Different Polypeptides Are Rapidly Transported in Auditory and Optic Neurons

Abstract
Rapidly transported proteins and glycoproteins in the auditory and optic nerves of the guinea pig were analyzed by electrophoresis and 2-dimensional electrofocusing/electrophoresis. Proteins transported in the auditory nerve were analyzed in the cochlear nucleus 3 h after cochlear injection of radioactive precursor. Proteins transported in the optic nerve were analyzed in the superior colliculus 6 h after intraocular injection of radioactive precursor. Two-dimensional analysis showed that several rapidly transported polypeptides were present in one system, but not in the other. By use of [3H]fucose as a precursor or by separating [35S]methionine-labeled polypeptides on immobilized concanavalin A or wheat germ agglutinin, it was shown that most of the proteins transported in only one system are glycoproteins. A polypeptide of MW 140,000 was a major labeled species in the auditory nerve. This polypeptide was also found in the optic nerve, but only as a minor species. Two other polypeptides with MW and isoelectric points similar to those of the 140,000 MW polypeptide were present in both systems, but were much more abundant in the optic nerve. The major labeled polypeptide in both systems had a MW of 25,000.