Axonal Transport of Newly Synthesized Glycoproteins in a Single Identified Neuron of Aplysia Californica

Increasing amounts of glycoprotein synthesized from L-[(3)H]fucose injected into the cell body of R2, an identified Aplysia neuron, were found in the right pleuro-abdominal connective. Autoradiography revealed that the glycoproteins were localized in the axon of R2. Glycoproteins appearing in the axon presumably were synthesized in the cell body, since no significant incorporation was observed when [(3)H]fucose was injected directly into the axon. [(3)H]glycoproteins were detected in the connective after a delay of 1 h after intrasomatic injection. Thereafter, transport from the cell body was rapid, and by 10 h after injection, 45% of the total neuronal [(3)H]glycoprotein had appeared in the axon. By analysing the radioactivity in cell body and connective 4, 10, and 15 h after injection, we found that [(3)H]glycoproteins were transported selectively compared to nonmacromolecular material. Sequential sectioning of the connective revealed that [(3)H]glycoproteins were transported in discrete waves. The population of membrane-associated [(3)H]glycoproteins in the axon differed from that in the cell body. Two of the five somatic components appeared to be transported preferentially. In addition a new component appeared in the axon 10 h after injection.