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Abstract
α2-macroglobulins are broad-spectrum endopeptidase inhibitors, which have to date been characterised from metazoans (vertebrates and invertebrates) and Gram-negative bacteria. Their structural and biochemical properties reveal two related modes of action: the "Venus flytrap" and the "snap-trap" mechanisms. In both cases, peptidases trigger a massive conformational rearrangement of α2-macroglobulin after cutting in a highly flexible bait region, which results in their entrapment. In some homologs, a second action takes place that involves a highly reactive β-cysteinyl-γ-glutamyl thioester bond, which covalently binds cleaving peptidases and thus contributes to the further stabilization of the enzyme:inhibitor complex. Trapped peptidases are still active, but have restricted access to their substrates due to steric hindrance. In this way, the human α2-macroglobulin homolog regulates proteolysis in complex biological processes, such as nutrition, signalling, and tissue remodelling, but also defends the host organism against attacks by external toxins and other virulence factors during infection and envenomation. In parallel, it participates in several other biological functions by modifying the activity of cytokines and regulating hormones, growth factors, lipid factors and other proteins, which has a great impact on physiology. Likewise, bacterial α2-macroglobulins may participate in defence by protecting cell wall components from attacking peptidases, or in host-pathogen interactions through recognition of host peptidases and/or antimicrobial peptides. α2-macroglobulins are more widespread than initially thought and exert multifunctional roles in both eukaryotes and prokaryotes, therefore, their on-going study is essential.
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Affiliation(s)
- Irene Garcia-Ferrer
- Proteolysis Lab, Structural Biology Unit, "María de Maeztu" Unit of Excellence, Molecular Biology Institute of Barcelona (CSIC), Barcelona Science Park; c/Baldiri Reixac, 15-21, 08028, Barcelona, Spain
- Present address: EMBL Grenoble, 71 Avenue des Martyrs; 38042 CS 90181, Grenoble Cedex 9, France
| | - Aniebrys Marrero
- Proteolysis Lab, Structural Biology Unit, "María de Maeztu" Unit of Excellence, Molecular Biology Institute of Barcelona (CSIC), Barcelona Science Park; c/Baldiri Reixac, 15-21, 08028, Barcelona, Spain
- Present address: Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - F Xavier Gomis-Rüth
- Proteolysis Lab, Structural Biology Unit, "María de Maeztu" Unit of Excellence, Molecular Biology Institute of Barcelona (CSIC), Barcelona Science Park; c/Baldiri Reixac, 15-21, 08028, Barcelona, Spain
| | - Theodoros Goulas
- Proteolysis Lab, Structural Biology Unit, "María de Maeztu" Unit of Excellence, Molecular Biology Institute of Barcelona (CSIC), Barcelona Science Park; c/Baldiri Reixac, 15-21, 08028, Barcelona, Spain.
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2
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Puttini S, Panaite PA, Mermod N, Renaud S, Steck AJ, Kuntzer T. Gene expression changes in chronic inflammatory demyelinating polyneuropathy skin biopsies. J Neuroimmunol 2014; 270:61-6. [PMID: 24657030 DOI: 10.1016/j.jneuroim.2014.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/15/2014] [Accepted: 03/02/2014] [Indexed: 11/25/2022]
Abstract
Chronic-inflammatory demyelinating polyneuropathy (CIDP) is an immune-mediated disease with no known biomarkers for diagnosing the disease or assessing its prognosis. We performed transcriptional profiling microarray analysis on skin punch biopsies from 20 CIDP patients and 17 healthy controls to identify disease-associated gene expression changes. We demonstrate changes in expression of genes involved in immune and chemokine regulation, growth and repair. We also found a combination of two upregulated genes that can be proposed as a novel biomarker of the disorder.
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Affiliation(s)
- Stefania Puttini
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Institute of Biotechnology, University of Lausanne (UNIL), chemin des Alambiques, CH-1015 Lausanne, Switzerland
| | - Petrica-Adrian Panaite
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland
| | - Nicolas Mermod
- Institute of Biotechnology, University of Lausanne (UNIL), chemin des Alambiques, CH-1015 Lausanne, Switzerland
| | - Susanne Renaud
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Neurology Division, Hôpital Neuchâtelois, Maladière 45, CH-2000 Neuchâtel, Switzerland
| | - Andreas J Steck
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Department of Neurology, Basel University Hospital, Spitalstrasse 21, 4031 Basel, Switzerland
| | - Thierry Kuntzer
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
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3
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Rehman AA, Ahsan H, Khan FH. α-2-Macroglobulin: a physiological guardian. J Cell Physiol 2013; 228:1665-75. [PMID: 23086799 DOI: 10.1002/jcp.24266] [Citation(s) in RCA: 242] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 10/12/2012] [Indexed: 12/18/2022]
Abstract
Alpha macroglobulins are large glycoproteins which are present in the body fluids of both invertebrates and vertebrates. Alpha-2-macroglobulin (α2 M), a key member of alpha macroglobulin superfamily, is a high-molecular weight homotetrameric glycoprotein. α2 M has many diversified and complex functions, but it is primarily known by its ability to inhibit a broad spectrum of proteases without the direct blockage of the protease active site. α2 M is also known to be involved in the regulation, transport, and a host of other functions. For example, apart from inhibiting proteinases, it regulates binding of transferrin to its surface receptor, binds defensin and myelin basic protein, etc., binds several important cytokines, including basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), nerve growth factor (NGF), interleukin-1β (IL-1β), and interleukin-6 (IL-6), and modify their biological activity. α2 M also binds a number of hormones and regulates their activity. α2 M is said to protect the body against various infections, and hence, can be used as a biomarker for the diagnosis and prognosis of a number of diseases. However, this multipurpose antiproteinse is not "fail safe" and could be damaged by reactive species generated endogenously or exogenously, leading to various pathophysiological conditions.
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Affiliation(s)
- Ahmed A Rehman
- Faculty of Life Sciences, Department of Biochemistry, Aligarh Muslim University, Aligarh, India
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Li KC, Palotie A, Yuan S, Bronnikov D, Chen D, Wei X, Choi OW, Saarela J, Peltonen L. Finding disease candidate genes by liquid association. Genome Biol 2008; 8:R205. [PMID: 17915034 PMCID: PMC2246280 DOI: 10.1186/gb-2007-8-10-r205] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/23/2007] [Accepted: 10/04/2007] [Indexed: 01/29/2023] Open
Abstract
A novel approach to finding candidate genes by using gene-expression data has been developed and used to identify a multiple sclerosis susceptibility candidate genes. A novel approach to finding candidate genes by using gene expression data through liquid association is developed and used to identify multiple sclerosis susceptibility candidate genes.
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Affiliation(s)
- Ker-Chau Li
- Department of Statistics, UCLA, 8125 Math Sciences Bldg, Los Angeles, California 90095-1554, USA
- Institute of Statistical Science, Academia Sinica, Academia Road, Nankang, Taipei 115, Taiwan
| | - Aarno Palotie
- The Finnish Genome Center and Department of Clinical Chemistry, University of Helsinki, Haartmaninkatu, 00290 Helsinki, Finland
- The Broad Institute of Harvard and MIT, Cambridge Center, Cambridge, Massachusetts 02142, USA
- Department of Pathology and Laboratory Medicine, Gonda Researach Center, UCLA, Los Angeles, California 90095-1766, USA
- Department of Human Genetics, UCLA, 695 Charles E. Young Drive South, Los Angeles, California 90095-1766, USA
| | - Shinsheng Yuan
- Institute of Statistical Science, Academia Sinica, Academia Road, Nankang, Taipei 115, Taiwan
| | - Denis Bronnikov
- The Broad Institute of Harvard and MIT, Cambridge Center, Cambridge, Massachusetts 02142, USA
- National Public Health Institute, Helsinki, Finland, Biomedicum Helsinki, Haartmaninkatu, 00290 Helsinki, Finland
| | - Daniel Chen
- The Broad Institute of Harvard and MIT, Cambridge Center, Cambridge, Massachusetts 02142, USA
| | - Xuelian Wei
- Department of Statistics, UCLA, 8125 Math Sciences Bldg, Los Angeles, California 90095-1554, USA
| | - Oi-Wa Choi
- The Broad Institute of Harvard and MIT, Cambridge Center, Cambridge, Massachusetts 02142, USA
| | - Janna Saarela
- National Public Health Institute, Helsinki, Finland, Biomedicum Helsinki, Haartmaninkatu, 00290 Helsinki, Finland
| | - Leena Peltonen
- National Public Health Institute, Helsinki, Finland, Biomedicum Helsinki, Haartmaninkatu, 00290 Helsinki, Finland
- Department of Medical Genetics, University of Helsinki, Biomedicum Helsinki, Haartmaninkatu, 00290 Helsinki, Finland
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Cederfur C, Salomonsson E, Nilsson J, Halim A, Oberg CT, Larson G, Nilsson UJ, Leffler H. Different affinity of galectins for human serum glycoproteins: galectin-3 binds many protease inhibitors and acute phase proteins. Glycobiology 2008; 18:384-94. [PMID: 18263896 DOI: 10.1093/glycob/cwn015] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Here we report the first survey of galectins binding to glycoproteins of human serum. Serum was subjected to affinity chromatography using immobilized galectins, and the bound glycoproteins were analyzed by electrophoresis, Western blotting, and mass spectrometry. Galectins-3, -8, and -9 bound a much broader range of ligands in serum than previously known, galectin-1 bound less, and galectins-2, -4, and -7 bound only traces or no serum ligands. Galectin-3 bound most major glycoproteins, including alpha-2-macroglobulin and acute phase proteins such as haptoglobin. It bound only a selected minor fraction of transferrin, and bound none or little of IgG. Galectins-8 and -9 bound a similar range of glycoproteins as galectin-3, but in lower amounts, and galectin-8 had a relative preference for IgA. Galectin-1 bound mainly a fraction of alpha-2-macroglobulin and only traces of other glycoproteins. The binding of galectin-3 to serum glycoproteins requires affinity for LacNAc, since a mutant (R186S), which has lost this affinity, did not bind any serum glycoproteins. The average affinity of galectin-3 for serum glycoproteins was estimated to correspond to K(d) approximately 1-5 muM by modeling of the affinity chromatography and a fluorescence anisotropy assay. Since galectins are expressed on endothelial cells and other cells exposed to serum components, this report gives new insight into function of galectins and the role of their different fine specificity giving differential binding to the serum glycoproteins.
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Affiliation(s)
- Cecilia Cederfur
- Department of Laboratory Medicine, Section MIG (Microbiology, Immunology, Glycobiology), Lund University, 223-62 Lund, Sweden.
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Jensen PEH, Humle Jørgensen S, Datta P, Sørensen PS. Significantly increased fractions of transformed to total α2-macroglobulin concentrations in plasma from patients with multiple sclerosis. Biochim Biophys Acta Mol Basis Dis 2004; 1690:203-7. [PMID: 15511627 DOI: 10.1016/j.bbadis.2004.06.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 06/18/2004] [Accepted: 06/21/2004] [Indexed: 10/26/2022]
Abstract
We examined the proteinase inhibitor alpha2-macroglobulin (alpha2M) in plasma from patients with multiple sclerosis (MS); a neurological disease of the central nervous system. The plasma concentrations of native and transformed alpha2M were measured in 90 patients with clinically definite MS, 73 with relapsing-remitting and 17 with secondary progressive MS, and 132 healthy individuals. Significantly lower concentrations of native alpha2M and significantly higher concentrations of transformed alpha2M were found in MS patients. A significant correlation between the concentrations of native and transformed alpha2M was found. The fraction of transformed to total alpha2M in the MS patients was 36% higher than in the healthy individuals. The results suggest an important involvement of alpha2M in regulation of increased proteolytic activity occurring in MS disease.
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Affiliation(s)
- Poul Erik H Jensen
- The Neuroimmunology Laboratory, Section 9302, MS Research Unit, Copenhagen University Hospital, Juliane Mariesvej 20, 2100 Copenhagen, Denmark.
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Harauz G, Ishiyama N, Hill CMD, Bates IR, Libich DS, Farès C. Myelin basic protein-diverse conformational states of an intrinsically unstructured protein and its roles in myelin assembly and multiple sclerosis. Micron 2004; 35:503-42. [PMID: 15219899 DOI: 10.1016/j.micron.2004.04.005] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The 18.5 kDa isoform of myelin basic protein (MBP) is a major component of the myelin sheath in the central nervous system of higher vertebrates, and a member of a larger family of proteins with a multiplicity of forms and post-translational modifications (PTMs). The 18.5 kDa protein is the exemplar of the family, being most abundant in adult myelin, and thus the most-studied. It is peripherally membrane-associated, but has generally been investigated in isolated form. MBP is an 'intrinsically unstructured' protein with a high proportion (approximately 75%) of random coil, but postulated to have core elements of beta-sheet and alpha-helix. We review here the properties of the MBP family, especially of the 18.5 kDa isoform, and discuss how its three-dimensional (3D) structure may be resolved by direct techniques available to us, viz., X-ray and electron crystallography, and solution and solid-state NMR spectrometry. In particular, we emphasise that creating an appropriate environment in which the protein can adopt a physiologically relevant fold is crucial to such endeavours. By solving the 3D structure of 18.5 kDa MBP and the effects of PTMs, we will attain a better understanding of myelin architecture, and of the molecular mechanisms that transpire in demyelinating diseases such as multiple sclerosis.
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Affiliation(s)
- George Harauz
- Department of Molecular Biology and Genetics, Biophysics Interdepartmental Group, University of Guelph, Room 230, Axelrod Building, 50 Stone Road East, Guelph, Ont., Canada N1G 2W1.
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8
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Ritchie RF, Palomaki GE, Neveux LM, Navolotskaia O, Ledue TB, Craig WY. Reference distributions for alpha2-macroglobulin: a practical, simple and clinically relevant approach in a large cohort. J Clin Lab Anal 2004; 18:139-47. [PMID: 15065215 PMCID: PMC6807892 DOI: 10.1002/jcla.20012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Accepted: 09/17/2003] [Indexed: 02/03/2023] Open
Abstract
In this 11th article in a series, reference values of serum levels alpha(2)-macroglobulin alpha(2)M) are examined. The study is based on a cohort of 40,420 Caucasian individuals from northern New England that were tested in our laboratory between 1994 and 2000. Measurements were standardized against Certified Reference Material (CRM 470)/Reference Preparation for Proteins in Human Serum (RPPHS) and the results analyzed using a previously described statistical approach. Individuals with unequivocal laboratory evidence of inflammation (C-reactive protein >10 mg/L) were excluded in one leg of the study and included in the other, confirming that alpha(2)M does not respond to acute phase drive in man. Nephrotic syndrome, diabetes mellitus, and chronic liver disease have significant effect on levels of alpha(2)M. Dramatic changes occur during life with males higher from birth to age 12, females thereafter have higher values until the ninth decade. When values were expressed as multiples of the age- and gender-specific median levels, the resulting distributions fitted a log-Gaussian distribution well over a broad range. When patient data are normalized in this manner, the distribution parameters can be used to assign a centile corresponding to an individual's measurement thus simplifying interpretation.
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Gunnarsson M, Sundström P, Stigbrand T, Jensen PEH. Native and transformed alpha2-macroglobulin in plasma from patients with multiple sclerosis. Acta Neurol Scand 2003; 108:16-21. [PMID: 12807388 DOI: 10.1034/j.1600-0404.2003.00079.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Multiple sclerosis (MS) is an inflammatory demyelinating disease with unknown etiology. Various proteinases have been observed in increased levels in the central nervous system of patients with MS, which may contribute to the release of immunogenic myelin components. alpha2-Macroglobulin (alpha2M) inhibits a broad spectrum of proteinases sterically, undergoing major conformational changes induced by the proteinases themselves. Moreover, alpha2M acts as a carrier of several cytokines in the systemic circulation. By use of radial immunodiffusion, we determined the total alpha2M levels in plasma from 28 MS patients and 15 control subjects [14 patients with other neurologic diseases (OND) and one healthy individual]. No significant differences in total alpha2M concentration were observed between the MS patients and the control subjects. A comparison of the degree of alpha2M transformation in MS patients with different disease courses and controls was performed, using monoclonal antibodies (mAbs) specific for binding to native and transformed alpha2M, respectively. The fractions of transformed alpha2M were significantly increased in patients with secondary or primary progressive disease course compared with the controls. No significant differences were obtained using a native-specific mAb. At least a major proportion of alpha2M from the MS patients was able to change conformation from its native to its transformed state, as demonstrated by a shift in mAb reactivity, following methylamine treatment of the plasma samples. In conclusion, the results indicate that plasma alpha2M may be inactivated at a higher degree in patients with chronic progressive MS compared with patients with OND. This may influence the levels of proteinases and cytokines in the systemic circulation and may furthermore have diagnostic implications.
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Affiliation(s)
- M Gunnarsson
- Department of Immunology, Umeå University, Umeå, Sweden and Neuroimmunology Laboratory, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
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Gunnarsson M, Frängsmyr L, Stigbrand T, Jensen PEH. Stimulation of peripheral blood mononuclear cells with lipopolysaccharide induces expression of the plasma protein alpha2-macroglobulin. Protein Expr Purif 2003; 27:238-43. [PMID: 12597882 DOI: 10.1016/s1046-5928(02)00551-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The human alpha(2)-macroglobulin gene is approximately 48 kb in size and consists of 36 exons, which encode the 180 kDa subunit of this large tetrameric protein. In this investigation, a procedure of sequencing human alpha(2)-macroglobulin mRNA, using mRNA from lipopolysaccharide-stimulated peripheral blood mononuclear cells as template in RT-PCR, was developed. Incubation of peripheral blood mononuclear cell populations with lipopolysaccharide induced alpha(2)-macroglobulin mRNA expression reaching levels detectable by RT-PCR. Extracted human alpha(2)-macroglobulin mRNA was used to determine the nucleotide sequence of a 500 bp DNA segment encoding the most C-terminal, receptor-binding part of the protein, using alpha(2)-macroglobulin specific primers. The sequence obtained matched the earlier published sequence of human alpha(2)-macroglobulin, except for three point mutations, i.e., cytosine for guanine, cytosine for thymidine and thymidine for adenine substitutions at positions 4369, 4423, and 4511, respectively. None of these alterations, however, affect the amino acid sequence of the protein. In conclusion, we demonstrate a new, improved, approach to sequence human alpha(2)-macroglobulin mRNA by overexpressing the protein in peripheral blood mononuclear cells. This procedure may be useful in the search for mutations in alpha(2)-macroglobulin, examining its role in the pathogenesis of human diseases.
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11
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Gunnarsson M, Stigbrand T, Jensen PE. Aberrant forms of alpha(2)-macroglobulin purified from patients with multiple sclerosis. Clin Chim Acta 2000; 295:27-40. [PMID: 10767392 DOI: 10.1016/s0009-8981(00)00190-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The biochemical properties of alpha(2)-macroglobulin were investigated in four patients with multiple sclerosis and compared to alpha(2)-macroglobulin from healthy controls. An impaired stability of alpha(2)-macroglobulin from the multiple sclerosis patients was demonstrated as a spontaneous conversion to an electrophoretic"fast" form of alpha(2)-macroglobulin upon purification and storage, with a concomitant decrease in functional capacity to inhibit proteinases. The ability to form complexes with proteinases was significantly reduced in alpha(2)-macroglobulin purified from the multiple sclerosis patients. The aberrant molecular arrangements of the protein were not due to proteinase cleavages in the bait regions of alpha(2)-macroglobulin, as demonstrated by gel electrophoresis and protein sequencing. The number of functional thiol esters, however, was reduced in alpha(2)-macroglobulin purified from the multiple sclerosis patients, an observation compatible with the impaired proteinase binding property. Furthermore, differences in isoelectric points were observed between alpha(2)-macroglobulin from the multiple sclerosis patients and alpha(2)-macroglobulin from healthy controls. The results suggest that aberrant forms of alpha(2)-macroglobulin may be present in patients with multiple sclerosis.
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Affiliation(s)
- M Gunnarsson
- Department of Immunology, Umeâ University, S-901 85, Umeå, Sweden
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12
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Gonias SL, Carmichael A, Mettenburg JM, Roadcap DW, Irvin WP, Webb DJ. Identical or overlapping sequences in the primary structure of human alpha(2)-macroglobulin are responsible for the binding of nerve growth factor-beta, platelet-derived growth factor-BB, and transforming growth factor-beta. J Biol Chem 2000; 275:5826-31. [PMID: 10681572 DOI: 10.1074/jbc.275.8.5826] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha(2)-Macroglobulin (alpha(2)M) functions as a proteinase inhibitor and as a carrier of diverse growth factors. In this study, we localized binding sites for platelet-derived growth factor-BB (PDGF-BB) and nerve growth factor-beta (NGF-beta) to a linear sequence in the 180-kDa human alpha(2)M subunit which includes amino acids 591-774. A glutathione S-transferase fusion protein containing amino acids 591-774 (FP3) bound PDGF-BB and NGF-beta in ligand blotting assays whereas five other fusion proteins, which collectively include amino acids 99-590 and 775-1451 did not. The K(D) values for PDGF-BB and NGF-beta binding to immobilized FP3 were 300 +/- 40 and 180 +/- 30 nM, respectively; these values were comparable with those determined using methylamine-modified alpha(2)M, suggesting that higher-order alpha(2)M structure is not necessary for PDGF-BB and NGF-beta binding. PDGF-BB and NGF-beta blocked the binding of transforming growth factor-beta1 (TGF-beta1) to FP3. Furthermore, murinoglobulin, which is the only known member of the alpha-macroglobulin family that does not bind TGF-beta, also failed to bind PDGF-BB and NGF-beta. These results support the hypothesis that either a single linear sequence in human alpha(2)M or overlapping sequences are responsible for the binding of TGF-beta, PDGF-BB, and NGF-beta, even though there is minimal sequence identity between these three growth factors. FP3 blocked the binding of PDGF-BB to a purified chimeric protein, in which the extracellular domain of the PDGF beta receptor was fused to the IgG(1) Fc domain, and to PDGF receptors on NIH 3T3 cells. Thus, FP3 may inhibit the activity of PDGF-BB.
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Affiliation(s)
- S L Gonias
- Department of Pathology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
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