Type IX Collagen Interacts with Fibronectin Providing an Important Molecular Bridge in Articular Cartilage

Type IX collagen is covalently bound to the surface of type II collagen fibrils within the cartilage extracellular matrix. The N-terminal, globular noncollagenous domain (NC4) of the α1(IX) chain protrudes away from the surface of the fibrils into the surrounding matrix and is available for molecula...

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Bibliographic Details
Published in:The Journal of biological chemistry 2011-10, Vol.286 (40), p.34986-34997
Main Authors: Parsons, Philippa, Gilbert, Sophie J., Vaughan-Thomas, Anne, Sorrell, David A., Notman, Rebecca, Bishop, Mark, Hayes, Anthony J., Mason, Deborah J., Duance, Victor C.
Format: Article
Language:English
Subjects:
Animals
Articular Cartilage
Cartilage - metabolism
Cartilage, Articular - metabolism
Cell Line
Chondrocytes - metabolism
Collagen
Collagen Type IX - metabolism
Connective Tissue
DNA, Complementary - metabolism
Extracellular Matrix
Fibronectin
Fibronectins - metabolism
Glycobiology and Extracellular Matrices
Humans
Kinetics
Mice
NC4
Polymerase Chain Reaction
Protein Interaction Mapping
Protein Structure, Tertiary
Protein-Protein Interactions
Recombinant Proteins - chemistry
Two-Hybrid System Techniques
Type IX Collagen
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Summary:Type IX collagen is covalently bound to the surface of type II collagen fibrils within the cartilage extracellular matrix. The N-terminal, globular noncollagenous domain (NC4) of the α1(IX) chain protrudes away from the surface of the fibrils into the surrounding matrix and is available for molecular interactions. To define these interactions, we used the NC4 domain in a yeast two-hybrid screen of a human chondrocyte cDNA library. 73% of the interacting clones encoded fibronectin. The interaction was confirmed using in vitro immunoprecipitation and was further characterized by surface plasmon resonance. Using whole and pepsin-derived preparations of type IX collagen, the interaction was shown to be specific for the NC4 domain with no interaction with the triple helical collagenous domains. The interaction was shown to be of high affinity with nanomolar Kd values. Analysis of the fibronectin-interacting clones indicates that the constant domain is the likely site of interaction. Type IX collagen and fibronectin were shown to co-localize in cartilage. This novel interaction between the NC4 domain of type IX collagen and fibronectin may represent an in vivo interaction in cartilage that could contribute to the matrix integrity of the tissue.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M111.238188