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Chu A, Yao Y, Glibowicka M, Deber CM, Manolson MF. The Human Mutation K237_V238del in a Putative Lipid Binding Motif within the V-ATPase a2 Isoform Suggests a Molecular Mechanism Underlying Cutis Laxa. Int J Mol Sci 2024; 25:2170. [PMID: 38396846 PMCID: PMC10889665 DOI: 10.3390/ijms25042170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 01/19/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
Vacuolar ATPases (V-ATPases), proton pumps composed of 16 subunits, are necessary for a variety of cellular functions. Subunit "a" has four isoforms, a1-a4, each with a distinct cellular location. We identified a phosphoinositide (PIP) interaction motif, KXnK(R)IK(R), conserved in all four isoforms, and hypothesize that a/PIP interactions regulate V-ATPase recruitment/retention to different organelles. Among the four isoforms, a2 is enriched on Golgi with a2 mutations in the PIP motif resulting in cutis laxa. We hypothesize that the hydrophilic N-terminal (NT) domain of a2 contains a lipid-binding domain, and mutations in this domain prevent interaction with Golgi-enriched PIPs, resulting in cutis laxa. We recreated the cutis laxa-causing mutation K237_V238del, and a double mutation in the PIP-binding motif, K237A/V238A. Circular dichroism confirmed that there were no protein structure alterations. Pull-down assays with PIP-enriched liposomes revealed that wildtype a2NT preferentially binds phosphatidylinositol 4-phosphate (PI(4)P), while mutants decreased binding to PI(4)P. In HEK293 cells, wildtype a2NT was localized to Golgi and co-purified with microsomal membranes. Mutants reduced Golgi localization and membrane association. Rapamycin depletion of PI(4)P diminished a2NT-Golgi localization. We conclude that a2NT is sufficient for Golgi retention, suggesting the lipid-binding motif is involved in V-ATPase targeting and/or retention. Mutational analyses suggest a molecular mechanism underlying how a2 mutations result in cutis laxa.
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Affiliation(s)
- Anh Chu
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Miroslawa Glibowicka
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
| | - Charles M. Deber
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
| | - Morris F. Manolson
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
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Dobrewa W, Bielska M, Bąbol-Pokora K, Janczar S, Młynarski W. Congenital neutropenia: From lab bench to clinic bedside and back. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2024; 793:108476. [PMID: 37989463 DOI: 10.1016/j.mrrev.2023.108476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 11/11/2023] [Accepted: 11/12/2023] [Indexed: 11/23/2023]
Abstract
Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.
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Affiliation(s)
- Weronika Dobrewa
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 36\50 Sporna Str, 91-738 Lodz, Poland.
| | - Marta Bielska
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 36\50 Sporna Str, 91-738 Lodz, Poland
| | - Katarzyna Bąbol-Pokora
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 36\50 Sporna Str, 91-738 Lodz, Poland
| | - Szymon Janczar
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 36\50 Sporna Str, 91-738 Lodz, Poland
| | - Wojciech Młynarski
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, 36\50 Sporna Str, 91-738 Lodz, Poland.
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Ma Y, Xu Y, Zhang Y, Duan X. Molecular Mechanisms of Craniofacial and Dental Abnormalities in Osteopetrosis. Int J Mol Sci 2023; 24:10412. [PMID: 37373559 DOI: 10.3390/ijms241210412] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/14/2023] [Accepted: 06/15/2023] [Indexed: 06/29/2023] Open
Abstract
Osteopetrosis is a group of genetic bone disorders characterized by increased bone density and defective bone resorption. Osteopetrosis presents a series of clinical manifestations, including craniofacial deformities and dental problems. However, few previous reports have focused on the features of craniofacial and dental problems in osteopetrosis. In this review, we go through the clinical features, types, and related pathogenic genes of osteopetrosis. Then we summarize and describe the characteristics of craniofacial and dental abnormalities in osteopetrosis that have been published in PubMed from 1965 to the present. We found that all 13 types of osteopetrosis have craniomaxillofacial and dental phenotypes. The main pathogenic genes, such as chloride channel 7 gene (CLCN7), T cell immune regulator 1 (TCIRG1), osteopetrosis-associated transmembrane protein 1 (OSTM1), pleckstrin homology domain-containing protein family member 1 (PLEKHM1), and carbonic anhydrase II (CA2), and their molecular mechanisms involved in craniofacial and dental phenotypes, are discussed. We conclude that the telltale craniofacial and dental abnormalities are important for dentists and other clinicians in the diagnosis of osteopetrosis and other genetic bone diseases.
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Affiliation(s)
- Yu Ma
- College of Life Sciences, Northwest University, Xi'an 710069, China
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Disease, Shaanxi Key Laboratory of Stomatology, Department of Oral Biology & Clinic of Oral Rare Diseases and Genetic Diseases, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China
| | - Yali Xu
- College of Life Sciences, Northwest University, Xi'an 710069, China
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Disease, Shaanxi Key Laboratory of Stomatology, Department of Oral Biology & Clinic of Oral Rare Diseases and Genetic Diseases, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China
| | - Yanli Zhang
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Disease, Shaanxi Key Laboratory of Stomatology, Department of Oral Biology & Clinic of Oral Rare Diseases and Genetic Diseases, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China
| | - Xiaohong Duan
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Disease, Shaanxi Key Laboratory of Stomatology, Department of Oral Biology & Clinic of Oral Rare Diseases and Genetic Diseases, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China
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Capo V, Abinun M, Villa A. Osteoclast rich osteopetrosis due to defects in the TCIRG1 gene. Bone 2022; 165:116519. [PMID: 35981697 DOI: 10.1016/j.bone.2022.116519] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/10/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022]
Abstract
Discovery that mutations in TCIRG1 (also known as Atp6i) gene are responsible for most instances of autosomal recessive osteopetrosis (ARO) heralded a new era for comprehension and treatment of this phenotypically heterogeneous rare bone disease. TCIRG1 encodes the a3 subunit, an essential isoform of the vacuolar ATPase proton pump involved in acidification of the osteoclast resorption lacuna and in secretory lysosome trafficking. TCIRG1 defects lead to inefficient bone resorption by nonfunctional osteoclasts seen in abundance on bone marrow biopsy, delineating this ARO as 'osteoclast-rich'. Presentation is usually in early childhood and features of extramedullary haematopoiesis (hepatosplenomegaly, anaemia, thrombocytopenia) due to bone marrow fibrosis, and cranial nerve impingement (blindness in particular). Impaired dietary calcium uptake due to high pH causes the co-occurrence of rickets, described as "osteopetrorickets". Osteoclast dysfunction leads to early death if untreated, and allogeneic haematopoietic stem cell transplantation is currently the treatment of choice. Studies of patients as well as of mouse models carrying spontaneous (the oc/oc mouse) or targeted disruption of Atp6i (TCIRG1) gene have been instrumental providing insight into disease pathogenesis and development of novel cellular therapies that exploit gene correction.
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Affiliation(s)
- Valentina Capo
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy
| | - Mario Abinun
- Children's Haematopoietic Stem Cell Transplantation Unit, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Anna Villa
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy.
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Garneau AP, Slimani S, Haydock L, Nsimba-Batomene TR, Préfontaine FCM, Lavoie MM, Tremblay LE, Fiola MJ, Mac-Way F, Isenring P. Molecular mechanisms, physiological roles, and therapeutic implications of ion fluxes in bone cells: Emphasis on the cation-Cl - cotransporters. J Cell Physiol 2022; 237:4356-4368. [PMID: 36125923 PMCID: PMC10087713 DOI: 10.1002/jcp.30879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/25/2022] [Accepted: 09/01/2022] [Indexed: 11/11/2022]
Abstract
Bone turnover diseases are exceptionally prevalent in human and come with a high burden on physical health. While these diseases are associated with a variety of risk factors and causes, they are all characterized by common denominators, that is, abnormalities in the function or number of osteoblasts, osteoclasts, and/or osteocytes. As such, much effort has been deployed in the recent years to understand the signaling mechanisms of bone cell proliferation and differentiation with the objectives of exploiting the intermediates involved as therapeutic preys. Ion transport systems at the external and in the intracellular membranes of osteoblasts and osteoclasts also play an important role in bone turnover by coordinating the movement of Ca2+ , PO4 2- , and H+ ions in and out of the osseous matrix. Even if they sustain the terminal steps of osteoformation and osteoresorption, they have been the object of very little attention in the last several years. Members of the cation-Cl- cotransporter (CCC) family are among the systems at work as they are expressed in bone cells, are known to affect the activity of Ca2+ -, PO4 2- -, and H+ -dependent transport systems and have been linked to bone mass density variation in human. In this review, the roles played by the CCCs in bone remodeling will be discussed in light of recent developments and their potential relevance in the treatment of skeletal disorders.
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Affiliation(s)
- Alexandre P Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada.,Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, Inserm U1151, Université Paris Cité, rue de Sèvres, Paris, France
| | - Samira Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Ludwig Haydock
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | | | | | - Mathilde M Lavoie
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Laurence E Tremblay
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Marie-Jeanne Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Fabrice Mac-Way
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Paul Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
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Chu A, Zirngibl RA, Manolson MF. The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption. Int J Mol Sci 2021; 22:ijms22136934. [PMID: 34203247 PMCID: PMC8269383 DOI: 10.3390/ijms22136934] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 12/29/2022] Open
Abstract
This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.
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Guérit D, Marie P, Morel A, Maurin J, Verollet C, Raynaud-Messina B, Urbach S, Blangy A. Primary myeloid cell proteomics and transcriptomics: importance of β-tubulin isotypes for osteoclast function. J Cell Sci 2020; 133:jcs239772. [PMID: 32265273 DOI: 10.1242/jcs.239772] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 03/19/2020] [Indexed: 08/31/2023] Open
Abstract
Among hematopoietic cells, osteoclasts (OCs) and immature dendritic cells (DCs) are closely related myeloid cells with distinct functions: OCs participate skeleton maintenance while DCs sample the environment for foreign antigens. Such specificities rely on profound modifications of gene and protein expression during OC and DC differentiation. We provide global proteomic and transcriptomic analyses of primary mouse OCs and DCs, based on original stable isotope labeling with amino acids in cell culture (SILAC) and RNAseq data. We established specific signatures for OCs and DCs, including genes and proteins of unknown functions. In particular, we showed that OCs and DCs have the same α- and β-tubulin isotype repertoire but that OCs express much more of the β tubulin isotype Tubb6 (also known as TBB6). In both mouse and human OCs, we demonstrate that elevated expression of Tubb6 in OCs is necessary for correct podosomes organization and thus for the structure of the sealing zone, which sustains the bone resorption apparatus. Hence, lowering Tubb6 expression hinders OC resorption activity. Overall, we highlight here potential new regulators of OC and DC biology, and illustrate the functional importance of the tubulin isotype repertoire in the biology of differentiated cells.
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Affiliation(s)
- David Guérit
- 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
| | - Anne Morel
- 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
| | - Christel Verollet
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 31077 Toulouse Cedex 04, France
- International associated laboratory (LIA) CNRS 'IM-TB/HIV' (1167), 31077 Toulouse Cedex 04, France
- International associated laboratory (LIA) CNRS 'IM-TB/HIV' (1167), Buenos Aires C1425AUM, Argentina
| | - Brigitte Raynaud-Messina
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 31077 Toulouse Cedex 04, France
- International associated laboratory (LIA) CNRS 'IM-TB/HIV' (1167), 31077 Toulouse Cedex 04, France
- International associated laboratory (LIA) CNRS 'IM-TB/HIV' (1167), Buenos Aires C1425AUM, Argentina
| | - Serge Urbach
- Functional Proteomics Facility, Institute of Functional Genomics, Montpellier Univ., CNRS, 141 rue de la Cardonille, 34000 Montpellier, France
| | - Anne Blangy
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), Montpellier Univ., CNRS, 34000 Montpellier, France
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Tao SC, Guo SC. Extracellular vesicles in bone: "dogrobbers" in the "eternal battle field". Cell Commun Signal 2019; 17:6. [PMID: 30658653 PMCID: PMC6339294 DOI: 10.1186/s12964-019-0319-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 01/06/2019] [Indexed: 02/07/2023] Open
Abstract
Throughout human life, bone is constantly in a delicate dynamic equilibrium of synthesis and resorption, hosting finely-tuned bone mineral metabolic processes for bone homeostasis by collaboration or symphony among several cell types including osteoclasts (OCs), osteoblasts (OBs), osteocytes (OYs), vascular endothelial cells (ECs) and their precursors. Beyond these connections, a substantial level of communication seems to occur between bone and other tissues, and together, they form an organic unit linked to human health and disease. However, the current hypothesis, which includes growth factors, hormones and specific protein secretion, incompletely explains the close connections among bone cells or between bone and other tissues. Extracellular vesicles (EVs) are widely-distributed membrane structures consisting of lipid bilayers, membrane proteins and intravesicular cargo (including proteins and nucleic acids), ranging from 30 nm to 1000 nm in diameter, and their characters have been highly conserved throughout evolution. EVs have targeting abilities and the potential to transmit multidimensional, abundant and complicated information, as powerful and substantial "dogrobbers" mediating intercellular communications. As research has progressed, EVs have gradually become thought of as "dogrobbers" in bone tissue-the "eternal battle field" -in a delicate dynamic balance of destruction and reconstruction. In the current review, we give a brief description of the major constituent cells in bone tissues and explore the progress of current research on bone-derived EVs. In addition, this review also discusses in depth not only potential directions for future research to breakthrough in this area but also problems existing in current research that need to be solved for a better understanding of bone tissues.
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Affiliation(s)
- Shi-Cong Tao
- Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, China.
| | - Shang-Chun Guo
- Institute of Microsurgery on Extremities, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, China.
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Duan X, Yang S, Zhang L, Yang T. V-ATPases and osteoclasts: ambiguous future of V-ATPases inhibitors in osteoporosis. Theranostics 2018; 8:5379-5399. [PMID: 30555553 PMCID: PMC6276090 DOI: 10.7150/thno.28391] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 10/10/2018] [Indexed: 12/11/2022] Open
Abstract
Vacuolar ATPases (V-ATPases) play a critical role in regulating extracellular acidification of osteoclasts and bone resorption. The deficiencies of subunit a3 and d2 of V-ATPases result in increased bone density in humans and mice. One of the traditional drug design strategies in treating osteoporosis is the use of subunit a3 inhibitor. Recent findings connect subunits H and G1 with decreased bone density. Given the controversial effects of ATPase subunits on bone density, there is a critical need to review the subunits of V-ATPase in osteoclasts and their functions in regulating osteoclasts and bone remodeling. In this review, we comprehensively address the following areas: information about all V-ATPase subunits and their isoforms; summary of V-ATPase subunits associated with human genetic diseases; V-ATPase subunits and osteopetrosis/osteoporosis; screening of all V-ATPase subunits variants in GEFOS data and in-house data; spectrum of V-ATPase subunits during osteoclastogenesis; direct and indirect roles of subunits of V-ATPases in osteoclasts; V-ATPase-associated signaling pathways in osteoclasts; interactions among V-ATPase subunits in osteoclasts; osteoclast-specific V-ATPase inhibitors; perspective of future inhibitors or activators targeting V-ATPase subunits in the treatment of osteoporosis.
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Affiliation(s)
- Xiaohong Duan
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral Biology, Clinic of Oral Rare and Genetic Diseases, School of Stomatology, the Fourth Military Medical University, 145 West Changle Road, Xi'an 710032, P. R. China
| | - Shaoqing Yang
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral Biology, Clinic of Oral Rare and Genetic Diseases, School of Stomatology, the Fourth Military Medical University, 145 West Changle Road, Xi'an 710032, P. R. China
| | - Lei Zhang
- Center for Genetic Epidemiology and Genomics, School of Public Health, Medical College of Soochow University, 199 Renai Road, Suzhou, Jiangsu, P. R. China
| | - Tielin Yang
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, and Institute of Molecular Genetics, School of Life Science and Technology, Xi'an Jiaotong University, 28 West Xianning Road, Xi'an 710049, People's Republic of China
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Yang W, Han W, Qin A, Wang Z, Xu J, Qian Y. The emerging role of Hippo signaling pathway in regulating osteoclast formation. J Cell Physiol 2018; 233:4606-4617. [PMID: 29219182 DOI: 10.1002/jcp.26372] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/01/2017] [Indexed: 12/14/2022]
Abstract
A delicate balance between osteoblastic bone formation and osteoclastic bone resorption is crucial for bone homeostasis. This process is regulated by the Hippo signaling pathway including key regulatory molecules RASSF2, NF2, MST1/2, SAV1, LATS1/2, MOB1, YAP, and TAZ. It is well established that the Hippo signaling pathway plays an important part in regulating osteoblast differentiation, but its role in osteoclast formation and activation remains poorly understood. In this review, we discuss the emerging role of Hippo-signaling pathway in osteoclast formation and bone homeostasis. It is revealed that specific molecules of the Hippo-signaling pathway take part in a stage specific regulation in pre-osteoclast proliferation, osteoclast differentiation and osteoclast apoptosis and survival. Upon activation, MST and LAST, transcriptional co-activators YAP and TAZ bind to the members of the TEA domain (TEAD) family transcription factors, and influence osteoclast differentiation via regulating the expression of downstream target genes such as connective tissue growth factor (CTGF/CCN2) and cysteine-rich protein 61 (CYR61/CCN1). In addition, through interacting or cross talking with RANKL-mediated signaling cascades including NF-κB, MAPKs, AP1, and NFATc1, Hippo-signaling molecules such as YAP/TAZ/TEAD complex, RASSF2, MST2, and Ajuba could also potentially modulate osteoclast differentiation and function. Elucidating the roles of the Hippo-signaling pathway in osteoclast development and specific molecules involved is important for understanding the mechanism of bone homeostasis and diseases.
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Affiliation(s)
- Wanlei Yang
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital of Zhejiang University), Shaoxing, Zhejiang, P. R. China
| | - Weiqi Han
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital of Zhejiang University), Shaoxing, Zhejiang, P. R. China
| | - An Qin
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ziyi Wang
- School of Biomedical Sciences, The University of Western Australia, Perth, WA, Australia
| | - Jiake Xu
- School of Biomedical Sciences, The University of Western Australia, Perth, WA, Australia
| | - Yu Qian
- Department of Orthopaedics, Shaoxing People's Hospital (Shaoxing Hospital of Zhejiang University), Shaoxing, Zhejiang, P. R. China
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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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12
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Abstract
The vacuolar ATPases (V-ATPases) are a family of proton pumps that couple ATP hydrolysis to proton transport into intracellular compartments and across the plasma membrane. They function in a wide array of normal cellular processes, including membrane traffic, protein processing and degradation, and the coupled transport of small molecules, as well as such physiological processes as urinary acidification and bone resorption. The V-ATPases have also been implicated in a number of disease processes, including viral infection, renal disease, and bone resorption defects. This review is focused on the growing evidence for the important role of V-ATPases in cancer. This includes functions in cellular signaling (particularly Wnt, Notch, and mTOR signaling), cancer cell survival in the highly acidic environment of tumors, aiding the development of drug resistance, as well as crucial roles in tumor cell invasion, migration, and metastasis. Of greatest excitement is evidence that at least some tumors express isoforms of V-ATPase subunits whose disruption is not lethal, leading to the possibility of developing anti-cancer therapeutics that selectively target V-ATPases that function in cancer cells.
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Affiliation(s)
- Laura Stransky
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, and Program in Cellular and Molecular Physiology, Program in Biochemistry, and Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
| | - Kristina Cotter
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, and Program in Cellular and Molecular Physiology, Program in Biochemistry, and Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
| | - Michael Forgac
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, and Program in Cellular and Molecular Physiology, Program in Biochemistry, and Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
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13
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Johnson L, Ganss B, Wang A, Zirngibl RA, Johnson DE, Owen C, Bradley G, Voronov I. V-ATPases Containing a3 Subunit Play a Direct Role in Enamel Development in Mice. J Cell Biochem 2017; 118:3328-3340. [PMID: 28295540 DOI: 10.1002/jcb.25986] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/09/2017] [Indexed: 12/17/2022]
Abstract
Vacuolar H+ -ATPases (V-ATPases) are ubiquitous multisubunit proton pumps responsible for organellar pH maintenance. Mutations in the a3 subunit of V-ATPases cause autosomal recessive osteopetrosis, a rare disease due to impaired bone resorption. Patients with osteopetrosis also display dental anomalies, such as enamel defects; however, it is not clear whether these enamel abnormalities are a direct consequence of the a3 mutations. We investigated enamel mineralization, spatiotemporal expression of enamel matrix proteins and the a3 protein during tooth development using an osteopetrotic mouse model with a R740S point mutation in the V-ATPase a3 subunit. Histology revealed aberrations in both crown and root development, whereas SEM analysis demonstrated delayed enamel mineralization in homozygous animals. Enamel thickness and mineralization were significantly decreased in homozygous mice as determined by μCT analysis. The expression patterns of the enamel matrix proteins amelogenin, amelotin, and odontogenic ameloblast-associated protein (ODAM) suggested a delay in transition to the maturation stage in homozygous animals. Protein expression of the a3 subunit was detected in ameloblasts in all three genotypes, suggesting that a3-containing V-ATPases play a direct role in amelogenesis, and mutations in a3 delay transition from the secretory to the maturation stage, resulting in hypomineralized and hypoplastic enamel. J. Cell. Biochem. 118: 3328-3340, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Lisa Johnson
- Faculty of Dentistry, Department of Oral Pathology, University of Toronto, Toronto, Ontario, Canada.,Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Bernhard Ganss
- Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada.,Matrix Dynamics Group, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Andrew Wang
- Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Ralph A Zirngibl
- Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Danielle E Johnson
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Celeste Owen
- Centre for Modeling Human Disease, Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, Toronto, Ontario, Canada
| | - Grace Bradley
- Faculty of Dentistry, Department of Oral Pathology, University of Toronto, Toronto, Ontario, Canada
| | - Irina Voronov
- Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada
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14
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Tsukuba T, Sakai E, Nishishita K, Kadowaki T, Okamoto K. New functions of lysosomes in bone cells. J Oral Biosci 2017. [DOI: 10.1016/j.job.2017.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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15
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Hu Y, Carraro-Lacroix LR, Wang A, Owen C, Bajenova E, Corey PN, Brumell JH, Voronov I. Lysosomal pH Plays a Key Role in Regulation of mTOR Activity in Osteoclasts. J Cell Biochem 2016. [PMID: 26212375 DOI: 10.1002/jcb.25287] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian target of rapamycin (mTOR) is a serine/threonine kinase involved in the regulation of cell growth. It has been shown to play an important role in osteoclast differentiation, particularly at the earlier stages of osteoclastogenesis. mTOR activation and function, as part of mTORC1 complex, is dependent on lysosomal localization and the vacuolar H(+) -ATPase (V-ATPase) activity; however, the precise mechanism is still not well understood. Using primary mouse osteoclasts that are known to have higher lysosomal pH due to R740S mutation in the V-ATPase a3 subunit, we investigated the role of lysosomal pH in mTORC1 signaling. Our results demonstrated that +/R740S cells had increased basal mTOR protein levels and mTORC1 activity compared to +/+ osteoclasts, while mTOR gene expression was decreased. Treatment with lysosomal inhibitors chloroquine and ammonium chloride, compounds known to raise lysosomal pH, significantly increased mTOR protein levels in +/+ cells, confirming the importance of lysosomal pH in mTOR signaling. These results also suggested that mTOR could be degraded in the lysosome. To test this hypothesis, we cultured osteoclasts with chloroquine or proteasomal inhibitor MG132. Both chloroquine and MG132 increased mTOR and p-mTOR protein levels in +/+ osteoclasts, suggesting that mTOR undergoes both lysosomal and proteasomal degradation. Treatment with cycloheximide, an inhibitor of new protein synthesis, confirmed that mTOR is constitutively expressed and degraded. These results show that, in osteoclasts, the lysosome plays a key role not only in mTOR activation but also in its deactivation through protein degradation, representing a novel molecular mechanism of mTOR regulation.
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Affiliation(s)
- Yingwei Hu
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.,Institute of Dental Medicine, Qilu Hospital, Shandong University, Jinan, China
| | | | - Andrew Wang
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Celeste Owen
- Centre for Modeling Human Disease, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Elena Bajenova
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Paul N Corey
- Dalla Lana School of Public Health, 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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16
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Aldrich LN, Kuo SY, Castoreno AB, Goel G, Kuballa P, Rees MG, Seashore-Ludlow BA, Cheah JH, Latorre IJ, Schreiber SL, Shamji AF, Xavier RJ. Discovery of a Small-Molecule Probe for V-ATPase Function. J Am Chem Soc 2015; 137:5563-8. [PMID: 25860544 PMCID: PMC4416280 DOI: 10.1021/jacs.5b02150] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
Lysosomes perform
a critical cellular function as a site of degradation
for diverse cargoes including proteins, organelles, and pathogens
delivered through distinct pathways, and defects in lysosomal function
have been implicated in a number of diseases. Recent studies have
elucidated roles for the lysosome in the regulation of protein synthesis,
metabolism, membrane integrity, and other processes involved in homeostasis.
Complex small-molecule natural products have greatly contributed to
the investigation of lysosomal function in cellular physiology. Here
we report the discovery of a novel, small-molecule modulator of lysosomal
acidification derived from diversity-oriented synthesis through high-content
screening.
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Affiliation(s)
- Leslie N Aldrich
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.,‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Szu-Yu Kuo
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States.,§Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Adam B Castoreno
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Gautam Goel
- ∥Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States.,⊥Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, United States.,#Program in Medical and Population Genetics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Petric Kuballa
- ∥Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States.,⊥Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, United States.,#Program in Medical and Population Genetics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Matthew G Rees
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Brinton A Seashore-Ludlow
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Jaime H Cheah
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Isabel J Latorre
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Stuart L Schreiber
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.,‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States.,∇Howard Hughes Medical Institute, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Alykhan F Shamji
- ‡Center for the Science of Therapeutics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
| | - Ramnik J Xavier
- ∥Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States.,⊥Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, United States.,#Program in Medical and Population Genetics, Broad Institute, 415 Main Street, Cambridge, Massachusetts 02142, United States
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17
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Sobacchi C, Pangrazio A, Lopez AGM, Gomez DPV, Caldana ME, Susani L, Vezzoni P, Villa A. As little as needed: the extraordinary case of a mild recessive osteopetrosis owing to a novel splicing hypomorphic mutation in the TCIRG1 gene. J Bone Miner Res 2014; 29:1646-50. [PMID: 24535816 PMCID: PMC4258090 DOI: 10.1002/jbmr.2203] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/23/2014] [Accepted: 02/09/2014] [Indexed: 01/22/2023]
Abstract
Mutations in the TCIRG1 gene, coding for a subunit of the osteoclast proton pump, are responsible for more than 50% of cases of human malignant autosomal recessive osteopetrosis (ARO), a rare inherited bone disease with increased bone density owing to a failure in bone resorption. A wide variety of mutations has been described, including missense, nonsense, small deletions/insertions, splice-site mutations, and large genomic deletions, all leading to a similar severe presentation. So far, to the best of our knowledge, no report of a mild phenotype owing to recessive TCIRG1 mutations is present neither in our series of more than 100 TCIRG1-dependent ARO patients nor in the literature. Here we describe an 8-year-old patient referred to us with a clinical diagnosis of ARO, based on radiological findings; of note, no neurological or hematological defects were present in this girl. Surprisingly, we identified a novel nucleotide change in intron 15 of the TCIRG1 gene at the homozygous state, leading to the production of multiple aberrant transcripts, but also, more importantly, of a limited amount of the normal transcript. Our results show that a low level of normal TCIRG1 protein can dampen the clinical presentation of TCIRG1-dependent ARO. On this basis, a small amount of protein might be sufficient to rescue, at least partially, the severe ARO phenotype, and this is particularly important when gene therapy approaches are considered. In addition, we would also recommend that the TCIRG1 gene be included in the molecular diagnosis of mild forms of human ARO.
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Affiliation(s)
- Cristina Sobacchi
- Unitá Operativa di Supporto (UOS)/Institute of Genetic and Biomedical Research (IRGB), Milan Unit, National Research Council (CNR), Milan, Italy; Humanitas Clinical and Research Center, Rozzano, Italy
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18
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Makaryan V, Rosenthal EA, Bolyard AA, Kelley ML, Below JE, Bamshad MJ, Bofferding KM, Smith JD, Buckingham K, Boxer LA, Skokowa J, Welte K, Nickerson DA, Jarvik GP, Dale DC. TCIRG1-associated congenital neutropenia. Hum Mutat 2014; 35:824-7. [PMID: 24753205 DOI: 10.1002/humu.22563] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 03/28/2014] [Indexed: 11/12/2022]
Abstract
Severe congenital neutropenia (SCN) is a rare hematopoietic disorder, with estimated incidence of 1 in 200,000 individuals of European descent, many cases of which are inherited in an autosomal dominant pattern. Despite the fact that several causal genes have been identified, the genetic basis for >30% of cases remains unknown. We report a five-generation family segregating a novel single nucleotide variant (SNV) in TCIRG1. There is perfect cosegregation of the SNV with congenital neutropenia in this family; all 11 affected, but none of the unaffected, individuals carry this novel SNV. Western blot analysis show reduced levels of TCIRG1 protein in affected individuals, compared to healthy controls. Two unrelated patients with SCN, identified by independent investigators, are heterozygous for different, rare, highly conserved, coding variants in TCIRG1.
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Affiliation(s)
- Vahagn Makaryan
- Department of Medicine, Divisions of GIM, University of Washington, Seattle, Washington
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19
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Ochotny N, Voronov I, Owen C, Aubin JE, Manolson MF. The R740S mutation in the V-ATPase a3 subunit results in osteoclast apoptosis and defective early-stage autophagy. J Cell Biochem 2013; 114:2823-33. [DOI: 10.1002/jcb.24630] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 07/22/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Noelle Ochotny
- Faculty of Dentistry; Dental Research Institute; University of Toronto; Toronto; Ontario; Canada
| | - Irina Voronov
- Faculty of Dentistry; Dental Research Institute; University of Toronto; Toronto; Ontario; Canada
| | - Celeste Owen
- Centre for Modeling Human Disease; Samuel Lunenfeld Research Institute; Mt. Sinai Hospital; Toronto; Ontario; Canada
| | | | - Morris F. Manolson
- Faculty of Dentistry; Dental Research Institute; University of Toronto; Toronto; Ontario; Canada
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20
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Sobacchi C, Schulz A, Coxon FP, Villa A, Helfrich MH. Osteopetrosis: genetics, treatment and new insights into osteoclast function. Nat Rev Endocrinol 2013; 9:522-36. [PMID: 23877423 DOI: 10.1038/nrendo.2013.137] [Citation(s) in RCA: 363] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Osteopetrosis is a genetic condition of increased bone mass, which is caused by defects in osteoclast formation and function. Both autosomal recessive and autosomal dominant forms exist, but this Review focuses on autosomal recessive osteopetrosis (ARO), also known as malignant infantile osteopetrosis. The genetic basis of this disease is now largely uncovered: mutations in TCIRG1, CLCN7, OSTM1, SNX10 and PLEKHM1 lead to osteoclast-rich ARO (in which osteoclasts are abundant but have severely impaired resorptive function), whereas mutations in TNFSF11 and TNFRSF11A lead to osteoclast-poor ARO. In osteoclast-rich ARO, impaired endosomal and lysosomal vesicle trafficking results in defective osteoclast ruffled-border formation and, hence, the inability to resorb bone and mineralized cartilage. ARO presents soon after birth and can be fatal if left untreated. However, the disease is heterogeneous in clinical presentation and often misdiagnosed. This article describes the genetics of ARO and discusses the diagnostic role of next-generation sequencing methods. The management of affected patients, including guidelines for the indication of haematopoietic stem cell transplantation (which can provide a cure for many types of ARO), are outlined. Finally, novel treatments, including preclinical data on in utero stem cell treatment, RANKL replacement therapy and denosumab therapy for hypercalcaemia are also discussed.
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Affiliation(s)
- Cristina Sobacchi
- Unit Of Support/Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Humanitas Clinical and Research Centre, Via Manzoni 113, 20089 Rozzano, Italy
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21
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Crasto GJ, Kartner N, Yao Y, Li K, Bullock L, Datti A, Manolson MF. Luteolin inhibition of V-ATPasea3-d2interaction decreases osteoclast resorptive activity. J Cell Biochem 2013; 114:929-41. [DOI: 10.1002/jcb.24434] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 10/22/2012] [Indexed: 01/14/2023]
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22
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Voronov I, Ochotny N, Jaumouillé V, Owen C, Manolson MF, Aubin JE. The R740S mutation in the V-ATPase a3 subunit increases lysosomal pH, impairs NFATc1 translocation, and decreases in vitro osteoclastogenesis. J Bone Miner Res 2013; 28:108-18. [PMID: 22865292 DOI: 10.1002/jbmr.1727] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 06/07/2012] [Accepted: 07/16/2012] [Indexed: 01/04/2023]
Abstract
Vacuolar H(+) -ATPase (V-ATPase), a multisubunit enzyme located at the ruffled border and in lysosomes of osteoclasts, is necessary for bone resorption. We previously showed that heterozygous mice with an R740S mutation in the a3 subunit of V-ATPase (+/R740S) have mild osteopetrosis resulting from an ∼90% reduction in proton translocation across osteoclast membranes. Here we show that lysosomal pH is also higher in +/R740S compared with wild-type (+/+) osteoclasts. Both osteoclast number and size were decreased in cultures of +/R740S compared with +/+ bone marrow cells, with concomitant decreased expression of key osteoclast markers (TRAP, cathepsin K, OSCAR, DC-STAMP, and NFATc1), suggesting that low lysosomal pH plays an important role in osteoclastogenesis. To elucidate the molecular mechanism of this inhibition, NFATc1 activation was assessed. NFATc1 nuclear translocation was significantly reduced in +/R740S compared with +/+ cells; however, this was not because of impaired enzymatic activity of calcineurin, the phosphatase responsible for NFATc1 dephosphorylation. Protein and RNA expression levels of regulator of calcineurin 1 (RCAN1), an endogenous inhibitor of NFATc1 activation and a protein degraded in lysosomes, were not significantly different between +/R740S and +/+ osteoclasts, but the RCAN1/NFATc1 ratio was significantly higher in +/R740S versus +/+ cells. The lysosomal inhibitor chloroquine significantly increased RCAN1 accumulation in +/+ cells, consistent with the hypothesis that higher lysosomal pH impairs RCAN1 degradation, leading to a higher RCAN1/NFATc1 ratio and consequently NFATc1 inhibition. Our data indicate that increased lysosomal pH in osteoclasts leads to decreased NFATc1 signaling and nuclear translocation, resulting in a cell autonomous impairment of osteoclastogenesis in vitro.
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Affiliation(s)
- Irina Voronov
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
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23
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Omi, a recessive mutation on chromosome 10, is a novel allele of Ostm1. Mamm Genome 2012; 24:44-53. [PMID: 23160729 PMCID: PMC3560959 DOI: 10.1007/s00335-012-9438-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 09/11/2012] [Indexed: 10/28/2022]
Abstract
Large-scale N-ethyl-N-nitrosourea (ENU) mutagenesis has provided many rodent models for human disease. Here we describe the initial characterization and mapping of a recessive mutation that leads to degeneration of the incisors, failure of molars to erupt, a grey coat colour, and mild osteopetrosis. We mapped the omi mutation to chromosome 10 between D10Mit214 and D10Mit194. The Ostm1 gene is a likely candidate gene in this region and the grey-lethal allele, Ostm1 ( gl ), and omi mutations fail to complement each other. We show that om/om mice have reduced levels of Ostm1 protein. To date we have not been able to identify the causative mutation. We propose that omi is a novel hypomorphic mutation affecting Ostm1 expression, potentially in a regulatory element.
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24
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Bhargava A, Voronov I, Wang Y, Glogauer M, Kartner N, Manolson MF. Osteopetrosis mutation R444L causes endoplasmic reticulum retention and misprocessing of vacuolar H+-ATPase a3 subunit. J Biol Chem 2012; 287:26829-39. [PMID: 22685294 DOI: 10.1074/jbc.m112.345702] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Osteopetrosis is a genetic bone disease characterized by increased bone density and fragility. The R444L missense mutation in the human V-ATPase a3 subunit (TCIRG1) is one of several known mutations in a3 and other proteins that can cause this disease. The autosomal recessive R444L mutation results in a particularly malignant form of infantile osteopetrosis that is lethal in infancy, or early childhood. We have studied this mutation using the pMSCV retroviral vector system to integrate the cDNA construct for green fluorescent protein (GFP)-fused a3(R445L) mutant protein into the RAW 264.7 mouse osteoclast differentiation model. In comparison with wild-type a3, the mutant glycoprotein localized to the ER instead of lysosomes and its oligosaccharide moiety was misprocessed, suggesting inability of the core-glycosylated glycoprotein to traffic to the Golgi. Reduced steady-state expression of the mutant protein, in comparison with wild type, suggested that the former was being degraded, likely through the endoplasmic reticulum-associated degradation pathway. In differentiated osteoclasts, a3(R445L) was found to degrade at an increased rate over the course of osteoclastogenesis. Limited proteolysis studies suggested that the R445L mutation alters mouse a3 protein conformation. Together, these data suggest that Arg-445 plays a role in protein folding, or stability, and that infantile malignant osteopetrosis caused by the R444L mutation in the human V-ATPase a3 subunit is another member of the growing class of protein folding diseases. This may have implications for early-intervention treatment, using protein rescue strategies.
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Affiliation(s)
- Ajay Bhargava
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1G6, Canada
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25
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Qin A, Cheng TS, Pavlos NJ, Lin Z, Dai KR, Zheng MH. V-ATPases in osteoclasts: structure, function and potential inhibitors of bone resorption. Int J Biochem Cell Biol 2012; 44:1422-35. [PMID: 22652318 DOI: 10.1016/j.biocel.2012.05.014] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 05/18/2012] [Accepted: 05/18/2012] [Indexed: 01/06/2023]
Abstract
The vacuolar-type H(+)-ATPase (V-ATPase) proton pump is a macromolecular complex composed of at least 14 subunits organized into two functional domains, V(1) and V(0). The complex is located on the ruffled border plasma membrane of bone-resorbing osteoclasts, mediating extracellular acidification for bone demineralization during bone resorption. Genetic studies from mice to man implicate a critical role for V-ATPase subunits in osteoclast-related diseases including osteopetrosis and osteoporosis. Thus, the V-ATPase complex is a potential molecular target for the development of novel anti-resorptive agents useful for the treatment of osteolytic diseases. Here, we review the current structure and function of V-ATPase subunits, emphasizing their exquisite roles in osteoclastic function. In addition, we compare several distinct classes of V-ATPase inhibitors with specific inhibitory effects on osteoclasts. Understanding the structure-function relationship of the osteoclast V-ATPase may lead to the development of osteoclast-specific V-ATPase inhibitors that may serve as alternative therapies for the treatment of osteolytic diseases.
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Affiliation(s)
- A Qin
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Crawley, Australia.
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Chan CY, Prudom C, Raines SM, Charkhzarrin S, Melman SD, De Haro LP, Allen C, Lee SA, Sklar LA, Parra KJ. Inhibitors of V-ATPase proton transport reveal uncoupling functions of tether linking cytosolic and membrane domains of V0 subunit a (Vph1p). J Biol Chem 2012; 287:10236-10250. [PMID: 22215674 DOI: 10.1074/jbc.m111.321133] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are important for many cellular processes, as they regulate pH by pumping cytosolic protons into intracellular organelles. The cytoplasm is acidified when V-ATPase is inhibited; thus we conducted a high-throughput screen of a chemical library to search for compounds that acidify the yeast cytosol in vivo using pHluorin-based flow cytometry. Two inhibitors, alexidine dihydrochloride (EC(50) = 39 μM) and thonzonium bromide (EC(50) = 69 μM), prevented ATP-dependent proton transport in purified vacuolar membranes. They acidified the yeast cytosol and caused pH-sensitive growth defects typical of V-ATPase mutants (vma phenotype). At concentrations greater than 10 μM the inhibitors were cytotoxic, even at the permissive pH (pH 5.0). Membrane fractions treated with alexidine dihydrochloride and thonzonium bromide fully retained concanamycin A-sensitive ATPase activity despite the fact that proton translocation was inhibited by 80-90%, indicating that V-ATPases were uncoupled. Mutant V-ATPase membranes lacking residues 362-407 of the tether of Vph1p subunit a of V(0) were resistant to thonzonium bromide but not to alexidine dihydrochloride, suggesting that this conserved sequence confers uncoupling potential to V(1)V(0) complexes and that alexidine dihydrochloride uncouples the enzyme by a different mechanism. The inhibitors also uncoupled the Candida albicans enzyme and prevented cell growth, showing further specificity for V-ATPases. Thus, a new class of V-ATPase inhibitors (uncouplers), which are not simply ionophores, provided new insights into the enzyme mechanism and original evidence supporting the hypothesis that V-ATPases may not be optimally coupled in vivo. The consequences of uncoupling V-ATPases in vivo as potential drug targets are discussed.
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Affiliation(s)
- Chun-Yuan Chan
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Catherine Prudom
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Summer M Raines
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Sahba Charkhzarrin
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Sandra D Melman
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Leyma P De Haro
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Chris Allen
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Samuel A Lee
- Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Larry A Sklar
- Center for Molecular Discovery, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131; Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131.
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Qin A, Cheng TS, Lin Z, Pavlos NJ, Jiang Q, Xu J, Dai KR, Zheng MH. Versatile roles of V-ATPases accessory subunit Ac45 in osteoclast formation and function. PLoS One 2011; 6:e27155. [PMID: 22087256 PMCID: PMC3210823 DOI: 10.1371/journal.pone.0027155] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 10/11/2011] [Indexed: 11/25/2022] Open
Abstract
Vacuolar-type H(+)-ATPases (V-ATPases) are macromolecular proton pumps that acidify intracellular cargos and deliver protons across the plasma membrane of a variety of specialized cells, including bone-resorbing osteoclasts. Extracellular acidification is crucial for osteoclastic bone resorption, a process that initiates the dissolution of mineralized bone matrix. While the importance of V-ATPases in osteoclastic resorptive function is well-defined, whether V-ATPases facilitate additional aspects of osteoclast function and/or formation remains largely obscure. Here we report that the V-ATPase accessory subunit Ac45 participates in both osteoclast formation and function. Using a siRNA-based approach, we show that targeted suppression of Ac45 impairs intracellular acidification and endocytosis, both are prerequisite for osteoclastic bone resorptive function in vitro. Interestingly, we find that knockdown of Ac45 also attenuates osteoclastogenesis owing to a reduced fusion capacity of osteoclastic precursor cells. Finally, in an effort to gain more detailed insights into the functional role of Ac45 in osteoclasts, we attempted to generate osteoclast-specific Ac45 conditional knockout mice using a Cathepsin K-Cre-LoxP system. Surprisingly, however, insertion of the neomycin cassette in the Ac45-Flox(Neo) mice resulted in marked disturbances in CNS development and ensuing embryonic lethality thus precluding functional assessment of Ac45 in osteoclasts and peripheral bone tissues. Based on these unexpected findings we propose that, in addition to its canonical function in V-ATPase-mediated acidification, Ac45 plays versatile roles during osteoclast formation and function.
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Affiliation(s)
- An Qin
- Shanghai Key Laboratory of Orthopaedic Implant, Department of Orthopaedics, Shanghai Jiao Tong University School of Medicine, Ninth People's Hospital, Shanghai, The People's Republic of China
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - Tak S. Cheng
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - Zhen Lin
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
- Division of Orthopaedic, Department of Surgery, Guangdong Academy of Medical Sciences, Guangdong General Hospital, Guangdong, The People's Republic of China
| | - Nathan J. Pavlos
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
| | - Qing Jiang
- Australian-China Joint Centre for Bone and Joint Research, Model Animal Research Centre of Nanjing University, Nanjing, The People's Republic of China
- The Center of Diagnosis and Treatment for Joint Disease, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, The People's Republic of China
| | - Jiake Xu
- School of Pathology and Laboratory Medicine, The University of Western Australia, Perth, Australia
| | - Ke R. Dai
- Shanghai Key Laboratory of Orthopaedic Implant, Department of Orthopaedics, Shanghai Jiao Tong University School of Medicine, Ninth People's Hospital, Shanghai, The People's Republic of China
- Orthopaedic Cellular and Molecular Biology Laboratory, Institute of Health Sciences, School of Medicine, Chinese Academy of Sciences, Shanghai Jiao Tong University, Shanghai, The People's Republic of China
| | - Ming H. Zheng
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Perth, Australia
- Australian-China Joint Centre for Bone and Joint Research, Model Animal Research Centre of Nanjing University, Nanjing, The People's Republic of China
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28
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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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Affiliation(s)
- Cameron C Scott
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
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