A CENTRAL SEGMENT OF THE NG2 PROTEOGLYCAN IS CRITICAL FOR THE ABILITYOF GLIOMA-CELLS TO BIND AND MIGRATE TOWARD TYPE-VI COLLAGEN

Previous studies have established that the NG2 proteoglycan binds dire ctly to type VI collagen. To further our understanding of the biochemi cal and functional significance of this interaction we have used NG2 c DNA to construct a series of NG2 mutants with relations spaced through out, the entire length of the 260-kDa NG2 core protein. Following tran sfection of these mutant cDNAs into B28 glioma cells, we determined th e ability of mutant NG2 molecules to anchor type Vl collagen on the ce ll surface, Eight of 11 transfectant populations were able to anchor t ype VI. collagen. The three NG2 variants incapable of anchoring type V I collagen have deletions clustered within the central one-third of th e NG2 ectodomain, These deletions identify a 469-amino-acid domain of NG2 responsible for binding of type VI collagen, Functional consequenc es of the NG2-type VI collagen interaction were explored by testing th e relative ability of NG2-transfected and untransfected glioma cells t o migrate toward type VI collagen. NG2-expressing cells exhibited a gr eater migratory response toward type VI collagen than their NG2-negati ve counterparts. This enhanced migration could be specifically inhibit ed with NG2 antibodies. Furthermore, glioma cells expressing NG2 in wh ich the collagen-binding domain was deleted failed to exhibit this enh anced migration, whereas NG2 mutants in which non-collagen-binding, re gions were deleted continued to exhibit increased chemotaxis toward th e type VI collagen, These comparisons confirm the importance of the ce ntral collagen-binding domain in mediating functionally important inte ractions between NG2 and type VI collagen. (C) 1997 Academic Press.