To characterize the domain localization, quantitation, and functional binding consequences of an O linked oligosaccharide expressed on synovial fluid (SF) fibronectin (Fn).
Identification and localization of the O linked oligosaccharide was performed by limited digestion of isolated SF Fn with a series of proteolytic enzymes followed by Western blotting with peroxidase labeled peanut agglutinin. Binding affinity to denatured collagen was performed utilizing a solid phase gelatin-binding assay. Quantitation was performed by measuring purified Fn in an antibody-lectin sandwich binding assay.
A desialyated O linked oligosaccharide was identified on the C-terminal 18 kDa segment of the SF Fn collagen-binding domain. These SF collagen-binding Fn fragments were more basic and had higher gelatin-binding affinities than corresponding plasma fibronectin fragments. Expression of this O linked oligosaccharide was highest on Fn isolated from osteoarthritic SF, followed by Fn isolated from rheumatoid arthritis SF, and finally normal human plasma.
Fn isolated from SF have glycosylation alterations that may influence their biologic properties in the diseased joint.