Lis1 restricts the conformational changes in cytoplasmic dynein on microtubules.

Cytoplasmic dynein is a microtubule-based motor protein that transports intracellular cargo and performs various functions during cell division. We previously reported that Lis1 suppressed dynein motility on microtubules in an idling state. Recently, a model showed that Lis1 prevents the ATPase domain of dynein from transmitting a detachment signal to its microtubule-binding domain. However, conformational information on dynein is limited. We used electron microscopy to investigate the conformation of dynein and nucleotide-induced conformational changes on microtubules. The conformation of dynein differed depending on the presence or absence of a nucleotide. In the presence of the nucleotide ADP-vanadate, dynein displayed an extended form on microtubules (extended form), whereas in the absence of a nucleotide, dynein lay along microtubules (compact form). This conformational change reflects chemomechanical coupling in dynein walking on microtubules. We also found that Lis1 fixed the conformation of dynein in the compact form regardless of the nucleotide condition. Removal of the Lis1 dimerization motif abolished Lis1-dependent fixation of dynein in the compact form. This suggests that the idling state of dynein on microtubules induced by Lis1 occurs through the Lis1-dependent arrest of dynein chemomechanical coupling.

Kinesin-1 regulates dendrite microtubule polarity in Caenorhabditis elegans.

In neurons, microtubules (MTs) span the length of both axons and dendrites, and the molecular motors use these intracellular 'highways' to transport diverse cargo to the appropriate subcellular locations. Whereas axonal MTs are organized such that the plus-end is oriented out from the cell body, dendrites exhibit a mixed MTs polarity containing both minus-end-out and plus-end-out MTs. The molecular mechanisms underlying this differential organization, as well as its functional significance, are unknown. Here, we show that kinesin-1 is critical in establishing the characteristic minus-end-out MT organization of the dendrite in vivo. In unc-116 (kinesin-1/kinesin heavy chain) mutants, the dendritic MTs adopt an axonal-like plus-end-out organization. Kinesin-1 protein is able to cross-link anti-paralleled MTs in vitro. We propose that kinesin-1 regulates the dendrite MT polarity through directly gliding the plus-end-out MTs out of the dendrite using both the motor domain and the C-terminal MT-binding domain. DOI:http://dx.doi.org/10.7554/eLife.00133.001.