Interactions between chondroitin sulfate proteoglycan, fibronectin, and collagen

A proteoglycan isolated from a rat yolk sac tumor and characterized as a chondroitin sulfate proteoglycan with a smaller amount of dermatan sulfate was studied with respect to complex formation with collagen and fibronectin. The proteoglycan co-precipitated with native collagen from neutral salt solutions at 6 degrees C and 37 degrees C. Addition of fibronectin in such precipitation mixtures resulted in incorporation of fibronectin to the precipitate. Treatment of the proteoglycan with alkali to separate the glycosaminoglycan chains from the protein part and digestion of the protein part with papain greatly reduced the capacity of the proteoglycan to precipitate collagen and fibronectin. A defined extracellular matrix as represented by the complexes of collagen, proteoglycan, and fibronectin constructed here may be useful for studies on the biological effects of extracellular matrices. The multiple interactions of matrix macromolecules exemplified by these results may play a role in the formation of extracellular matrices and in the maintenance of their integrity.