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Castro-Gomes T, Corrotte M, Tam C, Andrews NW. Plasma Membrane Repair Is Regulated Extracellularly by Proteases Released from Lysosomes. PLoS One 2016; 11:e0152583. [PMID: 27028538 PMCID: PMC4814109 DOI: 10.1371/journal.pone.0152583] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/16/2016] [Indexed: 12/28/2022] Open
Abstract
Eukaryotic cells rapidly repair wounds on their plasma membrane. Resealing is Ca2+-dependent, and involves exocytosis of lysosomes followed by massive endocytosis. Extracellular activity of the lysosomal enzyme acid sphingomyelinase was previously shown to promote endocytosis and wound removal. However, whether lysosomal proteases released during cell injury participate in resealing is unknown. Here we show that lysosomal proteases regulate plasma membrane repair. Extracellular proteolysis is detected shortly after cell wounding, and inhibition of this process blocks repair. Conversely, surface protein degradation facilitates plasma membrane resealing. The abundant lysosomal cysteine proteases cathepsin B and L, known to proteolytically remodel the extracellular matrix, are rapidly released upon cell injury and are required for efficient plasma membrane repair. In contrast, inhibition of aspartyl proteases or RNAi-mediated silencing of the lysosomal aspartyl protease cathepsin D enhances resealing, an effect associated with the accumulation of active acid sphingomyelinase on the cell surface. Thus, secreted lysosomal cysteine proteases may promote repair by facilitating membrane access of lysosomal acid sphingomyelinase, which promotes wound removal and is subsequently downregulated extracellularly by a process involving cathepsin D.
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Affiliation(s)
- Thiago Castro-Gomes
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, 20742, United States of America
| | - Matthias Corrotte
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, 20742, United States of America
| | - Christina Tam
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, 20742, United States of America
| | - Norma W. Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, 20742, United States of America
- * E-mail:
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Synergistic effects of hypoxia and morphogenetic factors on early chondrogenic commitment of human embryonic stem cells in embryoid body culture. Stem Cell Rev Rep 2016; 11:228-41. [PMID: 25618295 DOI: 10.1007/s12015-015-9584-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Derivation of articular chondrocytes from human stem cells would advance our current understanding of chondrogenesis, and accelerate development of new stem cell therapies for cartilage repair. Chondrogenic differentiation of human embryonic stem cells (hESCs) has been studied using supplemental and cell-secreted morphogenetic factors. The use of bioreactors enabled insights into the effects of physical forces and controlled oxygen tension. In this study, we investigated the interactive effects of controlled variation of oxygen tension and chondrocyte-secreted morphogenetic factors on chondrogenic differentiation of hESCs in the embryoid body format (hESC-EB). Transient hypoxic culture (2 weeks at 5 % O2 followed by 1 week at 21 % O2) of hESC-EBs in medium conditioned with primary chondrocytes up-regulated the expression of SOX9 and suppressed pluripotent markers OCT4 and NANOG. Pellets derived from these cells showed significant up-regulation of chondrogenic genes (SOX9, COL2A1, ACAN) and enhanced production of cartilaginous matrix (collagen type II and proteoglycan) as compared to the pellets from hESC-EBs cultured under normoxic conditions. Gene expression profiles corresponded to those associated with native cartilage development, with early expression of N-cadherin (indicator of cell condensation) and late expression of aggrecan (ACAN, indicator of proteoglycan production). When implanted into highly vascularized subcutaneous area in immunocompromised mice for 4 weeks, pellets remained phenotypically stable and consisted of cartilaginous extracellular matrix (ECM), without evidence of dedifferentiation or teratoma formation. Based on these results, we propose that chondrogenesis in hESC can be synergistically enhanced by a control of oxygen tension and morphogenetic factors secreted by chondrocytes.
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Zhao C, Sun W, Zhang P, Ling S, Li Y, Zhao D, Peng J, Wang A, Li Q, Song J, Wang C, Xu X, Xu Z, Zhong G, Han B, Chang YZ, Li Y. miR-214 promotes osteoclastogenesis by targeting Pten/PI3k/Akt pathway. RNA Biol 2015; 12:343-53. [PMID: 25826666 DOI: 10.1080/15476286.2015.1017205] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
microRNA is necessary for osteoclast differentiation, function and survival. It has been reported that miR-199/214 cluster plays important roles in vertebrate skeletal development and miR-214 inhibits osteoblast function by targeting ATF4. Here, we show that miR-214 is up-regulated during osteoclastogenesis from bone marrow monocytes (BMMs) with macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) induction, which indicates that miR-214 plays a critical role in osteoclast differentiation. Overexpression of miR-214 in BMMs promotes osteoclastogenesis, whereas inhibition of miR-214 attenuates it. We further find that miR-214 functions through PI3K/Akt pathway by targeting phosphatase and tensin homolog (Pten). In vivo, osteoclast specific miR-214 transgenic mice (OC-TG214) exhibit down-regulated Pten levels, increased osteoclast activity, and reduced bone mineral density. These results reveal a crucial role of miR-214 in the differentiation of osteoclasts, which will provide a potential therapeutic target for osteoporosis.
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Key Words
- BMD, bone mineral density
- BMMs, bone marrow monocytes
- BV/TV, ratio of bone volume to tissue volume
- Dnm3os, Dnm3 opposite strand
- M-CSF, macrophage colony stimulating factor
- NFATc1, nuclear factor of activated T-cells cytoplasmic
- OC-TG214, osteoclast specific miR-214 transgenic mice
- PI 3-kinase
- PTEN
- Pten, phosphatase and tensin homolog
- RANKL, receptor activator of nuclear factor-κB ligand
- TRAP, tartrate-resistant acid phosphatase
- Tb.Sp, trabecular spacing
- WT, wild-type
- miRNA
- micro CT, Micro computed tomography
- osteoclast
- osteoporosis
- qRT-PCR, quantitative real-time PCR
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Affiliation(s)
- Chenyang Zhao
- a From Key Laboratory of Molecular and Cellular Biology of Ministry of Education; College of Life Science; Hebei Normal University ; Shijiazhuang , China
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54
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Sancho-Knapik S, Guillén N, Osada J. Cloning and expression of hepatic synaptotagmin 1 in mouse. Gene 2015; 562:236-43. [PMID: 25735570 DOI: 10.1016/j.gene.2015.02.074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 02/17/2015] [Accepted: 02/27/2015] [Indexed: 11/29/2022]
Abstract
Mouse hepatic synaptotagmin 1 (SYT1) cDNA was cloned, characterized and compared to the brain one. The hepatic transcript was 1807 bp in length, smaller than the brain, and only encoded by 9 of 11 gene exons. In this regard, 5'-and 3'-untranslated regions were 66 and 476 bp, respectively; the open reading frame of 1266 bp codified for a protein of 421 amino acids, identical to the brain, with a predicted molecular mass of 47.4 kDa and highly conserved across different species. Immunoblotting of protein showed two isoforms of higher molecular masses than the theoretical prediction based on amino acid sequence suggesting posttranslational modifications. Subcellular distribution of protein isoforms corresponded to plasma membrane, lysosomes and microsomes and was identical between the brain and liver. Nonetheless, the highest molecular weight isoform was smaller in the liver, irrespective of subcellular location. Quantitative mRNA tissue distribution showed that it was widely expressed and that the highest values corresponded to the brain, followed by the liver, spleen, abdominal fat, intestine and skeletal muscle. These findings indicate tissue-specific splicing of the gene and posttranslational modification and the variation in expression in the different tissues might suggest a different requirement of SYT1 for the specific function in each organ.
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Affiliation(s)
- Sara Sancho-Knapik
- Departamento Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón (IIS), Universidad de Zaragoza, Spain
| | - Natalia Guillén
- Departamento de Toxicología, Facultad de Veterinaria, Universidad de Zaragoza, Spain
| | - Jesús Osada
- Departamento Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón (IIS), Universidad de Zaragoza, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Spain.
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55
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Sung BH, Weaver AM. Regulation of lysosomal secretion by cortactin drives fibronectin deposition and cell motility. BIOARCHITECTURE 2014; 1:257-260. [PMID: 22545176 PMCID: PMC3337126 DOI: 10.4161/bioa.1.6.19197] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Directional cellular movement is required for various organismal processes, including immune defense and cancer metastasis. Proper navigation of migrating cells involves responding to a complex set of extracellular cues, including diffusible chemical signals and physical structural information. In tissues, conflicting gradients and signals may require cells to not only respond to the environment but also modulate it for efficient adhesion formation and directional cell motility. Recently, we found that cells endocytose fibronectin (FN) and resecrete it from a late endosomal/lysosomal (LE/Lys) compartment to provide an autocrine extracellular matrix (ECM) substrate for cell motility. Branched actin assembly regulated by cortactin was required for trafficking of FN-containing vesicles from LE/Lys to the cell surface. These findings suggest a model in which migrating cells use lysosomal secretion as a versatile mechanism to modulate the ECM environment, promote adhesion assembly and enhance directional migration.
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56
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Role of vesicular trafficking in skeletal dynamics. Curr Opin Pharmacol 2014; 16:7-14. [PMID: 24566133 DOI: 10.1016/j.coph.2014.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 01/27/2014] [Indexed: 01/06/2023]
Abstract
Vesicular trafficking is critical for the function of bone cells, exemplified by bone diseases such as osteopetrosis, which frequently results from defects in this process. Recent work has further dissected the role of the endolysosomal system in both bone formation by osteoblasts and bone resorption by osteoclasts. This pathway also plays an important role in the communication between these and other cells in bone, through trafficking and degradation of growth factors and their receptors, and microvesicle release. In addition, a crucial role for autophagy in bone remodelling and bone disease is beginning to emerge. These insights into the molecular control of bone remodelling raise the possibility of developing novel therapeutics for bone diseases designed to target specific aspects of this process.
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57
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Lacombe J, Karsenty G, Ferron M. Regulation of lysosome biogenesis and functions in osteoclasts. Cell Cycle 2013; 12:2744-52. [PMID: 23966172 DOI: 10.4161/cc.25825] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In order to resorb the mineralized bone extracellular matrix, the osteoclast relies on the generation of a resorption lacuna characterized by the presence of specific proteases and a low pH. Hence, bone resorption by osteoclasts is highly dependent on lysosomes, the organelles specialized in intra- and extracellular material degradation. This is best illustrated by the fact that multiple forms of human osteopetrosis are caused by mutations in genes encoding for lysosomal proteins. Yet, until recently, the molecular mechanisms regulating lysosomal biogenesis and function in osteoclasts were poorly understood. Here we review the latest developments in the study of lysosomal biogenesis and function in osteoclasts with an emphasis on the transcriptional control of these processes.
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Affiliation(s)
- Julie Lacombe
- Institut de Recherches Cliniques de Montréal; Montréal, Québec, Canada
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58
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Boyce BF. Advances in osteoclast biology reveal potential new drug targets and new roles for osteoclasts. J Bone Miner Res 2013; 28:711-22. [PMID: 23436579 PMCID: PMC3613781 DOI: 10.1002/jbmr.1885] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 01/22/2013] [Accepted: 01/28/2013] [Indexed: 01/06/2023]
Abstract
Osteoclasts are multinucleated myeloid lineage cells formed in response to macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL) by fusion of bone marrow-derived precursors that circulate in the blood and are attracted to sites of bone resorption in response to factors, such as sphingosine-1 phosphate signaling. Major advances in understanding of the molecular mechanisms regulating osteoclast functions have been made in the past 20 years, mainly from mouse and human genetic studies. These have revealed that osteoclasts express and respond to proinflammatory and anti-inflammatory cytokines. Some of these cytokines activate NF-κB and nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) signaling to induce osteoclast formation and activity and also regulate communication with neighboring cells through signaling proteins, including ephrins and semaphorins. Osteoclasts also positively and negatively regulate immune responses and osteoblastic bone formation. These advances have led to development of new inhibitors of bone resorption that are in clinical use or in clinical trials; and more should follow, based on these advances. This article reviews current understanding of how bone resorption is regulated both positively and negatively in normal and pathologic states.
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Affiliation(s)
- Brendan F Boyce
- Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA.
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59
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Feng X, Teitelbaum SL. Osteoclasts: New Insights. Bone Res 2013; 1:11-26. [PMID: 26273491 DOI: 10.4248/br201301003] [Citation(s) in RCA: 330] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 01/19/2013] [Indexed: 11/10/2022] Open
Abstract
Osteoclasts, the bone-resorbing cells, play a pivotal role in skeletal development and adult bone remodeling. They also participate in the pathogenesis of various bone disorders. Osteoclasts differentiate from cells of the monocyte/macrophage lineage upon stimulation of two essential factors, the monocyte/macrophage colony stimulating factor (M-CSF) and receptor activation of NF-κB ligand (RANKL). M-CSF binds to its receptor c-Fms to activate distinct signaling pathways to stimulate the proliferation and survival of osteoclast precursors and the mature cell. RANKL, however, is the primary osteoclast differentiation factor, and promotes osteoclast differentiation mainly through controlling gene expression by activating its receptor, RANK. Osteoclast function depends on polarization of the cell, induced by integrin αvβ3, to form the resorptive machinery characterized by the attachment to the bone matrix and the formation of the bone-apposed ruffled border. Recent studies have provided new insights into the mechanism of osteoclast differentiation and bone resorption. In particular, c-Fms and RANK signaling have been shown to regulate bone resorption by cross-talking with those activated by integrin αvβ3. This review discusses new advances in the understanding of the mechanisms of osteoclast differentiation and function.
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Affiliation(s)
- Xu Feng
- Department of Pathology, The University of Alabama at Birmingham , Birmingham, Alabama 35294, USA
| | - Steven L Teitelbaum
- Department of Pathology and Immunology, Washington University School of Medicine , St. Louis, Missouri 63110, USA
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60
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Zhu T, Chappel JC, Hsu FF, Turk J, Aurora R, Hyrc K, De Camilli P, Broekelmann TJ, Mecham RP, Teitelbaum SL, Zou W. Type I phosphotidylinosotol 4-phosphate 5-kinase γ regulates osteoclasts in a bifunctional manner. J Biol Chem 2013; 288:5268-77. [PMID: 23300084 PMCID: PMC3581369 DOI: 10.1074/jbc.m112.446054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Indexed: 12/22/2022] Open
Abstract
Type 1 phosphotidylinosotol-4 phosphate 5 kinase γ (PIP5KIγ) is central to generation of phosphotidylinosotol (4,5)P(2) (PI(4,5)P(2)). PIP5KIγ also participates in cytoskeletal organization by delivering talin to integrins, thereby enhancing their ligand binding capacity. As the cytoskeleton is pivotal to osteoclast function, we hypothesized that absence of PIP5KIγ would compromise their resorptive capacity. Absence of the kinase diminishes PI(4,5) abundance and desensitizes precursors to RANK ligand-stimulated differentiation. Thus, PIP5KIγ(-/-) osteoclasts are reduced in number in vitro and confirm physiological relevance in vivo. Despite reduced numbers, PIP5KIγ(-/-) osteoclasts surprisingly have normal cytoskeletons and effectively resorb bone. PIP5KIγ overexpression, which increases PI(4,5)P(2), also delays osteoclast differentiation and reduces cell number but in contrast to cells lacking the kinase, its excess disrupts the cytoskeleton. The cytoskeleton-disruptive effects of excess PIP5KIγ reflect its kinase activity and are independent of talin recognition. The combined arrested differentiation and disorganized cytoskeleton of PIP5KIγ-transduced osteoclasts compromises bone resorption. Thus, optimal PIP5KIγ and PI(4,5)P(2) expression, by osteoclasts, are essential for skeletal homeostasis.
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Affiliation(s)
| | | | | | | | - Rajeev Aurora
- the Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, St. Louis, Missouri 63104, and
| | - Krzysztof Hyrc
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri 63110
| | - Pietro De Camilli
- the Department of Cell Biology and Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06520
| | | | | | | | - Wei Zou
- From the Department of Pathology and Immunology
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61
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Subramani S, Malhotra V. Non-autophagic roles of autophagy-related proteins. EMBO Rep 2013; 14:143-51. [PMID: 23337627 PMCID: PMC3566844 DOI: 10.1038/embor.2012.220] [Citation(s) in RCA: 204] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 12/10/2012] [Indexed: 01/10/2023] Open
Abstract
Autophagy and autophagy-related processes are fundamentally important in human health and disease. These processes are viewed primarily as cellular degradative pathways that recycle macromolecules and dysfunctional or redundant organelles into amino acids, sugars and lipids, especially during starvation. However, the ubiquitin-like autophagy proteins and other components of the autophagic machinery additionally participate in cellular reprogramming. We highlight these non-autophagic roles of autophagy proteins with the aim of drawing attention to this growing, but unexplored, research topic. We focus on the non-autophagic functions of autophagy proteins in cell survival and apoptosis, modulation of cellular traffic, protein secretion, cell signalling, transcription, translation and membrane reorganization.
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Affiliation(s)
- Suresh Subramani
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, California 92093-0322, USA.
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62
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Lotinun S, Kiviranta R, Matsubara T, Alzate JA, Neff L, Lüth A, Koskivirta I, Kleuser B, Vacher J, Vuorio E, Horne WC, Baron R. Osteoclast-specific cathepsin K deletion stimulates S1P-dependent bone formation. J Clin Invest 2013; 123:666-81. [PMID: 23321671 DOI: 10.1172/jci64840] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 11/15/2012] [Indexed: 12/21/2022] Open
Abstract
Cathepsin K (CTSK) is secreted by osteoclasts to degrade collagen and other matrix proteins during bone resorption. Global deletion of Ctsk in mice decreases bone resorption, leading to osteopetrosis, but also increases the bone formation rate (BFR). To understand how Ctsk deletion increases the BFR, we generated osteoclast- and osteoblast-targeted Ctsk knockout mice using floxed Ctsk alleles. Targeted ablation of Ctsk in hematopoietic cells, or specifically in osteoclasts and cells of the monocyte-osteoclast lineage, resulted in increased bone volume and BFR as well as osteoclast and osteoblast numbers. In contrast, targeted deletion of Ctsk in osteoblasts had no effect on bone resorption or BFR, demonstrating that the increased BFR is osteoclast dependent. Deletion of Ctsk in osteoclasts increased their sphingosine kinase 1 (Sphk1) expression. Conditioned media from Ctsk-deficient osteoclasts, which contained elevated levels of sphingosine-1-phosphate (S1P), increased alkaline phosphatase and mineralized nodules in osteoblast cultures. An S1P1,3 receptor antagonist inhibited these responses. Osteoblasts derived from mice with Ctsk-deficient osteoclasts had an increased RANKL/OPG ratio, providing a positive feedback loop that increased the number of osteoclasts. Our data provide genetic evidence that deletion of CTSK in osteoclasts enhances bone formation in vivo by increasing the generation of osteoclast-derived S1P.
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Affiliation(s)
- Sutada Lotinun
- Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
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63
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Oikawa T, Kuroda Y, Matsuo K. Regulation of osteoclasts by membrane-derived lipid mediators. Cell Mol Life Sci 2013; 70:3341-53. [PMID: 23296124 PMCID: PMC3753467 DOI: 10.1007/s00018-012-1238-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 12/05/2012] [Accepted: 12/10/2012] [Indexed: 12/22/2022]
Abstract
Osteoclasts are bone-resorbing cells of monocytic origin. An imbalance between bone formation and resorption can lead to osteoporosis or osteopetrosis. Osteoclastogenesis is triggered by RANKL- and IP3-induced Ca2+ influx followed by activation of NFATc1, a master transcription factor for osteoclastogenic gene regulation. During differentiation, osteoclasts undergo cytoskeletal remodeling to migrate and attach to the bone surface. Simultaneously, they fuse with each other to form multinucleated cells. These processes require PI3-kinase-dependent cytoskeletal protein activation to initiate cytoskeletal remodeling, resulting in the formation of circumferential podosomes and fusion-competent protrusions. In multinucleated osteoclasts, circumferential podosomes mature into stabilized actin rings, which enables the formation of a ruffled border where intensive membrane trafficking is executed. Membrane lipids, especially phosphoinositides, are key signaling molecules that regulate osteoclast morphology and act as second messengers and docking sites for multiple important effectors. We examine the critical roles of phosphoinositides in the signaling cascades that regulate osteoclast functions.
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Affiliation(s)
- Tsukasa Oikawa
- Laboratory of Cell and Tissue Biology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
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64
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Deselm CJ, Zou W, Teitelbaum SL. Halofuginone prevents estrogen-deficient osteoporosis in mice. J Cell Biochem 2013; 113:3086-92. [PMID: 22581682 DOI: 10.1002/jcb.24185] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Osteoporosis is characterized by enhanced activity of osteoclasts relative to that of osteoblasts. Thus, the principal means of treating the most common form of osteoporosis, namely that attending menopause, is inhibition of osteoclast formation or function. We have demonstrated that the inflammatory cytokine, IL-17, mediates estrogen-deficient osteoporosis, in mice, and that genetic blockade of its function prevents ovariectomy-induced bone loss. We herein report that the febrifugine derivative, halofuginone, a small molecule drug, reduces abundance of Th-17 cells in mice and prevents estrogen-deficient osteoporosis by diminishing bone resorption without impacting osteogenesis. In keeping with IL-17 mediating its osteoclastogenic effects by promoting RANK ligand expression by osteoblasts, halofuginone does not directly inhibit the bone resorptive cell. Thus, halofuginone, which is presently FDA-approved for treatment of scleroderma, is a candidate therapeutic for post-menopausal osteoporosis.
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Affiliation(s)
- Carl J Deselm
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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65
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Ng PY, Cheng TS, Zhao H, Ye S, Sm Ang E, Khor EC, Feng HT, Xu J, Zheng MH, Pavlos NJ. Disruption of the dynein-dynactin complex unveils motor-specific functions in osteoclast formation and bone resorption. J Bone Miner Res 2013; 28:119-34. [PMID: 22887640 DOI: 10.1002/jbmr.1725] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 07/02/2012] [Accepted: 07/27/2012] [Indexed: 12/22/2022]
Abstract
Osteoclastic bone resorption requires strict interplay between acidified carrier vesicles, motor proteins, and the underlying cytoskeleton in order to sustain the specialized structural and functional polarization of the ruffled border. Cytoplasmic dynein, a large processive mechanochemical motor comprising heavy, intermediate, and light chains coupled to the dynactin cofactor complex, powers unilateral motility of diverse cargos to microtubule minus-ends. We have recently shown that regulators of the dynein motor complex constitute critical components of the osteoclastic bone resorptive machinery. Here, by selectively modulating endogenous dynein activity, we show that the integrity of the dynein-dynactin motor complex is an essential requirement for both osteoclast formation and function. Systematic dissection of the osteoclast dynein-dynactin complex revealed that it is differentially localized throughout RANKL-induced osteoclast formation and activation, undergoing microtubule-coupled reorganization upon the establishment of cellular polarization. In osteoclasts actively resorbing bone, dynein-dynactin intimately co-localizes with the CAP-Gly domain-containing microtubule plus-end protein CLIP-170 at the resorptive front, thus orientating the ruffled border as a microtubule plus-end domain. Unexpectedly, disruption of the dynein-dynactin complex by exogenous p50/dynamitin expression retards osteoclast formation in vitro, owing largely to prolonged mitotic stasis of osteoclast progenitor cells. More importantly, loss of osteoclastic dynein activity results in a drastic redistribution of key intracellular organelles, including the Golgi and lysosomes, an effect that coincides with impaired cathepsin K secretion and diminished bone resorptive function. Collectively, these data unveil a previously unrecognized role for the dynein-dynactin motor complex in osteoclast formation and function, serving not only to regulate their timely maturation but also the delivery of osteolytic cargo that is essential to the bone resorptive process.
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Affiliation(s)
- Pei Ying Ng
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Nedlands, WA, Australia
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66
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Zou W, DeSelm CJ, Broekelmann TJ, Mecham RP, Pol SV, Choi K, Teitelbaum SL. Paxillin contracts the osteoclast cytoskeleton. J Bone Miner Res 2012; 27:2490-500. [PMID: 22807029 PMCID: PMC3494816 DOI: 10.1002/jbmr.1706] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/27/2012] [Accepted: 07/03/2012] [Indexed: 01/09/2023]
Abstract
Osteoclastic bone resorption depends upon the cell's ability to organize its cytoskeleton via the αvβ3 integrin and osteoclastogenic cytokines. Because paxillin associates with αvβ3, we asked if it participates in skeletal degradation. Unlike deletion of other αvβ3-associated cytoskeleton-regulating molecules, which impairs the cell's ability to spread, paxillin-deficient (Pax(-/-) ) osteoclasts, generated from embryonic stem cells, "superspread" in response to receptor activator of NF-κB ligand (RANKL) and form large, albeit dynamically atypical, actin bands. Despite their increased size, Pax(-/-) osteoclasts resorb bone poorly, excavating pits approximately one-third normal depth. Ligand-occupied αvβ3 or RANKL promotes paxillin serine and tyrosine phosphorylation, the latter via cellular sarcoma (c-Src). The abnormal Pax(-/-) phenotype is rescued by wild-type (WT) paxillin but not that lacking its LD4 domain. In keeping with the appearance of mutant osteoclasts, WT paxillin, overexpressed in WT cells, contracts the cytoskeleton. Most importantly, the abnormal phenotype of Pax(-/-) osteoclasts likely represents failed RANKL-mediated delivery of myosin IIA to the actin cytoskeleton via the paxillin LD4 domain but is independent of tyrosine phosphorylation. Thus, in response to RANKL, paxillin associates with myosin IIA to contract the osteoclast cytoskeleton, thereby promoting its bone-degrading capacity.
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Affiliation(s)
- Wei Zou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Carl J. DeSelm
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
- Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110
| | - Thomas J. Broekelmann
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Robert P. Mecham
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Scott Vande Pol
- Department of Pathology, University of Virginia, Charlottesville, VA 22908
| | - Kyunghee Choi
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Steven L. Teitelbaum
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Medicine, Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO 63110
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67
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Cremasco V, Decker CE, Stumpo D, Blackshear PJ, Nakayama KI, Nakayama K, Lupu TS, Graham DB, Novack DV, Faccio R. Protein kinase C-delta deficiency perturbs bone homeostasis by selective uncoupling of cathepsin K secretion and ruffled border formation in osteoclasts. J Bone Miner Res 2012; 27:2452-63. [PMID: 22806935 PMCID: PMC3498518 DOI: 10.1002/jbmr.1701] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/12/2012] [Accepted: 06/26/2012] [Indexed: 01/27/2023]
Abstract
Bone homeostasis requires stringent regulation of osteoclasts, which secrete proteolytic enzymes to degrade the bone matrix. Despite recent progress in understanding how bone resorption occurs, the mechanisms regulating osteoclast secretion, and in particular the trafficking route of cathepsin K vesicles, remain elusive. Using a genetic approach, we describe the requirement for protein kinase C-delta (PKCδ) in regulating bone resorption by affecting cathepsin K exocytosis. Importantly, PKCδ deficiency does not perturb formation of the ruffled border or trafficking of lysosomal vesicles containing the vacuolar-ATPase (v-ATPase). Mechanistically, we find that cathepsin K exocytosis is controlled by PKCδ through modulation of the actin bundling protein myristoylated alanine-rich C-kinase substrate (MARCKS). The relevance of our finding is emphasized in vivo because PKCδ-/- mice exhibit increased bone mass and are protected from pathological bone loss in a model of experimental postmenopausal osteoporosis. Collectively, our data provide novel mechanistic insights into the pathways that selectively promote secretion of cathepsin K lysosomes independently of ruffled border formation, providing evidence of the presence of multiple mechanisms that regulate lysosomal exocytosis in osteoclasts.
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Affiliation(s)
- Viviana Cremasco
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Corinne E. Decker
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Deborah Stumpo
- Laboratory of Signal transduction; National Institute of Environmental Health Science; Research Triangle Park, NC, 27709; USA
| | - Perry J. Blackshear
- Laboratory of Signal transduction; National Institute of Environmental Health Science; Research Triangle Park, NC, 27709; USA
| | - Keiichi I. Nakayama
- Department of Molecular and Cellular Biology; Medical Institute of Bioregulation; Kyushu University; Fukuoka, Fukuoka 812-8582; JAPAN
| | - Keiko Nakayama
- Department of Developmental Genetics; Center for Translational and Advanced Animal Research; Graduate School of Medicine; Tohoku University; Aoba-ku, Sendai 980-8575; Japan
| | - Traian S. Lupu
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Daniel B. Graham
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Deborah V. Novack
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Roberta Faccio
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
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68
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Shinohara M, Nakamura M, Masuda H, Hirose J, Kadono Y, Iwasawa M, Nagase Y, Ueki K, Kadowaki T, Sasaki T, Kato S, Nakamura H, Tanaka S, Takayanagi H. Class IA phosphatidylinositol 3-kinase regulates osteoclastic bone resorption through protein kinase B-mediated vesicle transport. J Bone Miner Res 2012; 27:2464-75. [PMID: 22806988 DOI: 10.1002/jbmr.1703] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 05/22/2012] [Accepted: 06/26/2012] [Indexed: 12/20/2022]
Abstract
Class IA phosphatidylinositol 3-kinases (PI3Ks) are activated by growth factor receptors and regulate a wide range of cellular processes. In osteoclasts, they are activated downstream of α(v) β(3) integrin and colony-stimulating factor-1 receptor (c-Fms), which are involved in the regulation of bone-resorbing activity. The physiological relevance of the in vitro studies using PI3K inhibitors has been of limited value, because they inhibit all classes of PI3K. Here, we show that the osteoclast-specific deletion of the p85 genes encoding the regulatory subunit of the class IA PI3K results in an osteopetrotic phenotype caused by a defect in the bone-resorbing activity of osteoclasts. Class IA PI3K is required for the ruffled border formation and vesicular transport, but not for the formation of the sealing zone. p85α/β doubly deficient osteoclasts had a defect in macrophage colony-stimulating factor (M-CSF)-induced protein kinase B (Akt) activation and the introduction of constitutively active Akt recovered the bone-resorbing activity. Thus, the class IA PI3K-Akt pathway regulates the cellular machinery crucial for osteoclastic bone resorption, and may provide a molecular basis for therapeutic strategies against bone diseases.
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Affiliation(s)
- Masahiro Shinohara
- Department of Cell Signaling, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
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69
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Hwang SY, Foley J, Numaga-Tomita T, Petranka JG, Bird GS, Putney JW. Deletion of Orai1 alters expression of multiple genes during osteoclast and osteoblast maturation. Cell Calcium 2012; 52:488-500. [PMID: 23122304 DOI: 10.1016/j.ceca.2012.10.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 09/28/2012] [Accepted: 10/01/2012] [Indexed: 01/08/2023]
Abstract
Store-operated Ca(2+) entry (SOCE) is a major Ca(2+) influx pathway in most non-excitable cell types and Orai1 was recently identified as an essential pore-subunit of SOCE channels. Here we investigate the physiological role of Orai1 in bone homeostasis using Orai1-deficient mice (Orai1(-/-)). Orai1(-/-) mice developed osteopenia with decreased bone mineral density and trabecular bone volume. To identify the nature and origin of the bone defect, bone-resorbing osteoclasts and bone-forming osteoblasts from Orai1(-/-) mice were examined. Orai1-mediated SOCE was completely abolished in Orai1(-/-) osteoclast precursor cells and osteoclastogenesis in vitro from Orai1(-/-) mice was impaired due to a defect in cell fusion of pre-osteoclasts. Also, resorption activity in vitro was comparable but the size of pits formed by Orai1(-/-) osteoclasts was smaller. We next assessed the role of Orai1 in osteoblast differentiation and function by using a pre-osteoblast cell line, as well as primary osteoblasts from wild-type and Orai1(-/-) mice. SOCE in MC3T3-E1 pre-osteoblastic cells was inactivated by lentiviral overexpression of a pore-dead Orai1 mutant. Lack of SOCE in MC3T3-E1 had no effect on alkaline phosphatase staining and expression but substantially inhibited mineralized nodule formation. Consistent with this finding, Orai1-mediated SOCE was markedly reduced in Orai1(-/-) osteoblast precursor cells and osteoblastogenesis in vitro from Orai1(-/-) stromal cells showed impaired mineral deposition but no change in differentiation. This indicates that Orai1 is involved in the function but not in the differentiation of osteoblasts. Together, these results suggest that Orai1 plays a critical role in bone homeostasis by regulating both osteoblasts and osteoclasts.
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Affiliation(s)
- Sung-Yong Hwang
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
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70
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Zhao H. Membrane trafficking in osteoblasts and osteoclasts: new avenues for understanding and treating skeletal diseases. Traffic 2012; 13:1307-14. [PMID: 22759194 DOI: 10.1111/j.1600-0854.2012.01395.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 06/28/2012] [Accepted: 07/03/2012] [Indexed: 12/21/2022]
Abstract
The endocytic and exocytic/secretory pathways are two major intracellular membrane trafficking routes that regulate numerous cellular functions in a variety of cell types. Osteoblasts and osteoclasts, two major bone cells responsible for bone remodeling and homeostasis, are no exceptions. During the past few years, emerging evidence has pinpointed a critical role for endocytic and secretory pathways in osteoblast and osteoclast differentiation and function. The endosomal membrane provides a platform to integrate bone tropic signals of hormones and growth factors in osteoblasts. In osteoclasts, endocytosis, followed by transcytosis, of degraded bone matrix promotes bone resorption. Secretory pathways, especially lysosome secretion, not only participate in bone matrix deposition by osteoblasts and degradation of mineralized bone matrix by osteoclasts; they may also be involved in the coupling of bone resorption and bone formation during bone remodeling. More importantly, mutations in genes encoding regulatory factors within the endocytic and secretory pathways have been identified as causes for bone diseases. Identification of the molecular mechanisms of these genes in bone cells may provide new therapeutic targets for skeletal disorders.
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Affiliation(s)
- Haibo Zhao
- Department of Internal Medicine, Center for Osteoporosis and Bone Metabolic Diseases, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR, 72205, USA.
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71
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Abstract
The osteoclast cytoskeleton is a unique structure that polarizes the cell's resorptive machinery to the bone-cell interface where it creates an isolated resorptive microenvironment consisting of an actin ring surrounding a ruffled border. This polarization process occurs under the aegis of the α(v) β(3) integrin in collaboration with the M-CSF receptor, c-Fms. When occupied, α(v) β(3) activates a canonical signaling complex consisting of c-Src, Syk, Dap12, Slp76, Vav 3, and Rac that permits the cell to spread and form actin rings. Generation of the ruffled border, the cell's resorptive organelle, is an exocytic process wherein synaptotagmin VII mediates fusion of secretory lysosomes to the bone-apposed plasma membrane. Absence of any component of this signaling pathway compromises osteoclast cytoskeletal organization and abridges bone resorption.
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Affiliation(s)
- Steven L Teitelbaum
- Departments of Pathology and Immunology, and Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
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72
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Stenbeck G, Lawrence KM, Albert AP. Hormone-stimulated modulation of endocytic trafficking in osteoclasts. Front Endocrinol (Lausanne) 2012; 3:103. [PMID: 22936925 PMCID: PMC3424527 DOI: 10.3389/fendo.2012.00103] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 08/05/2012] [Indexed: 11/30/2022] Open
Abstract
A precise control of vesicular trafficking is crucial not only for osteoclastic bone resorption, but also for the crosstalk between osteoclasts and osteoblasts, which regulates bone homeostasis. In addition to the release of growth factors and modulators, such as glutamate, flux through the intracellular trafficking routes could also provide the osteoclast with a monitoring function of its resorption activity. To establish the signaling pathways regulating trafficking events in resorbing osteoclasts, we used the bone conserving hormone calcitonin, which has the unique property of inducing osteoclast quiescence. Calcitonin acts through the calcitonin receptor and activates multiple signaling pathways. By monitoring trafficking of a fluorescent low molecular weight probe in mature, bone resorbing osteoclasts we show for the first time that calcitonin blocks endocytosis from the ruffled border by phospholipase C (PLC) activation. Furthermore, we identify a requirement for polyunsaturated fatty acids in endocytic trafficking in osteoclasts. Inhibition of PLC prior to calcitonin treatment restores endocytosis to 75% of untreated rates. This effect is independent of protein kinase C activation and can be mimicked by an increase in intracellular calcium. We thus define an essential role for intracellular calcium levels in the maintenance of endocytosis in osteoclasts.
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Affiliation(s)
- Gudrun Stenbeck
- Centre for Cell and Chromosome Biology, School of Health Science and Social Care, Brunel UniversityUxbridge, UK
- *Correspondence: Gudrun Stenbeck, Centre for Cell and Chromosome Biology, School of Health Science and Social Care, Heinz Wolff Building, Brunel University, Uxbridge UB8 3PH, UK. e-mail:
| | - Kevin M. Lawrence
- Pharmacology and Cell Physiology, Biomedical Sciences Research Centre, Division of Biomedical Sciences, St George’s, University of LondonLondon, UK
| | - Anthony P. Albert
- Pharmacology and Cell Physiology, Biomedical Sciences Research Centre, Division of Biomedical Sciences, St George’s, University of LondonLondon, UK
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73
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Croke M, Ross FP, Korhonen M, Williams DA, Zou W, Teitelbaum SL. Rac deletion in osteoclasts causes severe osteopetrosis. J Cell Sci 2011; 124:3811-21. [PMID: 22114304 PMCID: PMC3225269 DOI: 10.1242/jcs.086280] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2011] [Indexed: 02/04/2023] Open
Abstract
Cdc42 mediates bone resorption principally by stimulating osteoclastogenesis. Whether its sister GTPase, Rac, meaningfully impacts upon the osteoclast and, if so, by what means, is unclear. We find that whereas deletion of Rac1 or Rac2 alone has no effect, variable reduction of Rac1 in osteoclastic cells of Rac2(-/-) mice causes severe osteopetrosis. Osteoclasts lacking Rac1 and Rac2 in combination (Rac double-knockout, RacDKO), fail to effectively resorb bone. By contrast, osteoclasts are abundant in RacDKO osteopetrotic mice and, unlike those deficient in Cdc42, express the maturation markers of the cells normally. Hence, the osteopetrotic lesion of RacDKO mice largely reflects impaired function, and not arrested differentiation, of the resorptive polykaryon. The dysfunction of RacDKO osteoclasts represents failed cytoskeleton organization as evidenced by reduced motility of the cells and their inability to spread or generate the key resorptive organelles (i.e. actin rings and ruffled borders), which is accompanied by abnormal Arp3 distribution. The cytoskeleton-organizing capacity of Rac1 is mediated through its 20-amino-acid effector domain. Thus, Rac1 and Rac2 are mutually compensatory. Unlike Cdc42 deficiency, their combined absence does not impact upon differentiation but promotes severe osteopetrosis by dysregulating the osteoclast cytoskeleton.
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Affiliation(s)
- Monica Croke
- Department of Pathology and Immunology, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
- Division of Biology and Biomedical Sciences, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
| | - F. Patrick Ross
- Department of Pathology and Immunology, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
| | | | - David A. Williams
- Division of Hematology/Oncology, Children's Hospital Boston, Boston, MA 02115, USA
| | - Wei Zou
- Department of Pathology and Immunology, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
| | - Steven L. Teitelbaum
- Department of Pathology and Immunology, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
- Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
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74
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Crotti TN, O'Sullivan RP, Shen Z, Flannery MR, Fajardo RJ, Ross FP, Goldring SR, McHugh KP. Bone matrix regulates osteoclast differentiation and annexin A8 gene expression. J Cell Physiol 2011; 226:3413-21. [PMID: 21344395 DOI: 10.1002/jcp.22699] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
While attachment to bone is required for optimal osteoclast function, the molecular events that underlie this fact are unclear, other than that the cell requires adhesion to mineralized matrix to assume a fully differentiated phenotype. To address this issue, we cultured murine bone marrow-derived osteoclasts on either cell culture plastic or devitalized mouse calvariae to identify the distinct genetic profile induced by interaction with bone. Among a number of genes previously unknown to be expressed in osteoclasts we found that Annexin A8 (AnxA8) mRNA was markedly up-regulated by bone. AnxA8 protein was present at high levels in osteoclasts present in human tissues recovered from sites of pathological bone loss. The presence of bone mineral was required for up-regulation of AnxA8 mRNA since osteoclasts plated on decalcified bone express AnxA8 at low levels as did osteoclasts plated on native or denatured type I collagen. Finally, AnxA8-regulated cytoskeletal reorganization in osteoclasts generated on a mineralized matrix. Thus, we used a novel approach to define a distinct bone-dependent genetic program associated with terminal osteoclast differentiation and identified Anxa8 as a gene strongly induced late in osteoclast differentiation and a protein that regulates formation of the cell's characteristic actin ring.
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Affiliation(s)
- Tania N Crotti
- Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, South Australia, Australia
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75
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DeSelm CJ, Miller BC, Zou W, Beatty WL, van Meel E, Takahata Y, Klumperman J, Tooze SA, Teitelbaum SL, Virgin HW. Autophagy proteins regulate the secretory component of osteoclastic bone resorption. Dev Cell 2011; 21:966-74. [PMID: 22055344 DOI: 10.1016/j.devcel.2011.08.016] [Citation(s) in RCA: 355] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 07/01/2011] [Accepted: 08/19/2011] [Indexed: 01/13/2023]
Abstract
Osteoclasts resorb bone via the ruffled border, whose complex folds are generated by secretory lysosome fusion with bone-apposed plasma membrane. Lysosomal fusion with the plasmalemma results in acidification of the resorptive microenvironment and release of CatK to digest the organic matrix of bone. The means by which secretory lysosomes are directed to fuse with the ruffled border are enigmatic. We show that proteins essential for autophagy, including Atg5, Atg7, Atg4B, and LC3, are important for generating the osteoclast ruffled border, the secretory function of osteoclasts, and bone resorption in vitro and in vivo. Further, Rab7, which is required for osteoclast function, localizes to the ruffled border in an Atg5-dependent manner. Thus, autophagy proteins participate in polarized secretion of lysosomal contents into the extracellular space by directing lysosomes to fuse with the plasma membrane. These findings are in keeping with a putative link between autophagy genes and human skeletal homeostasis.
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Affiliation(s)
- Carl J DeSelm
- Department of Pathology, Washington University Medical School, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
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76
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Mellis DJ, Itzstein C, Helfrich MH, Crockett JC. The skeleton: a multi-functional complex organ: the role of key signalling pathways in osteoclast differentiation and in bone resorption. J Endocrinol 2011; 211:131-43. [PMID: 21903860 DOI: 10.1530/joe-11-0212] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Osteoclasts are the specialised cells that resorb bone matrix and are important both for the growth and shaping of bones throughout development as well as during the process of bone remodelling that occurs throughout life to maintain a healthy skeleton. Osteoclast formation, function and survival are tightly regulated by a network of signalling pathways, many of which have been identified through the study of rare monogenic diseases, knockout mouse models and animal strains carrying naturally occurring mutations in key molecules. In this review, we describe the processes of osteoclast formation, activation and function and discuss the major transcription factors and signalling pathways (including those that control the cytoskeletal rearrangements) that are important at each stage.
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Affiliation(s)
- David J Mellis
- Musculoskeletal Research Programme, University of Aberdeen, Institute of Medical Sciences, Foresterhill, UK
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77
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van Meel E, Boonen M, Zhao H, Oorschot V, Ross FP, Kornfeld S, Klumperman J. Disruption of the Man-6-P targeting pathway in mice impairs osteoclast secretory lysosome biogenesis. Traffic 2011; 12:912-24. [PMID: 21466643 PMCID: PMC3115509 DOI: 10.1111/j.1600-0854.2011.01203.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Osteoclasts are specialized cells that secrete lysosomal acid hydrolases at the site of bone resorption, a process critical for skeletal formation and remodeling. However, the cellular mechanism underlying this secretion and the organization of the endo-lysosomal system of osteoclasts have remained unclear. We report that osteoclasts differentiated in vitro from murine bone marrow macrophages contain two types of lysosomes. The major species is a secretory lysosome containing cathepsin K and tartrate-resistant acid phosphatase (TRAP), two hydrolases critical for bone resorption. These secretory lysosomes are shown to fuse with the plasma membrane, allowing the regulated release of acid hydrolases at the site of bone resorption. The other type of lysosome contains cathepsin D, but little cathepsin K or TRAP. Osteoclasts from Gnptab(-/-) (gene encoding GlcNAc-1-phosphotransferase α, β-subunits) mice, which lack a functional mannose 6-phosphate (Man-6-P) targeting pathway, show increased secretion of cathepsin K and TRAP and impaired secretory lysosome formation. However, cathepsin D targeting was intact, showing that osteoclasts have a Man-6-P-independent pathway for selected acid hydrolases.
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Affiliation(s)
- Eline van Meel
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, the Netherlands
| | - Marielle Boonen
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Haibo Zhao
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Viola Oorschot
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, the Netherlands
| | - F. Patrick Ross
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stuart Kornfeld
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, the Netherlands
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78
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Laulagnier K, Schieber NL, Maritzen T, Haucke V, Parton RG, Gruenberg J. Role of AP1 and Gadkin in the traffic of secretory endo-lysosomes. Mol Biol Cell 2011; 22:2068-82. [PMID: 21525240 PMCID: PMC3113771 DOI: 10.1091/mbc.e11-03-0193] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 04/12/2011] [Accepted: 04/19/2011] [Indexed: 11/11/2022] Open
Abstract
Whereas lysosome-related organelles (LRO) of specialized cells display both exocytic and endocytic features, lysosomes in nonspecialized cells can also acquire the property to fuse with the plasma membrane upon an acute rise in cytosolic calcium. Here, we characterize this unconventional secretory pathway in fibroblast-like cells, by monitoring the appearance of Lamp1 on the plasma membrane and the release of lysosomal enzymes into the medium. After sequential ablation of endocytic compartments in living cells, we find that donor membranes primarily derive from a late compartment, but that an early compartment is also involved. Strikingly, this endo-secretory process is not affected by treatments that inhibit endosome dynamics (microtubule depolymerization, cholesterol accumulation, overexpression of Rab7 or its effector Rab-interacting lysosomal protein [RILP], overexpression of Rab5 mutants), but depends on Rab27a, a GTPase involved in LRO secretion, and is controlled by F-actin. Moreover, we find that this unconventional endo-secretory pathway requires the adaptor protein complexes AP1, Gadkin (which recruits AP1 by binding to the γ1 subunit), and AP2, but not AP3. We conclude that a specific fraction of the AP2-derived endocytic pathway is dedicated to secretory purposes under the control of AP1 and Gadkin.
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Affiliation(s)
- Karine Laulagnier
- Department of Biochemistry, University of Geneva, 1211-Geneva-4, Switzerland
| | - Nicole L. Schieber
- Institute for Molecular Bioscience and Center for Microscopy and Microanalysis, The University of Queensland, Brisbane 4072, Australia
| | - Tanja Maritzen
- Laboratory of Membrane Biochemistry, Freie Universitaet Berlin, 14195 Berlin, Germany
| | - Volker Haucke
- Laboratory of Membrane Biochemistry, Freie Universitaet Berlin, 14195 Berlin, Germany
| | - Robert G. Parton
- Institute for Molecular Bioscience and Center for Microscopy and Microanalysis, The University of Queensland, Brisbane 4072, Australia
| | - Jean Gruenberg
- Department of Biochemistry, University of Geneva, 1211-Geneva-4, Switzerland
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79
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Sausbier U, Dullin C, Missbach-Guentner J, Kabagema C, Flockerzie K, Kuscher GM, Stuehmer W, Neuhuber W, Ruth P, Alves F, Sausbier M. Osteopenia due to enhanced cathepsin K release by BK channel ablation in osteoclasts. PLoS One 2011; 6:e21168. [PMID: 21695131 PMCID: PMC3114853 DOI: 10.1371/journal.pone.0021168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 05/23/2011] [Indexed: 01/05/2023] Open
Abstract
Background The process of bone resorption by osteoclasts is regulated by Cathepsin K, the lysosomal collagenase responsible for the degradation of the organic bone matrix during bone remodeling. Recently, Cathepsin K was regarded as a potential target for therapeutic intervention of osteoporosis. However, mechanisms leading to osteopenia, which is much more common in young female population and often appears to be the clinical pre-stage of idiopathic osteoporosis, still remain to be elucidated, and molecular targets need to be identified. Methodology/Principal Findings We found, that in juvenile bone the large conductance, voltage and Ca2+-activated (BK) K+ channel, which links membrane depolarization and local increases in cytosolic calcium to hyperpolarizing K+ outward currents, is exclusively expressed in osteoclasts. In juvenile BK-deficient (BK−/−) female mice, plasma Cathepsin K levels were elevated two-fold when compared to wild-type littermates. This increase was linked to an osteopenic phenotype with reduced bone mineral density in long bones and enhanced porosity of trabecular meshwork in BK−/− vertebrae as demonstrated by high-resolution flat-panel volume computed tomography and micro-CT. However, plasma levels of sRANKL, osteoprotegerin, estrogene, Ca2+ and triiodthyronine as well as osteoclastogenesis were not altered in BK−/− females. Conclusion/Significance Our findings suggest that the BK channel controls resorptive osteoclast activity by regulating Cathepsin K release. Targeted deletion of BK channel in mice resulted in an osteoclast-autonomous osteopenia, becoming apparent in juvenile females. Thus, the BK−/− mouse-line represents a new model for juvenile osteopenia, and revealed the BK channel as putative new target for therapeutic controlling of osteoclast activity.
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Affiliation(s)
- Ulrike Sausbier
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Christian Dullin
- Department of Diagnostic Radiology, University Medical Center Göttingen, Göttingen, Germany
| | | | - Clement Kabagema
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Katarina Flockerzie
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Gerd Marten Kuscher
- Max-Planck-Institute for Experimental Medicine, Department of Molecular Biology of Neuronal Signals, Göttingen, Germany
| | - Walter Stuehmer
- Max-Planck-Institute for Experimental Medicine, Department of Molecular Biology of Neuronal Signals, Göttingen, Germany
| | - Winfried Neuhuber
- Institute for Anatomy, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Peter Ruth
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Frauke Alves
- Max-Planck-Institute for Experimental Medicine, Department of Molecular Biology of Neuronal Signals, Göttingen, Germany
- Department of Hematology and Oncology, University Medical Center Göttingen, Göttingen, Germany
| | - Matthias Sausbier
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
- * E-mail:
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80
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Farber CR, Bennett BJ, Orozco L, Zou W, Lira A, Kostem E, Kang HM, Furlotte N, Berberyan A, Ghazalpour A, Suwanwela J, Drake TA, Eskin E, Wang QT, Teitelbaum SL, Lusis AJ. Mouse genome-wide association and systems genetics identify Asxl2 as a regulator of bone mineral density and osteoclastogenesis. PLoS Genet 2011; 7:e1002038. [PMID: 21490954 PMCID: PMC3072371 DOI: 10.1371/journal.pgen.1002038] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 02/12/2011] [Indexed: 12/31/2022] Open
Abstract
Significant advances have been made in the discovery of genes affecting bone mineral density (BMD); however, our understanding of its genetic basis remains incomplete. In the current study, genome-wide association (GWA) and co-expression network analysis were used in the recently described Hybrid Mouse Diversity Panel (HMDP) to identify and functionally characterize novel BMD genes. In the HMDP, a GWA of total body, spinal, and femoral BMD revealed four significant associations (-log10P>5.39) affecting at least one BMD trait on chromosomes (Chrs.) 7, 11, 12, and 17. The associations implicated a total of 163 genes with each association harboring between 14 and 112 genes. This list was reduced to 26 functional candidates by identifying those genes that were regulated by local eQTL in bone or harbored potentially functional non-synonymous (NS) SNPs. This analysis revealed that the most significant BMD SNP on Chr. 12 was a NS SNP in the additional sex combs like-2 (Asxl2) gene that was predicted to be functional. The involvement of Asxl2 in the regulation of bone mass was confirmed by the observation that Asxl2 knockout mice had reduced BMD. To begin to unravel the mechanism through which Asxl2 influenced BMD, a gene co-expression network was created using cortical bone gene expression microarray data from the HMDP strains. Asxl2 was identified as a member of a co-expression module enriched for genes involved in the differentiation of myeloid cells. In bone, osteoclasts are bone-resorbing cells of myeloid origin, suggesting that Asxl2 may play a role in osteoclast differentiation. In agreement, the knockdown of Asxl2 in bone marrow macrophages impaired their ability to form osteoclasts. This study identifies a new regulator of BMD and osteoclastogenesis and highlights the power of GWA and systems genetics in the mouse for dissecting complex genetic traits.
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Affiliation(s)
- Charles R Farber
- Center for Public Health Genomics, University of Virginia, Charlottesville, Virginia, United States of America.
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81
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82
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Tctex-1, a novel interaction partner of Rab3D, is required for osteoclastic bone resorption. Mol Cell Biol 2011; 31:1551-64. [PMID: 21262767 DOI: 10.1128/mcb.00834-10] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Vesicular transport along microtubules must be strictly regulated to sustain the unique structural and functional polarization of bone-resorbing osteoclasts. However, the molecular mechanisms bridging these vesicle-microtubule interactions remain largely obscure. Rab3D, a member of the Rab3 subfamily (Rab3A/B/C/D) of small exocytotic GTPases, represents a core component of the osteoclastic vesicle transport machinery. Here, we identify a new Rab3D-interacting partner, Tctex-1, a light chain of the cytoplasmic dynein microtubule motor complex, by a yeast two-hybrid screen. We demonstrate that Tctex-1 binds specifically to Rab3D in a GTP-dependent manner and co-occupies Rab3D-bearing vesicles in bone-resorbing osteoclasts. Furthermore, we provide evidence that Tctex-1 and Rab3D intimately associate with the dynein motor complex and microtubules in osteoclasts. Finally, targeted disruption of Tctex-1 by RNA interference significantly impairs bone resorption capacity and mislocalizes Rab3D vesicles in osteoclasts, attesting to the notion that components of the Rab3D-trafficking pathway contribute to the maintenance of osteoclastic resorptive function.
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83
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Al-Jallad HF, Myneni VD, Piercy-Kotb SA, Chabot N, Mulani A, Keillor JW, Kaartinen MT. Plasma membrane factor XIIIA transglutaminase activity regulates osteoblast matrix secretion and deposition by affecting microtubule dynamics. PLoS One 2011; 6:e15893. [PMID: 21283799 PMCID: PMC3024320 DOI: 10.1371/journal.pone.0015893] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Accepted: 11/30/2010] [Indexed: 11/19/2022] Open
Abstract
Transglutaminase activity, arising potentially from transglutaminase 2 (TG2) and
Factor XIIIA (FXIIIA), has been linked to osteoblast differentiation where it is
required for type I collagen and fibronectin matrix deposition. In this study we
have used an irreversible TG-inhibitor to ‘block –and-track’
enzyme(s) targeted during osteoblast differentiation. We show that the
irreversible TG-inhibitor is highly potent in inhibiting osteoblast
differentiation and mineralization and reduces secretion of both fibronectin and
type I collagen and their release from the cell surface. Tracking of the dansyl
probe by Western blotting and immunofluorescence microscopy demonstrated that
the inhibitor targets plasma membrane-associated FXIIIA. TG2 appears not to
contribute to crosslinking activity on the osteoblast surface. Inhibition of
FXIIIA with NC9 resulted in defective secretory vesicle delivery to the plasma
membrane which was attributable to a disorganized microtubule network and
decreased microtubule association with the plasma membrane. NC9 inhibition of
FXIIIA resulted in destabilization of microtubules as assessed by cellular
Glu-tubulin levels. Furthermore, NC9 blocked modification of Glu-tubulin into
150 kDa high-molecular weight Glu-tubulin form which was specifically localized
to the plasma membrane. FXIIIA enzyme and its crosslinking activity were
colocalized with plasma membrane-associated tubulin, and thus, it appears that
FXIIIA crosslinking activity is directed towards stabilizing the interaction of
microtubules with the plasma membrane. Our work provides the first mechanistic
cues as to how transglutaminase activity could affect protein secretion and
matrix deposition in osteoblasts and suggests a novel function for plasma
membrane FXIIIA in microtubule dynamics.
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Affiliation(s)
- Hadil F. Al-Jallad
- Division of Biomedical Sciences, Faculty of Dentistry, McGill University,
Montreal, Quebec, Canada
| | - Vamsee D. Myneni
- Division of Biomedical Sciences, Faculty of Dentistry, McGill University,
Montreal, Quebec, Canada
| | - Sarah A. Piercy-Kotb
- Division of Biomedical Sciences, Faculty of Dentistry, McGill University,
Montreal, Quebec, Canada
- Division of Experimental Medicine, Department of Medicine, Faculty of
Medicine, McGill University, Montreal, Quebec, Canada
| | - Nicolas Chabot
- Department of Chemistry, Faculty of Arts and Science, Université
de Montréal, Montreal, Quebec, Canada
| | - Amina Mulani
- Department of Chemistry, Faculty of Arts and Science, Université
de Montréal, Montreal, Quebec, Canada
| | - Jeffrey W. Keillor
- Department of Chemistry, Faculty of Arts and Science, Université
de Montréal, Montreal, Quebec, Canada
| | - Mari T. Kaartinen
- Division of Biomedical Sciences, Faculty of Dentistry, McGill University,
Montreal, Quebec, Canada
- Division of Experimental Medicine, Department of Medicine, Faculty of
Medicine, McGill University, Montreal, Quebec, Canada
- * E-mail:
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84
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Flannery AR, Czibener C, Andrews NW. Palmitoylation-dependent association with CD63 targets the Ca2+ sensor synaptotagmin VII to lysosomes. ACTA ACUST UNITED AC 2010; 191:599-613. [PMID: 21041449 PMCID: PMC3003310 DOI: 10.1083/jcb.201003021] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Posttranslational lipid modifications promote association of Syt VII with the tetraspanin CD63, determining its exit from the Golgi and targeting to lysosomes. Syt VII is a Ca2+ sensor that regulates lysosome exocytosis and plasma membrane repair. Because it lacks motifs that mediate lysosomal targeting, it is unclear how Syt VII traffics to these organelles. In this paper, we show that mutations or inhibitors that abolish palmitoylation disrupt Syt VII targeting to lysosomes, causing its retention in the Golgi complex. In macrophages, Syt VII is translocated simultaneously with the lysosomal tetraspanin CD63 from tubular lysosomes to nascent phagosomes in a Ca2+-dependent process that facilitates particle uptake. Mutations in Syt VII palmitoylation sites block trafficking of Syt VII, but not CD63, to lysosomes and phagosomes, whereas tyrosine replacement in the lysosomal targeting motif of CD63 causes both proteins to accumulate on the plasma membrane. Complexes of CD63 and Syt VII are detected only when Syt VII palmitoylation sites are intact. These findings identify palmitoylation-dependent association with the tetraspanin CD63 as the mechanism by which Syt VII is targeted to lysosomes.
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Affiliation(s)
- Andrew R Flannery
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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85
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Ito Y, Teitelbaum SL, Zou W, Zheng Y, Johnson JF, Chappel J, Ross FP, Zhao H. Cdc42 regulates bone modeling and remodeling in mice by modulating RANKL/M-CSF signaling and osteoclast polarization. J Clin Invest 2010; 120:1981-93. [PMID: 20501942 DOI: 10.1172/jci39650] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Accepted: 02/24/2010] [Indexed: 11/17/2022] Open
Abstract
The modeling and remodeling of bone requires activation and polarization of osteoclasts, achieved by reorganization of the cytoskeleton. Members of the Rho subfamily of small GTPases, including Cdc42, are known regulators of cytoskeletal components, but the role of these proteins in bone physiology and pathophysiology remains unclear. Here, we examined loss-of-function mice in which Cdc42 was selectively ablated in differentiated osteoclasts and gain-of-function animals wherein Cdc42Gap, a protein that inactivates the small GTPase, was deleted globally. Cdc42 loss-of-function mice were osteopetrotic and resistant to ovariectomy-induced bone loss, while gain-of-function animals were osteoporotic. Isolated Cdc42-deficient osteoclasts displayed suppressed bone resorption, while osteoclasts with increased Cdc42 activity had enhanced resorptive capacity. We further demonstrated that Cdc42 modulated M-CSF-stimulated cyclin D expression and phosphorylation of Rb and induced caspase 3 and Bim, thus contributing to osteoclast proliferation and apoptosis rates. Furthermore, Cdc42 was required for multiple M-CSF- and RANKL-induced osteoclastogenic signals including activation and expression of the differentiation factors MITF and NFATc1 and was a component of the Par3/Par6/atypical PKC polarization complex in osteoclasts. These data suggest that Cdc42 regulates osteoclast formation and function and may represent a promising therapeutic target for prevention of pathological bone loss.
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Affiliation(s)
- Yuji Ito
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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86
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Yamazaki T, Takata N, Uemura M, Kawamura Y. Arabidopsis synaptotagmin SYT1, a type I signal-anchor protein, requires tandem C2 domains for delivery to the plasma membrane. J Biol Chem 2010; 285:23165-76. [PMID: 20498364 DOI: 10.1074/jbc.m109.084046] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The correct localization of integral membrane proteins to subcellular compartments is important for their functions. Synaptotagmin contains a single transmembrane domain that functions as a type I signal-anchor sequence in its N terminus and two calcium-binding domains (C(2)A and C(2)B) in its C terminus. Here, we demonstrate that the localization of an Arabidopsis synaptotagmin homolog, SYT1, to the plasma membrane (PM) is modulated by tandem C2 domains. An analysis of the roots of a transformant-expressing green fluorescent protein-tagged SYT1 driven by native SYT1 promoter suggested that SYT1 is synthesized in the endoplasmic reticulum, and then delivered to the PM via the exocytotic pathway. We transiently expressed a series of truncated proteins in protoplasts, and determined that tandem C(2)A-C(2)B domains were necessary for the localization of SYT1 to the PM. The PM localization of SYT1 was greatly reduced following mutation of the calcium-binding motifs of the C(2)B domain, based on sequence comparisons with other homologs, such as endomembrane-localized SYT5. The localization of SYT1 to the PM may have been required for the functional divergence that occurred in the molecular evolution of plant synaptotagmins.
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Affiliation(s)
- Tomokazu Yamazaki
- 21st Century Center of Excellence Program, Iwate University, Morioka, Iwate 020-8550, Japan
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87
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Abstract
The unique ability of the osteoclast to degrade skeletal tissue depends upon formation of a resorptive microenvironment between the osteoclast and the bone surface. Generation of this privileged space is substantially mediated by signals emanating from alphavbeta3 integrin, which transits to its active high-affinity conformation by growth factor-initiated intracellular events targeting the matrix receptor's cytoplasmic domain. The activated liganded integrin stimulates a signaling complex consisting of c-Src, Syk, immunoreceptor tyrosine-based activation motif proteins, Slp-76, Vav3, and members of the Rho family of GTPases. These events contribute to secretory lysososme insertion into the bone-apposed plasma membrane to form the ruffled border that delivers the bone-degrading molecules (HCl and cathepsin K) into the resorptive microenvironment. Integrin/bone recognition also promotes formation of actin rings, which surround the ruffled border, thereby isolating the focus of skeletal degradation from the general extracellular space.
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Affiliation(s)
- Wei Zou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
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88
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Musch MW, Arvans DL, Wang Y, Nakagawa Y, Solomaha E, Chang EB. Cyclic AMP-mediated endocytosis of intestinal epithelial NHE3 requires binding to synaptotagmin 1. Am J Physiol Gastrointest Liver Physiol 2010; 298:G203-11. [PMID: 19926819 PMCID: PMC2822502 DOI: 10.1152/ajpgi.00379.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The apical membrane Na(+)-H(+) exchanger (NHE)3 is regulated by cAMP-dependent phosphorylation, which inhibits its activity through membrane endocytosis. The clathrin complex adaptor protein synaptotagmin 1 (Syt 1) appears to be essential to this process, but little is known about its expression in intestinal epithelial cells or interaction with NHE3. The intestinal epithelial expression and apical location of Syt 1 were determined by Syt 1 mRNA profiling and immunolocalization. Tandem mass spectrometry was used for protein identification. Bis(sulfosuccinimidyl) suberate (BS(3)) cross linking suggested that NHE3 and Syt 1 were in a membrane complex following cAMP stimulation of Caco2BBE (Brush Border Expressions) cells. To investigate the regulation of NHE3 appearance in a Syt 1-containing membrane compartment, doxycycline-inducible hemaglutinin (HA)-tagged NHE3 was expressed in Caco2BBE cells. HA-NHE3 correctly targeted to the apical membrane, where, upon cAMP stimulation, it was internalized with a Syt 1-containing compartment. Site-directed mutagenesis of NHE3 showed that serine 605 (S605) was pivotal to NHE3 and Syt 1 association and internalization. Direct Syt 1 interaction with NHE3 was suggested by fluorescence resonance energy transfer (FRET) analysis. The physiological role of S552 was less clear. By FRET, this serine residue appeared to be involved in cAMP-induced Syt 1 binding of NHE3. However, when HA-tagged NHE3 S552A was expressed in Caco2 cells, the mutated construct was not inserted into the apical membrane. We conclude that intestinal epithelial Syt 1 plays an important role in cAMP-stimulated endocytosis of apical NHE3 through cAMP-dependent phosphorylation of S605 that is required for NHE3 and Syt 1 association.
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Affiliation(s)
| | | | - Yunwei Wang
- 1Martin Boyer Laboratories, Department of Medicine;
| | | | - Elena Solomaha
- 2Biophysical Research Core Facility, Divisions of Biological and Physical Sciences, University of Chicago, Chicago, Illinois
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89
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Calcium-sensing beyond neurotransmitters: functions of synaptotagmins in neuroendocrine and endocrine secretion. Biosci Rep 2009; 29:245-59. [PMID: 19500075 DOI: 10.1042/bsr20090031] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Neurotransmitters, neuropeptides and hormones are released through the regulated exocytosis of SVs (synaptic vesicles) and LDCVs (large dense-core vesicles), a process that is controlled by calcium. Synaptotagmins are a family of type 1 membrane proteins that share a common domain structure. Most synaptotagmins are located in brain and endocrine cells, and some of these synaptotagmins bind to phospholipids and calcium at levels that trigger regulated exocytosis of SVs and LDCVs. This led to the proposed synaptotagmin-calcium-sensor paradigm, that is, members of the synaptotagmin family function as calcium sensors for the regulated exocytosis of neurotransmitters, neuropeptides and hormones. Here, we provide an overview of the synaptotagmin family, and review the recent mouse genetic studies aimed at understanding the functions of synaptotagmins in neurotransmission and endocrine-hormone secretion. Also, we discuss potential roles of synaptotagmins in non-traditional endocrine systems.
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90
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Cross-talk between endocytic clearance and secretion in macrophages. Immunobiology 2009; 214:576-93. [DOI: 10.1016/j.imbio.2009.03.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 03/16/2009] [Indexed: 12/20/2022]
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91
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Zou W, Reeve JL, Zhao H, Ross FP, Teitelbaum SL. Syk tyrosine 317 negatively regulates osteoclast function via the ubiquitin-protein isopeptide ligase activity of Cbl. J Biol Chem 2009; 284:18833-9. [PMID: 19419964 DOI: 10.1074/jbc.m109.012385] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cytoskeletal organization of the osteoclast (OC), which is central to the capacity of the cell to resorb bone, is induced by occupancy of the alphavbeta3 integrin or the macrophage colony-stimulating factor (M-CSF) receptor c-Fms. In both circumstances, the tyrosine kinase Syk is an essential signaling intermediary. We demonstrate that Cbl negatively regulates OC function by interacting with Syk(Y317). Expression of nonphosphorylatable Syk(Y317F) in primary Syk(-/-) OCs enhances M-CSF- and alphavbeta3-induced phosphorylation of the cytoskeleton-organizing molecules, SLP76, Vav3, and PLCgamma2, to levels greater than wild type, thereby accelerating the resorptive capacity of the cell. Syk(Y317) suppresses cytoskeletal organization and function while binding the ubiquitin-protein isopeptide ligase Cbl. Consequently, Syk(Y317F) abolishes M-CSF- and integrin-stimulated Syk ubiquitination. Thus, Cbl/Syk(Y317) association negatively regulates OC function and therefore is essential for maintenance of skeletal homeostasis.
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Affiliation(s)
- Wei Zou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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92
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Gustavsson N, Wei SH, Hoang DN, Lao Y, Zhang Q, Radda GK, Rorsman P, Südhof TC, Han W. Synaptotagmin-7 is a principal Ca2+ sensor for Ca2+ -induced glucagon exocytosis in pancreas. J Physiol 2009; 587:1169-78. [PMID: 19171650 DOI: 10.1113/jphysiol.2008.168005] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Hormones such as glucagon are secreted by Ca(2+)-induced exocytosis of large dense-core vesicles, but the mechanisms involved have only been partially elucidated. Studies of pancreatic beta-cells secreting insulin revealed that synaptotagmin-7 alone is not sufficient to mediate Ca(2+)-dependent insulin granule exocytosis, and studies of chromaffin cells secreting neuropeptides and catecholamines showed that synaptotagmin-1 and -7 collaborate as Ca(2+) sensors for exocytosis, and that both are equally involved. As no other peptide secretion was analysed, it remains unclear whether synaptotagmins generally act as Ca(2+) sensors in large dense-core vesicle exocytosis in endocrine cells, and if so, whether synaptotagmin-7 always functions with a partner in that role. In particular, far less is known about the mechanisms underlying Ca(2+)-triggered glucagon release from alpha-cells than insulin secretion from beta-cells, even though insulin and glucagon together regulate blood glucose levels. To address these issues, we analysed the role of synaptotagmins in Ca(2+)-triggered glucagon exocytosis. Surprisingly, we find that deletion of a single synaptotagmin isoform, synaptotagmin-7, nearly abolished Ca(2+)-triggered glucagon secretion. Moreover, single-cell capacitance measurements confirmed that pancreatic alpha-cells lacking synaptotagmin-7 exhibited little Ca(2+)-induced exocytosis, whereas all other physiological and morphological parameters of the alpha-cells were normal. Our data thus identify synaptotagmin-7 as a principal Ca(2+) sensor for glucagon secretion, and support the notion that synaptotagmins perform a universal but selective function as individually acting Ca(2+) sensors in neurotransmitter, neuropeptide, and hormone secretion.
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Affiliation(s)
- Natalia Gustavsson
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore 138667
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93
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Zhao H, Ito Y, Chappel J, Andrews N, Ross FP, Teitelbaum SL. How do bone cells secrete proteins? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 658:105-9. [PMID: 19950020 DOI: 10.1007/978-1-4419-1050-9_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The ruffled border is the most specific marker of the active osteoclast (OC) as it forms only when the cell is resorbing bone. We provide evidence that this complex cytoskeletal structure reflects insertion of the lysosomal vesicles into the bone-apposed plasma membrane under the aegis of the Ca-sensing, exocytic protein, synaptotagmin VII (SytVII). In the manner, SytVII permits transport of matrix-degrading molecules into the resorptive microenvironment. SytVII also regulates secretion of bone matrix molecules by osteoblasts. Thus, SytVII-deficient mice experience suppressed bone resorption and formation with the latter deficiency predominant thereby yielding osteoporosis characterized by attenuated remodeling.
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Affiliation(s)
- Haibo Zhao
- Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA
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94
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Abstract
Plasma insulin levels are determined mainly by the rate of exocytosis of the insulin-containing large dense core vesicles (LDCVs) of pancreatic islet beta-cells. This process involves the recruitment of LDCVs to the plasma membrane, where they are docked by the assembly of multiprotein SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes. However, fusion of the two membranes will proceed only in the presence of Ca(2+) ions, implicating a Ca(2+) sensor protein. The synaptotagmin gene family, comprising 15 members, was proposed to act as such Ca(2+) sensor in regulated exocytosis in neurons and neuroendocrine and endocrine cells. Herein, we review the physiological function of the various synaptotagmins with reference to their impact on insulin exocytosis. Cumulating evidence emphasizes the crucial role of synaptotagmin VII and IX as mediators of glucose-induced insulin secretion.
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Affiliation(s)
- Benoit R Gauthier
- Dept. of Cell Physiology and Metabolism, University Medical Center, 1211 Geneva 4, Switzerland.
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95
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Idone V, Tam C, Andrews NW. Two-way traffic on the road to plasma membrane repair. Trends Cell Biol 2008; 18:552-9. [PMID: 18848451 DOI: 10.1016/j.tcb.2008.09.001] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 08/31/2008] [Accepted: 09/01/2008] [Indexed: 12/21/2022]
Abstract
Ca(2+) influx through plasma membrane wounds triggers a rapid-repair response that is essential for cell survival. Earlier studies showed that repair requires the exocytosis of intracellular vesicles. Exocytosis was thought to promote resealing by 'patching' the plasma membrane lesion or by facilitating bilayer restoration through reduction in membrane tension. However, cells also rapidly repair lesions created by pore-forming proteins, a form of injury that cannot be resealed solely by exocytosis. Recent studies indicate that, in cells injured by pores or mechanical abrasions, exocytosis is followed by lesion removal through endocytosis. Describing the relationship between wound-induced exocytosis and endocytosis has implications for the understanding of muscular degenerative diseases that are associated with defects in plasma membrane repair.
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Affiliation(s)
- Vincent Idone
- Section of Microbial Pathogenesis, Yale University School of Medicine, 295 Congress Street, New Haven, CT 06511, USA
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96
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Coxon FP, Taylor A. Vesicular trafficking in osteoclasts. Semin Cell Dev Biol 2008; 19:424-33. [DOI: 10.1016/j.semcdb.2008.08.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 08/04/2008] [Accepted: 08/08/2008] [Indexed: 11/24/2022]
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