THE INTERACTIONS OF NON-AGGREGATING PROTEOGLYCANS

The small proteoglycans decorin, biglycan and fibromodulin were prepar ed as a mixture from bovine nasal cartilage. The proteoglycans in this mixture were shown to interact with hyaluronate immobilized on Sephar ose beads under isotonic conditions. The interaction could be disrupte d by increasing the ionic strength of the solvent by enhancing the con centration of NaCl. To further characterize the proteoglycans of this mixture, they were visualized with the glycerol spraying/rotary shadow ing technique for electron microscopy. They were shown to have a globu lar core protein and one or more glycosaminoglycan chains. The molecul es, moreover, were organized as multimeric complexes, and their associ ation one with another appeared to be mediated by either core protein or glycosaminoglycan chain interactions. Complexes were shown by rotar y shadowing microscopy to associate with hyaluronate in solution. The combined results of this study show that as a mixture, the small prote oglycans of cartilage can interact with hyaluronate, though not necess arily as discrete monomers but rather as multimeric complexes. The obs ervations made in this study also suggest that a similar interaction c ould occur in vivo, where the interaction between small proteoglycans and hyaluronate may have a functional significance in the maintenance of cartilage homeostasis.