Expression of NG2 proteoglycan causes retention of type VI collagen on the cell surface.

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Abstract
NG2 is a membrane-associated chondroitin sulfate proteoglycan with a core protein of 300 kD. Previously it was shown immunochemically that the core protein of NG2 can bind type VI collagen (Stallcup, W., Dahlin, K., and P. Healy. 1990. J. Cell Biol. 111:3177-3188). We have extended our studies on the interaction of NG2 and type VI collagen by transfecting cells with the full-length rat NG2 cDNA. B28 rat neural cells and U251MG human glioma cells used for transfection do not synthesize NG2. Both cell lines secrete type VI collagen into tissue culture medium but do not anchor it at the cell surface. Upon transfection of these cells with the NG2 cDNA, NG2 was correctly localized to the cell surface. Furthermore, type VI collagen could now be detected on the surface of NG2-positive cells in a pattern that coincided with that of NG2. This ability of NG2 to anchor type VI collagen to the cell surface could be abolished by incubating the cells in the presence of anti-NG2 monoclonal antibodies. These findings indicate that NG2 functions as a cell surface receptor for type VI collagen and may play a role in modulating the assembly of pericellular matrix.