A fucose-specific lectin from Aleuria aurantia was used to study the dynamics of neuronal membrane glycoproteins. Albino rabbits received vitreal injections of affinity-purified 125I-Aleuria lectin. The radioactive probe was internalized by adsorptive endocytosis into retinal ganglion cells, and transported intact down to the nerve terminals in the contralateral geniculate bodies and superior colliculi. We found that the radiolabeled lectin was transported with at least two distinct rates (I, approximately 205 mm/day; II, approximately 45 mm/day) corresponding to the two rapid phases of anterograde transport of endogenous polypeptides described earlier in this system. This is the first evidence that an exogenous macromolecule may be transported along the axon at more than one velocity.
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