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Seeburun S, Wu S, Hemani D, Pham L, Ju D, Xie Y, Kata P, Li L. Insights into elastic fiber fragmentation: Mechanisms and treatment of aortic aneurysm in Marfan syndrome. Vascul Pharmacol 2023; 153:107215. [PMID: 37640090 PMCID: PMC10872825 DOI: 10.1016/j.vph.2023.107215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Accepted: 08/25/2023] [Indexed: 08/31/2023]
Abstract
Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutations in fibrillin 1 (FBN1) gene. These mutations result in defects in the skeletal, ocular, and cardiovascular systems. Aortic aneurysm is the leading cause of premature mortality in untreated MFS patients. Elastic fiber fragmentation in the aortic vessel wall is a hallmark of MFS-associated aortic aneurysms. FBN1 mutations result in FBN1 fragments that also contribute to elastic fiber fragmentation. Although recent research has advanced our understanding of MFS, the contribution of elastic fiber fragmentation to the pathogenesis of aneurysm formation remains poorly understood. This review provides a comprehensive overview of the molecular mechanisms of elastic fiber fragmentation and its role in the pathogenesis of aortic aneurysm progression. Increased comprehension of elastic fragmentation has significant clinical implications for developing targeted interventions to block aneurysm progression, which would benefit not only individuals with Marfan syndrome but also other patients with aneurysms. Moreover, this review highlights an overlooked connection between inhibiting aneurysm and the restoration of elastic fibers in the vessel wall with various aneurysm inhibitors, including drugs and chemicals. Investigating the underlying molecular mechanisms could uncover innovative therapeutic strategies to inhibit elastin fragmentation and prevent the progression of aneurysms.
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Affiliation(s)
- Sheilabi Seeburun
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
| | - Shichao Wu
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
| | - Darshi Hemani
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit MI, USA
| | - Lucynda Pham
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit MI, USA
| | - Donghong Ju
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
- Department of Oncology, Wayne State University, Detroit MI, USA
| | - Youming Xie
- Department of Oncology, Wayne State University, Detroit MI, USA
| | - Priyaranjan Kata
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
| | - Li Li
- Department of Internal Medicine, Wayne State University, Detroit MI, USA
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit MI, USA
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Mahdizadehi M, Saghaeian Jazi M, Mir SM, Jafari SM. Role of fibrilins in human cancer: A narrative review. Health Sci Rep 2023; 6:e1434. [PMID: 37469709 PMCID: PMC10353528 DOI: 10.1002/hsr2.1434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 06/25/2023] [Accepted: 07/07/2023] [Indexed: 07/21/2023] Open
Abstract
Background Fibrillin is one of the extracellular matrix glycoproteins and participates in forming microfibrils found in many connective tissues. The microfibrils enable the elasticity and stretching properties of the ligaments and support connective tissues. There are three isoforms of fibrillin molecules identified in mammals: fibrillin 1 (FBN1), fibrillin 2 (FBN2), and fibrillin 3. Objective Multiple studies have shown that mutations in these genes or changes in their expression levels can be related to various diseases, including cancers. In this study, we focus on reviewing the role of the fibrillin family in multiple cancers. Methods and Results We performed a comprehensive literature review to search PubMed and Google Scholar for studies published so far on fibrillin gene expression and its role in cancers. In this review, we have focused on the expression of FBN1 and FBN2 genes in cancers such as the lung, intestine, ovary, pancreatic ductal, esophagus, and thyroid. Conclusion Altogether various studies showed higher expression of fibrillins in different tumor tissues correlated with the patient's survival. However, there are controversial findings, as some other cancers showed hypermethylated FBN promoters with lower gene expression levels.
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Affiliation(s)
- Mahsa Mahdizadehi
- Metabolic Disorders Research CenterGolestan University of Medical SciencesGorganIran
- Department of Biochemistry and Biophysics, Faculty of MedicineGolestan University of Medical SciencesGorganIran
| | - Marie Saghaeian Jazi
- Metabolic Disorders Research CenterGolestan University of Medical SciencesGorganIran
| | - Seyyed Mostafa Mir
- Metabolic Disorders Research CenterGolestan University of Medical SciencesGorganIran
- Department of Biochemistry and Biophysics, Faculty of MedicineGolestan University of Medical SciencesGorganIran
| | - Seyyed Mehdi Jafari
- Metabolic Disorders Research CenterGolestan University of Medical SciencesGorganIran
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Salmasi MY, Alwis S, Cyclewala S, Jarral OA, Mohamed H, Mozalbat D, Nienaber CA, Athanasiou T, Morris-Rosendahl D. The genetic basis of thoracic aortic disease: The future of aneurysm classification? Hellenic J Cardiol 2023; 69:41-50. [PMID: 36202327 DOI: 10.1016/j.hjc.2022.09.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/24/2022] [Accepted: 09/25/2022] [Indexed: 11/04/2022] Open
Abstract
The expansion in the repertoire of genes linked to thoracic aortic aneurysms (TAA) has revolutionised our understanding of the disease process. The clinical benefits of such progress are numerous, particularly helping our understanding of non-syndromic hereditary causes of TAA (HTAAD) and further refinement in the subclassification of disease. Furthermore, the understanding of aortic biomechanics and mechanical homeostasis has been significantly informed by the discovery of deleterious mutations and their effect on aortic phenotype. The drawbacks in genetic testing in TAA lie with the inability to translate genotype to accurate prognostication in the risk of thoracic aortic dissection (TAD), which is a life-threatening condition. Under current guidelines, there are no metrics by which those at risk for dissection with normal aortic diameters may undergo preventive surgery. Future research lies with more advanced genetic diagnosis of HTAAD and investigation of the diverse pathways involved in its pathophysiology, which will i) serve to improve our understanding of the underlying mechanisms, ii) improve guidelines for treatment and iii) prevent complications for HTAAD and sporadic aortopathies.
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Affiliation(s)
| | | | | | - Omar A Jarral
- Department of Surgery and Cancer, Imperial College London, UK
| | - Heba Mohamed
- Royal Brompton and Harefield Foundation Trust, UK
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Cheng A, Cain SA, Tian P, Baldwin AK, Uppanan P, Kielty CM, Kimber SJ. Recombinant Extracellular Matrix Protein Fragments Support Human Embryonic Stem Cell Chondrogenesis. Tissue Eng Part A 2018; 24:968-978. [PMID: 29279011 PMCID: PMC5984563 DOI: 10.1089/ten.tea.2017.0285] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We previously developed a 14-day culture protocol under potentially GMP, chemically defined conditions, to generate chondroprogenitors from human embryonic stem cells (hESCs). In vivo work has confirmed the cartilage repair capacity of these cells in a nude rat osteochondral defect model. Aiming to enhance hESC-chondrogenesis, we screened a range of extracellular matrix (ECM) molecules for their ability to support differentiation of hESCs toward chondrocytes. We identified two novel ECM protein fragments that supported hESC-chondrogenesis: Fibronectin III (fibronectin 7-14 protein fragments, including the RGD domain, syndecan-binding domain, and heparin-binding domain) and fibrillin-1 (FBN1) fragment PF8 (encoded by exons 30-38, residues 1238-1605, which contains the RGD motif but not heparin-binding site). These two protein fragments support hESC-chondrogenesis compared with the substrates routinely used previously (a mixture of fibronectin and gelatin) in our directed chondrogenic protocol. We have identified recombinant fibronectin fragment (FN III) and FBNI fragment (PF8) as alternative coating substrates to promote expression of genes known to regulate chondrocytes and code for chondrocyte ECM components. These recombinant protein fragments are likely to have better batch to batch stability than full-length molecules, especially where extracted from tissue/serum.
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Affiliation(s)
- Aixin Cheng
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Stuart A. Cain
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Pinyuan Tian
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Andrew K. Baldwin
- Academic Group—Engineering, Sports and Sciences, The University of Bolton, Bolton, United Kingdom
| | | | - Cay M. Kielty
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Susan J. Kimber
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
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Sartor L, Forteza A. Strategies to prevent aortic complications in Marfan syndrome. J Thorac Dis 2017; 9:S434-S438. [PMID: 28616337 DOI: 10.21037/jtd.2017.04.69] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Lucio Sartor
- Division of Cardiovascular Surgery, Hospital Universitario Quirónsalud Madrid, Madrid, Spain
| | - Alberto Forteza
- Division of Cardiovascular Surgery, Hospital Universitario Quirónsalud Madrid, Madrid, Spain.,Marfan Unit, Hospital Universitario Puerta de Hierro Majadahonda, Madrid, Spain
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Romaniello F, Mazzaglia D, Pellegrino A, Grego S, Fiorito R, Ferlosio A, Chiariello L, Orlandi A. Aortopathy in Marfan syndrome: an update. Cardiovasc Pathol 2014; 23:261-6. [PMID: 24925629 DOI: 10.1016/j.carpath.2014.04.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 04/29/2014] [Accepted: 04/30/2014] [Indexed: 12/11/2022] Open
Abstract
Marfan syndrome (MFS) is an inherited autosomal dominant multisystem disease caused by mutations in the FBN1 gene encoding fibrillin-1, an extracellular matrix glycoprotein widely distributed in mesenchymal-derived tissues that provide a scaffold for elastin deposition. MFS is characterized by variable clinical manifestations, including skeletal, ocular, and cardiovascular abnormalities; ascending aortic aneurysm with ensuing dissection and rupture is the main life-threatening cardiovascular manifestation of MFS. Histological aspects of MFS aortopathy include a medial degeneration from disarray and fragmentation of elastic fibers and accumulation of basophilic ground substance areas depleted of smooth muscle cells (SMCs). Transmission electron microscopy well evidences the high number of interruptions and the thick appearance of the elastic lamellae and the accumulation of abundant extracellular glycosaminoglycan-rich material, sometimes SMCs showing a prevalent synthetic phenotype. The aberrant signaling of transforming growth factor-β (TGF-β) as the consequence of the altered structure of fibrillin-1 induces activation and the overexpression of Smad-dependent profibrotic signaling pathway and ERK1/2-mediated increased synthesis of matrix metalloproteinases. In addition, MFS is accompanied by an impaired aortic contractile function and aortic endothelial-dependent relaxation, which is caused by an enhancement of the oxidative stress and increased reactive oxygen species during the progression of the disease. Many studies are currently evaluating the contribution of TGF-β-mediated biomolecular pathways to the progression of MFS aortopathy and aneurysm development, in order to discover new targets for pharmacological strategies aimed to counteract aortic dilation.
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Affiliation(s)
- Federico Romaniello
- Institute of Anatomic Pathology, Dept. of Biomedicine and Prevention, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Donatella Mazzaglia
- Institute of Anatomic Pathology, Dept. of Biomedicine and Prevention, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Antonio Pellegrino
- Cardiac Surgery, Dept. of Experimental Medicine and Surgery, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Susanna Grego
- Cardiac Surgery, Dept. of Experimental Medicine and Surgery, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Roberto Fiorito
- General Surgery, Dept. of Biomedicine and Prevention, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Amedeo Ferlosio
- Institute of Anatomic Pathology, Dept. of Biomedicine and Prevention, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Luigi Chiariello
- Cardiac Surgery, Dept. of Experimental Medicine and Surgery, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy
| | - Augusto Orlandi
- Institute of Anatomic Pathology, Dept. of Biomedicine and Prevention, Tor Vergata University of Rome, Via Montpellier, 00133 Rome, Italy.
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Boregowda RK, Krovic BM, Ritty TM. Selective integrin subunit reduction disrupts fibronectin extracellular matrix deposition and fibrillin 1 gene expression. Mol Cell Biochem 2012; 369:205-16. [PMID: 22782528 DOI: 10.1007/s11010-012-1383-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/20/2012] [Indexed: 10/28/2022]
Abstract
Integrins are transmembrane receptors that can specifically bind extracellular matrix (ECM) proteins. Assembly of the ECM protein fibronectin into fibrils has been shown to be a cell-mediated process that requires integrins. Like fibronectin, fibrillin 1 is an ECM glycoprotein that can assemble into fibrils, but the role of integrins in fibril formation is not understood. To investigate the role of integrins in fibrillin 1 ECM deposition, cells that normally produce and assemble fibrillin 1 fibers in vitro were stably transfected with plasmid constructs encoding short interfering RNAs that target specific integrin subunits. Cells that were deficient in α2- and β3-integrin subunits produced and deposited fibronectin normally, but cells that were deficient for α5 and αV were unable to elaborate a fibronectin matrix, although they continued to produce and secrete the protein. Surprisingly, the cells that were unable to elaborate a fibronectin matrix also lost fibrillin 1 gene expression.
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Affiliation(s)
- Rajeev K Boregowda
- Division of Musculoskeletal Sciences, Department of Orthopaedics, Penn State College of Medicine, Hershey, PA 17033, USA.
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Guo G, Gehle P, Doelken S, Martin-Ventura JL, von Kodolitsch Y, Hetzer R, Robinson PN. Induction of macrophage chemotaxis by aortic extracts from patients with Marfan syndrome is related to elastin binding protein. PLoS One 2011; 6:e20138. [PMID: 21647416 PMCID: PMC3103536 DOI: 10.1371/journal.pone.0020138] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 04/15/2011] [Indexed: 11/18/2022] Open
Abstract
Marfan syndrome is an autosomal dominantly inherited disorder of connective tissue with prominent skeletal, ocular, and cardiovascular manifestations. Aortic aneurysm and dissection are the major determinants of premature death in untreated patients. In previous work, we showed that extracts of aortic tissues from the mgR mouse model of Marfan syndrome showed increased chemotactic stimulatory activity related to the elastin-binding protein. Aortic samples were collected from 6 patients with Marfan syndrome and 8 with isolated aneurysms of the ascending aorta. Control samples were obtained from 11 organ donors without known vascular or connective tissue diseases. Soluble proteins extracted from the aortic samples of the two patient groups were compared against buffer controls and against the aortic samples from controls with respect to the ability to induce macrophage chemotaxis as measured using a modified Boyden chamber, as well as the reactivity to a monoclonal antibody BA4 against bioactive elastin peptides using ELISA. Samples from Marfan patients displayed a statistically significant increase in chemotactic inductive activity compared to control samples. Additionally, reactivity to BA4 was significantly increased. Similar statistically significant increases were identified for the samples from patients with idiopathic thoracic aortic aneurysm. There was a significant correlation between the chemotactic index and BA4 reactivity, and the increases in chemotactic activity of extracts from Marfan patients could be inhibited by pretreatment with lactose, VGVAPG peptides, or BA4, which indicates the involvement of EBP in mediating the effects. Our results demonstrate that aortic extracts of patients with Marfan syndrome can elicit macrophage chemotaxis, similar to our previous study on aortic extracts of the mgR mouse model of Marfan syndrome (Guo et al., Circulation 2006; 114:1855-62).
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Affiliation(s)
- Gao Guo
- Institute for Medical and Human Genetics, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Petra Gehle
- Deutsches Herzzentrum Berlin (DHZB, German Heart Institute Berlin), Berlin, Germany
- Marfan-Zentrum des DHZB und der Charité, Berlin, Germany
| | - Sandra Doelken
- Institute for Medical and Human Genetics, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Max-Planck-Institute for Molecular Genetics, Berlin, Germany
- Berlin Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - José Luis Martin-Ventura
- Vascular Research Laboratory, Instituto de Investigacion Sanitaria, Fundación Jimenez Diaz, Autonoma University, Madrid, Spain
| | - Yskert von Kodolitsch
- Centre of Cardiology and Cardiovascular Surgery, Department of Cardiology/Angiology, University Hospital Hamburg–Eppendorf, Hamburg, Germany
| | - Roland Hetzer
- Deutsches Herzzentrum Berlin (DHZB, German Heart Institute Berlin), Berlin, Germany
- Marfan-Zentrum des DHZB und der Charité, Berlin, Germany
| | - Peter N. Robinson
- Institute for Medical and Human Genetics, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Marfan-Zentrum des DHZB und der Charité, Berlin, Germany
- Max-Planck-Institute for Molecular Genetics, Berlin, Germany
- Berlin Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin Berlin, Berlin, Germany
- * E-mail:
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Biomechanics and Pathobiology of Aortic Aneurysms. STUDIES IN MECHANOBIOLOGY, TISSUE ENGINEERING AND BIOMATERIALS 2011. [DOI: 10.1007/8415_2011_84] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Loeys BL, Gerber EE, Riegert-Johnson D, Iqbal S, Whiteman P, McConnell V, Chillakuri CR, Macaya D, Coucke PJ, De Paepe A, Judge DP, Wigley F, Davis EC, Mardon HJ, Handford P, Keene DR, Sakai LY, Dietz HC. Mutations in fibrillin-1 cause congenital scleroderma: stiff skin syndrome. Sci Transl Med 2010; 2:23ra20. [PMID: 20375004 PMCID: PMC2953713 DOI: 10.1126/scitranslmed.3000488] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The predisposition for scleroderma, defined as fibrosis and hardening of the skin, is poorly understood. We report that stiff skin syndrome (SSS), an autosomal dominant congenital form of scleroderma, is caused by mutations in the sole Arg-Gly-Asp sequence-encoding domain of fibrillin-1 that mediates integrin binding. Ordered polymers of fibrillin-1 (termed microfibrils) initiate elastic fiber assembly and bind to and regulate the activation of the profibrotic cytokine transforming growth factor-beta (TGFbeta). Altered cell-matrix interactions in SSS accompany excessive microfibrillar deposition, impaired elastogenesis, and increased TGFbeta concentration and signaling in the dermis. The observation of similar findings in systemic sclerosis, a more common acquired form of scleroderma, suggests broad pathogenic relevance.
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Affiliation(s)
- B L Loeys
- Institute of Genetic Medicine and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Broadway Research Building, Room 539, 733 North Broadway, Baltimore, MD 21205, USA
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Yang HHC, Kim JM, Chum E, van Breemen C, Chung AWY. Long-term effects of losartan on structure and function of the thoracic aorta in a mouse model of Marfan syndrome. Br J Pharmacol 2009; 158:1503-12. [PMID: 19814725 DOI: 10.1111/j.1476-5381.2009.00443.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE During development of thoracic aortic aneurysms in a mouse model of Marfan syndrome, upregulation of matrix metalloproteinase (MMP)-2 and -9 was accompanied by compromised aortic constriction and endothelium-dependent relaxation. Losartan has been proposed for the prevention of thoracic aortic aneurysm. We hypothesized that losartan would suppress MMP-2/-9 activation and improve aortic vasomotor function in this model. EXPERIMENTAL APPROACH A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. Starting at 6 weeks old, Marfan mice were untreated or given losartan (0.6 g.L(-1) in drinking water, n= 30). The littermate Fbn1(+/+) mice served as control. Thoracic aortas were studied at 3, 6 and 9 months by histology and by contractility assays in isolated segments in vitro. KEY RESULTS Losartan improved elastic fibre organization and increased aortic breaking stress. Losartan reduced the activity and protein expression of MMP-2 and MMP-9 at all ages. Aortic constriction in response to membrane depolarization or phenylephrine was increased by losartan at 3 and 9 months by 100-200%. Active force of aortic smooth muscle was also increased at 6 and 9 months. Acetylcholine-induced endothelium-dependent relaxation was improved by 30% after 3 months of losartan treatment, but such improvement disappeared with longer duration of treatment, accompanied by reduced phosphorylation of endothelial nitric oxide (NO) synthase(Ser1177), Akt(Thr308) and Akt(Ser473), compared with the control. CONCLUSIONS AND IMPLICATIONS Losartan improved the contractile function of aorta and reduced MMP activation. However, the endothelial NO pathway remained suppressed in the thoracic aorta during losartan treatment, which might limit its long-term benefits in Marfan syndrome.
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Affiliation(s)
- H H Clarice Yang
- Department of Cardiovascular Science, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada
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Affiliation(s)
- Martin G. Keane
- From the Departments of Medicine (M.G.K., R.E.P.) and Genetics (R.E.P.) and the Institute for Cardiovascular Medicine (M.G.K., R.E.P.), University of Pennsylvania School of Medicine, Philadelphia
| | - Reed E. Pyeritz
- From the Departments of Medicine (M.G.K., R.E.P.) and Genetics (R.E.P.) and the Institute for Cardiovascular Medicine (M.G.K., R.E.P.), University of Pennsylvania School of Medicine, Philadelphia
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Abstract
Human fibrillin-1 is the major structural protein of extracellular matrix 10–12 nm microfibrils. It has a disulfide-rich modular organization which consists primarily of cbEGF (Ca2+-binding epidermal growth factor-like) domains and TB (transforming growth factor β-binding protein-like) domains. TB4 contains an RGD (Arg-Gly-Asp) integrin-binding motif. The atomic structure of this region has been solved by X-ray crystallography and shows the TB4 and flanking cbEGF domains to be arranged as a tetragonal pyramid with N- and C-termini exposed at opposite ends of the fragment. The RGD integrin-binding motif is located within a flexible loop. We have used a variety of biophysical, biochemical and cell biology methods to investigate the molecular properties of integrin–fibrillin-1 interactions and have demonstrated that recombinant fibrillin-1 domain fragments mediate binding to integrins αVβ3, α5β1 and αVβ6. Integrin αVβ3 is a high-affinity fibrillin-1 receptor (Kd ∼40 nM), whereas integrins αVβ6 and α5β1 show moderate-affinity (Kd ∼450 nM) and low-affinity (Kd >1 μM) binding respectively. Different patterns of α5β1 distribution are seen when human keratinocytes and fibroblasts are plated on to fibrillin domain fragments compared with those seen for fibronectin, suggesting that fibrillin may cause a lesser degree or different type of intracellular signalling. A number of disease-causing mutations which affect the TB4 domain have been identified. These are being investigated for their effects on integrin binding and/or changes in intramolecular structure.
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McGowan SE, Holmes AJ, Mecham RP, Ritty TM. Arg-Gly-Asp-containing domains of fibrillins-1 and -2 distinctly regulate lung fibroblast migration. Am J Respir Cell Mol Biol 2007; 38:435-45. [PMID: 18006876 DOI: 10.1165/rcmb.2007-0281oc] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Development of the extracellular matrix is a critical feature of alveolar formation and actively involves pulmonary interstitial fibroblasts. The elastic fiber network is an interconnected system of load-bearing fibers that also influences the behavior of adjacent cells, particularly the interstitial lung fibroblasts (LF). We hypothesized that discrete domains of fibrillins-1 and -2 interact with LF integrins and direct their migration in the presence of platelet-derived growth factor (PDGF)-A. Surfaces coated with recombinant peptides lacking or including an arginine-glycine-aspartic acid (RGD) motif were used to study LF migration across porous filters and on protein-coated glass. Exon 24 of fibrillin-2 (Fib2 24), which encodes for an RGD-containing transforming growth factor-beta-binding (TB) domain, stimulated migration with greater directional persistence and more effectively stimulated trans-filter migration at low concentrations. Exons 36-44 of fibrillin-1 (Fib1 36-44), which include epidermal growth factor-like domains and an RGD-containing TB domain, induce more lamlellipodia and more widespread remodeling of the leading edge, resulting in greater migration velocity than did Fib2 24. Distinct structural features in regions that surround the RGD motifs may differentially regulate how the PDGF receptor-alpha promotes integrin distribution and actin filament remodeling at the cell's leading edge. Understanding how fibrillins regulate LF migration may help elucidate how the elastic fiber system could be restored as an interconnected unit, which fails to occur in emphysematous lungs.
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Affiliation(s)
- Stephen E McGowan
- Department of Veterans Affairs Research Service and University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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Jovanovic J, Takagi J, Choulier L, Abrescia NGA, Stuart DI, van der Merwe PA, Mardon HJ, Handford PA. αVβ6 Is a Novel Receptor for Human Fibrillin-1. J Biol Chem 2007; 282:6743-51. [PMID: 17158881 DOI: 10.1074/jbc.m607008200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human fibrillin-1, the major structural protein of connective tissue 10-12 nm microfibrils, contains multiple calcium binding epidermal growth factor-like domains interspersed with transforming growth factor beta-binding protein-like (TB) domains. TB4 contains a flexible RGD loop that mediates cell adhesion via alphaVbeta3 and alpha5beta1 integrins. This study identifies integrin alphaVbeta6 as a novel cellular receptor for fibrillin-1 with a K(d) of approximately 0.45 mum. Analyses of this interaction by surface plasmon resonance and immunocytochemistry reveal different module requirements for alphaVbeta6 activation compared with those of alphaVbeta3, suggesting that a covalent linkage of an N-terminal calcium binding epidermal growth factor-like domain to TB4 can modulate alphaV integrin binding specificity. Furthermore, our data suggest alpha5beta1 is a low affinity fibrillin-1 receptor (K(d) > 1 mum), thus providing a molecular explanation for the different alpha5beta1 distribution patterns seen when human keratinocytes and fibroblasts are plated on recombinant fibrillin fragments versus those derived from the physiological ligand fibronectin. Non-focal contact distribution of alpha5beta1 suggests that its engagement by fibrillin-1 may elicit a lesser degree and/or different type of intracellular signaling compared with that seen with a high affinity ligand.
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Affiliation(s)
- Jelena Jovanovic
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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Tseleni-Balafouta S, Gakiopoulou H, Fanourakis G, Voutsinas G, Litsiou H, Sozopoulos E, Balafoutas D, Patsouris E. Fibrillin expression and localization in various types of carcinomas of the thyroid gland. Mod Pathol 2006; 19:695-700. [PMID: 16528372 DOI: 10.1038/modpathol.3800578] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fibrillin is an extracellular matrix (ECM) glycoprotein, a main component of microfibrills, suggested to support cell attachment and to impact cell differentiation and migration. The aim of this study was to investigate fibrillin-1 expression in thyroid carcinomas at mRNA and protein level, since ECM proteins are suggested to be of great importance for the metastatic potential of carcinomas. RNA was extracted from 13 thyroid carcinoma cell lines and RT-PCR analysis with gene-specific primers revealed fibrillin-1 mRNA expression in all cell lines, with highest expression in the follicular carcinoma cell line WRO and lowest expression in the two anaplastic cell lines (APO, FRO). Furthermore, we investigated fibrillin-1 expression by immumohistochemistry in a commercially available tissue microarray including 50 thyroid carcinomas as well as in archival tissue from 33 thyroid carcinomas. Fibrillin-1 demonstrated a cytoplasmic location in the neoplastic cells of almost all carcinomas apart from the follicular ones. The most intense staining was observed in papillary carcinomas with some evidence of a slight increased intensity in advanced stages. Our data indicate that fibrillin-1 is strongly expressed by the neoplastic cells of thyroid carcinomas in different degree in the various histologic types and might be implicated in cell-stroma interaction in terms of signaling, attachment and migration.
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MESH Headings
- Adenocarcinoma, Follicular/genetics
- Adenocarcinoma, Follicular/metabolism
- Adenocarcinoma, Follicular/pathology
- Adolescent
- Adult
- Aged
- Carcinoma, Medullary/genetics
- Carcinoma, Medullary/metabolism
- Carcinoma, Medullary/pathology
- Carcinoma, Papillary/genetics
- Carcinoma, Papillary/metabolism
- Carcinoma, Papillary/pathology
- Cell Line, Tumor
- Female
- Fibrillin-1
- Fibrillins
- Humans
- Immunohistochemistry
- Male
- Microfilament Proteins/analysis
- Microfilament Proteins/genetics
- Middle Aged
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Thyroid Neoplasms/genetics
- Thyroid Neoplasms/metabolism
- Thyroid Neoplasms/pathology
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17
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Dietz HC, Loeys B, Carta L, Ramirez F. Recent progress towards a molecular understanding of Marfan syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2005; 139C:4-9. [PMID: 16273535 DOI: 10.1002/ajmg.c.30068] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Marfan syndrome (MFS) is a systemic disorder of the connective tissue that is inherited as an autosomal dominant trait and which displays variable manifestations in the ocular, skeletal, and cardiovascular systems. These pleiotropic manifestations are accounted for by mutations in fibrillin-1, the building block of extracellular microfibrils. During the past 10 years, we have witnessed significant progress in delineating the pathological events responsible for the manifestations of MFS. Much of this progress has been based on the creation and analysis of fibrillin-1 mutant mouse lines that faithfully recapitulate the spectrum of clinical severity of MFS. These studies have established the critical contribution of fibrillin-1 deficiency to disease progression through altered cell-matrix interactions and dysregulated TGF-beta signaling. As a result, our definition of MFS as the prototypical structural disorder of the connective tissue has changed to that of a developmental abnormality with broad and complex effects on the morphogenesis and function of multiple organ systems. Importantly, new biological targets have emerged that may yield exciting new opportunities for the development of productive treatment strategies in MFS.
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Affiliation(s)
- Harry C Dietz
- Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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18
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Bouzeghrane F, Reinhardt DP, Reudelhuber TL, Thibault G. Enhanced expression of fibrillin-1, a constituent of the myocardial extracellular matrix in fibrosis. Am J Physiol Heart Circ Physiol 2005; 289:H982-91. [PMID: 15849235 DOI: 10.1152/ajpheart.00151.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fibrillin-1 localization in the myocardium and the modulation of its expression in cardiac fibrosis were examined. In normal rat hearts, fibrillin-1 was abundant throughout the myocardium as thin fibers that crossed over the perimysium and around arteries. After cardiac fibrosis was induced in rats by either 14-day ANG II infusion or 21-day DOCA-salt treatment [a high endothelin-1 (ET-1) model], fibrillin-1 immunostaining was stronger in the interstitium (2.8-fold and 4.4-fold increases, respectively, in each model), extended between myocytes, and accumulated in microscopic scars and in the perivascular area of both ventricles. mRNA analysis confirmed its enhanced ventricular expression in both groups of rats (2.5-fold and 6.6-fold increments, respectively, in each model). In 1B normotensive and 2C hypertensive transgenic mice, two lines expressing an ANG II fusion protein in cardiac myocytes, strong fibrillin-1 immunoreactivity was observed in the interstitium and around arteries (3.7-fold and 7-fold increases, respectively). ANG II and transforming growth factor-beta1 enhanced fibrillin-1 synthesis by cardiac fibroblasts. Some fibrillin-1 fragments interacted with RGD-dependent integrins, including alpha(8)beta(1)-integrin, of cardiac fibroblasts but not necessarily through the RGD motif. Our findings illustrate that fibrillin-1 is an important constituent of the myocardium. In vitro and in vivo evidence suggests that ANG II can directly induce fibrillin-1 expression in cardiac fibroblasts. This protein can thus contribute to reactive and reparative processes.
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Affiliation(s)
- Fatiha Bouzeghrane
- Institut de Recherches Cliniques de Montréal, Montréal, Québec, Canada H2W 1R7
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19
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Lemaire R, Korn JH, Schiemann WP, Lafyatis R. Fibulin-2 and fibulin-5 alterations in tsk mice associated with disorganized hypodermal elastic fibers and skin tethering. J Invest Dermatol 2005; 123:1063-9. [PMID: 15610515 DOI: 10.1111/j.0022-202x.2004.23471.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Tight skin (Tsk) mouse is an important model of skin fibrosis that occurs in systemic sclerosis. These mice develop skin tethering and thickening associated with expression of a mutant fibrillin-1 gene. We show that Tsk fibrillin-1 leads to marked alterations in elastic fibers of the hypodermis of Tsk animals. In Tsk mice, a prominent elastic fiber layer found normally at the interface between hypodermal muscle and connective tissue was absent from an early age. The lack of elastic fibers at the hypodermal muscle-connective tissue (M-CT) interface was associated with a loss of staining for fibulin-5 in the same region. These mice also formed disorganized elastic fibers throughout hypodermal connective tissue as they aged. The increased elastic fibers in Tsk hypodermal connective tissue was associated with increased fibrillin-1 and fibulin-2 matrices. These results suggest that Tsk fibrillin-1 causes skin tethering by altering matrix protein composition in Tsk hypodermal connective tissues. The closely parallel alterations in elastogenesis associated with increased fibulin-2 in hypodermal connective tissues and decreased fibulin-5 at the hypodermal M-CT interface suggest that these proteins mediate the effect of Tsk-fibrillin-1 on elastogenesis.
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Affiliation(s)
- Raphael Lemaire
- The Arthritis Center, Boston University School of Medicine, Boston, Massachusetts, USA
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20
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Hyytiäinen M, Penttinen C, Keski-Oja J. Latent TGF-beta binding proteins: extracellular matrix association and roles in TGF-beta activation. Crit Rev Clin Lab Sci 2004; 41:233-64. [PMID: 15307633 DOI: 10.1080/10408360490460933] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Transforming growth factor betas (TGF-betas) are multifunctional and pleiotropic growth factors. Their major effects include inhibition of cell proliferation and enhancement of extracellular matrix production. TGF-betas are secreted from cells as latent complexes, consisting of mature dimeric growth factor, the latency-associated propeptide (LAP), and a distinct gene product, latent TGF-beta binding protein LTBP. The secreted complex is targeted to specific locations in the extracellular matrix by the appropriate LTBP. The latent complex needs subsequently to be activated. Most studies describing biological effects of TGF-beta have been carried out in cell cultures using high concentrations of active, soluble TGF-beta, where appropriate targeting of the growth factor is missing. However, TGF-beta is produced and secreted in vivo as a latent complex in a specific and targeted manner. Various experimental approaches have convincingly shown the importance of the activation of latent TGF-beta, as well as the importance of LTBPs as targeting molecules of the effects of TGF-beta. Essential steps in the activation appear to be cellular recognition of extracellular matrix-associated LTBPs and subsequent recognition of the associated latent TGF-beta. Cell recognition by specific molecules like integrins and proteolytic events involving plasminogen activation evidently play multifaceted roles in the regulation of TGF-beta activation.
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Affiliation(s)
- Marko Hyytiäinen
- Department of Virology, Haartman Institute and Helsinki University Hospital, University of Helsinki, Finland
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21
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Booms P, Pregla R, Ney A, Barthel F, Reinhardt DP, Pletschacher A, Mundlos S, Robinson PN. RGD-containing fibrillin-1 fragments upregulate matrix metalloproteinase expression in cell culture: a potential factor in the pathogenesis of the Marfan syndrome. Hum Genet 2004; 116:51-61. [PMID: 15517394 DOI: 10.1007/s00439-004-1194-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 09/07/2004] [Indexed: 10/26/2022]
Abstract
The Marfan syndrome (MFS), a relatively common autosomal dominant disorder of connective tissue, is caused by mutations in the gene for fibrillin-1 (FBN1). Fibrillin-1 is the main component of the 10- to 12-nm microfibrils that together with elastin form elastic fibers found in tissues such as the aortic media. Recently, FBN1 mutations have been shown to increase the susceptibility of fibrillin-1 to proteolysis in vitro, and other findings suggest that up-regulation of matrix metalloproteinases (MMP), as well as fragmentation of microfibrils, could play a role in the pathogenesis of MFS. In the present work, we have investigated the influence of fibrillin-1 fragments on the expression of MMP-1, MMP-2, and MMP-3 in a cell culture system. Cultured human dermal fibroblasts were incubated with several different recombinant fibrillin-1 fragments. The expression level of MMP-1, MMP-2, and MMP-3, was determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and the concentration of the corresponding proteins was estimated by quantitative Western blotting. Our results establish that treatment of cultured human dermal fibroblasts with recombinant fibrillin-1 fragments containing the arginine-glycine-aspartic acid (RGD) integrin-binding motif of fibrillin-1 induces up-regulation of MMP-1 and MMP-3. A similar effect was seen upon stimulation with a synthetic RGD peptide. The expression of MMP-2 was not influenced by treatment. Our results suggest the possibility that fibrillin fragments could themselves have pathogenic effects by leading to up-regulation of MMPs, which in turn may be involved in the progressive breakdown of microfibrils thought to play a role in MFS.
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Affiliation(s)
- Patrick Booms
- Institute of Medical Genetics, Charité University Hospital, Humboldt University Berlin, Augustenburger Platz 1, Berlin 13353, Germany
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22
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Lorena D, Darby IA, Reinhardt DP, Sapin V, Rosenbaum J, Desmoulière A. Fibrillin-1 expression in normal and fibrotic rat liver and in cultured hepatic fibroblastic cells: modulation by mechanical stress and role in cell adhesion. J Transl Med 2004; 84:203-12. [PMID: 14661032 DOI: 10.1038/labinvest.3700023] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Fibrillin-1, together with elastin, is the main component of elastic fibers found throughout the extracellular space and responsible for the biomechanical properties of most tissues and organs. In this work, fibrillin-1 expression and modulation were explored in experimental rat liver fibrosis and in vitro; furthermore, the role of fibrillin-1 fragments on cell adhesion was analyzed. Fibrosis was induced by subjecting rats to common bile duct ligation for 72 h and 7 days or carbon tetrachloride (CCl(4)) treatment for 2 and 6 weeks. Immunohistochemistry showed that, after bile duct ligation, fibrillin-1, elastin, and alpha-smooth muscle actin colocalized in the developing portal connective tissue. In CCl(4)-treated animals, a similar colocalization was observed in septa; however, elastin deposition was not observed around activated alpha-smooth muscle actin-positive stellate cells of the parenchyma. Treatment with the profibrogenic mediator transforming growth factor-beta1 (TGF-beta1) greatly increased the fibrillin-1 expression of cultured liver fibroblasts. The level of fibrillin-1 expression was significantly higher in cells grown in restrained (stressed) collagen lattices compared with those grown in unrestrained collagen lattices. Cell adhesion on the C-terminal fragment of fibrillin-1 containing the RGD sequence (rF6H) slightly increased (between 0.3 and 2.5 microg/ml) and decreased at higher concentrations, while adhesion on the N-terminal fragment of fibrillin-1 (rF16) was dose-dependently decreased. In addition, the rF16 fragment decreased cell adhesion to fibronectin. In conclusion, our study illustrates the important deposition of fibrillin-1 that occurs in two mechanistically distinct settings of liver fibrogenesis. Furthermore, the induction of fibrillin-1 expression by TGF-beta1 and mechanical stress, and the antiadhesive properties of fibrillin-1 fragments suggest important implications for physiological and pathological fibrillin-1 catabolism during tissue remodeling.
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Affiliation(s)
- Dionne Lorena
- Groupe de Recherches pour l'Etude du Foie, INSERM E0362, and Institut Fédératif de Recherche 66, Pathologies Infectieuses et Cancers, Université Victor Segalen Bordeaux 2, Bordeaux, France
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23
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Affiliation(s)
- Cassandra M Kelleher
- Washington University School of Medicine, Department of Cell Biology and Physiology, St. Louis, Missouri 63110, USA
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24
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Ritty TM, Broekelmann TJ, Werneck CC, Mecham RP. Fibrillin-1 and -2 contain heparin-binding sites important for matrix deposition and that support cell attachment. Biochem J 2003; 375:425-32. [PMID: 12837131 PMCID: PMC1223679 DOI: 10.1042/bj20030649] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2003] [Revised: 06/25/2003] [Accepted: 07/02/2003] [Indexed: 01/10/2023]
Abstract
Fibrillin-1 and -2 are large modular extracellular matrix glycoproteins found in many vertebrate organ systems and are known to be key components of the elastic fibre. In the present study, we identify a new heparin-binding region in fibrillin-2 between exons 18 and 24. Additionally, we have narrowed the location of heparin-binding activity previously identified in fibrillin-1 to the last 17 residues of the mature proteolytically processed protein. This domain demonstrated higher activity as a multimer than as a monomer. The fibrillin-1 C-terminal site supported cell attachment in each of nine cell types tested. Attachment was shown to be mediated by cell-surface heparan sulphate proteoglycans. Fibrillin-1 has been shown previously to have heparin-binding activity that is important for matrix deposition of the molecule by fibroblasts. This function in deposition was confirmed in two additional fibrillin-producing cell types (osteosarcoma and epithelial cells) for the deposition of both fibrillin-1 and -2 into the extracellular matrix.
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Affiliation(s)
- Timothy M Ritty
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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25
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Bax DV, Bernard SE, Lomas A, Morgan A, Humphries J, Shuttleworth CA, Humphries MJ, Kielty CM. Cell adhesion to fibrillin-1 molecules and microfibrils is mediated by alpha 5 beta 1 and alpha v beta 3 integrins. J Biol Chem 2003; 278:34605-16. [PMID: 12807887 DOI: 10.1074/jbc.m303159200] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fibrillins are the major glycoprotein components of microfibrils that form a template for tropoelastin during elastic fibrillogenesis. We have examined cell adhesion to assembled purified microfibrils, and its molecular basis. Human dermal fibroblasts exhibited Arg-Gly-Asp and cation-dependent adhesion to microfibrils and recombinant fibrillin-1 protein fragments. Strong integrin alpha 5 beta 1 interactions with fibrillin ligands were identified, but integrin alpha v beta 3 also contributed to cell adhesion. Fluorescence-activated cell sorting analysis confirmed the presence of abundant alpha 5 beta 1 and some alpha v beta 3 receptors on these cells. Adhesion to microfibrils and to Arg-Gly-Asp containing fibrillin-1 protein fragments induced signaling events that led to cell spreading, altered cytoskeletal organization, and enhanced extracellular fibrillin-1 deposition. Differences in cell shape when plated on fibrillin or fibronectin implied substrate-specific alpha 5 beta 1-mediated cellular responses. An Arg-Gly-Asp-independent cell adhesion sequence was also identified within fibrillin-1. Adhesion and spreading of smooth muscle cells on fibrillin ligands was enhanced by antibody-induced beta1 integrin activation. A375-SM melanoma cells bound Arg-Gly-Asp-containing fibrillin-1 protein fragments mainly through alpha v beta 3, whereas HT1080 cells used mainly alpha 5 beta 1. This study has shown that fibrillin microfibrils mediate cell adhesion, that alpha 5 beta 1 and alpha v beta 3 are both important but cell-specific fibrillin-1 receptors, and that cellular interactions with fibrillin-1 influence cell behavior.
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Affiliation(s)
- Daniel V Bax
- United Kingdom Centre for Tissue Engineering, School of Biological Sciences, University of Manchester, United Kingdom
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26
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Vehviläinen P, Hyytiäinen M, Keski-Oja J. Latent transforming growth factor-beta-binding protein 2 is an adhesion protein for melanoma cells. J Biol Chem 2003; 278:24705-13. [PMID: 12716902 DOI: 10.1074/jbc.m212953200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Of the four latent transforming growth factor (TGF)-beta-binding proteins (LTBPs), LTBP-2 is different in the respect that it does not bind small latent forms of TGF-beta. LTBP-2 is therefore likely to have other roles in the extracellular matrix. LTBP-2 contains an RGD putative integrin recognition site, suggesting a role in cell adhesion. We carried out a study on cell attachment to LTBP-2. Purified recombinant LTBP-2 was used as substratum in cell adhesion and migration studies. We found that, unlike most adherent cell lines, all of the melanoma cell lines tested adhered to LTBP-2 very efficiently and in a concentration-dependent manner. Bowes melanoma cells bound most efficiently to LTBP-2 and were used for further characterization. Cell adhesion assays with recombinant LTBP-2 fragments indicated that the adhesive site is located in an N-terminal region of LTBP-2. The attachment of melanoma cells to LTBP-2 was prevented with monoclonal antibody against beta1 integrin in a concentration-dependent manner, suggesting an important role for beta1 integrin in the process. Antibodies against integrin subunits alpha3 and alpha6 decreased melanoma cell adhesion as well. The beta1 and alpha3 integrins were localized on the cell surface, especially in lamellipodia, as observed by immunofluorescence. In addition to integrin antagonists, heparin also markedly decreased melanoma cell adhesion. LTBP-2 also supported Bowes cell migration in modified Boyden chamber assays in a manner similar to the migration on fibronectin. Current data indicate that LTBP-2 can play a role in melanoma cell adhesion.
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Affiliation(s)
- Piia Vehviläinen
- Department of Pathology, Haartman Institute, University of Helsinki, Finland
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27
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Samuel CS, Sakai LY, Amento EP. Relaxin regulates fibrillin 2, but not fibrillin 1, mRNA and protein expression by human dermal fibroblasts and murine fetal skin. Arch Biochem Biophys 2003; 411:47-55. [PMID: 12590922 DOI: 10.1016/s0003-9861(02)00710-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Relaxin modulates connective tissue remodeling by altering matrix molecule expression. We have found that relaxin specifically inhibits a microfibril component, fibrillin 2 (FBN2), without affecting fibrillin 1 (FBN1). Human dermal fibroblasts (HDFs) grown or stimulated to overexpress fibrillin expression were used to show that relaxin specifically down-regulated FBN2 mRNA and protein levels. Continuous exposure of HDFs to relaxin (30ng/ml) significantly (P<0.05) decreased fibrillin 2 protein (40%) while FBN1 protein expression was unchanged. Our in vitro studies were confirmed using relaxin null mice whereby the absence of relaxin was associated with increased FBN2 mRNA and protein in fetal skin from pregnant relaxin knockout mice. The regulation of FBN2 expression may be associated with functional changes in elastic tissues during development and growth.
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Affiliation(s)
- Chrishan S Samuel
- Molecular Medicine Research Institute, 525 Del Rey Avenue, Suite B, Sunnyvale, CA 94085, USA.
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28
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Spessotto P, Cervi M, Mucignat MT, Mungiguerra G, Sartoretto I, Doliana R, Colombatti A. beta 1 Integrin-dependent cell adhesion to EMILIN-1 is mediated by the gC1q domain. J Biol Chem 2003; 278:6160-7. [PMID: 12456677 DOI: 10.1074/jbc.m208322200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
EMILIN-1 (Elastin Microfibril Interface Located ProteIN), the prototype of the EMILIN family, consists of a cysteine-rich domain (EMI domain) at the N terminus, an extended region with a high potential coiled-coil structure, a short collagenous stalk, and a self-interacting globular gC1q-l domain. EMILIN-1 is an adhesive extracellular matrix constituent associated with elastic fibers, detected also in the proximity of cell surfaces. To localize the cell attachment site(s), monoclonal antibodies (mAbs) against EMILIN-1 or the gC1q-1 domain were used to inhibit cell attachment to EMILIN-1. Thus, one mAb mapping to the gC1q-1 domain caused complete inhibition of cell attachment. EMILIN-1 and gC1q-1 displayed a comparable dose-dependent ability to promote cell adhesion. Adhesion kinetics was similar to that of fibronectin (FN), reaching the maximum level of attachment at 20 min, but in the absence of cations adhesion was negligible. The relative adhesion strength to detach 50% of the cells was similar for EMILIN-1 and gC1q-1 (250-270 x g) but lower than that for FN (>>500). Cell adhesion to EMILIN-1 or gC1q-1 was completely blocked by a function-blocking beta(1) integrin subunit mAb. In contrast, adhesion to the complement C1q component was totally unaffected. Among the various function-blocking mAbs against the alpha integrin subunits only the anti-alpha(4) fully abrogated cell adhesion to gC1q-1 and up to 70% to EMILIN-1. Furthermore, only K562 cells transfected with the alpha(4) integrin chain, but not wild type K562, were able to adhere to EMILIN-1 and were specifically inhibited by anti-alpha(4) function-blocking mAb. Finally, cells attached to EMILIN-1 or gC1q-1, compared with cells plated on FN or vitronectin, which appeared well spread out on the substrate with prominent stress fibers and focal contacts, were much smaller with wide ruffles and a different organization status of the actin cytoskeleton along the cell periphery. This pattern was in accord with the ability of EMILIN-1 to promote cell movement.
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Affiliation(s)
- Paola Spessotto
- Divisione di Oncologia Sperimentale 2, Centro di Riferimento Oncologico, Aviano, Italy
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29
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Tiedemann K, Bätge B, Müller PK, Reinhardt DP. Interactions of fibrillin-1 with heparin/heparan sulfate, implications for microfibrillar assembly. J Biol Chem 2001; 276:36035-42. [PMID: 11461921 DOI: 10.1074/jbc.m104985200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fibrillin-1 is a major constituent of the 10-12 nm extracellular microfibrils. Here we identify, characterize, and localize heparin/heparan sulfate-binding sites in fibrillin-1 and report on the role of such glycosaminoglycans in the assembly of fibrillin-1. By using different binding assays, we localize two calcium-independent heparin-binding sites to the N-terminal (Arg(45)-Thr(450)) and C-terminal (Asp(1528)-Arg(2731)) domains of fibrillin-1. A calcium-dependent-binding site was localized to the central (Asp(1028)-Thr(1486)) region of fibrillin-1. Heparin binding to these sites can be inhibited by a highly sulfated and iduronated form of heparan sulfate but not by chondroitin 4-sulfate, chondroitin 6-sulfate, and dermatan sulfate, demonstrating that the heparin binding regions represent binding domains for heparan sulfate. When heparin or heparan sulfate was added to cultures of skin fibroblasts, the assembly of fibrillin-1 into a microfibrillar network was significantly reduced. Western blot analysis demonstrated that this effect was not due to a reduced amount of fibrillin-1 secreted into the culture medium. Inhibition of the attachment of glycosaminoglycans to core proteins of proteoglycans by beta-d-xylosides resulted in a significant reduction of the fibrillin-1 network. These studies suggest that binding of fibrillin-1 to proteoglycan-associated heparan sulfate chains is an important step in the assembly of microfibrils.
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Affiliation(s)
- K Tiedemann
- Universität zu Lübeck, Institut für Medizinische Molekularbiologie, Ratzeburger Allee 160, D-23538 Lübeck, Germany
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30
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Bunton TE, Biery NJ, Myers L, Gayraud B, Ramirez F, Dietz HC. Phenotypic alteration of vascular smooth muscle cells precedes elastolysis in a mouse model of Marfan syndrome. Circ Res 2001; 88:37-43. [PMID: 11139471 DOI: 10.1161/01.res.88.1.37] [Citation(s) in RCA: 227] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Marfan syndrome is associated with early death due to aortic aneurysm. The condition is caused by mutations in the gene (FBN1) encoding fibrillin-1, a major constituent of extracellular microfibrils. Prior observations suggested that a deficiency of microfibrils causes failure of elastic fiber assembly during late fetal development. Mice homozygous for a targeted hypomorphic allele (mgR) of Fbn1 revealed a predictable sequence of abnormalities in the vessel wall including elastic fiber calcification, excessive deposition of matrix elements, elastolysis, and intimal hyperplasia. Here we describe previously unrecognized concordant findings in elastic vessels from patients with Marfan syndrome. Furthermore, ultrastructural analysis of mgR mice revealed cellular events that initiate destructive changes. The first detectable abnormality was an unusually smooth surface of elastic laminae, manifesting the loss of cell attachments that are normally mediated by fibrillin-1. Adjacent cells adopted alteration in their expression profile accompanied by morphological changes but retained expression of vascular smooth muscle cell markers. The abnormal synthetic repertoire of these morphologically abnormal smooth muscle cells in early vascular lesions included elastin, among other matrix elements, and matrix metalloproteinase 9, a known mediator of elastolysis. Ultimately, cell processes associated with zones of elastic fiber thinning and fragmentation. These data suggest that the loss of cell attachments signals a nonproductive program to synthesize and remodel an elastic matrix. This refined understanding of the pathogenesis of vascular disease in Marfan syndrome will facilitate the development of therapeutic strategies.
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MESH Headings
- Actins/analysis
- Adolescent
- Adult
- Animals
- Aorta/metabolism
- Aorta/pathology
- Aorta/ultrastructure
- Disease Models, Animal
- Elastic Tissue/pathology
- Fibrillin-1
- Fibrillins
- Humans
- Immunohistochemistry
- In Situ Hybridization
- Marfan Syndrome/metabolism
- Marfan Syndrome/pathology
- Matrix Metalloproteinase 9/analysis
- Mice
- Mice, Knockout
- Microfibrils/metabolism
- Microfilament Proteins/deficiency
- Microfilament Proteins/genetics
- Microscopy, Electron
- Middle Aged
- Muscle, Smooth, Vascular/chemistry
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Phenotype
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Tropoelastin/genetics
- Tropoelastin/metabolism
- Vimentin/analysis
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Affiliation(s)
- T E Bunton
- Department of Comparative Medicine, Institute for Genetic Medicine, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Md, USA
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31
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Dietz HC, Mecham RP. Mouse models of genetic diseases resulting from mutations in elastic fiber proteins. Matrix Biol 2000; 19:481-8. [PMID: 11068202 DOI: 10.1016/s0945-053x(00)00101-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The inability to study appropriate human tissues at various stages of development has precluded the elaboration of a thorough understanding of the pathogenic mechanisms leading to diseases linked to mutations in genes for elastic fiber proteins. Recently, new insights have been gained by studying mice harboring targeted mutations in the genes that encode fibrillin-1 and elastin. These genes have been linked to Marfan syndrome (MFS) and supravalvular aortic stenosis (SVAS), respectively. For fibrillin-1, mouse models have revealed that phenotype is determined by the degree of functional impairment. The haploinsufficiency state or the expression of low levels of a product with dominant-negative potential from one allele is associated with mild phenotypes with a predominance of skeletal features. Exuberant expression of a dominant-negative-acting protein leads to the more severe MFS phenotype. Mice harboring targeted deletion of the elastin gene (ELN) show many of the features of SVAS in humans, including abnormalities in the vascular wall and altered hemodynamics associated with changes in wall compliance. The genetically altered mice suggest that SVAS is predominantly a disease of haploinsufficiency. These studies have underscored the prominent role of the elastic matrix in the morphogenesis and homeostasis of the vessel wall.
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Affiliation(s)
- H C Dietz
- Departments of Pediatrics, Medicine, and Molecular Biology and Genetics, and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Ross 858, 720 Rutland Ave., Baltimore, MD 21205, USA.
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Saharinen J, Keski-Oja J. Specific sequence motif of 8-Cys repeats of TGF-beta binding proteins, LTBPs, creates a hydrophobic interaction surface for binding of small latent TGF-beta. Mol Biol Cell 2000; 11:2691-704. [PMID: 10930463 PMCID: PMC14949 DOI: 10.1091/mbc.11.8.2691] [Citation(s) in RCA: 220] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Transforming growth factor (TGF)-betas are secreted in large latent complexes consisting of TGF-beta, its N-terminal latency-associated peptide (LAP) propeptide, and latent TGF-beta binding protein (LTBP). LTBPs are required for secretion and subsequent deposition of TGF-beta into the extracellular matrix. TGF-beta1 associates with the 3(rd) 8-Cys repeat of LTBP-1 by LAP. All LTBPs, as well as fibrillins, contain multiple 8-Cys repeats. We analyzed the abilities of fibrillins and LTBPs to bind latent TGF-beta by their 8-Cys repeats. 8-Cys repeat was found to interact with TGF-beta1*LAP by direct cysteine bridging. LTBP-1 and LTBP-3 bound efficiently all TGF-beta isoforms, LTBP-4 had a much weaker binding capacity, whereas LTBP-2 as well as fibrillins -1 and -2 were negative. A short, specific TGF-beta binding motif was identified in the TGF-beta binding 8-Cys repeats. Deletion of this motif in the 3(rd) 8-Cys repeat of LTBP-1 resulted in loss of TGF-beta*LAP binding ability, while its inclusion in non-TGF-beta binding 3(rd) 8-Cys repeat of LTBP-2 resulted in TGF-beta binding. Molecular modeling of the 8-Cys repeats revealed a hydrophobic interaction surface and lack of three stabilizing hydrogen bonds introduced by the TGF-beta binding motif necessary for the formation of the TGF-beta*LAP - 8-Cys repeat complex inside the cells.
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Affiliation(s)
- J Saharinen
- Departments of Virology and Pathology, The Haartman Institute, University of Helsinki, Finland
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33
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Robinson PN, Godfrey M. The molecular genetics of Marfan syndrome and related microfibrillopathies. J Med Genet 2000; 37:9-25. [PMID: 10633129 PMCID: PMC1734449 DOI: 10.1136/jmg.37.1.9] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Mutations in the gene for fibrillin-1 (FBN1) have been shown to cause Marfan syndrome, an autosomal dominant disorder of connective tissue characterised by pleiotropic manifestations involving primarily the ocular, skeletal, and cardiovascular systems. Fibrillin-1 is a major component of the 10-12 nm microfibrils, which are thought to play a role in tropoelastin deposition and elastic fibre formation in addition to possessing an anchoring function in some tissues. Fibrillin-1 mutations have also been found in patients who do not fulfil clinical criteria for the diagnosis of Marfan syndrome, but have related disorders of connective tissue, such as isolated ectopia lentis, familial aortic aneurysm, and Marfan-like skeletal abnormalities, so that Marfan syndrome may be regarded as one of a range of type 1 fibrillinopathies. There appear to be no particular hot spots since mutations are found throughout the entire fibrillin-1 gene. However, a clustering of mutations associated with the most severe form of Marfan syndrome, neonatal Marfan syndrome, has been noted in a region encompassing exons 24 to 32. The gene for fibrillin-2 (FBN2) is highly homologous to FBN1, and mutations in FBN2 have been shown to cause a phenotypically related disorder termed congenital contractural arachnodactyly. Since mutations in the fibrillin genes are likely to affect the global function of the microfibrils, the term microfibrillopathy may be the most appropriate to designate the spectrum of disease associated with dysfunction of these molecules. The understanding of the global and the molecular functions of the fibrillin containing microfibrils is still incomplete and, correspondingly, no comprehensive theory of the pathogenesis of Marfan syndrome has emerged to date. Many, but not all, fibrillin-1 gene mutations are expected to exert a dominant negative effect, whereby mutant fibrillin monomers impair the global function of the microfibrils. In this paper we review the molecular physiology and pathophysiology of Marfan syndrome and related microfibrillopathies.
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Affiliation(s)
- P N Robinson
- Laboratory of Paediatric Molecular Biology, Department of General Paediatrics, Charité University Hospital, Humboldt University, D-10098 Berlin, Germany
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Saharinen J, Hyytiäinen M, Taipale J, Keski-Oja J. Latent transforming growth factor-beta binding proteins (LTBPs)--structural extracellular matrix proteins for targeting TGF-beta action. Cytokine Growth Factor Rev 1999; 10:99-117. [PMID: 10743502 DOI: 10.1016/s1359-6101(99)00010-6] [Citation(s) in RCA: 215] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Growth factors of the transforming growth factor-beta family are potent regulators of the extracellular matrix formation, in addition to their immunomodulatory and regulatory roles for cell growth. TGF-beta s are secreted from cells as latent complexes containing TGF-beta and its propeptide, LAP (latency-associated peptide). In most cells LAP is covalently linked to an additional protein, latent TGF-beta binding protein (LTBP), forming the large latent complex. LTBPs are required for efficient secretion and correct folding of TGF-beta s. The secreted large latent complexes associate covalently with the extracellular matrix via the N-termini of the LTBPs. LTBPs belong to the fibrillin-LTBP family of extracellular matrix proteins, which have a typical repeated domain structure consisting mostly of epidermal growth factor (EGF)-like repeats and characteristic eight cysteine (8-Cys) repeats. Currently four different LTBPs and two fibrillins have been identified. LTBPs contain multiple proteinase sensitive sites, providing means to solubilize the large latent complex from the extracellular matrix structures. LTBPs are now known to exist both as soluble molecules and in association with the extracellular matrix. An important consequence of this is LTBP-mediated deposition and targeting of latent, activatable TGF-beta into extracellular matrices and connective tissues. LTBPs have a dual function, they are required both for the secretion of the small latent TGF-beta complex as well as directing bound latent TGF-beta to extracellular matrix microfibrils. However, it is not known at present whether LTBPs are capable of forming microfibrils independently, or whether they are a part of the fibrillin-containing fibrils. Most LTBPs possess RGD-sequences, which may have a role in their interactions with the cell surface. At least LTBP-1 is chemotactic to smooth muscle cells, and is involved in vascular remodelling. Analyses of the expressed LTBPs have revealed considerable variations throughout the molecules, generated both by alternative splicing and utilization of multiple promoter regions. The significance of this structural diversity is mostly unclear at present.
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Affiliation(s)
- J Saharinen
- Department of Virology, Haartman Institute, University of Helsinki, Finland
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Gibson MA, Leavesley DI, Ashman LK. Microfibril-associated glycoprotein-2 specifically interacts with a range of bovine and human cell types via alphaVbeta3 integrin. J Biol Chem 1999; 274:13060-5. [PMID: 10224057 DOI: 10.1074/jbc.274.19.13060] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microfibril-associated glycoprotein (MAGP)-1 and MAGP-2 are small structurally related glycoproteins that are specifically associated with fibrillin-containing microfibrils. MAGP-2, unlike MAGP-1, contains an RGD motif with potential for integrin binding. To determine if the RGD sequence is active, a series of cell binding assays was performed. MAGP-2 was shown to promote the attachment and spreading of bovine nuchal ligament fibroblasts when coated onto plastic wells in molar quantities similar to those of fibronectin. In contrast, approximately 10-fold more MAGP-1 was required to support comparable levels of cell adhesion. The fibroblast binding to MAGP-2 was completely inhibited if the peptide GRGDSP or the MAGP-2-specific peptide GVSGQRGDDVTTVTSET was added to the reaction medium at a 10 microM final concentration. The control peptide GRGESP had no effect on the interaction. These findings indicate that the cell interaction with MAGP-2 is an RGD-mediated event. A monoclonal antibody to human alphaVbeta3 integrin (LM609) almost completely blocked cell attachment to MAGP-2 when added to the medium at 0.5 microgram/ml, whereas two monoclonal antibodies specific for the human beta1 integrin subunit, 4B4 (blocking) and QE2.E5 (activating), had no effect even at 10 microgram/ml. Fetal bovine aortic smooth muscle cells, ear cartilage chondrocytes, and arterial endothelial cells and human skin fibroblasts and osteoblasts were also observed to adhere strongly to MAGP-2. In addition, each cell type was able to spread on MAGP-2 substrate, with the exception of the endothelial cells, which remained spherical after 2 h of incubation. The binding of each cell type was blocked when the anti-alphaVbeta3 integrin antibody was included in the assay, indicating that alphaVbeta3 integrin is the major receptor for MAGP-2 on several cell types. Thus, MAGP-2 may mediate interactions between fibrillin-containing microfibrils and cell surfaces during the development of a variety of tissues.
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Affiliation(s)
- M A Gibson
- Department of Pathology, University of Adelaide, Adelaide, South Australia 5005.
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Raghunath M, Putnam EA, Ritty T, Hamstra D, Park ES, Tschödrich-Rotter M, Peters R, Rehemtulla A, Milewicz DM. Carboxy-terminal conversion of profibrillin to fibrillin at a basic site by PACE/furin-like activity required for incorporation in the matrix. J Cell Sci 1999; 112 ( Pt 7):1093-100. [PMID: 10198291 DOI: 10.1242/jcs.112.7.1093] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fibrillin-1, the main component of 10–12 nm microfibrils of the extracellular matrix, is synthesized as profibrillin and proteolytically processed to fibrillin. The putative cleavage site has been mapped to the carboxy-terminal domain of profibrillin-1, between amino acids arginine 2731 and serine 2732, by a spontaneous mutation in this recognition site that prevents profibrillin conversion. This site contains a basic amino acid recognition sequence (R-G-R-K-R-R) for proprotein convertases of the furin/PACE family. In this study, we use a mini-profibrillin protein to confirm the cleavage in the carboxy-terminal domain by both fibroblasts and recombinantly expressed furin/PACE, PACE4, PC1/3 and PC2. Site-directed mutagenesis of amino acids in the consensus recognition motif prevented conversion, thereby identifying the scissile bond and characterizing the basic amino acids required for cleavage. Using a PACE/furin inhibitor, we show that wild-type profibrillin is not incorporated into the extracellular matrix until it is converted to fibrillin. Therefore, profibrillin-1 is the first extracellular matrix protein to be shown to be a substrate for subtilisin-like proteases, and the conversion of profibrillin to fibrillin controls microfibrillogenesis through exclusion of uncleaved profibrillin.
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Affiliation(s)
- M Raghunath
- Department of Physiological Chemistry and Pathobiochemistry and of Medical Physics and Biophysics, University of Münster, Münster, Germany
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