FHL2 inhibits the activated osteoclast in a TRAF6-dependent manner.

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.

[1]  Steven W. Martin,et al.  A Single‐Dose Placebo‐Controlled Study of AMG 162, a Fully Human Monoclonal Antibody to RANKL, in Postmenopausal Women , 2005, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[2]  Osami Kanagawa,et al.  NF-κB–inducing kinase controls lymphocyte and osteoclast activities in inflammatory arthritis , 2005 .

[3]  Yu Wei,et al.  Interaction and Functional Cooperation between the LIM Protein FHL2, CBP/p300, and β-Catenin , 2004, Molecular and Cellular Biology.

[4]  M. Beckerle,et al.  The LIM domain: from the cytoskeleton to the nucleus , 2004, Nature Reviews Molecular Cell Biology.

[5]  Matthew J. Silva,et al.  Marrow Stromal Cells and Osteoclast Precursors Differentially Contribute to TNF-α-Induced Osteoclastogenesis In Vivo1 , 2004, The Journal of Immunology.

[6]  Michael W.-H. Wang,et al.  The HIV protease inhibitor ritonavir blocks osteoclastogenesis and function by impairing RANKL-induced signaling. , 2004, The Journal of clinical investigation.

[7]  R. Schüle,et al.  The LIM-only Proteins FHL2 and FHL3 Interact with α- and β-Subunits of the Muscle α7β1 Integrin Receptor* , 2004, Journal of Biological Chemistry.

[8]  Colin R Dunstan,et al.  A Single‐Dose Placebo‐Controlled Study of AMG 162, a Fully Human Monoclonal Antibody to RANKL, in Postmenopausal Women , 2004, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[9]  B. Aggarwal,et al.  Evidence That Receptor Activator of Nuclear Factor (NF)-κB Ligand Can Suppress Cell Proliferation and Induce Apoptosis through Activation of a NF-κB-independent and TRAF6-dependent Mechanism* , 2004, Journal of Biological Chemistry.

[10]  Hao Wu,et al.  TRAF6, a molecular bridge spanning adaptive immunity, innate immunity and osteoimmunology , 2003, BioEssays : news and reviews in molecular, cellular and developmental biology.

[11]  D. Goeddel,et al.  The IκB Function of NF-κB2 p100 Controls Stimulated Osteoclastogenesis , 2003, The Journal of experimental medicine.

[12]  P. Sassone-Corsi,et al.  The LIM-only protein FHL2 is a serum-inducible transcriptional coactivator of AP-1 , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[13]  A. Zallone,et al.  c-Fms and the αvβ3 integrin collaborate during osteoclast differentiation , 2003 .

[14]  M. Buendia,et al.  Identification of the LIM Protein FHL2 as a Coactivator of β-Catenin* , 2003, The Journal of Biological Chemistry.

[15]  W. Dougall,et al.  A RANK/TRAF6-dependent Signal Transduction Pathway Is Essential for Osteoclast Cytoskeletal Organization and Resorptive Function* , 2002, The Journal of Biological Chemistry.

[16]  J. Licht,et al.  The LIM-only Protein DRAL/FHL2 Interacts with and Is a Corepressor for the Promyelocytic Leukemia Zinc Finger Protein* , 2002, The Journal of Biological Chemistry.

[17]  Hao Wu,et al.  Distinct molecular mechanism for initiating TRAF6 signalling , 2002, Nature.

[18]  A. Dierich,et al.  Impaired neural tube closure, axial skeleton malformations, and tracheal ring disruption in TRAF4-deficient mice , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[19]  A. Bosserhoff,et al.  The transcriptional coactivator FHL2 transmits Rho signals from the cell membrane into the nucleus , 2002, The EMBO journal.

[20]  V. Parikka,et al.  Downregulation of Small GTPase Rab7 Impairs Osteoclast Polarization and Bone Resorption* 210 , 2001, The Journal of Biological Chemistry.

[21]  J. Pober,et al.  Tumor necrosis factor receptor-associated factors (TRAFs) , 2001, Oncogene.

[22]  C. Nelson,et al.  Crystal structure of the TRANCE/RANKL cytokine reveals determinants of receptor-ligand specificity. , 2001, The Journal of clinical investigation.

[23]  Y. Kadono,et al.  Segregation of TRAF6‐mediated signaling pathways clarifies its role in osteoclastogenesis , 2001, The EMBO journal.

[24]  P. Sassone-Corsi,et al.  A Family of LIM-Only Transcriptional Coactivators: Tissue-Specific Expression and Selective Activation of CREB and CREM , 2000, Molecular and Cellular Biology.

[25]  J. Ross,et al.  FHL2 (SLIM3) Is Not Essential for Cardiac Development and Function , 2000, Molecular and Cellular Biology.

[26]  S. Teitelbaum,et al.  Bone resorption by osteoclasts. , 2000, Science.

[27]  M. Morgan,et al.  The structure of the human LIM protein ACT gene and its expression in tumor cell lines. , 2000, Biochemical and biophysical research communications.

[28]  Qiang Zhou,et al.  Expression patterns of FHL/SLIM family members suggest important functional roles in skeletal muscle and cardiovascular system , 2000, Mechanisms of Development.

[29]  I. Bach.  The LIM domain: regulation by association , 2000, Mechanisms of Development.

[30]  R. Hynes,et al.  Mice lacking beta3 integrins are osteosclerotic because of dysfunctional osteoclasts. , 2000, The Journal of clinical investigation.

[31]  R. Schüle,et al.  FHL2, a novel tissue‐specific coactivator of the androgen receptor , 2000, The EMBO journal.

[32]  J. Inoue,et al.  Tumor necrosis factor receptor-associated factor (TRAF) family: adapter proteins that mediate cytokine signaling. , 2000, Experimental cell research.

[33]  David M. Rothwarf,et al.  The NF-κB Activation Pathway: A Paradigm in Information Transfer from Membrane to Nucleus , 1999, Science's STKE.

[34]  W. Dougall,et al.  RANK is essential for osteoclast and lymph node development. , 1999, Genes & development.

[35]  Sakae Tanaka,et al.  Severe osteopetrosis, defective interleukin‐1 signalling and lymph node organogenesis in TRAF6‐deficient mice , 1999, Genes to cells : devoted to molecular & cellular mechanisms.

[36]  S. Morony,et al.  TRAF6 deficiency results in osteopetrosis and defective interleukin-1, CD40, and LPS signaling. , 1999, Genes & development.

[37]  C. Thompson,et al.  Tumor necrosis factor receptor-associated factors (TRAFs)--a family of adapter proteins that regulates life and death. , 1998, Genes & development.

[38]  D. Lacey,et al.  Osteoprotegerin Ligand Is a Cytokine that Regulates Osteoclast Differentiation and Activation , 1998, Cell.

[39]  K P Fung,et al.  Molecular cloning and characterization of FHL2, a novel LIM domain protein preferentially expressed in human heart. , 1998, Gene.

[40]  J. J. Breen,et al.  LIM domains: multiple roles as adapters and functional modifiers in protein interactions. , 1998, Trends in genetics : TIG.

[41]  Zhaodan Cao,et al.  TRAF6 is a signal transducer for interleukin-1 , 1996, Nature.

[42]  J. Koziol,et al.  Integrin alphavbeta3 is expressed in selected microvessels after focal cerebral ischemia. , 1996, The American journal of pathology.

[43]  D. Cheresh.  Human endothelial cells synthesize and express an Arg-Gly-Asp-directed adhesion receptor involved in attachment to fibrinogen and von Willebrand factor. , 1987, Proceedings of the National Academy of Sciences of the United States of America.

[44]  D. Stupack,et al.  Integrins and angiogenesis. , 2004, Current topics in developmental biology.

[45]  Matthew J. Silva,et al.  SHIP-deficient mice are severely osteoporotic due to increased numbers of hyper-resorptive osteoclasts , 2002, Nature Medicine.