Glycosaminoglycans show a specific periodic interaction with type I collagen fibrils

Raspanti, Mario; Viola, Manuela; Forlino, Antonella; Tenni, Ruggero; Gruppi, Cristian; Tira, Maria Enrica

doi:10.1016/j.jsb.2008.07.001

Cited by 96 publications

(70 citation statements)

References 40 publications

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“…Random areas of control fibers were imaged over different time intervals of incubation in cathepsin activity buffer at pH 5.5 for up to 20 h, which revealed no changes in the fiber structures and minor increases in diameters. Our results are similar to those of previously reported structural SEMbased collagen fibril studies (38,39). SDS-PAGE analysis of supernatants of fiber incubation mixtures did not show any Coomassie-positive fragments, indicating the intactness of the collagen fibers (see also Fig.…”

Section: Control Collagensupporting

confidence: 92%

Effects of Cysteine Proteases on the Structural and Mechanical Properties of Collagen Fibers

Panwar¹,

Du²,

Sharma³

et al. 2013

Journal of Biological Chemistry

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Background: Collagen macromolecules are biologically relevant substrates in tissue remodeling and bone-related diseases. Results: We investigated the action of cysteine proteases on the structural integrity and mechanical functionality of collagen fibers. Conclusion: Using ultrastructural and biochemical techniques, we present a model of collagen fiber degradation via cathepsin K. Significance: Our data provide new insights in matrix degradation and may allow new strategies to inhibit it.

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Section: Control Collagensupporting

confidence: 92%

Effects of Cysteine Proteases on the Structural and Mechanical Properties of Collagen Fibers

Panwar¹,

Du²,

Sharma³

et al. 2013

Journal of Biological Chemistry

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“…This rotation indicates that an extended GAG chain would run down the length of the tropocollagen, either twirling around it or crossing over to neighboring triple helices in the fibril. Both GAG binding modes have been demonstrated via biochemical means and by electron microscopy (23)(24)(25). The CatK dimer-GAG complex interaction with the collagen sheds light on a potential mechanism of collagen uncoiling and cleaving.…”

Section: Resultsmentioning

confidence: 96%

Structural basis of collagen fiber degradation by cathepsin K

Aguda¹,

Panwar²,

Du³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

127

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Cathepsin K is the major collagenolytic protease in bone that facilitates physiological as well as pathological bone degradation. Despite its key role in bone remodeling and for being a highly sought-after drug target for the treatment of osteoporosis, the mechanism of collagen fiber degradation by cathepsin K remained elusive. Here, we report the structure of a collagenolytically active cathepsin K protein dimer. Cathepsin K is organized into elongated C-shaped protease dimers that reveal a putative collagen-binding interface aided by glycosaminoglycans. Molecular modeling of collagen binding to the dimer indicates the participation of nonactive site amino acid residues, Q21 and Q92, in collagen unfolding. Mutations at these sites as well as perturbation of the dimer protein-protein interface completely inhibit cathepsin-K-mediated fiber degradation without affecting the hydrolysis of gelatin or synthetic peptide. Using scanning electron microscopy, we demonstrate the specific binding of cathepsin K at the edge of the fibrillar gap region of collagen fibers, which suggest initial cleavage events at the N-and C-terminal ends of tropocollagen molecules. Edman degradation analysis of collagen fiber degradation products revealed those initial cleavage sites. We propose that one cathepsin K molecule binds to collagen-bound glycosaminoglycans at the gap region and recruits a second protease molecule that provides an unfolding and cleavage mechanism for triple helical collagen. Removal of collagen-associated glycosaminoglycans prevents cathepsin K binding and subsequently fiber hydrolysis. Cathepsin K dimer and glycosaminoglycan binding sites represent novel targeting sites for the development of nonactive site-directed secondgeneration inhibitors of this important drug target.cathepsin K | collagen | glycosaminoglycan | enzyme mechanism

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“…The aberrant collagen fibrils due to uncontrolled lateral fusion were also observed for the tail tendon in decorin-deficient mice (28). An In vitro study suggested that decorin GAG chains without the core protein may simply bind to the collagen fibril surface and regulate ties between two or more collagen fibrils (29). Thus, lateral binding of collagen fibrils is a key function of decorin GAG chains.…”

Section: D Structure Of Glycosaminoglycan Chains In Tendonmentioning

confidence: 93%

Ring-Mesh Model of Proteoglycan Glycosaminoglycan Chains in Tendon based on Three-dimensional Reconstruction by Focused Ion Beam Scanning Electron Microscopy

Watanabe

Kametani

Koyama

et al. 2016

Journal of Biological Chemistry

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Tendons are composed of collagen fibrils and proteoglycan predominantly consisting of decorin. Decorin is located on the d-band of collagen fibrils, and its glycosaminoglycan (GAG) chains have been observed between collagen fibrils with transmission electron microscopy. GAG chains have been proposed to interact with each other or with collagen fibrils, but its threedimensional organization remains unclear. In this report, we used focused ion beam scanning electron microscopy to examine the three-dimensional organization of the GAG chain in the Achilles tendon of mature rats embedded in epoxy resin after staining with Cupromeronic blue, which specifically stains GAG chains. We used 250 serial back-scattered electron images of longitudinal sections with a 10-nm interval for reconstruction. Three-dimensional images revealed that GAG chains form a ring mesh-like structure with each ring surrounding a collagen fibril at the d-band and fusing with adjacent rings to form the planar network. This ring mesh model of GAG chains suggests that more than two GAG chains may interact with each other around collagen fibrils, which could provide new insights into the roles of GAG chains.Tendon is primarily composed of collagen fibrils and the non-collagen matrix (1). Canty et al. (2) suggested that plasma membrane protrusions called fibripositors contribute to the parallel arrangement of collagen fibrils in tendon, especially in the embryonic stage. Decorin and biglycan belong to the small leucine-rich proteoglycan family and consist of a core protein containing leucine repeats with a covalently attached chondroitin/dermatan sulfate glycosaminoglycan (GAG) 2 chain. The majority (Ͼ90%) of the tendon proteoglycan is decorin, while tendon also contains small amounts of biglycan (3). The decorin core protein binds to the surface of collagen fibrils by non-covalent binding and the attached decorin GAG chain extends from the core protein to associate closely with another decorin GAG chain on an adjacent fibril surface (4 -6).Some studies have suggested that the GAG chain forms bridges between collagen fibrils to guarantee mechanical integrity (4, 7-9). In contrast, other studies have suggested that the GAG chain is irrelevant to mechanical integrity (3, 10 -12), because results of mechanical tests using decorin-knock-out mice vary depending on the type and region of the tendon (13). Some researchers also reported that decorin might restore the alignment of the collagen fibrils deformed under load, rather than contribute to the transmission of forces (14,15). However, precise roles of decorin are not well understood, partly because its three-dimensional structure is unresolved.The structure of decorin GAG chains among collagen fibrils was observed by ultrathin sections of a sample stained with Cupromeronic blue and the critical electrolyte concentration technique, which was used to reveal the sulfated GAGs under a transmission electron microscope (TEM) (5, 16). Scott et al. (17) proposed the "shape module model" in which the decorin ...

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Glycosaminoglycans show a specific periodic interaction with type I collagen fibrils

Cited by 96 publications

References 40 publications

Effects of Cysteine Proteases on the Structural and Mechanical Properties of Collagen Fibers

Effects of Cysteine Proteases on the Structural and Mechanical Properties of Collagen Fibers

Structural basis of collagen fiber degradation by cathepsin K

Ring-Mesh Model of Proteoglycan Glycosaminoglycan Chains in Tendon based on Three-dimensional Reconstruction by Focused Ion Beam Scanning Electron Microscopy

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