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Zhao L, Leung LL, Morser J. Methods to Investigate Thrombin Cleavage of Osteopontin (OPN). Methods Mol Biol 2024; 2747:95-117. [PMID: 38038935 DOI: 10.1007/978-1-0716-3589-6_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Osteopontin (OPN) is a matricellular protein containing binding sites for a variety of ligands including an RGD sequence for binding to αvβ3 integrins. OPN is a conserved substrate for thrombin, the effector protease of the coagulation cascade. Thrombin cleaves OPN at a single site revealing new functionalities such as a previously cryptic α4β1 and α9β1 integrin-binding site. That integrin-binding site is abolished upon treatment with a basic carboxypeptidase. The thrombin cleavage of OPN has been demonstrated to play a role in regulating tumor growth.This report describes methods for production of full-length OPN as well as the enzymatically cleaved OPN fragments resulting from thrombin and carboxypeptidase treatments. Quantification procedures for the various OPN proteins are described as well as functional assays on mouse melanoma and myeloid cell lines.
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Affiliation(s)
- Lei Zhao
- Division of Hematology, Stanford University School of Medicine, Stanford, CA, USA
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA
| | - Lawrence L Leung
- Division of Hematology, Stanford University School of Medicine, Stanford, CA, USA.
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA.
| | - John Morser
- Division of Hematology, Stanford University School of Medicine, Stanford, CA, USA.
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA.
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2
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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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3
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Sørensen ES, Christensen B. Milk Osteopontin and Human Health. Nutrients 2023; 15:nu15112423. [PMID: 37299387 DOI: 10.3390/nu15112423] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 06/12/2023] Open
Abstract
Osteopontin (OPN) is a multifunctional protein found in all vertebrates. OPN is expressed in many different cell types, and is consequently found in most tissues and physiological secretions. OPN is involved in a multitude of biological processes, such as activation and regulation of the immune system; biomineralization; tissue-transformative processes, including growth and development of the gut and brain; interaction with bacteria; and many more. OPN is found in the highest concentrations in milk, where it is believed to initiate and regulate developmental, immunological and physiological processes in infants who consume milk. Processes for the isolation of bovine OPN for use in infant formula have been developed, and in recent years, many studies have investigated the effects of the intake of milk OPN. The purpose of this article is to review and compare existing knowledge about the structure and function of milk OPN, with a particular focus on the effects of milk OPN on human health and disease.
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Affiliation(s)
- Esben S Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Brian Christensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
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Zhang Y, Mo Y, Zhang Y, Yuan J, Zhang Q. MMP-3-mediated cleavage of OPN is involved in copper oxide nanoparticle-induced activation of fibroblasts. Part Fibre Toxicol 2023; 20:22. [PMID: 37217992 PMCID: PMC10201731 DOI: 10.1186/s12989-023-00532-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/08/2023] [Indexed: 05/24/2023] Open
Abstract
BACKGROUND Copper oxide nanoparticles (Nano-CuO) are one of the most produced and used nanomaterials. Previous studies have shown that exposure to Nano-CuO caused acute lung injury, inflammation, and fibrosis. However, the mechanisms underlying Nano-CuO-induced lung fibrosis are still unclear. Here, we hypothesized that exposure of human lung epithelial cells and macrophages to Nano-CuO would upregulate MMP-3, which cleaved osteopontin (OPN), resulting in fibroblast activation and lung fibrosis. METHODS A triple co-culture model was established to explore the mechanisms underlying Nano-CuO-induced fibroblast activation. Cytotoxicity of Nano-CuO on BEAS-2B, U937* macrophages, and MRC-5 fibroblasts were determined by alamarBlue and MTS assays. The expression or activity of MMP-3, OPN, and fibrosis-associated proteins was determined by Western blot or zymography assay. Migration of MRC-5 fibroblasts was evaluated by wound healing assay. MMP-3 siRNA and an RGD-containing peptide, GRGDSP, were used to explore the role of MMP-3 and cleaved OPN in fibroblast activation. RESULTS Exposure to non-cytotoxic doses of Nano-CuO (0.5 and 1 µg/mL) caused increased expression and activity of MMP-3 in the conditioned media of BEAS-2B and U937* cells, but not MRC-5 fibroblasts. Nano-CuO exposure also caused increased production of cleaved OPN fragments, which was abolished by MMP-3 siRNA transfection. Conditioned media from Nano-CuO-exposed BEAS-2B, U937*, or the co-culture of BEAS-2B and U937* caused activation of unexposed MRC-5 fibroblasts. However, direct exposure of MRC-5 fibroblasts to Nano-CuO did not induce their activation. In a triple co-culture system, exposure of BEAS-2B and U937* cells to Nano-CuO caused activation of unexposed MRC-5 fibroblasts, while transfection of MMP-3 siRNA in BEAS-2B and U937* cells significantly inhibited the activation and migration of MRC-5 fibroblasts. In addition, pretreatment with GRGDSP peptide inhibited Nano-CuO-induced activation and migration of MRC-5 fibroblasts in the triple co-culture system. CONCLUSIONS Our results demonstrated that Nano-CuO exposure caused increased production of MMP-3 from lung epithelial BEAS-2B cells and U937* macrophages, which cleaved OPN, resulting in the activation of lung fibroblasts MRC-5. These results suggest that MMP-3-cleaved OPN may play a key role in Nano-CuO-induced activation of lung fibroblasts. More investigations are needed to confirm whether these effects are due to the nanoparticles themselves and/or Cu ions.
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Affiliation(s)
- Yuanbao Zhang
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, 485 E. Gray Street, Louisville, KY 40202 USA
| | - Yiqun Mo
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, 485 E. Gray Street, Louisville, KY 40202 USA
| | - Yue Zhang
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611 USA
| | - Jiali Yuan
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, 485 E. Gray Street, Louisville, KY 40202 USA
| | - Qunwei Zhang
- Department of Epidemiology and Population Health, School of Public Health and Information Sciences, University of Louisville, 485 E. Gray Street, Louisville, KY 40202 USA
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Christensen B, Nielsen NR, Sørensen MR, Jacobsen LN, Ostenfeld MS, Sørensen ES. Naturally Occurring N-Terminal Fragments of Bovine Milk Osteopontin Are Transported across Models of the Intestinal Barrier. Biomedicines 2023; 11:biomedicines11030893. [PMID: 36979872 PMCID: PMC10045268 DOI: 10.3390/biomedicines11030893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/07/2023] [Accepted: 03/12/2023] [Indexed: 03/18/2023] Open
Abstract
Osteopontin (OPN) is a bioactive integrin-binding protein found in high concentrations in milk, where it is present both as a full-length protein and as several N-terminally derived fragments. OPN resists gastric digestion, and via interaction with receptors in the gut or by crossing the intestinal barrier into circulation, ingested milk OPN may influence physiological processes. The aim of this study was to investigate OPN interaction with intestinal cells and its transport across models of the intestinal barrier. Immunodetection of OPN incubated with Caco-2 cells at 4 °C and 37 °C showed that OPN binds to the intestinal cells, but it is not internalised. Transepithelial transport was studied using mono- and co-cultures of Caco-2 cells and mucus-producing HT29-MTX cells in transwell membranes. OPN was shown to cross the barrier models in a time-, temperature-, and energy-dependent process inhibited by wortmannin, indicating that the transport takes place via the transcytosis pathway. Analyses of the naturally occurring milk mixture of full-length and N-terminal fragments showed that the N-terminal fragments of OPN bound intestinal cells most effectively and that the fragments were transported across the intestinal membrane models. This suggests that proteolytic processing of OPN increases its biological activity after ingestion.
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Affiliation(s)
- Brian Christensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; (B.C.)
| | - Nanna R. Nielsen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; (B.C.)
| | - Marie R. Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; (B.C.)
| | - Lotte N. Jacobsen
- Arla Foods Ingredients Group P/S, DK-8260 Viby J, Denmark; (L.N.J.); (M.S.O.)
| | - Marie S. Ostenfeld
- Arla Foods Ingredients Group P/S, DK-8260 Viby J, Denmark; (L.N.J.); (M.S.O.)
| | - Esben S. Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; (B.C.)
- Correspondence:
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Turck D, Castenmiller J, De Henauw S, Hirsch‐Ernst KI, Kearney J, Maciuk A, Mangelsdorf I, McArdle HJ, Naska A, Pelaez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Cubadda F, Frenzel T, Heinonen M, Maradona MP, Marchelli R, Neuhäuser‐Berthold M, Poulsen M, Schlatter JR, van Loveren H, Gelbmann W, Knutsen HK. Safety of bovine milk osteopontin as a Novel food pursuant to Regulation (EU) 2015/2283. EFSA J 2022; 20:e07137. [PMID: 35572202 PMCID: PMC9074041 DOI: 10.2903/j.efsa.2022.7137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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Slovacek H, Khanna R, Poredos P, Jezovnik M, Hoppensteadt D, Fareed J, Hopkinson W. Interrelationship of Osteopontin, MMP-9 and ADAMTS4 in Patients With Osteoarthritis Undergoing Total Joint Arthroplasty. Clin Appl Thromb Hemost 2021; 26:1076029620964864. [PMID: 33350314 PMCID: PMC7758646 DOI: 10.1177/1076029620964864] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Osteoarthritis (OA) is a degenerative joint disease characterized by loss of articular cartilage, inflammation and pain, which sometimes necessitates total joint arthroplasty (TJA). Profiling biomarkers of cartilage degradation and inflammation is a promising area of research to understand the pathogenesis of OA. This study aims to report the post-operative fluctuations of 3 biomarkers of OA, osteopontin (OPN), matrix metalloproteinase-9 (MMP-9), and ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs 4), in patients undergoing TJA to further define the interaction among these biomarkers and delineate their role in OA pathogenesis. OPN is an extracellular matrix (ECM) glycoprotein with increased activity in OA and joint damage and is upregulated by either inflammation or cleavage by MMPs and thrombin. MMP-9 is known to cleave OPN and is upregulated by inflammatory markers, such as IL-1, IL-6 and CRP. ADAMTS4 is an enzyme that degrades aggrecan, a major component of cartilage. These biomarkers were measured in deidentified blood samples collected on the day of surgery, 1 day post-operatively, and day 5-7 post-operatively. MMP-9 and OPN levels were significantly elevated at all times, and ADAMTS4 was significantly decreased at baseline versus controls. OPN and ADAMTS4 inversely fluctuated post-operatively, indicating an interrelation between these 2 biomarkers. This study suggests that the upregulation of MMP-9 and therefore OPN then results in the downregulation of ADAMTS4. The relationship between OPN and thrombin also highlights the importance of monitoring for thrombotic complications. These biomarkers, along with thrombin-mediated cleavage products, may be helpful in the prognostic management of OA patients.
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Affiliation(s)
- Hannah Slovacek
- Department of Pathology and Laboratory Medicine, 25815Loyola University Medical Center, Maywood, IL, USA
| | - Rajan Khanna
- Department of Pathology and Laboratory Medicine, 25815Loyola University Medical Center, Maywood, IL, USA
| | - Pavel Poredos
- Medical Clinic Division of Vascular Medicine, 37663Ljubljana University Medical Center, Ljubljana, Slovenia
| | - Mateja Jezovnik
- Department of Advanced Cardiopulmonary Therapies and Transplantation, 12340University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Debra Hoppensteadt
- Department of Pathology and Laboratory Medicine, Cardiovascular Research Institute, 2456Loyola University Chicago, Health Sciences Division, Maywood, IL, USA
| | - Jawed Fareed
- Cardiovascular Research Institute, 2456Loyola University Chicago, Health Sciences Division, Maywood, IL, USA
| | - William Hopkinson
- Health Sciences Division, Orthopaedic Surgery and Rehabilitation Department, 2456Loyola University Chicago, Maywood, IL, USA
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Jia Q, Wang Y, Zhu J, Yu H, Tong X. A literature review on lactopontin and its roles in early life. Transl Pediatr 2021; 10:1924-1931. [PMID: 34430441 PMCID: PMC8349962 DOI: 10.21037/tp-21-293] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 07/14/2021] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE Our study aims to review the functions and possible mechanisms of lactopontin (LPN) in early life. BACKGROUND Human milk proteins provide a variety of protection and health benefits in early life. One of these multifunctional proteins is LPN, which is osteopontin (OPN) derived from milk. METHODS Information used to write this paper was collected from Uniprot, PubMed, and Google Scholar, including in vitro, in vivo, and clinical studies. CONCLUSIONS LPN is a highly phosphorylated, O-glycosylated acidic protein and a unique type of OPN, as it presents at the highest concentration and a higher degree of posttranslational modifications (PTMs) in human milk than other tissues and excretions. LPN is present in milk and the intestinal tracts of infants after consumption as a mixture of intact protein and peptides, which can bind diverse integrin and receptors in the target cell and drive downstream signaling pathways. LPN is found to play important roles in developing the immune, intestinal and nervous systems in early life. Moreover, LPN has also shown to support preterm infants' health when they are especially vulnerable after delivery via animal studies. Additionally, LPN can form protein complex with another milk bioactive protein, lactoferrin (LF), to withstand proteolysis and perform more efficient biological activity. Therefore, LPN showed great potential for early life while more clinical trials and evidence are still emergying.
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Affiliation(s)
- Qiong Jia
- Department of Pediatrics, Peking University Third Hospital, Beijing, China
| | - Yiran Wang
- Department of Nutritional and Functional Assessment, Beijing Institute of Nutritional Resources, Beijing, China
| | - Jing Zhu
- Department of Nutritional and Functional Assessment, Beijing Institute of Nutritional Resources, Beijing, China
| | - Huanling Yu
- Department of Nutrition and Food Hygiene, School of Public Health, Capital Medical University, Beijing, China
| | - Xiaomei Tong
- Department of Pediatrics, Peking University Third Hospital, Beijing, China
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Factors influencing milk osteopontin concentration based on measurements from Danish Holstein cows. J DAIRY RES 2021; 88:89-94. [PMID: 33622420 DOI: 10.1017/s0022029921000054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Our objective was to determine the content of the bioactive protein osteopontin (OPN) in bovine milk and identify factors influencing its concentration. OPN is expressed in many tissues and body fluids, with by far the highest concentrations in milk. OPN plays a role in immunological and developmental processes and it has been associated with several milk production traits and lactation persistency in cows. In the present study, we report the development of an enzyme linked immunosorbent assay (ELISA) for measurement of OPN in bovine milk. The method was used to determine the concentration of OPN in milk from 661 individual Danish Holstein cows. The median OPN level was determined to 21.9 mg/l with a pronounced level of individual variation ranging from 0.4 mg/l to 67.8 mg/l. Breeding for increased OPN in cow's milk is of significant interest, however, the heritability of OPN in milk was found to be relatively low, with an estimated value of 0.19 in the current dataset. The variation explained by the herd was also found to be low suggesting that OPN levels are not affected by farm management or feeding. Interestingly, the concentration of OPN was found to increase with days in milk and to decrease with parity.
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10
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Bu T, Zheng J, Liu L, Li S, Wu J. Milk proteins and their derived peptides on bone health: Biological functions, mechanisms, and prospects. Compr Rev Food Sci Food Saf 2021; 20:2234-2262. [PMID: 33522110 DOI: 10.1111/1541-4337.12707] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Bone is a dynamic organ under constant metabolism (or remodeling), where a delicate balance between bone resorption and bone formation is maintained. Disruption of this coordinated bone remodeling results in bone diseases, such as osteoporosis, the most common bone disorder characterized by decreased bone mineral density and microarchitectural deterioration. Epidemiological and clinical evidence support that consumption of dairy products is beneficial for bone health; this benefit is often attributed to the presence of calcium, the physiological contributions of milk proteins on bone metabolism, however, are underestimated. Emerging evidence highlighted that not only milk proteins (including individual milk proteins) but also their derived peptides positively regulate bone remodeling and attenuate bone loss, via the regulation of cellular markers and signaling of osteoblasts and osteoclasts. This article aims to review current knowledge about the roles of milk proteins, with an emphasis on individual milk proteins, bioactive peptides derived from milk proteins, and effect of milk processing in particular fermentation, on bone metabolism, to highlight the potential uses of milk proteins in the prevention and treatment of osteoporosis, and, to discuss the knowledge gap and to recommend future research directions.
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Affiliation(s)
- Tingting Bu
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China.,ZJU-UA Joint Lab for Molecular Nutrition and Bioactive Peptides, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China
| | - Jiexia Zheng
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China.,ZJU-UA Joint Lab for Molecular Nutrition and Bioactive Peptides, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China
| | - Ling Liu
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China.,ZJU-UA Joint Lab for Molecular Nutrition and Bioactive Peptides, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China
| | - Shanshan Li
- College of Animal Sciences, Zhejiang University, Hangzhou, P. R. China
| | - Jianping Wu
- ZJU-UA Joint Lab for Molecular Nutrition and Bioactive Peptides, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, P. R. China.,Department of Agricultural, Food and Nutritional Science, 4-10 Ag/For Building, University of Alberta, Edmonton, Alberta, Canada
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11
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Bailey S, Sroga GE, Hoac B, Katsamenis OL, Wang Z, Bouropoulos N, McKee MD, Sørensen ES, Thurner PJ, Vashishth D. The role of extracellular matrix phosphorylation on energy dissipation in bone. eLife 2020; 9:58184. [PMID: 33295868 PMCID: PMC7746230 DOI: 10.7554/elife.58184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 12/07/2020] [Indexed: 01/22/2023] Open
Abstract
Protein phosphorylation, critical for cellular regulatory mechanisms, is implicated in various diseases. However, it remains unknown whether heterogeneity in phosphorylation of key structural proteins alters tissue integrity and organ function. Here, osteopontin phosphorylation level declined in hypo- and hyper- phosphatemia mouse models exhibiting skeletal deformities. Phosphorylation increased cohesion between osteopontin polymers, and adhesion of osteopontin to hydroxyapatite, enhancing energy dissipation. Fracture toughness, a measure of bone’s mechanical competence, increased with ex-vivo phosphorylation of wildtype mouse bones and declined with ex-vivo dephosphorylation. In osteopontin-deficient mice, global matrix phosphorylation level was not associated with toughness. Our findings suggest that phosphorylated osteopontin promotes fracture toughness in a dose-dependent manner through increased interfacial bond formation. In the absence of osteopontin, phosphorylation increases electrostatic repulsion, and likely protein alignment and interfilament distance leading to decreased fracture resistance. These mechanisms may be of importance in other connective tissues, and the key to unraveling cell–matrix interactions in diseases.
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Affiliation(s)
- Stacyann Bailey
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
| | - Grazyna E Sroga
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
| | - Betty Hoac
- Faculty of Dentistry, McGill University, Montreal, Canada
| | - Orestis L Katsamenis
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, United Kingdom
| | - Zehai Wang
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, United States
| | | | - Marc D McKee
- Faculty of Dentistry, McGill University, Montreal, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, Canada
| | - Esben S Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - Deepak Vashishth
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
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12
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Structural Biology of Calcium Phosphate Nanoclusters Sequestered by Phosphoproteins. CRYSTALS 2020. [DOI: 10.3390/cryst10090755] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Biofluids that contain stable calcium phosphate nanoclusters sequestered by phosphopeptides make it possible for soft and hard tissues to co-exist in the same organism with relative ease. The stability diagram of a solution of nanocluster complexes shows how the minimum concentration of phosphopeptide needed for stability increases with pH. In the stable region, amorphous calcium phosphate cannot precipitate. Nevertheless, if the solution is brought into contact with hydroxyapatite, the crystalline phase will grow at the expense of the nanocluster complexes. The physico-chemical principles governing the formation, composition, size, structure, and stability of the complexes are described. Examples are given of complexes formed by casein, osteopontin, and recombinant phosphopeptides. Application of these principles and properties to blood serum, milk, urine, and resting saliva is described to show that under physiological conditions they are in the stable region of their stability diagram and so cannot cause soft tissue calcification. Stimulated saliva, however, is in the metastable region, consistent with its role in tooth remineralization. Destabilization of biofluids, with consequential ill-effects, can occur when there is a failure of homeostasis, such as an increase in pH without a balancing increase in the concentration of sequestering phosphopeptides.
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13
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Christensen B, Karlsen NJ, Jørgensen SDS, Jacobsen LN, Ostenfeld MS, Petersen SV, Müllertz A, Sørensen ES. Milk osteopontin retains integrin-binding activity after in vitro gastrointestinal transit. J Dairy Sci 2019; 103:42-51. [PMID: 31733850 DOI: 10.3168/jds.2019-17212] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 09/30/2019] [Indexed: 11/19/2022]
Abstract
Osteopontin (OPN) is a multifunctional protein highly expressed in milk, where it is hypothesized to be involved in immunological signaling via the conserved Arg-Gly-Asp (RGD) integrin-binding sequence. Intervention studies have indicated beneficial effects of orally administered OPN in animal and human infants, but the mechanisms underlying these effects are not well described. To induce physiological effects, OPN must resist gastrointestinal transit in a bioactive form. In this study, we subjected bovine milk OPN to in vitro gastrointestinal transit, and characterized the generated fragments using monoclonal antibody and mass spectrometric analyses. We found that the fragment Trp27-Phe151 containing the integrin-binding RGD sequence resisted in vitro gastric digestion. This resistance was dependent on glycosylation of threonine residues near the integrin-binding sequence in both human and bovine milk OPN. Furthermore, the fragment Trp27-Phe151 retained the ability to interact with integrins in an RGD-dependent process. These results suggest a mechanism for how ingested milk OPN can induce physiological effects via integrin signaling in the intestine.
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Affiliation(s)
- B Christensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; iFood, Aarhus University Center for Innovative Food Research, DK-8000 Aarhus, Denmark
| | - N J Karlsen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - S D S Jørgensen
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - L N Jacobsen
- Arla Foods Ingredients Group P/S, DK-8260 Viby J, Denmark
| | - M S Ostenfeld
- Arla Foods Ingredients Group P/S, DK-8260 Viby J, Denmark
| | - S V Petersen
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus, Denmark
| | - A Müllertz
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - E S Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark; iFood, Aarhus University Center for Innovative Food Research, DK-8000 Aarhus, Denmark.
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A Reversed-Phase HPLC Method for Determination of Osteopontin in Infant Formula. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9183711] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Osteopontin (OPN) is a multifunctional whey protein which has recently received much attention for possibly applications in fortifying infant milk formula (IMF) with its bioactivity. However, to date, there is no established high-performance liquid chromatography (HPLC) method to quantify this protein in milk or IMF. In this study, a rapid, simple, isocratic and reliable reversed-phase HPLC method was developed and validated to quantify the OPN in IMF. A C18 column (4.6 × 150 mm × 5 micron) was employed with 20% of 0.1% trifluoroacetic acid (TFA) and 80% of 60% acetonitrile in 0.1% TFA for 10 min detected at 214 nm. The flow rate was 0.3 mL/min with an injection volume of 10 µL. The column temperature was 40 °C, and the peak appeared after 4 min. The validation was based on the system suitability, linearity (r2 = 0.999), limit of detection (LOD) (0.14 mg/L), limit of quantitation (LOQ) (0.41 mg/L), precision (% relative standard deviation (RSD) < 0.2), recovery (% RSD < 3) and robustness. The results confirm that the method developed is suitable for OPN determination in IMF.
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Osteopontin Levels in Human Milk Vary Across Countries and Within Lactation Period: Data From a Multicenter Study. J Pediatr Gastroenterol Nutr 2018; 67:250-256. [PMID: 29668569 DOI: 10.1097/mpg.0000000000002004] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVES Osteopontin (OPN) is a multifunctional protein expressed in many cell types, tissues and body fluids with the highest concentrations found in milk; significantly higher in human than in bovine milk. Intervention studies have indicated beneficial effects of supplementing infant formula with bovine OPN. In this multicenter study, we determined the OPN content in human milk samples from 629 Chinese, Danish, Japanese and Korean mothers. METHODS At each study site, milk samples were collected and analyzed for OPN and protein concentration using ELISA and infrared spectroscopy, respectively. RESULTS A total of 829 milk samples from 629 women were included. When delivering the first sample, mean maternal age was 31.4 years (SD 4.0), and median infant age was 13.4 weeks (interquartile range 4.6-17.9). The median OPN concentration varied across sites; from 99.7 mg/L in Danish, 185.0 mg/L in Japanese, 216.2 mg/L in Korean to 266.2 mg/L in Chinese mothers (P < 0.001), corresponding to 1.3%, 2.4%, 1.8% and 2.7% of the total protein content (OPN/protein%) (P < 0.05), respectively. Based on 75 Chinese and 33 Japanese mothers delivering more than 1 sample, multilevel (mixed model) linear regression analysis showed a decrease in OPN concentration with infant age (β = (-11.3), 95% confidence interval (CI) = (-13.9) to (-8.8) and β = (-2.1), 95% CI = (-3.2) to (-0.9), respectively). CONCLUSIONS In this large multicenter study, we observed statistically significant differences in the OPN concentration and the OPN/protein% in human milk samples between countries. Based on mothers delivering more than 1 sample, a significant decrease within the lactation period was observed.
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Effect of Phosphorylation on a Human-like Osteopontin Peptide. Biophys J 2017; 112:1586-1596. [PMID: 28445750 PMCID: PMC5406370 DOI: 10.1016/j.bpj.2017.03.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/25/2017] [Accepted: 03/06/2017] [Indexed: 12/22/2022] Open
Abstract
The last decade established that the dynamic properties of the phosphoproteome are central to function and its modulation. The temporal dimension of phosphorylation effects remains nonetheless poorly understood, particularly for intrinsically disordered proteins. Osteopontin, selected for this study due to its key role in biomineralization, is expressed in many species and tissues to play a range of distinct roles. A notable property of highly phosphorylated isoforms of osteopontin is their ability to sequester nanoclusters of calcium phosphate to form a core-shell structure, in a fluid that is supersaturated but stable. In Biology, this process enables soft and hard tissues to coexist in the same organism with relative ease. Here, we extend our understanding of the effect of phosphorylation on a disordered protein, the recombinant human-like osteopontin rOPN. The solution structures of the phosphorylated and unphosphorylated rOPN were investigated by small-angle x-ray scattering and no significant changes were detected on the radius of gyration or maximum interatomic distance. The picosecond-to-nanosecond dynamics of the hydrated powders of the two rOPN forms were further compared by elastic and quasi-elastic incoherent neutron scattering. Phosphorylation was found to block some nanosecond side-chain motions while increasing the flexibility of other side chains on the faster timescale. Phosphorylation can thus selectively change the dynamic behavior of even a highly disordered protein such as osteopontin. Through such an effect on rOPN, phosphorylation can direct allosteric mechanisms, interactions with substrates, cofactors and, in this case, amorphous or crystalline biominerals.
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17
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Ameziane-Le Hir S, Bourgeois D, Basset C, Hagège A, Vidaud C. Reactivity of U-associated osteopontin with lactoferrin: a one-to-many complex. Metallomics 2017; 9:865-875. [DOI: 10.1039/c7mt00087a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A highly-simplified scenario of LF/U-fOPN interaction. The U content of the U-fOPN complexes refers to the CE-ICP/MS experiments.
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Affiliation(s)
| | | | - Christian Basset
- CEA
- DRF
- Biosciences and Biotechnologies Institute (BIAM)
- Bagnols-sur-Cèze
- France
| | - Agnès Hagège
- Univ Lyon
- CNRS
- Université Claude Bernard Lyon 1
- Ens de Lyon
- Institut des Sciences Analytiques
| | - Claude Vidaud
- CEA
- DRF
- Biosciences and Biotechnologies Institute (BIAM)
- Bagnols-sur-Cèze
- France
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19
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Jürets A, Le Bras M, Staffler G, Stein G, Leitner L, Neuhofer A, Tardelli M, Turkof E, Zeyda M, Stulnig TM. Inhibition of Cellular Adhesion by Immunological Targeting of Osteopontin Neoepitopes Generated through Matrix Metalloproteinase and Thrombin Cleavage. PLoS One 2016; 11:e0148333. [PMID: 26840958 PMCID: PMC4740464 DOI: 10.1371/journal.pone.0148333] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 01/15/2016] [Indexed: 01/10/2023] Open
Abstract
Osteopontin (OPN), a secreted protein involved in inflammatory processes and cancer, induces cell adhesion, migration, and activation of inflammatory pathways in various cell types. Cells bind OPN via integrins at a canonical RGD region in the full length form as well as to a contiguous cryptic site that some have shown is unmasked upon thrombin or matrix metalloproteinase cleavage. Thus, the adhesive capacity of osteopontin is enhanced by proteolytic cleavage that may occur in inflammatory conditions such as obesity, atherosclerosis, rheumatoid arthritis, tumor growth and metastasis. Our aim was to inhibit cellular adhesion to recombinant truncated proteins that correspond to the N-terminal cleavage products of thrombin- or matrix metalloproteinase-cleaved OPN in vitro. We specifically targeted the cryptic integrin binding site with monoclonal antibodies and antisera induced by peptide immunization of mice. HEK 293 cells adhered markedly stronger to truncated OPN proteins than to full length OPN. Without affecting cell binding to the full length form, the raised monoclonal antibodies specifically impeded cellular adhesion to the OPN fragments. Moreover, we show that the peptides used for immunization were able to induce antisera, which impeded adhesion either to all OPN forms, including the full-length form, or selectively to the corresponding truncated recombinant proteins. In conclusion, we developed immunological tools to selectively target functional properties of protease-cleaved OPN forms, which could find applications in treatment and prevention of various inflammatory diseases and cancers.
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Affiliation(s)
- Alexander Jürets
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | | | | | - Gesine Stein
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Lukas Leitner
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Angelika Neuhofer
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Matteo Tardelli
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Edvin Turkof
- Department of Plastic and Reconstructive Surgery, Medical University of Vienna, Vienna, Austria
| | - Maximilian Zeyda
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Thomas M. Stulnig
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
- * E-mail:
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20
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Lenton S, Nylander T, Holt C, Sawyer L, Härtlein M, Müller H, Teixeira SCM. Structural studies of hydrated samples of amorphous calcium phosphate and phosphoprotein nanoclusters. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 45:405-12. [PMID: 26780236 DOI: 10.1007/s00249-015-1109-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 11/25/2015] [Accepted: 12/17/2015] [Indexed: 11/28/2022]
Abstract
There are abundant examples of nanoclusters and inorganic microcrystals in biology. Their study under physiologically relevant conditions remains challenging due to their heterogeneity, instability, and the requirements of sample preparation. Advantages of using neutron diffraction and contrast matching to characterize biomaterials are highlighted in this article. We have applied these and complementary techniques to search for nanocrystals within clusters of calcium phosphate sequestered by bovine phosphopeptides, derived from osteopontin or casein. The neutron diffraction patterns show broad features that could be consistent with hexagonal hydroxyapatite crystallites smaller than 18.9 Å. Such nanocrystallites are, however, undetected by the complementary X-ray and FTIR data, collected on the same samples. The absence of a distinct diffraction pattern from the nanoclusters supports the generally accepted amorphous calcium phosphate structure of the mineral core.
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Affiliation(s)
- Samuel Lenton
- EPSAM, Keele University, Staffordshire, ST5 5BG, UK.,Institut Laue-Langevin, 71 Avenue des Martyrs, 38042, Grenoble Cedex 9, France.,School of Physics and Astronomy, Astbury Center for Structural Molecular Biology, University of Leeds, LS2 9JT, Leeds, UK
| | - Tommy Nylander
- Division of Physical Chemistry, Department of Chemistry, Lund University, 124, Lund, S221 00, Sweden
| | - Carl Holt
- Institute of Molecular, Cell, and Systems Biology, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Lindsay Sawyer
- Structural Biochemistry Group, University of Edinburgh, Roger Land Building, The King's Buildings, Mayfield Road, EH9 3JR, Edinburgh, UK
| | - Michael Härtlein
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042, Grenoble Cedex 9, France
| | - Harrald Müller
- European Synchrotron Radiation Facility, CS 40220, 38043, Grenoble, France
| | - Susana C M Teixeira
- EPSAM, Keele University, Staffordshire, ST5 5BG, UK. .,Institut Laue-Langevin, 71 Avenue des Martyrs, 38042, Grenoble Cedex 9, France.
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21
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Lenton S, Seydel T, Nylander T, Holt C, Härtlein M, Teixeira S, Zaccai G. Dynamic footprint of sequestration in the molecular fluctuations of osteopontin. J R Soc Interface 2015; 12:0506. [PMID: 26354827 PMCID: PMC4614460 DOI: 10.1098/rsif.2015.0506] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 08/19/2015] [Indexed: 11/12/2022] Open
Abstract
The sequestration of calcium phosphate by unfolded proteins is fundamental to the stabilization of biofluids supersaturated with respect to hydroxyapatite, such as milk, blood or urine. The unfolded state of osteopontin (OPN) is thought to be a prerequisite for this activity, which leads to the formation of core-shell calcium phosphate nanoclusters. We report on the structures and dynamics of a native OPN peptide from bovine milk, studied by neutron spectroscopy and small-angle X-ray and neutron scattering. The effects of sequestration are quantified on the nanosecond- ångström resolution by elastic incoherent neutron scattering. The molecular fluctuations of the free phosphopeptide are in agreement with a highly flexible protein. An increased resilience to diffusive motions of OPN is corroborated by molecular fluctuations similar to those observed for globular proteins, yet retaining conformational flexibilities. The results bring insight into the modulation of the activity of OPN and phosphopeptides with a role in the control of biomineralization. The quantification of such effects provides an important handle for the future design of new peptides based on the dynamics-activity relationship.
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Affiliation(s)
- S Lenton
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France Environment, Physical Sciences and Applied Mathematics Research Institute, Keele University, Staffordshire ST5 5BG, UK
| | - T Seydel
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France
| | - T Nylander
- Division of Physical Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - C Holt
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow G12 8QQ, UK
| | - M Härtlein
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France
| | - S Teixeira
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France Environment, Physical Sciences and Applied Mathematics Research Institute, Keele University, Staffordshire ST5 5BG, UK
| | - G Zaccai
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France C.N.R.S., Institut de Biologie Structurale, F-38044 Grenoble, France
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22
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Leitner L, Schuch K, Jürets A, Itariu BK, Keck M, Grablowitz V, Aszmann OC, Prager G, Staffler G, Zeyda M, Stulnig TM. Immunological blockade of adipocyte inflammation caused by increased matrix metalloproteinase-cleaved osteopontin in obesity. Obesity (Silver Spring) 2015; 23:779-85. [PMID: 25776538 DOI: 10.1002/oby.21024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 12/16/2014] [Indexed: 01/22/2023]
Abstract
OBJECTIVE Osteopontin (OPN) is upregulated in adipose tissue (AT) in obesity and contributes to subclinical inflammation, adipocyte dysfunction, and insulin resistance. OPN effects can be increased by cleavage by matrix metalloproteinases (MMP). This study aimed at investigating the presence of OPN cleavage products in human AT in obesity and their impact on adipocyte function and immunological blockade of these effects. METHODS AT of severely obese and control donors was investigated for OPN and MMP expression and the presence of OPN cleavage fragments. Primary adipocytes were isolated from human donors for in vitro investigation of cleaved OPN effects. RESULTS OPN and MMP-9 expression was highly correlated in AT from obese donors, and increased levels of cleaved OPN were detected in AT from obese individuals. The in vitro effect of OPN on adipocyte inflammation and insulin resistance was enhanced by protease cleavage, which could finally be blocked with a monoclonal antibody directed against the MMP cleavage site of OPN. CONCLUSIONS These findings show that MMP cleavage of OPN in AT occurs in obesity, thereby enhancing OPN's inflammatory and pro-diabetic activity on adipocytes. Specifically targeting MMP-cleaved OPN opens avenues for prevention and treatment of obesity-induced type 2 diabetes.
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Affiliation(s)
- Lukas Leitner
- Christian Doppler Laboratory for Cardio-Metabolic Immunotherapy and Clinical Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
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23
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Lindsey ML, Zouein FA, Tian Y, Padmanabhan Iyer R, de Castro Brás LE. Osteopontin is proteolytically processed by matrix metalloproteinase 9. Can J Physiol Pharmacol 2015; 93:879-86. [PMID: 26176332 DOI: 10.1139/cjpp-2015-0019] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Osteopontin is robustly upregulated following myocardial infarction (MI), which suggests that it has an important role in post-MI remodeling of the left ventricle (LV). Osteopontin deletion results in increased LV dilation and worsened cardiac function. Thus, osteopontin exerts protective effects post-MI, but the mechanisms have yet to be defined. Matrix metalloproteinases (MMPs) regulate LV remodeling post-MI, and osteopontin is a known substrate for MMP-2, -3, -7, and -9, although the cleavage sites have not been mapped. Osteopontin-derived peptides can exert distinct biological functions that may depend on their cleavage sites. We mapped the MMP-9 cleavage sites via LC-MS/MS analysis using label-free and N-terminal labeling methods, and compared them with those of MMP-2, -3, and -7. Each MMP yielded a unique cleavage profile with few overlapping cleavage sites. Using synthetic peptides, we validated 3 sites for MMP-9 cleavage at amino acid positions 151-152, 193-194, and 195-196. Four peptides were synthesized based on the upstream- and downstream-generated fragments and were tested for biological activity in isolated cardiac fibroblasts. Two peptides increased cardiac fibroblast migration rates post-wounding (p < 0.05 compared with the negative control). Our study highlights the importance of osteopontin processing, and confirms that different cleavage sites generate osteopontin peptides with distinct biological functions.
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Affiliation(s)
- Merry L Lindsey
- a San Antonio Cardiovascular Proteomics Center.,b Mississippi Center for Heart Research, Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA.,c Research Service, G.V. (Sonny) Montgomery Veterans Affairs Medical Center, Jackson, Mississippi, USA
| | - Fouad A Zouein
- a San Antonio Cardiovascular Proteomics Center.,b Mississippi Center for Heart Research, Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - Yuan Tian
- a San Antonio Cardiovascular Proteomics Center.,b Mississippi Center for Heart Research, Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - Rugmani Padmanabhan Iyer
- a San Antonio Cardiovascular Proteomics Center.,b Mississippi Center for Heart Research, Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA
| | - Lisandra E de Castro Brás
- a San Antonio Cardiovascular Proteomics Center.,d East Carolina University, Department of Physiology, Greenville, North Carolina, USA
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A review of the biology of calcium phosphate sequestration with special reference to milk. ACTA ACUST UNITED AC 2014; 95:3-14. [PMID: 25632319 PMCID: PMC4302223 DOI: 10.1007/s13594-014-0177-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 06/05/2014] [Accepted: 06/17/2014] [Indexed: 11/04/2022]
Abstract
In milk, a stable fluid is formed in which sequestered nanoclusters of calcium phosphate are substructures in casein micelles. As a result, calcium and phosphate concentrations in milk can be far in excess of their solubility. Variations of calcium, phosphate and casein concentrations in milks, both within and among species, are mainly due to the formation of the nanocluster complexes. Caseins evolved from tooth and bone proteins well before the evolution of lactation. It has therefore been suggested that the role of caseins in milk is an adaptation of an antecedent function in the control of some aspect of biomineralisation. There is new evidence that nanocluster-type complexes are also present in blood serum and, by implication, in many other closely related biofluids. Because such fluids are stable but nevertheless supersaturated with respect to the bone and tooth mineral hydroxyapatite, they allow soft and mineralised tissues to co-exist in the same organism with relative ease. An appreciable concentration of nanocluster complexes exists in fresh saliva. Such saliva may stabilise tooth mineral and help to repair demineralised lesions. In the extracellular matrix of bone, nanocluster complexes may be involved in directing the amorphous calcium phosphate to intrafibrillar spaces in collagen where they can mature into oriented apatite crystals. Thus, evidence is accumulating that calcium phosphate sequestration by phosphopeptides to form equilibrium complexes, first observed in milk, is more generally important in the control of physiological calcification.
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