Abstract
Summary Cytoplasmic dynein-1 (dynein) is minus-end directed motor protein that transports cargo over long distances and organizes microtubules (MTs) during critical cellular processes such as mitotic spindle assembly. How dynein motor activity is harnessed for these diverse functions remains unknown. Here, we have uncovered a mechanism for how processive dynein-dynactin complexes drive MT-MT sliding, reorganization, and focusing, activities required for mitotic spindle assembly. We find that motors cooperatively accumulate, in limited numbers, at MT minus-ends. Minus-end accumulations drive MT-MT sliding, independent of MT orientation, and this activity always results in the clustering of MT minus-ends. At a mesoscale level, activated dynein-dynactin drives the formation and coalescence of MT asters. Macroscopically, dynein-dynactin activity leads to bulk contraction of millimeter-scale MT networks, demonstrating that minus-end accumulations produce network scale contractile stresses. Our data provides a model for how localized dynein activity is harnessed by cells to produce contractile stresses within the mitotic spindle.
Highlights
Processive dynein-dynactin complexes cooperatively form stable accumulations at MT minus-ends.
Minus-end accumulations of motors slide MTs without orientation bias, leading to minus-end focusing.
Minus-end accumulations of motors organize dynamic MTs into asters.
Minus-end accumulations of motors drive bulk contractions of large-scale MT networks.
