Taxol impairs anterograde axonal transport of microinjected horseradish peroxidase in dorsal root ganglia neurons in vitro.

We have investigated the effects of taxol on the axonal transport of horseradish peroxidase (HRP) in dorsal root ganglia (DRG) cells and their neuronal cytoskeleton. The former were analysed by microinjection of HRP into single DRG cells and the latter was studied by means of immunohistochemistry and cryo-electron microscopy. In cultured and untreated DRG cells, microinjected HRP was typically transported anterogradely several hundred micrometres along their neurites. Different exposure periods (1, 2 and 3 days) to taxol were analysed. The axonal transport of HRP in DRG cells was time-dependently impeded by taxol. After the drug had been washed out, a recovery of the axonal transport of HRP was observed and confirmed by quantitative analysis. Cryo-electron microscopy revealed an abnormal aggregation of axonal and cytoplasmic microtubules, associated with a decreased amount of cross-linking structures, in taxol-treated DRG cell cultures. After 3 days of taxol exposure, microtubule-associated proteins and Tau-protein were restricted to the cellular somata but the neurofilament network and tubulin-proteins seemed to be unaffected. Our results demonstrate, for the first time, an inhibition of anterograde axonal transport of HRP in single neurons by taxol. This effect is reversible and seems not to be caused by cellular damage, but is rather a consequence of an altered organisation of microtubules and/or microtubule-associated proteins.