IMMUNOCYTOCHEMICAL COMPARISON OF POSTTRANSLATIONALLY MODIFIED FORMS OF TUBULIN IN THE VESTIBULAR END-ORGANS OF THE GERBIL - TYROSINATED, ACETYLATED AND POLYGLUTAMYLATED TUBULIN

Specific antibodies against alpha-tubulin, acetylated alpha-tubulin, t yrosinated alpha-tubulin and polyglutamylated alpha- and beta-tubulin were used to compare the distribution of posttranslationally modified tubulin in the vestibular end-organs of the gerbil. Antibodies to acet ylated tubulin labeled a dense network of microtubules in the hair cel ls and bundles of microtubule in the supporting cells. Nerve fibers wi thin and below the epithelium were weakly labeled. This localization p aralleled that seen with antibodies to cu-tubulin which labeled all mi crotubules present in the cells. Antibodies to tyrosinated tubulin lab eled networks and bundles of microtubules in both hair cells and suppo rting cells and in addition gave intense, diffuse labeling in the cyto plasm of both cell types. It also labeled the nerve fibers. Antibodies to polyglutamylated tubulin were localized mainly in nerve fibers, an d in the calyces the labeled microtubules were found running circumfer entially around the type I sensory hair cells. Thus, tyrosinated tubul in was found in the fine networks of microtubules in both the sensory and supporting cells. Acetylated tubulin was found in the dense networ ks and bundles of microtubules in the sensory and supporting cells, bu t did not colocalize with polyglutamylated tubulin, which was found pr edominantly in the nerve fibers. The labeling patterns for the tyrosin ated tubulin and posttranslationally modified tubulins in the sensory and supporting cells of the vestibular end organs differ from that see n in the organ of Corti and may reflect differences in the stability o f the microtubules and the mechanical properties of the sensory epithe lium.