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Hong S, Wang LC, Gao X, Kuo YL, Liu B, Merling R, Kung HJ, Shih HM, Giam CZ. Heptad repeats regulate protein phosphatase 2a recruitment to I-kappaB kinase gamma/NF-kappaB essential modulator and are targeted by human T-lymphotropic virus type 1 tax. J Biol Chem 2007; 282:12119-26. [PMID: 17314097 DOI: 10.1074/jbc.m610392200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The switching on-and-off of I-kappaB kinase (IKK) and NF-kappaB occurs rapidly after signaling. How activated IKK becomes down-regulated is not well understood. Here we show that following tumor necrosis factor-alpha stimulation, protein phosphatase 2A (PP2A) association with IKK is increased. A heptad repeat in IKKgamma, helix 2 (HLX2), mediates PP2A recruitment. Two other heptad repeats downstream of HLX2, termed coiled-coil region 2 (CCR2) and leucine zipper (LZ), bind HLX2 and negatively regulate HLX2 interaction with PP2A. HTLV-1 transactivator Tax also binds HLX2, and this interaction is enhanced by CCR2 but reduced by LZ. In the presence of Tax, PP2A-IKKgamma binding is greatly strengthened. Interestingly, peptides spanning CCR2 and/or LZ disrupt IKKgamma-Tax and IKKgamma-PP2A interactions and potently inhibit NF-kappaB activation by Tax and tumor necrosis factor-alpha. We propose that when IKK is resting, HLX2, CCR2, and LZ form a helical bundle in which HLX2 is sequestered. The HLX2-CCR2-LZ bundle becomes unfolded by signal-induced modifications of IKKgamma or after Tax binding. In this conformation, IKK becomes activated. IKKgamma then recruits PP2A via the exposed HLX2 domain for rapid down-regulation of IKK. Tax-PP2A interaction, however, renders PP2A inactive, thus maintaining Tax-PP2A-IKK in an active state. Finally, CCR2 and LZ possibly inhibit IKK activation by stabilizing the HLX2-CCR2-LZ bundle.
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Affiliation(s)
- Sohee Hong
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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102
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Sehnert B, Gierer P, Ibrahim S, Kühl A, Voll R, Nandakumar KS, Holmdahl R, Hallmann R, Vollmar B, Burkhardt H. Modulation of granulocyte-endothelium interactions by antileukoproteinase: inhibition of anti-type II collagen antibody-induced leukocyte attachment to the synovial endothelium. Arthritis Res Ther 2007; 8:R95. [PMID: 16776851 PMCID: PMC1779410 DOI: 10.1186/ar1973] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 04/17/2006] [Accepted: 05/16/2006] [Indexed: 01/30/2023] Open
Abstract
Antileukoproteinase (ALP) is a physiological inhibitor of granulocytic serine proteases that has been shown to have anti-inflammatory properties in addition to its antiproteolytic activity. On the basis of its potential to block anti-collagen type II (CII) antibody-induced arthritis (CAIA) and to suppress the conformational activation of β2-integrins in leukocytes, the present study was undertaken to investigate its interference with leukocyte adherence to cytokine-activated endothelium. The potential of recombinant ALP to block the interactions of leukocytes with the endothelial lining was concomitantly investigated in vitro and in vivo. Thus, intravital fluorescence microscopic imaging of leukocyte rolling and firm adhesion to postcapillary venules were performed in the knee joints of DBA1/J mice after intravenous injection of anti-CII mAbs. An IL-1β-activated endothelial layer formed by a murine glomerular cell line (glEND.2) was used to assay the interaction with human leukocytes in vitro. Electromobility shift and luciferase reporter gene assays permitted the analysis of cytokine-induced activation of the NF-κB pathway. Fluorescence-activated cell sorting was applied to determine endothelial E-selectin expression. Leukocyte rolling and firm adhesion to the synovial endothelium in an early response to the anti-CII antibody transfer were significantly decreased in ALP-pretreated mice. Concomitantly, ALP suppressed the IL-1β-induced NF-κB activation and the upregulation of E-selectin expression in glEND.2 cells in vitro. These findings support the notion that the newly uncovered properties of ALP to interfere with cytokine signalling and upregulation of adhesion molecules in endothelial cells are likely to contribute to the therapeutic potential of ALP in immune-complex-induced tissue injury.
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Affiliation(s)
- Bettina Sehnert
- Department of Internal Medicine III and Institute of Clinical Immunology at the Friedrich-Alexander-University of Erlangen-Nürnberg, Krankenhausstrasse 12, 91054 Erlangen, Germany
| | - Philip Gierer
- Department of Experimental Surgery, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
- Department of Trauma and Reconstructive Surgery, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
| | - Saleh Ibrahim
- Institute of Immunology, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
| | - Anja Kühl
- Department of Experimental Surgery, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
| | - Reinhard Voll
- IZKF Research Group N2, Nikolaus-Fiebiger Center, and Department of Internal Medicine III, Friedrich-Alexander-University of Erlangen-Nürnberg, Glückstrasse 6, 91054 Erlangen, Germany
| | | | - Rikard Holmdahl
- Section for Medical Inflammation Research, BMC I11, Lund University, Sweden
| | - Rupert Hallmann
- Institute for Physiological Chemistry and Pathobiochemistry, University of Münster, Waldeyerstrasse 15, 48149 Münster, Germany
| | - Brigitte Vollmar
- Department of Experimental Surgery, University of Rostock, Schillingallee 70, 18055 Rostock, Germany
| | - Harald Burkhardt
- Department of Internal Medicine III and Institute of Clinical Immunology at the Friedrich-Alexander-University of Erlangen-Nürnberg, Krankenhausstrasse 12, 91054 Erlangen, Germany
- Current address: Division of Rheumatology, Johann Wolfgang Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
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103
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Solt LA, Madge LA, Orange JS, May MJ. Interleukin-1-induced NF-kappaB activation is NEMO-dependent but does not require IKKbeta. J Biol Chem 2007; 282:8724-33. [PMID: 17244613 PMCID: PMC2824644 DOI: 10.1074/jbc.m609613200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of NF-kappaB by the pro-inflammatory cytokines tumor necrosis factor (TNF) and interleukin-1 (IL-1) requires the IkappaB kinase (IKK) complex, which contains two kinases named IKKalpha and IKKbeta and a critical regulatory subunit named NEMO. Although we have previously demonstrated that NEMO associates with both IKKs, genetic studies reveal that only its interaction with IKKbeta is required for TNF-induced NF-kappaB activation. To determine whether NEMO and IKKalpha can form a functional IKK complex capable of activating the classical NF-kappaB pathway in the absence of IKKbeta, we utilized a panel of mouse embryonic fibroblasts (MEFs) lacking each of the IKK complex subunits. This confirmed that TNF-induced IkappaBalpha degradation absolutely requires NEMO and IKKbeta. In contrast, we consistently observed intact IkappaBalpha degradation and NF-kappaB activation in response to IL-1 in two separate cell lines lacking IKKbeta. Furthermore, exogenously expressed, catalytically inactive IKKbeta blocked TNF- but not IL-1-induced IkappaBalpha degradation in wild-type MEFs, and reconstitution of IKKalpha/beta double knockout cells with IKKalpha rescued IL-1- but not TNF-induced NF-kappaB activation. Finally, we have shown that incubation of IKKbeta-deficient MEFs with a cell-permeable peptide that blocks the interaction of NEMO with the IKKs inhibits IL-1-induced NF-kappaB activation. Our results therefore demonstrate that NEMO and IKKalpha can form a functional IKK complex that activates the classical NF-kappaB pathway in response to IL-1 but not TNF. These findings further suggest NEMO differentially regulates the fidelity of the IKK subunits activated by distinct upstream signaling pathways.
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Affiliation(s)
- Laura A. Solt
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104
| | - Lisa A. Madge
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104
| | - Jordan S. Orange
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Michael J. May
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104
- To whom correspondence should be addressed: Dept. of Animal Biology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St. (OVH 200E), Philadelphia, PA 19104. Tel.: 215-573-0940; Fax: 215-573-5186;
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104
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Abstract
Nuclear factor kappaB (NF-kappaB), a transcription factor, plays an important role in carcinogenesis as well as in the regulation of immune and inflammatory responses. NF-kappaB induces the expression of diverse target genes that promote cell proliferation, regulate apoptosis, facilitate angiogenesis and stimulate invasion and metastasis. Furthermore, many cancer cells show aberrant or constitutive NF-kappaB activation which mediates resistance to chemo- and radio-therapy. Therefore, the inhibition of NF-kappaB activation and its signaling pathway offers a potential cancer therapy strategy. In addition, recent studies have shown that NF-kappaB can also play a tumor suppressor role in certain settings. In this review, we focus on the role of NF-kappaB in carcinogenesis and the therapeutic potential of targeting NF-kappaB in cancer therapy.
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Affiliation(s)
- Chae Hyeong Lee
- Department of Obstetrics and Gynecology, College of Medicine, Seoul National University, Seoul, Korea
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105
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Abstract
Transcription factors of the NF-kappaB family regulate hundreds of genes in the context of multiple important physiological and pathological processes. NF-kappaB activation depends on phosphorylation-induced proteolysis of inhibitory IkappaB molecules and NF-kappaB precursors by the ubiquitin-proteasome system. Most of the diverse signaling pathways that activate NF-kappaB converge on IkappaB kinases (IKK), which are essential for signal transmission. Many important details of the composition, regulation and biological function of IKK have been revealed in the last years. This review summarizes current aspects of structure and function of the regular stoichiometric components, the regulatory transient protein interactions of IKK and the mechanisms that contribute to its activation, deactivation and homeostasis. Both phosphorylation and ubiquitinatin (destructive as well as non-destructive) are crucial post-translational events in these processes. In addition to controlling induced IkappaB degradation in the cytoplasm and processing of the NF-kappaB precursor p100, nuclear IKK components have been found to act directly at the chromatin level of induced genes and to mediate responses to DNA damage. Finally, IKK is engaged in cross talk with other pathways and confers functions independently of NF-kappaB.
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106
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Leis H, Sanchis A, Pérez P. Deletion of the N-terminus of IKKgamma induces apoptosis in keratinocytes and impairs the AKT/PTEN signaling pathway. Exp Cell Res 2006; 313:742-52. [PMID: 17184772 DOI: 10.1016/j.yexcr.2006.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 11/06/2006] [Accepted: 11/15/2006] [Indexed: 01/03/2023]
Abstract
The regulatory subunit IKKgamma/NEMO is crucial for skin development and function and although devoid of kinase activity, loss of IKKgamma function completely abolishes the activation of NF-kappaB by all pro-inflammatory cytokines. To inhibit the IkappaB kinase (IKK) complex in keratinocytes, we have used a dominant negative approach by generating stable transfectants of an N-terminal deletion of IKKgamma (IKKgamma-DN97) that uncouples formation of the IKK complex. Expression of this mutant in PB keratinocytes (PB-IKKgamma-DN97) delayed growth kinetics, caused morphological changes and dramatically augmented apoptosis even in the absence of pro-apoptotic stimuli, as determined by cell morphology, TUNEL and caspase-3 cleavage. Moreover, in PB-IKKgamma-DN97 cells, TNF-alpha and IL-1 treatment failed to induce degradation of IkappaBalpha, phosphorylation of p65 on Ser 536 and nuclear translocation which, consequently, reduced kappaB-binding activity. In PB-IKKgamma-DN97 cells, accumulation of IkappaBalpha correlated with a downregulation of AKT activity and an increase of PTEN protein levels whereas pro-apoptotic p53 target genes Bax and Puma were upregulated. These effects were most likely mediated through IKK since coexpression of the wild-type form of IKKgamma in keratinocytes partially reversed apoptosis and reduced PTEN expression. Thus, our data suggest a negative cross-talk mechanism involving PTEN and NF-kappaB, critical for the anti-apoptotic role of NF-kappaB in keratinocytes.
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Affiliation(s)
- Hugo Leis
- Centro de Investigación Príncipe Felipe, Valencia, Av. Autopista del Saler 16, Camino de las Moreras, Valencia, Spain
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107
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Abstract
Nuclear factor (NF)-kappaB is a ubiquitous and essential transcription factor whose dysregulation has been linked to numerous diseases including arthritis and cancer. It is therefore not surprising that the NF-kappaB activation pathway has become a major target for development of novel therapies for inflammatory diseases and cancer. However, the indispensable role played by NF-kappaB in many biological processes has raised concern that a complete shutdown of this pathway would have significant detrimental effects on normal cellular function. Instead, drugs that selectively target the inflammation induced NF-kappaB activity, while sparing the protective functions of basal NF-kappaB activity, would be of greater therapeutic value and would likely display fewer undesired side effects. The recent identification and characterisation of the NF-kappaB essential modulator (NEMO)-binding domain (NBD) peptide that can block the activation of the IkappaB kinase (IKK) complex, have provided an opportunity to selectively abrogate the inflammation induced activation of NF-kappaB by targeting the NBD-NEMO interaction. This peptide is synthesised in tandem with a protein transduction domain sequence from Drosophila antennapedia which facilitates uptake of the inhibitory peptide into the cytosol of target cells.
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Affiliation(s)
- I Strickland
- Section of Immunology, Department of Biophysics and Biochemistry, Yale University, New Haen, CT, USA
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108
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Abstract
Members of the nuclear factor kappa B (NF-kappaB) family of dimeric transcription factors (TFs) regulate expression of a large number of genes involved in immune responses, inflammation, cell survival, and cancer. NF-kappaB TFs are rapidly activated in response to various stimuli, including cytokines, infectious agents, and radiation-induced DNA double-strand breaks. In nonstimulated cells, some NF-kappaB TFs are bound to inhibitory IkappaB proteins and are thereby sequestered in the cytoplasm. Activation leads to phosphorylation of IkappaB proteins and their subsequent recognition by ubiquitinating enzymes. The resulting proteasomal degradation of IkappaB proteins liberates IkappaB-bound NF-kappaB TFs, which translocate to the nucleus to drive expression of target genes. Two protein kinases with a high degree of sequence similarity, IKKalpha and IKKbeta, mediate phosphorylation of IkappaB proteins and represent a convergence point for most signal transduction pathways leading to NF-kappaB activation. Most of the IKKalpha and IKKbeta molecules in the cell are part of IKK complexes that also contain a regulatory subunit called IKKgamma or NEMO. Despite extensive sequence similarity, IKKalpha and IKKbeta have largely distinct functions, due to their different substrate specificities and modes of regulation. IKKbeta (and IKKgamma) are essential for rapid NF-kappaB activation by proinflammatory signaling cascades, such as those triggered by tumor necrosis factor alpha (TNFalpha) or lipopolysaccharide (LPS). In contrast, IKKalpha functions in the activation of a specific form of NF-kappaB in response to a subset of TNF family members and may also serve to attenuate IKKbeta-driven NF-kappaB activation. Moreover, IKKalpha is involved in keratinocyte differentiation, but this function is independent of its kinase activity. Several years ago, two protein kinases, one called IKKepsilon or IKK-i and one variously named TBK1 (TANK-binding kinase), NAK (NF-kappaB-activated kinase), or T2K (TRAF2-associated kinase), were identified that exhibit structural similarity to IKKalpha and IKKbeta. These protein kinases are important for the activation of interferon response factor 3 (IRF3) and IRF7, TFs that play key roles in the induction of type I interferon (IFN-I). Together, the IKKs and IKK-related kinases are instrumental for activation of the host defense system. This Review focuses on the functions of IKK and IKK-related kinases and the molecular mechanisms that regulate their activities.
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Affiliation(s)
- Hans Häcker
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
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109
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Marienfeld RB, Palkowitsch L, Ghosh S. Dimerization of the I kappa B kinase-binding domain of NEMO is required for tumor necrosis factor alpha-induced NF-kappa B activity. Mol Cell Biol 2006; 26:9209-19. [PMID: 17000764 PMCID: PMC1698548 DOI: 10.1128/mcb.00478-06] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Previous studies have demonstrated that peptides corresponding to a six-amino-acid NEMO-binding domain from the C terminus of IkappaB kinase alpha (IKKalpha) and IKKbeta can disrupt the IKK complex and block NF-kappaB activation. We have now mapped and characterized the corresponding amino-terminal IKK-binding domain (IBD) of NEMO. Peptides corresponding to the IBD were efficiently recruited to the IKK complex but displayed only a weak inhibitory potential on cytokine-induced NF-kappaB activity. This is most likely due to the formation of sodium dodecyl sulfate- and urea-resistant NEMO dimers through a dimerization domain at the amino terminus of NEMO that overlaps with the region responsible for binding to IKKs. Mutational analysis revealed different alpha-helical subdomains within an amino-terminal coiled-coil region are important for NEMO dimerization and IKKbeta binding. Furthermore, NEMO dimerization is required for the tumor necrosis factor alpha-induced NF-kappaB activation, even when interaction with the IKKs is unaffected. Hence, our data provide novel insights into the role of the amino terminus of NEMO for the architecture of the IKK complex and its activation.
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Affiliation(s)
- Ralf B Marienfeld
- Section of Immunobiology and Department of Molecular Biophysics and Biochemistry, Yale University Medical School, New Haven, CT 06520, USA
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110
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Gloire G, Dejardin E, Piette J. Extending the nuclear roles of IkappaB kinase subunits. Biochem Pharmacol 2006; 72:1081-9. [PMID: 16846590 DOI: 10.1016/j.bcp.2006.06.017] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 06/02/2006] [Accepted: 06/13/2006] [Indexed: 01/04/2023]
Abstract
The transcription factor NF-kappaB plays a key role in a wide variety of cellular processes such as innate and adaptive immunity, cellular proliferation, apoptosis and development. In unstimulated cells, NF-kappaB is sequestered in the cytoplasm through its tight association with inhibitory proteins called IkappaBs, comprising notably IkappaBalpha. A key step in NF-kappaB activation is the phosphorylation of IkappaBalpha by the so-called IkappaB kinase (IKK) complex, which targets the inhibitory protein for proteasomal degradation and allows the freed NF-kappaB to enter the nucleus where it can transactivate its target genes. The IKK complex is composed of two catalytic subunits called IKKalpha and IKKbeta, and a regulatory subunit called NEMO/IKKgamma. Despite their key role in mediating IkappaBalpha phosphorylation in the cytoplasm, recent works have provided evidence that IKK subunits also translocate into the nucleus to regulate NF-kappaB-dependent and -independent gene expression, paving the way of a novel and exciting field of research. In this review, we will describe the current knowledge in that research area.
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Affiliation(s)
- Geoffrey Gloire
- Center for Biomedical Integrated Genoproteomics (CBIG), Virology and Immunology Unit, Institute of Pathology B23, B-4000 Liège, Belgium
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111
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Yang F, De La Fuente R, Leu NA, Baumann C, McLaughlin KJ, Wang PJ. Mouse SYCP2 is required for synaptonemal complex assembly and chromosomal synapsis during male meiosis. ACTA ACUST UNITED AC 2006; 173:497-507. [PMID: 16717126 PMCID: PMC2063860 DOI: 10.1083/jcb.200603063] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During meiosis, the arrangement of homologous chromosomes is tightly regulated by the synaptonemal complex (SC). Each SC consists of two axial/lateral elements (AEs/LEs), and numerous transverse filaments. SC protein 2 (SYCP2) and SYCP3 are integral components of AEs/LEs in mammals. We find that SYCP2 forms heterodimers with SYCP3 both in vitro and in vivo. An evolutionarily conserved coiled coil domain in SYCP2 is required for binding to SYCP3. We generated a mutant Sycp2 allele in mice that lacks the coiled coil domain. The fertility of homozygous Sycp2 mutant mice is sexually dimorphic; males are sterile because of a block in meiosis, whereas females are subfertile with sharply reduced litter size. Sycp2 mutant spermatocytes exhibit failure in the formation of AEs and chromosomal synapsis. Strikingly, the mutant SYCP2 protein localizes to axial chromosomal cores in both spermatocytes and fetal oocytes, but SYCP3 does not, demonstrating that SYCP2 is a primary determinant of AEs/LEs and, thus, is required for the incorporation of SYCP3 into SCs.
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Affiliation(s)
- Fang Yang
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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112
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Clohisy JC, Yamanaka Y, Faccio R, Abu-Amer Y. Inhibition of IKK activation, through sequestering NEMO, blocks PMMA-induced osteoclastogenesis and calvarial inflammatory osteolysis. J Orthop Res 2006; 24:1358-65. [PMID: 16705717 DOI: 10.1002/jor.20184] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Osteoclasts, the primary bone-resorbing cells, play a crucial role in periprosthetic bone loss in response to implant-derived wear debris. Differentiation and activation of osteoclasts at the implant-bone interface are fueled by elevated levels of locally secreted inflammatory cytokines that heighten the osteolytic response. Among these cytokines are members of the TNF superfamily, including TNF and RANKL, which primarily act through activation of the transcription factor NF-kappaB. Activation of NF-kappaB is required for osteoclast formation, and its inhibition hampers osteoclastogenesis and bone loss. Activation of NF-kappaB is permitted following its dissociation from the inhibitory protein IkappaBalpha, an event subsequent to phosphorylation of the latter protein by the upstream IkappaBalpha kinase (IKK) complex. Our recent findings show that attenuating IKK complex assembly, by using a short peptide termed NEMO-binding domain (NBD) peptide, that blocks binding of IKK2 and IKK1 to IKKgamma/NEMO, inhibits NF-kappaB activation, and arrests RANKL-induced osteoclastogenesis. In this study, we examined if NBD is capable of blocking inflammatory osteolysis by PMMA particles. Our findings indicate that NBD peptide inhibits PMMA-induced IKK2 and NF-kappaB activation. More importantly, this peptide potently arrests PMMA-stimulated osteoclastogenesis and alleviates PMMA-induced inflammatory and osteolytic responses in mice. Thus, NBD peptide is considered as a promising modality to regulate inflammatory osteolysis.
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Affiliation(s)
- John C Clohisy
- Department of Orthopaedics and Cell Biology & Physiology, Washington University School of Medicine, One Barnes Hospital Plaza, 11300 West Pavilion Campus, Box 8233, St. Louis, Missouri 63110, USA
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113
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Schomer-Miller B, Higashimoto T, Lee YK, Zandi E. Regulation of IκB Kinase (IKK) Complex by IKKγ-dependent Phosphorylation of the T-loop and C Terminus of IKKβ. J Biol Chem 2006; 281:15268-76. [PMID: 16597623 DOI: 10.1074/jbc.m513793200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanistic relationship of phosphorylation of the C terminus of IKKbeta with phosphorylation of its T-loop kinase domain within the IKK complex remained unclear. We investigated the regulatory role of the serine cluster residing immediately adjacent to the HLH domain and of the serines in the NEMO/IKKgamma-binding domain (NBD/gammaBD) in the C-terminal portion of IKKbeta in MEFs deficient in IKKbeta and IKKalpha and in yeast reconstitution system. We show that phosphorylation events at the C terminus of IKKbeta can be divided into autophosphorylation of the serine cluster adjacent to the HLH domain and phosphorylation of the NBD/gammaBD. Autophosphorylation of the serine cluster occurs immediately after IKK activation and requires IKKgamma. In MEFs, this autophosphorylation does not have the down-regulatory function on the IKK complex that was previously described (1). On the other hand, phosphorylation of the NBD/gammaBD regulates IKKgamma-dependent phosphorylation of the T-loop activation domain in IKKbeta and, hence, IKK complex activation. Our study suggests that, within the IKK complex, modulation of the NBD/gammaBD by IKKgamma is upstream to the T-loop phosphorylation.
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Affiliation(s)
- Beth Schomer-Miller
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California 90089-9176, USA
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114
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Strnad J, McDonnell PA, Riexinger DJ, Mapelli C, Cheng L, Gray H, Ryseck RP, Burke JR. NEMO binding domain of IKK-2 encompasses amino acids 735–745. J Mol Recognit 2006; 19:227-33. [PMID: 16583354 DOI: 10.1002/jmr.766] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
NF-kappaB activation is mediated by the IKK signalsome. Though this signalsome is comprised of IKK-1, IKK-2, and NEMO/IKKgamma, it is the interaction between IKK-2 and NEMO that is critical to formation of a functional signalsome. More specifically, previous reports have indicated that this interaction involves the C-terminal LDWSWL residues of IKK-2 (called the Nemo Binding Domain (NBD)) and the N-terminus of NEMO. In an effort to characterize the IKK-2:NEMO interaction, we have investigated several NBD-containing peptides for their ability to bind NEMO and inhibit the critical IKK-2:NEMO interaction. The six residue NBD peptide, LDWSWL, showed modest binding to NEMO and little inhibition of the IKK-2:NEMO interaction, whereas peptides containing the NBD plus additional flanking amino acids (NBD-containing peptides) more effectively bound NEMO and inhibited the interaction. These longer NBD-containing peptides may be required to give the NBD an appropriate conformation for recognition by NEMO and/or to provide for additional interactions with NEMO.
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Affiliation(s)
- Joann Strnad
- Drug Discovery Research, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543, USA.
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115
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Abu-Amer Y, Faccio R. Therapeutic approaches in bone pathogeneses: targeting the IKK/NF-κB axis. ACTA ACUST UNITED AC 2006. [DOI: 10.2217/17460816.1.1.133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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116
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Abstract
Bone metabolism is regulated by hormonal or local factors in the bone microenvironment, and recent studies have revealed that bone homeostasis is also influenced by immune system. The term 'osteoimmunology' has been proposed to explain the cross-talk between bone and the immune system. A critical element in this cross-talk is the inducible transcription factor nuclear factor-kappaB (NF-kappaB), which regulates gene expression during inflammatory and immune responses. However, NF-kappaB-signaling pathways are also important for bone homeostasis, in particular for osteoclast differentiation. By bridging inflammation and bone homeostasis, NF-kappaB also contributes to the onset and progression of arthritis. Several natural compounds, synthetic drugs, and gene-transfer technologies that lead to inhibition of the inhibitor of NF-kappaB kinase (IKK)/NF-kappaB activation pathway can prevent arthritis in animal models. In this review, we discuss the signaling pathway that leads to NF-kappaB activation and the role of NF-kappaB on osteoclast differentiation. Furthermore, we discuss the possibility that inhibition of NF-kappaB might provide novel therapeutic approach for inhibiting bone destruction in rheumatoid arthritis.
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Affiliation(s)
- Eijiro Jimi
- Division of Molecular Biochemistry, Department of Biosciences, Science of Health Improvement, Kyushu Dental College, Kitakyushu-shi, Japan
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117
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Lamsoul I, Lodewick J, Lebrun S, Brasseur R, Burny A, Gaynor RB, Bex F. Exclusive ubiquitination and sumoylation on overlapping lysine residues mediate NF-kappaB activation by the human T-cell leukemia virus tax oncoprotein. Mol Cell Biol 2005; 25:10391-406. [PMID: 16287853 PMCID: PMC1291224 DOI: 10.1128/mcb.25.23.10391-10406.2005] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The transcription factor NF-kappaB is critical for the induction of cancer, including adult T-cell leukemia, which is linked to infection by human T-cell leukemia virus type 1 and the expression of its regulatory protein Tax. Although activation of the NF-kappaB pathway by Tax involves its interaction with the regulatory subunit of the IkappaB kinase (IKK) complex, NEMO/IKKgamma, the mechanism by which Tax activates specific cellular genes in the nucleus remains unknown. Here, we demonstrate that the attachment of SUMO-1 to Tax regulates its localization in nuclear bodies and the recruitment of both the RelA subunit of NF-kappaB and free IKKgamma in these nuclear structures. However, this sumoylation step is not sufficient for the activation of the NF-kappaB pathway by Tax. This activity requires the prior ubiquitination and colocalization of ubiquitinated Tax with IKK complexes in the cytoplasm and the subsequent migration of the RelA subunit of NF-kappaB to the nucleus. Thus, the ubiquitination and sumoylation of Tax function in concert to result in the migration of RelA to the nucleus and its accumulation with IKKgamma in nuclear bodies for activation of gene expression. These modifications may result in targets for the treatment of adult T-cell leukemia.
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Affiliation(s)
- Isabelle Lamsoul
- Institute for Microbiological Research J-M Wiame, 1 Avenue E. Gryson, B-1070 Brussels, Belgium
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118
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Li Q, Withoff S, Verma IM. Inflammation-associated cancer: NF-kappaB is the lynchpin. Trends Immunol 2005; 26:318-25. [PMID: 15922948 DOI: 10.1016/j.it.2005.04.003] [Citation(s) in RCA: 226] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Revised: 03/18/2005] [Accepted: 04/14/2005] [Indexed: 01/19/2023]
Abstract
It has long been suspected that NF-kappaB signaling has a pivotal role in chronic inflammation-associated malignancies, although genetic evidence for this hypothesis has been lacking. However, recent papers have lent credence to this concept and show that NF-kappaB activation in pre-malignant cells contributes to cell survival and metastatic potential. Furthermore, NF-kappaB activation in tumor-associated leukocytes, especially macrophages, contributes towards tumorigenesis by upregulating tumor-promoting proinflammatory proteins. This emphasizes the importance of NF-kappaB inhibitors as immunotherapeutic agents for chronic inflammation and suggests that these reagents might prevent, or at least inhibit, chronic inflammation-associated tumorigenesis.
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Affiliation(s)
- Qiutang Li
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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119
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Nadjar A, Tridon V, May MJ, Ghosh S, Dantzer R, Amédée T, Parnet P. NFkappaB activates in vivo the synthesis of inducible Cox-2 in the brain. J Cereb Blood Flow Metab 2005; 25:1047-59. [PMID: 15758944 DOI: 10.1038/sj.jcbfm.9600106] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Interleukin-1beta (IL-1beta) induces cyclooxygenase-2 (Cox-2) expression in many of its cellular targets resulting in production and release of prostaglandins. Although IL-1beta-induced Cox-2 expression most likely requires activation of nuclear transcription factor kappa B (NFkappaB) pathway, this has never been formally demonstrated in vivo. We tested this using a specific inhibitor of NFkappaB activation, the NEMO binding domain (NBD) peptide, that has been shown previously to be effective in various in vivo models of acute inflammation. Incubation of rat glioma cells with the NBD peptide blocked IL-1beta-induced NFkappaB nuclear translocation. Furthermore, after injection of a biotinylated version of the NBD peptide into the lateral ventricle of the brain, we found that it readily diffused to its potential cellular targets in vivo. To test the effects of the peptide on NFkappaB activation and Cox-2 expression in the brain, we injected it intracerebroventricularly (36 microg/rat) into rats before intraperitoneal injection of IL-1beta (60 microg/kg). Treatment with NBD peptide completely abolished IL-1beta-induced NFkappaB activation and Cox-2 synthesis in microvasculature. In contrast, the peptide had no effect on constitutive neuronal Cox-2. These findings strongly support the hypothesis that IL-1beta-induced NFkappaB activation plays a major role in transmission of immune signals from the periphery to the brain.
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Affiliation(s)
- Agnès Nadjar
- Institut F. Magendie, Unité de Neurobiologie Intégrative, Bordeaux Cedex, France
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120
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di Meglio P, Ianaro A, Ghosh S. Amelioration of acute inflammation by systemic administration of a cell-permeable peptide inhibitor of NF-kappaB activation. ACTA ACUST UNITED AC 2005; 52:951-8. [PMID: 15751079 DOI: 10.1002/art.20960] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE We used an experimental model of inflammation in mice, carrageenan-induced paw edema, to study the antiinflammatory effects of the NEMO-binding domain (NBD) peptide, which blocks activation of the inducible transcription factor NF-kappaB. METHODS Paw edema was induced by subplantar injection of 1% lambda-carrageenan into the mouse left hind paw. Test agents were given intraperitoneally immediately after carrageenan injection. The increase in footpad thickness was considered to be edema. In some experiments, the mice were killed and the paws were removed for histologic and molecular biology analysis. NF-kappaB DNA binding activity was evaluated in nuclear extracts by electrophoretic mobility shift assays. The expression levels of NF-kappaB-regulated cyclooxygenase 2 (COX-2) protein and tumor necrosis factor alpha (TNFalpha) messenger RNA (mRNA) were evaluated by immunoblot analysis and polymerase chain reaction amplification of reverse-transcribed mRNA, respectively. RESULTS We found that systemically administered NBD peptide significantly inhibited edema formation and cellular infiltration in inflamed mouse paws. This antiinflammatory activity was most likely due to inhibition of expression of proinflammatory mediators, such as TNFalpha and COX-2, in inflamed tissues. CONCLUSION These studies further establish NF-kappaB as a target for antiinflammatory therapy and provide support for the use of the NBD peptide as a possible therapeutic agent for inflammatory diseases.
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Affiliation(s)
- Paola di Meglio
- Yale University School of Medicine, New Haven, Connecticut 06520, USA
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121
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Noda K, Kitami T, Gai WP, Chegini F, Jensen PH, Fujimura T, Murayama K, Tanaka K, Mizuno Y, Hattori N. Phosphorylated IκBα is a component of Lewy body of Parkinson’s disease. Biochem Biophys Res Commun 2005; 331:309-17. [PMID: 15845394 DOI: 10.1016/j.bbrc.2005.03.167] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2005] [Indexed: 01/13/2023]
Abstract
Ubiquitin is one of the major components of Lewy bodies (LB), the pathological hallmark of Parkinson's disease (PD). Here, we identified that a phosphorylated form of IkappaBalpha (pIkappaBalpha), an inhibitor of NF-kappaB, and SCF(beta-TrCP), the ubiquitin ligase of pIkappaBalpha, are components of LB in brains of PD patients. In vitro studies identified those proteins in the ubiquitin- and alpha-synuclein (known as the major component of LB)-positive LB-like inclusions generated in dopaminergic SH-SY5Y cells treated with MG132, a proteasome inhibitor. Intriguingly, IkappaBalpha migration into such ubiquitinated inclusions in cells treated with MG132 was inhibited by a cell-permeable peptide known to block phosphorylation of IkappaBalpha, although this peptide did not influence cell viability under proteasomal inhibition. Our results indicate that phosphorylation of IkappaBalpha plays a role in the formation of IkappaBalpha-containing inclusions caused by proteasomal dysfunction, and that the generation of such inclusion is independent of cell death caused by impairment of proteasome.
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Affiliation(s)
- Kazuyuki Noda
- Department of Neurology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan
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122
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Agou F, Courtois G, Chiaravalli J, Baleux F, Coïc YM, Traincard F, Israël A, Véron M. Inhibition of NF-κB Activation by Peptides Targeting NF-κB Essential Modulator (NEMO) Oligomerization. J Biol Chem 2004; 279:54248-57. [PMID: 15466857 DOI: 10.1074/jbc.m406423200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
NF-kappa B essential modulator/IKK-gamma (NEMO/IKK-gamma) plays a key role in the activation of the NF-kappa B pathway in response to proinflammatory stimuli. Previous studies suggested that the signal-dependent activation of the IKK complex involves the trimerization of NEMO. The minimal oligomerization domain of this protein consists of two coiled-coil subdomains named Coiled-coil 2 (CC2) and leucine zipper (LZ) (Agou, F., Traincard, F., Vinolo, E., Courtois, G., Yamaoka, S., Israel, A., and Veron, M. (2004) J. Biol. Chem. 279, 27861-27869). To search for drugs inhibiting NF-kappa B activation, we have rationally designed cell-permeable peptides corresponding to the CC2 and LZ subdomains that mimic the contact areas between NEMO subunits. The peptides were tagged with the Antennapedia/Penetratin motif and delivered to cells prior to stimulation with lipopolysaccharide. Peptide transduction was monitored by fluorescence-activated cell sorter, and their effect on lipopolysaccharide-induced NF-kappa B activation was quantified using an NF-kappa B-dependent beta-galactosidase assay in stably transfected pre-B 70Z/3 lymphocytes. We show that the peptides corresponding to the LZ and CC2 subdomains inhibit NF-kappa B activation with an IC(50) in the mum range. Control peptides, including mutated CC2 and LZ peptides and a heterologous coiled-coil peptide, had no inhibitory effect. The designed peptides are able to induce cell death in human retinoblastoma Y79 cells exhibiting constitutive NF-kappa B activity. Our results provide the "proof of concept" for a new and promising strategy for the inhibition of NF-kappa B pathway activation through targeting the oligomerization state of the NEMO protein.
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Affiliation(s)
- Fabrice Agou
- Unité de Régulation Enzymatique des Activités Cellulaires, CNRS URA 2185, 75724 Paris, France.
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123
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Abstract
The transcription factor NF-kappaB has been the focus of intense investigation for nearly two decades. Over this period, considerable progress has been made in determining the function and regulation of NF-kappaB, although there are nuances in this important signaling pathway that still remain to be understood. The challenge now is to reconcile the regulatory complexity in this pathway with the complexity of responses in which NF-kappaB family members play important roles. In this review, we provide an overview of established NF-kappaB signaling pathways with focus on the current state of research into the mechanisms that regulate IKK activation and NF-kappaB transcriptional activity.
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Affiliation(s)
- Matthew S Hayden
- Section of Immunobiology and Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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124
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May MJ, Larsen SE, Shim JH, Madge LA, Ghosh S. A Novel Ubiquitin-like Domain in IκB Kinase β Is Required for Functional Activity of the Kinase. J Biol Chem 2004; 279:45528-39. [PMID: 15319427 DOI: 10.1074/jbc.m408579200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of NF-kappaB requires two highly related kinases named IKKalpha and IKKbeta that share identity in the nature and positioning of their structural domains. Despite their similarity, the kinases are functionally divergent, and we therefore sought to identify any structural features specific for IKKalpha or IKKbeta. We performed bioinformatics analysis, and we identified a region resembling a ubiquitin-like domain (UBL) that exists only in IKKbeta and that we named the UBL-like domain (ULD). Deletion of the ULD rendered IKKbeta catalytically inactive and unable to induce NF-kappaB activity, and overexpression of only the ULD dose-dependently inhibited tumor necrosis factor-alpha-induced NF-kappaB activity. The ULD could not be functionally replaced within IKKbeta by ubiquitin or the corresponding region of IKKalpha, whereas deletion of the equivalent section of IKKalpha did not affect its catalytic activity against IkappaBalpha or its activation by NF-kappaB-inducing kinase. We identified five residues conserved among the larger family of UBL-containing proteins and IKKbeta, and alanine scanning revealed that the leucine at position 353 (Leu(353)) is absolutely critical for IKKbeta-induced NF-kappaB activation. Most intriguingly, the L353A mutant was catalytically active but, unlike wild-type IKKbeta, formed a stable complex with the NF-kappaB p65 subunit. Our findings therefore establish the ULD as a critical functional domain specific for IKKbeta that might play a role in dissociating IKKbeta from p65.
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Affiliation(s)
- Michael J May
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104, USA
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125
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Dai S, Hirayama T, Abbas S, Abu-Amer Y. The IkappaB kinase (IKK) inhibitor, NEMO-binding domain peptide, blocks osteoclastogenesis and bone erosion in inflammatory arthritis. J Biol Chem 2004; 279:37219-22. [PMID: 15252035 DOI: 10.1074/jbc.c400258200] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of NF-kappaB leads to expression of ample genes that regulate inflammatory and osteoclastogenic responses. The process is facilitated by induction of IkappaB kinase (IKK) complex that phosphorylates IkappaB and leads to its dissociation from the NF-kappaB complex, thus permitting activation of NF-kappaB. The IKK complex contains primarily IKKalpha, IKKbeta, and the regulatory kinase IKKgamma, also known as NEMO. NEMO regulates the IKK complex activity through its binding to carboxyl-terminal region of IKKalpha and IKKbeta, termed NEMO-binding domain (NBD). In this regard, a cell-permeable NBD peptide has been shown to block association of NEMO with the IKK complex and inhibit activation of NF-kappaB. Given the pivotal role of cytokine-induced NF-kappaB in osteoclastogenesis and inflammatory bone loss, we deduced that cell-permeable TAT-NBD peptide may hinder osteoclastogenesis and bone erosion in inflammatory arthritis. Using NBD peptides, we show that wild type, but not mutant, NBD blocks IKK activation and reduces cytokine-induced promoter and DNA binding activities of NF-kappaB and inhibits cytokine-induced osteoclast formation by osteoclast precursors. Consistent with the key role of NF-kappaB in osteoinflammatory responses in vivo, wild type TAT-NBD administered into mice prior to induction of inflammatory arthritis efficiently block in vivo osteoclastogenesis, inhibits focal bone erosion, and ameliorates inflammatory responses in the joints of arthritic mice. The mutant NBD peptide fails to exert these functions. These results provide strong evidence that IKKs are potent regulators of cytokine-induced osteoclastogenesis and inflammatory arthritis. More importantly, blockade of NEMO assembly with the IKK complex is a viable strategy to avert inflammatory osteolysis.
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Affiliation(s)
- Simon Dai
- Department of Orthopaedics and Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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126
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Liu WK, Yen PF, Chien CY, Fann MJ, Su JY, Chou CK. The inhibitor ABIN-2 disrupts the interaction of receptor-interacting protein with the kinase subunit IKKgamma to block activation of the transcription factor NF-kappaB and potentiate apoptosis. Biochem J 2004; 378:867-76. [PMID: 14653779 PMCID: PMC1224013 DOI: 10.1042/bj20031736] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2003] [Revised: 11/26/2003] [Accepted: 12/01/2003] [Indexed: 11/17/2022]
Abstract
NF-kappaB (nuclear factor kappaB) proteins are key transcription factors that regulate gene expression in response to various extracellular stimuli. The pathway leading to the activation of NF-kappaB involves a complicated network that includes a number of signalling molecules. The recent identification of a wide range of negative regulators of NF-kappaB has given another layer of complexity in NF-kappaB activation. We and others have previously identified the protein ABIN-2 (A20 binding inhibitor of NF-kappaB 2) as an inhibitor of NF-kappaB activation. In the present paper, we demonstrate that ABIN-2 exerts its inhibitory function by blocking the interaction of RIP (receptor-interacting protein) with the downstream effector IKKgamma, a non-kinase component of the IkappaB (inhibitory kappaB) kinase complex. When overexpressed in cells, ABIN-2 bound to IKKgamma and prevented the association of IKKgamma with RIP. By a deletion mapping, a stretch of 50 amino acids on ABIN-2 is found to be essential for its interaction with IKKgamma. The ABIN-2 mutant that lacked these 50 amino acids did not interact with IKKgamma and, consequently, failed to inhibit NF-kappaB activation. Strikingly, a portion of RIP, which is similar to this 50-residue domain of ABIN-2, is also essential for RIP interaction with IKKgamma. The RIP mutant with deletion of this similar region did not associate with IKKgamma and had substantial reduction of its ability to mediate NF-kappaB activation. Taken together, these conserved 50 residues of ABIN-2 and RIP define a novel structural domain in mediating a key step in the NF-kappaB signalling pathway through the interaction with IKKgamma. Finally, the signalling pathway of NF-kappaB activation is known to promote survival in many cellular events. The mechanism for decision between cell death and survival is under fine regulation. In the present paper, we demonstrated further that the expression of ABIN-2 could promote the RIP-mediated apoptosis by presumably suppressing the anti-apoptotic effect of NF-kappaB.
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Affiliation(s)
- Wei-Kuang Liu
- Institute of Microbiology and Immunology, National Yang-Ming University, 155, Sec. 2, Li-Rong Street, Pei-Tou, Taipei 11211, Taiwan, Republic of China
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127
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Jimi E, Aoki K, Saito H, D'Acquisto F, May MJ, Nakamura I, Sudo T, Kojima T, Okamoto F, Fukushima H, Okabe K, Ohya K, Ghosh S. Selective inhibition of NF-κB blocks osteoclastogenesis and prevents inflammatory bone destruction in vivo. Nat Med 2004; 10:617-24. [PMID: 15156202 DOI: 10.1038/nm1054] [Citation(s) in RCA: 404] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Accepted: 05/06/2004] [Indexed: 11/09/2022]
Abstract
Bone destruction is a pathological hallmark of several chronic inflammatory diseases, including rheumatoid arthritis and periodontitis. Inflammation-induced bone loss of this sort results from elevated numbers of bone-resorbing osteoclasts. Gene targeting studies have shown that the transcription factor nuclear factor-kappa B (NF-kappa B) has a crucial role in osteoclast differentiation, and blocking NF-kappa B is a potential strategy for preventing inflammatory bone resorption. We tested this approach using a cell-permeable peptide inhibitor of the I kappa B-kinase complex, a crucial component of signal transduction pathways to NF-kappa B. The peptide inhibited RANKL-stimulated NF-kappa B activation and osteoclastogenesis both in vitro and in vivo. In addition, this peptide significantly reduced the severity of collagen-induced arthritis in mice by reducing levels of tumor necrosis factor-alpha and interleukin-1 beta, abrogating joint swelling and reducing destruction of bone and cartilage. Therefore, selective inhibition of NF-kappa B activation offers an effective therapeutic approach for inhibiting chronic inflammatory diseases involving bone resorption.
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Affiliation(s)
- Eijiro Jimi
- Section of Immunobiology and Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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128
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Abstract
The nuclear factor (NF)-kappaB pathway is important for the expression of a wide variety of genes that are involved in the control of the host immune and inflammatory response, and in the regulation of cellular proliferation and survival. The constitutive activation of this pathway is associated with inflammatory and autoimmune diseases, such as asthma, rheumatoid arthritis and inflammatory bowel disease, in addition to atherosclerosis, Alzheimer's disease, cancer and diabetes. One of the key steps in activating the NF-kappaB pathway is the stimulation of the IkappaB (inhibitor of kappaB) kinases. Recent data indicate that these kinases activate the NF-kappaB pathway through distinct steps that are operative in both the cytoplasm and the nucleus. A better understanding of the mechanisms that activate this pathway provides the potential for defining new therapeutic targets that might prevent the aberrant activation of NF-kappaB in a variety of human diseases.
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Affiliation(s)
- Yumi Yamamoto
- Division of Hematology-Oncology, Department of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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129
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Marienfeld R, May MJ, Berberich I, Serfling E, Ghosh S, Neumann M. RelB forms transcriptionally inactive complexes with RelA/p65. J Biol Chem 2003; 278:19852-60. [PMID: 12657634 DOI: 10.1074/jbc.m301945200] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RelB is an unusual member of the NF-kappaB transcription factor family that acts as both a transcriptional activator as well as a repressor of NF-kappaB-dependent gene expression. Although RelB promotes gene expression when it associates with p50/NF-kappaB1 or p52/NF-kappaB2, the precise molecular mechanisms through which it represses NF-kappaB remain unclear. To examine this inhibitory function in more detail, we employed reporter gene assays and found that RelB represses at the level of RelA. Furthermore, electrophoretic mobility shift analysis revealed that in vitro translated RelB impaired the DNA binding activity of RelA and that overexpressed RelB significantly reduced tumor necrosis factor-alpha-induced RelA activity in murine embryonic fibroblasts. Intriguingly, this inhibitory effect was due to the formation of RelA.RelB heterodimers that were unable to bind to kappaB sites in vitro strongly suggesting that these newly described NF-kappaB dimers cannot bind DNA. Expression pattern analysis revealed that RelA.RelB heterodimers appeared at relatively low levels in both lymphoid and non-lymphoid cells. However, the presence of these complexes increased following stimulation with phorbolesters or lipopolysaccharide or by overexpression of constitutively active IKKbeta. Functional characterization of RelA.RelB heterodimers in NIH3T3 murine embryonic fibroblasts revealed that they are not regulated by IkappaB proteins and are located in both the cytoplasm and the nucleus. Taken together, our findings demonstrate that sequestration of RelA in transcriptionally inactive RelA.RelB complexes provides a molecular mechanism that may explain the repressive role of RelB on NF-kappaB-dependent gene expression.
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Affiliation(s)
- Ralf Marienfeld
- Section of Immunobiology and Department of Molecular Biophysics and Biochemistry, Yale University Medical School, New Haven, Connecticut 06520, USA.
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130
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Tegethoff S, Behlke J, Scheidereit C. Tetrameric oligomerization of IkappaB kinase gamma (IKKgamma) is obligatory for IKK complex activity and NF-kappaB activation. Mol Cell Biol 2003; 23:2029-41. [PMID: 12612076 PMCID: PMC149477 DOI: 10.1128/mcb.23.6.2029-2041.2003] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The IkappaB kinase (IKK) complex mediates activation of transcription factor NF-kappaB by phosphorylation of IkappaB proteins. Its catalytic subunits, IKKalpha and IKKbeta, require association with the regulatory IKKgamma (NEMO) component to gain full basal and inducible kinase activity. However, the oligomeric composition of the IKK complex and its regulation by IKKgamma are poorly understood. We show here that IKKgamma predominantly forms tetramers and interacts with IKKalpha or IKKbeta in this state. We propose that tetramerization is accomplished by a prerequisite dimerization through a C-terminal coiled-coil minimal oligomerization domain (MOD). This is followed by dimerization of the dimers with their N-terminal sequences. Tetrameric IKKgamma sequesters four kinase molecules, yielding a gamma(4)(alpha/beta)(4) stoichiometry. Deletion of the MOD leads to loss of tetramerization and of phosphorylation of IKKbeta and IKKgamma, although the kinase can still interact with the resultant IKKgamma monomers and dimers. Likewise, MOD-mediated IKKgamma tetramerization is required to enhance IKKbeta kinase activity when overexpressed in 293 cells and to reconstitute a lipopolysaccharide-responsive IKK complex in pre-B cells. These data thus suggest that IKKgamma tetramerization enforces a spatial positioning of two kinase dimers to facilitate transautophosphorylation and activation.
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Affiliation(s)
- Sebastian Tegethoff
- Cell Growth and Differentiation Program, Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13092 Berlin, Germany
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