UNUSUAL DISTRIBUTION OF TUBULIN ISOFORMS IN THE SNAIL LYMNAEA-STAGNALIS

Immunocytochemistry and Western blotting techniques demonstrated that the nervous system and foot of the pond snail Lymnaea stagnalis are ri ch sources of tubulin, which can be extracted and assembled in vitro i n the presence of taxol. Various broad-spectrum antibodies raised agai nst alpha-tubulin and beta-tubulin yielded qualitatively similar resul ts. One monoclonal antibody to trypanosome alpha-tubulin, however, lab elled alpha-tubulin more strongly on both probed sections and Western blots. Cytochemistry and immunoblotting revealed that tyrosinated tubu lin constitutes a large proportion of total alpha-tubulin in locomotor cilia of the foot and in axons of the nervous system. Detyrosinated t ubulin also appeared to be abundant in the foot cilia but only a very faint band of detyrosinated tubulin was found on protein blots extract ed from the central ganglia, and staining was barely detectable in cen tral ganglia or peripheral nerves. Similarly, acetylated tubulin appea red to be abundant in foot cilia, but Western blotting indicated only low levels of acetylated tubulin in the nervous system. Immunocytochem istry indicated that, while most neurons possessed little or no acetyl ated tubulin, a small number of axons contained significant amounts of this isoform. Thus, while a large amount of tubulin was expected in t he nervous system and locomotor cilia of L. stagnalis, the observed di stribution of isoforms was unanticipated. Specifically, neurons of oth er organisms have generally been reported to contain substantial amoun ts of both detyrosinated alpha-tubulin and acetylated alpha-tubulin. O ur results indicate that such findings cannot be generalized across al l species. L. stagnalis, with its well studied nervous system and unus ual distribution of tubulin isoforms, may prove to be particularly use ful for studying the roles of tubulin isoforms in microtubule function and cell activity.