Myosin II-Independent Cytokinesis in Dictyostelium. Its Mechanism and Implications.

Uyeda, Taro Q.P.; Kitayama, Chikako; Yumura, Shigehiko

doi:10.1247/csf.25.1

Cited by 49 publications

(18 citation statements)

References 63 publications

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“…The sum of the energy landscape (black+blue) is shown in red, in which the in vivo shape is stabilized. Consistent with this ides, cell adhesion is critical for the progression of the contractile ring-independent cytokinesis in Dictyostelium discoideum and mammalian cultured cells [19], [27], [28]. The contractile ring-independent cytokinesis might be driven by the combination of cell surface stiffness and cell adhesion.…”

Section: Supporting Informationsupporting

confidence: 63%

A High-Resolution Shape Fitting and Simulation Demonstrated Equatorial Cell Surface Softening during Cytokinesis and Its Promotive Role in Cytokinesis

et al. 2012

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Different models for animal cell cytokinesis posit that the stiffness of the equatorial cortex is either increased or decreased relative to the stiffness of the polar cortex. A recent work has suggested that the critical cytokinesis signaling complex centralspindlin may reduce the stiffness of the equatorial cortex by inactivating the small GTPase Rac. To determine if such a reduction occurs and if it depends on centralspindlin, we devised a method to estimate cortical bending stiffness with high spatio-temporal resolution from in vivo cell shapes. Using the early Caenorhabditis elegans embryo as a model, we show that the stiffness of the equatorial cell surface is reduced during cytokinesis, whereas the stiffness of the polar cell surface remains stiff. The equatorial reduction of stiffness was compromised in cells with a mutation in the gene encoding the ZEN-4/kinesin-6 subunit of centralspindlin. Theoretical modeling showed that the absence of the equatorial reduction of stiffness could explain the arrest of furrow ingression in the mutant. By contrast, the equatorial reduction of stiffness was sufficient to generate a cleavage furrow even without the constriction force of the contractile ring. In this regime, the contractile ring had a supportive contribution to furrow ingression. We conclude that stiffness is reduced around the equator in a centralspindlin-dependent manner. In addition, computational modeling suggests that proper regulation of stiffness could be sufficient for cleavage furrow ingression.

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Section: Supporting Informationsupporting

confidence: 63%

A High-Resolution Shape Fitting and Simulation Demonstrated Equatorial Cell Surface Softening during Cytokinesis and Its Promotive Role in Cytokinesis

et al. 2012

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“…When subsequently placed on a substrate, they quickly adhere and different parts of the large cells move in different directions. Eventually, a thin cytoplasmic strand is formed between each cell fragment and the rest of the cell, which is severed after further pulling by the movement of the cell fragment, effectively resulting in cell cycle-uncoupled cell division (cytokinesis C or traction-mediated cytofission) [41], [42], [43]. During this process, the cytoplasmic strands are greatly stretched in an apparently passive manner, without myosin II.…”

Section: Resultsmentioning

confidence: 99%

Stretching Actin Filaments within Cells Enhances their Affinity for the Myosin II Motor Domain

et al. 2011

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To test the hypothesis that the myosin II motor domain (S1) preferentially binds to specific subsets of actin filaments in vivo, we expressed GFP-fused S1 with mutations that enhanced its affinity for actin in Dictyostelium cells. Consistent with the hypothesis, the GFP-S1 mutants were localized along specific portions of the cell cortex. Comparison with rhodamine-phalloidin staining in fixed cells demonstrated that the GFP-S1 probes preferentially bound to actin filaments in the rear cortex and cleavage furrows, where actin filaments are stretched by interaction with endogenous myosin II filaments. The GFP-S1 probes were similarly enriched in the cortex stretched passively by traction forces in the absence of myosin II or by external forces using a microcapillary. The preferential binding of GFP-S1 mutants to stretched actin filaments did not depend on cortexillin I or PTEN, two proteins previously implicated in the recruitment of myosin II filaments to stretched cortex. These results suggested that it is the stretching of the actin filaments itself that increases their affinity for the myosin II motor domain. In contrast, the GFP-fused myosin I motor domain did not localize to stretched actin filaments, which suggests different preferences of the motor domains for different structures of actin filaments play a role in distinct intracellular localizations of myosin I and II. We propose a scheme in which the stretching of actin filaments, the preferential binding of myosin II filaments to stretched actin filaments, and myosin II-dependent contraction form a positive feedback loop that contributes to the stabilization of cell polarity and to the responsiveness of the cells to external mechanical stimuli.

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“…Constriction and abscission also appear as distinct cytokinetic stages in eukaryotes using an actin-myosin ring. Further cytokinesis can occur in the absence of myosin II, the motor that drives contraction, under certain conditions [59,60]. The phragmoplast – an interdigitated microtubule array in plants – is an alternative to the purse string mechanism that delivers cell plate forming vesicles precisely between daughter cells.…”

Section: Conserved Cellular Processes With Atypical Mechanisms In Thementioning

confidence: 99%

Alternative cytoskeletal landscapes: cytoskeletal novelty and evolution in basal excavate protists

Dawson

Paredez

2013

Current Opinion in Cell Biology

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Microbial eukaryotes encompass the majority of eukaryotic evolutionary and cytoskeletal diversity. The cytoskeletal complexity observed in multicellular organisms appears to be an expansion of components present in genomes of diverse microbial eukaryotes such as the basal lineage of flagellates, the Excavata. Excavate protists have complex and diverse cytoskeletal architectures and life cycles – essentially alternative cytoskeletal “landscapes” – yet still possess conserved microtubule- and actin-associated proteins. Comparative genomic analyses have revealed that a subset of excavates, however, lack many canonical actin-binding proteins central to actin cytoskeleton function in other eukaryotes. Overall, excavates possess numerous uncharacterized and “hypothetical” genes, and may represent an undiscovered reservoir of novel cytoskeletal genes and cytoskeletal mechanisms. The continued development of molecular genetic tools in these complex microbial eukaryotes will undoubtedly contribute to our overall understanding of cytoskeletal diversity and evolution.

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Myosin II-Independent Cytokinesis in Dictyostelium. Its Mechanism and Implications.

Cited by 49 publications

References 63 publications

A High-Resolution Shape Fitting and Simulation Demonstrated Equatorial Cell Surface Softening during Cytokinesis and Its Promotive Role in Cytokinesis

A High-Resolution Shape Fitting and Simulation Demonstrated Equatorial Cell Surface Softening during Cytokinesis and Its Promotive Role in Cytokinesis

Stretching Actin Filaments within Cells Enhances their Affinity for the Myosin II Motor Domain

Alternative cytoskeletal landscapes: cytoskeletal novelty and evolution in basal excavate protists

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