Disruption of microtubules and retardation of development ofDictyostelium with ethylN-phenylcarbamate and thiabendazole

Summary

The effects of ethylN-phenylcarbamate (EPC) and thiabendazole (TB) onDictyostelium discoideum andD. mucoroides cells were examined as a step toward purifying tubulin and clarifying the function of microtubules in cellular slime molds. EPC (1.5 × 10⁻³M) or TB (5 × 10⁻⁵M) inhibited the development ofDictyostelium, inducing the formation of aberrant fruiting bodies with stalks irregular in shape and sori containing spores of various sizes and shapes.

EPC and TB inhibited cell division but not cell growth, resulting in the production of giant cells up to ten times larger than untreated cells. The giant cells either had a single huge nucleus of irregular shape or contained multiple nuclei. The effects of the inhibitors were reversible. After the removal of the inhibitors, the giant cells underwent successive cell divisions producing many daughter cells. Interestingly, most of the giant cells induced by EPC treatment contained gigantic secondary lysosomes probably produced by extensive lysosomophagy.

Light microscopy using Nomarski optics revealed that these inhibitors caused the round-up of the cells resulting in the inhibition of cell locomotion, whereas non-Brownian movement of the cytoplasmic granules was not affected. Indirect immunofluorescence using anti-α-tubulin revealed that networks of microtubules were apparently destroyed by the EPC or TB treatment.

These results show both EPC and TB are potent inhibitors of microtubules inDictyostelium and are effective tools for studying the function of microtubules either in cellular or multicellular organization throughout its life cycle.