| 1. |
- Häger, Mattias, et al.
(författare)
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Cib2 binds integrin a7Bb1D and is reduced in laminin a2 chain deficient muscular dystrophy
- 2008
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 283:36, s. 24760-24769
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Tidskriftsartikel (refereegranskat)abstract
- Mutations in the gene encoding laminin alpha 2 chain cause congenital muscular dystrophy type 1A. In skeletal muscle, laminin alpha 2 chain binds at least two receptor complexes: the dystrophin-glycoprotein complex and integrin alpha 7 beta 1. To gain insight into the molecular mechanisms underlying this disorder, we performed gene expression profiling of laminin alpha 2 chain-deficient mouse limb muscle. One of the down-regulated genes encodes a protein called Cib2 (calcium-and integrin-binding protein 2) whose expression and function is unknown. However, the closely related Cib1 has been reported to bind integrin alpha IIb and may be involved in outside-in-signaling in platelets. Since Cib2 might be a novel integrin alpha 7 beta 1-binding protein in muscle, we have studied Cib2 expression in the developing and adult mouse. Cib2 mRNA is mainly expressed in the developing central nervous system and in developing and adult skeletal muscle. In skeletal muscle, Cib2 colocalizes with the integrin alpha 7B subunit at the sarcolemma and at the neuromuscular and myotendinous junctions. Finally, we demonstrate that Cib2 is a calcium-binding protein that interacts with integrin alpha 7B beta 1D. Thus, our data suggest a role for Cib2 as a cytoplasmic effector of integrin alpha 7B beta 1D signaling in skeletal muscle.
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| 2. |
- Kalamajski, Sebastian, et al.
(författare)
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Asporin competes with decorin for collagen binding, binds calcium and promotes osteoblast collagen mineralization
- 2009
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Ingår i: Biochemical Journal. - 0264-6021. ; 423, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- The interactions of the ECM (extracellular matrix) protein asporin with ECM components have previously not been investigated. Here, we show that asporin binds collagen type I. This binding is inhibited by recombinant asporin fragment LRR (leucine-rich repeat) 10-12 and by full-length decorin, but not by biglycan. We demonstrate that the polyaspartate domain binds calcium and regulates hydroxyapatite formation in vitro. In the presence of asporin, the number of collagen nodules, and mRNA of osteoblastic markers Osterix and Runx2 were increased. Moreover, decorin or the collagen-binding asporin fragment LRR 10-12 inhibited the pro-osteoblastic activity of full-length asporin. Our results suggest that asporin and decorin compete for binding to collagen and that the polyaspartate in asporin directly regulates collagen mineralization. Therefore asporin has a role in osteoblast-driven collagen biomineralization activity. We also show that asporin can be expressed in Escherichia coli (Rosettagami (TM)) with correctly positioned cysteine bridges, and a similar system can possibly be used for the expression of other SLRPs (small LRR proteoglycans/proteins).
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| 3. |
- Kalamajski, Sebastian, et al.
(författare)
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Fibromodulin binds collagen type I via Glu-353 and Lys-355 in leucine-rich repeat 11
- 2007
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 282:37, s. 26740-26745
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Tidskriftsartikel (refereegranskat)abstract
- 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 collagen-binding Glu-353 and Lys-355 residues in fibromodulin are exposed on the exterior of the beta-sheet-loop structure of the leucine-rich repeat, which resembles the location of interacting residues in other leucine-rich repeat proteins, e. g. decorin.
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| 4. |
- Kalamajski, Sebastian
(författare)
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Functions of small leucine-rich repeat proteoglycans in connective tissues
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological properties of connective tissues rely heavily on collagen and its use in formation of extracellular networks (matrices) in which cells can live and move. To regulate the process of collagen matrix assembly, the cells secrete small leucine-rich repeat proteoglycans (SLRPs) that bind to collagen and influence its fibril formation. In this manner, fibromodulin - one of the SLRPs - can alter intermolecular cross-linking of collagen, which has long-term implications for the structural integrity of the connective tissue. Since SLRPs can bind to collagen in via different domains, and are expressed in different tissues, their regulation of collagen matrices is fine-tuned for the physiological requirements. For example, decorin and lumican interact with collagen using their central leucine-rich repeat domains, while fibromodulin makes use of its C-terminal domain. In addition, some SLRPs can inhibit each other's binding to collagen. These differences, together with the detailed knowledge on matrix protein interactions, can be useful to explain the development of connective tissues. In a longer time perspective, this knowledge could allow to manipulate fibrotic processes in pathological conditions like cancer or atherosclerosis - the two major causes of death in our society. The potential for such intervention is high, since fibromodulin is abundant in cancer stroma, raising its interstitial fluid pressure that hinders an efficient anti-cancer drug medication. Furthermore, fibromodulin is expressed in atherosclerotic plaques, regulating the growth of the fibrous cap and activity of smooth muscle cells. These observations validate further investigations into this field of connective tissue biology.
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| 5. |
- Kalamajski, Sebastian, et al.
(författare)
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Homologous sequence in lumican and fibromodulin LRR 5-7 competes for collagen binding.
- 2009
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 284:1, s. 534-539
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Tidskriftsartikel (refereegranskat)abstract
- Lumican and fibromodulin compete for collagen type I binding in vitro and fibromodulin-deficient mice have four-fold 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.
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| 6. |
- Kalamajski, Sebastian, et al.
(författare)
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The decorin sequence SYIRIADTNIT binds collagen type I.
- 2007
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 282:22, s. 16062-16067
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Tidskriftsartikel (refereegranskat)abstract
- Decorin belongs to the small leucine-rich repeat proteoglycan family, interacts with fibrillar collagens, and regulates the assembly, structure, and biomechanical properties of connective tissues. The decorin-collagen type I-binding region is located in leucine-rich repeats 5–6. Site-directed mutagenesis of this 54-residue-long collagen-binding sequence identifies Arg-207 and Asp-210 in leucine-rich repeat 6 as crucial for the binding to collagen. The synthetic peptide SYIRIADTNIT, which includes Arg-207 and Asp-210, inhibits the binding of full-length recombinant decorin to collagen in vitro. These collagen-binding amino acids are exposed on the exterior of the beta-sheet-loop structure of the leucine-rich repeat. This resembles the location of interacting residues in other leucine-rich repeat proteins.
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| 7. |
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| 8. |
- Lidén, Åsa, et al.
(författare)
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A fibronectin-binding protein from Streptococcus equi binds collagen and modulates cell-mediated collagen gel contraction
- 2006
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 340:2, s. 604-610
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Tidskriftsartikel (refereegranskat)abstract
- The N-terminal fragment (FNZN) of the fibronectin-binding protein FNZ from Streptococcus equi subspecies zooepidemicus was investigated as to effects on murine cell interactions with extracellular matrix proteins. FNZN bound to immobilized fibronectin (FN) and native, but not denatured, collagen type I. FNZN had no effect on primary adhesion of cells from the murine myoblastic C2C12 cell line to immobilized fibronectin. C2C12 cells adhered to immobilized FNZN, a process that was not inhibited by anti-human FN IgG or by an inhibitor of integrin alphaVbeta3. C2C12 cells lack collagen-binding beta1 integrins and neither adhere to native collagen nor mediate contraction of three-dimensional collagen gels. FNZN stimulated collagen gel contraction by C2C12 cells but not adhesion of C2C12 cells to collagen. Experiments with an alphaVbeta3-inhibitor suggested that FNZN promoted contraction by a process requiring alphaVbeta3. Our data suggest that FNZN by binding to cells, collagen, and FN modulate complex adhesive processes mediated by the alphaVbeta3 integrin. Since alphaVbeta3-mediated contractile events function to counteract edema formation during inflammation, it is possible that FNZN and its secreted homologue FNE modulate edema responses in infected tissues.
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| 9. |
- Maccarana, Marco, et al.
(författare)
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Dermatan Sulfate Epimerase 1-Deficient Mice have Reduced Content and Changed Distribution of Iduronic acids in Dermatan Sulfate and an Altered Collagen Structure in Skin.
- 2009
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Ingår i: Molecular and Cellular Biology. - 0270-7306. ; 29, s. 5517-5528
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Tidskriftsartikel (refereegranskat)abstract
- Dermatan sulfate epimerase 1 (DS-epi1) and 2 convert glucuronic acid to iduronic acid in chondroitin/dermatan sulfate biosynthesis. Here we report on the generation of DS-epi1-null mice and the resulting alterations in the chondroitin/dermatan polysaccharide chains. The numbers of long blocks of adjacent iduronic acids are greatly decreased in skin decorin and biglycan chondroitin/dermatan sulfate, along with a parallel decrease of iduronic-2-O-sulfated-galactosamine-4-O-sulfated structures. Both iduronic acid blocks and iduronic acids surrounded by glucuronic acids are also decreased in versican-derived chains. DS-epi1-deficient mice are smaller than wild-type littermates, but otherwise have no gross macroscopic alterations. The lack of DS-epi1 affects the chondroitin/dermatan sulfate in many proteoglycans and the consequences for skin collagen structure were initially analyzed. We found that the skin collagen architecture was altered, and electron microscopy showed that the DS-epi1-null fibrils have a larger diameter than the wild-type fibrils. The altered chondroitin/dermatan sulfate chains carried by decorin in skin are likely to affect the collagen fibril formation and reduce the tensile strength of DS-epi1-null skin.
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| 10. |
- Oldberg, Åke, et al.
(författare)
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Collagen-binding proteoglycan fibromodulin can determine stroma matrix structure and fluid balance in experimental carcinoma.
- 2007
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 104:35, s. 13966-13971
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Tidskriftsartikel (refereegranskat)abstract
- Research on the biology of the tumor stroma has the potential to lead to development of more effective treatment regimes enhancing the efficacy of drug-based treatment of solid malignancies. Tumor stroma is characterized by distorted blood vessels and activated connective tissue cells producing a collagen-rich matrix, which is accompanied by elevated interstitial fluid pressure (IFP), indicating a transport barrier between tumor tissue and blood. Here, we show that the collagen-binding proteoglycan fibromodulin controls stroma structure and fluid balance in experimental carcinoma. Gene ablation or inhibition of expression by anti-inflammatory agents showed that fibromodulin promoted the formation of a dense stroma and an elevated IFP. Fibromodulin-deficiency did not affect vasculature but increased the extracellular fluid volume and lowered IFP. Our data suggest that fibromodulin controls stroma matrix structure that in turn modulates fluid convection inside and out of the stroma. This finding is particularly important in relation to the demonstration that targeted modulations of the fluid balance in carcinoma can increase the response to cancer therapeutic agents.
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