To identify novel proteins essential for the fate of brain tumor cells, we examined the protein interaction network of the transcription factor, SOX2, in medulloblastoma cells. For this purpose, Multidimensional Protein Identification Technology (MudPIT) identified >280 SOX2-associated proteins in the medulloblastoma cell line DAOY. To begin to understand the roles of SOX2-associated proteins in brain cancer, we focused on two SOX2-associated proteins, Musashi 2 (MSI2) and Ubiquitin Specific Protease 9x (USP9X). Recent studies have implicated MSI2, a putative RNA binding protein, and USP9X, a deubiquitinating enzyme, in several cancers, but not brain tumors. We demonstrate that knockdown of MSI2 significantly reduces the growth of DAOY cells as well as U87 and U118 glioblastoma cells. We also demonstrate that the knockdown of USP9X in DAOY, U87 and U118 brain tumor cells strongly reduces their growth. Together, our studies identify a large set of SOX2-associated proteins in DAOY medulloblastoma cells and identify two proteins, MSI2 and USP9X, that warrant further investigation to determine whether they are potential therapeutic targets for brain cancer.
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274
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Williamson A, Werner A, Rape M. The Colossus of ubiquitylation: decrypting a cellular code. Mol Cell 2013; 49:591-600. [PMID: 23438855 DOI: 10.1016/j.molcel.2013.01.028] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/19/2013] [Accepted: 01/24/2013] [Indexed: 11/20/2022]
Abstract
Ubiquitylation is an essential posttranslational modification that can regulate the stability, activity, and localization of thousands of proteins. The reversible attachment of ubiquitin as well as interpretation of the ubiquitin signal depends on dynamic protein networks that are challenging to analyze. In this perspective, we discuss tools of the trade that have recently been developed to dissect mechanisms of ubiquitin-dependent signaling, thereby revealing the critical features of an important cellular code.
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Affiliation(s)
- Adam Williamson
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA
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275
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Tansley SL, McHugh NJ, Wedderburn LR. Adult and juvenile dermatomyositis: are the distinct clinical features explained by our current understanding of serological subgroups and pathogenic mechanisms? Arthritis Res Ther 2013; 15:211. [PMID: 23566358 PMCID: PMC3672700 DOI: 10.1186/ar4198] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adult and juvenile dermatomyositis share the hallmark features of pathognomic skin rash and muscle inflammation, but are heterogeneous disorders with a range of additional disease features and complications. The frequency of important clinical features such as calcinosis, interstitial lung disease and malignancy varies markedly between adult and juvenile disease. These differences may reflect different disease triggers between children and adults, but whilst various viral and other environmental triggers have been implicated, results are so far conflicting. Myositis-specific autoantibodies can be detected in both adults and children with idiopathic inflammatory myopathies. They are associated with specific disease phenotypes and complications, and divide patients into clinically homogenous subgroups. Interestingly, whilst the same autoantibodies are found in both adults and children, the disease features remain different within autoantibody subgroups, particularly with regard to life-threatening disease associations, such as malignancy and rapidly progressive interstitial lung disease. Our understanding of the mechanisms that underlie these differences is limited by a lack of studies directly comparing adults and children. Dermatomyositis is an autoimmune disease, which is believed to develop as a result of an environmental trigger in a genetically predisposed individual. Age-specific host immune responses and muscle physiology may be additional complicating factors that have significant impact on disease presentation. Further study into this area may produce new insights into disease pathogenesis.
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276
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Abstract
Ubiquitylation is a reversible post-translational modification that has emerged as a key regulator of most complex cellular processes. It may rival phosphorylation in scope and exceed it in complexity. The dynamic nature of ubiquitylation events is important for governing protein stability, maintaining ubiquitin homeostasis and controlling ubiquitin-dependent signalling pathways. The human genome encodes ~80 active deubiquitylating enzymes (DUBs, also referred to as deubiquitinases), which exhibit distinct specificity profiles towards the various ubiquitin chain topologies. As a result of their ability to reverse ubiquitylation, these enzymes control a broad range of key cellular processes. In this Commentary we discuss the cellular functions of DUBs, such as their role in governing membrane traffic and protein quality control. We highlight two key signalling pathways--the Wnt and transforming growth factor β (TGF-β) pathways, for which dynamic ubiquitylation has emerged as a key regulator. We also discuss the roles of DUBs in the nucleus, where they govern transcriptional activity and DNA repair pathways.
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Affiliation(s)
- Michael J Clague
- Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, L69 3BX Liverpool, UK.
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277
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Platta HW, Hagen S, Erdmann R. The exportomer: the peroxisomal receptor export machinery. Cell Mol Life Sci 2013; 70:1393-411. [PMID: 22983384 PMCID: PMC11113987 DOI: 10.1007/s00018-012-1136-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Revised: 07/30/2012] [Accepted: 08/13/2012] [Indexed: 12/21/2022]
Abstract
Peroxisomes constitute a dynamic compartment of almost all eukaryotic cells. Depending on environmental changes and cellular demands peroxisomes can acquire diverse metabolic roles. The compartmentalization of peroxisomal matrix enzymes is a prerequisite to carry out their physiologic function. The matrix proteins are synthesized on free ribosomes in the cytosol and are ferried to the peroxisomal membrane by specific soluble receptors. Subsequent to cargo release into the peroxisomal matrix, the receptors are exported back to the cytosol to facilitate further rounds of matrix protein import. This dislocation step is accomplished by a remarkable machinery, which comprises enzymes required for the ubiquitination as well as the ATP-dependent extraction of the receptor from the membrane. Interestingly, receptor ubiquitination and dislocation are the only known energy-dependent steps in the peroxisomal matrix protein import process. The current view is that the export machinery of the receptors might function as molecular motor not only in the dislocation of the receptors but also in the import step of peroxisomal matrix protein by coupling ATP-dependent removal of the peroxisomal import receptor with cargo translocation into the organelle. In this review we will focus on the architecture and function of the peroxisomal receptor export machinery, the peroxisomal exportomer.
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Affiliation(s)
- Harald W. Platta
- Abteilung für Systembiochemie, Medizinische Fakultät der Ruhr-Universität Bochum, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum, Germany
| | - Stefanie Hagen
- Abteilung für Systembiochemie, Medizinische Fakultät der Ruhr-Universität Bochum, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum, Germany
| | - Ralf Erdmann
- Abteilung für Systembiochemie, Medizinische Fakultät der Ruhr-Universität Bochum, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum, Germany
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278
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Abstract
Protein quality control functions to minimize the level and toxicity of misfolded proteins in the cell. Protein quality control is performed by intricate collaboration among chaperones and target protein degradation. The latter is performed primarily by the ubiquitin-proteasome system and perhaps autophagy. Terminally misfolded proteins that are not timely removed tend to form aggregates. Their clearance requires macroautophagy. Macroautophagy serves in intracellular quality control also by selectively segregating defective organelles (eg, mitochondria) and targeting them for degradation by the lysosome. Inadequate protein quality control is observed in a large subset of failing human hearts with a variety of causes, and its pathogenic role has been experimentally demonstrated. Multiple posttranslational modifications can occur to substrate proteins and protein quality control machineries, promoting or hindering the removal of the misfolded proteins. This article highlights recent advances in posttranslational modification-mediated regulation of intracellular quality control mechanisms and its known involvement in cardiac pathology.
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Affiliation(s)
- Xuejun Wang
- Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, 414 East Clark St, Vermillion, SD 57069, USA.
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279
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Fine-tuning BMP7 signalling in adipogenesis by UBE2O/E2-230K-mediated monoubiquitination of SMAD6. EMBO J 2013; 32:996-1007. [PMID: 23455153 DOI: 10.1038/emboj.2013.38] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 02/01/2013] [Indexed: 12/28/2022] Open
Abstract
SMAD6 is a crucial feedback inhibitory regulator of bone morphogenetic protein (BMP)/SMAD signalling. Although little is known regarding the post-transcriptional modification of inhibitory SMADs and the mechanism by which their function is regulated. In this study, using a whole proteomic interaction screen for SMAD6, we identified a large putative E2 ubiquitin-conjugating enzyme UBE2O (E2-230K) as a novel interacting protein of SMAD6. We showed that UBE2O functions as an E2-E3 hybrid to monoubiquitinate SMAD6 at lysine 174 and that the cysteine 885 residue of human UBE2O is necessary for SMAD6 monoubiquitination. Inactivation of the SMAD6 monoubiquitination site specially potentiates the inhibitory ability of SMAD6 against BMP7-induced SMAD1 phosphorylation and transcriptional responses. We also found that UBE2O potentiated BMP7 signalling in a SMAD6-dependent manner. Addressing the molecular mechanism by which UBE2O and monoubiquitinated SMAD6 potentiate BMP7 signalling, we demonstrated that monoubiquitinated SMAD6 impairs the binding affinity of non-modified SMAD6 to the BMP type I receptor. Moreover, UBE2O and SMAD6 cooperated in the regulation of BMP7-induced adipogenesis.
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280
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Abstract
PURPOSE OF REVIEW To review recent advances in our understanding of autoantibodies associated with dermatomyositis and the autoimmune necrotizing myopathies. RECENT FINDINGS Autoantibodies preferentially associated with dermatomyositis include those recognizing Mi-2, MDA5, TIF1γ, and NXP-2. Each of these is associated with a distinct clinical phenotype. Autoantibodies found in patients with autoimmune necrotizing myopathies recognize signal recognition particle and 3-hydroxy-3-methylglutaryl-coenzime A reductase (HMG-CoA) reductase. The latter are found in patients with statin-associated autoimmune muscle disease. SUMMARY As these are helpful both diagnostically and prognostically, a rheumatologist should be familiar with autoantibodies found in patients with dermatomyositis and the autoimmune necrotizing myopathies.
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281
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Betulinic acid selectively increases protein degradation and enhances prostate cancer-specific apoptosis: possible role for inhibition of deubiquitinase activity. PLoS One 2013; 8:e56234. [PMID: 23424652 PMCID: PMC3570422 DOI: 10.1371/journal.pone.0056234] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 01/11/2013] [Indexed: 02/03/2023] Open
Abstract
Inhibition of the ubiquitin-proteasome system (UPS) of protein degradation is a valid anti-cancer strategy and has led to the approval of bortezomib for the treatment of multiple myeloma. However, the alternative approach of enhancing the degradation of oncoproteins that are frequently overexpressed in cancers is less developed. Betulinic acid (BA) is a plant-derived small molecule that can increase apoptosis specifically in cancer but not in normal cells, making it an attractive anti-cancer agent. Our results in prostate cancer suggested that BA inhibited multiple deubiquitinases (DUBs), which resulted in the accumulation of poly-ubiquitinated proteins, decreased levels of oncoproteins, and increased apoptotic cell death. In normal fibroblasts, however, BA did not inhibit DUB activity nor increased total poly-ubiquitinated proteins, which was associated with a lack of effect on cell death. In the TRAMP transgenic mouse model of prostate cancer, treatment with BA (10 mg/kg) inhibited primary tumors, increased apoptosis, decreased angiogenesis and proliferation, and lowered androgen receptor and cyclin D1 protein. BA treatment also inhibited DUB activity and increased ubiquitinated proteins in TRAMP prostate cancer but had no effect on apoptosis or ubiquitination in normal mouse tissues. Overall, our data suggests that BA-mediated inhibition of DUBs and induction of apoptotic cell death specifically in prostate cancer but not in normal cells and tissues may provide an effective non-toxic and clinically selective agent for chemotherapy.
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282
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Beyer TA, Narimatsu M, Weiss A, David L, Wrana JL. The TGFβ superfamily in stem cell biology and early mammalian embryonic development. Biochim Biophys Acta Gen Subj 2013; 1830:2268-79. [DOI: 10.1016/j.bbagen.2012.08.025] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 07/23/2012] [Accepted: 08/28/2012] [Indexed: 01/20/2023]
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283
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Wisotzkey RG, Konikoff CE, Newfeld SJ. Hippo pathway phylogenetics predicts monoubiquitylation of Salvador and Merlin/Nf2. PLoS One 2012; 7:e51599. [PMID: 23272121 PMCID: PMC3522738 DOI: 10.1371/journal.pone.0051599] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Accepted: 11/08/2012] [Indexed: 01/20/2023] Open
Abstract
Recently we employed phylogenetics to predict that the cellular interpretation of TGF-β signals is modulated by monoubiquitylation cycles affecting the Smad4 signal transducer/tumor suppressor. This prediction was subsequently validated by experiments in flies, frogs and mammalian cells. Here we apply a phylogenetic approach to the Hippo pathway and predict that two of its signal transducers, Salvador and Merlin/Nf2 (also a tumor suppressor) are regulated by monoubiquitylation. This regulatory mechanism does not lead to protein degradation but instead serves as a highly efficient “off/on” switch when the protein is subsequently deubiquitylated. Overall, our study shows that the creative application of phylogenetics can predict new roles for pathway components and new mechanisms for regulating intercellular signaling pathways.
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Affiliation(s)
| | - Charlotte E. Konikoff
- Department of Biology, University of Washington, Seattle, Washington, United States of America
| | - Stuart J. Newfeld
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- * E-mail:
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284
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Peddaboina C, Jupiter D, Fletcher S, Yap JL, Rai A, Tobin RP, Jiang W, Rascoe P, Rogers MKN, Smythe WR, Cao X. The downregulation of Mcl-1 via USP9X inhibition sensitizes solid tumors to Bcl-xl inhibition. BMC Cancer 2012; 12:541. [PMID: 23171055 PMCID: PMC3543233 DOI: 10.1186/1471-2407-12-541] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 11/12/2012] [Indexed: 12/11/2022] Open
Abstract
Background It has been shown in many solid tumors that the overexpression of the pro-survival Bcl-2 family members Bcl-xL and Mcl-1 confers resistance to a variety of chemotherapeutic agents. Mcl-1 is a critical survival protein in a variety of cell lineages and is critically regulated via ubiquitination. Methods The Mcl-1, Bcl-xL and USP9X expression patterns in human lung and colon adenocarcinomas were evaluated via immunohistochemistry. Interaction between USP9X and Mcl-1 was demonstrated by immunoprecipitation-western blotting. The protein expression profiles of Mcl-1, Bcl-xL and USP9X in multiple cancer cell lines were determined by western blotting. Annexin-V staining and cleaved PARP western blotting were used to assay for apoptosis. The cellular toxicities after various treatments were measured via the XTT assay. Results In our current analysis of colon and lung cancer samples, we demonstrate that Mcl-1 and Bcl-xL are overexpressed and also co-exist in many tumors and that the expression levels of both genes correlate with the clinical staging. The downregulation of Mcl-1 or Bcl-xL via RNAi was found to increase the sensitivity of the tumor cells to chemotherapy. Furthermore, our analyses revealed that USP9X expression correlates with that of Mcl-1 in human cancer tissue samples. We additionally found that the USP9X inhibitor WP1130 promotes Mcl-1 degradation and increases tumor cell sensitivity to chemotherapies. Moreover, the combination of WP1130 and ABT-737, a well-documented Bcl-xL inhibitor, demonstrated a chemotherapeutic synergy and promoted apoptosis in different tumor cells. Conclusion Mcl-1, Bcl-xL and USP9X overexpression are tumor survival mechanisms protective against chemotherapy. USP9X inhibition increases tumor cell sensitivity to various chemotherapeutic agents including Bcl-2/Bcl-xL inhibitors.
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Affiliation(s)
- Chander Peddaboina
- Department of Surgery, Scott & White Memorial Hospital and Clinic, The Texas A&M University System, Health Science Center, College of Medicine, Temple, TX 76504, USA
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285
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Hesling C, Lopez J, Fattet L, Gonzalo P, Treilleux I, Blanchard D, Losson R, Goffin V, Pigat N, Puisieux A, Mikaelian I, Gillet G, Rimokh R. Tif1γ is essential for the terminal differentiation of mammary alveolar epithelial cells and for lactation through SMAD4 inhibition. Development 2012; 140:167-75. [PMID: 23154409 DOI: 10.1242/dev.085068] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Transforming growth factor β (TGFβ) is widely recognised as an important factor that regulates many steps of normal mammary gland (MG) development, including branching morphogenesis, functional differentiation and involution. Tif1γ has previously been reported to temporally and spatially control TGFβ signalling during early vertebrate development by exerting negative effects over SMAD4 availability. To evaluate the contribution of Tif1 γ to MG development, we developed a Cre/LoxP system to specifically invalidate the Tif1g gene in mammary epithelial cells in vivo. Tif1g-null mammary gland development appeared to be normal and no defects were observed during the lifespan of virgin mice. However, a lactation defect was observed in mammary glands of Tif1g-null mice. We demonstrate that Tif1 γ is essential for the terminal differentiation of alveolar epithelial cells at the end of pregnancy and to ensure lactation. Tif1 γ appears to play a crucial role in the crosstalk between TGFβ and prolactin pathways by negatively regulating both PRL receptor expression and STAT5 phosphorylation, thereby impairing the subsequent transactivation of PRL target genes. Using HC11 cells as a model, we demonstrate that the effects of Tif1g knockdown on lactation depend on both SMAD4 and TGFβ. Interestingly, we found that the Tif1γ expression pattern in mammary epithelial cells is almost symmetrically opposite to that described for TGFβ. We propose that Tif1γ contributes to the repression of TGFβ activity during late pregnancy and prevents lactation by inhibiting SMAD4.
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Affiliation(s)
- Cédric Hesling
- Centre de Recherche en Cancérologie de Lyon, Inserm UMR-S1052, CNRS UMR5286, Centre Léon Bérard, Lyon, France
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286
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Cheng X, Alborzinia H, Merz KH, Steinbeisser H, Mrowka R, Scholl C, Kitanovic I, Eisenbrand G, Wölfl S. Indirubin Derivatives Modulate TGFβ/BMP Signaling at Different Levels and Trigger Ubiquitin-Mediated Depletion of Nonactivated R-Smads. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.chembiol.2012.09.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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287
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Han KJ, Foster DG, Zhang NY, Kanisha K, Dzieciatkowska M, Sclafani RA, Hansen KC, Peng J, Liu CW. Ubiquitin-specific protease 9x deubiquitinates and stabilizes the spinal muscular atrophy protein-survival motor neuron. J Biol Chem 2012; 287:43741-52. [PMID: 23112048 DOI: 10.1074/jbc.m112.372318] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Spinal muscular atrophy (SMA), the leading genetic disorder of infant mortality, is caused by low levels of survival motor neuron (SMN) protein. Currently it is not clear how the SMN protein levels are regulated at the post-transcriptional level. In this report, we find that Usp9x, a deubiquitinating enzyme, stably associates with the SMN complex via directly interacting with SMN. Usp9x deubiquitinates SMN that is mostly mono- and di-ubiquitinated. Knockdown of Usp9x promotes SMN degradation and reduces the protein levels of SMN and the SMN complex in cultured mammalian cells. Interestingly, Usp9x does not deubiquitinate nuclear SMNΔ7, the main protein product of the SMN2 gene, which is polyubiquitinated and rapidly degraded by the proteasome. Together, our results indicate that SMN and SMNΔ7 are differently ubiquitinated; Usp9x plays an important role in stabilizing SMN and the SMN complex, likely via antagonizing Ub-dependent SMN degradation.
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Affiliation(s)
- Ke-Jun Han
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
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288
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Weiss A, Attisano L. The TGFbeta superfamily signaling pathway. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:47-63. [PMID: 23799630 DOI: 10.1002/wdev.86] [Citation(s) in RCA: 381] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The transforming growth factor (TGF)beta superfamily of secreted factors is comprised of over 30 members including Activins, Nodals, Bone Morphogenetic Proteins (BMPs), and Growth and Differentiation Factors (GDFs). Members of the family, which are found in both vertebrates and invertebrates, are ubiquitously expressed in diverse tissues and function during the earliest stages of development and throughout the lifetime of animals. Indeed, key roles in embryonic stem cell self-renewal, gastrulation, differentiation, organ morphogenesis, and adult tissue homeostasis have been delineated. Consistent with this ubiquitous activity, aberrant TGFbeta superfamily signaling is associated with a wide range of human pathologies including autoimmune, cardiovascular and fibrotic diseases, as well as cancer. TGFbeta superfamily ligands signal through cell-surface serine/threonine kinase receptors to the intracellular Smad proteins, which in turn accumulate in the nucleus to regulate gene expression. In addition to this universal cascade, Smad-independent pathways are also employed in a cell-specific manner to transduce TGFbeta signals. Ligand access to the signaling receptors is regulated by numerous secreted agonists and antagonists and by membrane-associated coreceptors that act in a context-dependent manner. Given the fundamental role of the TGFbeta superfamily in metazoans and the diversity of biological responses, it is not surprising that the signaling pathway is subject to tight and complex regulation at levels both outside and inside the cell. WIREs Dev Biol 2013, 2:47-63. doi: 10.1002/wdev.86 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Alexander Weiss
- Centre for Systems Biology, Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
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289
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Pathway analysis in blood cells of pigs infected with classical swine fever virus: comparison of pigs that develop a chronic form of infection or recover. Arch Virol 2012; 158:325-39. [DOI: 10.1007/s00705-012-1491-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/17/2012] [Indexed: 01/25/2023]
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290
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Abstract
The basic elements of the transforming growth factor-β (TGFβ) pathway were revealed more than a decade ago. Since then, the concept of how the TGFβ signal travels from the membrane to the nucleus has been enriched with additional findings, and its multifunctional nature and medical relevance have relentlessly come to light. However, an old mystery has endured: how does the context determine the cellular response to TGFβ? Solving this question is key to understanding TGFβ biology and its many malfunctions. Recent progress is pointing at answers.
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Affiliation(s)
- Joan Massagué
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
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291
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Self-regulation of the head-inducing properties of the Spemann organizer. Proc Natl Acad Sci U S A 2012; 109:15354-9. [PMID: 22949641 DOI: 10.1073/pnas.1203000109] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Spemann organizer stands out from other signaling centers of the embryo because of its broad patterning effects. It defines development along the anteroposterior and dorsoventral axes of the vertebrate body, mainly by secreting antagonists of growth factors. Qualitative models proposed more than a decade ago explain the organizer's region-specific inductions (i.e., head and trunk) as the result of different combinations of antagonists. For example, head induction is mediated by extracellular inhibition of Wnt, BMP, and Nodal ligands. However, little is known about how the levels of these antagonists become harmonized with those of their targets and with the factors initially responsible for germ layers and organizer formation, including Nodal itself. Here we show that key ingredients of the head-organizer development, namely Nodal ligands, Nodal antagonists, and ADMP ligands reciprocally adjust each other's strength and range of activity by a self-regulating network of interlocked feedback and feedforward loops. A key element in this cross-talk is the limited availability of ACVR2a, for which Nodal and ADMP must compete. By trapping Nodal extracellularly, the Nodal antagonists Cerberus and Lefty are permissive for ADMP activity. The system self-regulates because ADMP/ACVR2a/Smad1 signaling in turn represses the expression of the Nodal antagonists, reestablishing the equilibrium. In sum, this work reveals an unprecedented set of interactions operating within the organizer that is critical for embryonic patterning.
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292
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Harris DR, Mims A, Bunz F. Genetic disruption of USP9X sensitizes colorectal cancer cells to 5-fluorouracil. Cancer Biol Ther 2012; 13:1319-24. [PMID: 22895071 DOI: 10.4161/cbt.21792] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The X-linked deubiquitinase USP9X affects the stability and activity of numerous regulatory proteins that influence cell survival. Recent studies suggest that decreased USP9X expression can confer a selective advantage onto developing cancer cells and thereby promotes disease progression. To examine the effect of USP9X on the cellular responses to anticancer therapies, we derived cancer cell lines in which the USP9X locus was disrupted by homologous recombination. The resulting USP9X-deficient cancer cells exhibited increased activation of apoptotic pathways and markedly decreased clonogenic survival in response to 5-fluorouracil, a chemotherapeutic drug that is widely used for treatment of gastrointestinal malignancies. These unexpected results suggest that cancers with low USP9X expression might be specifically sensitized to some conventional therapeutic agents.
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Affiliation(s)
- Dennis R Harris
- Department of Radiation Oncology and Molecular Radiation Sciences, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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293
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Zhang Y, Fan KJ, Sun Q, Chen AZ, Shen WL, Zhao ZH, Zheng XF, Yang X. Functional screening for miRNAs targeting Smad4 identified miR-199a as a negative regulator of TGF-β signalling pathway. Nucleic Acids Res 2012; 40:9286-97. [PMID: 22821565 PMCID: PMC3467063 DOI: 10.1093/nar/gks667] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transforming growth factor-β (TGF-β) signalling pathway participates in various biological processes. Dysregulation of Smad4, a central cellular transducer of TGF-β signalling, is implicated in a wide range of human diseases and developmental disorders. However, the mechanisms underlying Smad4 dysregulation are not fully understood. Using a functional screening approach based on luciferase reporter assays, we identified 39 microRNAs (miRNAs) as potential regulators of Smad4 from an expression library of 388 human miRNAs. The screening was supported by bioinformatic analysis, as 24 of 39 identified miRNAs were also predicted to target Smad4. MiR-199a, one of the identified miRNAs, was inversely correlated with Smad4 expression in various human cancer cell lines and gastric cancer tissues, and repressed Smad4 expression and blocked canonical TGF-β transcriptional responses in cell lines. These effects were dependent on the presence of a conserved, but not perfect seed paired, miR-199a-binding site in the Smad4 3'-untranslated region (UTR). Overexpression of miR-199a significantly inhibited the ability of TGF-β to induce gastric cancer cell growth arrest and apoptosis in vitro, and promoted anchorage-independent growth in soft agar, suggesting that miR-199a plays an oncogenic role in human gastric tumourigenesis. In conclusion, our functional screening uncovers multiple miRNAs that regulate the cellular responsiveness to TGF-β signalling and reveals important roles of miR-199a in gastric cancer by directly targeting Smad4.
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Affiliation(s)
- Yan Zhang
- State Key Laboratory of Proteomics, Genetic Laboratory of Development and Disease, Institute of Biotechnology, 20 Dongdajie, Fengtai District, Beijing 100071, China
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294
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Abstract
The canonical TGF-β/Smad signaling pathway was delineated in the mid 90s and enriched over the past decade with many findings about its specificity, regulation, networking, and malfunctions in disease. However, a growing understanding of the chromatin status of a critical class of TGF-β target genes - the genes controlling differentiation of embryonic stem cells - recently prompted a reexamination of this pathway and its critical role in the regulation of stem cell differentiation. The new findings reveal master regulators of the pluripotent state set the stage for Smad-mediated activation of master regulators of the next differentiation stage. Furthermore, a novel branch of the TGF-β/Smad pathway has been identified in which a chromatin-reading Smad complex makes the master differentiation genes accessible to canonical Smad complexes for transcriptional activation. These findings provide exciting new insights into the global role of TGF-β signaling in the regulators of stem cell fate.
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Affiliation(s)
- Joan Massagué
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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295
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Dupont S, Inui M, Newfeld SJ. Regulation of TGF-β signal transduction by mono- and deubiquitylation of Smads. FEBS Lett 2012; 586:1913-20. [PMID: 22710170 PMCID: PMC3383349 DOI: 10.1016/j.febslet.2012.03.037] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 03/17/2012] [Accepted: 03/19/2012] [Indexed: 01/17/2023]
Abstract
Polyubiquitylation leading to proteasomal degradation is a well-established mechanism for regulating TGF-β signal transduction components such as receptors and Smads. Recently, an equally important role was suggested for monoubiquitylation of both Smad4 and receptor-associated Smads that regulates their function without protein degradation. Monoubiquitylation of Smads was discovered following the identification of deubiquitylases required for TGF-β signaling, suggesting that continuous cycles of Smad mono- and deubiquitylation are required for proper TGF-β signal transduction. Here we summarize and discuss recent work on Smad mono- and deubiquitylation.
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Affiliation(s)
- Sirio Dupont
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Masafumi Inui
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Stuart J. Newfeld
- School of Life Sciences, Arizona State University, Tempe AZ 85287-4501, USA
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296
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Warmflash A, Arduini BL, Brivanlou AH. The molecular circuitry underlying pluripotency in embryonic stem cells. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2012; 4:443-56. [PMID: 22761038 DOI: 10.1002/wsbm.1182] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cells in the pluripotent state have the ability to self-renew indefinitely and to differentiate to all the cells of the embryo. These cells provide an in vitro window into development, including human development, as well as holding extraordinary promise for cell-based therapies in regenerative medicine. The recent demonstration that somatic cells can be reprogrammed to the pluripotent state has raised the possibility of patient and disease-specific induced pluripotent cells. In this article, we review the molecular underpinning of pluripotency. We focus on the transcriptional and signaling networks that underlie the state of pluripotency and control differentiation. In general, the action of each of the molecular components and pathways is dose and context dependent highlighting the need for a systems approach to understanding pluripotency.
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Affiliation(s)
- Aryeh Warmflash
- Laboratory of Molecular Vertebrate Embryology, The Rockefeller University, New York, NY, USA
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297
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Stinchfield MJ, Takaesu NT, Quijano JC, Castillo AM, Tiusanen N, Shimmi O, Enzo E, Dupont S, Piccolo S, Newfeld SJ. Fat facets deubiquitylation of Medea/Smad4 modulates interpretation of a Dpp morphogen gradient. Development 2012; 139:2721-9. [PMID: 22745309 DOI: 10.1242/dev.077206] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The ability of secreted Transforming Growth Factor β (TGFβ) proteins to act as morphogens dictates that their influence be strictly regulated. Here, we report that maternally contributed fat facets (faf; a homolog of USP9X/FAM) is essential for proper interpretation of the zygotic Decapentaplegic (Dpp) morphogen gradient that patterns the embryonic dorsal-ventral axis. The data suggest that the loss of faf reduces the activity of Medea (a homolog of Smad4) below the minimum necessary for adequate Dpp signaling and that this is likely due to excessive ubiquitylation on a specific lysine. This study supports the hypothesis that the control of cellular responsiveness to TGFβ signals at the level of Smad4 ubiquitylation is a conserved mechanism required for proper implementation of a morphogen gradient.
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298
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Herquel B, Ouararhni K, Davidson I. The TIF1α-related TRIM cofactors couple chromatin modifications to transcriptional regulation, signaling and tumor suppression. Transcription 2012; 2:231-6. [PMID: 22231120 DOI: 10.4161/trns.2.5.17725] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
TRIM24 (TIF1α), TRIM28 (TIF1β) and TRIM33 (TIF1γ) are related cofactors defining a subgroup of the tripartite motif (TRIM) superfamily comprising an N-terminal RING finger E3 ligase and a C-terminal PHD-Bromodomain chromatin interacting module. Increasing evidence highlights the important roles of these proteins as modulators of multiple signaling pathways during normal development and as tumor suppressors. The finding that they interact to form a multiprotein complex suggests new mechanisms to integrate multiple signaling pathways for tumor suppression.
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Affiliation(s)
- Benjamin Herquel
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch Cédex, France
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299
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Dynamics of TGF-β signaling reveal adaptive and pulsatile behaviors reflected in the nuclear localization of transcription factor Smad4. Proc Natl Acad Sci U S A 2012; 109:E1947-56. [PMID: 22689943 DOI: 10.1073/pnas.1207607109] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The TGF-β pathway plays a vital role in development and disease and regulates transcription through a complex composed of receptor-regulated Smads (R-Smads) and Smad4. Extensive biochemical and genetic studies argue that the pathway is activated through R-Smad phosphorylation; however, the dynamics of signaling remain largely unexplored. We monitored signaling and transcriptional dynamics and found that although R-Smads stably translocate to the nucleus under continuous pathway stimulation, transcription of direct targets is transient. Surprisingly, Smad4 nuclear localization is confined to short pulses that coincide with transcriptional activity. Upon perturbation, the dynamics of transcription correlate with Smad4 nuclear localization rather than with R-Smad activity. In Xenopus embryos, Smad4 shows stereotyped, uncorrelated bursts of nuclear localization, but activated R-Smads are uniform. Thus, R-Smads relay graded information about ligand levels that is integrated with intrinsic temporal control reflected in Smad4 into the active signaling complex.
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300
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Abstract
A dual role of transforming growth factor β (TGF-β), to both suppress and promote tumor progression and metastasis, has been well established, but its molecular basis has remained elusive. In this review, we focus on Smad proteins, which are central mediators of the signal transduction of TGF-β family members. We describe current knowledge of cell-type-specific binding patterns of Smad proteins and mechanisms of transcriptional regulation, obtained from recent studies on genome-wide binding sites of Smad molecules. We also discuss potential application of the genome-wide analyses for cancer research, which will allow clarification of the complex mechanisms occurring during cancer progression, and the identification of potential biomarkers for future cancer diagnosis, prognosis and therapy.
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Affiliation(s)
- M Morikawa
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Biomedical Center, Uppsala, Sweden
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