Autotaxin is an N-linked glycoprotein but the sugar moieties are not needed for its stimulation of cellular motility.

ABSTRACT

Autotaxin is a 125kD autocrine motility factor that stimulates both random and directed motility in producing the human A2058 melanoma cell line. The recently cloned autotaxin has been demonstrated to bind strongly and specifically to concanavalin A (con A). In this study, we show that the oligosaccharide side chains on autotaxin are exclusively asparagine linked, since N-glycosidase F, but not neuraminidase or O-glycosidase, decreases the protein molecular mass to 100-105kD, which is the calculated molecular mass of the deduced autotaxin polypeptide. Furthermore, removal of oligosaccharide side chains by N-glycosidase F can be performed under mild conditions that retain motility-stimulating activity, suggesting that the oligosaccharide side chains are not necessary for autotaxin to activate its receptor. Finally, when melanoma cells are treated with inhibitors of carbohydrate processing, such as N-methyl-1-deoxynojirimycin, 1-deoxymannojirimycin and swainsonine, they still secrete a motility-stimulating autotaxin. Therefore, the carbohydrate side chains on autotaxin are not necessary to stimulate motility; however, they may still play a role in folding, secretion or maintenance of the active conformation of the protein.