Possible role of myelin-associated neuraminidase in membrane adhesion.

Previous studies from our laboratory have demonstrated the presence of a specific interaction between myelin-associated neuraminidase and GM1 (Saito and Yu, J Neurochem 47:632-641, 1986). In the present study, we further characterized this neuraminidase-GM1 interaction and examined its role in the adhesion of rat oligodendroglial cells to GM1. Hydrolysis of N-acetylneuramin-lactitol by the enzyme was inhibited by GM1 in a competitive manner; GM1 itself was not hydrolyzed, suggesting that GM1 may serve as a competitive inhibitor of the enzyme. Asialo-GM1 had no inhibitory effect. When a soluble enzyme preparation was applied to a GM1-linked affinity column, the enzyme activity was retained on the column and was recovered from the column only by elution with a buffer containing 5 mM 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (Neu2en5Ac), a competitive inhibitor of neuraminidase. A binding study with 51Cr-labeled rat oligodendroglial cells showed that oligodendroglial cells bound preferentially to GM1 developed on a thin-layer plate, but not to other gangliosides such as GM3, GD1a, GD1b, and GT1b. The binding reaction to GM1 was inhibited by Neu2en5Ac (5 mM). These results suggest that myelin-associated neuraminidase specifically interacts with GM1 and may be involved in adhesion of oligodendroglial cells to GM1. This neuraminidase-GM1 interaction may play an important role in the formation and stabilization of the multilamellar structure of the myelin sheath.