scholarly journals Anillin promotes astral microtubule-directed cortical myosin polarization

2011 ◽  
Vol 22 (17) ◽  
pp. 3165-3175 ◽  
Author(s):  
Yu Chung Tse ◽  
Alisa Piekny ◽  
Michael Glotzer
Keyword(s):  
Myosin Ii ◽  
Cell Polarization ◽  
Cell Cortex ◽  
Polar Regions ◽  
Contractile Ring ◽  
Central Spindle ◽  
Astral Microtubule ◽  
Nonmuscle Myosin Ii ◽  
Evolutionarily Conserved ◽  
Cortical Asymmetry

Assembly of a cytokinetic contractile ring is a form of cell polarization in which the equatorial cell cortex becomes differentiated from the polar regions. Microtubules direct cytokinetic polarization via the central spindle and astral microtubules. The mechanism of central spindle–directed furrow formation is reasonably well understood, but the aster-directed pathway is not. In aster-directed furrowing, cytoskeletal factors accumulate to high levels at sites distal to the asters and at reduced levels at cortical sites near the asters. In this paper, we demonstrate that the cytoskeletal organizing protein anillin (ANI-1) promotes the formation of an aster-directed furrow in Caenorhabditis elegans embryos. Microtubule-directed nonmuscle myosin II polarization is aberrant in embryos depleted of ANI-1. In contrast, microtubule-directed polarized ANI-1 localization is largely unaffected by myosin II depletion. Consistent with a role in the induction of cortical asymmetry, ANI-1 also contributes to the polarization of arrested oocytes. Anillin has an evolutionarily conserved capacity to associate with microtubules, possibly providing an inhibitory mechanism to promote polarization of the cell cortex.

scholarly journals An ECT2–centralspindlin complex regulates the localization and function of RhoA

2005 ◽  
Vol 170 (4) ◽  
pp. 571-582 ◽  
Author(s):  
Özlem Yüce ◽  
Alisa Piekny ◽  
Michael Glotzer
Keyword(s):  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Myosin Ii ◽  
Cell Cortex ◽  
Contractile Ring ◽  
Division Plane ◽  
Central Spindle ◽  
Ring Assembly ◽  
Cortical Localization ◽  
And Function

In anaphase, the spindle dictates the site of contractile ring assembly. Assembly and ingression of the contractile ring involves activation of myosin-II and actin polymerization, which are triggered by the GTPase RhoA. In many cells, the central spindle affects division plane positioning via unknown molecular mechanisms. Here, we dissect furrow formation in human cells and show that the RhoGEF ECT2 is required for cortical localization of RhoA and contractile ring assembly. ECT2 concentrates on the central spindle by binding to centralspindlin. Depletion of the centralspindlin component MKLP1 prevents central spindle localization of ECT2; however, RhoA, F-actin, and myosin still accumulate on the equatorial cell cortex. Depletion of the other centralspindlin component, CYK-4/MgcRacGAP, prevents cortical accumulation of RhoA, F-actin, and myosin. CYK-4 and ECT2 interact, and this interaction is cell cycle regulated via ECT2 phosphorylation. Thus, central spindle localization of ECT2 assists division plane positioning and the CYK-4 subunit of centralspindlin acts upstream of RhoA to promote furrow assembly.

scholarly journals Mechanism of the formation of contractile ring in dividing cultured animal cells. II. Cortical movement of microinjected actin filaments.

1990 ◽  
Vol 111 (5) ◽  
pp. 1905-1911 ◽  
Author(s):  
L G Cao ◽  
Y L Wang
Keyword(s):  
Actin Filaments ◽  
Average Rate ◽  
Rat Kidney ◽  
Equatorial Region ◽  
Cell Cortex ◽  
Polar Regions ◽  
Cortical Actin ◽  
Animal Cells ◽  
Contractile Ring ◽  
Directional Movement

The contractile ring in dividing animal cells is formed primarily through the reorganization of existing actin filaments (Cao, L.-G., and Y.-L. Wang. 1990. J. Cell Biol. 110:1089-1096), but it is not clear whether the process involves a random recruitment of diffusible actin filaments from the cytoplasm, or a directional movement of cortically associated filaments toward the equator. We have studied this question by observing the distribution of actin filaments that have been labeled with fluorescent phalloidin and microinjected into dividing normal rat kidney (NRK) cells. The labeled filaments are present primarily in the cytoplasm during prometaphase and early metaphase, but become associated extensively with the cell cortex 10-15 min before the onset of anaphase. This process is manifested both as an increase in cortical fluorescence intensity and as movements of discrete aggregates of actin filaments toward the cortex. The concentration of actin fluorescence in the equatorial region, accompanied by a decrease of fluorescence in polar regions, is detected 2-3 min after the onset of anaphase. By directly tracing the distribution of aggregates of labeled actin filaments, we are able to detect, during anaphase and telophase, movements of cortical actin filaments toward the equator at an average rate of 1.0 micron/min. Our results, combined with previous observations, suggest that the organization of actin filaments during cytokinesis probably involves an association of cytoplasmic filaments with the cortex, a movement of cortical filaments toward the cleavage furrow, and a dissociation of filaments from the equatorial cortex.

scholarly journals Polar relaxation by dynein-mediated removal of cortical myosin II

2020 ◽  
Vol 219 (8) ◽  
Author(s):  
Bernardo Chapa-y-Lazo ◽  
Motonari Hamanaka ◽  
Alexander Wray ◽  
Mohan K. Balasubramanian ◽  
Masanori Mishima
Keyword(s):  
Recent Work ◽  
Molecular Mechanism ◽  
Molecular Mechanisms ◽  
Myosin Ii ◽  
Cell Cortex ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
C Elegans ◽  
Polar Cell

Nearly six decades ago, Lewis Wolpert proposed the relaxation of the polar cell cortex by the radial arrays of astral microtubules as a mechanism for cleavage furrow induction. While this mechanism has remained controversial, recent work has provided evidence for polar relaxation by astral microtubules, although its molecular mechanisms remain elusive. Here, using C. elegans embryos, we show that polar relaxation is achieved through dynein-mediated removal of myosin II from the polar cortexes. Mutants that position centrosomes closer to the polar cortex accelerated furrow induction, whereas suppression of dynein activity delayed furrowing. We show that dynein-mediated removal of myosin II from the polar cortexes triggers a bidirectional cortical flow toward the cell equator, which induces the assembly of the actomyosin contractile ring. These results provide a molecular mechanism for the aster-dependent polar relaxation, which works in parallel with equatorial stimulation to promote robust cytokinesis.

scholarly journals Expansion and concatenation of nonmuscle myosin IIA filaments drive cellular contractile system formation during interphase and mitosis

2016 ◽  
Vol 27 (9) ◽  
pp. 1465-1478 ◽  
Author(s):  
Aidan M. Fenix ◽  
Nilay Taneja ◽  
Carmen A. Buttler ◽  
John Lewis ◽  
Schuyler B. Van Engelenburg ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Cell Movement ◽  
Nonmuscle Myosin ◽  
Contractile Ring ◽  
Contractile System ◽  
Nonmuscle Myosin Ii ◽  
Dividing Cells ◽  
Contractile Forces

Cell movement and cytokinesis are facilitated by contractile forces generated by the molecular motor, nonmuscle myosin II (NMII). NMII molecules form a filament (NMII-F) through interactions of their C-terminal rod domains, positioning groups of N-terminal motor domains on opposite sides. The NMII motors then bind and pull actin filaments toward the NMII-F, thus driving contraction. Inside of crawling cells, NMIIA-Fs form large macromolecular ensembles (i.e., NMIIA-F stacks), but how this occurs is unknown. Here we show NMIIA-F stacks are formed through two non–mutually exclusive mechanisms: expansion and concatenation. During expansion, NMIIA molecules within the NMIIA-F spread out concurrent with addition of new NMIIA molecules. Concatenation occurs when multiple NMIIA-Fs/NMIIA-F stacks move together and align. We found that NMIIA-F stack formation was regulated by both motor activity and the availability of surrounding actin filaments. Furthermore, our data showed expansion and concatenation also formed the contractile ring in dividing cells. Thus interphase and mitotic cells share similar mechanisms for creating large contractile units, and these are likely to underlie how other myosin II–based contractile systems are assembled.

scholarly journals Carboxyl-terminal-dependent recruitment of nonmuscle myosin II to megakaryocyte contractile ring during polyploidization

Blood ◽  
2014 ◽  
Vol 124 (16) ◽  
pp. 2564-2568 ◽  
Author(s):  
Idinath Badirou ◽  
Jiajia Pan ◽  
Céline Legrand ◽  
Aibing Wang ◽  
Larissa Lordier ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Specific Role ◽  
Nonmuscle Myosin ◽  
Contractile Ring ◽  
Terminal Domain ◽  
Nonmuscle Myosin Ii ◽  
Key Points ◽  
Carboxyl Terminal

Key Points C-terminal domain determines myosin II localization to the MK contractile ring and the specific role of NMII-B in MK polyploidization.

Microtubule-mediated centrosome motility and the positioning of cleavage furrows in multinucleate myosin II-null cells

1998 ◽  
Vol 111 (9) ◽  
pp. 1227-1240 ◽  
Author(s):  
R. Neujahr ◽  
R. Albrecht ◽  
J. Kohler ◽  
M. Matzner ◽  
J.M. Schwartz ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Myosin Ii ◽  
Cytoplasmic Dynein ◽  
Cell Cortex ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
Mitotic Apparatus ◽  
Alpha Tubulin ◽  
Multinucleate Cells ◽  
Green Fluorescent

To study centrosome motility and the interaction of microtubules with the cell cortex in mitotic, post-mitotic and interphase cells, (alpha)-tubulin was tagged in Dictyostelium discoideum with green fluorescent protein. Multinucleate cells formed by myosin II-null mutants proved to be especially suited for the analysis of the control of cleavage furrow formation by the microtubule system. After docking of the mitotic apparatus onto the cell cortex during anaphase, the cell surface is activated to form ruffles on top of the asters of microtubules that emanate from the centrosomes. Cleavage furrows are initiated at spaces between the asters independently of the positions of spindles. Once initiated, the furrows expand as deep folds without a continued connection to the microtubule system. Occurrence of unilateral furrows indicates that a closed contractile ring is dispensable for cytokinesis in Dictyostelium. The progression of cytokinesis in the multinucleate cells underlines the importance of proteins other than myosin II in specifying a cleavage furrow. The analysis of centrosome motility suggests a major role for a minus-end directed motor protein, probably cytoplasmic dynein, in applying traction forces on guiding microtubules that connect the centrosome with the cell cortex.

scholarly journals Plastin increases cortical connectivity to facilitate robust polarization and timely cytokinesis

2017 ◽  
Vol 216 (5) ◽  
pp. 1371-1386 ◽  
Author(s):  
Wei Yung Ding ◽  
Hui Ting Ong ◽  
Yusuke Hara ◽  
Jantana Wongsantichon ◽  
Yusuke Toyama ◽  
...  
Keyword(s):  
Cell Shape ◽  
Animal Cell ◽  
Cell Cortex ◽  
Cross Linking ◽  
Cortical Dynamics ◽  
Actomyosin Contractility ◽  
Nonmuscle Myosin Ii ◽  
Evolutionarily Conserved ◽  
Contractile Forces

The cell cortex is essential to maintain animal cell shape, and contractile forces generated within it by nonmuscle myosin II (NMY-2) drive cellular morphogenetic processes such as cytokinesis. The role of actin cross-linking proteins in cortical dynamics is still incompletely understood. Here, we show that the evolutionarily conserved actin bundling/cross-linking protein plastin is instrumental for the generation of potent cortical actomyosin contractility in the Caenorhabditis elegans zygote. PLST-1 was enriched in contractile structures and was required for effective coalescence of NMY-2 filaments into large contractile foci and for long-range coordinated contractility in the cortex. In the absence of PLST-1, polarization was compromised, cytokinesis was delayed or failed, and 50% of embryos died during development. Moreover, mathematical modeling showed that an optimal amount of bundling agents enhanced the ability of a network to contract. We propose that by increasing the connectivity of the F-actin meshwork, plastin enables the cortex to generate stronger and more coordinated forces to accomplish cellular morphogenesis.

scholarly journals Role of Survivin in cytokinesis revealed by a separation-of-function allele

2011 ◽  
Vol 22 (20) ◽  
pp. 3779-3790 ◽  
Author(s):  
Edith Szafer-Glusman ◽  
Margaret T. Fuller ◽  
Maria Grazia Giansanti
Keyword(s):  
Myosin Ii ◽  
Cell Cortex ◽  
Direct Role ◽  
Central Spindle ◽  
Ring Assembly ◽  
Chromosomal Passenger ◽  
Missense Allele ◽  
Ring Analysis ◽  
And Function

The chromosomal passenger complex (CPC), containing Aurora B kinase, Inner Centromere Protein, Survivin, and Borealin, regulates chromosome condensation and interaction between kinetochores and microtubules at metaphase, then relocalizes to midzone microtubules at anaphase and regulates central spindle organization and cytokinesis. However, the precise role(s) played by the CPC in anaphase have been obscured by its prior functions in metaphase. Here we identify a missense allele of Drosophila Survivin that allows CPC localization and function during metaphase but not cytokinesis. Analysis of mutant cells showed that Survivin is essential to target the CPC and the mitotic kinesin-like protein 1 orthologue Pavarotti (Pav) to the central spindle and equatorial cell cortex during anaphase in both larval neuroblasts and spermatocytes. Survivin also enabled localization of Polo kinase and Rho at the equatorial cortex in spermatocytes, critical for contractile ring assembly. In neuroblasts, in contrast, Survivin function was not required for localization of Rho, Polo, or Myosin II to a broad equatorial cortical band but was required for Myosin II to transition to a compact, fully constricted ring. Analysis of this “separation-of-function” allele demonstrates the direct role of Survivin and the CPC in cytokinesis and highlights striking differences in regulation of cytokinesis in different cell systems.

scholarly journals Taxol-stabilized Microtubules Can Position the Cytokinetic Furrow in Mammalian Cells

2005 ◽  
Vol 16 (9) ◽  
pp. 4423-4436 ◽  
Author(s):  
Katie B. Shannon ◽  
Julie C. Canman ◽  
C. Ben Moree ◽  
Jennifer S. Tirnauer ◽  
E. D. Salmon
Keyword(s):  
Cell Division ◽  
Mammalian Cells ◽  
Myosin Ii ◽  
Spindle Checkpoint ◽  
Microtubule Dynamics ◽  
Cell Cortex ◽  
Contractile Ring ◽  
Spindle Microtubule ◽  
Anaphase Onset ◽  
Centromere Protein

How microtubules act to position the plane of cell division during cytokinesis is a topic of much debate. Recently, we showed that a subpopulation of stable microtubules extends past chromosomes and interacts with the cell cortex at the site of furrowing, suggesting that these stabilized microtubules may stimulate contractility. To test the hypothesis that stable microtubules can position furrows, we used taxol to rapidly suppress microtubule dynamics during various stages of mitosis in PtK1 cells. Cells with stabilized prometaphase or metaphase microtubule arrays were able to initiate furrowing when induced into anaphase by inhibition of the spindle checkpoint. In these cells, few microtubules contacted the cortex. Furrows formed later than usual, were often aberrant, and did not progress to completion. Images showed that furrowing correlated with the presence of one or a few stable spindle microtubule plus ends at the cortex. Actin, myosin II, and anillin were all concentrated in these furrows, demonstrating that components of the contractile ring can be localized by stable microtubules. Inner centromere protein (INCENP) was not found in these ingressions, confirming that INCENP is dispensable for furrow positioning. Taxol-stabilization of the numerous microtubule-cortex interactions after anaphase onset delayed furrow initiation but did not perturb furrow positioning. We conclude that taxol-stabilized microtubules can act to position the furrow and that loss of microtubule dynamics delays the timing of furrow onset and prevents completion. We discuss our findings relative to models for cleavage stimulation.

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