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Shinwari K, Rehman HM, Liu G, Bolkov MA, Tuzankina IA, Chereshnev VA. Novel Disease-Associated Missense Single-Nucleotide Polymorphisms Variants Predication by Algorithms Tools and Molecular Dynamics Simulation of Human TCIRG1 Gene Causing Congenital Neutropenia and Osteopetrosis. Front Mol Biosci 2022; 9:879875. [PMID: 35573728 PMCID: PMC9095858 DOI: 10.3389/fmolb.2022.879875] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 04/04/2022] [Indexed: 12/16/2022] Open
Abstract
T Cell Immune Regulator 1, ATPase H + Transporting V0 Subunit A3 (TCIRG1 gene provides instructions for making one part, the a3 subunit, of a large protein complex known as a vacuolar H + -ATPase (V-ATPase). V-ATPases are a group of similar complexes that act as pumps to move positively charged hydrogen atoms (protons) across membranes. Single amino acid changes in highly conserved areas of the TCIRG1 protein have been linked to autosomal recessive osteopetrosis and severe congenital neutropenia. We used multiple computational approaches to classify disease-prone single nucleotide polymorphisms (SNPs) in TCIRG1. We used molecular dynamics analysis to identify the deleterious nsSNPs, build mutant protein structures, and assess the impact of mutation. Our results show that fifteen nsSNPs (rs199902030, rs200149541, rs372499913, rs267605221, rs374941368, rs375717418, rs80008675, rs149792489, rs116675104, rs121908250, rs121908251, rs121908251, rs149792489 and rs116675104) variants are likely to be highly deleterious mutations as by incorporating them into wild protein they destabilize the wild protein structure and function. They are also located in the V-ATPase I domain, which may destabilize the structure and impair TCIRG1 protein activation, as well as reduce its ATPase effectiveness. These mutants have not yet been identified in patients suffering from CN and osteopetrosis while (G405R, R444L, and D517N) reported in our study are already associated with osteopetrosis. Mutation V52L reported in our study was identified in a patient suspected for CN. Finally, these mutants can help to further understand the broad pool of illness susceptibilities associated with TCIRG1 catalytic kinase domain activation and aid in the development of an effective treatment for associated diseases.
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Affiliation(s)
- Khyber Shinwari
- Institute of Chemical Engineering, Department of Immunochemistry, Ural Federal University, Yekaterinburg, Russia
- *Correspondence: Khyber Shinwari,
| | - Hafiz Muzzammel Rehman
- School of Biochemistry and Biotechnology, University of the Punjab, Lahore, Pakistan
- Alnoorians Group of Institutes, Shad Bagh, Lahore, Pakistan
| | - Guojun Liu
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, China
| | - Mikhail A. Bolkov
- Institute of Chemical Engineering, Department of Immunochemistry, Ural Federal University, Yekaterinburg, Russia
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Irina A. Tuzankina
- Institute of Chemical Engineering, Department of Immunochemistry, Ural Federal University, Yekaterinburg, Russia
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
| | - Valery. A. Chereshnev
- Institute of Chemical Engineering, Department of Immunochemistry, Ural Federal University, Yekaterinburg, Russia
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia
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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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Santos-Pereira C, Rodrigues LR, Côrte-Real M. Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities. Med Res Rev 2021; 41:1927-1964. [PMID: 33483985 DOI: 10.1002/med.21782] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/05/2020] [Accepted: 01/05/2021] [Indexed: 12/13/2022]
Abstract
The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.
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Affiliation(s)
- Cátia Santos-Pereira
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal.,Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Lígia R Rodrigues
- Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Manuela Côrte-Real
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal
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Vacher J, Bruccoleri M, Pata M. Ostm1 from Mouse to Human: Insights into Osteoclast Maturation. Int J Mol Sci 2020; 21:ijms21165600. [PMID: 32764302 PMCID: PMC7460669 DOI: 10.3390/ijms21165600] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 07/29/2020] [Accepted: 08/04/2020] [Indexed: 12/14/2022] Open
Abstract
The maintenance of bone mass is a dynamic process that requires a strict balance between bone formation and resorption. Bone formation is controlled by osteoblasts, while osteoclasts are responsible for resorption of the bone matrix. The opposite functions of these cell types have to be tightly regulated not only during normal bone development, but also during adult life, to maintain serum calcium homeostasis and sustain bone integrity to prevent bone fractures. Disruption of the control of bone synthesis or resorption can lead to an over accumulation of bone tissue in osteopetrosis or conversely to a net depletion of the bone mass in osteoporosis. Moreover, high levels of bone resorption with focal bone formation can cause Paget’s disease. Here, we summarize the steps toward isolation and characterization of the osteopetrosis associated trans-membrane protein 1 (Ostm1) gene and protein, essential for proper osteoclast maturation, and responsible when mutated for the most severe form of osteopetrosis in mice and humans.
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Affiliation(s)
- Jean Vacher
- Institut de Recherches Cliniques de Montreal (IRCM), Montreal, QC H2W 1R7, Canada; (M.B.); (M.P.)
- Departement de Medecine, Universite de Montreal, Montreal, QC H2W 1R7, Canada
- Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, QC H3A 1A3, Canada
- Correspondence:
| | - Michael Bruccoleri
- Institut de Recherches Cliniques de Montreal (IRCM), Montreal, QC H2W 1R7, Canada; (M.B.); (M.P.)
- Departement de Medecine, Universite de Montreal, Montreal, QC H2W 1R7, Canada
| | - Monica Pata
- Institut de Recherches Cliniques de Montreal (IRCM), Montreal, QC H2W 1R7, Canada; (M.B.); (M.P.)
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Zhang Y, Yang X, He X, Liu H, Guo P, Liu X, Xiao Y, Feng X, Wang Y, Li L. A novel mutation of the ITGB2 gene in a Chinese Zhuang minority patient with leukocyte adhesion deficiency type 1 and glucose-6-phosphate dehydrogenase deficiency. Gene 2019; 715:144027. [PMID: 31374327 DOI: 10.1016/j.gene.2019.144027] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 07/29/2019] [Accepted: 07/29/2019] [Indexed: 12/25/2022]
Abstract
OBJECTIVES To explore the clinical and molecular characteristics of a Chinese Zhuang minority patient with leukocyte adhesion deficiency type-1 (LAD-1) and glucose-6-phosphate dehydrogenase deficiency (G6PDD). METHODS Routine clinical and physical examinations were performed, and patient data was collected and analyzed. Protein expression levels of Itgb2 and glucose-6-phosphate dehydrogenase (G6pd) proteins were assessed by flow cytometry and the glucose-6-phosphate (G6P) substrate method, respectively. Whole exome sequencing was performed to investigate genetic variations of the patient and his parents. RESULTS The patient had fester disease and delayed separation of the umbilical cord at birth. Staphylococcus was detected in the fluid secretion of the auditory meatus of the patient. He exhibited a recurrent cheek scab, swollen hand, and swollen gum. Hematological examination indicated dramatic elevation of leukocytes including lymphocytes, monocytes, neutrophils and eosinophils. A novel homozygous mutation was detected in the ITGB2 gene of the patient, which was determined to be a two nucleotide deletion at the site of c.1537-1538 (c.1537-1538delGT), causing a frameshift of 24 amino acids from p.513 and inducing a stop codon (p.V513Lfs*24). A base substitution mutation was identified at c.1466 (c.1466G>T) of G6PD on chromosome X of the patient, which resulted in an amino acid change from arginine to leucine at p.489 (p.R489L). The patient also showed deficient lymphocyte expression of CD18 (2.99%) and significant downregulation of the G6pd protein. CONCLUSIONS The patient was diagnosed with G6PDD and moderate LAD-1. The combination of LAD-1 and G6PDD in this case may have been due to the high incidence of genetic disease in this minority ethnic population. Analyzing existing LAD-1 and G6PDD cases from different populations can facilitate disease diagnosis and treatment. Particularly, reporting pathogenic mutations of LAD-1 and G6PDD will be crucial for genetic testing and prenatal diagnosis in an effort to decrease the incidence of these diseases.
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Affiliation(s)
- Yu Zhang
- Kunming Key Laboratory of Children Infection and Immunity, Yunnan Key Laboratory of Children's Major Disease Research, Yunnan Medical Center for Pediatric Diseases, Yunnan Institute of Pediatrics, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Xiaotao Yang
- Department of 2nd Infections, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Xiaoli He
- Kunming Key Laboratory of Children Infection and Immunity, Yunnan Key Laboratory of Children's Major Disease Research, Yunnan Medical Center for Pediatric Diseases, Yunnan Institute of Pediatrics, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Haifeng Liu
- Kunming Key Laboratory of Children Infection and Immunity, Yunnan Key Laboratory of Children's Major Disease Research, Yunnan Medical Center for Pediatric Diseases, Yunnan Institute of Pediatrics, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Pin Guo
- Department of Pharmacy, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Xiaoning Liu
- Department of Pharmacy, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Yang Xiao
- Department of Otolaryngology, Head & Neck Surgery, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Xingxing Feng
- Department of Clinical Laboratory, Kunming Children's Hospital, Kunming 650228, Yunnan, China
| | - Yanchun Wang
- Department of 2nd Infections, Kunming Children's Hospital, Kunming 650228, Yunnan, China.
| | - Li Li
- Kunming Key Laboratory of Children Infection and Immunity, Yunnan Key Laboratory of Children's Major Disease Research, Yunnan Medical Center for Pediatric Diseases, Yunnan Institute of Pediatrics, Kunming Children's Hospital, Kunming 650228, Yunnan, China.
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TCIRG1 and SNX10 gene mutations in the patients with autosomal recessive osteopetrosis. Gene 2019; 702:83-88. [PMID: 30898715 DOI: 10.1016/j.gene.2019.02.088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 02/08/2019] [Accepted: 02/25/2019] [Indexed: 11/21/2022]
Abstract
Autosomal recessive osteopetrosis (ARO) is a rare genetic bone disease characterized by dense and fragile bone, caused by a defect in osteoclasts responsible for the bone destruction. In this study, we aimed to investigate the mutations in TCIRG1 and SNX10 that are responsible for 50% and 4% of the cases, respectively. All amplicons were sequenced by Sanger sequencing following PCR amplification. As a result, six different mutations of the TCIRG1 gene were found in five of the twelve unrelated cases. These include two novel mutations, namely c.630 + 1G > T mutation and c.1778_1779delTG mutation of the gene which are identified as homozygous. A compound heterozygosity of known mutations c.649_674del26 and c.1372G > A and homozygous presence of the known c.2235 + 1G > A mutation were also observed in different patients. In addition, as a result of the prenatal testing in a family with osteopetrosis infant, the c.1674-1G > A mutation was detected as homozygous for the fetus. In TCIRG1, c.166C > T change, which is indicated as likely benign according to ClinVar database, was heterozygous. Several known polymorphisms; c.117 + 83 T > C, c.417 + 11A > G and c.714-19C > A in TCIRG1 gene; c.24 + 36 T > A and c.112-84G > A in SNX10 gene were also detected. In conclusion, our study revealed that five of the twelve cases carry at least one mutation of TCIRG1 gene. Further studies with more patients and other genes would help better understanding of genetic etiology of the disease.
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Han G, Zuo J, Holliday LS. Specialized Roles for Actin in Osteoclasts: Unanswered Questions and Therapeutic Opportunities. Biomolecules 2019; 9:biom9010017. [PMID: 30634501 PMCID: PMC6359508 DOI: 10.3390/biom9010017] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 01/03/2019] [Accepted: 01/04/2019] [Indexed: 12/11/2022] Open
Abstract
Osteoclasts are cells of the hematopoietic lineage that are specialized to resorb bone. In osteoclasts, the actin cytoskeleton engages in at least two unusual activities that are required for resorption. First, microfilaments form a dynamic and structurally elaborate actin ring. Second, microfilaments bind vacuolar H⁺-ATPase (V-ATPase) and are involved in forming the V-ATPase-rich ruffled plasma membrane. The current review examines these two specialized functions with emphasis on the identification of new therapeutic opportunities. The actin ring is composed of substructures called podosomes that are interwoven to form a cohesive superstructure. Studies examining the regulation of the formation of actin rings and its constituent proteins are reviewed. Areas where there are gaps in the knowledge are highlighted. Microfilaments directly interact with the V-ATPase through an actin binding site in the B2-subunit of V-ATPase. This binding interaction is required for ruffled membrane formation. Recent studies show that an inhibitor of the interaction blocks bone resorption in pre-clinical animal models, including a model of post-menopausal osteoporosis. Because the unusual actin-based resorption complex is unique to osteoclasts and essential for bone resorption, it is likely that deeper understanding of its underlying mechanisms will lead to new approaches to treat bone disease.
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Affiliation(s)
- Guanghong Han
- Department of Stomatology, College and Hospital of Stomatology, Jilin University, Changchun 130021, China.
| | - Jian Zuo
- Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, FL 32610, USA.
| | - Lexie Shannon Holliday
- Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, FL 32610, USA.
- Department of Anatomy & Cell Biology, College of Dentistry, University of Florida, Gainesville, FL 32610, USA.
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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: 41] [Impact Index Per Article: 6.8] [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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Holliday LS. Vacuolar H +-ATPases (V-ATPases) as therapeutic targets: a brief review and recent developments. ACTA ACUST UNITED AC 2017; 1. [PMID: 30957075 DOI: 10.21037/biotarget.2017.12.01] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Vacuolar H+-ATPases (V-ATPases) are multi-subunit enzymes that play housekeeping roles in eukaryotic cells by acidifying lysosomes, late endosomes, Golgi, and other membrane-bounded compartments. Beyond that, V-ATPases have specialized functions in certain cell types linked to diseases including osteoporosis and cancer. Efforts to identify strategies to develop inhibitors selective for V-ATPases that are involved in disease progression have been ongoing for more than two decades, but so far have not yielded a therapeutic agent that has been translated to the clinic. Recent basic science studies have identified unexpected roles for V-ATPases in nutrient and energy sensing, and renin/angiotensin signaling, which offer additional incentives for considering V-ATPases as therapeutic targets. This article briefly reviews efforts to utilize inhibitors of V-ATPases as drugs. Primary focus is on recent "rational" efforts to identify small molecule inhibitors of the V-ATPases that are selectively expressed in osteoclasts and cancer cells. Enoxacin and bis-enoxacin are two molecules that emerged from these efforts. These molecules block a binding interaction between V-ATPases and microfilaments that occurs in osteoclasts, but not most other cell types, which relates to the specialized function of V-ATPases in bone resorption. Enoxacin and bis-enoxacin have proven useful in the treatment of bone diseases and cancer in animal models and display therapeutic effects that are different, and perhaps better, than current drugs. These results provide evidence that agents targeting subsets of V-ATPases may prove useful in the clinic.
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Affiliation(s)
- L Shannon Holliday
- Departments of Orthodontics and Anatomy & Cell Biology, University of Florida College of Dentistry, Gainesville, Florida, USA
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Duan X, Liu J, Zheng X, Wang Z, Zhang Y, Hao Y, Yang T, Deng H. Deficiency of ATP6V1H Causes Bone Loss by Inhibiting Bone Resorption and Bone Formation through the TGF-β1 Pathway. Am J Cancer Res 2016; 6:2183-2195. [PMID: 27924156 PMCID: PMC5135442 DOI: 10.7150/thno.17140] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 08/15/2016] [Indexed: 12/02/2022] Open
Abstract
Vacuolar-type H +-ATPase (V-ATPase) is a highly conserved, ancient enzyme that couples the energy of ATP hydrolysis to proton transport across vesicular and plasma membranes of eukaryotic cells. Previously reported mutations of various V-ATPase subunits are associated with increased bone density. We now show that haploinsufficiency for the H subunit of the V1 domain (ATP6V1H) is associated with osteoporosis in humans and mice. A genome-wide SNP array analysis of 1625 Han Chinese found that 4 of 15 tag SNPs (26.7%) within ATP6V1H were significantly associated with low spine bone mineral density. Atp6v1h+/- knockout mice generated by the CRISPR/Cas9 technique had decreased bone remodeling and a net bone matrix loss. Atp6v1h+/- osteoclasts showed impaired bone formation and increased bone resorption. The increased intracellular pH of Atp6v1h+/- osteoclasts downregulated TGF-β1 activation, thereby reducing induction of osteoblast formation but the bone mineralization was not altered. However, bone formation was reduced more than bone resorption. Our data provide evidence that partial loss of ATP6V1H function results in osteoporosis/osteopenia. We propose that defective osteoclast formation triggers impaired bone formation by altering bone remodeling. In the future, ATP6V1H might, therefore, serve as a target for the therapy of osteoporosis.
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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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Vacuolar H+-ATPase: An Essential Multitasking Enzyme in Physiology and Pathophysiology. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/675430] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Vacuolar H+-ATPases (V-ATPases) are large multisubunit proton pumps that are required for housekeeping acidification of membrane-bound compartments in eukaryotic cells. Mammalian V-ATPases are composed of 13 different subunits. Their housekeeping functions include acidifying endosomes, lysosomes, phagosomes, compartments for uncoupling receptors and ligands, autophagosomes, and elements of the Golgi apparatus. Specialized cells, including osteoclasts, intercalated cells in the kidney and pancreatic beta cells, contain both the housekeeping V-ATPases and an additional subset of V-ATPases, which plays a cell type specific role. The specialized V-ATPases are typically marked by the inclusion of cell type specific isoforms of one or more of the subunits. Three human diseases caused by mutations of isoforms of subunits have been identified. Cancer cells utilize V-ATPases in unusual ways; characterization of V-ATPases may lead to new therapeutic modalities for the treatment of cancer. Two accessory proteins to the V-ATPase have been identified that regulate the proton pump. One is the (pro)renin receptor and data is emerging that indicates that V-ATPase may be intimately linked to renin/angiotensin signaling both systemically and locally. In summary, V-ATPases play vital housekeeping roles in eukaryotic cells. Specialized versions of the pump are required by specific organ systems and are involved in diseases.
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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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Pangrazio A, Caldana ME, Lo Iacono N, Mantero S, Vezzoni P, Villa A, Sobacchi C. Autosomal recessive osteopetrosis: report of 41 novel mutations in the TCIRG1 gene and diagnostic implications. Osteoporos Int 2012; 23:2713-8. [PMID: 22231430 DOI: 10.1007/s00198-011-1878-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 11/09/2011] [Indexed: 12/24/2022]
Abstract
UNLABELLED Here we report 41 novel mutations in the TCIRG1 gene that is responsible for the disease in more than 50% of ARO patients. The characterisation of mutations in this gene might be useful in the process of drug design for osteoporosis treatment. INTRODUCTION Autosomal recessive osteopetrosis (ARO) is a genetically heterogeneous disorder due to reduced bone resorption by osteoclasts. In this process, a crucial role is played by the proton pump V-ATPase. Biallelic mutations in the TCIRG1 gene, encoding for the a3 subunit of this pump, are responsible for more than one half of ARO patients. METHODS Patients with a clinical diagnosis of ARO have been collected for 7 years and mutation analysis of the TCIRG1 gene was performed using direct DNA sequencing of PCR-amplified exons according to both a standard protocol and a modified one. RESULTS We report here 41 novel mutations identified in 67 unpublished patients, all with biallelic mutations. In particular, we describe two novel large genomic deletions and two splice site mutations in the 5' UTR of the TCIRG1 gene, in patients previously classified as mono-allelic. CONCLUSIONS Our data highlights the importance of two large genomic deletions and mutations in the 5' UTR with respect to patient management and, more critically, to prenatal diagnosis. With the present work, we strongly contribute to the molecular dissection of TCIRG1-deficient ARO and identify several protein residues which are fundamental for proton pump function and could thus be the target of future drugs designed to inhibit osteoclast resorptive activity.
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Affiliation(s)
- A Pangrazio
- Milan Unit, Institute of Genetic and Biomedical Research (IRGB), National Research Council, 20138, Milan, Italy
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15
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Toro EJ, Ostrov DA, Wronski TJ, Holliday LS. Rational identification of enoxacin as a novel V-ATPase-directed osteoclast inhibitor. Curr Protein Pept Sci 2012; 13:180-91. [PMID: 22044158 PMCID: PMC3409362 DOI: 10.2174/138920312800493151] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/15/2011] [Accepted: 06/16/2011] [Indexed: 11/22/2022]
Abstract
Binding between vacuolar H+-ATPases (V-ATPases) and microfilaments is mediated by an actin binding domain in the B-subunit. Both isoforms of mammalian B-subunit bind microfilaments with high affinity. A similar actin-binding activity has been demonstrated in the B-subunit of yeast. A conserved “profilin-like” domain in the B-subunit mediates this actin-binding activity, named due to its sequence and structural similarity to an actin-binding surface of the canonical actin binding protein profilin. Subtle mutations in the “profilin-like” domain eliminate actin binding activity without disrupting the ability of the altered protein to associate with the other subunits of V-ATPase to form a functional proton pump. Analysis of these mutated B-subunits suggests that the actin-binding activity is not required for the “housekeeping” functions of V-ATPases, but is important for certain specialized roles. In osteoclasts, the actin-binding activity is required for transport of V-ATPases to the plasma membrane, a prerequisite for bone resorption. A virtual screen led to the identification of enoxacin as a small molecule that bound to the actin-binding surface of the B2-subunit and competitively inhibited B2-subunit and actin interaction. Enoxacin disrupted osteoclastic bone resorption in vitro, but did not affect osteoblast formation or mineralization. Recently, enoxacin was identified as an inhibitor of the virulence of Candidaalbicans and more importantly of cancer growth and metastasis. Efforts are underway to determine the mechanisms by which enoxacin and other small molecule inhibitors of B2 and microfilament binding interaction selectively block bone resorption, the virulence of Candida, cancer growth, and metastasis.
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Affiliation(s)
- Edgardo J Toro
- Department of Orthodontics, University of Florida College of Dentistry, Gainesville, FL 32610, USA
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16
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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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17
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Yuan P, Yue Z, Sun L, Huang W, Hu B, Yang Z, Hu Y, Xiao H, Shi H, Zhou Q, Wang Y. Novel mutation of TCIRG1 and clinical pictures of two infantile malignant osteopetrosis patients. J Bone Miner Metab 2011; 29:251-6. [PMID: 21042819 DOI: 10.1007/s00774-010-0228-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 09/08/2010] [Indexed: 09/29/2022]
Abstract
Infantile malignant osteopetrosis (IMO) (OMIM 259700) is a lethal autosomal recessive disease. The underlying gene in most IMO patients is TCIRG1. This codes for the TCIRG1 protein involved in the cellular proton pump, which is highly expressed on surfaces of osteoclasts. We have characterized a family comprising two affected siblings born to healthy parents. The sister and her younger brother both presented classical X-ray images of IMO at 17 h and 16 weeks, respectively, after birth, and both died after the appearance of fever and flu-like symptoms months later. Radiographs revealed normal bone density in both parents. Mutation detection of the TCIRG1 gene was performed in the boy and the parents. The novel mutation c.242delC (p.Pro81ArgfsX85) and the known mutation c.1114C>T (p.Gln372X) were both identified in the boy. Both mutations are predicted to introduce premature stop codons, with deletion of 666 amino acids from the C terminus of the TCIRG1 protein of one allele and 459 from the other. Both mutations involve loss of part or the whole of the ATPase V0-complex domain of the protein. The father carries the c.242delC (p.Pro81ArgfsX85) mutation and the mother the c.1114C>T (p.Gln372X). Our findings provide new data for pre- and post-natal genetic diagnosis and identification of heterozygous carriers of the disease.
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Affiliation(s)
- Ping Yuan
- Department of Medical Genetics, Center for Genome Research, Zhongshan School of Medicine, Sun Yat-Sen University, 74 Zhongshan Road II, Guangzhou, 510080, People's Republic of China
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18
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Sihn G, Rousselle A, Vilianovitch L, Burckle C, Bader M. Physiology of the (pro)renin receptor: Wnt of change? Kidney Int 2010; 78:246-56. [DOI: 10.1038/ki.2010.151] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Abstract
Osteopetrorickets is a rare autosomal recessive disorder of osteoclast function characterized by abnormally dense bone and failure of resorption of calcified cartilage. Rickets is a paradoxical complication of osteopetrosis, resulting from the inability of the osteoclasts to maintain a normal calcium-phosphorus balance in the extracellular fluid. We report a patient with an unusual case of infantile osteopetro-rickets who was admitted with anterior fontanel bulging and was treated with haploidentical bone marrow transplantation.
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Affiliation(s)
- A Avni Atay
- Department ofPediatric Hematology, Gulhane Military Medical Academy, Ankara, Turkey
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20
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Villa A, Guerrini MM, Cassani B, Pangrazio A, Sobacchi C. Infantile malignant, autosomal recessive osteopetrosis: the rich and the poor. Calcif Tissue Int 2009; 84:1-12. [PMID: 19082854 DOI: 10.1007/s00223-008-9196-4] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 11/07/2008] [Indexed: 02/06/2023]
Abstract
Human recessive osteopetrosis (ARO) represents a group of diseases in which, due to a defect in osteoclasts, bone resorption is prevented. The deficit could arise either from failure in osteoclast differentiation or from inability to perform resorption by mature, multinucleated, but nonfunctional cells. Historically, osteopetrosis due to both these mechanisms was found in spontaneous and artificially created mouse mutants, but the first five genes identified in human ARO (CA-II, TCIRG1, ClCN7, OSTM1, and PLEKHM1) were all involved in the effector function of mature osteoclasts, being linked to acidification of the cell/bone interface or to intracellular processing of the resorbed material. Differentiation defects in human ARO have only recently been described, following the identification of mutations in both RANKL and RANK, which define a new form of osteoclast-poor ARO, as expected from biochemical, cellular, and animal studies. The molecular dissection of ARO has prognostic and therapeutic implications. RANKL-dependent patients, in particular, represent an interesting subset which could benefit from mesenchymal cell transplant and/or administration of soluble RANKL cytokine.
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Affiliation(s)
- Anna Villa
- Istituto di Tecnologie Biomediche, CNR, via Cervi 93, Segrate, Italy.
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21
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Characterization of a novel Alu-Alu recombination-mediated genomic deletion in the TCIRG1 gene in five osteopetrotic patients. J Bone Miner Res 2009; 24:162-7. [PMID: 18715141 DOI: 10.1359/jbmr.080818] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Human malignant autosomal recessive osteopetrosis (ARO) is a genetically heterogeneous disorder caused by reduced bone resorption by osteoclasts. Biallelic mutations in the TCIRG1 gene, encoding the a3 subunit of the vacuolar proton pump, are responsible for more than one half of ARO patients. However, a few patients with monoallelic mutations have been described, raising the possibility of a dominant-like TCIRG1-dependent osteopetrosis, of a digenic disease, or of peculiar mutations difficult to detect with standard methods. We describe here a novel genomic deletion in the TCIRG1 gene explaining why, in some patients, mutations in only one allele have previously been found. The analysis of a proband from a consanguineous Turkish family allowed us to define the deletion boundaries encompassing introns 10 and 13 and occurring within AluSx repeat sequences, suggesting Alu-mediated homologous recombination as a mechanism. An identical genomic deletion at the heterozygous level was found in four unrelated Italian families in whom only a single mutated allele has previously been found. TCIRG1 haplotype analysis in these five families suggests a possible common ancestral origin for this large deletion. In summary, we describe the identification of a novel genomic deletion in the TCIRG1 gene that is of clinical relevance, especially in prenatal diagnosis.
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22
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Callahan JW, Bagshaw RD, Mahuran DJ. The integral membrane of lysosomes: its proteins and their roles in disease. J Proteomics 2008; 72:23-33. [PMID: 19068244 DOI: 10.1016/j.jprot.2008.11.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 10/30/2008] [Accepted: 11/11/2008] [Indexed: 12/18/2022]
Abstract
The protein composition of the integral lysosomal membrane and the membrane-associated compartment have been defined in part by proteomics approaches. While the role of its constituent hydrolases in a large array of human disorders has been well-documented, the manner in which membrane proteins are integrated into the organelle, the multiprotein complexes that form at the organelle's cytosolic surface and their roles in the biogenesis and functional control of the organelle are now emerging. Defining cytosolic targeting complexes that affect the function of the lysosomal/endosomal compartment may help to identify the lysosome's role in a variety of human pathologies.
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Affiliation(s)
- John W Callahan
- Research Institute, The Hospital for Sick Children, Toronto, Canada.
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23
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Pata M, Héraud C, Vacher J. OSTM1 bone defect reveals an intercellular hematopoietic crosstalk. J Biol Chem 2008; 283:30522-30. [PMID: 18790735 PMCID: PMC2662145 DOI: 10.1074/jbc.m805242200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Revised: 09/08/2008] [Indexed: 12/31/2022] Open
Abstract
The most severe form of bone autosomal recessive osteopetrosis both in humans and in the gray-lethal (gl/gl) mouse is caused by mutations in the Ostm1 gene. Although osteopetrosis is usually associated with a defect in the hematopoietic-derived osteoclast cells, this study determined that Ostm1 is expressed in many hematopoietic cells of the myeloid and lymphoid B- and T-lineages. Hematopoiesis in gl/gl mice is characterized by a marked expansion of the osteoclast lineage but also by deregulation of the lymphoid lineages with a decrease in B-lymphoid cell populations and altered distribution in T-lymphoid double and single CD4 CD8-positive cells. In committed gl/gl osteoclasts, specific Ostm1 transgene targeting showed a requirement of additional factors and/or cells for normal osteoclast function, and importantly, defined the gl osteopetrotic defect as non-cell autonomous. By contrast, gl/gl osteoclast, B- and T-lymphoid lineage phenotypes were rescued when Ostm1 is expressed under PU.1 regulation from a bacterial artificial chromosome transgene, which established an essential role for Ostm1 in hematopoietic cells in addition to osteoclasts. Together these experiments are the first to demonstrate the existence of hematopoietic crosstalk for the production of functional and active osteoclasts.
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Affiliation(s)
- Monica Pata
- Department of Cellular Interactions and Development, Faculté de Médecine de l'Université de Montréal, Québec H2W 1R7, Canada
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24
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Villa A, Pangrazio A, Caldana E, Guerrini M, Vezzoni P, Frattini A, Sobacchi C. Prognostic potential of precise molecular diagnosis of Autosomal Recessive Osteopetrosis with respect to the outcome of bone marrow transplantation. Cytotechnology 2008; 58:57-62. [PMID: 19002772 DOI: 10.1007/s10616-008-9165-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 09/15/2008] [Indexed: 10/21/2022] Open
Abstract
Hematopoietic stem cell transplantation (HSCT) is often the only practical approach to fatal genetic defects. One of the first pathologies which HSCT was applied to was Autosomal Recessive Osteopetrosis (ARO), a rare genetic bone disease in which a deficit in bone resorption by osteoclasts leads to increased bone density and secondary defects. The disease is often lethal early in life unless treated with HSCT. In utero transplantation (IUT) of the oc/oc mouse, reproducing the clinical features of a subset of ARO, has demonstrated that the quality of life and the survival of transplanted animals are greatly improved, suggesting that a similar protocol could be applied to humans. However, recently the dissection of the molecular bases of the disease has shown that ARO is genetically heterogeneous and has revealed the presence of subsets of patients which do not benefit from HSCT. This observation highlights the importance of molecular diagnosing ARO to identify and establish the proper therapies for a better prognosis. In particular, on the basis of experimental results in murine models, efforts should be undertaken to develop approaches such as IUT and new pharmacological strategies.
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Affiliation(s)
- Anna Villa
- Istituto di Tecnologie Biomediche, CNR, via F.lli Cervi 93, 20090, Segrate, Italy,
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25
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Brain lipid composition in grey-lethal mutant mouse characterized by severe malignant osteopetrosis. Glycoconj J 2008; 26:623-33. [DOI: 10.1007/s10719-008-9179-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 08/06/2008] [Accepted: 08/08/2008] [Indexed: 12/11/2022]
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26
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Feng H, Cheng T, Pavlos NJ, Yip KHM, Carrello A, Seeber R, Eidne K, Zheng MH, Xu J. Cytoplasmic terminus of vacuolar type proton pump accessory subunit Ac45 is required for proper interaction with V(0) domain subunits and efficient osteoclastic bone resorption. J Biol Chem 2008; 283:13194-204. [PMID: 18227071 DOI: 10.1074/jbc.m709712200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Solubilization of mineralized bone by osteoclasts is largely dependent on the acidification of the extracellular resorption lacuna driven by the vacuolar (H+)-ATPases (V-ATPases) polarized within the ruffled border membranes. V-ATPases consist of two functionally and structurally distinct domains, V(1) and V(0). The peripheral cytoplasmically oriented V(1) domain drives ATP hydrolysis, which necessitates the translocation of protons across the integral membrane bound V(0) domain. Here, we demonstrate that an accessory subunit, Ac45, interacts with the V(0) domain and contributes to the vacuolar type proton pump-mediated function in osteoclasts. Consistent with its role in intracellular acidification, Ac45 was found to be localized to the ruffled border region of polarized resorbing osteoclasts and enriched in pH-dependent endosomal compartments that polarized to the ruffled border region of actively resorbing osteoclasts. Interestingly, truncation of the 26-amino acid residue cytoplasmic tail of Ac45, which encodes an autonomous internalization signal, was found to impair bone resorption in vitro. Furthermore, biochemical analysis revealed that although both wild type Ac45 and mutant were capable of associating with subunits a3, c, c'', and d, deletion of the cytoplasmic tail altered its binding proximity with a3, c'', and d. In all, our data suggest that the cytoplasmic terminus of Ac45 contains elements necessary for its proper interaction with V(0) domain and efficient osteoclastic bone resorption.
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Affiliation(s)
- Haotian Feng
- Molecular Orthopaedic Laboratory, Centre for Orthopaedic Research, School of Surgery and Pathology, University of Western Australia, Nedlands, Western Australia 6009, Australia
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27
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Conway RL, Falk RE. A patient with TCIRG1-related infantile osteopetrosis presenting with congenital anomalies: chance association or a case for pleiotropy? Am J Med Genet A 2007; 143A:3140-3. [PMID: 18000986 DOI: 10.1002/ajmg.a.32102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Robert L Conway
- Pediatrics and Human Development, Michigan State University, East Lansing, Michigan, USA.
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28
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Beranger GE, Momier D, Guigonis JM, Samson M, Carle GF, Scimeca JC. Differential binding of poly(ADP-Ribose) polymerase-1 and JunD/Fra2 accounts for RANKL-induced Tcirg1 gene expression during osteoclastogenesis. J Bone Miner Res 2007; 22:975-83. [PMID: 17419679 DOI: 10.1359/jbmr.070406] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED We studied Tcirg1 gene expression on RANKL-induced osteoclastic differentiation of the mouse model RAW264.7 cells. We identified a mechanism involving PARP-1 inhibition release and JunD/Fra-2 binding, which is responsible for Tcirg1 gene upregulation. INTRODUCTION The Tcirg1 gene encodes the a3 isoform of the V-ATPase a subunit, which plays a critical role in the resorption activity of the osteoclast. Using serial deletion constructs of the Tcirg1 gene promoter, we performed a transcriptional study to identify factor(s) involved in the regulation of the RANKL-induced gene expression. MATERIALS AND METHODS The promoter activity of serial-deletion fragments of the Tcirg1 gene promoter was monitored throughout the RAW264.7 cells differentiation process. We next performed sequence analysis, EMSA, UV cross-linking, qPCR, and gel supershift experiments to identify the factor(s) interacting with the promoter. RESULTS A deletion of the -1297-1244 region led to the disappearance of the RANKL-induced promoter activity. EMSA experiments showed the binding of two factors that undergo differential binding on RANKL treatment. Supershift experiments led us to identify the dimer JunD/Fra-2 as the binding activity associated with the -1297/-1268 Tcirg1 gene promoter sequence in response to RANKL. Moreover, we observed poly(ADP-ribose) polymerase-1 (PARP-1) binding to an adjacent site (-1270/-1256), and this interaction was disrupted after RANKL treatment. CONCLUSIONS We provide data that identify junD proto-oncogene (JunD) and Fos-related antigen 2 (Fra-2) as the activator protein-1 (AP-1) factors responsible for the RANKL-induced upregulation of the mouse Tcirg1 gene expression. Moreover, we identified another binding site for PARP-1 that might account for the repression of Tcirg1 gene expression in pre-osteoclastic cells.
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29
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Souraty N, Noun P, Djambas-Khayat C, Chouery E, Pangrazio A, Villa A, Lefranc G, Frattini A, Mégarbané A. Molecular study of six families originating from the Middle-East and presenting with autosomal recessive osteopetrosis. Eur J Med Genet 2007; 50:188-99. [PMID: 17400532 DOI: 10.1016/j.ejmg.2007.01.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Accepted: 01/30/2007] [Indexed: 11/18/2022]
Abstract
Autosomal recessive osteopetrosis is a severe hereditary bone disease whose cellular basis is in the osteoclast, but with heterogeneous molecular defects. We hereby report the clinical and the molecular study of seven patients affected by the recessive form of osteopetrosis (ARO) from six families originating from the Middle-East: four from Lebanon and two from Syria. Parental consanguinity was found in five families. The mean age of diagnosis was 3 months. Failure to thrive, prominent forehead, exophthalmia, optic atrophy, hepatosplenomegaly, neurological manifestations, anaemia, thrombocytopenia, hypocalcaemia, elevated hepatic enzymes and acid phosphatase, and an early fatal outcome were common. Macrocephaly, strabismus, and brain malformations were relatively less common. Mutations were identified in two genes: TCIRG1 and OSTM1. Phenotype-genotype correlation is discussed.
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Affiliation(s)
- Noëlle Souraty
- Unité de Génétique Médicale, Laboratoire de Biologie Moléculaire et Cytogénétique, Faculté de Médecine, Université Saint-Joseph, Beirut, Lebanon
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30
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Beranger GE, Momier D, Rochet N, Quincey D, Guigonis JM, Samson M, Carle GF, Scimeca JC. RANKL treatment releases the negative regulation of the poly(ADP-ribose) polymerase-1 on Tcirg1 gene expression during osteoclastogenesis. J Bone Miner Res 2006; 21:1757-69. [PMID: 17002555 DOI: 10.1359/jbmr.060809] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED The Tcirg1 gene encodes the osteoclast-specific a3 isoform of the V-ATPase a subunit. Using the mouse osteoclastic model RAW264.7 cells, we studied Tcirg1 gene expression, and we identified PARP-1 as a transcriptional repressor negatively regulated by RANKL during osteoclastogenesis. INTRODUCTION The TCIRG1 gene encodes the a3 isoform of the V-ATPase a subunit, and mutations at this locus account for approximately 60% of infantile malignant osteopetrosis cases. Using RAW264.7 cells as an osteoclastic differentiation model, we undertook a transcriptional study of the mouse Tcirg1 gene focused on the 4-kb region upstream of the transcription starting point. MATERIALS AND METHODS The promoter activity of serial-deletion fragments of the Tcirg1 gene promoter was monitored throughout the RAW264.7 cell differentiation process. We next performed EMSA, UV cross-linking, affinity purification, mass spectrometry analysis, gel supershift, and siRNA transfection experiments to identify the factor(s) interacting with the promoter. RESULTS The -3946/+113 region of the mouse Tcirg1 gene displayed a high basal promoter activity, which was enhanced by RANKL treatment of RAW264.7 cells. Constructs deleted up to -1589 retained this response to RANKL. A deletion up to -1402 induced a 3-fold enhancement of the basal activity, whereas RANKL response was not affected. EMSA experiments led us to identify within the -1589/-1402 region, a 10-nucleotide sequence, which bound a nuclear protein present in nondifferentiated RAW264.7 cells. This interaction was lost using nuclear extracts derived from RANKL-treated cells. Affinity purification followed by mass spectrometry analysis and gel supershift assay allowed the identification of poly(ADP-ribose) polymerase-1 (PARP-1) as this transcriptional repressor, whereas Western blot experiments revealed the cleavage of the DNA-binding domain of PARP-1 on RANKL treatment. Finally, both PARP-1 depletion after siRNA transfection and RAW264.7 cell treatment by an inhibitor of PARP-1 activity induced an increase of a3 mRNA expression. CONCLUSIONS We provide evidence that the basal transcription activity of the Tcirg1 gene is negatively regulated by the binding of PARP-1 protein to its promoter region in mouse pre-osteoclast. On RANKL treatment, PARP-1 protein is cleaved and loses its repression effect, allowing an increase of Tcirg1 gene expression that is critical for osteoclast function.
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Affiliation(s)
- Guillaume E Beranger
- GéPITOS-K2943 CNRS/UNSA, Faculté de Médecine de l'Université de Nice-Sophia Antipolis, Nice, France
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Blin-Wakkach C, Breuil V, Quincey D, Bagnis C, Carle GF. Establishment and characterization of new osteoclast progenitor cell lines derived from osteopetrotic and wild type mice. Bone 2006; 39:53-60. [PMID: 16503212 DOI: 10.1016/j.bone.2005.12.078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Accepted: 12/16/2005] [Indexed: 11/30/2022]
Abstract
Malignant infantile osteopetrosis is a rare and lethal disease characterized by the absence of bone resorption due to inactive osteoclasts (OCLs). Among the murine models of osteopetrosis, the Tcirg1oc/oc mouse is the most resembling to the human pathology. In the majority of patients as in Tcirg1oc/oc mouse, the gene involved is the Tcirg1 gene, encoding the a3 subunit of the vacuolar proton pump. However, to date, no osteoclastic cell lines from osteopetrotic mice are available to facilitate the study of either OCL differentiation in osteopetrosis or the factors involved in the control of Tcirg1 gene expression. Heterozygotes Tcirg1+/oc mice were crossed with p53+/- mice to obtain homozygotes p53-/-Tcirg1oc/oc and p53-/-Tcirg1+/+ animals. The p53-/-Tcirg1oc/oc mice display the same bone and hematological phenotype as the original Tcirg1oc/oc mice. From the bone marrow of these mice, we have derived cell lines named POC-MGoc/oc and POC-MG+/+. These cell lines express standard osteoclastogenic markers and differentiate into OCLs in the presence of RANK-L and M-CSF. Furthermore, both cell lines can be transduced by a lentiviral vector with a high efficiency and without alteration of their OCL differentiation potential. Therefore, these cell lines provide valuable new tools to study the differentiation and function of osteoclasts in normal and resorption defective conditions.
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Affiliation(s)
- Claudine Blin-Wakkach
- CNRS/UNSA Unité K2943, IFR50, Faculté de Médecine, and Service de Rhumatologie, Hôpital L'Archet 1, Nice, France
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Pangrazio A, Poliani PL, Megarbane A, Lefranc G, Lanino E, Di Rocco M, Rucci F, Lucchini F, Ravanini M, Facchetti F, Abinun M, Vezzoni P, Villa A, Frattini A. Mutations in OSTM1 (grey lethal) define a particularly severe form of autosomal recessive osteopetrosis with neural involvement. J Bone Miner Res 2006; 21:1098-105. [PMID: 16813530 DOI: 10.1359/jbmr.060403] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
UNLABELLED We report three novel osteopetrosis patients with OSTM1 mutations and review two that have been previously described. Our analysis suggests that OSTM1 defines a new subset of patients with severe central nervous system involvement. This defect is also present in the gl mouse, which could represent a good model to study the role of the gene in the pathogenesis of this disease. INTRODUCTION Autosomal recessive osteopetrosis (ARO) is a severe hereditary bone disease whose cellular basis is in the osteoclast, but with heterogeneous molecular defects. In addition to the TCIRG1 and the ClCN7 genes, whose mutations account for approximately 55% and 10% of cases, respectively, the OSTM1 gene has been described thus far in only two ARO patients. materials and methods: We report here three novel ARO patients presenting with severe primary central nervous system involvement in addition to the classical stigmata of severe bone sclerosis, growth failure, anemia, thrombocytopenia, and visual impairment with optic atrophy. In addition we analyzed the brain morphology and histology of the grey lethal mutant mouse. RESULTS The analysis of the OSTM1 gene in two patients, both from Kuwait, showed homozygous two nucleotide deletion in exon 2, leading to a frameshift and premature termination. The third (Lebanese) patient showed a single point mutation in exon 1, leading to a nonsense mutation. The clinical neurological evaluation of the two Kuwaiti patients by CT and MRI scans showed a defect in the white matter, with a specific diagnosis of severe cerebral atrophy. The gl brain showed a diffuse translucent appearance with loss of the normal demarcation between the white and the grey matter, features consistent with myelin loss or hypomyelination. Histological and myelin staining analysis evidenced an atrophy of the corpus callosum with loss of myelin fibers, and in cortical areas, loss of the normal lamination consistent with multiple foci of cortical dysplasia. CONCLUSIONS These findings suggest that OSTM1-dependent ARO defines a new subset of patients with severe central nervous system involvement leading to a very poor prognosis. The fact that central nervous system involvement is also present in the gl mouse mutant suggests that this mouse is a good model to test possible therapies.
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Balemans W, Van Wesenbeeck L, Van Hul W. A clinical and molecular overview of the human osteopetroses. Calcif Tissue Int 2005; 77:263-74. [PMID: 16307387 DOI: 10.1007/s00223-005-0027-6] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Accepted: 04/08/2005] [Indexed: 12/15/2022]
Abstract
The osteopetroses are a heterogeneous group of bone remodeling disorders characterized by an increase in bone density due to a defect in osteoclastic bone resorption. In humans, several types can be distinguished and a classification has been made based on their mode of inheritance, age of onset, severity, and associated clinical symptoms. The best-known forms of osteopetrosis are the malignant and intermediate autosomal recessive forms and the milder autosomal dominant subtypes. In addition to these forms, a restricted number of cases have been reported in which additional clinical features unrelated to the increased bone mass occur. During the last years, molecular genetic studies have resulted in the identification of several disease-causing gene mutations. Thus far, all genes associated with a human osteopetrosis encode proteins that participate in the functioning of the differentiated osteoclast. This contributed substantially to the understanding of osteoclast functioning and the pathogenesis of the human osteopetroses and will provide deeper insights into the molecular pathways involved in other bone pathologies, including osteoporosis.
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Affiliation(s)
- W Balemans
- Department of Medical Genetics, University and University Hospital of Antwerp, Antwerp, Belgium
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Bagshaw RD, Mahuran DJ, Callahan JW. Lysosomal membrane proteomics and biogenesis of lysosomes. Mol Neurobiol 2005; 32:27-41. [PMID: 16077181 DOI: 10.1385/mn:32:1:027] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Accepted: 10/14/2004] [Indexed: 12/30/2022]
Abstract
This review focuses on events involved in the biogenesis of the lysosome. This organelle contains a diverse array of soluble, luminal proteins capable of digesting all the macromolecules in the cell. Altered function of lysosomes or its constituent enzymes has been implicated in a host of human pathologies, including storage diseases, cancer, and infectious and neurodegenerative diseases. Luminal enzymes are well-characterized, and aspects of how they are incorporated into lysosomes are known. However, little is known about the composition of the membrane surrounding the organelle or how the membrane is assembled. Our starting point to study lysosome biogenesis is to define the composition of the membrane by the use of proven methods for purification of lysosomes to near homogeneity and then to characterize membrane-associated and integral lysosomal membrane proteins. This has been achieved using advanced proteomics (electrophoretic or chromatographic separations of proteins followed by time-of-flight mass spectrometric identification of peptide sequences). To date, we have identified 55 proteins in the membrane-associated fraction and 215 proteins in the integral membrane. By applying these methods to mouse models of lysosome dysgenesis (such as BEIGE, Pale Ear, PEARL) that are related to human diseases such as Chediak-Higashi and Hermansky-Pudlak syndromes, it may be possible to define the membrane protein composition of lysosomes in each of these mutants and to determine how they differ from normal. Identifying proteins affected in the respective mutants may provide hints about how they are targeted to the lysosomal membrane and how failure to target them leads to disease; these features are pivotal to understanding lysosome biogenesis and have the potential to implicate lysosomes in a broad range of human pathologies.
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Affiliation(s)
- Richard D Bagshaw
- Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Canada
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35
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Hu Y, Nyman J, Muhonen P, Väänänen HK, Laitala-Leinonen T. Inhibition of the osteoclast V-ATPase by small interfering RNAs. FEBS Lett 2005; 579:4937-42. [PMID: 16115623 DOI: 10.1016/j.febslet.2005.07.078] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 07/19/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
The multisubunit enzyme V-ATPase harbours isoforms of individual subunits. a3 is one of four 116 kDa subunit a isoforms, and it is crucial for bone resorption. We used small interfering RNA (siRNA) molecules to knock down a3 in rat osteoclast cultures. Labeled siRNA-molecules entered osteoclasts via endocytosis and knocked down the a3 mRNA. Bone resorption was decreased in siRNA-treated samples due to decreased acidification and osteoclast inactivation. Expression of a1 did not respond to decreased a3 levels, suggesting that a1 does not compensate for a3 in osteoclast cultures. Subunit a3 is thus an interesting target for novel nucleic acid therapy.
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Affiliation(s)
- Yingwei Hu
- Bone Biology Research Consortium, Department of Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland
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36
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Smirnova AS, Morgun A, Shulzhenko N, Silva IDCG, Gerbase-DeLima M. Identification of new alternative splice events in the TCIRG1 gene in different human tissues. Biochem Biophys Res Commun 2005; 330:943-9. [PMID: 15809087 DOI: 10.1016/j.bbrc.2005.03.065] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Indexed: 11/19/2022]
Abstract
Two transcript variants (TV) of the T cell immune regulator gene 1 (TCIRG1) have already been characterized. TV1 encodes a subunit of the osteoclast vacuolar proton pump and TV2 encodes a T cell inhibitory receptor. Based on the search in dbEST, we validated by RT-PCR six new alternative splice events in TCIRG1 in most of the 28 human tissues studied. In addition, we observed that transcripts using the TV1 transcription start site and two splice forms previously described in a patient with infantile malignant osteopetrosis are also expressed in various tissues of healthy individuals. Studies of these nine splice forms in cytoplasmic RNA of peripheral blood mononuclear cells showed that at least six of them could be efficiently exported from the nucleus. Since various products with nearly ubiquitous tissue distribution are generated from TCIRG1, this gene may be involved in other processes besides immune response and bone resorption.
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Affiliation(s)
- Anna S Smirnova
- Immunogenetics Division, Pediatrics Department, Universidade Federal de São Paulo (UNIFESP-EPM), São Paulo, Brazil
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Susani L, Pangrazio A, Sobacchi C, Taranta A, Mortier G, Savarirayan R, Villa A, Orchard P, Vezzoni P, Albertini A, Frattini A, Pagani F. TCIRG1-dependent recessive osteopetrosis: mutation analysis, functional identification of the splicing defects, and in vitro rescue by U1 snRNA. Hum Mutat 2005; 24:225-35. [PMID: 15300850 DOI: 10.1002/humu.20076] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Human malignant infantile osteopetrosis (arOP) is a genetically heterogeneous autosomal recessive disorder of bone metabolism. The TCIRG1 gene, encoding the a3 subunit of the vacuolar proton pump, which mediates the acidification of the bone/osteoclast interface, is responsible for more than one-half of the arOP patients. We performed genetic analysis of TCIRG1 in 55 arOP patients including 25 new cases and identified nine novel mutations. The two most frequent mutations, c.1674-1G>A (aberrant splicing: r.1674_1884del) and c.2005C>T (protein variation: p.Arg669X), found in 17 and 16 alleles, respectively, constituted 30% of all TCIRG1 abnormalities. They both originated in Northern Europe, p.Arg669X quite recently from West Flanders, Belgium. As substitutions in splicing regulatory sequences represented a large portion (40%; 44 alleles) of the TCIRG1 variations, we developed a functional splicing assay to distinguish between polymorphic variants and disease-causing mutations. Three intronic nucleotide substitutions flanking the splice sites (c.117+4A>T; c.1673+5G>A; and c.504-8G>A) were studied using hybrid minigenes and an abnormal processing of the transcripts was demonstrated in all cases. Cotransfection experiments with complementary U1 snRNAs performed in c.117+4A>T and c.1673+5G>A mutations showed that only in the first case was the defect at the 5' splice site corrected, indicating that mutations near the invariant GT donor sites are mechanistically different. These findings indicate the feasibility of the hybrid minigene approach to detect splicing defects, particularly in patients in whom the RNA is not available. In addition, the present results suggest that modified U1 snRNAs may represent a new therapeutic strategy for arOP patients with a U1 snRNP-dependent splicing defect.
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Affiliation(s)
- Lucia Susani
- Istituto di Tecnologie Biomediche, CNR, Milan, Italy
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Utku N, Boerner A, Tomschegg A, Bennai-Sanfourche F, Bulwin GC, Heinemann T, Loehler J, Blumberg RS, Volk HD. TIRC7 deficiency causes in vitro and in vivo augmentation of T and B cell activation and cytokine response. THE JOURNAL OF IMMUNOLOGY 2004; 173:2342-52. [PMID: 15294947 DOI: 10.4049/jimmunol.173.4.2342] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The membrane protein T cell immune response cDNA 7 (TIRC7) was recently identified and was shown to play an important role in T cell activation. To characterize the function of TIRC7 in more detail, we generated TIRC7-deficient mice by gene targeting. We observed disturbed T and B cell function both in vitro and in vivo in TIRC7(-/-) mice. Histologically, primary and secondary lymphoid organs showed a mixture of hypo-, hyper-, and dysplastic changes of multiple lymphohemopoietic compartments. T cells from TIRC7(-/-) mice exhibited significantly increased proliferation and expression of IL-2, IFN-gamma, and IL-4 in response to different stimuli. Resting T cells from TIRC7(-/-) mice exhibited decreased CD62L, but increased CD11a and CD44 expression, suggesting an in vivo expansion of memory/effector T cells. Remarkably, activated T cells from TIRC7(-/-) mice expressed lower levels of CTLA-4 in comparison with wild-type cells. B cells from TIRC7-deficient mice exhibited significantly higher in vitro proliferation following stimulation with anti-CD40 Ab or LPS plus IL-4. B cell hyperreactivity was reflected in vivo by elevated serum levels of various Ig classes and higher CD86 expression on B cells. Furthermore, TIRC7 deficiency resulted in an augmented delayed-type hypersensitivity response that was also reflected in increased mononuclear infiltration in the skin obtained from TIRC7-deficient mice food pads. In summary, the data strongly support an important role for TIRC7 in regulating both T and B cell responses.
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Affiliation(s)
- Nalân Utku
- Institut für Medizinische Immunologie, Charité-Campus Mitte, Universitätsmedizin Berlin, Berlin, Germany.
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Blin-Wakkach C, Wakkach A, Sexton PM, Rochet N, Carle GF. Hematological defects in the oc/oc mouse, a model of infantile malignant osteopetrosis. Leukemia 2004; 18:1505-11. [PMID: 15284856 DOI: 10.1038/sj.leu.2403449] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Infantile malignant osteopetrosis (IMO) is a rare and lethal disease characterized by an absence of bone resorption due to inactive OCLs. Affected patients display an increased bone mass and hematological defects. The osteopetrotic oc/oc mouse displays a bone phenotype similar to the one observed in IMO patients, and the same gene, Tcirg1, is mutated in this model and in the majority of these patients. Therefore, we explored in oc/oc mice the consequences of the perturbed bone microenvironment on hematopoiesis. We show that the myelomonocytic differentiation is increased, leading to an elevated number of OCLs and dendritic cells. B lymphopoiesis is blocked at the pro-B stage in the bone marrow of oc/oc mouse, leading to a low mature B-cell number. T-cell activation is also affected, with a reduction of IFNgamma secretion by splenic CD4(+) T cells. These alterations are associated with a low IL-7 expression in bone marrow. All these data indicate that the lack of bone resorption in oc/oc mice has important consequences in both myelopoiesis and lymphopoiesis, leading to a form of immunodeficiency. The oc/oc mouse is therefore an appropriate model to understand the hematological defects described in IMO patients, and to derive new therapeutic strategies.
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Affiliation(s)
- C Blin-Wakkach
- GPM FRE2720, CNRS/UNSA, Faculté de Médecine, av de Valombrose, Nice, France
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Abstract
The osteoclast is the main effector of bone resorption. Failure in osteoclast differentiation or function leads to osteopetrosis, a bone disease characterized by an impaired bone resorption. Analysis of mouse models developing osteopetrosis as a consequence of naturally occurring mutations or gene knockouts allowed to establish the osteoclast differentiation pathway. Among these models, the oc/oc, the gl/gl and the Clcn7(-/-) mice present a phenotype similar to the one displayed by patients with infantile malignant osteopetrosis, the most severe form of osteopetrosis in human. Analysis of these models led to the identification of different mutations in the corresponding human genes TCIRG1, GL and CLCN7, in osteopetrotic patients. Mutations in the TCIRG1 gene seem the most frequent cause of malignant osteopetrosis and mutations in the CLCN7 gene seem the most frequent cause of type II osteopetrosis. Therefore, these three mouse models appear to be particularly well suited for the study of the osteoclast function in order to provide new insights in the therapy of osteopetrosis.
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Affiliation(s)
- Claudine Blin-Wakkach
- IAG, UMR 6549, Cnrs/UNSA, IFR50, Faculté de Médecine, Avenue de Valombrose, 06107 Nice 2, France
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Lerner UH. NEW MOLECULES IN THE TUMOR NECROSIS FACTOR LIGAND AND RECEPTOR SUPERFAMILIES WITH IMPORTANCE FOR PHYSIOLOGICAL AND PATHOLOGICAL BONE RESORPTION. ACTA ACUST UNITED AC 2004; 15:64-81. [PMID: 15059943 DOI: 10.1177/154411130401500202] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Osteoclasts are tissue-specific polykaryon bone-resorbing cells derived from the monocyte/macrophage hematopoietic lineage with specialized functions required for the adhesion of the cells to bone and the subsequent polarization of the cell membrane, secretion of acid to dissolve mineral crystals, and release of proteolytic enzymes to degrade the extracellular matrix proteins. Most pathological conditions in the skeleton lead to loss of bone due to excess osteoclastic bone resorption, including periodontal disease, rheumatoid arthritis, and osteoporosis. In rare cases, most of them genetic, patients with osteopetrosis exhibit sclerotic bone due either to a lack of osteoclasts or to non-functional osteoclasts. Mainly because of phenotypic findings in genetically manipulated mice or due to spontaneous mutations in humans, mice, and rats, several genes have been discovered as being crucial for osteoclast formation and activation. Recent breakthroughs in our understanding of osteoclast biology have revealed the critical roles in osteoclast differentiation played by RANKL, RANK, and OPG, three novel members of the tumor necrosis factor ligand and receptor superfamilies. The further study of these molecules and downstream signaling events are likely to provide a molecular basis for the development of new drugs for the treatment of diseases with excess or deficient osteoclastic bone resorption.
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Affiliation(s)
- Ulf H. Lerner
- Department of Oral Cell Biology, Umeå University, 901 87 Umeå, Sweden.
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Manolson MF, Yu H, Chen W, Yao Y, Li K, Lees RL, Heersche JNM. The a3 isoform of the 100-kDa V-ATPase subunit is highly but differentially expressed in large (>or=10 nuclei) and small (<or= nuclei) osteoclasts. J Biol Chem 2003; 278:49271-8. [PMID: 14504271 DOI: 10.1074/jbc.m309914200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Osteoclasts dissolve bone through acidification of an extracellular compartment by means of a multimeric vacuolar type H+-ATPase (V-ATPase). In mammals, there are four isoforms of the 100-kDa V-ATPase "a" subunit. Mutations in the a3 isoform result in deficient bone resorption and osteopetrosis, suggesting that a3 has a unique function in osteoclasts. It is thus surprising that several studies show a basal level of a3 expression in most tissues. To address this issue, we have compared a3 expression in bone with expression in other tissues. RNA blots revealed that the a3 isoform was expressed highest in bone and confirmed its expression (in decreasing order) in liver, kidney, brain, lung, spleen, and muscle. In situ hybridization on bone tissue sections revealed that the a3 isoform was highly expressed in multinucleated osteoclasts but not in mononuclear stromal cells, whereas the a1 isoform was expressed in both cell types at about the same level. We also found that a3 expression was greater in osteoclasts with 10 or more nuclei as compared with osteoclasts with five or fewer nuclei. We hypothesize that these differences in a3 expression may be associated with previously demonstrated differences between large and small osteoclasts with reference to their resorptive activity.
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Affiliation(s)
- Morris F Manolson
- Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1G6, Canada.
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