scholarly journals Cooperative Accumulation of Dynein-Dynactin at Microtubule Minus-Ends Drives Microtubule Network Reorganization

2017 ◽  
Author(s):  
Ruensern Tan ◽  
Peter J. Foster ◽  
Daniel J. Needleman ◽  
Richard J. McKenney
Keyword(s):  
Mitotic Spindle ◽  
Large Scale ◽  
Spindle Assembly ◽  
Cytoplasmic Dynein ◽  
List Type ◽  
Microtubule Network ◽  
Cellular Processes ◽  
Dynein Motor ◽  
Mitotic Spindle Assembly ◽  
Orientation Bias

SummaryCytoplasmic 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.HighlightsProcessive 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.

scholarly journals Theory of cytoskeletal reorganization during crosslinker-mediated mitotic spindle assembly

2018 ◽  
Author(s):  
A. R. Lamson ◽  
C. J. Edelmaier ◽  
M. A. Glaser ◽  
M. D. Betterton
Keyword(s):  
Mitotic Spindle ◽  
Large Scale ◽  
Dynamic Instability ◽  
Kinetic Monte Carlo ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Balance Model ◽  
Cytoskeletal Reorganization ◽  
Bipolar Spindle ◽  
Mitotic Spindle Assembly

AbstractCells grow, move, and respond to outside stimuli by large-scale cytoskeletal reorganization. A prototypical example of cytoskeletal remodeling is mitotic spindle assembly, during which micro-tubules nucleate, undergo dynamic instability, bundle, and organize into a bipolar spindle. Key mechanisms of this process include regulated filament polymerization, crosslinking, and motor-protein activity. Remarkably, using passive crosslinkers, fission yeast can assemble a bipolar spindle in the absence of motor proteins. We develop a torque-balance model that describes this reorganization due to dynamic microtubule bundles, spindle-pole bodies, the nuclear envelope, and passive crosslinkers to predict spindle-assembly dynamics. We compare these results to those obtained with kinetic Monte Carlo-Brownian dynamics simulations, which include crosslinker-binding kinetics and other stochastic effects. Our results show that rapid crosslinker reorganization to microtubule overlaps facilitates crosslinker-driven spindle assembly, a testable prediction for future experiments. Combining these two modeling techniques, we illustrate a general method for studying cytoskeletal network reorganization.

scholarly journals A Complex of NuMA and Cytoplasmic Dynein Is Essential for Mitotic Spindle Assembly

Cell ◽  
1996 ◽  
Vol 87 (3) ◽  
pp. 447-458 ◽  
Author(s):  
Andreas Merdes ◽  
Kasra Ramyar ◽  
Janet D Vechio ◽  
Don W Cleveland
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Cytoplasmic Dynein ◽  
Mitotic Spindle Assembly

scholarly journals Ran-GTP is non-essential to activate NuMA for spindle pole focusing, but dynamically polarizes HURP to control mitotic spindle length

2018 ◽  
Author(s):  
Kenta Tsuchiya ◽  
Hisato Hayashi ◽  
Momoko Nishina ◽  
Masako Okumura ◽  
Yoshikatsu Sato ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Nucleocytoplasmic Transport ◽  
Spindle Pole ◽  
Human Cells ◽  
Fiber Formation ◽  
List Type ◽  
Mitotic Spindle Assembly ◽  
Ran Gtp ◽  
Dynamic Microtubule

AbstractDuring mitosis, a bipolar spindle is assembled around chromosomes to efficiently capture chromosomes. Previous work proposed that a chromosome-derived Ran-GTP gradient promotes spindle assembly around chromosomes by liberating spindle assembly factors (SAFs) from inhibitory importins. However, Ran’s dual functions in interphase nucleocytoplasmic transport and mitotic spindle assembly have made it difficult to assess its mitotic roles in somatic cells. Here, using auxin-inducible degron technology in human cells, we developed acute mitotic degradation assays to dissect Ran’s mitotic roles systematically and separately from its interphase function. In contrast to the prevailing model, we found that the Ran pathway is not essential for spindle assembly activities that occur at sites spatially separated from chromosomes, including activating NuMA for spindle pole focusing or for targeting TPX2. In contrast, Ran-GTP is required to localize HURP and HSET specifically at chromosome-proximal regions. We demonstrated that Ran-GTP and importin-β coordinately promote HURP’s dynamic microtubule binding-dissociation cycle near chromosomes, which results in stable kinetochore-fiber formation. Intriguingly, this pathway acts to establish proper spindle length preferentially during prometaphase, rather than metaphase. Together, we propose that the Ran pathway is required to activate SAFs specifically near chromosomes, but not generally during human mitotic spindle assembly. Ran-dependent spindle assembly is likely coupled with parallel pathways to activate SAFs, including NuMA, for spindle pole focusing away from chromosomes.HighlightsUsing auxin-inducible degron technology, we developed mitotic degradation assays for the Ran pathway in human cells.The Ran pathway is non-essential to activate NuMA for spindle pole focusing.The Ran pathway dynamically polarizes HURP and defines mitotic spindle length preferentially during prometaphase.Ran-GTP is required to activate SAFs specifically near chromosomes, but not generally, in human mitotic cells.

scholarly journals Novel insights into the mechanisms of mitotic spindle assembly by NEK kinases

2016 ◽  
Vol 3 (3) ◽  
pp. e1062952 ◽  
Author(s):  
Suzanna L. Prosser ◽  
Laura O'Regan ◽  
Andrew M. Fry
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Mitotic Spindle Assembly

scholarly journals Dynactin Is Required for Microtubule Anchoring at Centrosomes

1999 ◽  
Vol 147 (2) ◽  
pp. 321-334 ◽  
Author(s):  
N.J. Quintyne ◽  
S.R. Gill ◽  
D.M. Eckley ◽  
C.L. Crego ◽  
D.A. Compton ◽  
...  
Keyword(s):  
Mitotic Cell ◽  
Cytoplasmic Dynein ◽  
Microtubule Organization ◽  
Cultured Fibroblasts ◽  
Cell Extracts ◽  
Dynein Motor ◽  
Mitotic Spindle Assembly ◽  
Dynactin Complex

The multiprotein complex, dynactin, is an integral part of the cytoplasmic dynein motor and is required for dynein-based motility in vitro and in vivo. In living cells, perturbation of the dynein–dynactin interaction profoundly blocks mitotic spindle assembly, and inhibition or depletion of dynein or dynactin from meiotic or mitotic cell extracts prevents microtubules from focusing into spindles. In interphase cells, perturbation of the dynein–dynactin complex is correlated with an inhibition of ER-to-Golgi movement and reorganization of the Golgi apparatus and the endosome–lysosome system, but the effects on microtubule organization have not previously been defined. To explore this question, we overexpressed a variety of dynactin subunits in cultured fibroblasts. Subunits implicated in dynein binding have effects on both microtubule organization and centrosome integrity. Microtubules are reorganized into unfocused arrays. The pericentriolar components, γ tubulin and dynactin, are lost from centrosomes, but pericentrin localization persists. Microtubule nucleation from centrosomes proceeds relatively normally, but microtubules become disorganized soon thereafter. Overexpression of some, but not all, dynactin subunits also affects endomembrane localization. These data indicate that dynein and dynactin play important roles in microtubule organization at centrosomes in fibroblastic cells and provide new insights into dynactin–cargo interactions.

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