RAPID TRANSPORT OF FUCOSYL GLYCOPROTEINS TO NERVE ENDINGS IN MOUSE BRAIN

Abstract— Mice were injected intracerebrally with mixtures of ³H]fucose and ¹⁴C]gluco-samine, and incorporation into macromolecules in various subcellular fractions of brain was studied at 1, 2, 3 and 4 h after administration of the precursors. There was a lag of several hours between the incorporation of ³H]fucose into the glycoproteins of the whole brain fractions and of that into the soluble and particulate glycoproteins of the nerve ending fractions. In contrast, no lag was observed between the incorporation of ¹⁴C]glucosamine into the macromolecules of the whole brain fractions and of that into the soluble macro-molecules of the nerve ending fraction. We conclude that fucosyl glycoproteins of the nerve ending fraction were synthesized in the nerve cell bodies and transported to nerve endings by rapid axoplasmic transport, whereas a substantial proportion of the glucosamine in the soluble macromolecules of the nerve ending fraction was incorporated by the nerve endings themselves. In addition, our evidence indicates that cyclobeximide inhibited fucose incorporation into brain glycoproteins by inhibiting the synthesis of acceptor proteins rather than fucosyl transferase.