Microtubule disruption and Dictyostelium cell motility: Effects on random migration and chemotaxis

Abstract

To obtain insights into the roles of microtubules in cell motility and chemotaxis, we have treated randomly migrating or chemotactically responding Dictyostelium cells with nocodazole, a microtubule-disrupting reagent, and analyzed their motility and shape changes from time-lapse phase-contrast microscope images. Nocodazole treatments at 50 μM for 30 minutes, which sufficiently disrupted dynamic microtubules, made the speed of cell migration significantly faster (120%) as well as induced more frequent cell shape changes. That is, the cells became less polarized and generated pseudopods more frequently. Therefore, microtubules might be a negative regulator of pseudopod formation, and may thus play a role in establishing and/or maintaining the cell polarity by suppressing multiple pseudopod generation. With regard to chemotaxis, the nocodazole treated cells showed normal chemotactic migration, and their additional pseudopod formation was suppressed normally compared to control cells in a steep gradient of chemoattractant cAMP. Thus, strong chemoattractant signals seems to be able to compensate for the lack of dynamic microtubules. The nocodazole treatment did not affect the multicellular morphogenesis during the development of the cellular slime mold. On the other hand, in a shallower gradient, the cells showed slight but significant decreases in chemotactic efficiency. Although microtubules are dispensable in steep gradients of cAMP, they may play a role in increasing the efficiency of chemotaxis in shallow gradients.