Changes in rapidly transported proteins in the auditory nerve after hair cell loss

In an effort to further characterize the proteins of the auditory nerve, the effects of hair cell loss on rapidly transported proteins of the auditory nerve were studied. The effects were studied in the waltzing guinea pig, a genetically deaf animal which displays an age-dependent loss of sensory cells, and in normal guinea pigs treated with neomycin. In both cases hair cell loss is followed by a slow degeneration of spiral ganglion cells and corresponding auditory nerve fibers. Rapidly transported proteins in the cochlear nucleus were analyzed by two dimensional electrofocusing/electrophoresis 3 h after cochlear injection of [35S]methionine. In both the waltzing guinea pig and the neomycin-treated animals, a significant increase in labeling of two series of polypeptides (average molecular weights of 27,000 and 36,000 daltons) was apparent. Quantitation of the 36,000 dalton protein by extracting from dried gels showed a 2-fold increase in the 10-day-old waltzing guinea pig and a 6-fold increase in the 80-day-old waltzing guinea pig. Further analysis shows these proteins to be membrane-associated glycoproteins.