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Blangy A, Touaitahuata H, Cres G, Pawlak G. Cofilin activation during podosome belt formation in osteoclasts. PLoS One 2012; 7:e45909. [PMID: 23049890 PMCID: PMC3457939 DOI: 10.1371/journal.pone.0045909] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 08/23/2012] [Indexed: 12/02/2022] Open
Abstract
Podosomes are dynamic actin-based structures found constitutively in cells of monocytic origin such as macrophages, dendritic cells and osteoclasts. They have been involved in osteoclast cell adhesion, motility and matrix degradation, and all these functions rely on the ability of podosomes to form supra-molecular structures called podosome belts or sealing zones on mineralized substrates. Podosomes contain two distinct domains, an actin-rich core enriched in actin polymerization regulators, surrounded by a ring of signaling and plaque molecules. The organization of podosome arrays into belts is linked to actin dynamics. Cofilin is an actin-severing protein that is known to regulate cytoskeleton architecture and cell migration. Cofilin is present in lamellipodia and invadopodia where it regulates actin polymerization. In this report, we show that cofilin is a novel component of the podosome belt, the mature osteoclast adhesion structure. Time-course analysis demonstrated that cofilin is activated during primary osteoclast differentiation, at the time of podosome belt assembly. Immunofluorescence studies reveal a localization of active cofilin in the podosome core structure, whereas phosphorylated, inactive cofilin is concentrated in the podosome cloud. Pharmacological studies unraveled the role of a specific cofilin phosphatase to achieve cofilin activation during osteoclast differentiation. We ruled out the implication of PP1/PP2A and PTEN in this process, and rather provided evidence for the involvement of SSH1. In summary, our data involve cofilin as a regulator of podosome organization that is activated during osteoclast differentiation by a RANKL-mediated signaling pathway targeting the SSH1 phosphatase.
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Affiliation(s)
- Anne Blangy
- Centre de Recherche de Biochimie Macromoleculaire, Montpellier University, CNRS UMR 5237, Montpellier, France.
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Ray BJ, Thomas K, Huang CS, Gutknecht MF, Botchwey EA, Bouton AH. Regulation of osteoclast structure and function by FAK family kinases. J Leukoc Biol 2012; 92:1021-8. [PMID: 22941736 DOI: 10.1189/jlb.0512259] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Osteoclasts are highly specialized cells that resorb bone and contribute to bone remodeling. Diseases such as osteoporosis and osteolytic bone metastasis occur when osteoclast-mediated bone resorption takes place in the absence of concurrent bone synthesis. Considerable effort has been placed on identifying molecules that regulate the bone resorption activity of osteoclasts. To this end, we investigated unique and overlapping functions of members of the FAK family (FAK and Pyk2) in osteoclast functions. With the use of a conditional knockout mouse model, in which FAK is selectively targeted for deletion in osteoclast precursors (FAK(Δmyeloid)), we found that loss of FAK resulted in reduced bone resorption by osteoclasts in vitro, coincident with impaired signaling through the CSF-1R. However, bone architecture appeared normal in FAK(Δmyeloid) mice, suggesting that Pyk2 might functionally compensate for reduced FAK levels in vivo. This was supported by data showing that podosome adhesion structures, which are essential for bone degradation, were significantly more impaired in osteoclasts when FAK and Pyk2 were reduced than when either molecule was depleted individually. We conclude that FAK contributes to cytokine signaling and bone resorption in osteoclasts and partially compensates for the absence of Pyk2 to maintain proper adhesion structures in these cells.
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Affiliation(s)
- Brianne J Ray
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908, USA
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Goldberg SR, Georgiou J, Glogauer M, Grynpas MD. A 3D scanning confocal imaging method measures pit volume and captures the role of Rac in osteoclast function. Bone 2012; 51:145-52. [PMID: 22561898 DOI: 10.1016/j.bone.2012.04.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 04/05/2012] [Accepted: 04/19/2012] [Indexed: 01/09/2023]
Abstract
Modulation of Rho GTPases Rac1 and Rac2 impacts bone development, remodeling, and disease. In addition, GTPases are considered treatment targets for dysplastic and erosive bone diseases including Neurofibromatosis type 1. While it is important to understand the effects of Rac modulation on osteoclast function, two-dimensional resorption pit area measurements fall short in elucidating the volume aspect of bone resorption activity. Bone marrow from wild-type, Rac1 and Rac2 null mice was isolated from femora. Osteoclastogenesis was induced by adding M-CSF and RANKL in culture plates containing dentin slices and later stained with Picro Sirius Red to image resorption lacunae. Osteoclasts were also plated on glass cover slips and stained with phalloidin and DAPI to measure their surface area and the number of nuclei. Volumetric images were collected on a laser-scanning confocal system. Sirius Red confocal imaging provided an unambiguous, continuous definition of the pit boundary compared to reflected and transmitted light imaging. Rac1- and Rac2-deficient osteoclasts had fewer nuclei in comparison to wild-type counterparts. Rac1-deficient osteoclasts showed reduced resorption pit volume and surface area. Lacunae made by single Rac2 null osteoclasts had reduced volume but surprisingly surface area was unaffected. Surface area measures are deceiving since volume changed independently in resorption pits made by individual Rac2 null osteoclasts. Our innovative confocal imaging technique allows us to derive novel conclusions about Rac1 and Rac2 in osteoclast function. The data and method can be applied to study effects of genes and drugs including Rho GTPase modulators on osteoclast function and to develop pharmacotherapeutics to treat bone lytic disorders.
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Affiliation(s)
- Stephanie R Goldberg
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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Buchwald ZS, Kiesel JR, DiPaolo R, Pagadala MS, Aurora R. Osteoclast activated FoxP3+ CD8+ T-cells suppress bone resorption in vitro. PLoS One 2012; 7:e38199. [PMID: 22701612 PMCID: PMC3368916 DOI: 10.1371/journal.pone.0038199] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 05/03/2012] [Indexed: 12/17/2022] Open
Abstract
Background Osteoclasts are the body’s sole bone resorbing cells. Cytokines produced by pro-inflammatory effector T-cells (TEFF) increase bone resorption by osteoclasts. Prolonged exposure to the TEFF produced cytokines leads to bone erosion diseases such as osteoporosis and rheumatoid arthritis. The crosstalk between T-cells and osteoclasts has been termed osteoimmunology. We have previously shown that under non-inflammatory conditions, murine osteoclasts can recruit naïve CD8 T-cells and activate these T-cells to induce CD25 and FoxP3 (TcREG). The activation of CD8 T-cells by osteoclasts also induced the cytokines IL-2, IL-6, IL-10 and IFN-γ. Individually, these cytokines can activate or suppress osteoclast resorption. Principal Findings To determine the net effect of TcREG on osteoclast activity we used a number of in vitro assays. We found that TcREG can potently and directly suppress bone resorption by osteoclasts. TcREG could suppress osteoclast differentiation and resorption by mature osteoclasts, but did not affect their survival. Additionally, we showed that TcREG suppress cytoskeletal reorganization in mature osteoclasts. Whereas induction of TcREG by osteoclasts is antigen-dependent, suppression of osteoclasts by TcREG does not require antigen or re-stimulation. We demonstrated that antibody blockade of IL-6, IL-10 or IFN-γ relieved suppression. The suppression did not require direct contact between the TcREG and osteoclasts. Significance We have determined that osteoclast-induced TcREG can suppress osteoclast activity, forming a negative feedback system. As the CD8 T-cells are activated in the absence of inflammatory signals, these observations suggest that this regulatory loop may play a role in regulating skeletal homeostasis. Our results provide the first documentation of suppression of osteoclast activity by CD8 regulatory T-cells and thus, extend the purview of osteoimmunology.
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Affiliation(s)
- Zachary S. Buchwald
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Jennifer R. Kiesel
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Richard DiPaolo
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Meghana S. Pagadala
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Rajeev Aurora
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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55
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Eleniste PP, Du L, Shivanna M, Bruzzaniti A. Dynamin and PTP-PEST cooperatively regulate Pyk2 dephosphorylation in osteoclasts. Int J Biochem Cell Biol 2012; 44:790-800. [PMID: 22342188 DOI: 10.1016/j.biocel.2012.01.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 01/17/2012] [Accepted: 01/30/2012] [Indexed: 11/18/2022]
Abstract
Bone loss is caused by the dysregulated activity of osteoclasts which degrade the extracellular bone matrix. The tyrosine kinase Pyk2 is highly expressed in osteoclasts, and mice lacking Pyk2 exhibit an increase in bone mass, in part due to impairment of osteoclast function. Pyk2 is activated by phosphorylation at Y402 following integrin activation, but the mechanisms leading to Pyk2 dephosphorylation are poorly understood. In the current study, we examined the mechanism of action of the dynamin GTPase on Pyk2 dephosphorylation. Our studies reveal a novel mechanism for the interaction of Pyk2 with dynamin, which involves the binding of Pyk2's FERM domain with dynamin's plextrin homology domain. In addition, we demonstrate that the dephosphorylation of Pyk2 requires dynamin's GTPase activity and is mediated by the tyrosine phosphatase PTP-PEST. The dephosphorylation of Pyk2 by dynamin and PTP-PEST may be critical for terminating outside-in integrin signaling, and for stabilizing cytoskeletal reorganization during osteoclast bone resorption.
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Affiliation(s)
- Pierre P Eleniste
- Department of Oral Biology, Indiana University School of Dentistry, Indianapolis, IN 46202, USA.
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Abstract
Vertebrates evolved elaborating a structure made up of more than 200 bones and cartilages articulated with one another to form the skeleton, through which locomotion, organ protection, lodging of hematopoiesis, and mineral homeostasis are allowed. Skeletogenesis starts at the fetal stage, along with marrow hematopoiesis, and evolves postnatally through modeling and remodeling processes that permit skeletal mass buildup. Preservation of skeletal mass is then implemented by balanced remodeling, which ensures continuous renovation of the tissue to allow its mechanical, structural, and metabolic properties to remain unaltered until ageing or diseases disrupt this equilibrium. Skeletal homeostasis is fulfilled by specialized bone cells in association with systemic and local regulators. Herein I review landmark discoveries that shed light on the intricate mesh connecting bone cells among themselves and with other systems, thus representing the cellular basis of normal and abnormal bone development and homeostasis.
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Affiliation(s)
- Anna Teti
- Department of Experimental Medicine, University of L'Aquila, Via Vetoio-Coppito 2, 67100, L'Aquila, Italy.
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Motskin M, Müller KH, Genoud C, Monteith AG, Skepper JN. The sequestration of hydroxyapatite nanoparticles by human monocyte-macrophages in a compartment that allows free diffusion with the extracellular environment. Biomaterials 2011; 32:9470-82. [PMID: 21889202 DOI: 10.1016/j.biomaterials.2011.08.060] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 08/18/2011] [Indexed: 11/30/2022]
Abstract
Calcium phosphate and hydroxyapatite nanoparticles are extensively researched for medical applications, including bone implant materials, DNA and SiRNA delivery vectors and slow release vaccines. Elucidating the mechanisms by which cells internalize nanoparticles is fundamental for their long-term exploitation. In this study, we demonstrate that hydrophilic hydroxyapatite nanoparticles are sequestered within a specialized compartment called SCC (surface-connected compartment). This membrane-bound compartment is an elaborate labyrinth-like structure directly connected to the extracellular space. This continuity is demonstrated by in vivo 2-photon microscopy of ionic calcium using both cell-permeable and cell-impermeable dyes and by 3-D reconstructions from serial block-face SEM of fixed cells. Previously, this compartment was thought to be initiated specifically by exposure of macrophages to hydrophobic nanoparticles. However, we show that the SCC can be triggered by a much wider range of nanoparticles. Furthermore, we demonstrate its formation in A549 human lung epithelial cells, which are considerably less phagocytic than macrophages. EDX shows that extensive amounts of hydroxyapatite nanoparticles can be sequestered in this manner. We propose that SCC formation may be a means to remove large amounts of foreign material from the extracellular space, followed by slow degradation, may be to avoid excessive damage to surrounding cells or tissues.
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Affiliation(s)
- Michael Motskin
- Multi-Imaging Centre, Dept. of Physiology, Development and Neuroscience, Anatomy Building, Cambridge University, Cambridge CB2 3DY, UK
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Tsutsumi K, Matsuda M, Kotani M, Mizokami A, Murakami A, Takahashi I, Terada Y, Kanematsu T, Fukami K, Takenawa T, Jimi E, Hirata M. Involvement of PRIP, phospholipase C-related, but catalytically inactive protein, in bone formation. J Biol Chem 2011; 286:31032-31042. [PMID: 21757756 PMCID: PMC3162462 DOI: 10.1074/jbc.m111.235903] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 07/08/2011] [Indexed: 11/06/2022] Open
Abstract
PRIP (phospholipase C-related, but catalytically inactive protein) is a novel protein isolated in this laboratory. PRIP-deficient mice showed increased serum gonadotropins, but decreased gonadal steroid hormones. This imbalance was similar to that for the cause of bone disease, such as osteoporosis. In the present study, therefore, we analyzed mutant mice with special reference to the bone property. We first performed three-dimensional analysis of the femur of female mice. The bone mineral density and trabecular bone volume were higher in mutant mice. We further performed histomorphometrical assay of bone formation parameters: bone formation rate, mineral apposition rate, osteoid thickness, and osteoblast number were up-regulated in the mutant, indicating that increased bone mass is caused by the enhancement of bone formation ability. We then cultured primary cells isolated from calvaria prepared from both genotypes. In mutant mice, osteoblast differentiation, as assessed by alkaline phosphatase activity and the expression of osteoblast differentiation marker genes, was enhanced. Moreover, we analyzed the phosphorylation of Smad1/5/8 in response to bone morphogenetic protein, with longer phosphorylation in the mutant. These results indicate that PRIP is implicated in the negative regulation of bone formation.
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Affiliation(s)
- Koshiro Tsutsumi
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan; Division of Fixed Prosthodontics, Kyushu University, Fukuoka 812-8582, Japan
| | - Miho Matsuda
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan
| | - Miho Kotani
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan; Division of Orthodontics, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Akiko Mizokami
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan
| | - Ayako Murakami
- Division of Orthodontics, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Ichiro Takahashi
- Division of Orthodontics, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Yoshihiro Terada
- Division of Fixed Prosthodontics, Kyushu University, Fukuoka 812-8582, Japan
| | - Takashi Kanematsu
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan
| | - Kiyoko Fukami
- Laboratory of Genome and Biosignal, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan
| | - Tadaomi Takenawa
- Division of Lipid Biochemistry, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan
| | - Eijiro Jimi
- Department of Molecular Signaling and Biochemistry, Kyushu Dental College, Kitakyushu 803-8580, Japan
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Kyushu University, Fukuoka 812-8582, Japan.
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Crockett JC, Rogers MJ, Coxon FP, Hocking LJ, Helfrich MH. Bone remodelling at a glance. J Cell Sci 2011; 124:991-8. [PMID: 21402872 DOI: 10.1242/jcs.063032] [Citation(s) in RCA: 312] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Julie C Crockett
- Musculoskeletal Research Programme, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
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Abstract
Since the discovery that deletion of the NF-κB subunits p50 and p52 causes osteopetrosis in mice, there has been considerable interest in the role of NF-κB signaling in bone. NF-κB controls the differentiation or activity of the major skeletal cell types - osteoclasts, osteoblasts, osteocytes and chondrocytes. However, with five NF-κB subunits and two distinct activation pathways, not all NF-κB signals lead to the same physiologic responses. In this review, we will describe the roles of various NF-κB proteins in basal bone homeostasis and disease states, and explore how NF-κB inhibition might be utilized therapeutically.
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Affiliation(s)
- Deborah Veis Novack
- Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, St Louis, MO, USA.
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Yang C, McCoy K, Davis JL, Schmidt-Supprian M, Sasaki Y, Faccio R, Novack DV. NIK stabilization in osteoclasts results in osteoporosis and enhanced inflammatory osteolysis. PLoS One 2010; 5:e15383. [PMID: 21151480 PMCID: PMC2975662 DOI: 10.1371/journal.pone.0015383] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 08/31/2010] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Maintenance of healthy bone requires the balanced activities of osteoclasts (OCs), which resorb bone, and osteoblasts, which build bone. Disproportionate action of OCs is responsible for the bone loss associated with postmenopausal osteoporosis and rheumatoid arthritis. NF-κB inducing kinase (NIK) controls activation of the alternative NF-κB pathway, a critical pathway for OC differentiation. Under basal conditions, TRAF3-mediated NIK degradation prevents downstream signaling, and disruption of the NIK:TRAF3 interaction stabilizes NIK leading to constitutive activation of the alternative NF-κB pathway. METHODOLOGY/PRINCIPAL FINDINGS Using transgenic mice with OC-lineage expression of NIK lacking its TRAF3 binding domain (NT3), we now find that alternative NF-κB activation enhances not only OC differentiation but also OC function. Activating NT3 with either lysozyme M Cre or cathepsinK Cre causes high turnover osteoporosis with increased activity of OCs and osteoblasts. In vitro, NT3-expressing precursors form OCs more quickly and at lower doses of RANKL. When cultured on bone, they exhibit larger actin rings and increased resorptive activity. OC-specific NT3 transgenic mice also have an exaggerated osteolytic response to the serum transfer model of arthritis. CONCLUSIONS Constitutive activation of NIK drives enhanced osteoclastogenesis and bone resorption, both in basal conditions and in response to inflammatory stimuli.
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Affiliation(s)
- Chang Yang
- Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kathleen McCoy
- Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Jennifer L. Davis
- Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | | | | | - Roberta Faccio
- Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Deborah Veis Novack
- Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Pathology, Washington University School of Medicine, St. Louis, Missouri, United States of America
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