scholarly journals Rap1-dependent pathways coordinate cytokinesis in Dictyostelium

2014 ◽  
Vol 25 (25) ◽  
pp. 4195-4204 ◽  
Author(s):  
Katarzyna Plak ◽  
Ineke Keizer-Gunnink ◽  
Peter J. M. van Haastert ◽  
Arjan Kortholt
Keyword(s):  
Cell Division ◽  
Cell Cortex ◽  
Adherent Cells ◽  
Contractile Ring ◽  
Daughter Cells ◽  
Small G Protein ◽  
Rap1 Activation ◽  
Actomyosin Cytoskeleton ◽  
Mutant Cells ◽  
Severe Growth

Cytokinesis is the final step of mitosis when a mother cell is separated into two daughter cells. Major cytoskeletal changes are essential for cytokinesis; it is, however, not well understood how the microtubules and actomyosin cytoskeleton are exactly regulated in time and space. In this paper, we show that during the early stages of cytokinesis, in rounded-up Dictyostelium discoideum cells, the small G-protein Rap1 is activated uniformly at the cell cortex. When cells begin to elongate, active Rap1 becomes restricted from the furrow region, where the myosin contractile ring is subsequently formed. In the final stages of cytokinesis, active Rap1 is only present at the cell poles. Mutant cells with decreased Rap1 activation at the poles showed strongly decreased growth rates. Hyperactivation of Rap1 results in severe growth delays and defective spindle formation in adherent cells and cell death in suspension. Furthermore, Rap mutants show aberrant regulation of the actomyosin cytoskeleton, resulting in extended furrow ingression times and asymmetrical cell division. We propose that Rap1 drives cytokinesis progression by coordinating the three major cytoskeletal components: microtubules, actin, and myosin II. Importantly, mutated forms of Rap also affect cytokinesis in other organisms, suggesting a conserved role for Rap in cell division.

scholarly journals Network Contractility during Cytokinesis—From Molecular to Global Views

Biomolecules ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 194 ◽  
Author(s):  
Joana Leite ◽  
Daniel Sampaio Osorio ◽  
Ana Filipa Sobral ◽  
Ana Marta Silva ◽  
Ana Xavier Carvalho
Keyword(s):  
Motor Activity ◽  
Network Architecture ◽  
Theoretical Models ◽  
Coarse Grained ◽  
Cell Cortex ◽  
Contractile Ring ◽  
Daughter Cells ◽  
Experimental Approaches ◽  
Global Understanding ◽  
Last Stage

Cytokinesis is the last stage of cell division, which partitions the mother cell into two daughter cells. It requires the assembly and constriction of a contractile ring that consists of a filamentous contractile network of actin and myosin. Network contractility depends on network architecture, level of connectivity and myosin motor activity, but how exactly is the contractile ring network organized or interconnected and how much it depends on motor activity remains unclear. Moreover, the contractile ring is not an isolated entity; rather, it is integrated into the surrounding cortex. Therefore, the mechanical properties of the cell cortex and cortical behaviors are expected to impact contractile ring functioning. Due to the complexity of the process, experimental approaches have been coupled to theoretical modeling in order to advance its global understanding. While earlier coarse-grained descriptions attempted to provide an integrated view of the process, recent models have mostly focused on understanding the behavior of an isolated contractile ring. Here we provide an overview of the organization and dynamics of the actomyosin network during cytokinesis and discuss existing theoretical models in light of cortical behaviors and experimental evidence from several systems. Our view on what is missing in current models and should be tested in the future is provided.

scholarly journals Fascetto interacting protein ensures proper cytokinesis and ploidy

2019 ◽  
Vol 30 (8) ◽  
pp. 992-1007 ◽  
Author(s):  
Zachary T. Swider ◽  
Rachel K. Ng ◽  
Ramya Varadarajan ◽  
Carey J. Fagerstrom ◽  
Nasser M. Rusan
Keyword(s):  
Cell Division ◽  
Tissue Repair ◽  
Complete Separation ◽  
Contractile Ring ◽  
Interacting Protein ◽  
Simultaneous Reduction ◽  
Central Spindle ◽  
Daughter Cells ◽  
Molecular Machinery ◽  
The Brain

Cell division is critical for development, organ growth, and tissue repair. The later stages of cell division include the formation of the microtubule (MT)-rich central spindle in anaphase, which is required to properly define the cell equator, guide the assembly of the acto-myosin contractile ring and ultimately ensure complete separation and isolation of the two daughter cells via abscission. Much is known about the molecular machinery that forms the central spindle, including proteins needed to generate the antiparallel overlapping interzonal MTs. One critical protein that has garnered great attention is the protein regulator of cytokinesis 1, or Fascetto (Feo) in Drosophila, which forms a homodimer to cross-link interzonal MTs, ensuring proper central spindle formation and cytokinesis. Here, we report on a new direct protein interactor and regulator of Feo we named Feo interacting protein (FIP). Loss of FIP results in a reduction in Feo localization, rapid disassembly of interzonal MTs, and several defects related to cytokinesis failure, including polyploidization of neural stem cells. Simultaneous reduction in Feo and FIP results in very large, tumorlike DNA-filled masses in the brain that contain hundreds of centrosomes. In aggregate, our data show that FIP acts directly on Feo to ensure fully accurate cell division.

scholarly journals The Actin Gene ACT1 Is Required for Phagocytosis, Motility, and Cell Separation of Tetrahymena thermophila

2006 ◽  
Vol 5 (3) ◽  
pp. 555-567 ◽  
Author(s):  
Norman E. Williams ◽  
Che-Chia Tsao ◽  
Josephine Bowen ◽  
Gery L. Hehman ◽  
Ruth J. Williams ◽  
...  
Keyword(s):  
Cell Separation ◽  
Tetrahymena Thermophila ◽  
Cell Cortex ◽  
Actin Gene ◽  
Wild Type ◽  
Daughter Cells ◽  
Genetic Constructs ◽  
Mutant Cells ◽  
Phagocytic Uptake ◽  
Cell Cycle Length

ABSTRACT A previously identified Tetrahymena thermophila actin gene (C. G. Cupples and R. E. Pearlman, Proc. Natl. Acad. Sci. USA 83:5160-5164, 1986), here called ACT1, was disrupted by insertion of a neo3 cassette. Cells in which all expressed copies of this gene were disrupted exhibited intermittent and extremely slow motility and severely curtailed phagocytic uptake. Transformation of these cells with inducible genetic constructs that contained a normal ACT1 gene restored motility. Use of an epitope-tagged construct permitted visualization of Act1p in the isolated axonemes of these rescued cells. In ACT1Δ mutant cells, ultrastructural abnormalities of outer doublet microtubules were present in some of the axonemes. Nonetheless, these cells were still able to assemble cilia after deciliation. The nearly paralyzed ACT1Δ cells completed cleavage furrowing normally, but the presumptive daughter cells often failed to separate from one another and later became reintegrated. Clonal analysis revealed that the cell cycle length of the ACT1Δ cells was approximately double that of wild-type controls. Clones could nonetheless be maintained for up to 15 successive fissions, suggesting that the ACT1 gene is not essential for cell viability or growth. Examination of the cell cortex with monoclonal antibodies revealed that whereas elongation of ciliary rows and formation of oral structures were normal, the ciliary rows of reintegrated daughter cells became laterally displaced and sometimes rejoined indiscriminately across the former division furrow. We conclude that Act1p is required in Tetrahymena thermophila primarily for normal ciliary motility and for phagocytosis and secondarily for the final separation of daughter cells.

scholarly journals The Septation Apparatus, an Autonomous System in Budding Yeast

2002 ◽  
Vol 13 (8) ◽  
pp. 2747-2759 ◽  
Author(s):  
Dong-Hyun Roh ◽  
Blair Bowers ◽  
Martin Schmidt ◽  
Enrico Cabib
Keyword(s):  
Cell Division ◽  
Fluorescent Protein ◽  
Nuclear Division ◽  
Fluorescent Proteins ◽  
Budding Yeast ◽  
Cell Cortex ◽  
Nonpermissive Temperature ◽  
Contractile Ring ◽  
Primary Septum ◽  
Endocytic Vesicles

Actomyosin ring contraction and chitin primary septum deposition are interdependent processes in cell division of budding yeast. By fusing Myo1p, as representative of the contractile ring, and Chs2p for the primary septum, to different fluorescent proteins we show herein that the two processes proceed essentially at the same location and simultaneously. Chs2p differs from Myo1p in that it reflects the changes in shape of the plasma membrane to which it is attached and in that it is packed after its action into visible endocytic vesicles for its disposal. To ascertain whether this highly coordinated system could function independently of other cell cycle events, we reexamined the septum-like structures made by the septin mutant cdc3 at various sites on the cell cortex at the nonpermissive temperature. With the fluorescent fusion proteins mentioned above, we observed that incdc3 at 37°C both Myo1p and Chs2p colocalize at different spots of the cell cortex. A contraction of the Myo1p patch could also be detected, as well as that of a Chs2p patch, with subsequent appearance of vesicles. Furthermore, the septin Cdc12p, fused with yellow or cyan fluorescent protein, also colocalized with Myo1p and Chs2p at the aberrant locations. The formation of delocalized septa did not require nuclear division. We conclude that the septation apparatus, composed of septins, contractile ring, and the chitin synthase II system, can function at ectopic locations autonomously and independently of cell division, and that it can recruit the other elements necessary for the formation of secondary septa.

scholarly journals Inhibition of polar actin assembly by astral microtubules is required for cytokinesis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anan Chen ◽  
Luisa Ulloa Severino ◽  
Thomas C. Panagiotou ◽  
Trevor F. Moraes ◽  
Darren A. Yuen ◽  
...  
Keyword(s):  
Cell Division ◽  
Actin Cytoskeleton ◽  
Actin Filament ◽  
Cell Cortex ◽  
Actin Assembly ◽  
Actin Network ◽  
Contractile Ring ◽  
Actin Networks ◽  
Membrane Blebbing ◽  
Actin Isoform

AbstractDuring cytokinesis, the actin cytoskeleton is partitioned into two spatially distinct actin isoform specific networks: a β-actin network that generates the equatorial contractile ring, and a γ-actin network that localizes to the cell cortex. Here we demonstrate that the opposing regulation of the β- and γ-actin networks is required for successful cytokinesis. While activation of the formin DIAPH3 at the cytokinetic furrow underlies β-actin filament production, we show that the γ-actin network is specifically depleted at the cell poles through the localized deactivation of the formin DIAPH1. During anaphase, CLIP170 is delivered by astral microtubules and displaces IQGAP1 from DIAPH1, leading to formin autoinhibition, a decrease in cortical stiffness and localized membrane blebbing. The contemporaneous production of a β-actin contractile ring at the cell equator and loss of γ-actin from the poles is required to generate a stable cytokinetic furrow and for the completion of cell division.

scholarly journals Fascetto Interacting Protein (FIP) Regulates Fascetto (PRC1) to Ensure Proper Cytokinesis and Ploidy

2018 ◽  
Author(s):  
Zachary T. Swider ◽  
Rachel K. Ng ◽  
Ramya Varadarajan ◽  
Carey J. Fagerstrom ◽  
Nasser M Rusan
Keyword(s):  
Cell Division ◽  
Tissue Repair ◽  
Complete Separation ◽  
Contractile Ring ◽  
Interacting Protein ◽  
Simultaneous Reduction ◽  
Central Spindle ◽  
Daughter Cells ◽  
Molecular Machinery ◽  
The Brain

AbstractCell division is critical for development, organ growth, and tissue repair. The later stages of cell division include the formation of the microtubule (MT)-rich central spindle in anaphase, which is required to properly define the cell equator, guide the assembly of the acto-myosin contractile ring, and ultimately ensure complete separation and isolation of the two daughter cells via abscission. Much is known about the molecular machinery that forms the central spindle, including proteins needed to generate the antiparallel overlapping interzonal MTs. One critical protein that has garnered great attention is Protein Regulator of Cytokinesis 1 (PRC1), or Fascetto (Feo) in Drosophila, which forms a homodimer to crosslink interzonal MTs, ensuring proper central spindle formation and cytokinesis. Here, we report on a new direct protein interactor and regulator of Feo we named Fascetto Interacting Protein (FIP). Loss of FIP results in a significant reduction in Feo localization, rapid disassembly of interzonal MTs, and several cytokinesis defects. Simultaneous reduction in Feo and FIP results in tumor-like, DNA-filled masses in the brain. In aggregate our data show that FIP functions upstream of, and acts directly on, Feo to ensure fully accurate cell division.

scholarly journals Independent Localization of Plasma Membrane and Chloroplast Components during Eyespot Assembly

2013 ◽  
Vol 12 (9) ◽  
pp. 1258-1270 ◽  
Author(s):  
Telsa M. Mittelmeier ◽  
Mark D. Thompson ◽  
Esra Öztürk ◽  
Carol L. Dieckmann
Keyword(s):  
Plasma Membrane ◽  
Cell Division ◽  
Immunofluorescence Microscopy ◽  
Pigment Granule ◽  
Time Frame ◽  
Chloroplast Envelope ◽  
Basal Bodies ◽  
Content Type ◽  
Daughter Cells ◽  
Mutant Cells

ABSTRACTLike many algae,Chlamydomonas reinhardtiiis phototactic, using two anterior flagella to swim toward light optimal for photosynthesis. The flagella are responsive to signals initiated at the photosensory eyespot, which comprises photoreceptors in the plasma membrane and layers of pigment granules in the chloroplast. Phototaxis depends on placement of the eyespot at a specific asymmetric location relative to the flagella, basal bodies, and bundles of two or four highly acetylated microtubules, termed rootlets, which extend from the basal bodies toward the posterior of the cell. Previous work has shown that the eyespot is disassembled prior to cell division, and new eyespots are assembled in daughter cells adjacent to the nascent four-membered rootlet associated with the daughter basal body (D4), but the chronology of these assembly events has not been determined. Here we use immunofluorescence microscopy to follow assembly and acetylation of the D4 rootlet, localization of individual eyespot components in the plasma membrane or chloroplast envelope, and flagellar emergence during and immediately following cell division. We find that the D4 rootlet is assembled before the initiation of eyespot assembly, which occurs within the same time frame as rootlet acetylation and flagellar outgrowth. Photoreceptors in the plasma membrane are correctly localized in eyespot mutant cells lacking pigment granule layers, and chloroplast components of the eyespot assemble in mutant cells in which photoreceptor localization is retarded. The data suggest that plasma membrane and chloroplast components of the eyespot are independently responsive to a cytoskeletal positioning cue.

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.

scholarly journals The ARP2/3 complex prevents excessive formin activity during cytokinesis

2019 ◽  
Vol 30 (1) ◽  
pp. 96-107 ◽  
Author(s):  
Fung-Yi Chan ◽  
Ana M. Silva ◽  
Joana Saramago ◽  
Joana Pereira-Sousa ◽  
Hailey E. Brighton ◽  
...  
Keyword(s):  
Cell Division ◽  
Caenorhabditis Elegans ◽  
Actin Filament ◽  
Ring Formation ◽  
Contractile Ring ◽  
Present Evidence ◽  
Daughter Cells ◽  
Ring Constriction ◽  
Filament Network ◽  
Kinetics Of

Cytokinesis completes cell division by constriction of an actomyosin contractile ring that separates the two daughter cells. Here we use the early Caenorhabditis elegans embryo to explore how the actin filament network in the ring and the surrounding cortex is regulated by the single cytokinesis formin CYK-1 and the ARP2/3 complex, which nucleate nonbranched and branched filaments, respectively. We show that CYK-1 and the ARP2/3 complex are the predominant F-actin nucleators responsible for generating distinct cortical F-actin architectures and that depletion of either nucleator affects the kinetics of cytokinesis. CYK-1 is critical for normal F-actin levels in the contractile ring, and acute inhibition of CYK-1 after furrow ingression slows ring constriction rate, suggesting that CYK-1 activity is required throughout ring constriction. Surprisingly, although the ARP2/3 complex does not localize in the contractile ring, depletion of the ARP2 subunit or treatment with ARP2/3 complex inhibitor delays contractile ring formation and constriction. We present evidence that the delays are due to an excess in formin-nucleated cortical F-actin, suggesting that the ARP2/3 complex negatively regulates CYK-1 activity. We conclude that the kinetics of cytokinesis are modulated by interplay between the two major actin filament nucleators.

scholarly journals Sas4 links basal bodies to cell division via Hippo signaling

2020 ◽  
Vol 219 (8) ◽  
Author(s):  
Marisa D. Ruehle ◽  
Alexander J. Stemm-Wolf ◽  
Chad G. Pearson
Keyword(s):  
Cell Division ◽  
Signaling Pathway ◽  
Cortical Microtubule ◽  
Cell Cortex ◽  
Basal Bodies ◽  
Hippo Signaling ◽  
Microtubule Organization ◽  
Hippo Signaling Pathway ◽  
Daughter Cells ◽  
Striated Fiber

Basal bodies (BBs) are macromolecular complexes required for the formation and cortical positioning of cilia. Both BB assembly and DNA replication are tightly coordinated with the cell cycle to ensure their accurate segregation and propagation to daughter cells, but the mechanisms ensuring coordination are unclear. The Tetrahymena Sas4/CPAP protein is enriched at assembling BBs, localizing to the core BB structure and to the base of BB-appendage microtubules and striated fiber. Sas4 is necessary for BB assembly and cortical microtubule organization, and Sas4 loss disrupts cell division furrow positioning and DNA segregation. The Hippo signaling pathway is known to regulate cell division furrow position, and Hippo molecules localize to BBs and BB-appendages. We find that Sas4 loss disrupts localization of the Hippo activator, Mob1, suggesting that Sas4 mediates Hippo activity by promoting scaffolds for Mob1 localization to the cell cortex. Thus, Sas4 links BBs with an ancient signaling pathway known to promote the accurate and symmetric segregation of the genome.

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