Interactions between fibronectin, glycosaminoglycans and native collagen fibrils: an EM study in artificial three-dimensional extracellular matrices.
The interactions between plasma fibronectin (FN), glycosaminoglycans (GAGs) and native collagen (COL) fibrils were studied in artificial three-dimensional extracellular matrices. FN-COL binding was investigated using rotary shadowed platinum-carbon replicas, EM immunocytochemistry and FN-gold complexes. GAGs were visualized using cationic dyes and anti-GAG antibodies. The specificity of the reactions was evaluated with dot blots. FN showed a low affinity for the surface of native COL fibrils. In contrast, it attached extensively to incompletely/irregularly polymerized COL. Where associated with native fibrils, FN showed preferential affinity for the dark cross-striations, particularly with the a and b bands. Like FN, GAGs bound mostly to the zones of incomplete/irregular COL polymerization. However, they also extensively decorated native fibrils, particularly over the dark cross-striations The d band in the gap zone was not a preferential binding site for either FN or GAGs. The pattern of FN-COL fibril binding was not influenced by GAGs. Dot blots confirmed that, under physiological conditions, FN shows no significant affinity for GAGs other than heparin. However, it does bind to all GAGs in low salt conditions. Results suggest that some of the roles ascribed to FN-COL interactions, particularly structural ones, must be reevaluated.
Cidadão
A J
AJ
Department of Cell Biology, Gulbenkian Institute of Science, Oeiras/Portugal.
D003094:Collagen / Q000378:metabolism* / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000166:cytology*; D005353:Fibronectins / Q000378:metabolism* / Q000648:ultrastructure; D006025:Glycosaminoglycans / Q000378:metabolism*; D066298:In Vitro Techniques; D008854:Microscopy, Electron
D005353:Fibronectins; D006025:Glycosaminoglycans; D003094:Collagen