The interactions of 'non-aggregating' proteoglycans.

The small proteoglycans decorin, biglycan and fibromodulin were prepared as a mixture from bovine nasal cartilage. The proteoglycans in this mixture were shown to interact with hyaluronate immobilized on Sepharose beads under isotonic conditions. The interaction could be disrupted by increasing the ionic strength of the solvent by enhancing the concentration of NaCl. To further characterize the proteoglycans of this mixture, they were visualized with the glycerol spraying/rotary shadowing technique for electron microscopy. They were shown to have a globular core protein and one or more glycosaminoglycan chains. The molecules, moreover, were organized as multimeric complexes, and their association one with another appeared to be mediated by either core protein or glycosaminoglycan chain interactions. Complexes were shown by rotary shadowing microscopy to associate with hyaluronate in solution. The combined results necessarily as discrete monomers but rather as multimeric complexes. The observations made in this study also suggest that a similar interaction could occur in vivo, where the interaction between small proteoglycans and hyaluronate may have a functional significance in the maintenance of cartilage homeostasis.