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Kanaan R, Yaghi C, Saade Riachy C, Schlosser A, Hamade A, Holmskov U, Medlej‐Hashim M, Sørensen GL, Jounblat R. Serum
MFAP4
, a novel potential biomarker for liver cirrhosis screening, correlates with transient elastography in
NAFLD
patients. JGH Open 2023; 7:197-203. [PMID: 36968563 PMCID: PMC10037036 DOI: 10.1002/jgh3.12873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 12/20/2022] [Accepted: 01/16/2023] [Indexed: 02/25/2023]
Abstract
Background and Aim Non-alcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in different countries. Liver fibrosis is considered as the most appropriate predictor of NAFLD-associated outcome. Microfibrillar-associated protein 4 (MFAP4) is a glycoprotein located in the extracellular matrix. Circulatory MFAP4 has been suggested as a noninvasive biomarker for the assessment of hepatitis C virus and alcoholic liver disease associated liver fibrosis. In this study, we aimed to investigate the association between serum MFAP4 and liver fibrosis severity in NAFLD patients. Methods A case-control study was conducted in which NAFLD patients (n = 25) and healthy participants (n = 12) were recruited. Liver fibrosis/cirrhosis was assessed by transient elastography (TE) and biochemical parameters were collected. Serum MFAP4 was measured by sandwich ELISA based on two monoclonal anti-MFAP4 antibodies and calibrated with a standard of recombinant MFAP4. Results Serum MFAP4 levels increased with fibrosis severity and were highly upregulated in patients with cirrhosis (F4 fibrosis stage). In addition, serum MFAP4 levels positively correlated with TE measurement and showed significant association with the severely advanced fibrotic stage in NAFLD patients, in multiple linear regression analysis following adjustment for age, gender, and body mass index. Conclusion This study suggests the use of MFAP4 as a potential diagnostic noninvasive biomarker for cirrhosis screening in NAFLD patients.
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Affiliation(s)
- Reine Kanaan
- Department of Cancer and Inflammation Research Institute of Molecular Medicine, University of Southern Denmark Odense Denmark
- Laboratory of Cellular and Molecular Physiopathologies (CAMP), Department of Life and Earth Sciences, Faculty of Sciences Lebanese University Beirut Lebanon
| | - Cesar Yaghi
- Faculty of Medicine Saint‐Joseph University Beirut Lebanon
- Hepato‐Gastroenterology Department Hôtel‐ Dieu de France University Hospital Beirut Lebanon
| | | | - Anders Schlosser
- Department of Cancer and Inflammation Research Institute of Molecular Medicine, University of Southern Denmark Odense Denmark
| | - Aline Hamade
- Laboratoire d'Innovation Thérapeutique (LIT), Departments of Life and Earth Sciences – Chemistry and Biochemistry, Faculty of Sciences Lebanese University Beirut Lebanon
| | - Uffe Holmskov
- Department of Cancer and Inflammation Research Institute of Molecular Medicine, University of Southern Denmark Odense Denmark
| | - Myrna Medlej‐Hashim
- Laboratory of Cellular and Molecular Physiopathologies (CAMP), Department of Life and Earth Sciences, Faculty of Sciences Lebanese University Beirut Lebanon
| | - Grith Lykke Sørensen
- Department of Cancer and Inflammation Research Institute of Molecular Medicine, University of Southern Denmark Odense Denmark
| | - Rania Jounblat
- Laboratory of Cellular and Molecular Physiopathologies (CAMP), Department of Life and Earth Sciences, Faculty of Sciences Lebanese University Beirut Lebanon
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Johansson SL, Wulf-Johansson H, Schlosser A, Titlestad IL, Miller B, Tal-Singer R, Holmskov U, Vestbo J, Sørensen GL. Plasma microfibrillar-associated protein 4 is not prognostic of emphysema progression but is associated with cardiovascular disease history and mortality in COPD patients. ERJ Open Res 2019; 5:00021-2019. [PMID: 31024964 PMCID: PMC6469069 DOI: 10.1183/23120541.00021-2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 02/24/2019] [Indexed: 11/10/2022] Open
Abstract
Chronic obstructive pulmonary disease (COPD) is characterised by chronic airflow limitation and inflammation of the airways and lung parenchyma. COPD is associated with many comorbidities, especially cardiovascular disease (CVD), which share similar risk factors with COPD [1]. Circulating MFAP4 is a relevant biomarker to identify COPD patients at risk of death and cardiovascular comorbidity after smoking cessationhttp://ow.ly/6vnL30o8t1g
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Affiliation(s)
- Sofie Lock Johansson
- Dept of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Helle Wulf-Johansson
- Dept of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Anders Schlosser
- Dept of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Ingrid L Titlestad
- Dept of Respiratory Medicine, Odense University Hospital, Odense, Denmark
| | | | | | - Uffe Holmskov
- Dept of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Jørgen Vestbo
- Dept of Respiratory Medicine, Odense University Hospital, Odense, Denmark.,Division of Infection, Immunity and Respiratory Medicine, The University of Manchester, Manchester Academic Health Science Centre, and Manchester NHS Foundation Trust, Manchester, UK
| | - Grith Lykke Sørensen
- Dept of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
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Gudmann NS, Siebuhr AS, Christensen AF, Ejstrup L, Sørensen GL, Loft AG, Karsdal MA, Bay-Jensen AC, Munk HL, Junker P. Type I and III collagen turnover is increased in axial spondyloarthritis and psoriatic arthritis. Associations with disease activity and diagnostic capacity. Clin Exp Rheumatol 2017; 35:653-659. [PMID: 28240584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/20/2017] [Indexed: 06/06/2023]
Abstract
OBJECTIVES To investigate the turnover of type I and III collagen by neo-epitope markers in patients with axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA). METHODS Patients with PsA (n=101) or axSpA (n=110) and healthy subjects (n=120) were included. Demographic and clinical data were recorded. Markers of type I and III collagen were quantified by RIA (ICTP) or ELISA (C1M and C3M). Non-parametric statistics were applied for intergroup comparisons and correlation studies. The diagnostic potential of these marker molecules was assessed by ROC analysis. RESULTS C1M and C3M, which originate from soft connective tissues, were significantly higher in axSpA and PsA as compared with healthy control subjects. CIM and C3M correlated with ASDAS and DAS28. Overall, ICTP, which arises from bone degradation, did not differ between disease versus healthy. However, ICTP was lower in HLA-B27 positive than in HLA-B27 negative patients with axSpA. There was no association between bone and soft connective tissue collagen I markers (ICTP and C1M), while C1M and C3M were highly correlated (p<0.0001). C1M discriminated between healthy and diseased with AUCs of 0.83 for PsA and 0.79 for axSpA. C3M AUCs were 0.77 for PsA and 0.78 for axSpA. CONCLUSIONS Type I and III collagen remodelling in soft connective tissue is increased in axSpA and PsA and associates with disease activity. Bone collagen degradation is lower in HLA-B27 positive compared with HLA-B27 negative axSpA, which may represent an aspect of enhanced enthesopathic bone proliferation in HLA-B27 carriers. C1M and C3M distinguish well between healthy and diseased individuals.
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Affiliation(s)
| | | | | | - Leif Ejstrup
- Department of Rheumatology, Esbjerg Hospital, Denmark
| | | | - Anne Gitte Loft
- Department of Rheumatology, Vejle Hospital; and Department of Rheumatology, Aarhus University Hospital, Denmark
| | | | | | | | - Peter Junker
- Department of Rheumatology, Odense University Hospital, Denmark
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Gudmann NS, Munk HL, Christensen AF, Ejstrup L, Sørensen GL, Loft AG, Karsdal MA, Bay-Jensen AC, He Y, Siebuhr AS, Junker P. Chondrocyte activity is increased in psoriatic arthritis and axial spondyloarthritis. Arthritis Res Ther 2016; 18:141. [PMID: 27306080 PMCID: PMC4910260 DOI: 10.1186/s13075-016-1040-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 05/31/2016] [Indexed: 01/22/2023] Open
Abstract
Background Psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) are chronic inflammatory rheumatic diseases with complex origins. Both are characterized by altered extracellular matrix remodeling in joints and entheses that results in destructive and osteochondral proliferative lesions. There is a need for biomarkers reflecting core disease pathways for diagnosis and disease mapping. Pro-C2 reflects mature cartilage collagen type IIB formation, while C-Col10 represents turnover of type X collagen, which is exclusively expressed by hypertrophic chondrocytes. The objectives of this study were to study cartilage metabolism in axSpA and PsA by assessing Pro-C2 and C-Col10 and to evaluate their diagnostic utility against a healthy reference population. Methods Patients with PsA (n = 101) or axSpA (n = 110) were recruited consecutively from three rheumatology outpatient clinics. Demographic and clinical disease measures were recorded. Pro-C2 and C-Col10 were quantified in serum by using newly developed and specific competitive enzyme-linked immunosorbent assays based on monoclonal antibodies. One-way analysis of variance and Tukey’s multiple comparison tests were performed on log-transformed data. ROC curve analysis was carried out to evaluate their discriminative power. Results Pro-C2 levels in serum were significantly increased in both axSpA (median concentration 1.11 ng/ml, 0.67–1.64) and PsA (median concentration 1.03 ng/ml, 0.53–1.47) compared with healthy controls (median concentration 0.30 ng/ml, 0.16–0.41) (p < 0.0001). Pro-C2 did not differ according to treatment. C-Col10 was slightly but equally elevated in the PsA and axSpA groups vs. the control group, but it was significantly lower in patients with axSpA undergoing tumor necrosis factor-α inhibitor (TNFi) treatment. ROC curve analysis revealed AUCs of 0.85 (95 % CI 0.79–0.89) for axSpA and 0.81 (95 % CI 0.75–0.86) for PsA. Conclusions These findings indicate that cartilage collagen metabolism was enhanced in the axSpA and PsA groups compared with the healthy control group. The lower C-Col10 level in patients with axSpA undergoing TNFi treatment may reflect that hypertrophic chondrocytes in axSpA are targeted by TNFi. ROC curve analysis showed a diagnostic potential for Pro-C2 in axSpA and PsA.
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Affiliation(s)
- Natasja Stæhr Gudmann
- Nordic Bioscience Biomarkers and Research, Herlev Hovedgade 207, Herlev, 2730, Denmark.
| | | | | | - Leif Ejstrup
- Department of Rheumatology, Esbjerg Hospital, Esbjerg, Denmark
| | - Grith Lykke Sørensen
- Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Anne Gitte Loft
- Department of Rheumatology, Vejle Hospital, Vejle, Denmark.,Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark
| | - Morten Asser Karsdal
- Nordic Bioscience Biomarkers and Research, Herlev Hovedgade 207, Herlev, 2730, Denmark
| | | | - Yi He
- Nordic Bioscience Biomarkers and Research, Herlev Hovedgade 207, Herlev, 2730, Denmark
| | - Anne Sofie Siebuhr
- Nordic Bioscience Biomarkers and Research, Herlev Hovedgade 207, Herlev, 2730, Denmark
| | - Peter Junker
- Department of Rheumatology, Odense University Hospital, Odense, Denmark
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Sækmose SG, Schlosser A, Holst R, Johansson SL, Wulf-Johansson H, Tornøe I, Vestbo J, Kyvik KO, Barington T, Holmskov U, Sørensen GL. Enzyme-linked immunosorbent assay characterization of basal variation and heritability of systemic microfibrillar-associated protein 4. PLoS One 2013; 8:e82383. [PMID: 24324779 PMCID: PMC3853316 DOI: 10.1371/journal.pone.0082383] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 10/25/2013] [Indexed: 11/23/2022] Open
Abstract
Background Microfibrillar-associated protein 4 (MFAP4) is a systemic biomarker that is significantly elevated in samples from patients suffering from hepatic cirrhosis. The protein is generally localized to elastic fibers and other connective tissue fibers in the extracellular matrix (ECM), and variation in systemic MFAP4 (sMFAP4) has the potential to reflect diverse diseases with increased ECM turnover. Here, we aimed to validate an enzyme-linked immunosorbent assay (ELISA) for the measurement of sMFAP4 with an emphasis on the robustness of the assay. Moreover, we aimed to determine confounders influencing the basal sMFAP4 variability and the genetic contribution to the basal variation. Methods The sandwich ELISA was based on two monoclonal anti-MFAP4 antibodies and was optimized and calibrated with a standard of recombinant MFAP4. The importance of pre-analytical sample handling was evaluated regarding sample tube type, time, and temperature conditions. The mean value structure and variance structure was determined in a twin cohort including 1,417 Danish twins (age 18-67 years) by mixed-effect linear regression modeling. Results The practical working range of the sandwich ELISA was estimated to be 4-75 U/ml. The maximum intra- and inter-assay variation was estimated to be 8.7% and 6.6%, respectively. Sample handling and processing appeared to influence MFAP4 measurements only marginally. The average concentration of sMFAP4 in the serum was 18.9 ± 8.4 (SD) U/ml in the twin cohort (95% CI: 18.5-19.4, median sMFAP4 17.3 U/ml). The mean structure model was demonstrated to include waist-hip ratio, age, and cigarette smoking status in interactions with gender. A relatively low heritability of h2 = 0.24 was found after applying a model including additive genetic factors and shared and non-shared environmental factors. Conclusions The described ELISA provides robust measures of the liver fibrosis marker sMFAP4. The low heritability and the relatively limited basal variation suggest that increased sMFAP4 reflects disease-induced processes.
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Affiliation(s)
- Susanne Gjørup Sækmose
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
- Department of Clinical Immunology, Region Sjaelland, Naestved Hospital, Naestved, Denmark
- Department of Clinical Immunology, Odense University Hospital, Odense, Denmark
| | - Anders Schlosser
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - René Holst
- Danish Twin Registry and Danish Aging Research Centre, Institute of Public Health, University of Southern Denmark, Odense, Denmark
| | - Sofie Lock Johansson
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Helle Wulf-Johansson
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Ida Tornøe
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Jørgen Vestbo
- Department of Respiratory Medicine, Odense University Hospital, Odense, Denmark
- Respiratory and Allergy Research Group, Manchester Academic Health Sciences Centre, University Hospital South Manchester NHD Foundation Trust, Manchester, United Kingdom
| | - Kirsten Ohm Kyvik
- Danish Twin Registry and Danish Aging Research Centre, Institute of Public Health, University of Southern Denmark, Odense, Denmark
- Odense Patient data Explorative Network (OPEN), Odense University Hospital, Odense, Denmark
| | - Torben Barington
- Department of Clinical Immunology, Odense University Hospital, Odense, Denmark
- Odense Patient data Explorative Network (OPEN), Odense University Hospital, Odense, Denmark
| | - Uffe Holmskov
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Grith Lykke Sørensen
- Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
- * E-mail:
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Layden BT, Durai V, Newman MV, Marinelarena AM, Ahn CW, Feng G, Lin S, Zhang X, Kaufman DB, Jafari N, Sørensen GL, Lowe WL. Regulation of pancreatic islet gene expression in mouse islets by pregnancy. J Endocrinol 2010; 207:265-79. [PMID: 20847227 DOI: 10.1677/joe-10-0298] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Pancreatic β cells adapt to pregnancy-induced insulin resistance by unclear mechanisms. This study sought to identify genes involved in β cell adaptation during pregnancy. To examine changes in global RNA expression during pregnancy, murine islets were isolated at a time point of increased β cell proliferation (E13.5), and RNA levels were determined by two different assays (global gene expression array and G-protein-coupled receptor (GPCR) array). Follow-up studies confirmed the findings for select genes. Differential expression of 110 genes was identified and follow-up studies confirmed the changes in select genes at both the RNA and protein level. Surfactant protein D (SP-D) mRNA and protein levels exhibited large increases, which were confirmed in murine islets. Cytokine-induced expression of SP-D in islets was also demonstrated, suggesting a possible role as an anti-inflammatory molecule. Complementing these studies, an expression array was performed to define pregnancy-induced changes in expression of GPCRs that are known to impact islet cell function and proliferation. This assay, the results of which were confirmed using real-time reverse transcription-PCR assays, demonstrated that free fatty acid receptor 2 and cholecystokinin receptor A mRNA levels were increased at E13.5. This study has identified multiple novel targets that may be important for the adaptation of islets to pregnancy.
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Affiliation(s)
- B T Layden
- Division of Endocrinology, Metabolism and Molecular Medicine, Department of Medicine, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Tarry 15, Chicago, Illinois 60611, USA
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Olesen HV, Holmskov U, Schiøtz PO, Sørensen GL. Serum-surfactant SP-D correlates inversely to lung function in cystic fibrosis. J Cyst Fibros 2010; 9:257-62. [DOI: 10.1016/j.jcf.2010.03.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Revised: 03/22/2010] [Accepted: 03/29/2010] [Indexed: 01/07/2023]
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Christensen AF, Sørensen GL, Hørslev-Petersen K, Holmskov U, Lindegaard HM, Junker K, Hetland ML, Stengaard-Pedersen K, Jacobsen S, Lottenburger T, Ellingsen T, Andersen LS, Hansen I, Skjødt H, Pedersen JK, Lauridsen UB, Svendsen A, Tarp U, Pødenphant J, Vestergaard A, Jurik AG, Østergaard M, Junker P. Circulating surfactant protein -D is low and correlates negatively with systemic inflammation in early, untreated rheumatoid arthritis. Arthritis Res Ther 2010; 12:R39. [PMID: 20211020 PMCID: PMC2888186 DOI: 10.1186/ar2948] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 01/11/2010] [Accepted: 03/08/2010] [Indexed: 01/05/2023] Open
Abstract
INTRODUCTION Surfactant protein D (SP-D) is a collectin with immuno-regulatory functions, which may depend on oligomerization. Anti-microbial and anti-inflammatory properties have been attributed to multimeric SP-D variants, while trimeric subunits per se have been suggested to enhance inflammation. Previously, we reported low circulating SP-D in early rheumatoid arthritis (RA), and the present investigation aims to extend these data by serial SP-D serum measurements, studies on synovial fluid, SP-D size distribution and genotyping in patients with early RA. METHODS One-hundred-and-sixty disease-modifying antirheumatic drug (DMARD) naïve RA patients with disease duration less than six months were studied prospectively for four years (CIMESTRA (Ciclosporine, Methotrexate, Steroid in RA) trial) including disease activity measures (C-reactive protein, joint counts and Health Assessment Questionnaire (HAQ) score), autoantibodies, x-ray findings and SP-D. SP-D was quantified by enzyme-linked immunosorbent assay (ELISA) and molecular size distribution was assessed by gel filtration chromatography. Further, SP-D Met11Thr single nucleotide polymorphism (SNP) analysis was performed. RESULTS Serum SP-D was significantly lower in RA patients at baseline compared with healthy controls (P < 0.001). SP-D increased slightly during follow-up (P < 0.001), but was still subnormal at four years after adjustment for confounders (P < 0.001). SP-D in synovial fluid was up to 2.5-fold lower than in serum. While multimeric variants were detected in serum, SP-D in synovial fluid comprised trimeric subunits only. There were no significant associations between genotype distribution and SP-D. Baseline SP-D was inversely associated to CRP and HAQ score. A similar relationship was observed regarding temporal changes in SP-D and CRP (zero to four years). SP-D was not associated to x-ray findings. CONCLUSIONS This study confirms that circulating SP-D is persistently subnormal in early and untreated RA despite a favourable therapeutic response obtained during four years of follow-up. SP-D correlated negatively to disease activity measures, but was not correlated with x-ray progression or SP-D genotype. These observations suggest that SP-D is implicated in RA pathogenesis at the protein level. The exclusive presence of trimeric SP-D in affected joints may contribute to the maintenance of joint inflammation. TRIAL REGISTRATION (j.nr NCT00209859).
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Larsen MR, Sørensen GL, Fey SJ, Larsen PM, Roepstorff P. Phospho-proteomics: evaluation of the use of enzymatic de-phosphorylation and differential mass spectrometric peptide mass mapping for site specific phosphorylation assignment in proteins separated by gel electrophoresis. Proteomics 2001; 1:223-38. [PMID: 11680869 DOI: 10.1002/1615-9861(200102)1:2<223::aid-prot223>3.0.co;2-b] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Detection of phosphorylated proteins as well as assignment of the phosphorylated sites in such proteins is a major challenge in proteomics. In the present study we evaluate the use of enzymatic de-phosphorylation in combination with differential peptide mass mapping for identification of phosphorylated peptides in peptide mixtures derived from in-gel digested phospho-proteins. Phospho-peptides could be identified provided that improved sample preparation methods prior to mass spectrometric analysis were used. An attempt to identify the proteins visualized by [32P] autoradiography in a proteomics study and their phosphorylation sites, demonstrated that protein identification was possible whereas reliable identification of the phospho-peptides requires more protein than normally available in our proteomics studies.
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Affiliation(s)
- M R Larsen
- Department of Biochemistry and Molecular Biology, Center for Proteome Analysis, University of Southern Denmark, Denmark
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