Possible role of myelin‐associated neuraminidase in membrane adhesion

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Abstract
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 51 Cr‐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.

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