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Leung LL, Myles T, Morser J. Thrombin Cleavage of Osteopontin and the Host Anti-Tumor Immune Response. Cancers (Basel) 2023; 15:3480. [PMID: 37444590 DOI: 10.3390/cancers15133480] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/28/2023] [Accepted: 07/01/2023] [Indexed: 07/15/2023] Open
Abstract
Osteopontin (OPN) is a multi-functional protein that is involved in various cellular processes such as cell adhesion, migration, and signaling. There is a single conserved thrombin cleavage site in OPN that, when cleaved, yields two fragments with different properties from full-length OPN. In cancer, OPN has tumor-promoting activity and plays a role in tumor growth and metastasis. High levels of OPN expression in cancer cells and tumor tissue are found in various types of cancer, including breast, lung, prostate, ovarian, colorectal, and pancreatic cancer, and are associated with poor prognosis and decreased survival rates. OPN promotes tumor progression and invasion by stimulating cell proliferation and angiogenesis and also facilitates the metastasis of cancer cells to other parts of the body by promoting cell adhesion and migration. Furthermore, OPN contributes to immune evasion by inhibiting the activity of immune cells. Thrombin cleavage of OPN initiates OPN's tumor-promoting activity, and thrombin cleavage fragments of OPN down-regulate the host immune anti-tumor response.
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Affiliation(s)
- Lawrence L Leung
- Division of Hematology, Stanford University School of Medicine, Stanford, CA 94305, USA
- Veterans Affairs Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA
| | - Timothy Myles
- Division of Hematology, Stanford University School of Medicine, Stanford, CA 94305, USA
- Veterans Affairs Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA
| | - John Morser
- Division of Hematology, Stanford University School of Medicine, Stanford, CA 94305, USA
- Veterans Affairs Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA
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2
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Kaleta B. The role of osteopontin in kidney diseases. Inflamm Res 2018; 68:93-102. [PMID: 30456594 DOI: 10.1007/s00011-018-1200-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Osteopontin (OPN) is a pleiotropic glycoprotein expressed in various cell types in animals and in humans, including bone, immune, smooth muscle, epithelial and endothelial cells. Moreover, OPN is found in kidneys (in the thick ascending limbs of the loop of Henle and in distal nephrons) and urine. The protein plays an important role in mineralization and bone resorption. In addition, OPN is involved in the regulation of immunity and inflammation, angiogenesis and apoptosis. It was demonstrated that OPN and some OPN gene polymorphic variants are associated with the pathogenesis and progression of multiple disorders, such as cancer, autoimmune, neurodegenerative and cardiovascular diseases. Moreover, recent studies suggested that OPN is associated with the pathogenesis of renal failure. METHODS In this review, I briefly discussed the role of OPN and its gene polymorphisms in kidney physiology, as well as in various kidney diseases. FINDINGS AND CONCLUSION Most studies reported that OPN expression is elevated in urolithiasis, and also in acute and chronic kidney diseases, and in renal allograft dysfunction. Moreover, it was demonstrated that polymorphic variants of the OPN gene may be associated with renal failure. However, some reports suggested that OPN is essential for tubulogenesis, and that it inhibits calcium oxalate crystal formation and retention, nitric oxide synthesis, cell apoptosis and promotes cell regeneration. Thus, further studies are required to fully understand the role of OPN in kidney physiology and pathology. Eventually, these studies may result in the identification of OPN as a valuable marker for renal dysfunction prognosis and treatment.
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Affiliation(s)
- Beata Kaleta
- Department of Clinical Immunology, Transplantation Institute, Medical University of Warsaw, 59 Nowogrodzka St., 02-006, Warsaw, Poland.
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Ferreira LB, Lima RT, Bastos ACSDF, Silva AM, Tavares C, Pestana A, Rios E, Eloy C, Sobrinho-Simões M, Gimba ERP, Soares P. OPNa Overexpression Is Associated with Matrix Calcification in Thyroid Cancer Cell Lines. Int J Mol Sci 2018; 19:ijms19102990. [PMID: 30274371 PMCID: PMC6213506 DOI: 10.3390/ijms19102990] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 09/19/2018] [Accepted: 09/27/2018] [Indexed: 12/12/2022] Open
Abstract
Osteopontin (OPN) spliced variants (OPN-SV: OPNa, OPNb, and OPNc) are aberrantly expressed in tumors and frequently associated with cancer progression. This holds true for papillary thyroid carcinoma (PTC), which is the most common type of thyroid cancer (TC). PTC often presents with desmoplasia and dystrophic calcification, including psammoma bodies (PB). This work aimed to investigate total OPN (tOPN) and OPN-SV expression and their association with the presence of PB in the PTC classical variants (cPTC), as well as the involvement of OPN-SV in matrix calcification of TC cell lines. We found that cPTC samples presenting PB showed higher OPN expression levels. In TC cell lines, OPNa overexpression promotes higher matrix calcification and collagen synthesis when compared to that of clones overexpressing OPNb or OPNc. In response to OPN knockdown, calcification was inhibited, paralleled with the downregulation of calcification markers. In conclusion, our data evidenced that OPN expression is associated with the presence of PB in cPTC samples. Among the OPN-SV, OPNa is the main contributor to matrix calcification in tested TC cells, providing clues to a better understanding on the biology and ethiopathogenesis of the calcification process in TC cells.
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Affiliation(s)
- Luciana B Ferreira
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
- Research Coordination, National Institute of Cancer, Rio de Janeiro 20230-130, Brazil.
| | - Raquel T Lima
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
- Medical Faculty, University of Porto, 4200-319 Porto, Portugal.
| | | | - Andreia M Silva
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- INEB-Instituto de Engenharia Biomédica, 4200-135 Porto, Portugal.
- ICBAS-Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto, 4050-313 Porto, Portugal.
| | - Catarina Tavares
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
| | - Ana Pestana
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
| | - Elisabete Rios
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
- Medical Faculty, University of Porto, 4200-319 Porto, Portugal.
- Department of Pathology, Hospital de S. João, 4200-319 Porto, Portugal.
| | - Catarina Eloy
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
| | - Manuel Sobrinho-Simões
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
- Medical Faculty, University of Porto, 4200-319 Porto, Portugal.
- Department of Pathology, Hospital de S. João, 4200-319 Porto, Portugal.
| | - Etel R P Gimba
- Research Coordination, National Institute of Cancer, Rio de Janeiro 20230-130, Brazil.
- Natural Sciences Department, Health and Humanities Institute, Fluminense Federal University, Rio de Janeiro 28880-000, Brazil.
| | - Paula Soares
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
- Institute of Molecular Pathology and Immunology of the University of Porto (Ipatimup), 4200-135 Porto, Portugal.
- Medical Faculty, University of Porto, 4200-319 Porto, Portugal.
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Clemente N, Raineri D, Cappellano G, Boggio E, Favero F, Soluri MF, Dianzani C, Comi C, Dianzani U, Chiocchetti A. Osteopontin Bridging Innate and Adaptive Immunity in Autoimmune Diseases. J Immunol Res 2016; 2016:7675437. [PMID: 28097158 PMCID: PMC5206443 DOI: 10.1155/2016/7675437] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 10/02/2016] [Accepted: 10/19/2016] [Indexed: 12/21/2022] Open
Abstract
Osteopontin (OPN) regulates the immune response at multiple levels. Physiologically, it regulates the host response to infections by driving T helper (Th) polarization and acting on both innate and adaptive immunity; pathologically, it contributes to the development of immune-mediated and inflammatory diseases. In some cases, the mechanisms of these effects have been described, but many aspects of the OPN function remain elusive. This is in part ascribable to the fact that OPN is a complex molecule with several posttranslational modifications and it may act as either an immobilized protein of the extracellular matrix or a soluble cytokine or an intracytoplasmic molecule by binding to a wide variety of molecules including crystals of calcium phosphate, several cell surface receptors, and intracytoplasmic molecules. This review describes the OPN structure, isoforms, and functions and its role in regulating the crosstalk between innate and adaptive immunity in autoimmune diseases.
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Affiliation(s)
- Nausicaa Clemente
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Davide Raineri
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Giuseppe Cappellano
- Biocenter, Division for Experimental Pathophysiology and Immunology, Laboratory of Autoimmunity, Medical University of Innsbruck, Innsbruck, Austria
| | - Elena Boggio
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Francesco Favero
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Maria Felicia Soluri
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Chiara Dianzani
- Department of Drug Science and Technology, University of Torino, Torino, Italy
| | - Cristoforo Comi
- Department of Translational Medicine, Neurology Unit, “A. Avogadro” UPO, Novara, Italy
| | - Umberto Dianzani
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
| | - Annalisa Chiocchetti
- Department of Health Sciences and Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), “A. Avogadro” University of Piemonte Orientale (UPO), Novara, Italy
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Qin C, Baba O, Butler WT. Post-translational Modifications of SIBLING Proteins and Their Roles in Osteogenesis and Dentinogenesis. ACTA ACUST UNITED AC 2016; 15:126-36. [PMID: 15187031 DOI: 10.1177/154411130401500302] [Citation(s) in RCA: 344] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The extracellular matrix (ECM) of bone and dentin contains several non-collagenous proteins. One category of non-collagenous protein is termed the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family, that includes osteopontin (OPN), bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE). These polyanionic SIBLING proteins are believed to play key biological roles in the mineralization of bone and dentin. Although the specific mechanisms involved in controlling bone and dentin formation are still unknown, it is clear that some functions of the SIBLING family members are dependent on the nature and extent of post-translational modifications (PTMs), such as phosphorylation, glycosylation, and proteolytic processing, since these PTMs would have significant effects on their structure. OPN and BSP are present in the ECM of bone and dentin as full-length forms, whereas amino acid sequencing indicates that DMP1 and DSPP exist as proteolytically processed fragments that result from scission of X-Asp bonds. We hypothesized that the processing of DMP1 and DSPP is catalyzed by the PHEX enzyme, since this protein, an endopeptidase that is predominantly expressed in bone and tooth, has a strong preference for cleavage at the NH2-terminus of aspartyl residue. We envision that the proteolytic processing of DMP1 and DSPP may be an activation process that plays a significant, crucial role in osteogenesis and dentinogenesis, and that a failure in this processing would cause defective mineralization in bone and dentin, as observed in X-linked hypophosphatemic rickets.
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Affiliation(s)
- C Qin
- The Department of Endodontics and Periodontics, University of Texas-Houston Health Science Center, Dental Branch, Houston, TX 77030, USA.
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Abstract
Protection of mucosal tissues of the oral cavity, intestines, respiratory tract, and urogenital tract from the constant challenge of pathogens is achieved by the combined barrier function of the lining epithelia and specialized immune cells. Recent studies have indicated that osteopontin (OPN) has a pivotal role in the development of immune responses and in the tissue destruction and the subsequent repair processes associated with inflammatory diseases. While expression of OPN is increased in immune cells—including neutrophils, macrophages, T- and B-lymphocytes—and in epithelial, endothelial, and fibroblastic cells of inflamed tissues, deciphering the specific functions of OPN has been difficult. In part, this is due to the broad range of biological activities of OPN that are mediated by multiple receptors which recognize several signaling motifs whose activities are influenced by post-translational modifications and proteolytic processing of OPN. Understanding the role of OPN in mucosal inflammation is further complicated by its contributions to the barrier function of the lining epithelia and the complexity of the specialized mucosal immune system. In an attempt to provide some insights into the involvement of OPN in mucosal diseases, this review summarizes current knowledge of the biological activities of OPN involved in the development of inflammatory responses and in wound healing, and indicates how these activities may affect the protection of mucosal tissues.
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Affiliation(s)
- J Sodek
- CIHR Group in Matrix Dynamics, Faculty of Dentistry, University of Toronto, ON, Canada
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Storan MJ, Heazlewood SY, Heazlewood CK, Haylock DN, Alexander WS, Neaves RJ, Oteiza A, Nilsson SK. Brief Report: Factors Released by Megakaryocytes Thrombin Cleave Osteopontin to Negatively Regulate Hematopoietic Stem Cells. Stem Cells 2015; 33:2351-7. [DOI: 10.1002/stem.2038] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 03/28/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Melonie J. Storan
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
| | - Shen Y. Heazlewood
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
- Australian Regenerative Medicine Institute; Monash University; Melbourne Australia
| | - Chad K. Heazlewood
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
- Australian Regenerative Medicine Institute; Monash University; Melbourne Australia
| | - David N. Haylock
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
- Australian Regenerative Medicine Institute; Monash University; Melbourne Australia
| | - Warren S. Alexander
- Cancer and Hematology Division, Walter and Eliza Hall Institute of Medical Research; Melbourne Victoria Australia
- Department of Medical Biology; The University of Melbourne; Melbourne Victoria Australia
| | - Rebecca J. Neaves
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
- Department of Anatomy and Developmental Cell Biology; Monash University; Melbourne Victoria Australia
| | - Ana Oteiza
- Department of Medical Biology; University of Tromsø; Tromsø Norway
| | - Susan K. Nilsson
- Manufacturing Flagship; Commonwealth Scientific and Industrial Research Organization; Melbourne Victoria Australia
- Australian Regenerative Medicine Institute; Monash University; Melbourne Australia
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8
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Johnson GA, Burghardt RC, Bazer FW. Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep. J Anim Sci Biotechnol 2014; 5:56. [PMID: 25671104 PMCID: PMC4322467 DOI: 10.1186/2049-1891-5-56] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 11/25/2014] [Indexed: 11/10/2022] Open
Abstract
Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species.
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Affiliation(s)
- Greg A Johnson
- />Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458 USA
| | - Robert C Burghardt
- />Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458 USA
| | - Fuller W Bazer
- />Department of Animal Science, Texas A&M University, College Station, TX 77843 USA
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Kohri K, Yasui T, Okada A, Hirose M, Hamamoto S, Fujii Y, Niimi K, Taguchi K. Biomolecular mechanism of urinary stone formation involving osteopontin. ACTA ACUST UNITED AC 2012; 40:623-37. [PMID: 23124115 DOI: 10.1007/s00240-012-0514-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 09/13/2012] [Indexed: 12/15/2022]
Abstract
Urinary stones consist of two phases-an inorganic (mineral) phase and an organic (matrix) phase. Studies on the organic components of kidney stones have been undertaken later than those on the inorganic components. After osteopontin was identified as one of the matrix components, the biomolecular mechanism of urinary stone formation became clearer. It also triggered the development of new preventive treatments. Osteopontin expression is sporadically observed in normal distal tubular cells and is markedly increased in stone-forming kidneys. Calcium oxalate crystals adhering to renal tubular cells are incorporated into cells by the involvement of osteopontin. Stimulation of crystal-cell adhesion impairs the opening of mitochondrial permeability transition pores (mPTP) in tubular cells and produces oxidative stress, apoptosis, and osteopontin expression. Macrophages phagocytose and digest a small amount of crystals, but many crystals aggregate into a mass containing osteopontin and epithelial cell debris and are excreted into the renal tubular lumen, becoming nuclei of urinary stones. This biomolecular mechanism is similar to atherosclerotic calcification. Based on these findings, new preventive treatments have been developed. Dietary control such as low-cholesterol intake and the ingestion of antioxidative foods and vegetables have successfully reduced the 5-year recurrence rate. Osteopontin antibodies and cyclosporine A, which blocks the opening of mPTP, have markedly inhibited the expression of osteopontin and urinary stone formation in animal models.
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Affiliation(s)
- Kenjiro Kohri
- Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, 467-8601, Japan.
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Pre- and post-translational regulation of osteopontin in cancer. J Cell Commun Signal 2011; 5:111-22. [PMID: 21516514 DOI: 10.1007/s12079-011-0130-6] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 03/15/2011] [Indexed: 12/15/2022] Open
Abstract
Osteopontin (OPN) is a matricellular protein that binds to a number of cell surface receptors including integrins and CD44. It is expressed in many tissues and secreted into body fluids including blood, milk and urine. OPN plays important physiological roles in bone remodeling, immune response and inflammation. It is also a tumour-associated protein, and elevated OPN levels are associated with tumour formation, progression and metastasis. Research has revealed a promising role for OPN as a cancer biomarker. OPN is subject to alternative splicing, as well as post-translational modifications such as phosphorylation, glycosylation and proteolytic cleavage. Functional differences have been revealed for different isoforms and post-translational modifications. The pattern of isoform expression and post-translational modification is cell-type specific and may influence the potential role of OPN in malignancy and as a cancer biomarker.
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Lund SA, Giachelli CM, Scatena M. The role of osteopontin in inflammatory processes. J Cell Commun Signal 2009; 3:311-22. [PMID: 19798593 PMCID: PMC2778587 DOI: 10.1007/s12079-009-0068-0] [Citation(s) in RCA: 370] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Accepted: 09/09/2009] [Indexed: 01/01/2023] Open
Abstract
Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions. OPN is involved in normal physiological processes and is implicated in the pathogenesis of a variety of disease states, including atherosclerosis, glomerulonephritis, cancer, and several chronic inflammatory diseases. Through interactions with several integrins, OPN mediates cell migration, adhesion, and survival in many cell types. OPN also functions as a Th1 cytokine, promotes cell-mediated immune responses, and plays a role in chronic inflammatory and autoimmune diseases. Besides its function in inflammation, OPN is also a regulator of biomineralization and a potent inhibitor of vascular calcification.
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Affiliation(s)
- Susan Amanda Lund
- Department of Bioengineering, University of Washington, Box 358056, Seattle, WA 98195 USA
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Jheon A, Bansal AK, Zhu B, Ganss B, Cheifetz S, Sodek J. Characterisation of the constitutive over-expression of AJ18 in a novel rat stromal bone marrow cell line (D8-SBMC). Arch Oral Biol 2009; 54:705-16. [DOI: 10.1016/j.archoralbio.2009.04.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/08/2009] [Accepted: 04/21/2009] [Indexed: 01/20/2023]
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Thrombin-cleaved osteopontin regulates hemopoietic stem and progenitor cell functions through interactions with alpha9beta1 and alpha4beta1 integrins. Blood 2009; 114:49-59. [PMID: 19417209 DOI: 10.1182/blood-2009-01-197988] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Osteopontin (OPN), a multifunctional acidic glycoprotein, expressed by osteoblasts within the endosteal region of the bone marrow (BM) suppresses the proliferation of hemopoietic stem and progenitor cells and also regulates their lodgment within the BM after transplantation. Herein we demonstrate that OPN cleavage fragments are the most abundant forms of this protein within the BM. Studies aimed to determine how hemopoietic stem cells (HSCs) interact with OPN revealed for the first time that murine and human HSCs express alpha(9)beta(1) integrin. The N-terminal thrombin cleavage fragment of OPN through its binding to the alpha(9)beta(1) and alpha(4)beta(1) integrins plays a key role in the attraction, retention, regulation, and release of hemopoietic stem and progenitor cells to, in, and from their BM niche. Thrombin-cleaved OPN (trOPN) acts as a chemoattractant for stem and progenitor cells, mediating their migration in a manner that involves interaction with alpha(9)beta(1) and alpha(4)beta(1) integrins. In addition, in the absence of OPN, there is an increased number of white blood cells and, specifically, stem and progenitor cells in the peripheral circulation.
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Kazanecki CC, Uzwiak DJ, Denhardt DT. Control of osteopontin signaling and function by post-translational phosphorylation and protein folding. J Cell Biochem 2008; 102:912-24. [PMID: 17910028 DOI: 10.1002/jcb.21558] [Citation(s) in RCA: 211] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Osteopontin (OPN) plays roles in a variety of cellular processes from bone resorption and extracellular matrix (ECM) remodeling to immune cell activation and inhibition of apoptosis. Because it binds receptors (integrins, CD44 variants) typically engaged by ECM molecules, OPN acts as a "soluble" ECM molecule. A persistent theme throughout the characterization of how OPN functions has been the importance of phosphorylation. The source of the OPN used in specific experiments and the location of modified sites is an increasingly important consideration for OPN research. We review briefly some of the ways OPN impacts on the biology of mammalian systems with an emphasis on the importance of serine phosphorylation in modulating its signaling ability. We describe experiments that support the hypothesis that differences in the post-translational phosphorylation of OPN expressed by different cell types regulate how it impacts on target cells. Analyses of OPN's potential secondary structure reveal a possible beta-sheet conformation that offers an interpretation of certain experimental observations, specifically the effect of thrombin cleavage; it is consistent with an interaction between the C-terminal region of the protein and the central integrin-binding RGD sequence.
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Hincke MT, Chien YC, Gerstenfeld LC, McKee MD. Colloidal-gold immunocytochemical localization of osteopontin in avian eggshell gland and eggshell. J Histochem Cytochem 2008; 56:467-76. [PMID: 18256019 DOI: 10.1369/jhc.2008.950576] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
During mineralization of the avian eggshell, there is a sequential and orderly deposition of both matrix and mineral phases. Therefore, the eggshell is an excellent model for studying matrix-mineral relationships and the regulation of mineralization. Osteopontin, as an inhibitor of crystal growth, potently influences the formation of calcium phosphate and calcium carbonate biominerals. The purpose of this study was to characterize matrix-mineral relationships, specifically for osteopontin, in the avian eggshell using high-resolution transmission (TEM) and scanning (SEM) electron microscopy to gain insight into how calcite crystal growth is structured and compartmentalized during eggshell mineralization. Osteopontin was localized at the ultrastructural level by colloidal-gold immunocytochemistry. In EDTA-decalcified eggshell, an extensive matrix network was observed by TEM and SEM throughout all regions and included interconnected fibrous sheets, irregularly shaped aggregates, vesicular structures, protein films, and isolated protein fibers. Osteopontin was associated with protein sheets in the highly mineralized palisades region; some of these features defined boundaries that compartmentalized different eggshell structural units. In fractured and undecalcified eggshell, osteopontin was immunolocalized on the {104} crystallographic faces of calcite-its natural cleavage plane. The specific occlusion of osteopontin into calcite during mineralization may influence eggshell structure to modify its fracture resistance.
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Affiliation(s)
- Maxwell T Hincke
- Faculty of Dentistry, 3640 University Street, Montreal, Quebec, Canada H3A 2B2
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16
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Joyce MM, González JF, Lewis S, Woldesenbet S, Burghardt RC, Newton GR, Johnson GA. Caprine uterine and placental osteopontin expression is distinct among epitheliochorial implanting species. Placenta 2005; 26:160-70. [PMID: 15708117 DOI: 10.1016/j.placenta.2004.05.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/17/2004] [Indexed: 10/26/2022]
Abstract
Osteopontin (OPN) is the most highly up-regulated extracellular matrix/adhesion molecule in the uterus of humans and domestic animals as it becomes receptive to implantation. Studies in sheep and pigs have shown that OPN is a component of ovine and porcine histotroph characterized by a complex temporal and spatial pattern of uterine and conceptus expression involving immune, epithelial, and stromal cells. It is proposed that these expression events are orchestrated to contribute to conceptus attachment and placentation. However, differences in OPN expression between sheep and pigs have been detected that relate to differences in placentation. Therefore, this study examined OPN expression in the caprine uterus and conceptus to gain insight into mechanisms underlying OPN function(s) during pregnancy through comparative analysis of differences in placentation between pigs, sheep, and goats. Goats were hysterectomized (n = 5/day) on Days 5, 11, 13, 15, 17 or 19 of the estrous cycle, and Days 5, 11, 13, 15, 17, 19 or 25 of pregnancy. Slot-blot hybridization showed increases in endometrial OPN mRNA beginning on Day 17 of the estrous cycle and Day 19 of pregnancy. In situ hybridization localized OPN mRNA to endometrial glandular epithelium (GE), Day 25 myometrium, and cells scattered within the placenta hypothesized to be immune. Immunofluorescence microscopy detected OPN protein on the apical surface of endometrial lumenal epithelium (LE), in GE, and on conceptus (Tr). Western blot analysis detected primarily the native 70-kDa OPN protein in endometrial extracts from the estrous cycle and pregnancy, as well as in uterine flushings from pregnant goats. Co-induction of OPN and alpha-smooth muscle actin, but not desmin proteins, was observed in uterine stroma by Day 25 of pregnancy. OPN in cyclic GE, Day 25 myometrium, and desmin-negative endometrial stroma is unique and reflects subtle differences among superficial implanting species that correlate with the depth of Tr invasion.
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Affiliation(s)
- M M Joyce
- Department of Veterinary Anatomy and Public Health, Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, TX, USA
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17
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Kleinman JG, Wesson JA, Hughes J. Osteopontin and Calcium Stone Formation. ACTA ACUST UNITED AC 2004; 98:p43-7. [DOI: 10.1159/000080263] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Abstract
Osteopontin (OPN) is an acidic member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of extracellular matrix proteins/cytokines that undergoes extensive posttranslational modification, including phosphorylation, glycosylation, and cleavage, yielding molecular mass variants ranging in size from 25 to 75 kDa. The result is a versatile protein(s) with multiple functions arising from its role as a mediator of cell-cell and cell-extracellular matrix (ECM) communication that encompass both normal and tumorigenic developmental processes, immunological responses during inflammation and wound healing, and biomineralization. Studies in primates, pigs, sheep, and rodents have revealed that OPN is a major constituent of the uterine-placental microenvironment with influence as 1) a component of histotroph required for adhesion and signal transduction at the uterine-placental interface throughout pregnancy, 2) a gene product expressed by uterine stroma contributing to a decidualization-like transformation that correlates with the degree of conceptus invasiveness, and 3) a product of resident uterine and placental immune cells that may regulate their behavior and cytokine production. This minireview summarizes information regarding uterine and placental expression of OPN that has accumulated over the past 15 yr, and we briefly describe structural/functional properties of this protein that are likely relevant to its role(s) during pregnancy. Comparative studies have offered insights into the potential hormonal/cytokine, cellular, and molecular mechanisms underlying OPN-mediated adhesion, remodeling, and cell-cell/cell-ECM communication within the uterus and placenta. OPN has the potential to profoundly impact pregnancy, and investigators are now challenged to focus on the mechanistic nature of the functions of this multifaceted and major component of the uterine-placental microenvironment.
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Affiliation(s)
- Greg A Johnson
- Center for Animal Biotechnology and Genomics, College of Veterinary Medicine, Texas A and M University, College Station, TX 77843, USA.
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Fernandez MS, Escobar C, Lavelin I, Pines M, Arias JL. Localization of osteopontin in oviduct tissue and eggshell during different stages of the avian egg laying cycle. J Struct Biol 2003; 143:171-80. [PMID: 14572472 DOI: 10.1016/j.jsb.2003.08.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The avian eggshell is an acellular bioceramic containing organic and inorganic phases that are sequentially assembled during the time the egg moves along the oviduct. As it has been demonstrated in other mineralized tissues, mineralization of the eggshell is regulated by extracellular matrix proteins especially the anionic side chains of proteoglycans. Among them, osteopontin has been found in the avian eggshell and oviduct. However, its precise localization in the eggshell or in different oviduct regions during eggshell formation, nor its function have been established. By using anti-osteopontin antibody (OPN 1), we studied its immunolocalization in the isthmus, red isthmus and shell gland of the oviduct, and in the eggshell during formation. In the eggshell, osteopontin was localized in the core of the non-mineralized shell membrane fibers, in the base of the mammillae and in the outermost part of the palisade. In the oviduct, OPN 1 was localized in the ciliated epithelial but not in the tubular gland cells of the isthmus, in the ciliated epithelial cells of the red isthmus, and in the non-ciliated epithelial cells of the shell gland. The occurrence of osteopontin in each of the oviduct regions, coincided with the concomitant presence of the egg in such region. Considering the reported inhibitory function of osteopontin in other mineralized systems, together with its main occurrence in the non-mineralized parts of the eggshell and at the outermost part of the shell, suggests that this molecule could be part of the mechanism regulating the eggshell calcification.
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Affiliation(s)
- M S Fernandez
- Faculty of Veterinary and Animal Sciences and Center for Advanced Interdisciplinary Research in Materials (CIMAT), University of Chile, Santiago, Chile
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20
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Abstract
OBJECTIVE We evaluated whether osteopontin (OPN) and other proteins with the RGD sequence as in OPN (RGD family proteins) that are present in renal tubular cells (fibronectin [FN], Tamm-Horsfall glycoprotein [THP], vitronectin [VN], and laminin [LN]) inhibit the aggregation and growth of calcium oxalate (CaOx) crystals by a novel seed crystal method using collagen granules (CG) with and without OPN adhered on the surface. We also evaluated the effect of solid phase OPN, FN and THP in which the relationship between their proteins and CaOx crystallization was reported. Moreover, the state and time-course changes in CaOx crystals adhered to CG were observed under scanning electron microscopy (SEM). METHODS The inhibitory activity (IA) on the aggregation and growth of CaOx crystals was measured in vitro by the conventional seed crystal method using isotopes. In this study, the following nine samples were used: OPN alone; FN alone; THP alone; VN alone; LN alone; CG alone; and CG with OPN, FN, or THP adhered on the surface (OPN/FN/THP-immobilized CG). In addition, the state and time-course changes in CaOx crystals adhered to CG were evaluated by SEM. RESULTS Using the conventional seed crystal method, the following values of IA were obtained: 91.7% (37.5 micro g/ml) for OPN, 5.0% (100 micro g/ml) for FN, 2.0% (100 micro g/ml) for THP, 3.0% (100 micro g/ml) for VN, and 1.0% (100 micro g/ml) for LN. However, the value of IA obtained by our seed crystal method using CG was 92.1% (180cm(2)/5ml PBS) when CG alone was used. Although the value of IA was decreased by 33.6% when OPN-immobilized CG was used, it did not significantly change when FN/THP-immobilized CG was used. When CG alone was used, the evaluation of CaOx crystallization by SEM demonstrated mild adherence and aggregation of CaOx crystal suspension (seed crystals) on the CG surface, although newly formed crystals only slightly adhered to the CG surface. When OPN-immobilized CG was used, marked adherence and aggregation of seed crystals were observed, in addition to the relatively increased adherence of newly formed crystals. When FN/THP-immobilized CG was used, newly formed crystals only slightly adhered to the CG surface, although the degree of seed crystal adherence and aggregation did not significantly change. CONCLUSIONS These findings suggest that the immobilization of OPN to the CG surface enhances the adherence and aggregation of seed crystals, as well as enhancing the adherence of newly formed crystals, resulting in decreased IA of CG (overall promotion of crystal deposition). Therefore, the results of this study clarified that OPN enhances the formation and aggregation of CaOx crystals in this experimental system.
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Affiliation(s)
- Eiji Konya
- Department of Urology, Kinki University School of Medicine, 377-2, Ohno-Higashi, Osaka-Sayama, Osaka, 589-8511, Japan.
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Koguchi Y, Kawakami K, Kon S, Segawa T, Maeda M, Uede T, Saito A. Penicillium marneffei causes osteopontin-mediated production of interleukin-12 by peripheral blood mononuclear cells. Infect Immun 2002; 70:1042-8. [PMID: 11854181 PMCID: PMC127744 DOI: 10.1128/iai.70.3.1042-1048.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the role of osteopontin (OPN) in interleukin-12 (IL-12) production from peripheral blood mononuclear cells (PBMCs) stimulated with Penicillium marneffei. Kinetic studies showed that OPN synthesis preceded that of IL-12 at both mRNA and protein levels when PBMCs were cocultured with P. marneffei. Treatment with anti-OPN monoclonal antibodies (MAb) significantly suppressed IL-12 secretion. Furthermore, native OPN induced a profound level of synthesis of IL-12 from noninfected PBMCs. The major cellular source of OPN was monocytes, because depletion of CD14(+) cells resulted in the abrogation of such production. We also examined the regulatory role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in OPN secretion from P. marneffei-stimulated PBMCs. Neutralizing anti-GM-CSF MAb significantly reduced OPN secretion, and treatment with this cytokine induced OPN production from both infected and noninfected PBMCs. Finally, antagonists against the mannose receptor but not the beta-glucan receptor almost completely abrogated the production of OPN. Our results demonstrated that OPN secreted from monocytes is involved in the production of IL-12 from PBMCs after stimulation with P. marneffei and that OPN production is regulated by GM-CSF. Our results also indicated the possible involvement of the mannose receptor as a signal-transducing receptor for triggering the secretion of OPN by P. marneffei-stimulated PBMCs.
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Affiliation(s)
- Yoshinobu Koguchi
- First Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
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Ishigaki R, Takagi M, Igarashi M, Ito K. Gene expression and immunohistochemical localization of osteonectin in association with early bone formation in the developing mandible. THE HISTOCHEMICAL JOURNAL 2002; 34:57-66. [PMID: 12365801 DOI: 10.1023/a:1021352110531] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have compared the expression of osteonectin with that of osteocalcin and bone sialoprotein during bone formation in the rat mandible, using in situ hybridization and immunohistochemistry. Expression of osteonectin, osteocalcin and bone sialoprotein mRNAs were first observed in newly differentiated osteoblasts of the developing mandible at embryonic day 15 (E15) and subsequently increased with the number of osteoblasts through E20. Definitive osteonectin immunostaining was observed in newly differentiated osteoblasts, but not in the intercellular unmineralized matrix. Immunostaining for osteocalcin and bone sialoprotein was visible in osteoblasts and unmineralized matrix. Concomitant with the initiation of matrix mineralization at E16, mineralized bone matrix showed osteocalcin and bone sialoprotein immunostaining, but lacked osteonectin immunostaining. The same staining profile was observed during subsequent phases of bone formation at E17-20. However, sequential demineralization with ethanolic trimethylammonium EDTA and protease digestion of tissue sections demonstrated prominent osteonectin immunostaining of the mineralized bone matrix. Western blot analysis of osteonectin in extracts of fresh specimens at E18 and 20 revealed that an EDTA extract contains osteonectin having M, approximately 50 kDa. These results indicate that newly differentiated osteoblasts synthesize and secrete osteonectin, which is mainly incorporated into the mineralized bone matrix and becomes a specific component of developing manibula of foetal rats.
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Affiliation(s)
- Ryo Ishigaki
- Department of Periodontology, Nihon University School of Dentistry, Tokyo, Japan
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23
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Weber GF. The metastasis gene osteopontin: a candidate target for cancer therapy. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1552:61-85. [PMID: 11825687 DOI: 10.1016/s0304-419x(01)00037-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Malignant tumors are characterized by dysregulated growth control, overcoming of replicative senescence, and metastasis formation. Current therapeutic regimens mostly exert their effects through inhibition of cell cycle progression, leaving two major components of transformation untouched. The cytokine osteopontin is essential for the dissemination of various cancers. Past research has implied several modes in which osteopontin and its main receptors on tumor cells can be suppressed. Osteopontin expression is inhibitable on the levels of gene transcription and the RNA message, and the osteopontin protein can be blocked with antibodies or synthetic peptides. The osteopontin receptor CD44 has been targeted by diverse therapeutic strategies, including cytotoxic and immunotherapeutic approaches. The receptor integrin alpha(V)beta(3) contributes not only to tumor cell dissemination, but also to angiogenesis and osteolysis in bone metastases. Small molecule inhibitors of this receptor are under study as drug candidates. Because receptors and cytokine ligands that mediate metastasis formation are sparsely expressed in the adult healthy organism and are more readily reached by pharmaceuticals than intracellular drug targets they may represent a particularly suitable focus for therapeutic intervention.
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Affiliation(s)
- G F Weber
- Department of Radiation Oncology, New England Medical Center and Tufts University Medical School, 750 Washington Street, NEMC #824, Boston, MA 02111, USA.
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Javed A, Barnes GL, Jasanya BO, Stein JL, Gerstenfeld L, Lian JB, Stein GS. runt homology domain transcription factors (Runx, Cbfa, and AML) mediate repression of the bone sialoprotein promoter: evidence for promoter context-dependent activity of Cbfa proteins. Mol Cell Biol 2001; 21:2891-905. [PMID: 11283267 PMCID: PMC86918 DOI: 10.1128/mcb.21.8.2891-2905.2001] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of the bone sialoprotein (BSP) gene, a marker of bone formation, is largely restricted to cells in mineralized tissues. Recent studies have shown that the Cbfa1 (also known as Runx2, AML-3, and PEBP2alphaA) transcription factor supports commitment and differentiation of progenitor cells to hypertrophic chondrocytes and osteoblasts. This study addresses the functional involvement of Cbfa sites in expression of the Gallus BSP gene. Gel mobility shift analyses with nuclear extracts from ROS 17/2.8 osteoblastic cells revealed that multiple Cbfa consensus sequences are functional Cbfa DNA binding sites. Responsiveness of the 1.2-kb Gallus BSP promoter to Cbfa factors Cbfa1, Cbfa2, and Cbfa3 was assayed in osseous and nonosseous cells. Each of the Cbfa factors mediated repression of the wild-type BSP promoter, in contrast to their well known activation of various hematopoietic and skeletal phenotypic genes. Suppression of BSP by Cbfa factors was not observed in BSP promoters in which Cbfa sites were deleted or mutated. Expression of the endogenous BSP gene in Gallus osteoblasts was similarly downregulated by forced expression of Cbfa factors. Our data indicate that Cbfa repression of the BSP promoter does not involve the transducin-like enhancer (TLE) proteins. Neither coexpression of TLE1 or TLE2 nor the absence of the TLE interaction motif of Cbfa1 (amino acids 501 to 513) influenced repressor activity. However, removal of the C terminus of Cbfa1 (amino acids 362 to 513) relieved suppression of the BSP promoter. Our results, together with the evolutionary conservation of the seven Cbfa sites in the Gallus and human BSP promoters, suggest that suppressor activity by Cbfa is of significant physiologic consequence and may contribute to spatiotemporal expression of BSP during bone development.
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Affiliation(s)
- A Javed
- Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0106, USA
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Sodek J, Ganss B, McKee MD. Osteopontin. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2001; 11:279-303. [PMID: 11021631 DOI: 10.1177/10454411000110030101] [Citation(s) in RCA: 829] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Osteopontin (OPN) is a highly phosphorylated sialoprotein that is a prominent component of the mineralized extracellular matrices of bones and teeth. OPN is characterized by the presence of a polyaspartic acid sequence and sites of Ser/Thr phosphorylation that mediate hydroxyapatite binding, and a highly conserved RGD motif that mediates cell attachment/signaling. Expression of OPN in a variety of tissues indicates a multiplicity of functions that involve one or more of these conserved motifs. While the lack of a clear phenotype in OPN "knockout" mice has not established a definitive role for OPN in any tissue, recent studies have provided some novel and intriguing insights into the versatility of this enigmatic protein in diverse biological events, including developmental processes, wound healing, immunological responses, tumorigenesis, bone resorption, and calcification. The ability of OPN to stimulate cell activity through multiple receptors linked to several interactive signaling pathways can account for much of the functional diversity. In this review, we discuss the structural features of OPN that relate to its function in the formation, remodeling, and maintenance of bones and teeth.
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Affiliation(s)
- J Sodek
- MRC Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, ON, Canada.
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26
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Mizuno M, Fujisawa R, Kuboki Y. Type I collagen-induced osteoblastic differentiation of bone-marrow cells mediated by collagen-alpha2beta1 integrin interaction. J Cell Physiol 2000; 184:207-13. [PMID: 10867645 DOI: 10.1002/1097-4652(200008)184:2<207::aid-jcp8>3.0.co;2-u] [Citation(s) in RCA: 298] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bone marrow cells are multipotent cells. When bone marrow cells were cultured with type I collagen matrix gels, they showed high alkaline phosphatase activity, collagen synthesis, and formed mineralized tissues. Furthermore, cells expressed osteocalcin and bone sialoprotein genes, which are osteoblast-specific genes. These findings indicate that type I collagen matrix gels induce osteoblastic differentiation of bone marrow cells. Type I collagen interacts with the alpha 2 beta 1 integrin receptor on the cell membrane and mediates extracellular signals into cells. DGEA peptide is a cell-binding domain of type I collagen molecule. When collagen-integrin interaction was interrupted by the addition of Asp-Gly-Glu-Ala (DGEA) peptide to the culture, the expression of osteoblastic phenotypes of bone marrow cells was inhibited. Furthermore, anti-alpha 2 integrin antibody, which interacts with alpha subunit of integrin and blocks the binding of integrin with collagen, suppressed the expression of osteoblastic phenotypes. These findings imply that collagen-alpha 2 beta 1 integrin interaction is an important signal for the osteoblastic differentiation of bone marrow cells.
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Affiliation(s)
- M Mizuno
- Department of Biochemistry, School of Dentistry, Hokkaido University, Sapporo, Japan
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27
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Jono S, Peinado C, Giachelli CM. Phosphorylation of osteopontin is required for inhibition of vascular smooth muscle cell calcification. J Biol Chem 2000; 275:20197-203. [PMID: 10766759 DOI: 10.1074/jbc.m909174199] [Citation(s) in RCA: 238] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Osteopontin (OPN) is a non-collagenous, glycosylated phosphoprotein associated with biomineralization in osseous tissues, as well as ectopic calcification. We previously reported that osteopontin was co-localized with calcified deposits in atherosclerotic lesions, and that osteopontin potently inhibits calcium deposition in a human smooth muscle cell (HSMC) culture model of vascular calcification. In this report, the role of phosphorylation in osteopontin's mineralization inhibitory function was examined. The ability of OPN to inhibit calcification completely depended on post-translational modifications, since bacteria-derived recombinant OPN did not inhibit HSMC mineralization. Following casein kinase II treatment, phosphorylated OPN (P-OPN) dose-dependently inhibited calcification of HSMC cultured in vitro about as effectively as native OPN. The inhibitory effect of osteopontin depended on the extent of phosphorylation. To determine the specific structural domains of OPN important for inhibition of calcification, we compared OPN fragments (N-terminal, C-terminal, and full-length), and compared the inhibitory effect of both phosphorylated and non-phosphorylated fragments. While none of the non-phosphorylated OPN fragments effected calcification, P-OPN caused dose dependent inhibition of HSMC calcification. P-OPN was treated with alkaline phosphatase to create dephosphorylated OPN. Dephosphorylated OPN did not have an inhibitory effect on calcification. The expression of OPN mRNA and P-OPN secretion by HSMC were decreased in a time-dependent manner during culture calcification. These results indicate that phosphorylation is required for the inhibitory effect of OPN on HSMC calcification, and that regulation of OPN phosphorylation represents one way in which mineralization may be controlled by cells.
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Affiliation(s)
- S Jono
- Department of Bioengineering, University of Washington, Seattle, Washington, 98195, USA
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Ganss B, Kim RH, Sodek J. Bone sialoprotein. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2000; 10:79-98. [PMID: 10759428 DOI: 10.1177/10454411990100010401] [Citation(s) in RCA: 411] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The search for a protein nucleator of hydroxyapatite crystal formation has been a focus for the isolation and characterization of the major non-collagenous proteins in bone. Of the proteins characterized to date, bone sialoprotein (BSP) has emerged as the only bona fide candidate for nucleation. BSP is a highly glycosylated and sulphated phosphoprotein that is found almost exclusively in mineralized connective tissues. Characteristically, polyglutamic acid and arginine-glycine-aspartate (RGD) motifs with the ability to bind hydroxyapatite and cell-surface integrins, respectively, have been conserved in the protein sequence. Expression of the BSP gene, which is induced in newly formed osteoblasts, is up-regulated by hormones and cytokines that promote bone formation and down-regulated by factors that suppress bone formation. Thus, BSP has the biophysical and chemical properties of a nucleator, and its temporo-spatial expression coincides with de novo mineralization in bone and cementum. Moreover, BSP has been associated with mineral crystal formation in several pathologies, including breast carcinomas. However, the ability of BSP to mediate cell attachment and to signal through the RGD motif points to alternate functions for BSP which need further investigation. In combination, the hydroxyapatite-binding polyglutamic acid sequences and the RGD provide bi-functional entities through which BSP may mediate the targeting and attachment of normal and metastasizing cells to the bone surface.
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Affiliation(s)
- B Ganss
- Medical Research Council Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Ontario, Canada
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Lavelin I, Yarden N, Ben-Bassat S, Bar A, Pines M. Regulation of osteopontin gene expression during egg shell formation in the laying hen by mechanical strain. Matrix Biol 1998; 17:615-23. [PMID: 9923654 DOI: 10.1016/s0945-053x(98)90112-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The aim of this study is to evaluate the regulation of the osteopontin (OPN) gene expression by non-hormonal stimuli, such as calcium flux and mechanical strain during the daily egg cycle in the oviduct of the laying hen. After the egg enters the eggshell gland (ESG), the OPN gene is expressed by the epithelium cells in two waves: first by the basal cells and only then by the apical cells of the epithelium. A reduction in OPN gene expression was observed 1 h prior to laying. The calbindin gene, which marks the onset of calcification, was found to be expressed in the glandular epithelium starting 2 h after OPN gene expression. In addition, the formation of soft shells was accompanied by a reduction in calbindin, but not in OPN, gene expression. The application of a mechanical strain comparable to that induced by an egg led to induction of OPN gene expression at a normally quiescent phase in the cyclical expression of this gene. The induction of the gene was time- and strain-dependent and temporally similar to that induced by the entry of the egg into the ESG. In contrast, the calbindin gene was not affected by mechanical strain. The ESG of the laying hen provides a system to study the effect of a mechanical strain on matrix protein production in vivo, in a relevant physiological setting. The finding suggests that, in contrast to calbindin, OPN gene expression is not regulated by calcium flux but rather by the mechanical strain imposed by the resident egg.
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Affiliation(s)
- I Lavelin
- Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
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Kido J, Nishikawa S, Ishida H, Yamashita K, Kitamura S, Kohri K, Nagata T. Identification of calprotectin, a calcium binding leukocyte protein, in human dental calculus matrix. J Periodontal Res 1997; 32:355-61. [PMID: 9210089 DOI: 10.1111/j.1600-0765.1997.tb00545.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Calprotectin is a calcium binding protein produced by leukocytes, macrophages and epithelial cells, and its levels in several tissues increase during infections and in many inflamed areas, suggesting that it may be an indicator of inflammatory activity. Osteopontin is a prominent phosphorylated glycoprotein in bone matrix, having calcium binding capacity. Recently, it has been reported that calprotectin and osteopontin are present in urinary stones (pathological mineralized masses in the body), and that these proteins may be involved in their formation. Dental calculus formed by mineralization of dental plaque is an inflammatory factor which may contribute to periodontal disease. It contains many organic components involved in mineralization. We recently found osteopontin molecules in human dental calculus and suggested that the components of its matrix may be similar to those of urinary stones. In this study, we investigated the presence of calprotectin in human dental calculus by immunohistochemical and immunoblotting analyses using a specific antibody for calprotectin. After fixation and demineralization of dental calculi adhered to tooth roots, sections embedded in paraffin were immunoreacted with the antibody for calprotectin and positive immunostaining for calprotectin was observed. Dental calculus proteins were then extracted with EDTA and separated by electrophoresis on 15% polyacrylamide gels. By immunoblotting analysis, 3 or 4 bands were observed at 11, 14.5, 22-25, 28 or 36.5 kDa and these patterns corresponded to those of calprotectin subunits. When non-immune rabbit serum was used instead of calprotectin-specific antibody as a negative control, no immunoreactivity was observed. These findings indicate that calprotectin is associated not only with antibacterial action but also with calcium binding capacity during dental calculus formation.
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Affiliation(s)
- J Kido
- Department of Periodontology and Endodontology, Tokushima University School of Dentistry, Japan
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31
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Shen M, Marie P, Farge D, Carpentier S, De Pollak C, Hott M, Chen L, Martinet B, Carpentier A. Osteopontin is associated with bioprosthetic heart valve calcification in humans. COMPTES RENDUS DE L'ACADEMIE DES SCIENCES. SERIE III, SCIENCES DE LA VIE 1997; 320:49-57. [PMID: 9099263 DOI: 10.1016/s0764-4469(99)80086-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Calcification of non-osseous tissues such as heart valves or vessels is a major concern in clinical practice. The exact mechanism is still unknown. Numerous studies have shown that mineral deposits of crystalline hydroxyapatite within these tissues were associated with increased non-collagenous protein content. More recently osteopontin was found to be associated with calcification in living tissues such as vessels and native human aortic valves. The aim of this study was to determine whether or not non-collagenous proteins can also be found in non-living tissues such as glutaraldehyde-pretreated porcine valves after implantation in humans. Thirty-eight glutaraldehyde pretreated porcine bioprostheses were studied: 16 not implanted and 22 after 11 years of implantation in the aortic and mitral valve position in humans. In areas of calcification vizualized by Von Kossa staining and microradiography, immunostaining using polyclonal antibodies against calcium-binding proteins showed osteopontin positive staining and no staining for osteocalcin, bone sialoprotein or osteonectin. In uncalcified areas and in non-implanted values, staining for osteopontin or other calcium-binding proteins was negative. Western blot analysis of macroscopically calcified and uncalcified areas showed that several proteins were adsorbed in implanted values and confirmed the presence of osteopontin in the calcified areas, while no immunolabelling was found in non-calcified areas, in uncalcified valves and in non-implanted valves. Thus the presence of osteopontin in the calcified areas of bioprosthetic heart valves implanted in human indicates that this protein is associated with bioprosthetic valvular calcification. Since these values are made of non-living connective tissue, and no cell immunostained for osteopontin was found around the calcified area, this suggests that a non-cellular mediated mechanism involving protein adsorption may play a role in bioprosthetic valvular calcification.
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Affiliation(s)
- M Shen
- Laboratoire d'étude des greffes et prothèses cardiaques, université Paris-VI-hôpital Broussais, France
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32
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Salih E, Zhou HY, Glimcher MJ. Phosphorylation of purified bovine bone sialoprotein and osteopontin by protein kinases. J Biol Chem 1996; 271:16897-905. [PMID: 8663267 DOI: 10.1074/jbc.271.28.16897] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The large number of covalently bound phosphates on the extracellular phosphoproteins osteopontin (OPN) and bone sialoprotein (BSP) have been implicated in biological functions such as mineral deposition and osteoclast binding. In the present study the state of phosphorylation of BSP and OPN was evaluated by in vitro 32P labeling using a series of protein kinases and quantification. Both the purified bovine BSP and OPN were radiolabeled by [32P]ATP and factor-independent protein kinase. Quantification of 32P radioactivity incorporated on dephosphorylated BSP and OPN provided 6.6 and 8.9 mol of phosphate incorporated/mol, respectively. Native OPN incorporated 1.07 and BSP 2.46 mol of phosphate/mol by factor-independent protein kinase. These data led to calculations that OPN and BSP, respectively, contain 7.83 and 4.14 mol of phosphate/mol in their natural state. Thrombin digests of 32P-labeled BSP showed radioactivity to be associated with fragment of approximately molecular mass values 30 kDa (N-terminal half), with no observable radioactivity associated with the 40-kDa fragment (C-terminal half). Similar experiments with 32P-labeled OPN provided two radiolabeled thrombin fragments, with molecular mass 30 kDa (N-terminal half) and 20 kDa (C-terminal half), both were radioactive. The major phosphorylation was associated with the N-terminal half containing 7.0 mol of phosphate, and 1.9 mol of phosphate were associated with the C-terminal half. Additional experiments of in vitro phosphorylation of OPN and BSP by several other known protein kinases were carried out. cAMP-dependent protein kinase showed no phosphorylation of OPN or BSP, while protein kinase C and cGMP-dependent protein kinase led to minor phosphorylation, each of the latter introduced about 1 mol of phosphate/mol of OPN and BSP molecule.
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Affiliation(s)
- E Salih
- Department of Orthopaedic Surgery, Harvard Medical School and The Children's Hospital, Boston, Massachusetts 02115, USA
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33
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Abstract
BACKGROUND The purpose of this review is to examine the usefulness of cell culture methods to model the mechanisms of bone formation on the surfaces of candidate implant materials. METHODS The central objective is to show that in vitro methods are uniquely valuable in providing an understanding of how new bone is formed on solid surfaces. It should be emphasized, at the outset, that the use of cell culture studies as cytotoxicity assays will not be addressed, nor is it implied that cell cultures can model all the complexities of the in vivo environment. Nevertheless, by comparison with in vivo data, which are by nature retrospective, it is shown that primary differentiating osteogenic cell cultures, derived from bone marrow, illustrate a sequence of extracellular matrix elaboration events that characterize the establishment of the interface between newly formed bone and solid surfaces. These solid surfaces either may be implant materials, or indeed previously formed bone matrix, which has been resorbed during normal bone remodeling events. In each case the first biologically derived matrix at these sites is a morphologically distinct collagen fibre-free extracellular matrix, which, in bone histology has been referred to for > 100 years as a cement line. RESULTS The sequence starts with secretion and adsorption to the substratum of organic components, of which the major proteins are osteopontin and bone sialoprotein. Mineralization of this matrix occurs by the seeding of nanocrystalline calcium phosphate, which precedes the appearance of morphologically identifiable collagen fibres. This is clearly contrary to the dogma that collagen is necessary for mineralization of bone, but is in agreement with specific cases of other, particularly dental, calcified connective tissues. Although collagen is synthesized by the differentiating osteogenic cells that elaborate the cement line interface, it is not adsorbed to the underlying solid surface. Following the elaboration of the cement line matrix, collagen fibre assembly occurs and is then mineralized to produce morphologically identifiable bone matrix. CONCLUSION Key elements of this sequence of events can be seen at the interface of implants retrieved from in vivo experiments, which indicates that these in vitro methods not only mimic known in vivo phenomena, but also provide a mechanistic understanding of bone elaboration at implant surfaces. However, distinction is drawn between the events of new bone formation at implant surfaces and other bone/implant morphologies, which are unrelated to de novo bone formation at the implant surface. Finally, this new information emerging from bone marrow cell culture studies demands a re-examination of the concepts of bone-bonding and nonbonding implant materials.
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Affiliation(s)
- J E Davies
- Centre for Biomaterials, University of Toronto, Ontario, Canada
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34
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Bautista DS, Saad Z, Chambers AF, Tonkin KS, O'Malley FP, Singhal H, Tokmakejian S, Bramwell V, Harris JF. Quantification of osteopontin in human plasma with an ELISA: basal levels in pre- and postmenopausal women. Clin Biochem 1996; 29:231-9. [PMID: 8740509 DOI: 10.1016/0009-9120(96)84728-a] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVES To develop an immunoassay for osteopontin (OPN), a secreted phosphoglycoprotein that is implicated in a number of human diseases, and establish basal plasma OPN levels in healthy women. DESIGN AND METHODS An antigen-capture ELISA was developed to quantity OPN in plasma using a combination of mouse monoclonal and rabbit polyclonal antibodies. Basal OPN levels were determined in blood plasma of 21 pre- and 14 postmenopausal women obtained at 7-day intervals over a 4-week period. RESULTS A group of 35 healthy women had a median OPN level of 31 micrograms/L (range = 14-64 micrograms/L). Comparison between pre- and postmenopausal women showed that their 4-week average OPN levels did not differ significantly (p > 0.16, Mann-Whitney test), and that levels in each premenopausal individual remained constant during the menstrual cycle, unaffected by cyclical levels of leuteinizing hormone and progesterone. CONCLUSION Systematic quantification of plasma OPN can now be done by ELISA, which was used to establish basal plasma OPN levels in a group of healthy women. Levels in pre- and postmenopausal women appeared relatively stable over a 4-week period.
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35
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Abstract
Bone sialoprotein (BSP) is a major protein of the mineralized bone extracellular matrix that has been implicated in the nucleation of hydroxyapatite crystals. Our previous studies have demonstrated that BSP mRNA is expressed by differentiated osteoblasts, odontoblasts, and cementoblasts involved in de novo mineralized tissue formation in a tissue-specific and developmentally regulated manner. To determine the basis of the selective expression of the BSP gene, we have generated four transgenic mouse lines in which 2.7 kb of the rat BSP promoter ligated to a luciferase reporter gene has been stably integrated into the mouse genome. Assays of luciferase activities in 5-day-old animals has revealed consistently high levels in bone tissues with negligible activities in various other organs including kidney, liver, stomach, intestine, and spleen. In some animals, variable expression was observed in brain and skin. Temporal analyses revealed the highest luciferase expression in neonatal bones, with expression decreasing markedly with subsequent growth and development, as observed previously for the endogenous gene in rats. Immunohistochemical analysis of luciferase activity and in situ hybridization of luciferase mRNA in bone tissues show that differentiated osteoblasts express the highest levels of luciferase, consistent with the induction of endogenous gene expression. These studies demonstrate that the regulation of the BSP gene during osteoblastic differentiation, together with its tissue-specific, developmentally regulated expression, is primarily mediated within the 2.7 kb region of the promoter.
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Affiliation(s)
- J Chen
- Department of Pediatric Dentistry, The University of Texas Health Science Center, San Antonio, USA
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36
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Cheng SL, Zhang SF, Avioli LV. Expression of bone matrix proteins during dexamethasone-induced mineralization of human bone marrow stromal cells. J Cell Biochem 1996; 61:182-93. [PMID: 9173083 DOI: 10.1002/(sici)1097-4644(19960501)61:2<182::aid-jcb3>3.0.co;2-q] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glucocorticoids have been shown to induce the differentiation of bone marrow stromal osteoprogenitor cells into osteoblasts and the mineralization of the matrix. Since the expression of bone matrix proteins is closely related to the differentiation status of osteoblasts and because matrix proteins may play important roles in the mineralization process, we investigated the effects of dexamethasone (Dex) on the expression of bone matrix proteins in cultured normal human bone marrow stromal cells (HBMSC). Treatment of HBMSC with Dex for 23 days resulted in a significant increase in alkaline phosphatase activity with maximum values attained on day 20 at which time the cell matrix was mineralized. Northern blot analysis revealed an increase in the steady-state mRNA level of alkaline phosphatase over 4 weeks of Dex exposure period. The observed increase in the alkaline phosphatase mRNA was effective at a Dex concentration as low as 10(-10) M with maximum values achieved at 10(-8)M. In contrast, Dex decreased the steady-state mRNA levels of both bone sialoprotein (BSP) and osteopontin (OPN) over a 4 week observation period when compared to the corresponding control values. The relative BSP and OPN mRNA levels among the Dex treated cultures, however, showed a steady increase after more than 1 week exposure. The expression of osteocalcin mRNA which was decreased after 1 day Dex exposure was undetectable 4 days later. Neither control nor Dex-treated HBMSC secreted osteocalcin into the conditioned media in the absence of 1 ,25(OH)(2)D(3) during a 25-day observation period. The accumulated data indicate that Dex has profound and varied effects on the expression of matrix proteins produced by human bone marrow stromal cells. With the induced increment in alkaline phosphatase correlating with the mineralization effects of Dex, the observed concomitant decrease in osteopontin and bone sialoprotein mRNA levels and the associated decline of osteocalcin are consistent with the hypothesis that the regulation of the expression of these highly negatively charged proteins is essential in order to maximize the Dex-induced mineralization process conditioned by normal human bone marrow stromal osteoprogenitor cells.
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Affiliation(s)
- S L Cheng
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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37
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Abstract
Expression of the osteopontin (OPN) gene in the oviduct of the laying hen was studied. It was detected only in the egg shell gland (ESG), where massive calcification occurs. No OPN gene expression was detected in any other part of the oviduct, such as the magnum and isthmus. The OPN gene was expressed in a circadian fashion during the daily egg cycle only during the period of egg shell calcification. No OPN gene expression was detected in the ESG of a pre-laying hen before the onset of reproduction, or after forced removal of the egg close to its entrance into the ESG. OPN was found to be synthesized by the epithelial cells of the ESG lining the lumen. Upon synthesis, OPN is immediately secreted out of cells and accumulates in the egg shell. These findings demonstrate for the first time temporal and spatial association of OPN with egg shell calcification. OPN, which was found to be part of the organic matrix of the egg shell, may play an important role in egg shell calcification.
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Affiliation(s)
- M Pines
- Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
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38
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Sørensen ES, Højrup P, Petersen TE. Posttranslational modifications of bovine osteopontin: identification of twenty-eight phosphorylation and three O-glycosylation sites. Protein Sci 1995; 4:2040-9. [PMID: 8535240 PMCID: PMC2142990 DOI: 10.1002/pro.5560041009] [Citation(s) in RCA: 184] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Osteopontin (OPN) is a multiphosphorylated glycoprotein found in bone and other normal and malignant tissues, as well as in the physiological fluids urine and milk. The present study demonstrates that bovine milk osteopontin is phosphorylated at 27 serine residues and 1 threonine residue. Phosphoamino acids were identified by a combination of amino acid analysis, sequence analysis of S-ethylcysteine-derivatized phosphopeptides, and mass spectrometric analysis. Twenty-five phosphoserines and one phosphothreonine were located in Ser/Thr-X-Glu/Ser(P)/Asp motifs, and two phosphoserines were found in the sequence Ser-X-X-Glu/Ser(P). These sequence motifs are identical with the recognition sequences of mammary gland casein kinase and casein kinase II, respectively. Examination of the phosphorylation pattern revealed that the phosphorylations were clustered in groups of approximately three spanned by unphosphorylated regions of 11-32 amino acids. This pattern is probably of importance in the multiple functions of OPN involving interaction with Ca2+ and inorganic calcium salts. Furthermore, three O-glycosylated threonines (Thr 115, Thr 124, and Thr 129) have been identified in a threonine- and proline-rich region of the protein. Three putative N-glycosylation sites (Asn 63, Asn 85, and Asn 193) are present in bovine osteopontin, but sequence and mass spectrometric analysis showed that none of these asparagines were glycosylated in bovine mammary gland osteopontin. Alignment analysis showed that the majority of the phosphorylation sites in bovine osteopontin as well as all three O-glycosylation sites were conserved in other mammalian sequences. This conservation of serines, even in otherwise less well-conserved regions of the protein, indicates that the phosphorylation of osteopontin at specific sites is essential for the function of the protein.
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Affiliation(s)
- E S Sørensen
- Protein Chemistry Laboratory, University of Aarhus, Denmark
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39
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Kido J, Kasahara C, Ohishi K, Nishikawa S, Ishida H, Yamashita K, Kitamura S, Kohri K, Nagata T. Identification of osteopontin in human dental calculus matrix. Arch Oral Biol 1995; 40:967-72. [PMID: 8526807 DOI: 10.1016/0003-9969(95)00056-u] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Osteopontin is a prominent non-collagenous component of bone matrix, although it is expressed in several other tissues. Recently, osteopontin was reported to be involved in urinary stone formation and atherosclerotic lesions of the aorta, suggesting that it may be a key protein associated with these types of pathological mineralization. In this study, whether or not human dental calculus contains osteopontin was investigated by immunoblotting and immunohistochemical analyses. After extraction of calculus proteins with EDTA and separation of the proteins by electrophoresis, immunoblotting analysis revealed the presence of osteopontin. Two forms of osteopontin appeared at 61 and 68 kDa on 10% polyacrylamide gel and the proteins were digested with thrombin, a highly specific protease. Moreover, immunohistochemical analysis revealed that osteopontin was localized in dental calculus adherent to tooth roots. These findings indicate that osteopontin is, in fact, present in human dental calculus and may be involved in calculus formation as the stone matrix.
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Affiliation(s)
- J Kido
- Department of Periodontology and Endodontology, Tokushima University School of Dentistry, Japan
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40
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Saavedra RA, Kimbro SK, Stern DN, Schnuer J, Ashkar S, Glimcher MJ, Ljubetic CI. Gene expression and phosphorylation of mouse osteopontin. Ann N Y Acad Sci 1995; 760:35-43. [PMID: 7540379 DOI: 10.1111/j.1749-6632.1995.tb44618.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Osteopontin is expressed in many different cell types and has been proposed to play several functions. Distinct forms of the protein have been detected. Various tissues and cell lines from mouse, however, exhibit two classes of transcripts with different 5'-untranslated ends but with an identical coding region (exons II through VII). These transcripts do not arise from the alternative splicing of coding exons. These results suggest that posttranslational modifications of osteopontin, such as phosphorylation, are a major mechanism to generate different forms of the protein. Mouse osteopontin was expressed in E. coli and used as a model to study its phosphorylation.
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Affiliation(s)
- R A Saavedra
- Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts 02115, USA
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41
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Sodek J, Chen J, Nagata T, Kasugai S, Todescan R, Li IW, Kim RH. Regulation of osteopontin expression in osteoblasts. Ann N Y Acad Sci 1995; 760:223-41. [PMID: 7785896 DOI: 10.1111/j.1749-6632.1995.tb44633.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Osteopontin (OPN) is a prominent bone matrix protein that is synthesized by osteoblastic cells. To elucidate the function of OPN in bone we studied the regulated expression of the rat OPN protein during bone formation in vivo and in vitro. OPN mRNA is expressed by preosteoblastic cells early in bone formation, but the highest expression is observed in mature osteoblasts at sites of bone remodelling. A low-phosphorylated, 55-kDa form of OPN is produced by the preosteoblastic cells, whereas osteoblasts produce a highly phosphorylated, 44-kDa protein; the two forms of OPN corresponding to pp69 and pp62 in transformed rat cells. The synthesis of the 55-kDa OPN correlates with the formation of a 'cement' matrix that is synthesized prior to bone deposition, whereas the 44-kDa OPN synthesized by osteoblasts associates rapidly with hydroxyapatite, possibly regulating crystal growth, and may also provide a substratum for osteoclast attachment. Expression of OPN mRNA is upregulated by growth and differentiation factors (PDGF, EGF, TGF-beta and BMP-7/OP-1) and by mechanical stress, which promote bone formation, as well as by osteotropic hormones (retinoic acid and vitamin D3), which can promote bone resorption and remodelling. However, OPN mRNA is down-regulated by bisphosphonates, which abrogate bone resorption. Regulation of OPN expression is, therefore, consistent with a multiplicity of functions for OPN that involve specific structural motifs in both the synthesis and resorption of bone.
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Affiliation(s)
- J Sodek
- Medical Research Council Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Ontario, Canada
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42
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Senger DR, Brown LF, Perruzzi CA, Papadopoulos-Sergiou A, Van de Water L. Osteopontin at the tumor/host interface. Functional regulation by thrombin-cleavage and consequences for cell adhesion. Ann N Y Acad Sci 1995; 760:83-100. [PMID: 7540380 DOI: 10.1111/j.1749-6632.1995.tb44622.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- D R Senger
- Department of Pathology, Beth Israel Hospital, Boston, Massachusetts 02215, USA
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43
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Sørensen ES, Petersen TE. Phosphorylation, glycosylation, and transglutaminase sites in bovine osteopontin. Ann N Y Acad Sci 1995; 760:363-6. [PMID: 7785918 DOI: 10.1111/j.1749-6632.1995.tb44658.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- E S Sørensen
- Protein Chemistry Laboratory, University of Aarhus, Denmark
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44
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Affiliation(s)
- W T Butler
- Department of Basic Sciences, University of Texas-Houston Health Science Center 77030, USA
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45
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Yang R, Gotoh Y, Moore MA, Rafidi K, Gerstenfeld LC. Characterization of an avian bone sialoprotein (BSP) cDNA: comparisons to mammalian BSP and identification of conserved structural domains. J Bone Miner Res 1995; 10:632-40. [PMID: 7610935 DOI: 10.1002/jbmr.5650100417] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Bone sialoprotein (BSP) is one of the major noncollagenous proteins found in mineralized vertebrate tissue. It is an acidic glycoprotein containing a high sialic acid content and is phosphorylated on several of its Ser and Thr residues. While it has been extensively characterized from various mammalian species, little is known about its sequence or expression in lower vertebrates. The cloning and characterization of several cDNAs encoding the chicken bone sialoprotein are reported here. A partial cDNA clone encoding the carboxyl terminus of the protein was initially isolated from a lambda GT11 expression library using a polyclonal antibody gains BSP purified from chicken bone matrix. Subsequently, several additional clones were obtained by further screening and by reverse transcription polymerase chain reaction (RT-PCR). Three overlapping clones encompassing about 1 kb, which included the complete coding sequence for BSP, were analyzed. The deduced amino acid sequence revealed that chicken BSP contains 276 amino acid residues. Although the overall identity between chicken and mammalian BSP is only approximately 39%, the diversity in amino acid sequence occurs mostly between the major functional domains of this molecule. These domains include: (1) three acidic poly-Glu regions; (2) two tyrosine-rich domains, which may be sites for protein sulfation; (3) several casein kinase II phosphorylation sites; (4) an Asn glycosylation site; and (5) an RGD cell-binding motif. Of interest in the chicken BSP is the identification of two additional RGD motifs within the avian sequence, unlike the mammalian forms of BSP which has only one.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R Yang
- Department of Orthopaedic Surgery, Harvard Medical School, Children's Hospital, Boston, Massachusetts, USA
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46
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Nagata T, Kaho K, Nishikawa S, Shinohara H, Wakano Y, Ishida H. Effect of prostaglandin E2 on mineralization of bone nodules formed by fetal rat calvarial cells. Calcif Tissue Int 1994; 55:451-7. [PMID: 7895184 DOI: 10.1007/bf00298559] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effects of PGE2 on mineralized bone nodule formation were studied in fetal rat calvarial (RC) cells in vitro. Continuous exposure of RC cells to 3 x 10(-8) M PGE2 induced a twofold increase in mineralized bone nodule formation and a 1.5-fold increase in alkaline phosphatase (ALPase) activity without affecting RC cell growth. These stimulatory effects were evoked by concentrations of 3 x 10(-9)-3 x 10(-6) M PGE2 and the maximal effect was observed with 3 x 10(-8) M PGE2. The in vitro effects of PGE2 were evident when RC cells were exposed to it on days 8-14 and 8-21, which correspond to the post-confluent culture stage, but no effects were observed when the cells were exposed on days 1-7, the growth stage. The ALPase activity was also higher (1.2-1.4-fold) when 3 x 10(-8) M PGE2 was added during the post-confluent stage. In order to determine the effect of PGE2 during the mineralization phase of bone nodules in the presence of a large population of osteoprogenitor cells, RC cells were exposed to dexamethasone for 7 days before PGE2 was added during the post-confluent stage. A significantly higher percentage of nodules mineralized were observed with 3 x 10(-8)-3 x 10(-9) M PGE2 (1.6- and 1.4-fold, respectively), than in control cultures. Analysis of the mineral-related proteins by EDTA extraction of bone nodules followed by electrophoresis and Stains-All staining revealed an increased total amount of osteopontin extracted from the mineralized matrix after PGE2 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T Nagata
- Department of Periodontology and Endodontology, Tokushima University School of Dentistry, Japan
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47
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Ohishi K, Ishida H, Nagata T, Yamauchi N, Tsurumi C, Nishikawa S, Wakano Y. Thyroid hormone suppresses the differentiation of osteoprogenitor cells to osteoblasts, but enhances functional activities of mature osteoblasts in cultured rat calvaria cells. J Cell Physiol 1994; 161:544-52. [PMID: 7962135 DOI: 10.1002/jcp.1041610318] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of thyroid hormone on osteoblastic differentiation and activity were studied in fetal rat calvaria (RC) cells cultured for up to 30 days in medium supplemented with thyroid hormone-depleted serum. In this condition, the cells proliferated and differentiated to form mineralized bone nodules (BN) and expressed osteoblastic markers such as alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). The continuous presence of triiodothyronine (T3) at 10(-9)-10(-8) M in the medium inhibited the osteoblastic differentiation: 34% decrease in ALP activity on day 12 and 60% decrease in BN formation on day 15 at 10(-8) M. T3 at these doses had no effect on the DNA content of RC cells at confluence (day 6). Short-term (48-h) exposure of T3 at 10(-9) M or higher decreased ALP activity when RC cells were differentiating (days 7-11). However, when BN formation by the cells had already reached a plateau (day 28), the activity was increased by treatment with T3 at 10(-7)-10(-6) M. OCN production was increased dose dependently by this treatment with T3 (2.1-fold and 1.3-fold of control at 10(-8) M on days 11 and 28, respectively). Similar increases were observed in the levels of OCN mRNA. In addition, increases in phosphorylated OPN in the medium (day 11) and mineralized matrix (day 28) were observed (1.5-fold at 10(-8)-10(-6) M), while OPN synthesis and the level of its mRNA were depressed by T3 (60-70% of control at 10(-8) M). These results suggest that T3 regulates osteoblastic differentiation and activity depending on the state of cell differentiation: T3 suppresses the differentiation of osteoprogenitor cells to osteoblasts, but enhances the functional activity of mature osteoblasts.
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Affiliation(s)
- K Ohishi
- Department of Periodontology and Endodontology, Tokushima University School of Dentistry, Japan
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48
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Nagata T, Yokota M, Ohishi K, Nishikawa S, Shinohara H, Wakano Y, Ishida H. 1 alpha,25-dihydroxyvitamin D3 stimulation of osteopontin expression in rat clonal dental pulp cells. Arch Oral Biol 1994; 39:775-82. [PMID: 7802613 DOI: 10.1016/0003-9969(94)90007-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Osteopontin (OPN) is a major phosphorylated non-collagenous protein isolated from bone. Rat clonal dental-pulp cell lines RPC-C2A and RDP4-1 produce and secrete OPN as a principal phosphoprotein. 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] is a potent calcitropic hormone which regulates calcified tissue metabolism including the synthesis of extracellular matrix proteins. The effects of 1,25(OH)2D3 on the expression of OPN mRNA and the synthesis of OPN protein by pulp cells in vitro were investigated. In RPC-C2A cells, 1,25(OH)2D3 markedly stimulated synthesis of both [32PO4]- and [35S]-methionine-labelled OPN. Phosphorylated OPN synthesis increased dose-dependently and showed a maximum level at 48 h after addition of 10(-11)-10(-7) M 1,25(OH)2D3. Similar stimulation was also observed in RDP4-1 cells. Northern hybridization analysis revealed that 1,25(OH)2D3 greatly increased the level of OPN mRNA in both pulp cell lines. Examination of the time course of the effects of 1,25(OH)2D3 on the level of OPN mRNA in RPC-C2A cells by dot-blot analysis showed that stimulation was detectable at 24 h and reached a maximum at 48 h after exposure to 10(-7)M 1,25(OH)2D3. These findings indicate that 1,25(OH)2D3 stimulates the production of dental-pulp OPN by a mechanism that involves de novo synthesis and transcriptional control.
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Affiliation(s)
- T Nagata
- Department of Periodontology and Endodontology, Tokushima University School of Dentistry, Japan
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Yamaguchi M, Hashizume M. Effect of beta-alanyl-L-histidinato zinc on protein components in osteoblastic MC3T3-El cells: increase in osteocalcin, insulin-like growth factor-I and transforming growth factor-beta. Mol Cell Biochem 1994; 136:163-9. [PMID: 7845370 DOI: 10.1007/bf00926077] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effect of beta-alanyl-L-histidinato zinc (AHZ) on protein components in osteoblastic MC3T3-E1 cells was investigated. Cells were cultured for 3 days at 37 degrees C in CO2 incubator in plastic dishes containing alpha-modified minimum essential medium supplemented with 10% fetal bovine serum. After the cultures, the medium was exchanged for that containing 0.1% bovine serum albumin plus various concentrations of AHZ or other reagents, and the cells were cultured further 3 or 6 days. The homgenate of cells was analyzed with SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The presence of AHZ (10(-7) to 10(-5) M) caused an appreciable increase of many protein components in cells. Especially, the 67 killo-dalton (kDa) and 44 kDa proteins which are the major components from control cells were clearly increased by the presence of AHZ. Furthermore, the concentrations of osteocalcin, insulin-like growth factor-I and transforming growth factor-beta in the culture medium secreted from osteoblastic cells were markedly increased by the presence of AHZ (10(-6) and 10(-5) M). The effect of AHZ was a greater than that of zinc sulfate (10(-6) and 10(-5) M). The present findings suggest that AHZ can increase many proteins which are involved in the stimulation of bone formation and cell proliferation in osteoblastic cells.
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Affiliation(s)
- M Yamaguchi
- Laboratory of Metabolism and Endocrinology, Graduate School of Nutritional Sciences, University of Shizuoka, Japan
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50
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Senger DR, Perruzzi CA, Papadopoulos-Sergiou A, Van de Water L. Adhesive properties of osteopontin: regulation by a naturally occurring thrombin-cleavage in close proximity to the GRGDS cell-binding domain. Mol Biol Cell 1994; 5:565-74. [PMID: 7522656 PMCID: PMC301068 DOI: 10.1091/mbc.5.5.565] [Citation(s) in RCA: 165] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Osteopontin (OPN) is a secreted adhesive glycoprotein with a functional glycine-arginine-glycine-aspartate-serine (GRGDS) cell-binding domain. An interesting feature of OPN structure is the presence of a thrombin-cleavage site in close proximity to the GRGDS region. Cleavage of OPN by thrombin is likely to be of physiological importance, because cleavage of blood plasma OPN occurs naturally after activation of the blood coagulation pathway. To investigate functional consequences of OPN cleavage by thrombin, cell attachment and spreading assays were performed with uncleaved and cleaved forms of OPN. For all cell lines examined, thrombin-cleaved OPN promoted markedly greater cell attachment and spreading than uncleaved OPN. Cell attachment and spreading on thrombin-cleaved OPN was inhibited both by the soluble GRGDS peptides and an OPN-specific antibody raised to the GRGDS domain of OPN, thus implicating the GRGDS region in mediating the increased cell attachment and spreading observed on thrombin-cleaved OPN. Because the GRGDS sequence in OPN is only six residues from the thrombin-cleavage site, the data suggest that possibility that thrombin cleavage allows greater accessibility of the GRGDS domain to cell surface receptors. To investigate receptors that recognize uncleaved and thrombin-cleaved OPN, affinity chromatography was performed on placental extracts; the cell surface integrin alpha v beta 3 bound to columns constructed either with native or thrombin-cleaved OPN and was selectively eluted from each with soluble GRGDS peptide and EDTA. Moreover, adhesion assays performed in the presence of alpha v beta 3 blocking monoclonal antibody LM609 identified alpha v beta 3 as a major functional receptor for thrombin-cleaved OPN. Several lines of evidence suggest that cleavage of OPN by thrombin occurs in vivo, such as in tumors and at sites of tissue injury, and adhesion assay data presented here indicate that such cleavage is important in the regulation of OPN function.
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Affiliation(s)
- D R Senger
- Department of Pathology, Beth Israel Hospital, Boston, Massachusetts
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