401
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Affiliation(s)
- Evgenij Fiškin
- Institute of Biochemistry II, Goethe University School of Medicine, Frankfurt am Main, Germany
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402
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Wang Z, Potter CS, Sundberg JP, Hogenesch H. SHARPIN is a key regulator of immune and inflammatory responses. J Cell Mol Med 2013; 16:2271-9. [PMID: 22452937 PMCID: PMC3402681 DOI: 10.1111/j.1582-4934.2012.01574.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Mice with spontaneous mutations in the Sharpin gene develop chronic proliferative dermatitis that is characterized by eosinophilic inflammation of the skin and other organs with increased expression of type 2 cytokines and dysregulated development of lymphoid tissues. The mutant mice share phenotypic features with human hypereosinophilic syndromes. The biological function of SHARPIN and how its absence leads to such a complex inflammatory phenotype in mice are poorly understood. However, recent studies identified SHARPIN as a novel modulator of immune and inflammatory responses. The emerging mechanistic model suggests that SHARPIN functions as an important adaptor component of the linear ubiquitin chain assembly complex that modulates activation of NF-κB signalling pathway, thereby regulating cell survival and apoptosis, cytokine production and development of lymphoid tissues. In this review, we will summarize the current understanding of the ubiquitin-dependent regulatory mechanisms involved in NF-κB signalling, and incorporate the recently obtained molecular insights of SHARPIN into this pathway. Recent studies identified SHARPIN as an inhibitor of β1-integrin activation and signalling, and this may be another mechanism by which SHARPIN regulates inflammation. Furthermore, the disrupted lymphoid organogenesis in SHARPIN-deficient mice suggests that SHARPIN-mediated NF-κB regulation is important for de novo development of lymphoid tissues.
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Affiliation(s)
- Zhe Wang
- Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, West Lafayette, IN 47907-1243, USA
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403
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Diverse roles of the ubiquitin system in NF-κB activation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:129-36. [PMID: 23523932 DOI: 10.1016/j.bbamcr.2013.03.011] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Revised: 02/15/2013] [Accepted: 03/10/2013] [Indexed: 12/13/2022]
Abstract
NF-κB is a transcription factor known to be involved in pleomorphic biological phenomena such as inflammation and immune responses. Abnormal activation of NF-κB has been reported in many pathological conditions, including allergic and auto-inflammatory diseases and malignancies. Therefore, the NF-κB activation pathway has been extensively studied and involvement of the ubiquitin conjugation system in the NF-κB activation pathways has been shown. Also non-degradable roles of the ubiquitin system have been revealed, recently. Several types of polyubiquitin chains exist and the type of chain seems to determine how ubiquitinated proteins are regulated. Roles of non-degradable types of polyubiquitin chains such as K63, linear and K11 chains in NF-κB activation is one of the big issues in NF-κB research. Thus, this short article discusses the differential roles of those polyubiquitin chains in NF-κB activation. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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404
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Ori D, Kato H, Sanjo H, Tartey S, Mino T, Akira S, Takeuchi O. Essential roles of K63-linked polyubiquitin-binding proteins TAB2 and TAB3 in B cell activation via MAPKs. THE JOURNAL OF IMMUNOLOGY 2013; 190:4037-45. [PMID: 23509369 DOI: 10.4049/jimmunol.1300173] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Polyubiquitination of proteins plays a critical role in the activation of immune cells. K63-linked polyubiquitin-binding proteins TGF-β-activated kinase 1 (TAK1)-binding protein (TAB)2 and TAB3 are implicated in NF-κB signaling via TAK1 activation. However, TAB2 alone is dispensable for NF-κB activation in embryonic fibroblasts, and the functional roles of TAB2 and TAB3 in immune cells has yet to be clarified. In this study, we demonstrate that TAB2 and TAB3 are essential for B cell activation leading to Ag-specific Ab responses, as well as B-1 and marginal zone B cell development. TAB2 and TAB3 are critical for the activation of MAPKs, especially ERK, but not NF-κB, in response to TLR and CD40 stimulation in B cells. Surprisingly, TAB2 and TAB3 are dispensable for TAK1 activation in B cells, indicating that TAB2 and TAB3 activate MAPKs via a pathway independent of TAK1. In contrast to B cells, macrophages lacking TAB2 and TAB3 did not show any defects in the cytokine production and the signaling pathway in response to TLR stimulation. Furthermore, TAB2 and TAB3 were dispensable for TNF-induced cytokine production in embryonic fibroblasts. Thus, TAB2- and TAB3-mediated K63-linked polyubiquitin recognition controls B cell activation via MAPKs, but not the TAK1/NF-κB axis.
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Affiliation(s)
- Daisuke Ori
- Laboratory of Infection and Prevention, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
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405
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Müller-Rischart A, Pilsl A, Beaudette P, Patra M, Hadian K, Funke M, Peis R, Deinlein A, Schweimer C, Kuhn PH, Lichtenthaler S, Motori E, Hrelia S, Wurst W, Trümbach D, Langer T, Krappmann D, Dittmar G, Tatzelt J, Winklhofer K. The E3 Ligase Parkin Maintains Mitochondrial Integrity by Increasing Linear Ubiquitination of NEMO. Mol Cell 2013; 49:908-21. [DOI: 10.1016/j.molcel.2013.01.036] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 12/05/2012] [Accepted: 01/25/2013] [Indexed: 01/01/2023]
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406
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Seymour R, Shirley BJ, Hogenesch H, Shultz LD, Sundberg JP. Loss of function of the mouse Sharpin gene results in Peyer's patch regression. PLoS One 2013; 8:e55224. [PMID: 23424624 PMCID: PMC3570409 DOI: 10.1371/journal.pone.0055224] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 12/27/2012] [Indexed: 01/13/2023] Open
Abstract
Peyer’s patches (PP) are an important component in the immune response against intestinal pathogens. Two independent, spontaneous mutations in the mouse Sharpin gene (Sharpincpdm and Sharpincpdm-Dem) result in the absence of PP and disrupted splenic white pulp in adult mice, although a full complement of lymph nodes is present. Here we report that rudimentary PP begin to develop in Sharpincpdm mice during embryogenesis, but lack the organizational patterns that are typical of this tissue. In the present study, small intestines examined at weekly intervals from birth to maturity showed spontaneous regression of PP in mutant mice with concurrent infiltration of granulocytes. At 5 to 6 weeks of age, only indistinct remnants of granulocytic accumulations remain. Transplantation of normal bone marrow into Sharpincpdm mice at 7 days of age did not prevent regression of PP in bone marrow chimeras examined at 7 to 8 weeks of age. These findings indicate that SHARPIN expression is required for the normal development and maintenance, but not initiation, of PP.
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Affiliation(s)
- Rosemarie Seymour
- The Jackson Laboratory, Bar Harbor, Maine, United States of America.
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407
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p47 negatively regulates IKK activation by inducing the lysosomal degradation of polyubiquitinated NEMO. Nat Commun 2013; 3:1061. [PMID: 22990857 DOI: 10.1038/ncomms2068] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 08/15/2012] [Indexed: 12/18/2022] Open
Abstract
The persistent or excess activation of NF-κB causes various inflammatory and autoimmune diseases, but the molecular mechanisms that negatively regulate NF-κB activation are not fully understood. Here we show that p47, an essential factor for Golgi membrane fusion, associates with the NEMO subunit of the IκB kinase (IKK) complex upon TNF-α or IL-1 stimulation, and inhibits IKK activation. p47 binds to Lys63-linked and linear polyubiquitin chains, which are conjugated to NEMO upon such stimulation. The binding of p47 to polyubiquitinated NEMO triggers the lysosomal degradation of NEMO, thereby inhibiting IKK activation. The silencing of p47 results in enhanced TNF-α- or IL-1-induced IKK activation, and an increased expression of genes encoding inflammatory mediators. Taken together, our results suggest that p47 is critical for negatively regulating stimulation-induced IKK activation in a manner that is mechanistically distinct from the previously characterized negative regulators, such as A20 and CYLD.
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408
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Abstract
The nuclear factor κ enhancer binding protein (NF-κB) family of transcription factors regulates the expression of a large array of genes involved in diverse cellular processes including inflammation, immunity and cell survival. Activation of NF-κB requires ubiquitination, a highly conserved and versatile modification that can regulate cell signaling through both proteasome dependent and independent mechanisms. Studies in the past few years have provided new insights into the mechanisms underlying regulation of NF-κB by ubiquitination, including the involvement of multiple linkages of ubiquitin, the essential role of ubiquitin binding, and the function of unanchored polyubiquitin chains. In this review, we will focus on recent advances in understanding the role of ubiquitination in NF-κB regulation in various pathways.
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Affiliation(s)
- Jueqi Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, United States
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409
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Silke J, Meier P. Inhibitor of apoptosis (IAP) proteins-modulators of cell death and inflammation. Cold Spring Harb Perspect Biol 2013; 5:5/2/a008730. [PMID: 23378585 DOI: 10.1101/cshperspect.a008730] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Misregulated innate immune signaling and cell death form the basis of much human disease pathogenesis. Inhibitor of apoptosis (IAP) protein family members are frequently overexpressed in cancer and contribute to tumor cell survival, chemo-resistance, disease progression, and poor prognosis. Although best known for their ability to regulate caspases, IAPs also influence ubiquitin (Ub)-dependent pathways that modulate innate immune signaling via activation of nuclear factor κB (NF-κB). Recent research into IAP biology has unearthed unexpected roles for this group of proteins. In addition, the advances in our understanding of the molecular mechanisms that IAPs use to regulate cell death and innate immune responses have provided new insights into disease states and suggested novel intervention strategies. Here we review the functions assigned to those IAP proteins that act at the intersection of cell death regulation and inflammatory signaling.
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Affiliation(s)
- John Silke
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3052, Australia.
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410
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Rieser E, Cordier SM, Walczak H. Linear ubiquitination: a newly discovered regulator of cell signalling. Trends Biochem Sci 2013; 38:94-102. [DOI: 10.1016/j.tibs.2012.11.007] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 11/14/2012] [Accepted: 11/28/2012] [Indexed: 10/27/2022]
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411
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Belgnaoui SM, Paz S, Samuel S, Goulet ML, Sun Q, Kikkert M, Iwai K, Dikic I, Hiscott J, Lin R. Linear ubiquitination of NEMO negatively regulates the interferon antiviral response through disruption of the MAVS-TRAF3 complex. Cell Host Microbe 2013; 12:211-22. [PMID: 22901541 DOI: 10.1016/j.chom.2012.06.009] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/30/2012] [Accepted: 06/14/2012] [Indexed: 01/07/2023]
Abstract
The RIG-I/Mda5 sensors recognize viral intracellular RNA and trigger host antiviral responses. RIG-I signals through the adaptor protein MAVS, which engages various TRAF family members and results in type I interferon (IFNs) and proinflammatory cytokine production via activation of IRFs and NF-κB, respectively. Both the IRF and NF-κB pathways also require the adaptor protein NEMO. We determined that the RIG-I pathway is differentially regulated by the linear ubiquitin assembly complex (LUBAC), which consists of the E3 ligases HOIL-1L, HOIP, and the accessory protein SHARPIN. LUBAC downregulated virus-mediated IFN induction by targeting NEMO for linear ubiquitination. Linear ubiquitinated NEMO associated with TRAF3 and disrupted the MAVS-TRAF3 complex, which inhibited IFN activation while stimulating NF-κB-dependent signaling. In SHARPIN-deficient MEFs, vesicular stomatitis virus replication was decreased due to increased IFN production. Linear ubiquitination thus switches NEMO from a positive to a negative regulator of RIG-I signaling, resulting in an attenuated IFN response.
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Affiliation(s)
- S Mehdi Belgnaoui
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Canada
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412
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Warner N, Burberry A, Franchi L, Kim YG, McDonald C, Sartor MA, Núñez G. A genome-wide siRNA screen reveals positive and negative regulators of the NOD2 and NF-κB signaling pathways. Sci Signal 2013; 6:rs3. [PMID: 23322906 DOI: 10.1126/scisignal.2003305] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The cytoplasmic receptor NOD2 (nucleotide-binding oligomerization domain 2) senses peptidoglycan fragments and triggers host defense pathways, including activation of nuclear factor κB (NF-κB) signaling, which lead to inflammatory immune responses. Dysregulation of NOD2 signaling is associated with inflammatory diseases, such as Crohn's disease and Blau syndrome. We used a genome-wide small interfering RNA screen to identify regulators of the NOD2 signaling pathway. Several genes associated with Crohn's disease risk were identified in the screen. A comparison of candidates from this screen with other "omics" data sets revealed interconnected networks of genes implicated in NF-κB signaling, thus supporting a role for NOD2 and NF-κB pathways in the pathogenesis of Crohn's disease. Many of these regulators were validated in secondary assays, such as measurement of interleukin-8 secretion, which is partially dependent on NF-κB. Knockdown of putative regulators in human embryonic kidney 293 cells followed by stimulation with tumor necrosis factor-α revealed that most of the genes identified were general regulators of NF-κB signaling. Overall, the genes identified here provide a resource to facilitate the elucidation of the molecular mechanisms that regulate NOD2- and NF-κB-mediated inflammation.
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Affiliation(s)
- Neil Warner
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
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413
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Aillet F, Lopitz-Otsoa F, Egaña I, Hjerpe R, Fraser P, Hay RT, Rodriguez MS, Lang V. Heterologous SUMO-2/3-ubiquitin chains optimize IκBα degradation and NF-κB activity. PLoS One 2012; 7:e51672. [PMID: 23284737 PMCID: PMC3527444 DOI: 10.1371/journal.pone.0051672] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 11/05/2012] [Indexed: 01/09/2023] Open
Abstract
The NF-κB pathway is regulated by SUMOylation at least at three levels: the inhibitory molecule IκBα, the IKK subunit γ/NEMO and the p52 precursor p100. Here we investigate the role of SUMO-2/3 in the degradation of IκBα and activation of NF-κB mediated by TNFα. We found that under conditions of deficient SUMOylation, an important delay in both TNFα-mediated proteolysis of IκBα and NF-κB dependent transcription occurs. In vitro and ex vivo approaches, including the use of ubiquitin-traps (TUBEs), revealed the formation of chains on IκBα containing SUMO-2/3 and ubiquitin after TNFα stimulation. The integration of SUMO-2/3 appears to promote the formation of ubiquitin chains on IκBα after activation of the TNFα signalling pathway. Furthermore, heterologous chains of SUMO-2/3 and ubiquitin promote a more efficient degradation of IκBα by the 26S proteasome in vitro compared to chains of either SUMO-2/3 or ubiquitin alone. Consistently, Ubc9 silencing reduced the capture of IκBα modified with SUMO-ubiquitin hybrid chains that display a defective proteasome-mediated degradation. Thus, hybrid SUMO-2/3-ubiquitin chains increase the susceptibility of modified IκBα to the action of 26S proteasome, contributing to the optimal control of NF-κB activity after TNFα-stimulation.
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Affiliation(s)
- Fabienne Aillet
- Proteomics Unit, CIC bioGUNE, CIBERehd, Derio, Bizkaia, Spain
- Ubiquitylation & Cancer Molecular Biology Laboratory, Inbiomed, San Sebastián-Donostia, Gipuzkoa, Spain
| | | | - Isabel Egaña
- Proteomics Unit, CIC bioGUNE, CIBERehd, Derio, Bizkaia, Spain
| | - Roland Hjerpe
- Proteomics Unit, CIC bioGUNE, CIBERehd, Derio, Bizkaia, Spain
| | - Paul Fraser
- Tanz Centre for Research in Neurodegenerative Diseases and Department of Medical Biophysics, University of Toronto, Ontario, Canada
| | - Ron T. Hay
- Centre for Interdisciplinary Research, School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
| | | | - Valérie Lang
- Proteomics Unit, CIC bioGUNE, CIBERehd, Derio, Bizkaia, Spain
- Ubiquitylation & Cancer Molecular Biology Laboratory, Inbiomed, San Sebastián-Donostia, Gipuzkoa, Spain
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414
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Gustafsson Sheppard N, Heldring N, Dahlman-Wright K. Estrogen receptor-α, RBCK1, and protein kinase C β 1 cooperate to regulate estrogen receptor-α gene expression. J Mol Endocrinol 2012; 49:277-87. [PMID: 23042805 DOI: 10.1530/jme-12-0073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Estrogen receptor α (ERα) is initially overexpressed in two-thirds of all breast cancers and is involved in its development and proliferation. We previously reported that the RanBP-type and C3HC4-type zinc finger containing 1 (RBCK1) interacts with the ERα promoter and that RBCK1 expression positively correlates with ERα levels, expression of ERα downstream target genes, and proliferation of breast cancer cells. Based on this, and that RBCK1 positively correlates with ERα expression in breast cancer samples, we propose RBCK1 as a potential therapeutic target in breast cancer acting as a modulator of ERα expression. To further explore this, the molecular mechanism by which RBCK1 regulates ERα expression has to be defined. Here, we show that ERα, RBCK1, and the RBCK1-interacting protein protein kinase C β 1 (PKCβ(I)) co-occupy a previously identified ERα binding region in the proximal ERα promoter. We describe a number of mechanistic details of this complex including that RBCK1 recruitment to the ERα promoter B is facilitated by ERα, which in turn facilitates PKCβ(I) recruitment and PKCβ(I)-dependent histone modifications. Furthermore, ERα regulation of its own mRNA expression is facilitated by RBCK1 recruitment, suggesting an ERα coactivator function of RBCK1. The interaction between RBCK1 and ERα was dependent on the E3 ubiquitin ligase domain of RBCK1 and the activating function-1 domain of ERα. The ligand-binding function of ERα does not influence the interaction with RBCK1. In summary, our data provide insight into the molecular mechanism by which ERα expression is modulated in breast cancer cells.
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Affiliation(s)
- Nina Gustafsson Sheppard
- Department of Biosciences and Nutrition, Karolinska Institute, NOVUM, S-14183 Huddinge, Stockholm, Sweden.
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415
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Gonzalvez F, Lawrence D, Yang B, Yee S, Pitti R, Marsters S, Pham VC, Stephan JP, Lill J, Ashkenazi A. TRAF2 Sets a threshold for extrinsic apoptosis by tagging caspase-8 with a ubiquitin shutoff timer. Mol Cell 2012; 48:888-99. [PMID: 23142077 DOI: 10.1016/j.molcel.2012.09.031] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 08/28/2012] [Accepted: 09/27/2012] [Indexed: 11/16/2022]
Abstract
Apoptotic caspase activation mechanisms are well defined, yet inactivation modes remain unclear. The death receptors (DRs), DR4, DR5, and Fas, transduce cell-extrinsic apoptotic signals by recruiting caspase-8 into a death-inducing signaling complex (DISC). At the DISC, Cullin3-dependent polyubiquitination on the small catalytic subunit of caspase-8 augments stimulation. Here we report that tumor necrosis factor receptor-associated factor 2 (TRAF2) interacts with caspase-8 at the DISC, downstream of Cullin3. TRAF2 directly mediates RING-dependent, K48-linked polyubiquitination on the large catalytic domain of caspase-8. This modification destines activated caspase-8 molecules to rapid proteasomal degradation upon autoprocessing and cytoplasmic translocation. TRAF2 depletion lowers the signal threshold for DR-mediated apoptosis, altering cell life versus death decisions in vitro and in vivo. Thus, TRAF2 sets a critical barrier for cell-extrinsic apoptosis commitment by tagging activated caspase-8 with a K48-ubiquitin shutoff timer. These results may have important implications for caspase regulation mechanisms.
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Affiliation(s)
- Francois Gonzalvez
- Department of Molecular Oncology, Genentech Inc., South San Francisco, CA 94080, USA
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416
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Kravtsova-Ivantsiv Y, Sommer T, Ciechanover A. The lysine48-based polyubiquitin chain proteasomal signal: not a single child anymore. Angew Chem Int Ed Engl 2012; 52:192-8. [PMID: 23124625 DOI: 10.1002/anie.201205656] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Indexed: 11/07/2022]
Abstract
The conjugation of ubiquitin (Ub) to proteins is involved in the regulation of many processes. The modification serves as a recognition element in trans, in which downstream effectors bind to the modified protein and determine its fate and/or function. A polyUb chain that is linked through internal lysine (Lys)-48 of Ub and anchored to an internal Lys residue of the substrate has become the accepted "canonical" signal for proteasomal targeting and degradation. However, recent studies show that the signal is far more diverse and that chains based on other internal linkages, as well as linear or heterologous chains made of Ub and Ub-like proteins and even monoUb, are recognized by the proteasome. In addition, chains linked to residues other than internal Lys were described, all challenging the current paradigm.
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Affiliation(s)
- Yelena Kravtsova-Ivantsiv
- Cancer and Vascular Biology Research Center, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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417
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Boisson B, Laplantine E, Prando C, Giliani S, Israelsson E, Xu Z, Abhyankar A, Israël L, Trevejo-Nunez G, Bogunovic D, Cepika AM, MacDuff D, Chrabieh M, Hubeau M, Bajolle F, Debré M, Mazzolari E, Vairo D, Agou F, Virgin HW, Bossuyt X, Rambaud C, Facchetti F, Bonnet D, Quartier P, Fournet JC, Pascual V, Chaussabel D, Notarangelo LD, Puel A, Israël A, Casanova JL, Picard C. Immunodeficiency, autoinflammation and amylopectinosis in humans with inherited HOIL-1 and LUBAC deficiency. Nat Immunol 2012; 13:1178-86. [PMID: 23104095 PMCID: PMC3514453 DOI: 10.1038/ni.2457] [Citation(s) in RCA: 336] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 09/24/2012] [Indexed: 12/25/2022]
Abstract
We report the clinical description and molecular dissection of a new fatal human inherited disorder characterized by chronic auto-inflammation, invasive bacterial infections and muscular amylopectinosis. Patients from two kindreds carried biallelic loss-of-expression and loss-of-function mutations in HOIL1, a component the linear ubiquitination chain assembly complex (LUBAC). These mutations resulted in impairment of LUBAC stability. NF-κB activation in response to interleukin-1β (IL-1β) was compromised in the patients’ fibroblasts. By contrast, the patients’ mononuclear leukocytes, particularly monocytes, were hyperresponsive to IL-1β. The consequences of human HOIL-1 and LUBAC deficiencies for IL-1β responses thus differed between cell types, consistent with the unique association of auto-inflammation and immunodeficiency in these patients. These data suggest that LUBAC regulates NF-κB-dependent IL-1β responses differently in different cell types.
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Affiliation(s)
- Bertrand Boisson
- St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, Rockefeller University, New York, New York, USA
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418
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Abstract
Tumor necrosis factor (TNF) is a critical cytokine, which contributes to both physiological and pathological processes. This mini-review will briefly touch the history of TNF discovery, its family members and its biological and pathological functions. Then, it will focus on new findings on the molecular mechanisms of how TNF triggers activation of the NF-κB and AP-1 pathways, which are critical for expression of pro-inflammatory cytokines, as well as the MLKL cascade, which is critical for the generation of ROS in response to TNF. Finally, this review will briefly summarize recent advances in understanding TNF-induced cell survival, apoptosis and necrosis (also called necroptosis). Understanding new findings and emerging concepts will impact future research on the molecular mechanisms of TNF signaling in immune disorders and cancer-related inflammation.
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Affiliation(s)
- Wen-Ming Chu
- Cancer Biology Program, University of Hawaii Cancer Center, 651 Ilalo Street, Honolulu, HI 96813, USA.
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419
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Chapard C, Hohl D, Huber M. The role of the TRAF-interacting protein in proliferation and differentiation. Exp Dermatol 2012; 21:321-6. [PMID: 22509826 DOI: 10.1111/j.1600-0625.2012.01477.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ubiquitination of proteins is a post-translational modification, which decides on the cellular fate of the protein. Addition of ubiquitin moieties to proteins is carried out by the sequential action of three enzymes: E1, ubiquitin-activating enzyme; E2, ubiquitin-conjugating enzyme; and E3, ubiquitin ligase. The TRAF-interacting protein (TRAIP, TRIP, RNF206) functions as Really Interesting New Gene (RING)-type E3 ubiquitin ligase, but its physiological substrates are not yet known. TRAIP was reported to interact with TRAF [tumor necrosis factor (TNF) receptor-associated factors] and the two tumor suppressors CYLD and Syk (spleen tyrosine kinase). Ectopically expressed TRAIP was shown to inhibit nuclear factor-kappa B (NF-κB) signalling. However, recent results suggested a role for TRAIP in biological processes other than NF-κB regulation. Knock-down of TRAIP in human epidermal keratinocytes repressed cellular proliferation and induced a block in the G1/S phase of the cell cycle without affecting NF-κB signalling. TRAIP is necessary for embryonal development as mutations affecting the Drosophila homologue of TRAIP are maternal effect-lethal mutants, and TRAIP knock-out mice die in utero because of aberrant regulation of cell proliferation and apoptosis. These findings underline the tight link between TRAIP and cell proliferation. In this review, we summarize the data on TRAIP and put them into a larger perspective regarding the role of TRAIP in the control of tissue homeostasis.
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Affiliation(s)
- Christophe Chapard
- Service of Dermatology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
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420
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421
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Kravtsova-Ivantsiv Y, Ciechanover A. Non-canonical ubiquitin-based signals for proteasomal degradation. J Cell Sci 2012; 125:539-48. [PMID: 22389393 DOI: 10.1242/jcs.093567] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Regulated cellular proteolysis is mediated largely by the ubiquitin-proteasome system (UPS). It is a highly specific process that is time- (e.g. cell cycle), compartment- (e.g. nucleus or endoplasmic reticulum) and substrate quality- (e.g. denatured or misfolded proteins) dependent, and allows fast adaptation to changing conditions. Degradation by the UPS is carried out through two successive steps: the substrate is covalently tagged with ubiquitin and subsequently degraded by the 26S proteasome. The accepted 'canonical' signal for proteasomal recognition is a polyubiquitin chain that is anchored to a lysine residue in the target substrate, and is assembled through isopeptide bonds involving lysine 48 of ubiquitin. However, several 'non-canonical' ubiquitin-based signals for proteasomal targeting have also been identified. These include chains anchored to residues other than internal lysine in the substrates, chains assembled through linking residues other than lysine 48 in ubiquitin, and mixed chains made of both ubiquitin and a ubiquitin-like protein. Furthermore, some proteins can be degraded following modification by a single ubiquitin (monoubiquitylation) or multiple single ubiquitins (multiple monoubiquitylation). Finally, some proteins can be proteasomally degraded without prior ubiquitylation (the process is also often referred to as ubiquitination). In this Commentary, we describe these recent findings and discuss the possible physiological roles of these diverse signals. Furthermore, we discuss the possible impact of this signal diversity on drug development.
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Affiliation(s)
- Yelena Kravtsova-Ivantsiv
- Cancer and Vascular Biology Research Center, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Efron Street, Bat Galim, PO Box 9649, Haifa 31096, Israel.
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422
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Walden H, Martinez-Torres RJ. Regulation of Parkin E3 ubiquitin ligase activity. Cell Mol Life Sci 2012; 69:3053-67. [PMID: 22527713 PMCID: PMC11115052 DOI: 10.1007/s00018-012-0978-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 03/20/2012] [Accepted: 03/22/2012] [Indexed: 11/28/2022]
Abstract
Parkin is an E3 ubiquitin ligase mutated in autosomal recessive juvenile Parkinson's disease. In addition, it is a putative tumour suppressor, and has roles outside its enzymatic activity. It is critical for mitochondrial clearance through mitophagy, and is an essential protein in most eukaryotes. As such, it is a tightly controlled protein, regulated through an array of external interactions with multiple proteins, posttranslational modifications including phosphorylation and S-nitrosylation, and self-regulation through internal associations. In this review, we highlight some of the recent studies into Parkin regulation and discuss future challenges for gaining a full molecular understanding of the regulation of Parkin E3 ligase activity.
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Affiliation(s)
- Helen Walden
- Protein Structure and Function Laboratory, London Research Institute of Cancer Research UK, Lincoln's Inn Fields Laboratories, London, UK.
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423
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Stieglitz B, Morris-Davies AC, Koliopoulos MG, Christodoulou E, Rittinger K. LUBAC synthesizes linear ubiquitin chains via a thioester intermediate. EMBO Rep 2012; 13:840-6. [PMID: 22791023 PMCID: PMC3432797 DOI: 10.1038/embor.2012.105] [Citation(s) in RCA: 179] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 06/21/2012] [Accepted: 06/22/2012] [Indexed: 01/31/2023] Open
Abstract
The linear ubiquitin chain assembly complex (LUBAC) is a RING E3 ligase that regulates immune and inflammatory signalling pathways. Unlike classical RING E3 ligases, LUBAC determines the type of ubiquitin chain being formed, an activity normally associated with the E2 enzyme. We show that the RING-in-between-RING (RBR)-containing region of HOIP--the catalytic subunit of LUBAC--is sufficient to generate linear ubiquitin chains. However, this activity is inhibited by the N-terminal portion of the molecule, an inhibition that is released upon complex formation with HOIL-1L or SHARPIN. Furthermore, we demonstrate that HOIP transfers ubiquitin to the substrate through a thioester intermediate formed by a conserved cysteine in the RING2 domain, supporting the notion that RBR ligases act as RING/HECT hybrids.
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Affiliation(s)
- Benjamin Stieglitz
- Division of Molecular Structure, MRC-National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
| | - Aylin C Morris-Davies
- Division of Molecular Structure, MRC-National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
| | - Marios G Koliopoulos
- Division of Molecular Structure, MRC-National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
| | - Evangelos Christodoulou
- Division of Molecular Structure, MRC-National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
| | - Katrin Rittinger
- Division of Molecular Structure, MRC-National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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424
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Liechtenstein T, Dufait I, Lanna A, Breckpot K, Escors D. MODULATING CO-STIMULATION DURING ANTIGEN PRESENTATION TO ENHANCE CANCER IMMUNOTHERAPY. IMMUNOLOGY, ENDOCRINE & METABOLIC AGENTS IN MEDICINAL CHEMISTRY 2012; 12:224-235. [PMID: 22945252 PMCID: PMC3428911 DOI: 10.2174/187152212802001875] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
One of the key roles of the immune system is the identification of potentially dangerous pathogens or tumour cells, and raising a wide range of mechanisms to eliminate them from the organism. One of these mechanisms is activation and expansion of antigen-specific cytotoxic T cells, after recognition of antigenic peptides on the surface of antigen presenting cells such as dendritic cells (DCs). However, DCs also process and present autoantigens. Therefore, antigen presentation has to occur in the appropriate context to either trigger immune responses or establishing immunological tolerance. This is achieved by co-stimulation of T cells during antigen presentation. Co-stimulation consists on the simultaneous binding of ligand-receptor molecules at the immunological synapse which will determine the type and extent of T cell responses. In addition, the type of cytokines/chemokines present during antigen presentation will influence the polarisation of T cell responses, whether they lead to tolerance, antibody responses or cytotoxicity. In this review, we will focus on approaches manipulating co-stimulation during antigen presentation, and the role of cytokine stimulation on effective T cell responses. More specifically, we will address the experimental strategies to interfere with negative co-stimulation such as that mediated by PD-L1 (Programmed cell death 1 ligand 1)/PD-1 (Programmed death 1) to enhance anti-tumour immunity.
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Affiliation(s)
- Therese Liechtenstein
- Division of Infection and Immunity. Rayne Institute. University College London. 5 University Street. WC1E 6JF. London. United Kingdom
| | - Ines Dufait
- Division of Infection and Immunity. Rayne Institute. University College London. 5 University Street. WC1E 6JF. London. United Kingdom
- Department of Physiology-Immunology. Medical School. Free University of Brussels. Laarbeeklaan 103. 1090 Jette. Belgium
| | - Alessio Lanna
- Division of Infection and Immunity. Rayne Institute. University College London. 5 University Street. WC1E 6JF. London. United Kingdom
| | - Karine Breckpot
- Department of Physiology-Immunology. Medical School. Free University of Brussels. Laarbeeklaan 103. 1090 Jette. Belgium
| | - David Escors
- Division of Infection and Immunity. Rayne Institute. University College London. 5 University Street. WC1E 6JF. London. United Kingdom
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425
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Specific recognition of linear polyubiquitin by A20 zinc finger 7 is involved in NF-κB regulation. EMBO J 2012; 31:3856-70. [PMID: 23032187 DOI: 10.1038/emboj.2012.241] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 08/03/2012] [Indexed: 11/08/2022] Open
Abstract
LUBAC (linear ubiquitin chain assembly complex) activates the canonical NF-κB pathway through linear polyubiquitination of NEMO (NF-κB essential modulator, also known as IKKγ) and RIP1. However, the regulatory mechanism of LUBAC-mediated NF-κB activation remains elusive. Here, we show that A20 suppresses LUBAC-mediated NF-κB activation by binding linear polyubiquitin via the C-terminal seventh zinc finger (ZF7), whereas CYLD suppresses it through deubiquitinase (DUB) activity. We determined the crystal structures of A20 ZF7 in complex with linear diubiquitin at 1.70-1.98 Å resolutions. The crystal structures revealed that A20 ZF7 simultaneously recognizes the Met1-linked proximal and distal ubiquitins, and that genetic mutations associated with B cell lymphomas map to the ubiquitin-binding sites. Our functional analysis indicated that the binding of A20 ZF7 to linear polyubiquitin contributes to the recruitment of A20 into a TNF receptor (TNFR) signalling complex containing LUBAC and IκB kinase (IKK), which results in NF-κB suppression. These findings provide new insight into the regulation of immune and inflammatory responses.
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426
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A20 inhibits LUBAC-mediated NF-κB activation by binding linear polyubiquitin chains via its zinc finger 7. EMBO J 2012; 31:3845-55. [PMID: 23032186 DOI: 10.1038/emboj.2012.240] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 08/03/2012] [Indexed: 12/20/2022] Open
Abstract
Linear polyubiquitination of proteins has recently been implicated in NF-κB signalling and is mediated by the linear ubiquitin chain assembly complex (LUBAC), consisting of HOIL-1, HOIP and Sharpin. However, the mechanisms that regulate linear ubiquitination are still unknown. Here, we show that A20 is rapidly recruited to NEMO and LUBAC upon TNF stimulation and that A20 inhibits LUBAC-induced NF-κB activation via its C-terminal zinc-finger 7 (ZF7) domain. Expression of a polypeptide corresponding to only ZF7 was sufficient to inhibit TNF-induced NF-κB activation. Both A20 and ZF7 can form a complex with NEMO and LUBAC, and are able to prevent the TNF-induced binding of NEMO to LUBAC. Finally, we show that ZF7 preferentially binds linear polyubiquitin chains in vitro, indicating A20-ZF7 as a novel linear ubiquitin-binding domain (LUBID). We thus propose a model in which A20 inhibits TNF- and LUBAC-induced NF-κB signalling by binding to linear polyubiquitin chains via its seventh zinc finger, which prevents the TNF-induced interaction between LUBAC and NEMO.
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427
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Smit JJ, Monteferrario D, Noordermeer SM, van Dijk WJ, van der Reijden BA, Sixma TK. The E3 ligase HOIP specifies linear ubiquitin chain assembly through its RING-IBR-RING domain and the unique LDD extension. EMBO J 2012; 31:3833-44. [PMID: 22863777 PMCID: PMC3463842 DOI: 10.1038/emboj.2012.217] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 07/16/2012] [Indexed: 11/18/2022] Open
Abstract
Like Parkin, the linear ubiquitin chain assembly complex LUBAC functions as a RING/HECT-hybrid ubiquitin ligase, but includes a unique extension that dictates linear ubiquitin linkage specificity. Activation of the NF-κB pathway requires the formation of Met1-linked ‘linear' ubiquitin chains on NEMO, which is catalysed by the Linear Ubiquitin Chain Assembly Complex (LUBAC) E3 consisting of HOIP, HOIL-1L and Sharpin. Here, we show that both LUBAC catalytic activity and LUBAC specificity for linear ubiquitin chain formation are embedded within the RING-IBR-RING (RBR) ubiquitin ligase subunit HOIP. Linear ubiquitin chain formation by HOIP proceeds via a two-step mechanism involving both RING and HECT E3-type activities. RING1-IBR catalyses the transfer of ubiquitin from the E2 onto RING2, to transiently form a HECT-like covalent thioester intermediate. Next, the ubiquitin is transferred from HOIP onto the N-terminus of a target ubiquitin. This transfer is facilitated by a unique region in the C-terminus of HOIP that we termed ‘Linear ubiquitin chain Determining Domain' (LDD), which may coordinate the acceptor ubiquitin. Consistent with this mechanism, the RING2-LDD region was found to be important for NF-κB activation in cellular assays. These data show how HOIP combines a general RBR ubiquitin ligase mechanism with unique, LDD-dependent specificity for producing linear ubiquitin chains.
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Affiliation(s)
- Judith J Smit
- Division of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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428
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Kulathu Y, Komander D. Atypical ubiquitylation - the unexplored world of polyubiquitin beyond Lys48 and Lys63 linkages. Nat Rev Mol Cell Biol 2012; 13:508-23. [PMID: 22820888 DOI: 10.1038/nrm3394] [Citation(s) in RCA: 498] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ubiquitylation is one of the most abundant and versatile post-translational modifications (PTMs) in cells. Its versatility arises from the ability of ubiquitin to form eight structurally and functionally distinct polymers, in which ubiquitin moieties are linked via one of seven Lys residues or the amino terminus. Whereas the roles of Lys48- and Lys63-linked polyubiquitin in protein degradation and cellular signalling are well characterized, the functions of the remaining six 'atypical' ubiquitin chain types (linked via Lys6, Lys11, Lys27, Lys29, Lys33 and Met1) are less well defined. Recent developments provide insights into the mechanisms of ubiquitin chain assembly, recognition and hydrolysis and allow detailed analysis of the functions of atypical ubiquitin chains. The importance of Lys11 linkages and Met1 linkages in cell cycle regulation and nuclear factor-κB activation, respectively, highlight that the different ubiquitin chain types should be considered as functionally independent PTMs.
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Affiliation(s)
- Yogesh Kulathu
- Medical Research Council (MRC) Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK
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429
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Pouwels J, Nevo J, Pellinen T, Ylänne J, Ivaska J. Negative regulators of integrin activity. J Cell Sci 2012; 125:3271-80. [PMID: 22822081 DOI: 10.1242/jcs.093641] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Integrins are heterodimeric transmembrane adhesion receptors composed of α- and β-subunits. They are ubiquitously expressed and have key roles in a number of important biological processes, such as development, maintenance of tissue homeostasis and immunological responses. The activity of integrins, which indicates their affinity towards their ligands, is tightly regulated such that signals inside the cell cruicially regulate the switching between active and inactive states. An impaired ability to activate integrins is associated with many human diseases, including bleeding disorders and immune deficiencies, whereas inappropriate integrin activation has been linked to inflammatory disorders and cancer. In recent years, the molecular details of integrin 'inside-out' activation have been actively investigated. Binding of cytoplasmic proteins, such as talins and kindlins, to the cytoplasmic tail of β-integrins is widely accepted as being the crucial step in integrin activation. By contrast, much less is known with regard to the counteracting mechanism involved in switching integrins into an inactive conformation. In this Commentary, we aim to discuss the known mechanisms of integrin inactivation and the molecules involved.
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Affiliation(s)
- Jeroen Pouwels
- Centre for Biotechnology, University of Turku, Turku, Finland
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430
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van Wijk SJL, Fiskin E, Putyrski M, Pampaloni F, Hou J, Wild P, Kensche T, Grecco HE, Bastiaens P, Dikic I. Fluorescence-based sensors to monitor localization and functions of linear and K63-linked ubiquitin chains in cells. Mol Cell 2012; 47:797-809. [PMID: 22819327 DOI: 10.1016/j.molcel.2012.06.017] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 05/02/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
Ubiquitin chains modify a major subset of the proteome, but detection of ubiquitin signaling dynamics and localization is limited due to a lack of appropriate tools. Here, we employ ubiquitin-binding domain (UBD)-based fluorescent sensors to monitor linear and K63-linked chains in vitro and in vivo. We utilize the UBD in NEMO and ABIN (UBAN) for detection of linear chains, and RAP80 ubiquitin-interacting motif (UIM) and TAB2 Npl4 zinc finger (NZF) domains to detect K63 chains. Linear and K63 sensors decorated the ubiquitin coat surrounding cytosolic Salmonella during bacterial autophagy, whereas K63 sensors selectively monitored Parkin-induced mitophagy and DNA damage responses in fixed and living cells. In addition, linear and K63 sensors could be used to monitor endogenous signaling pathways, as demonstrated by their ability to differentially interfere with TNF- and IL-1-induced NF-κB pathway. We propose that UBD-based biosensors could serve as prototypes to track and trace other chain types and ubiquitin-like signals in vivo.
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Affiliation(s)
- Sjoerd J L van Wijk
- Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
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431
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Abstract
The nuclear factor-κB (NF-κB) pathway is a critical regulator of innate and adaptive immunity. Noncanonical K63-linked polyubiquitination plays a key regulatory role in NF-κB signaling pathways by functioning as a scaffold to recruit kinase complexes containing ubiquitin-binding domains. Ubiquitination is balanced by deubiquitinases that cleave polyubiquitin chains and oppose the function of E3 ubiquitin ligases. Deubiquitinases therefore play an important role in the termination of NF-κB signaling and the resolution of inflammation. In this review, we focus on NF-κB regulation by deubiquitinases with an emphasis on A20 and CYLD. Deubiquitinases and the ubiquitin/proteasome components that regulate NF-κB may serve as novel therapeutic targets for inflammatory diseases and cancer.
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Affiliation(s)
- Edward W Harhaj
- Department of Microbiology and Immunology, Sylvester Comprehensive Cancer Center, The University of Miami, Miller School of Medicine, Miami, FL, USA
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432
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Abstract
A role for polyubiquitination in the activation of inhibitor of NF-κB (IκB) kinase (IKK) through a proteasome-independent mechanism was first reported in 1996, but the physiological significance of this finding was not clear until 2000 when TRAF6 was found to be a ubiquitin E3 ligase that catalyzes lysine-63 (K63) polyubiquitination. Since then, several proteins known to regulate IKK have been linked to the ubiquitin pathway. These include the deubiquitination enzymes CYLD and A20 that inhibit IKK, and the ubiquitin binding proteins NEMO and TAB2 which are the regulatory subunits of IKK and TAK1 kinase complexes, respectively. Now accumulating evidence strongly supports a central role of K63 polyubiquitination in IKK activation by multiple immune and inflammatory pathways. Interestingly, recent research suggests that some alternative ubiquitin chains such as linear or K11 ubiquitin chains may also play a role in certain pathways such as the TNF pathway. Here I present a historical narrative of the discovery of the role of ubiquitin in IKK activation, review recent advances in understanding the role and mechanism of ubiquitin-mediated IKK activation, and raise some questions to be resolved in future research.
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Affiliation(s)
- Zhijian J Chen
- Department of Molecular Biology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA.
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433
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McCool KW, Miyamoto S. DNA damage-dependent NF-κB activation: NEMO turns nuclear signaling inside out. Immunol Rev 2012; 246:311-26. [PMID: 22435563 DOI: 10.1111/j.1600-065x.2012.01101.x] [Citation(s) in RCA: 182] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The dimeric transcription factor nuclear factor κB (NF-κB) functions broadly in coordinating cellular responses during inflammation and immune reactions, and its importance in the pathogenesis of cancer is increasingly recognized. Many of the signal transduction pathways that trigger activation of cytoplasmic NF-κB in response to a broad array of immune and inflammatory stimuli have been elaborated in great detail. NF-κB can also be activated by DNA damage, though relatively less is known about the signal transduction mechanisms that link DNA damage in the nucleus with activation of NF-κB in the cytoplasm. Here, we focus on the conserved signaling pathway that has emerged that promotes NF-κB activation following DNA damage. Post-translational modification of NF-κB essential modulator (NEMO) plays a central role in linking the cellular DNA damage response to NF-κB via the ataxia telangiectasia mutated (ATM) kinase. Accumulating evidence suggests that DNA damage-dependent NF-κB activation may play significant biological roles, particularly during lymphocyte differentiation and progression of human malignancies.
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Affiliation(s)
- Kevin W McCool
- Medical Scientist Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA
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434
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Tokunaga F, Iwai K. LUBAC, a novel ubiquitin ligase for linear ubiquitination, is crucial for inflammation and immune responses. Microbes Infect 2012; 14:563-72. [DOI: 10.1016/j.micinf.2012.01.011] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 01/19/2012] [Indexed: 10/14/2022]
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435
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Stieglitz B, Rittinger K, Haire LF. Crystallization of SHARPIN using an automated two-dimensional grid screen for optimization. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:816-9. [PMID: 22750873 PMCID: PMC3388930 DOI: 10.1107/s1744309112022208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 05/16/2012] [Indexed: 12/05/2022]
Abstract
An N-terminal fragment of human SHARPIN was recombinantly expressed in Escherichia coli, purified and crystallized. Crystals suitable for X-ray diffraction were obtained by a one-step optimization of seed dilution and protein concentration using a two-dimensional grid screen. The crystals belonged to the primitive tetragonal space group P4(3)2(1)2, with unit-cell parameters a = b = 61.55, c = 222.81 Å. Complete data sets were collected from native and selenomethionine-substituted protein crystals at 100 K to 2.6 and 2.0 Å resolution, respectively.
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Affiliation(s)
- Benjamin Stieglitz
- Division of Molecular Structure, MRC – National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, England
| | - Katrin Rittinger
- Division of Molecular Structure, MRC – National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, England
| | - Lesley F. Haire
- Division of Molecular Structure, MRC – National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, England
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436
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Iwai K. Diverse ubiquitin signaling in NF-κB activation. Trends Cell Biol 2012; 22:355-64. [DOI: 10.1016/j.tcb.2012.04.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 04/01/2012] [Accepted: 04/03/2012] [Indexed: 10/28/2022]
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437
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Fulda S, Rajalingam K, Dikic I. Ubiquitylation in immune disorders and cancer: from molecular mechanisms to therapeutic implications. EMBO Mol Med 2012; 4:545-56. [PMID: 22730341 PMCID: PMC3407942 DOI: 10.1002/emmm.201100707] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 04/30/2012] [Accepted: 05/11/2012] [Indexed: 01/01/2023] Open
Abstract
Conjugation of ubiquitin to proteins (ubiquitylation) has emerged to be one of the most crucial post-translational modifications controlling virtually all cellular processes. What was once regarded as a mere signal for protein degradation has turned out to be a major regulator of molecular signalling networks. Deregulation of ubiquitin signalling is closely associated with various human pathologies. Here, we summarize the current knowledge of ubiquitin signalling in immune deficiencies and cancer as well as the available therapeutic strategies targeting the ubiquitin system in combating these pathogenic conditions.
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Affiliation(s)
- Simone Fulda
- Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany
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438
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Stieglitz B, Haire LF, Dikic I, Rittinger K. Structural analysis of SHARPIN, a subunit of a large multi-protein E3 ubiquitin ligase, reveals a novel dimerization function for the pleckstrin homology superfold. J Biol Chem 2012; 287:20823-9. [PMID: 22549881 PMCID: PMC3375506 DOI: 10.1074/jbc.m112.359547] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 04/17/2012] [Indexed: 11/06/2022] Open
Abstract
SHARPIN (SHANK-associated RH domain interacting protein) is part of a large multi-protein E3 ubiquitin ligase complex called LUBAC (linear ubiquitin chain assembly complex), which catalyzes the formation of linear ubiquitin chains and regulates immune and apoptopic signaling pathways. The C-terminal half of SHARPIN contains ubiquitin-like domain and Npl4-zinc finger domains that mediate the interaction with the LUBAC subunit HOIP and ubiquitin, respectively. In contrast, the N-terminal region does not show any homology with known protein interaction domains but has been suggested to be responsible for self-association of SHARPIN, presumably via a coiled-coil region. We have determined the crystal structure of the N-terminal portion of SHARPIN, which adopts the highly conserved pleckstrin homology superfold that is often used as a scaffold to create protein interaction modules. We show that in SHARPIN, this domain does not appear to be used as a ligand recognition domain because it lacks many of the surface properties that are present in other pleckstrin homology fold-based interaction modules. Instead, it acts as a dimerization module extending the functional applications of this superfold.
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Affiliation(s)
- Benjamin Stieglitz
- From the Division of Molecular Structure, Medical Research Council National Institute for Medical Research, The Ridgeway, London NW7 1AA, United Kingdom and
| | - Lesley F. Haire
- From the Division of Molecular Structure, Medical Research Council National Institute for Medical Research, The Ridgeway, London NW7 1AA, United Kingdom and
| | - Ivan Dikic
- the Buchmann Institute for Molecular Life Sciences and Institute of Biochemistry II, Goethe University School of Medicine, D-60590 Frankfurt, Germany
| | - Katrin Rittinger
- From the Division of Molecular Structure, Medical Research Council National Institute for Medical Research, The Ridgeway, London NW7 1AA, United Kingdom and
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439
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Asquith M, Haberthur K, Brown M, Engelmann F, Murphy A, Al-Mahdi Z, Messaoudi I. Age-dependent changes in innate immune phenotype and function in rhesus macaques (Macaca mulatta). PATHOBIOLOGY OF AGING & AGE RELATED DISEASES 2012; 2:PBA-2-18052. [PMID: 22953039 PMCID: PMC3417700 DOI: 10.3402/pba.v2i0.18052] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 03/17/2012] [Accepted: 03/17/2012] [Indexed: 12/25/2022]
Abstract
Aged individuals are more susceptible to infections due to a general decline in immune function broadly referred to as immune senescence. While age-related changes in the adaptive immune system are well documented, aging of the innate immune system remains less well understood, particularly in nonhuman primates. A more robust understanding of age-related changes in innate immune function would provide mechanistic insight into the increased susceptibility of the elderly to infection. Rhesus macaques have proved a critical translational model for aging research, and present a unique opportunity to dissect age-dependent modulation of the innate immune system. We examined age-related changes in: (i) innate immune cell frequencies; (ii) expression of pattern recognition receptors (PRRs) and innate signaling molecules; (iii) cytokine responses of monocytes and dendritic cells (DC) following stimulation with PRR agonists; and (iv) plasma cytokine levels in this model. We found marked changes in both the phenotype and function of innate immune cells. This included an age-associated increased frequency of myeloid DC (mDC). Moreover, we found toll-like receptor (TLR) agonists lipopolysaccharide (TLR4), fibroblast stimulating ligand-1 (TLR2/6), and ODN2006 (TLR7/9) induced reduced cytokine responses in aged mDC. Interestingly, with the exception of the monocyte-derived TNFα response to LPS, which increased with age, TNFα, IL-6, and IFNα responses declined with age. We also found that TLR4, TLR5, and innate negative regulator, sterile alpha and TIR motif containing protein (SARM), were all expressed at lower levels in young animals. By contrast, absent in melanoma 2 and retinoic acid-inducible gene I expression was lowest in aged animals. Together, these observations indicate that several parameters of innate immunity are significantly modulated by age and contribute to differential immune function in aged macaques.
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Affiliation(s)
- Mark Asquith
- Vaccine and Gene Therapy Institute, Oregon Health and Science University, Portland, OR, USA
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440
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Kensche T, Tokunaga F, Ikeda F, Goto E, Iwai K, Dikic I. Analysis of nuclear factor-κB (NF-κB) essential modulator (NEMO) binding to linear and lysine-linked ubiquitin chains and its role in the activation of NF-κB. J Biol Chem 2012; 287:23626-34. [PMID: 22605335 DOI: 10.1074/jbc.m112.347195] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Nuclear factor-κB (NF-κB) essential modulator (NEMO), a component of the inhibitor of κB kinase (IKK) complex, controls NF-κB signaling by binding to ubiquitin chains. Structural studies of NEMO provided a rationale for the specific binding between the UBAN (ubiquitin binding in ABIN and NEMO) domain of NEMO and linear (Met-1-linked) di-ubiquitin chains. Full-length NEMO can also interact with Lys-11-, Lys-48-, and Lys-63-linked ubiquitin chains of varying length in cells. Here, we show that purified full-length NEMO binds preferentially to linear ubiquitin chains in competition with lysine-linked ubiquitin chains of defined length, including long Lys-63-linked deca-ubiquitins. Linear di-ubiquitins were sufficient to activate both the IKK complex in vitro and to trigger maximal NF-κB activation in cells. In TNFα-stimulated cells, NEMO chimeras engineered to bind exclusively to Lys-63-linked ubiquitin chains mediated partial NF-κB activation compared with cells expressing NEMO that binds to linear ubiquitin chains. We propose that NEMO functions as a high affinity receptor for linear ubiquitin chains and a low affinity receptor for long lysine-linked ubiquitin chains. This phenomenon could explain quantitatively distinct NF-κB activation patterns in response to numerous cell stimuli.
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Affiliation(s)
- Tobias Kensche
- Buchmann Institute for Molecular Life Sciences and Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, D-60590 Frankfurt, Main, Germany
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441
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Damgaard RB, Nachbur U, Yabal M, Wong WWL, Fiil BK, Kastirr M, Rieser E, Rickard JA, Bankovacki A, Peschel C, Ruland J, Bekker-Jensen S, Mailand N, Kaufmann T, Strasser A, Walczak H, Silke J, Jost PJ, Gyrd-Hansen M. The ubiquitin ligase XIAP recruits LUBAC for NOD2 signaling in inflammation and innate immunity. Mol Cell 2012; 46:746-58. [PMID: 22607974 DOI: 10.1016/j.molcel.2012.04.014] [Citation(s) in RCA: 293] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 03/19/2012] [Accepted: 04/12/2012] [Indexed: 01/07/2023]
Abstract
Nucleotide-binding and oligomerization domain (NOD)-like receptors constitute a first line of defense against invading bacteria. X-linked Inhibitor of Apoptosis (XIAP) is implicated in the control of bacterial infections, and mutations in XIAP are causally linked to immunodeficiency in X-linked lymphoproliferative syndrome type-2 (XLP-2). Here, we demonstrate that the RING domain of XIAP is essential for NOD2 signaling and that XIAP contributes to exacerbation of inflammation-induced hepatitis in experimental mice. We find that XIAP ubiquitylates RIPK2 and recruits the linear ubiquitin chain assembly complex (LUBAC) to NOD2. We further show that LUBAC activity is required for efficient NF-κB activation and secretion of proinflammatory cytokines after NOD2 stimulation. Remarkably, XLP-2-derived XIAP variants have impaired ubiquitin ligase activity, fail to ubiquitylate RIPK2, and cannot facilitate NOD2 signaling. We conclude that XIAP and LUBAC constitute essential ubiquitin ligases in NOD2-mediated inflammatory signaling and propose that deregulation of NOD2 signaling contributes to XLP-2 pathogenesis.
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Affiliation(s)
- Rune Busk Damgaard
- Department of Disease Biology, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, 2200 Copenhagen, Denmark
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442
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Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein K13 activates NF-κB pathway independent of TRAF6, TAK1 and LUBAC. PLoS One 2012; 7:e36601. [PMID: 22590573 PMCID: PMC3348130 DOI: 10.1371/journal.pone.0036601] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 04/11/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein (vFLIP) K13 activates the NF-κB pathway by binding to the NEMO/IKKγ subunit of the IκB kinase (IKK) complex. However, it has remained enigmatic how K13-NEMO interaction results in the activation of the IKK complex. Recent studies have implicated TRAF6, TAK1 and linear ubiquitin chains assembled by a linear ubiquitin chain assembly complex (LUBAC) consisting of HOIL-1, HOIP and SHARPIN in IKK activation by proinflammatory cytokines. METHODOLOGY/PRINCIPAL FINDINGS Here we demonstrate that K13-induced NF-κB DNA binding and transcriptional activities are not impaired in cells derived from mice with targeted disruption of TRAF6, TAK1 and HOIL-1 genes and in cells derived from mice with chronic proliferative dermatitis (cpdm), which have mutation in the Sharpin gene (Sharpin(cpdm/cpdm)). Furthermore, reconstitution of NEMO-deficient murine embryonic fibroblast cells with NEMO mutants that are incapable of binding to linear ubiquitin chains supported K13-induced NF-κB activity. K13-induced NF-κB activity was not blocked by CYLD, a deubiquitylating enzyme that can cleave linear and Lys63-linked ubiquitin chains. On the other hand, NEMO was required for interaction of K13 with IKK1/IKKα and IKK2/IKKβ, which resulted in their activation by "T Loop" phosphorylation. CONCLUSIONS/SIGNIFICANCE Our results demonstrate that K13 activates the NF-κB pathway by binding to NEMO which results in the recruitment of IKK1/IKKα and IKK2/IKKβ and their subsequent activation by phosphorylation. Thus, K13 activates NF-κB via a mechanism distinct from that utilized by inflammatory cytokines. These results have important implications for the development of therapeutic agents targeting K13-induced NF-κB for the treatment of KSHV-associated malignancies.
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443
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Keusekotten K, Komander D. New Tools for Ubiquitin Signaling. J Mol Biol 2012; 418:129-30. [DOI: 10.1016/j.jmb.2012.02.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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444
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Yagi H, Ishimoto K, Hiromoto T, Fujita H, Mizushima T, Uekusa Y, Yagi-Utsumi M, Kurimoto E, Noda M, Uchiyama S, Tokunaga F, Iwai K, Kato K. A non-canonical UBA-UBL interaction forms the linear-ubiquitin-chain assembly complex. EMBO Rep 2012; 13:462-8. [PMID: 22430200 DOI: 10.1038/embor.2012.24] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 01/29/2012] [Accepted: 02/10/2012] [Indexed: 12/25/2022] Open
Abstract
HOIL-1L and its binding partner HOIP are essential components of the E3-ligase complex that generates linear ubiquitin (Ub) chains, which are critical regulators of NF-κB activation. Using crystallographic and mutational approaches, we characterize the unexpected structural basis for the specific interaction between the Ub-like domain (UBL) of HOIL-1L and the Ub-associated domain (UBA) of HOIP. Our data indicate the functional significance of this non-canonical mode of UBA-UBL interaction in E3 complex formation and subsequent NF-κB activation. This study highlights the versatility and specificity of protein-protein interactions involving Ub/UBLs and their cognate proteins.
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Affiliation(s)
- Hirokazu Yagi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
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445
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Shoji I. Roles of the two distinct proteasome pathways in hepatitis C virus infection. World J Virol 2012; 1:44-50. [PMID: 24175210 PMCID: PMC3782266 DOI: 10.5501/wjv.v1.i2.44] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 02/22/2012] [Accepted: 03/05/2012] [Indexed: 02/05/2023] Open
Abstract
Hepatitis C virus (HCV) infection often causes chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The development of a HCV cell culture system enabled us to investigate its whole HCV life cycle and develop a better understanding of the pathogenesis of this virus. Post-translational modification plays a crucial role in HCV replication and in the maturation of viral particles. There is growing evidence also suggesting that the ubiquitin-proteasome pathway and the ubiquitin-independent proteasome pathway are involved in the stability control of HCV proteins. Many viruses are known to manipulate the proteasome pathways to modulate the cell cycle, inhibit apoptosis, evade the immune system, and activate cell signaling, thereby contributing to persistent infection and viral carcinogenesis. The identification of functional interactions between HCV and the proteasome pathways will therefore shed new light on the life cycle and pathogenesis of HCV. This review summarizes the current knowledge on the involvement of the ubiquitin-dependent and -independent proteasome pathways in HCV infection and discusses the roles of these two distinct mechanisms in HCV pathogenesis.
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Affiliation(s)
- Ikuo Shoji
- Ikuo Shoji, Division of Microbiology, Kobe University Graduate School of Medicine, Hyogo 650-0017, Japan
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446
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Abstract
The posttranslational modification with ubiquitin, a process referred to as ubiquitylation, controls almost every process in cells. Ubiquitin can be attached to substrate proteins as a single moiety or in the form of polymeric chains in which successive ubiquitin molecules are connected through specific isopeptide bonds. Reminiscent of a code, the various ubiquitin modifications adopt distinct conformations and lead to different outcomes in cells. Here, we discuss the structure, assembly, and function of this ubiquitin code.
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Affiliation(s)
- David Komander
- Division of Protein and Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Cambridge, CB2 0QH, United Kingdom.
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447
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Husnjak K, Dikic I. Ubiquitin-binding proteins: decoders of ubiquitin-mediated cellular functions. Annu Rev Biochem 2012; 81:291-322. [PMID: 22482907 DOI: 10.1146/annurev-biochem-051810-094654] [Citation(s) in RCA: 569] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ubiquitin acts as a versatile cellular signal that controls a wide range of biological processes including protein degradation, DNA repair, endocytosis, autophagy, transcription, immunity, and inflammation. The specificity of ubiquitin signaling is achieved by alternative conjugation signals (monoubiquitin and ubiquitin chains) and interactions with ubiquitin-binding proteins (known as ubiquitin receptors) that decode ubiquitinated target signals into biochemical cascades in the cell. Herein, we review the current knowledge pertaining to the structural and functional features of ubiquitin-binding proteins and the mechanisms by which they recognize various types of ubiquitin topologies. The combinatorial use of diverse ubiquitin-binding domains (UBDs) in full-length proteins, selective recognition of chains with distinct linkages and length, and posttranslational modifications of ubiquitin receptors or multivalent interactions within protein complexes illustrate a few mechanisms by which a circuitry of signaling networks can be rewired by ubiquitin-binding proteins to control cellular functions in vivo.
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Affiliation(s)
- Koraljka Husnjak
- Institute of Biochemistry II, School of Medicine, Goethe University, 60590 Frankfurt am Main, Germany.
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448
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Wenzel DM, Klevit RE. Following Ariadne's thread: a new perspective on RBR ubiquitin ligases. BMC Biol 2012; 10:24. [PMID: 22420831 PMCID: PMC3305615 DOI: 10.1186/1741-7007-10-24] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/15/2012] [Indexed: 01/06/2023] Open
Abstract
Ubiquitin signaling pathways rely on E3 ligases for effecting the final transfer of ubiquitin from E2 ubiquitin conjugating enzymes to a protein target. Here we re-evaluate the hybrid RING/HECT mechanism used by the E3 family RING-between-RINGs (RBRs) to transfer ubiquitin to substrates. We place RBRs into the context of current knowledge of HECT and RING E3s. Although not as abundant as the other types of E3s (there are only slightly more than a dozen RBR E3s in the human genome), RBRs are conserved in all eukaryotes and play important roles in biology. Re-evaluation of RBR ligases as RING/HECT E3s provokes new questions and challenges the field.
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Affiliation(s)
- Dawn M Wenzel
- Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
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449
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Walczak H, Iwai K, Dikic I. Generation and physiological roles of linear ubiquitin chains. BMC Biol 2012; 10:23. [PMID: 22420778 PMCID: PMC3305636 DOI: 10.1186/1741-7007-10-23] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 03/15/2012] [Indexed: 12/11/2022] Open
Abstract
Ubiquitination now ranks with phosphorylation as one of the best-studied post-translational modifications of proteins with broad regulatory roles across all of biology. Ubiquitination usually involves the addition of ubiquitin chains to target protein molecules, and these may be of eight different types, seven of which involve the linkage of one of the seven internal lysine (K) residues in one ubiquitin molecule to the carboxy-terminal diglycine of the next. In the eighth, the so-called linear ubiquitin chains, the linkage is between the amino-terminal amino group of methionine on a ubiquitin that is conjugated with a target protein and the carboxy-terminal carboxy group of the incoming ubiquitin. Physiological roles are well established for K48-linked chains, which are essential for signaling proteasomal degradation of proteins, and for K63-linked chains, which play a part in recruitment of DNA repair enzymes, cell signaling and endocytosis. We focus here on linear ubiquitin chains, how they are assembled, and how three different avenues of research have indicated physiological roles for linear ubiquitination in innate and adaptive immunity and suppression of inflammation.
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Affiliation(s)
- Henning Walczak
- Tumour Immunology Unit, Department of Medicine, Imperial College London, 10N5 Commonwealth Building, Du Cane Road, London W12 0NN, UK.
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450
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Hayden MS, Ghosh S. NF-κB, the first quarter-century: remarkable progress and outstanding questions. Genes Dev 2012; 26:203-34. [PMID: 22302935 DOI: 10.1101/gad.183434.111] [Citation(s) in RCA: 1272] [Impact Index Per Article: 106.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ability to sense and adjust to the environment is crucial to life. For multicellular organisms, the ability to respond to external changes is essential not only for survival but also for normal development and physiology. Although signaling events can directly modify cellular function, typically signaling acts to alter transcriptional responses to generate both transient and sustained changes. Rapid, but transient, changes in gene expression are mediated by inducible transcription factors such as NF-κB. For the past 25 years, NF-κB has served as a paradigm for inducible transcription factors and has provided numerous insights into how signaling events influence gene expression and physiology. Since its discovery as a regulator of expression of the κ light chain gene in B cells, research on NF-κB continues to yield new insights into fundamental cellular processes. Advances in understanding the mechanisms that regulate NF-κB have been accompanied by progress in elucidating the biological significance of this transcription factor in various physiological processes. NF-κB likely plays the most prominent role in the development and function of the immune system and, not surprisingly, when dysregulated, contributes to the pathophysiology of inflammatory disease. As our appreciation of the fundamental role of inflammation in disease pathogenesis has increased, so too has the importance of NF-κB as a key regulatory molecule gained progressively greater significance. However, despite the tremendous progress that has been made in understanding the regulation of NF-κB, there is much that remains to be understood. In this review, we highlight both the progress that has been made and the fundamental questions that remain unanswered after 25 years of study.
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Affiliation(s)
- Matthew S Hayden
- Department of Microbiology and Immunology, College of Physicians and Surgeons, New York, New York 10032, USA
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