1
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Philip R, Fiorino C, Harrison RE. Terminally differentiated osteoclasts organize centrosomes into large clusters for microtubule nucleation and bone resorption. Mol Biol Cell 2022; 33:ar68. [PMID: 35511803 DOI: 10.1091/mbc.e22-03-0098] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Osteoclasts are highly specialized, multinucleated cells responsible for the selective resorption of the dense, calcified bone matrix. Microtubules (MTs) contribute to the polarization and trafficking events involved in bone resorption by osteoclasts, however the origin of these elaborate arrays is less clear. Osteoclasts arise through cell fusion of precursor cells. Previous studies have suggested that centrosome MT nucleation is lost during this process, with the nuclear membrane and its surrounding Golgi serving as the major microtubule organizing centres (MTOCs) in these cells. Here we reveal that precursor cell centrosomes are maintained and functional in the multinucleated osteoclast and interestingly form large MTOC clusters, with the clusters organizing significantly more MTs, compared to individual centrosomes. MTOC cluster formation requires dynamic microtubules and minus-end directed MT motor activity. Inhibition of these centrosome clustering elements had a marked impact on both F-actin ring formation and bone resorption. Together these findings show that multinucleated osteoclasts employ unique centrosomal clusters to organize the extensive microtubules during bone attachment and resorption. [Media: see text].
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Affiliation(s)
- Reuben Philip
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.,Lunenfeld-Tanenbaum Research Institute, Toronto, Ontario, Canada, M5G 1 × 5
| | - Cara Fiorino
- Department of Cell & Systems Biology and the Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4
| | - Rene E Harrison
- Department of Cell & Systems Biology and the Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4
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2
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Becker R, Vergarajauregui S, Billing F, Sharkova M, Lippolis E, Mamchaoui K, Ferrazzi F, Engel FB. Myogenin controls via AKAP6 non-centrosomal microtubule-organizing center formation at the nuclear envelope. eLife 2021; 10:65672. [PMID: 34605406 PMCID: PMC8523159 DOI: 10.7554/elife.65672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 10/01/2021] [Indexed: 12/22/2022] Open
Abstract
Non-centrosomal microtubule-organizing centers (MTOCs) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in murine myoblasts for the localization of MTOC proteins to the nuclear envelope. Moreover, myogenin is sufficient in fibroblasts for nuclear envelope MTOC (NE-MTOC) formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated NE-MTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and NE-MTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1α, the NE-MTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous MTOC proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an NE-MTOC and identify AKAP6 as a novel NE-MTOC component in muscle cells.
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Affiliation(s)
- Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Florian Billing
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Maria Sharkova
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Eleonora Lippolis
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Kamel Mamchaoui
- Sorbonne Universités UPMC Université Paris 06, INSERM U974, CNRS FRE3617, Center for Research in Myology, GH Pitié Salpêtrière, 47 Boulevard de l'Hôpital, Paris, France
| | - Fulvia Ferrazzi
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
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3
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Vergarajauregui S, Becker R, Steffen U, Sharkova M, Esser T, Petzold J, Billing F, Kapiloff MS, Schett G, Thievessen I, Engel FB. AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9. eLife 2020; 9:61669. [PMID: 33295871 PMCID: PMC7725499 DOI: 10.7554/elife.61669] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 12/03/2020] [Indexed: 12/31/2022] Open
Abstract
The switch from centrosomal microtubule-organizing centers (MTOCs) to non-centrosomal MTOCs during differentiation is poorly understood. Here, we identify AKAP6 as key component of the nuclear envelope MTOC. In rat cardiomyocytes, AKAP6 anchors centrosomal proteins to the nuclear envelope through its spectrin repeats, acting as an adaptor between nesprin-1α and Pcnt or AKAP9. In addition, AKAP6 and AKAP9 form a protein platform tethering the Golgi to the nucleus. Both Golgi and nuclear envelope exhibit MTOC activity utilizing either AKAP9, or Pcnt-AKAP9, respectively. AKAP6 is also required for formation and activity of the nuclear envelope MTOC in human osteoclasts. Moreover, ectopic expression of AKAP6 in epithelial cells is sufficient to recruit endogenous centrosomal proteins. Finally, AKAP6 is required for cardiomyocyte hypertrophy and osteoclast bone resorption activity. Collectively, we decipher the MTOC at the nuclear envelope as a bi-layered structure generating two pools of microtubules with AKAP6 as a key organizer.
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Affiliation(s)
- Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Ulrike Steffen
- Department of Internal Medicine 3 - Rheumatology and Immunology, Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and Universitätsklinikum Erlangen, Erlangen, Germany
| | - Maria Sharkova
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Tilman Esser
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Jana Petzold
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Florian Billing
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Michael S Kapiloff
- Departments of Ophthalmology and Medicine, Stanford Cardiovascular Institute, Stanford University, Palo Alto, United States
| | - George Schett
- Department of Internal Medicine 3 - Rheumatology and Immunology, Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and Universitätsklinikum Erlangen, Erlangen, Germany
| | - Ingo Thievessen
- Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
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4
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Blangy A, Bompard G, Guerit D, Marie P, Maurin J, Morel A, Vives V. The osteoclast cytoskeleton - current understanding and therapeutic perspectives for osteoporosis. J Cell Sci 2020; 133:133/13/jcs244798. [PMID: 32611680 DOI: 10.1242/jcs.244798] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Osteoclasts are giant multinucleated myeloid cells specialized for bone resorption, which is essential for the preservation of bone health throughout life. The activity of osteoclasts relies on the typical organization of osteoclast cytoskeleton components into a highly complex structure comprising actin, microtubules and other cytoskeletal proteins that constitutes the backbone of the bone resorption apparatus. The development of methods to differentiate osteoclasts in culture and manipulate them genetically, as well as improvements in cell imaging technologies, has shed light onto the molecular mechanisms that control the structure and dynamics of the osteoclast cytoskeleton, and thus the mechanism of bone resorption. Although essential for normal bone physiology, abnormal osteoclast activity can cause bone defects, in particular their hyper-activation is commonly associated with many pathologies, hormonal imbalance and medical treatments. Increased bone degradation by osteoclasts provokes progressive bone loss, leading to osteoporosis, with the resulting bone frailty leading to fractures, loss of autonomy and premature death. In this context, the osteoclast cytoskeleton has recently proven to be a relevant therapeutic target for controlling pathological bone resorption levels. Here, we review the present knowledge on the regulatory mechanisms of the osteoclast cytoskeleton that control their bone resorption activity in normal and pathological conditions.
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Affiliation(s)
- Anne Blangy
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - Guillaume Bompard
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - David Guerit
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - Pauline Marie
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - Justine Maurin
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - Anne Morel
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
| | - Virginie Vives
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
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5
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Wang A, Carraro-Lacroix LR, Owen C, Gao B, Corey PN, Tyrrell P, Brumell JH, Voronov I. Activity-independent targeting of mTOR to lysosomes in primary osteoclasts. Sci Rep 2017; 7:3005. [PMID: 28592812 PMCID: PMC5462732 DOI: 10.1038/s41598-017-03494-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 04/28/2017] [Indexed: 12/14/2022] Open
Abstract
Mammalian target of rapamycin (mTOR) is activated by numerous stimuli, including amino acids and growth factors. This kinase is part of the mTOR complex 1 (mTORC1) which regulates cell proliferation, differentiation, and autophagy. Active mTORC1 is located on lysosomes and has been reported to disassociate from the lysosomal surface in the absence of amino acids. Furthermore, mTORC1 activity has been linked to the vacuolar H+-ATPases (V-ATPases), the proton pumps responsible for lysosomal acidification; however, the exact role of the V-ATPases in mTORC1 signaling is not known. To elucidate the mechanisms involved in mTORC1 regulation by the V-ATPases, we used primary osteoclasts derived from mice carrying a point (R740S) mutation in the a3 subunit of the V-ATPase. In these cells, the mutant protein is expressed but the pump is not functional, resulting in higher lysosomal pH. By analyzing mTOR activation, mTOR/lysosome co-localization, and lysosomal positioning using confocal microscopy, fractionation, and ultrapure lysosomal purification methods, we demonstrate that in primary osteoclasts, mTOR is localized on the lysosomal surface even when mTOR activity is inhibited. Our findings reveal that mTOR targeting to the lysosome in osteoclasts is activity-independent, and that its disassociation from the lysosome during starvation is not universal.
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Affiliation(s)
- Andrew Wang
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | | | - Celeste Owen
- Centre for Modeling Human Disease, Samuel Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Bowen Gao
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada
| | - Paul N Corey
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada
| | - Pascal Tyrrell
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada.,Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
| | - John H Brumell
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Irina Voronov
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
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6
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Calmodulin interacts with Rab3D and modulates osteoclastic bone resorption. Sci Rep 2016; 6:37963. [PMID: 27897225 PMCID: PMC5126571 DOI: 10.1038/srep37963] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 11/03/2016] [Indexed: 11/09/2022] Open
Abstract
Calmodulin is a highly versatile protein that regulates intracellular calcium homeostasis and is involved in a variety of cellular functions including cardiac excitability, synaptic plasticity and signaling transduction. During osteoclastic bone resorption, calmodulin has been reported to concentrate at the ruffled border membrane of osteoclasts where it is thought to modulate bone resorption activity in response to calcium. Here we report an interaction between calmodulin and Rab3D, a small exocytic GTPase and established regulator osteoclastic bone resorption. Using yeast two-hybrid screening together with a series of protein-protein interaction studies, we show that calmodulin interacts with Rab3D in a calcium dependent manner. Consistently, expression of a calcium insensitive form of calmodulin (i.e. CaM1234) perturbs calmodulin-Rab3D interaction as monitored by bioluminescence resonance energy transfer (BRET) assays. In osteoclasts, calmodulin and Rab3D are constitutively co-expressed during RANKL-induced osteoclast differentiation, co-occupy plasma membrane fractions by differential gradient sedimentation assay and colocalise in the ruffled border as revealed by confocal microscopy. Further, functional blockade of calmodulin-Rab3D interaction by calmidazolium chloride coincides with an attenuation of osteoclastic bone resorption. Our data imply that calmodulin- Rab3D interaction is required for efficient bone resorption by osteoclasts in vitro.
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7
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Kwon JO, Lee YD, Kim H, Kim MK, Song MK, Lee ZH, Kim HH. Tetraspanin 7 regulates sealing zone formation and the bone-resorbing activity of osteoclasts. Biochem Biophys Res Commun 2016; 477:1078-1084. [PMID: 27416754 DOI: 10.1016/j.bbrc.2016.07.046] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 07/08/2016] [Indexed: 11/26/2022]
Abstract
Tetraspanin family proteins regulate morphology, motility, fusion, and signaling in various cell types. We investigated the role of the tetraspanin 7 (Tspan7) isoform in the differentiation and function of osteoclasts. Tspan7 was up-regulated during osteoclastogenesis. When Tspan7 expression was reduced in primary precursor cells by siRNA-mediated gene knock-down, the generation of multinuclear osteoclasts was not affected. However, a striking cytoskeletal abnormality was observed: the formation of the podosome belt structure was inhibited and the microtubular network were disrupted by Tspan7 knock-down. Decreases in acetylated microtubules and levels of phosphorylated Src and Pyk2 in Tspan7 knock-down cells supported the involvement of Tspan7 in cytoskeletal rearrangement signaling in osteoclasts. This cytoskeletal defect interfered with sealing zone formation and subsequently the bone-resorbing activity of mature osteoclasts on dentin surfaces. Our results suggest that Tspan7 plays an important role in cytoskeletal organization required for the bone-resorbing function of osteoclasts by regulating signaling to Src, Pyk2, and microtubules.
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Affiliation(s)
- Jun-Oh Kwon
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Yong Deok Lee
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Haemin Kim
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Min Kyung Kim
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Min-Kyoung Song
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Zang Hee Lee
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Hong-Hee Kim
- Department of Cell and Developmental Biology, BK21 Program and DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea.
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8
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Matsumoto T, Nagase Y, Hirose J, Tokuyama N, Yasui T, Kadono Y, Ueki K, Kadowaki T, Nakamura K, Tanaka S. Regulation of bone resorption and sealing zone formation in osteoclasts occurs through protein kinase B-mediated microtubule stabilization. J Bone Miner Res 2013; 28:1191-202. [PMID: 23239117 DOI: 10.1002/jbmr.1844] [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: 09/06/2012] [Revised: 11/09/2012] [Accepted: 11/29/2012] [Indexed: 01/16/2023]
Abstract
We investigated the role of protein kinase B (Akt), a downstream effector of phosphatidylinositol 3-kinase, in bone-resorbing activity of mature osteoclasts. Treatment with a specific Akt inhibitor disrupted sealing zone formation and decreased the bone-resorbing activity of osteoclasts. The normal microtubule structures were lost and the Akt inhibitor reduced the amount of acetylated tubulin, which reflects stabilized microtubules, whereas forced Akt activation by adenovirus vectors resulted in the opposite effect. Forced Akt activation increased the binding of the microtubule-associated protein adenomatous polyposis coli (APC), the APC-binding protein end-binding protein 1 (EB1) and dynactin, a dynein activator complex, with microtubules. Depletion of Akt1 and Akt2 resulted in a disconnection of APC/EB1 and a decrease in bone-resorbing activity along with reduced sealing zone formation, both of which were recovered upon the addition of LiCl, a glycogen synthase kinase-3β (GSK-3β) inhibitor. The Akt1 and Akt2 double-knockout mice exhibited osteosclerosis due to reduced bone resorption. These findings indicate that Akt controls the bone-resorbing activity of osteoclasts by stabilizing microtubules via a regulation of the binding of microtubule associated proteins.
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Affiliation(s)
- Takumi Matsumoto
- Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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9
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Prydz K, Tveit H, Vedeler A, Saraste J. Arrivals and departures at the plasma membrane: direct and indirect transport routes. Cell Tissue Res 2012; 352:5-20. [DOI: 10.1007/s00441-012-1409-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/14/2012] [Indexed: 12/21/2022]
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10
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Zaal KJM, Reid E, Mousavi K, Zhang T, Mehta A, Bugnard E, Sartorelli V, Ralston E. Who needs microtubules? Myogenic reorganization of MTOC, Golgi complex and ER exit sites persists despite lack of normal microtubule tracks. PLoS One 2011; 6:e29057. [PMID: 22216166 PMCID: PMC3246457 DOI: 10.1371/journal.pone.0029057] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 11/20/2011] [Indexed: 11/18/2022] Open
Abstract
A wave of structural reorganization involving centrosomes, microtubules, Golgi complex and ER exit sites takes place early during skeletal muscle differentiation and completely remodels the secretory pathway. The mechanism of these changes and their functional implications are still poorly understood, in large part because all changes occur seemingly simultaneously. In an effort to uncouple the reorganizations, we have used taxol, nocodazole, and the specific GSK3-β inhibitor DW12, to disrupt the dynamic microtubule network of differentiating cultures of the mouse skeletal muscle cell line C2. Despite strong effects on microtubules, cell shape and cell fusion, none of the treatments prevented early differentiation. Redistribution of centrosomal proteins, conditional on differentiation, was in fact increased by taxol and nocodazole and normal in DW12. Redistributions of Golgi complex and ER exit sites were incomplete but remained tightly linked under all circumstances, and conditional on centrosomal reorganization. We were therefore able to uncouple microtubule reorganization from the other events and to determine that centrosomal proteins lead the reorganization hierarchy. In addition, we have gained new insight into structural and functional aspects of the reorganization of microtubule nucleation during myogenesis.
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Affiliation(s)
- Kristien J M Zaal
- Light Imaging Section, Office of Science and Technology, National Institute of Arthritis, Musculoskeletal, and Skin Disease, National Institutes of Health, Bethesda, Maryland, USA.
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11
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Ye S, Fowler TW, Pavlos NJ, Ng PY, Liang K, Feng Y, Zheng M, Kurten R, Manolagas SC, Zhao H. LIS1 regulates osteoclast formation and function through its interactions with dynein/dynactin and Plekhm1. PLoS One 2011; 6:e27285. [PMID: 22073305 PMCID: PMC3207863 DOI: 10.1371/journal.pone.0027285] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 10/13/2011] [Indexed: 11/19/2022] Open
Abstract
Microtubule organization and lysosomal secretion are both critical for the activation and function of osteoclasts, highly specialized polykaryons that are responsible for bone resorption and skeletal homeostasis. Here, we have identified a novel interaction between microtubule regulator LIS1 and Plekhm1, a lysosome-associated protein implicated in osteoclast secretion. Decreasing LIS1 expression by shRNA dramatically attenuated osteoclast formation and function, as shown by a decreased number of mature osteoclasts differentiated from bone marrow macrophages, diminished resorption pits formation, and reduced level of CTx-I, a bone resorption marker. The ablated osteoclast formation in LIS1-depleted macrophages was associated with a significant decrease in macrophage proliferation, osteoclast survival and differentiation, which were caused by reduced activation of ERK and AKT by M-CSF, prolonged RANKL-induced JNK activation and declined expression of NFAT-c1, a master transcription factor of osteoclast differentiation. Consistent with its critical role in microtubule organization and dynein function in other cell types, we found that LIS1 binds to and colocalizes with dynein in osteoclasts. Loss of LIS1 led to disorganized microtubules and aberrant dynein function. More importantly, the depletion of LIS1 in osteoclasts inhibited the secretion of Cathepsin K, a crucial lysosomal hydrolase for bone degradation, and reduced the motility of osteoclast precursors. These results indicate that LIS1 is a previously unrecognized regulator of osteoclast formation, microtubule organization, and lysosomal secretion by virtue of its ability to modulate dynein function and Plekhm1.
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Affiliation(s)
- Shiqiao Ye
- Center for Osteoporosis and Metabolic Bone Diseases, Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Arkansas for Medical Sciences and the Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, United States of America
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12
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Akisaka T, Yoshida H, Takigawa T. Differential distribution of posttranslationally modified microtubules in osteoclasts. J Histochem Cytochem 2011; 59:630-8. [PMID: 21421796 DOI: 10.1369/0022155411405334] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The differential distribution of microtubules in osteoclasts in culture was examined by using antibodies against acetylated, tyrosinated, or detyrosinated tubulins. Tyrosinated tubulin was found throughout the cytoplasmic microtubules in all cells examined. An expanding protrusion that contained tyrosinated tubulin but none of the detyrosinated or acetylated form was seen in the immature osteoclasts. Detyrosinated or acetylated tubulin was detectable in the peripheral cytoplasm of the mature osteoclasts displaying the loss of the expanding protrusion. Although most of the microtubules were derived from the centrosome, noncentrosomal microtubules were distributed in the expanding protrusion, which was predominantly positive for tyrosinated tubulin. By tracing single microtubules, the authors found that their growing ends were always rich in tyrosinated tubulin subunits. End binding protein 1 bound preferentially to the microtubule ends. Both acetylated and tyrosinated microtubules were shown to be closely associated with podosomes. Microtubules appeared to grow over or into the podosomes; in addition, the growing ends of single microtubules could be observed to target the podosomes. Moreover, a microtubule-associated histone deacetylase 6 was localized in the podosomes of the osteoclast. On the basis of these results, the authors conclude that posttranslational modifications of microtubules may correlate with characteristic changes in podosome dynamics in osteoclasts.
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Affiliation(s)
- Toshitaka Akisaka
- Division of Oral Anatomy, Asahi University School of Dentistry, Mizuho, Gifu, Japan. mail:
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13
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Väänänen HK, Laitala-Leinonen T. Osteoclast lineage and function. Arch Biochem Biophys 2008; 473:132-8. [DOI: 10.1016/j.abb.2008.03.037] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 03/27/2008] [Accepted: 03/28/2008] [Indexed: 01/03/2023]
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14
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Mulari MT, Nars M, Laitala-Leinonen T, Kaisto T, Metsikkö K, Sun Y, Väänänen HK. Recombinant VSV G proteins reveal a novel raft-dependent endocytic pathway in resorbing osteoclasts. Exp Cell Res 2008; 314:1641-51. [DOI: 10.1016/j.yexcr.2008.02.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 02/10/2008] [Accepted: 02/15/2008] [Indexed: 10/22/2022]
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Oriolo AS, Wald FA, Ramsauer VP, Salas PJI. Intermediate filaments: a role in epithelial polarity. Exp Cell Res 2007; 313:2255-64. [PMID: 17425955 PMCID: PMC1986643 DOI: 10.1016/j.yexcr.2007.02.030] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 02/19/2007] [Accepted: 02/22/2007] [Indexed: 11/24/2022]
Abstract
Intermediate filaments have long been considered mechanical components of the cell that provide resistance to deformation stress. Practical experimental problems, including insolubility, lack of good pharmacological antagonists, and the paucity of powerful genetic models have handicapped the research of other functions. In single-layered epithelial cells, keratin intermediate filaments are cortical, either apically polarized or apico-lateral. This review analyzes phenotypes of genetic manipulations of simple epithelial cell keratins in mice and Caenorhabditis elegans that strongly suggest a role of keratins in apico-basal polarization and membrane traffic. Published evidence that intermediate filaments can act as scaffolds for proteins involved in membrane traffic and signaling is also discussed. Such a scaffolding function would generate a highly polarized compartment within the cytoplasm of simple epithelial cells. While in most cases mechanistic explanations for the keratin-null or overexpression phenotypes are still missing, it is hoped that investigators will be encouraged to study these as yet poorly understood functions of intermediate filaments.
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Affiliation(s)
- Andrea S Oriolo
- Department of Cell Biology and Anatomy, University of Miami, Miller School of Medicine, 1600 NW 10th Ave.-RMSB, Miami, FL 33136, USA
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Bartolini F, Gundersen GG. Generation of noncentrosomal microtubule arrays. J Cell Sci 2007; 119:4155-63. [PMID: 17038542 DOI: 10.1242/jcs.03227] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In most proliferating and migrating animal cells, the centrosome is the main site for microtubule (MT) nucleation and anchoring, leading to the formation of radial MT arrays in which MT minus ends are anchored at the centrosomes and plus ends extend to the cell periphery. By contrast, in most differentiated animal cell types, including muscle, epithelial and neuronal cells, as well as most fungi and vascular plant cells, MTs are arranged in noncentrosomal arrays that are non-radial. Recent studies suggest that these noncentrosomal MT arrays are generated by a three step process. The initial step involves formation of noncentrosomal MTs by distinct mechanisms depending on cell type: release from the centrosome, catalyzed nucleation at noncentrosomal sites or breakage of pre-existing MTs. The second step involves transport by MT motor proteins or treadmilling to sites of assembly. In the final step, the noncentrosomal MTs are rearranged into cell-type-specific arrays by bundling and/or capture at cortical sites, during which MTs acquire stability. Despite their relative stability, the final noncentrosomal MT arrays may still exhibit dynamic properties and in many cases can be remodeled.
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Oriolo AS, Wald FA, Canessa G, Salas PJ. GCP6 binds to intermediate filaments: a novel function of keratins in the organization of microtubules in epithelial cells. Mol Biol Cell 2006; 18:781-94. [PMID: 17182859 PMCID: PMC1805110 DOI: 10.1091/mbc.e06-03-0201] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In simple epithelial cells, attachment of microtubule-organizing centers (MTOCs) to intermediate filaments (IFs) enables their localization to the apical domain. It is released by cyclin-dependent kinase (Cdk)1 phosphorylation. Here, we identified a component of the gamma-tubulin ring complex, gamma-tubulin complex protein (GCP)6, as a keratin partner in yeast two-hybrid assays. This was validated by binding in vitro of both purified full-length HIS-tagged GCP6 and a GCP6(1397-1819) fragment to keratins, and pull-down with native IFs. Keratin binding was blocked by Cdk1-mediated phosphorylation of GCP6. GCP6 was apical in normal enterocytes but diffuse in K8-null cells. GCP6 knockdown with short hairpin RNAs (shRNAs) in CACO-2 cells resulted in gamma-tubulin signal scattered throughout the cytoplasm, microtubules (MTs) in the perinuclear and basal regions, and microtubule-nucleating activity localized deep in the cytoplasm. Expression of a small fragment GCP6(1397-1513) that competes binding to keratins in vitro displaced gamma-tubulin from the cytoskeleton and resulted in depolarization of gamma-tubulin and changes in the distribution of microtubules and microtubule nucleation sites. Expression of a full-length S1397D mutant in the Cdk1 phosphorylation site delocalized centrosomes. We conclude that GCP6 participates in the attachment of MTOCs to IFs in epithelial cells and is among the factors that determine the peculiar architecture of microtubules in polarized epithelia.
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Affiliation(s)
- Andrea S. Oriolo
- Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Flavia A. Wald
- Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Gisella Canessa
- Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Pedro J.I. Salas
- Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, FL 33136
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Okumura S, Mizoguchi T, Sato N, Yamaki M, Kobayashi Y, Yamauchi H, Ozawa H, Udagawa N, Takahashi N. Coordination of microtubules and the actin cytoskeleton is important in osteoclast function, but calcitonin disrupts sealing zones without affecting microtubule networks. Bone 2006; 39:684-93. [PMID: 16774853 DOI: 10.1016/j.bone.2006.04.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 03/07/2006] [Accepted: 04/04/2006] [Indexed: 01/28/2023]
Abstract
Bone-resorbing osteoclasts form sealing zones and ruffled borders toward the bone surface. The sealing zone consists of a ring-like alignment of F-actin dots and surrounds the ruffled border, from which protons are secreted into the bone surface. Vacuolar-type proton ATPase (V-ATPase) in osteoclasts is a ruffled border-associated enzyme responsible for the proton secretion. We studied the interaction between microtubules and the actin cytoskeleton in osteoclasts. Confocal microscopic observation revealed that osteoclasts on glass coverslips, dentine slices and Osteologictrade mark discs formed the ring-like structure of F-actin dots, and microtubules overlapped the top of the F-actin dots. Osteoclasts cultured on dentine formed resorption pits within 48 h. The treatment of osteoclasts with cytochalasin D, an F-actin-depolymerizing reagent, induced perturbation of the microtubules in osteoclasts on glass and inhibited their pit-forming activity on dentine in a dose-dependent and reversible manner. Conversely, nocodazole, a microtubule-depolymerizing reagent, disrupted sealing zones and inhibited pit-forming activity of osteoclasts in a dose-dependent and reversible manner. V-ATPase showed a tendency to be localized inside sealing zones in osteoclasts. Treatment of osteoclasts with calcitonin induced both disruption of sealing zones and dispersion of V-ATPase to the whole area of the cytoplasm within 60 min. The microtubule networks in osteoclasts remained unchanged for 60 min even in the presence of calcitonin. These results suggest that coordination of the actin cytoskeleton and microtubules is important in the function of osteoclasts, but calcitonin selectively affects the actin cytoskeleton and induces the dispersion of V-ATPase without causing significant changes in the microtubules.
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Affiliation(s)
- S Okumura
- Department of Biochemistry, Matsumoto Dental University, 1780 Hiro-oka Gobara, Shiojiri, Nagano 399-0781, Japan
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Bugnard E, Zaal KJM, Ralston E. Reorganization of microtubule nucleation during muscle differentiation. ACTA ACUST UNITED AC 2004; 60:1-13. [PMID: 15532031 DOI: 10.1002/cm.20042] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Skeletal muscle differentiation involves a complete reorganization of the microtubule network. Nearly 20 years ago, Tassin et al. [1985: J Cell Biol 100:35-46] suggested a mechanism for this reorganization by showing a redistribution of the microtubule organizing center from the centrosome to the nuclear membrane. Little progress has been made since. It is still not clear whether centrosomal proteins are redistributed together, whether microtubules are nucleated at the nuclear membrane or transported there post-nucleation, and whether gamma-tubulin (gammatub) remains necessary for nucleation in myotubes. To investigate these questions, we have examined the redistribution of the centrosomal proteins pericentrin (PC), gammatub, and ninein in the C2 muscle cell line. Immunofluorescence of differentiated myotubes shows PC along the nuclear membrane whereas gammatub is only detected there after pre-fixation detergent extraction. After expression of a GFP-tagged gammatub, we observe a weak fluorescence along the nuclear membrane, confirming the presence of gammatub at a low concentration relative to PC. Microinjection of anti-gammatub antibodies into myotubes blocks microtubule growth from both nuclear membranes and centrosomal sites. The centrosomal microtubule-anchoring protein, ninein, is found at the nuclear membrane as well and its distribution appears independent of microtubule integrity. We conclude that centrosomal proteins are redistributed independently during muscle differentiation, to sites that nucleate microtubules both along the nuclear membranes and through the cytoplasm.
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Affiliation(s)
- Elisabeth Bugnard
- Light Imaging Section, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA
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