201
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Abstract
This review will focus on the role of nuclear factor kappaB (NF-kappaB) signaling in hematopoietic differentiation. We will also discuss several hematopoietic pathologies associated with deregulation of NF-kappaB and their potential therapies.
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Affiliation(s)
- V Bottero
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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202
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Liang C, Zhang M, Sun SC. beta-TrCP binding and processing of NF-kappaB2/p100 involve its phosphorylation at serines 866 and 870. Cell Signal 2006; 18:1309-17. [PMID: 16303288 DOI: 10.1016/j.cellsig.2005.10.011] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 10/07/2005] [Indexed: 12/30/2022]
Abstract
Processing of the NF-kappaB2 precursor protein p100 is a major step in noncanonical NF-kappaB signaling. This signaling step requires the NF-kappaB inducing kinase (NIK) and its downstream kinase, IkappaB kinase alpha (IKKalpha). We show here that p100 undergoes phosphorylation at serines 866, 870, and possibly 872, in cells stimulated with noncanonical NF-kappaB stimuli or transfected with NIK and IKKalpha. Phosphorylation of this serine cluster creates a binding site for beta-TrCP, the receptor subunit of the beta-TrCP(SCF) ubiquitin ligase. Mutation of either serine 866 or serine 870 abolishes the beta-TrCP recruitment and ubiquitination of p100. The functional significance of p100 phosphorylation is further supported by the finding that this molecular event occurs in a NIK- and IKKalpha-dependent manner. Additionally, induction of p100 phosphorylation can be blocked by a protein synthesis inhibitor, suggesting the requirement of de novo protein synthesis. These data suggest that p100 processing involves its phosphorylation at specific terminal serines, which form a binding site for beta-TrCP thereby regulating p100 ubiquitination.
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Affiliation(s)
- Chunyang Liang
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey Medical Center, P.O. Box 850, Hershey, Pennsylvania 17033, USA
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203
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Ishimaru N, Kishimoto H, Hayashi Y, Sprent J. Regulation of naive T cell function by the NF-kappaB2 pathway. Nat Immunol 2006; 7:763-72. [PMID: 16732290 DOI: 10.1038/ni1351] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 04/26/2006] [Indexed: 11/08/2022]
Abstract
T cell activation involves the orchestration of several signaling pathways, including that of the 'classical' transcription factor NF-kappaB components NF-kappaB1-RelA. The function of the 'nonclassical' NF-kappaB2-RelB pathway is less clear, although T cells lacking components of this pathway have activation defects. Here we show that mice deficient in NF-kappaB-inducing kinase have a complex phenotype consisting of immunosuppression mediated by CD25(-)Foxp3(-) memory CD4(+) cells and, in the absence of those cells, hyper-responsive naive CD4(+) T cells, which caused autoimmune lesions after adoptive transfer into hosts deficient in recombination-activating genes. Biochemical studies indicated involvement of a cell-intrinsic mechanism in which NF-kappaB2 (p100) limits nuclear translocation of NF-kappaB1-RelA and thereby functions as a regulatory 'brake' for the activation of naive T cells.
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204
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Sun L, Peng Y, Sharrow AC, Iqbal J, Zhang Z, Papachristou DJ, Zaidi S, Zhu LL, Yaroslavskiy BB, Zhou H, Zallone A, Sairam MR, Kumar TR, Bo W, Braun J, Cardoso-Landa L, Schaffler MB, Moonga BS, Blair HC, Zaidi M. FSH Directly Regulates Bone Mass. Cell 2006; 125:247-60. [PMID: 16630814 DOI: 10.1016/j.cell.2006.01.051] [Citation(s) in RCA: 490] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 09/02/2005] [Accepted: 01/23/2006] [Indexed: 11/29/2022]
Abstract
Postmenopausal osteoporosis, a global public health problem, has for decades been attributed solely to declining estrogen levels. Although FSH levels rise sharply in parallel, a direct effect of FSH on the skeleton has never been explored. We show that FSH is required for hypogonadal bone loss. Neither FSHbeta nor FSH receptor (FSHR) null mice have bone loss despite severe hypogonadism. Bone mass is increased and osteoclastic resorption is decreased in haploinsufficient FSHbeta+/- mice with normal ovarian function, suggesting that the skeletal action of FSH is estrogen independent. Osteoclasts and their precursors possess G(i2alpha)-coupled FSHRs that activate MEK/Erk, NF-kappaB, and Akt to result in enhanced osteoclast formation and function. We suggest that high circulating FSH causes hypogonadal bone loss.
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Affiliation(s)
- Li Sun
- Mount Sinai Bone Program, Department of Medicine and Department of Orthopedics, Mount Sinai School of Medicine, New York, NY 10029, USA
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205
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Natasha T, Kuhn M, Kelly O, Rittling SR. Override of the osteoclast defect in osteopontin-deficient mice by metastatic tumor growth in the bone. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 168:551-61. [PMID: 16436669 PMCID: PMC1606503 DOI: 10.2353/ajpath.2006.050480] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Osteopontin (OPN) is a major noncollagenous protein of bone that is frequently up-regulated in tumors, where it enhances tumor growth. OPN-deficient mice are resistant to stimulated bone resorption, including that occurring after ovariectomy. Using a new syngeneic model of bone metastasis (r3T), we examined whether OPN-deficient mice are similarly resistant to bone loss resulting from osteolytic tumor growth. Transformed mammary epithelial cells, r3T, which express parathyroid hormone-related protein but not receptor activator of nuclear factor-kappaB ligand, were injected via the intracardiac route into both wild-type and OPN-/- mice. We measured tumor burden in the bone by quantitative polymerase chain reaction assay and evaluated bone loss by X-ray and microCT. Unexpectedly, bone loss was similar in OPN-/- and wild-type mice bearing similar-sized tumors. Osteoclast number was comparable in both genotypes, and the expression of bone sialoprotein was similar in tumor-bearing bones of both genotypes, excluding two potential mechanisms of overriding the defect. Taken together, these results indicate that in the absence of OPN, the bone loss associated with tumor growth at the bone site proceeds rapidly despite the osteoclast defects documented in OPN-/- mice, suggesting that the mechanism of bone loss due to tumor growth differs from that occurring in other pathologies.
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Affiliation(s)
- Tajneen Natasha
- Department of Genetics, Rutgers University, Piscataway, New Jersey, USA
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206
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Ichikawa H, Aggarwal BB. Guggulsterone inhibits osteoclastogenesis induced by receptor activator of nuclear factor-kappaB ligand and by tumor cells by suppressing nuclear factor-kappaB activation. Clin Cancer Res 2006; 12:662-8. [PMID: 16428513 DOI: 10.1158/1078-0432.ccr-05-1749] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Bone resorption is commonly associated with aging and with certain types of cancer, including multiple myeloma and breast cancer. What induces bone resorption is not fully understood, but the role of osteoclasts is well established. Recently, receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL), a member of the tumor necrosis factor superfamily, was implicated as a major mediator of bone resorption, suggesting that agents that can suppress RANKL signaling have the potential to inhibit bone resorption or osteoclastogenesis. Guggulsterone [4,17(20)-pregnadiene-3,16-dione], isolated from the guggul tree Commiphora mukul and used to treat osteoarthritis and bone fractures, was recently shown to antagonize the farnesoid X receptor, decrease the expression of bile acid-activated genes, and suppress the NF-kappaB activation induced by various carcinogens. We investigated whether guggulsterone could modulate RANKL signaling and osteoclastogenesis induced by RANKL or tumor cells. We found that treatment of monocytes with guggulsterone suppressed RANKL-activated NF-kappaB activation (as indicated by gel-shift assay) and that this suppression correlated with inhibition of IkappaBalpha kinase and phosphorylation and degradation of IkappaBalpha, an inhibitor of NF-kappaB. Guggulsterone also suppressed the differentiation of monocytes to osteoclasts in a dose-dependent and time-dependent manner. Suppression of osteoclastogenesis by the NF-kappaB-specific inhibitory peptide implies a link between NF-kappaB and osteoclastogenesis. Finally, differentiation to osteoclasts induced by coincubating human breast tumor cells (MDA-MB-468) or human multiple myeloma (U266) cells with monocytes was also completely suppressed by guggulsterone. Collectively, our results indicate that guggulsterone suppresses RANKL and tumor cell-induced osteoclastogenesis by suppressing the activation of NF-kappaB.
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Affiliation(s)
- Haruyo Ichikawa
- Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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207
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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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208
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Crucial Roles of NF-κB for T Cell Activation. J Oral Biosci 2006. [DOI: 10.1016/s1349-0079(06)80014-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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209
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Demicco EG, Kavanagh KT, Romieu-Mourez R, Wang X, Shin SR, Landesman-Bollag E, Seldin DC, Sonenshein GE. RelB/p52 NF-kappaB complexes rescue an early delay in mammary gland development in transgenic mice with targeted superrepressor IkappaB-alpha expression and promote carcinogenesis of the mammary gland. Mol Cell Biol 2005; 25:10136-47. [PMID: 16260626 PMCID: PMC1280249 DOI: 10.1128/mcb.25.22.10136-10147.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Classical NF-kappaB (p65/p50) transcription factors display dynamic induction in the mammary gland during pregnancy. To further elucidate the role of NF-kappaB factors in breast development, we generated a transgenic mouse expressing the IkappaB-alpha S32/36A superrepressor (SR) protein under control of the mouse mammary tumor virus (MMTV) long terminal repeat promoter. A transient delay in mammary ductal branching was observed in MMTV-SR-IkappaB-alpha mice early during pregnancy at day 5.5 (d5.5) and d7.5; however, development recovered by mid- to late pregnancy (d14.5). Recovery correlated with induction of nuclear cyclin D1 and RelB/p52 NF-kappaB complexes. RelB/p52 complexes induced cyclin D1 and c-myc promoter activities and failed in electrophoretic mobility shift assay to interact with IkappaB-alpha-glutathione S-transferase, indicating that their weak interaction with IkappaB-alpha can account for the observed recovery of mammary gland development. Activation of IKKalpha and NF-kappaB-inducing kinase was detected by d5.5, implicating the alternative NF-kappaB signaling pathway in RelB/p52 induction. Constitutively active IKKalpha induced p52, RelB, and cyclin D1 in untransformed mammary epithelial cells. Moreover, mouse mammary tumors induced by 7,12-dimethylbenz(a)anthracene treatment displayed increased RelB/p52 activity. Inhibition of RelB in breast cancer cells repressed cyclin D1 and c-Myc levels and growth in soft agar. These results implicate RelB/p52 complexes in mammary gland development and carcinogenesis.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/pharmacology
- Agar/chemistry
- Animals
- Breast Neoplasms/metabolism
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Cyclin D1/metabolism
- Female
- Glutathione Transferase/metabolism
- Humans
- I-kappa B Kinase/metabolism
- I-kappa B Proteins/biosynthesis
- Immunoblotting
- Mammary Glands, Animal/embryology
- Mammary Glands, Animal/metabolism
- Mammary Neoplasms, Animal/chemically induced
- Mammary Neoplasms, Animal/genetics
- Mammary Neoplasms, Animal/metabolism
- Mice
- Mice, Transgenic
- NF-KappaB Inhibitor alpha
- NF-kappa B/metabolism
- NF-kappa B p52 Subunit/chemistry
- NF-kappa B p52 Subunit/physiology
- Phenotype
- Pregnancy
- Pregnancy, Animal
- Promoter Regions, Genetic
- Protein Binding
- Proto-Oncogene Proteins c-myc/metabolism
- RNA/metabolism
- Time Factors
- Transcription Factor RelA/metabolism
- Transcription Factor RelB/chemistry
- Transcription Factor RelB/physiology
- Transfection
- Transgenes
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Affiliation(s)
- Elizabeth G Demicco
- Department of Biochemistry, Boston University School of Medicine, 715 Albany Street, Boston, Massachusetts 02118, USA
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210
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Ruocco MG, Karin M. IKK{beta} as a target for treatment of inflammation induced bone loss. Ann Rheum Dis 2005; 64 Suppl 4:iv81-5. [PMID: 16239395 PMCID: PMC1766902 DOI: 10.1136/ard.2005.042721] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The transcription factor nuclear factor (NF)-kappaB is well recognised as a pivotal player in osteoclastogenesis and inflammation induced bone loss. Here, the authors discuss their recent results, obtained using a genetic approach in mice, that indicate the importance of IKKbeta, and not IKKalpha, as a transducer of signals from receptor activator of NF-kappaB (RANK) to NF-kappaB. Ablation of IKKbeta results in lack of osteoclastogenesis and unresponsiveness of IKKbeta deficient mice to inflammation induced bone loss. In the need of a more effective therapy for the treatment of inflammatory diseases causing bone resorption, specific inhibition of IKKbeta represents a logical alternative strategy to the current therapies.
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Affiliation(s)
- M G Ruocco
- Laboratory of Gene Regulation and Signal Transduction, School of Medicine, University of California at San Diego, La Jolla, CA, USA
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211
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212
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Abstract
Periarticular osteolysis, a crippling complication of rheumatoid arthritis, is the product of enhanced osteoclast recruitment and activation. The osteoclast, which is a member of the monocyte/macrophage family, is the exclusive bone resorptive cell, and its differentiation and activation are under the aegis of a variety of cytokines. Receptor activator of NF-kappaB ligand (RANKL) and macrophage colony-stimulating factor are the essential osteoclastogenic cytokines and are increased in inflammatory joint disease. Tumor necrosis factor-alpha, which perpetrates arthritic bone loss, exerts its osteoclastogenic effect in the context of RANKL with which it synergizes. Achieving an understanding of the mechanisms by which the three cytokines affect the osteoclast has resulted in a number of active and candidate therapeutic targets.
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Affiliation(s)
- Steven L Teitelbaum
- Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8118, St Louis, MO 63110, USA.
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213
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Sun SC, Yamaoka S. Activation of NF-kappaB by HTLV-I and implications for cell transformation. Oncogene 2005; 24:5952-64. [PMID: 16155602 DOI: 10.1038/sj.onc.1208969] [Citation(s) in RCA: 182] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
T-cell transformation by the human T-cell leukemia virus type I (HTLV-I) involves deregulation of cellular transcription factors, including members of the NF-kappaB family. In normal T cells, NF-kappaB activation occurs transiently in response to immune stimuli, which is required for antigen-stimulated T-cell proliferation and survival. However, HTLV-I induces persistent activation of NF-kappaB, causing deregulated expression of a large array of cellular genes, which in turn contributes to the induction of T-cell transformation. The HTLV-I transforming protein Tax functions as an intracellular stimulator of IkappaB kinase (IKK), a cellular kinase mediating NF-kappaB activation by diverse stimuli. Tax physically interacts with IKK and renders this inducible kinase constitutively active. By assembling different Tax/IKK complexes, Tax targets the persistent activation of both canonical and noncanonical NF-kappaB signaling pathways. Whereas Tax plays a primary role in HTLV-I-mediated NF-kappaB activation, recent studies reveal that the IKK/NF-kappaB signaling pathway is also activated in freshly isolated adult T-cell leukemia (ATL) cells that often lack detectable Tax expression. The mechanism underlying this Tax-independent pathway of NF-kappaB activation remains poorly understood. Clarifying the precise nature and consequences of the constitutive NF-kappaB activation in ATL cells is important for developing rational therapeutic strategies for this T-cell malignancy.
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Affiliation(s)
- Shao-Cong Sun
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA.
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214
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Bai S, Kitaura H, Zhao H, Chen J, Müller JM, Schüle R, Darnay B, Novack DV, Ross FP, Teitelbaum SL. FHL2 inhibits the activated osteoclast in a TRAF6-dependent manner. J Clin Invest 2005; 115:2742-51. [PMID: 16184196 PMCID: PMC1224296 DOI: 10.1172/jci24921] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Accepted: 07/12/2005] [Indexed: 12/26/2022] Open
Abstract
TNF receptor-associated factor 6 (TRAF6) associates with the cytoplasmic domain of receptor activator of NF-kappaB (RANK). This event is central to normal osteoclastogenesis. We discovered that TRAF6 also interacts with FHL2 (four and a half LIM domain 2), a LIM domain--only protein that functions as a transcriptional coactivator or corepressor in a cell-type--specific manner. FHL2 mRNA and protein are undetectable in marrow macrophages and increase pari passu with osteoclast differentiation in vitro. FHL2 inhibits TRAF6-induced NF-kappaB activity in wild-type osteoclast precursors and, in keeping with its role as a suppressor of TRAF6-mediated RANK signaling, TRAF6/RANK association is enhanced in FHL2-/- osteoclasts. FHL2 overexpression delays RANK ligand-induced (RANKL-induced) osteoclast formation and cytoskeletal organization. Interestingly, osteoclast-residing FHL2 is not detectable in naive wild-type mice, in vivo, but is abundant in those treated with RANKL and following induction of inflammatory arthritis. Reflecting increased RANKL sensitivity, osteoclasts generated from FHL2-/- mice reach maturation and optimally organize their cytoskeleton earlier than their wild-type counterparts. As a consequence, FHL2-/- osteoclasts are hyperresorptive, and mice lacking the protein undergo enhanced RANKL and inflammatory arthritis-stimulated bone loss. FHL2 is, therefore, an antiosteoclastogenic molecule exerting its effect by attenuating TRAF6-mediated RANK signaling.
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Affiliation(s)
- Shuting Bai
- Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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215
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Pavlos NJ, Xu J, Riedel D, Yeoh JSG, Teitelbaum SL, Papadimitriou JM, Jahn R, Ross FP, Zheng MH. Rab3D regulates a novel vesicular trafficking pathway that is required for osteoclastic bone resorption. Mol Cell Biol 2005; 25:5253-69. [PMID: 15923639 PMCID: PMC1140603 DOI: 10.1128/mcb.25.12.5253-5269.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Rab3 proteins are a subfamily of GTPases, known to mediate membrane transport in eukaryotic cells and play a role in exocytosis. Our data indicate that Rab3D is the major Rab3 species expressed in osteoclasts. To investigate the role of Rab3D in osteoclast physiology we examined the skeletal architecture of Rab3D-deficient mice and found an osteosclerotic phenotype. Although basal osteoclast number in null animals is normal the total eroded surface is significantly reduced, suggesting that the resorptive defect is due to attenuated osteoclast activity. Consistent with this hypothesis, ultrastructural analysis reveals that Rab3D(-/-) osteoclasts exhibit irregular ruffled borders. Furthermore, while overexpression of wild-type, constitutively active, or prenylation-deficient Rab3D has no significant effects, overexpression of GTP-binding-deficient Rab3D impairs bone resorption in vitro. Finally, subcellular localization studies reveal that, unlike wild-type or constitutively active Rab3D, which associate with a nonendosomal/lysosomal subset of post-trans-Golgi network (TGN) vesicles, inactive Rab3D localizes to the TGN and inhibits biogenesis of Rab3D-bearing vesicles. Collectively, our data suggest that Rab3D modulates a post-TGN trafficking step that is required for osteoclastic bone resorption.
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Affiliation(s)
- Nathan J Pavlos
- Unit of Orthopaedics, School of Surgery and Pathology, University of Western Australia, 2nd Floor M Block, QEII Medical Centre, Nedlands, Perth, Western Australia 6009, Australia
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216
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Ruocco MG, Maeda S, Park JM, Lawrence T, Hsu LC, Cao Y, Schett G, Wagner EF, Karin M. I{kappa}B kinase (IKK){beta}, but not IKK{alpha}, is a critical mediator of osteoclast survival and is required for inflammation-induced bone loss. ACTA ACUST UNITED AC 2005; 201:1677-87. [PMID: 15897281 PMCID: PMC2212920 DOI: 10.1084/jem.20042081] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Transcription factor, nuclear factor kappaB (NF-kappaB), is required for osteoclast formation in vivo and mice lacking both of the NF-kappaB p50 and p52 proteins are osteopetrotic. Here we address the relative roles of the two catalytic subunits of the IkappaB kinase (IKK) complex that mediate NF-kappaB activation, IKKalpha and IKKbeta, in osteoclast formation and inflammation-induced bone loss. Our findings point out the importance of the IKKbeta subunit as a transducer of signals from receptor activator of NF-kappaB (RANK) to NF-kappaB. Although IKKalpha is required for RANK ligand-induced osteoclast formation in vitro, it is not needed in vivo. However, IKKbeta is required for osteoclastogenesis in vitro and in vivo. IKKbeta also protects osteoclasts and their progenitors from tumor necrosis factor alpha-induced apoptosis, and its loss in hematopoietic cells prevents inflammation-induced bone loss.
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Affiliation(s)
- Maria Grazia Ruocco
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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217
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Aya K, Alhawagri M, Hagen-Stapleton A, Kitaura H, Kanagawa O, Novack DV. NF-(kappa)B-inducing kinase controls lymphocyte and osteoclast activities in inflammatory arthritis. J Clin Invest 2005; 115:1848-54. [PMID: 15937549 PMCID: PMC1142111 DOI: 10.1172/jci23763] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2004] [Accepted: 04/21/2005] [Indexed: 01/01/2023] Open
Abstract
NF-(kappa)B is an important component of both autoimmunity and bone destruction in RA. NF-(kappa)B-inducing kinase (NIK) is a key mediator of the alternative arm of the NF-(kappa)B pathway, which is characterized by the nuclear translocation of RelB/p52 complexes. Mice lacking functional NIK have no peripheral lymph nodes, defective B and T cells, and impaired receptor activator of NF-kappaB ligand-stimulated osteoclastogenesis. We investigated the role of NIK in murine models of inflammatory arthritis using Nik-/- mice. The serum transfer arthritis model is initiated by preformed antibodies and required only intact neutrophil and complement systems in recipients. While Nik-/- mice had inflammation equivalent to that of Nik+/+ controls, they showed significantly less periarticular osteoclastogenesis and less bone erosion. In contrast, Nik-/- mice were completely resistant to antigen-induced arthritis (AIA), which requires intact antigen presentation and lymphocyte function but not lymph nodes. Additionally, transfer of Nik+/+ splenocytes or T cells to Rag2-/- mice conferred susceptibility to AIA, while transfer of Nik-/- cells did not. Nik-/- mice were also resistant to a genetic, spontaneous form of arthritis, generated in mice expressing both the KRN T cell receptor and H-2. Thus, NIK is important in the immune and bone-destructive components of inflammatory arthritis and represents a possible therapeutic target for these diseases.
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Affiliation(s)
- Kunihiko Aya
- Department of Pathology and Immunology, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan
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218
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Nonaka M, Horie R, Itoh K, Watanabe T, Yamamoto N, Yamaoka S. Aberrant NF-kappaB2/p52 expression in Hodgkin/Reed-Sternberg cells and CD30-transformed rat fibroblasts. Oncogene 2005; 24:3976-86. [PMID: 15782119 DOI: 10.1038/sj.onc.1208564] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Overexpression of CD30 and constitutive nuclear factor-kappaB (NF-kappaB) activation are hallmarks of the malignant Hodgkin Reed-Sternberg (H-RS) cells. Previous investigations have demonstrated that both proliferation and survival of H-RS cells require constitutive NF-kappaB activity, which is comprised of the p50 and RelA subunits. We report here enhanced expression of NF-kappaB2/p52 and RelB-containing NF-kappaB DNA-binding activity in Epstein-Barr virus-negative H-RS cells. Kinetic studies revealed that a proteasome inhibitor MG132 induced p100 accumulation with reduced p52 expression in H-RS cells, suggesting proteasome-dependent processing of p100. In addition, treatment with a protein synthesis inhibitor cycloheximide rapidly downregulated inhibitor of NF-kappaB (IkappaB) kinase activity in H-RS cells. We also demonstrate that overexpression of CD30 in rat fibroblasts at levels comparable to those in H-RS cells results in constitutive IkappaB kinase activation, proteasome-dependent p100 processing, and NF-kappaB-dependent cell transformation. Our results thus indicate that CD30 triggers the noncanonical NF-kappaB activation pathway, and suggest that deregulated CD30 signaling contributes to the neoplastic features of H-RS cells.
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Affiliation(s)
- Mizuho Nonaka
- Department of Molecular Virology, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Bunkyo-ku, Tokyo 113-8510, Japan
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219
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Abstract
The osteoclast is a monocyte-derived cell with complex regulatory control due to its role, balancing calcium homeostasis with skeletal modelling and repair. Normal differentiation requires tyrosine kinase- and tumor necrosis-family receptors, normally fms and RANK. Ligands for these receptors plus unidentified serum or cell-presented factor(s) are needed for in vitro differentiation, possibly signalling via an immune-like tyrosine kinase acceptor molecule. Osteoclast development and activity are increased by cytokines signalling through GP130, such as IL-6, by TGF-beta, and by IL-1, although these cannot replace serum. Other tyrosine kinase receptors including kit and met can augment fms signalling, and TNFs other than RANKL, including TNFalpha and TRAIL, modify RANK signalling, which is also susceptible to interference by interferons. The situation is further complicated by G-protein coupled receptors including the calcitonin receptor, by integrin or calcium-mediated signals, and by estrogen receptors, which operate in bone largely via NO downstream signals. Differentiation, activity, and survival signals merge in intracellular second messengers. These include cytoplasmic kinases of several families; differentiation pathways often terminate in Erk/Jun kinases or NF-kappaB. Key regulatory intermediates include TRAF6, src, Smad3, phosphatidylinositol-3-kinase, Jak/Stat, and the cGMP-dependent protein kinase I. There are substantial uncertainties regarding how intracellular agents connect to primary signals. The frontier includes characterization of how scaffolding/adapter proteins, such as cbl, gab, grb, p130Cas, and shc, as well as itam-containing proteins and nonreceptor tyrosine kinase adapters of the src and syk families, delimit and integrate signals of multiple receptors to bring about specific outcomes.
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Affiliation(s)
- Harry C Blair
- Department of Pathology, University of Pittsburgh, Veterans' Affairs Health System, Pittsburgh, PA 15261, USA.
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220
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Faccio R, Teitelbaum SL, Fujikawa K, Chappel J, Zallone A, Tybulewicz VL, Ross FP, Swat W. Vav3 regulates osteoclast function and bone mass. Nat Med 2005; 11:284-90. [PMID: 15711558 DOI: 10.1038/nm1194] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Accepted: 12/14/2004] [Indexed: 12/26/2022]
Abstract
Osteoporosis, a leading cause of morbidity in the elderly, is characterized by progressive loss of bone mass resulting from excess osteoclastic bone resorption relative to osteoblastic bone formation. Here we identify Vav3, a Rho family guanine nucleotide exchange factor, as essential for stimulated osteoclast activation and bone density in vivo. Vav3-deficient osteoclasts show defective actin cytoskeleton organization, polarization, spreading and resorptive activity resulting from impaired signaling downstream of the M-CSF receptor and alpha(v)beta3 integrin. Vav3-deficient mice have increased bone mass and are protected from bone loss induced by systemic bone resorption stimuli such as parathyroid hormone or RANKL. Moreover, we provide genetic and biochemical evidence for the role of Syk tyrosine kinase as a crucial upstream regulator of Vav3 in osteoclasts. Thus, Vav3 is a potential new target for antiosteoporosis therapy.
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Affiliation(s)
- Roberta Faccio
- Department of Pathology and Immunology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, Missouri 63110, USA
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221
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Morrison MD, Reiley W, Zhang M, Sun SC. An atypical tumor necrosis factor (TNF) receptor-associated factor-binding motif of B cell-activating factor belonging to the TNF family (BAFF) receptor mediates induction of the noncanonical NF-kappaB signaling pathway. J Biol Chem 2005; 280:10018-24. [PMID: 15644327 DOI: 10.1074/jbc.m413634200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BAFF receptor (BAFFR) is a member of the TNF receptor (TNFR) superfamily that regulates the survival and maturation of B cells. BAFFR exerts its signaling function by inducing activation of NF-kappaB, although the underlying mechanism has not been well defined. By using a chimeric BAFFR, we show that BAFFR preferentially induces the noncanonical NF-kappaB signaling pathway. This specific function of BAFFR is mediated by a sequence motif, PVPAT, which is homologous to the TRAF-binding site (PVQET) present in CD40, a TNFR known to induce both the canonical and noncanonical NF-kappaB pathways. Mutation of this putative TRAF-binding motif within BAFFR abolishes its interaction with TRAF3 as well as its ability to induce noncanonical NF-kappaB. Interestingly, modification of the PVPAT sequence to the typical TRAF-binding sequence, PVQET, is sufficient to render the BAFFR capable of inducing strong canonical NF-kappaB signaling. Further, this functional acquisition of the modified BAFFR is associated with its stronger and more rapid association with TRAF3. These findings suggest that the PVPAT sequence of BAFFR not only functions as a key signaling motif of BAFFR but also determines its signaling specificity in the induction of the noncanonical NF-kappaB pathway.
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Affiliation(s)
- Matthew D Morrison
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, Pennsylvania 17033, USA
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222
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Abstract
Processing of NF-kappa B2 precursor protein p100 to generate p52 is tightly regulated. However, this proteolytic event could be actively induced by the NF-kappa B-inducing kinase and the human T-cell leukemia virus-encoded oncoprotein Tax or be constitutively turned on due to the loss of the C-terminal portion of p100. Whereas NF-kappa B-inducing kinase-mediated p100 processing requires beta-transducin repeat-containing protein, constitutive processing of p100 is independent of this protein. On the other hand, Tax-induced processing of p100 appears to be both beta-transducin repeat-containing protein-dependent and -independent. We show here that, besides the C-terminal sequences, multiple functional regions, including the two alpha-helices, dimerization domain, nuclear localization sequence, and glycine-rich region, located in the N terminus of p100, also play important roles in both constitutive and inducible processing, suggesting a common mechanism for p100 processing. We further demonstrate that with the help of the C-terminal death domain and I kappa B kinase alpha-targeting serines, the C-terminal ankyrin-repeat domain of p100 strongly interacts with its N-terminal dimerization domain and nuclear localization sequence, thereby bringing the C- and N-terminal sequences together to form a three-dimensional domain. This presumptive domain is not only responsible for suppression of constitutive processing but also required for inducible processing of p100. Taken together, these studies highlight the mechanism by which the different sequences within p100 work in concert to regulate its processing and shed light on the mechanisms of how p100 processing is tightly and delicately controlled.
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Affiliation(s)
- Guoliang Qing
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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223
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Abstract
NF-kappaB and c-Fos are transcription factors that are activated in immune cells and in most other cell types following stimulation by a variety of factors, including cytokines, growth factors, and hormones. They regulate the expression of a large number of genes, and both are activated in osteoclast precursors after RANKL, IL-1, or TNF bind to their respective receptors. However, of these cytokines, only RANKL is required for the induction of osteoclast formation in vivo. Nevertheless, it is likely that IL-1, TNF, and other cytokines participate in the upregulation of osteoclast formation seen in a variety of conditions that affect the skeleton in which cytokine production is increased, including estrogen deficiency and inflammatory bone diseases. In this review, the RANKL/ OPG/RANK system and roles for NF-kappaB and c-Fos in osteoclasts are reviewed along with our current understanding of how this system may be disrupted in common bone diseases, such as postmenopausal osteoporosis, inflammatory arthritis, and Paget's disease.
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Affiliation(s)
- Brendan F Boyce
- Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box 626, Rochester, NY 14642, USA.
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224
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Chaisson ML, Branstetter DG, Derry JM, Armstrong AP, Tometsko ME, Takeda K, Akira S, Dougall WC. Osteoclast differentiation is impaired in the absence of inhibitor of kappa B kinase alpha. J Biol Chem 2004; 279:54841-8. [PMID: 15485831 DOI: 10.1074/jbc.m406392200] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Signaling through the receptor activator of nuclear factor kappa B (RANK) is required for both osteoclast differentiation and mammary gland development, yet the extent to which RANK utilizes similar signaling pathways in these tissues remains unclear. Mice expressing a kinase-inactive form of the inhibitor of kappa B kinase alpha (IKK alpha) have mammary gland defects similar to those of RANK-null mice yet have apparently normal osteoclast function. Because mice that completely lack IKK alpha have severe skin and skeletal defects that are not associated with IKK alpha-kinase activity, we wished to directly examine osteoclastogenesis in IKK alpha(-/-) mice. We found that unlike RANK-null mice, which completely lack osteoclasts, IKK alpha(-/-) mice did possess normal numbers of TRAP(+) osteoclasts. However, only 32% of these cells were multinucleated compared with 57% in wild-type littermates. A more profound defect in osteoclastogenesis was observed in vitro using IKK alpha(-/-) hematopoietic cells treated with colony-stimulating factor 1 and RANK ligand (RANKL), as the cells failed to form large, multinucleated osteoclasts. Additionally, overall RANKL-induced global gene expression was significantly blunted in IKK alpha(-/-) cells, including osteoclast-specific genes such as TRAP, MMP-9, and c-Src. IKK alpha was not required for RANKL-mediated I kappa B alpha degradation or phosphorylation of mitogen-activated protein kinases but was required for RANKL-induced p100 processing. Treatment of IKK alpha(-/-) cells with tumor necrosis factor alpha (TNF alpha) in combination with RANKL led to partial rescue of osteoclastogenesis despite a lack of p100 processing. However, the ability of TNF alpha alone or in combination with transforming growth factor beta to induce osteoclast differentiation was dependent on IKK alpha, suggesting that synergy between RANKL and TNFalpha can overcome p100 processing defects in IKK alpha(-/-) cells.
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Affiliation(s)
- Michelle L Chaisson
- Department of Cancer Biology, Amgen Incorporated, Seattle, Washington 98119, USA.
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225
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Beinke S, Ley S. Functions of NF-kappaB1 and NF-kappaB2 in immune cell biology. Biochem J 2004; 382:393-409. [PMID: 15214841 PMCID: PMC1133795 DOI: 10.1042/bj20040544] [Citation(s) in RCA: 468] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2004] [Revised: 06/22/2004] [Accepted: 06/24/2004] [Indexed: 01/01/2023]
Abstract
Two members of the NF-kappaB (nuclear factor kappaB)/Rel transcription factor family, NF-kappaB1 and NF-kappaB2, are produced as precursor proteins, NF-kappaB1 p105 and NF-kappaB2 p100 respectively. These are proteolytically processed by the proteasome to produce the mature transcription factors NF-kappaB1 p50 and NF-kappaB2 p52. p105 and p100 are known to function additionally as IkappaBs (inhibitors of NF-kappaB), which retain associated NF-kappaB subunits in the cytoplasm of unstimulated cells. The present review focuses on the latest advances in research on the function of NF-kappaB1 and NF-kappaB2 in immune cells. NF-kappaB2 p100 processing has recently been shown to be stimulated by a subset of NF-kappaB inducers, including lymphotoxin-beta, B-cell activating factor and CD40 ligand, via a novel signalling pathway. This promotes the nuclear translocation of p52-containing NF-kappaB dimers, which regulate peripheral lymphoid organogenesis and B-lymphocyte differentiation. Increased p100 processing also contributes to the malignant phenotype of certain T- and B-cell lymphomas. NF-kappaB1 has a distinct function from NF-kappaB2, and is important in controlling lymphocyte and macrophage function in immune and inflammatory responses. In contrast with p100, p105 is constitutively processed to p50. However, after stimulation with agonists, such as tumour necrosis factor-alpha and lipopolysaccharide, p105 is completely degraded by the proteasome. This releases associated p50, which translocates into the nucleus to modulate target gene expression. p105 degradation also liberates the p105-associated MAP kinase (mitogen-activated protein kinase) kinase kinase TPL-2 (tumour progression locus-2), which can then activate the ERK (extracellular-signal-regulated kinase)/MAP kinase cascade. Thus, in addition to its role in NF-kappaB activation, p105 functions as a regulator of MAP kinase signalling.
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Key Words
- iκb kinase (ikk)
- nuclear factor κb (nf-κb)
- p100
- p105
- toll-like receptor (tlr)
- tumour progression locus-2 (tpl-2)
- abin, a20-binding inhibitor of nuclear factor κb
- baff, b-cell activating factor
- bmdm, bone-marrow-derived macrophage
- βtrcp, β-transducin repeat-containing protein
- cox-2, cyclo-oxygenase-2
- dc, dendritic cell
- dd, death domain
- dif, dorsal-related immunity factor
- ebna1, ebv nuclear antigen 1
- ebv, epstein–barr virus
- erk, extracellular-signal-regulated kinase
- fn14, fibroblast-growth-factor-inducible 14
- gc, germinal centre
- gm-csf, granulocyte–macrophage colony-stimulating factor
- grr, glycine-rich region
- gsk, glycogen synthase kinase
- htlv-1, human t-cell leukaemia virus type 1
- ifnβ, interferon-β
- iκb, inhibitor of nuclear factor κb
- ikk, iκb kinase
- il, interleukin
- imd, immune deficiency
- jnk, c-jun n-terminal kinase
- lmp1, latent membrane protein 1
- lps, lipopolysaccharide
- ltβr, lymphotoxin-β receptor
- map kinase, mitogen-activated protein kinase
- map 3-kinase, map kinase kinase kinase
- mef, mouse embryo fibroblast
- mek, map kinase/erk kinase
- mip, macrophage inflammatory protein
- nemo, nuclear factor κb essential modulator
- nf-κb, nuclear factor κb
- nik, nf-κb-inducing kinase
- pest region, polypeptide sequence enriched in proline (p), glutamic acid (e), serine (s) and threonine (t)
- pgrp-lc, peptidoglycan recognition protein lc
- rankl, receptor activator of nf-κb ligand
- rhd, rel homology domain
- scf, skp1/cul1/f-box
- th1, t-helper 1
- th2, t-helper 2
- tlr, toll-like receptor
- tnf, tumour necrosis factor
- tpl-2, tumour progression locus-2
- traf, tnf-receptor-associated factor
- tweak, tnf-like weak inducer of apoptosis
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Affiliation(s)
- Sören Beinke
- Division of Immune Cell Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
| | - Steven C. Ley
- Division of Immune Cell Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
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226
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Faccio R, Zou W, Colaianni G, Teitelbaum SL, Ross FP. High dose M-CSF partially rescues the Dap12-/- osteoclast phenotype. J Cell Biochem 2004; 90:871-83. [PMID: 14624447 DOI: 10.1002/jcb.10694] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Osteoclasts are macrophage derived cells and as such are subject to regulation by molecules impacting other members of the immune system. Dap12 is an adaptor protein expressed by NK cells and B and T lymphocytes. Dap12 also mediates maturation of myeloid cells and is expressed by osteoclasts which are dysfunctional in its absence. We find Dap12-/- osteoclast precursors fail to differentiate, in vitro, and the abnormality is partially rescued by high dose M-CSF. The relative paucity of osteoclast number, even in presence of high dose cytokine, is attended by dampened proliferation of precursor cells and their failure to normally migrate towards the osteoclast-recognized matrix protein, osteopontin. Furthermore, Dap12-/- osteoclasts generated in high dose M-CSF fail to normally organize their cytoskeleton. The incapacity of Dap12 null cells to undergo normal osteoclast differentiation is not due to blunted stimulation of major RANK ligand (RANKL) or M-CSF induced signaling pathways. On the other hand, when plated on osteopontin, Dap12-/- pre-osteoclasts do not activate the tyrosine kinase, Syk, which normally binds to the adaptor protein and transmits downstream signals. Attesting to the importance of the Dap12/Syk complex, Syk deficient macrophages do not undergo normal osteoclastogenesis. Furthermore, the same cells plated onto osteopontin, adhere poorly and fail to phosphorylate c-Src or Pyk2, two kinases central to organization of the osteoclast cytoskeleton.
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Affiliation(s)
- Roberta Faccio
- Washington University School of Medicine, St. Louis, Missouri 63110, USA
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227
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Durán A, Serrano M, Leitges M, Flores JM, Picard S, Brown JP, Moscat J, Diaz-Meco MT. The atypical PKC-interacting protein p62 is an important mediator of RANK-activated osteoclastogenesis. Dev Cell 2004; 6:303-9. [PMID: 14960283 DOI: 10.1016/s1534-5807(03)00403-9] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Revised: 12/04/2003] [Accepted: 12/11/2003] [Indexed: 11/16/2022]
Abstract
The atypical PKCs (aPKCs) have been implicated genetically in at least two independent signaling cascades that control NF-kappa B and cell polarity, through the interaction with the adapters p62 and Par-6, respectively. P62 binds TRAF6, which plays an essential role in osteoclastogenesis and bone remodeling. Recently, p62 mutations have been shown to be the cause of the 5q35-linked Paget's disease of bone, a genetic disorder characterized by aberrant osteoclastic activity. Here we show that p62, like TRAF6, is upregulated during RANK-L-induced osteoclastogenesis and that the genetic inactivation of p62 in mice leads to impaired osteoclastogenesis in vitro and in vivo, as well as inhibition of IKK activation and NF-kappa B nuclear translocation. In addition, RANK-L stimulation leads to the inducible formation of a ternary complex involving TRAF6, p62, and the aPKCs. These observations demonstrate that p62 is an important mediator during osteoclastogenesis and induced bone remodeling.
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Affiliation(s)
- Angeles Durán
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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