scholarly journals Theory of microtubule length regulation in antiparallel overlaps

2019 ◽  
Author(s):  
Hui-Shun Kuan ◽  
Meredith D. Betterton
Keyword(s):  
Steady State ◽  
Cell Division ◽  
Mitotic Spindle ◽  
Motor Proteins ◽  
Critical Concentration ◽  
Binding Kinetics ◽  
Kinesin Motor ◽  
Microtubule Polymerization ◽  
Length Regulation ◽  
Theory And Experiment

AbstractDuring cell division, microtubules in the mitotic spindle form antiparallel overlaps near the center of the spindle. Kinesin motor proteins alter microtubule polymerization dynamics to regulate the length of these overlaps to maintain spindle integrity. Length regulation of antiparallel overlaps has been reconstituted with purified microtubules, crosslinkers, and motors. Here we develop a theory of steady-state overlap length which depends on the filament plus-end motor concentration, determined by a balance between motor arrival (motor binding and stepping in the overlap) and motor departure (motor unbinding from filament tips during depolymerization) in the absence of motor-driven sliding. Assuming that motors processively depolymerize and exhibit altered binding kinetics near MT plus-ends improves the agreement between theory and experiment. Our theory explains the origin of the experimentally observed critical concentration, a minimum motor concentration to observe a steady-state overlap length.

scholarly journals TPX2 phosphorylation maintains metaphase spindle length by regulating microtubule flux

2015 ◽  
Vol 210 (3) ◽  
pp. 373-383 ◽  
Author(s):  
Jingyan Fu ◽  
Minglei Bian ◽  
Guangwei Xin ◽  
Zhaoxuan Deng ◽  
Jia Luo ◽  
...  
Keyword(s):  
Steady State ◽  
Mitotic Spindle ◽  
Microtubule Dynamics ◽  
Flux Rate ◽  
Aurora A ◽  
Null Mutant ◽  
Constant Length ◽  
Microtubule Polymerization ◽  
Spindle Microtubules

A steady-state metaphase spindle maintains constant length, although the microtubules undergo intensive dynamics. Tubulin dimers are incorporated at plus ends of spindle microtubules while they are removed from the minus ends, resulting in poleward movement. Such microtubule flux is regulated by the microtubule rescue factors CLASPs at kinetochores and depolymerizing protein Kif2a at the poles, along with other regulators of microtubule dynamics. How microtubule polymerization and depolymerization are coordinated remains unclear. Here we show that TPX2, a microtubule-bundling protein and activator of Aurora A, plays an important role. TPX2 was phosphorylated by Aurora A during mitosis. Its phospho-null mutant caused short metaphase spindles coupled with low microtubule flux rate. Interestingly, phosphorylation of TPX2 regulated its interaction with CLASP1 but not Kif2a. The effect of its mutant in shortening the spindle could be rescued by codepletion of CLASP1 and Kif2a that abolished microtubule flux. Together we propose that Aurora A–dependent TPX2 phosphorylation controls mitotic spindle length through regulating microtubule flux.

scholarly journals Roles of Polymerization Dynamics, Opposed Motors, and a Tensile Element in Governing the Length of Xenopus Extract Meiotic Spindles

2005 ◽  
Vol 16 (6) ◽  
pp. 3064-3076 ◽  
Author(s):  
T. J. Mitchison ◽  
P. Maddox ◽  
J. Gaetz ◽  
A. Groen ◽  
M. Shirasu ◽  
...  
Keyword(s):  
Steady State ◽  
Relative Stability ◽  
Motor Proteins ◽  
Microtubule Dynamics ◽  
Microtubule Polymerization ◽  
Hexylene Glycol ◽  
Meiotic Spindles

Metaphase spindles assemble to a steady state in length by mechanisms that involve microtubule dynamics and motor proteins, but they are incompletely understood. We found that Xenopus extract spindles recapitulate the length of egg meiosis II spindles, by using mechanisms intrinsic to the spindle. To probe these mechanisms, we perturbed microtubule polymerization dynamics and opposed motor proteins and measured effects on spindle morphology and dynamics. Microtubules were stabilized by hexylene glycol and inhibition of the catastrophe factor mitotic centromere-associated kinesin (MCAK) (a kinesin 13, previously called XKCM) and destabilized by depolymerizing drugs. The opposed motors Eg5 and dynein were inhibited separately and together. Our results are consistent with important roles for polymerization dynamics in regulating spindle length, and for opposed motors in regulating the relative stability of bipolar versus monopolar organization. The response to microtubule destabilization suggests that an unidentified tensile element acts in parallel with these conventional factors, generating spindle shortening force.

scholarly journals Steady-State Size Distributions in Probabilistic Models of the Cell Division Cycle

1985 ◽  
Vol 45 (4) ◽  
pp. 523-540 ◽  
Author(s):  
Kenneth B. Hannsgen ◽  
John J. Tyson ◽  
Layne T. Watson
Keyword(s):  
Steady State ◽  
Cell Division ◽  
Probabilistic Models ◽  
Cell Division Cycle ◽  
Size Distributions ◽  
State Size

scholarly journals EB1 and EB3 regulate microtubule minus end organization and Golgi morphology

2017 ◽  
Vol 216 (10) ◽  
pp. 3179-3198 ◽  
Author(s):  
Chao Yang ◽  
Jingchao Wu ◽  
Cecilia de Heus ◽  
Ilya Grigoriev ◽  
Nalan Liv ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Lines ◽  
Protein Complexes ◽  
Focal Adhesions ◽  
Microtubule Organization ◽  
The Core ◽  
Microtubule Polymerization ◽  
Golgi Membranes ◽  
Core Components ◽  
Knockout Technology

End-binding proteins (EBs) are the core components of microtubule plus end tracking protein complexes, but it is currently unknown whether they are essential for mammalian microtubule organization. Here, by using CRISPR/Cas9-mediated knockout technology, we generated stable cell lines lacking EB2 and EB3 and the C-terminal partner-binding half of EB1. These cell lines show only mild defects in cell division and microtubule polymerization. However, the length of CAMSAP2-decorated stretches at noncentrosomal microtubule minus ends in these cells is reduced, microtubules are detached from Golgi membranes, and the Golgi complex is more compact. Coorganization of microtubules and Golgi membranes depends on the EB1/EB3–myomegalin complex, which acts as membrane–microtubule tether and counteracts tight clustering of individual Golgi stacks. Disruption of EB1 and EB3 also perturbs cell migration, polarity, and the distribution of focal adhesions. EB1 and EB3 thus affect multiple interphase processes and have a major impact on microtubule minus end organization.

scholarly journals Asymmetric cell division-dominant neutral drift model for normal intestinal stem cell homeostasis

2019 ◽  
Vol 316 (1) ◽  
pp. G64-G74 ◽  
Author(s):  
Yoshitatsu Sei ◽  
Jianying Feng ◽  
Carson C. Chow ◽  
Stephen A. Wank
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Asymmetric Cell Division ◽  
Dominant Mode ◽  
Lineage Tracing ◽  
Intestinal Stem Cells ◽  
In Vivo Studies ◽  
Neutral Drift ◽  
Drift Model

The normal intestinal epithelium is continuously regenerated at a rapid rate from actively cycling Lgr5-expressing intestinal stem cells (ISCs) that reside at the crypt base. Recent mathematical modeling based on several lineage-tracing studies in mice shows that the symmetric cell division-dominant neutral drift model fits well with the observed in vivo growth of ISC clones and suggests that symmetric divisions are central to ISC homeostasis. However, other studies suggest a critical role for asymmetric cell division in the maintenance of ISC homeostasis in vivo. Here, we show that the stochastic branching and Moran process models with both a symmetric and asymmetric division mode not only simulate the stochastic growth of the ISC clone in silico but also closely fit the in vivo stem cell dynamics observed in lineage-tracing studies. In addition, the proposed model with highest probability for asymmetric division is more consistent with in vivo observations reported here and by others. Our in vivo studies of mitotic spindle orientations and lineage-traced progeny pairs indicate that asymmetric cell division is a dominant mode used by ISCs under normal homeostasis. Therefore, we propose the asymmetric cell division-dominant neutral drift model for normal ISC homeostasis. NEW & NOTEWORTHY The prevailing mathematical model suggests that intestinal stem cells (ISCs) divide symmetrically. The present study provides evidence that asymmetric cell division is the major contributor to ISC maintenance and thus proposes an asymmetric cell division-dominant neutral drift model. Consistent with this model, in vivo studies of mitotic spindle orientation and lineage-traced progeny pairs indicate that asymmetric cell division is the dominant mode used by ISCs under normal homeostasis.

scholarly journals The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Thomas S McAlear ◽  
Susanne Bechstedt
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Mitotic Spindle ◽  
Apparent Rate Constant ◽  
Microtubule Dynamics ◽  
Proliferation Marker ◽  
Microtubule Growth ◽  
Large Rearrangements ◽  
And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

scholarly journals A non-canonical function for Centromere-associated protein-E (CENP-E) controls centrosome integrity and orientation of cell division

2020 ◽  
Author(s):  
Mikito Owa ◽  
Brian Dynlacht
Keyword(s):  
Cell Division ◽  
Mitotic Arrest ◽  
Canonical Function ◽  
Kinesin Motor ◽  
Cell Divisions ◽  
Pericentriolar Material ◽  
Conventional Methods ◽  
In Cells

SummaryCentromere-associated protein-E (CENP-E) is a kinesin motor localizing at kinetochores. Although its mitotic functions have been well studied, it has been challenging to investigate direct consequences of CENP-E removal using conventional methods because CENP-E depletion results in mitotic arrest. In this study, we harnessed an auxin-inducible degron system to achieve acute degradation of CENP-E. We revealed a kinetochore-independent role for CENP-E that removes pericentriolar material 1 (PCM1) from centrosomes in G2 phase. After acute loss of CENP-E, centrosomal Polo-like kinase 1 (Plk1) is sequestered by accumulated PCM1, resulting in aberrant phosphorylation and destabilization of centrosomes, which triggers loss of astral microtubules and oblique cell divisions. Furthermore, we also observed centrosome and cell division defects in cells from a microcephaly patient with mutations in CENPE. Orientation of cell division is deregulated in some microcephalic patients, and our unanticipated findings provide a unifying principle that explains how microcephaly can result from centrosomal defects.

Controlling kinesin motor proteins in nanoengineered systems through a metal-binding on/off switch

2008 ◽  
Vol 101 (3) ◽  
pp. 478-486 ◽  
Author(s):  
Adrienne C. Greene ◽  
Amanda M. Trent ◽  
George D. Bachand
Keyword(s):  
Metal Binding ◽  
Motor Proteins ◽  
Kinesin Motor ◽  
Kinesin Motor Proteins
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