Possible role of myelin‐associated neuraminidase in membrane adhesion

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 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.

Visualization of Sialidase Activity in Mammalian Tissues and Cancer Detection with a Novel Fluorescent Sialidase Substrate

“…After washing with ACSF, white matter showed intense fluorescence in the slices stained with BTP2-Neu5Ac, BTP3-Neu5Ac and BTP4-Neu5Ac (Figure 4 A–C). This result was consistent with results of the previous studies showing that white matter of the mammalian brain exhibits intense sialidase activity using 4MU-Neu5Ac or X-Neu5Ac with FRV LB [8], [17].…”

Structure, function and metabolism of sialic acids

“…The enzymes occur in higher animals of the deuterostomate lineage that possess the corresponding sialic acid-containing substrates as components of an autonomous sialic acid metabolism. However, they have also been found in a variety of microorganisms, such as viruses, bacteria and protozoa [13,59]. Some of the latter organisms do not contain or produce sialic acid themselves.…”

Distribution of Sialidase Activity and the Role of Sialidase in the Brain

“…The sialidase is tightly bound to myelin membranes and cleaves sialic acid from glycoproteins and gangliosides including GM3, GD1a and GT1b (24,(26)(27)(28). The enzyme activity of myelin sialidase toward N-acetylneuramin(α2→3)lactiol exhibits a very broad pH dependency with optimal pH of 4.1 (24).…”

“…The myelin sialidase specifically interacts with GM1. It has been suggested that oligodendroglia cells bound preferentially to GM1 via the myelin sialidase (26). The myelin-associated sialidase would play an important role in the formation and maintenance of the myelin sheath and catabolism of sialoglycoconjugates in myelin and oligodendroglia cells.…”