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Type‐X collagen interacts with the small leucine‐rich proteoglycans decorin and biglycan
Author(s) -
Hancock S.,
Kwan A.P.L.,
Duance V.C.
Publication year - 2004
Publication title -
international journal of experimental pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.671
H-Index - 72
eISSN - 1365-2613
pISSN - 0959-9673
DOI - 10.1111/j.0959-9673.2004.369bb.x
Subject(s) - biglycan , decorin , collagen, type i, alpha 1 , type ii collagen , cartilage , chemistry , type i collagen , versican , proteoglycan , extracellular matrix , aggrecan , chondroitin sulfate , biochemistry , glycosaminoglycan , microbiology and biotechnology , biology , anatomy , pathology , osteoarthritis , medicine , articular cartilage , alternative medicine , endocrinology
Type‐X collagen is expressed by hypertrophic chondrocytes in the epiphyseal growth plate. The 59‐kDa α‐chain consists of a 45‐kDa triple‐helical domain flanked by two noncollagenous regions, a large C‐terminal domain termed NC1 and a smaller N‐terminal domain termed NC2. The restricted distribution of type‐X collagen within the growth plate indicates a potential role during the process of endochondral ossification. Type‐X collagen may form a hexagonal lattice‐like matrix, permissive to vascular invasion and mineralization. Decorin and biglycan are small leucine‐rich proteoglycans, which are usually substituted with one or two glycosaminoglycan (GAG) chains, respectively. Their 40‐kDa protein cores contain N‐terminal GAG attachment site(s), several central leucine‐rich repeats and a disulphide‐bonded loop at the C‐terminal. They are ubiquitously expressed and are found in many connective tissues, including skin, cartilage and bone. They are known to interact with many proteins including fibrillar collagens. The molecular interactions of type‐X collagen with decorin and biglycan have been investigated in vitro . Characterizing these interactions may elucidate the precise role of these complexes in the hypertrophic cartilage matrix. Materials and methods To investigate the interactions of type‐X collagen with decorin and biglycan, solid phase assays, including competitive assays and surface plasmon resonance were used. Proteins used during the investigation included type‐X collagen purified from embryonic chick tibial hypertrophic chondrocytes, pepsin‐treated type‐X collagen, human recombinant NC1 domain of type‐X collagen, human recombinant decorin and biglycan purified from bovine cartilage. Results Type‐X collagen interacts with biglycan and decorin in solid phase assays and surface plasmon resonance, using the BIAcore 3000 system. The interactions occur primarily via the NC1 domain of type‐X collagen and are not dependent on the presence of the GAG chains on the proteoglycans. Dissociation constants have been calculated and indicate high affinity binding. Results from competitive binding assays indicate that decorin and biglycan bind to the same site on type‐X collagen. Rotary shadowing is currently being used to confirm interactions and to locate the interaction sites better. Discussion Interactions between type‐X collagen and other matrix components may be required for the assembly of the hypertrophic cartilage matrix and to maintain its integrity. Within the growth plate, type‐X collagen interactions with decorin and biglycan may have potential roles in regulation or maintenance of the type‐X collagen hexagonal network and/or presentation of growth factors, e.g. TGF‐β known to be important in endochondral ossification.