Fibromodulin Interacts with Collagen Cross-linking Sites and Activates Lysyl Oxidase (original) (raw)
Related papers
International Journal of Experimental Pathology, 2002
The Spring meeting of the BCTS was held at University Hall, Cardiff University on 30-31st March, and had as its theme molecular interaction and matrix assembly. About 170 delegates, from all around the UK, registered for the meeting. In order to promote and increase international collaborations and interactions, speakers were invited from laboratories in the USA, Germany, Belgium, and Australia, and, also from the biomedical industries in the UK.
Fibromodulin Binds Collagen Type I via Glu-353 and Lys-355 in Leucine-rich Repeat 11
Journal of Biological Chemistry, 2007
Fibromodulin belongs to the small leucine-rich repeat proteoglycan family, interacts with collagen type I, and controls collagen fibrillogenesis and assembly. Here, we show that a major fibromodulin-binding site for collagen type I is located in leucine-rich repeat 11 in the C terminus of the leucine-rich repeat domain. We identified Glu-353 and Lys-355 in repeat 11 as essential for binding, and the synthetic peptide RLDGNEIKR, including Glu-353 and Lys-355, inhibits the binding of fibromodulin to collagen in vitro. Fibromodulin and lumican compete for the same binding region on collagen, and fibromodulin can inhibit the binding of lumican to collagen type I. However, the peptide RLDGNEIKR does not inhibit the binding of lumican to collagen, suggesting separate but closely situated fibromodulin-and lumican-binding sites in collagen. The collagenbinding Glu-353 and Lys-355 residues in fibromodulin are exposed on the exterior of the -sheet-loop structure of the leucine-rich repeat, which resembles the location of interacting residues in other leucine-rich repeat proteins, e.g. decorin. . 2 The abbreviations used are: SLRP, small leucine-rich repeat proteoglycan; LRR, leucine-rich repeat; GST, glutathione S-transferase; PBS, phosphatebuffered saline; BSA, bovine serum albumin; ITC, isothermal titration calorimetry.
Journal of Biological Chemistry, 2009
Lumican and fibromodulin compete for collagen type I binding in vitro and fibromodulin-deficient mice have fourfold more lumican in tendons. These observations indicate that homologous sequences in lumican and fibromodulin bind to collagen type I. Here, we demonstrate that lumican binding to collagen type I is mediated mainly by Asp-213 in LRR 7. The mutation D213N in lumican impairs interaction with collagen, and the lumican fragment spanning LRRs 5-7 is an efficient inhibitor of collagen binding. Also, the lumican LRR 7 sequence-based synthetic peptide CYLDNNKC inhibits the binding to collagen. Homologous collagen-binding site in fibromodulin, located in LRRs 5-7, inhibits the binding of lumican to collagen, and the mutation E251Q in this fibromodulin fragment does not inhibit the lumican-collagen binding. Lumican, but not the the D213N mutation, lowers the melting point and affects the packing of collagen fibrils.
Journal of Biological Chemistry, 1999
Fibromodulin is a member of a family of connective tissue glycoproteins/proteoglycans containing leucinerich repeat motifs. Several members of this gene family bind to fibrillar collagens and are believed to function in the assembly of the collagen network in connective tissues. Here we show that mice lacking a functional fibromodulin gene exhibit an altered morphological phenotype in tail tendon with fewer and abnormal collagen fiber bundles. In fibromodulin-null animals virtually all collagen fiber bundles are disorganized and have an abnormal morphology. Also 10-20% of the bundles in heterozygous mice are similar to the abnormal bundles in fibromodulin-null tail tendon. Ultrastructural analysis of Achilles tendon from fibromodulin-null mice show collagen fibrils with irregular and rough outlines in cross-section. Morphometric analysis show that fibromodulin-null mice have on the average thinner fibrils than wild type animals as a result of a larger preponderance of very thin fibrils in an overall similar range of fibril diameters. Protein and RNA analyses show an approximately 4-fold increase in the content of lumican in fibromodulin-null as compared with wild type tail tendon, despite a decrease in lumican mRNA. These results demonstrate a role for fibromodulin in collagen fibrillogenesis and suggest that the orchestrated action of several leucine-rich repeat glycoproteins/proteoglycans influence the architecture of collagen matrices.
Proceedings of The National Academy of Sciences, 2008
We describe the molecular structure of the collagen fibril and how it affects collagen proteolysis or ''collagenolysis.'' The fibrilforming collagens are major components of all mammalian connective tissues, providing the structural and organizational framework for skin, blood vessels, bone, tendon, and other tissues. The triple helix of the collagen molecule is resistant to most proteinases, and the matrix metalloproteinases that do proteolyze collagen are affected by the architecture of collagen fibrils, which are notably more resistant to collagenolysis than lone collagen monomers. Until now, there has been no molecular explanation for this. Full or limited proteolysis of the collagen fibril is known to be a key process in normal growth, development, repair, and cell differentiation, and in cancerous tumor progression and heart disease. Peptide fragments generated by collagenolysis, and the conformation of exposed sites on the fibril as a result of limited proteolysis, regulate these processes and that of cellular attachment, but it is not known how or why. Using computational and molecular visualization methods, we found that the arrangement of collagen monomers in the fibril (its architecture) protects areas vulnerable to collagenolysis and strictly governs the process. This in turn affects the accessibility of a cell interaction site located near the cleavage region. Our observations suggest that the C-terminal telopeptide must be proteolyzed before collagenase can gain access to the cleavage site. Collagenase then binds to the substrate's ''interaction domain,'' which facilitates the triplehelix unwinding/dissociation function of the enzyme before collagenolysis.
Increased c-telopeptide cross-linking of tendon type i collagen in fibromodulin-deficient mice
2014
Collagen cross-linking mechanisms must be regulated to obtain tissue-specific collagen fiber properties. Results: Deficiency in collagen-associated protein fibromodulin leads to excessively cross-linked specific domain of collagen. Conclusion: Fibromodulin modulates site-specific cross-linking of collagen. Significance: This is the first report showing that a collagen-associated protein can modulate cross-linking of specific collagen domains.
Molecular basis for governing the morphology of type-I collagen fibrils by Osteomodulin
Communications Biology
Small leucine-rich repeat proteoglycan (SLRP) proteins have an important role in the organization of the extracellular matrix, especially in the formation of collagen fibrils. However, the mechanism governing the shape of collagen fibrils is poorly understood. Here, we report that the protein Osteomodulin (OMD) of the SLRP family is a monomeric protein in solution that interacts with type-I collagen. This interaction is dominated by weak electrostatic forces employing negatively charged residues of OMD, in particular Glu284 and Glu303, and controlled by entropic factors. The protein OMD establishes a fast-binding equilibrium with collagen, where OMD may engage not only with individual collagen molecules, but also with the growing fibrils. This weak electrostatic interaction is carefully balanced so it modulates the shape of the fibrils without compromising their viability.
A matricellular protein fibulin-4 is essential for the activation of lysyl oxidase
Science Advances
Fibulin-4 is a matricellular protein required for extracellular matrix (ECM) assembly. Mice deficient in fibulin-4 (Fbln4−/−) have disrupted collagen and elastin fibers and die shortly after birth from aortic and diaphragmatic rupture. The function of fibulin-4 in ECM assembly, however, remains elusive. Here, we show that fibulin-4 is required for the activity of lysyl oxidase (LOX), a copper-containing enzyme that catalyzes the covalent cross-linking of elastin and collagen. LOX produced by Fbln4−/− cells had lower activity than LOX produced by wild-type cells due to the absence of lysine tyrosyl quinone (LTQ), a unique cofactor required for LOX activity. Our studies showed that fibulin-4 is required for copper ion transfer from the copper transporter ATP7A to LOX in the trans-Golgi network (TGN), which is a necessary step for LTQ formation. These results uncover a pivotal role for fibulin-4 in the activation of LOX and, hence, in ECM assembly.