ISOLATION OF A TENASCIN-R BINDING-PROTEIN FROM MOUSE-BRAIN MEMBRANES - A PHOSPHACAN-RELATED CHONDROITIN SULFATE PROTEOGLYCAN

We have isolated a chondroitin sulfate proteoglycan from mouse brain b y affinity chromatography with a fragment of the extracellular matrix glycoprotein tenascin-a (TN-R) that comprises the amino-terminal cyste ine-rich stretch and the 4.5 epidermal growth factor-like repeats. The isolated chondroitin sulfate proteoglycan has a molecular mass of 500 -600 kDa and carries the HNK-1 carbohydrate epitope. Treatment with ch ondroitinase ABC reveals a major band of approximately 400 kDa and two minor bands at 200 and 150 kDa. Immunoblot analysis relates the molec ule to phosphacan but not to the chondroitin sulfate proteoglycans neu rocan and versican. Binding of the phosphacan-related molecule to the epidermal growth factor-like repeats of TN-R is Ca2+-dependent. Co-loc alization of the molecule with TN-R in the retina and optic nerve by i mmunocytochemistry suggests a functional relationship between the two molecules in vivo. Inhibition of neurite outgrowth from hippocampal ne urons by the phosphacan-related molecule in vitro is neutralized by TN -R when coated as a uniform substrate. Furthermore, the phosphacan-rel ated molecule neutralizes growth cone repulsion induced by TN-R coated as a sharp substrate boundary with or without prior treatment with ch ondroitinase ABC. These observations indicate that TN-R can interact w ith a phosphacan-related molecule and thereby modulate its inhibitory influence on neuritogenesis.