scholarly journals Centrosome centering and decentering by microtubule network rearrangement

2016 ◽  
Vol 27 (18) ◽  
pp. 2833-2843 ◽  
Author(s):  
Gaëlle Letort ◽  
Francois Nedelec ◽  
Laurent Blanchoin ◽  
Manuel Théry
Keyword(s):  
Molecular Motors ◽  
Cell Polarization ◽  
Cell Cortex ◽  
Cell Periphery ◽  
Microtubule Network ◽  
Abrupt Transition ◽  
External Cues ◽  
Pulling Forces ◽  
Number Dynamics ◽  
Pushing And Pulling

The centrosome is positioned at the cell center by pushing and pulling forces transmitted by microtubules (MTs). Centrosome decentering is often considered to result from asymmetric, cortical pulling forces exerted in particular by molecular motors on MTs and controlled by external cues affecting the cell cortex locally. Here we used numerical simulations to investigate the possibility that it could equally result from the redistribution of pushing forces due to a reorientation of MTs. We first showed that MT gliding along cell edges and pivoting around the centrosome regulate MT rearrangement and thereby direct the spatial distribution of pushing forces, whereas the number, dynamics, and stiffness of MTs determine the magnitude of these forces. By modulating these parameters, we identified different regimes, involving both pushing and pulling forces, characterized by robust centrosome centering, robust off-centering, or “reactive” positioning. In the last-named conditions, weak asymmetric cues can induce a misbalance of pushing and pulling forces, resulting in an abrupt transition from a centered to an off-centered position. Taken together, these results point to the central role played by the configuration of the MTs on the distribution of pushing forces that position the centrosome. We suggest that asymmetric external cues should not be seen as direct driver of centrosome decentering and cell polarization but instead as inducers of an effective reorganization of the MT network, fostering centrosome motion to the cell periphery.

scholarly journals Centrosome centering and Decentering by microtubule network rearrangement

2016 ◽  
Author(s):  
Gaëlle Letort ◽  
Francois Nedelec ◽  
Laurent Blanchoin ◽  
Manuel Théry
Keyword(s):  
Molecular Motors ◽  
Cell Polarization ◽  
Cell Cortex ◽  
Cell Periphery ◽  
Microtubule Network ◽  
Abrupt Transition ◽  
External Cues ◽  
Pulling Forces ◽  
Number Dynamics ◽  
Pushing And Pulling

AbstractThe centrosome is positioned at the cell center by pushing and pulling forces transmitted by microtubules (MTs). Centrosome decentering is often considered to result from asymmetric, cortical pulling forces exerted in particular by molecular motors on MTs, and controlled by external cues affecting the cell cortex locally. Here we used numerical simulations to investigate the possibility that it could equally result from the redistribution of pushing forces due to a reorientation of MTs. We first showed that MT gliding along cell edges and pivoting around the centrosome regulate MT rearrangement and thereby direct the spatial distribution of pushing forces, while the number, dynamics and stiffness of MTs determine the magnitude of these forces. By modulating these parameters, we identified different regimes, involving both pushing and pulling forces, characterized either by robust centrosome centering, robust off-centering or “reactive” positioning. In those latter conditions weak asymmetric cues can induce a misbalance of pushing and pulling forces resulting in an abrupt transition from a centered to an off-centered position. Altogether these results point at the central role played by the configuration of the MTs on the distribution of pushing forces that position the centrosome. We suggest that asymmetric external cues should not be seen as direct driver of centrosome decentering and cell polarization, but rather as inducers of an effective reorganization of the MT network, fostering centrosome motion to the cell periphery.

scholarly journals Centering and Shifting of Centrosomes in Cells

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1351 ◽  
Author(s):  
Anton V. Burakov ◽  
Elena S. Nadezhdina
Keyword(s):  
Primary Cilia ◽  
Molecular Mechanisms ◽  
Apical Cell ◽  
Cell Polarization ◽  
Point Of View ◽  
Cell Cortex ◽  
External Cues ◽  
Intracellular Vesicles ◽  
Functional Point

Centrosomes have a nonrandom localization in the cells: either they occupy the centroid of the zone free of the actomyosin cortex or they are shifted to the edge of the cell, where their presence is justified from a functional point of view, for example, to organize additional microtubules or primary cilia. This review discusses centrosome placement options in cultured and in situ cells. It has been proven that the central arrangement of centrosomes is due mainly to the pulling microtubules forces developed by dynein located on the cell cortex and intracellular vesicles. The pushing forces from dynamic microtubules and actomyosin also contribute, although the molecular mechanisms of their action have not yet been elucidated. Centrosomal displacement is caused by external cues, depending on signaling, and is drawn through the redistribution of dynein, the asymmetrization of microtubules through the capture of their plus ends, and the redistribution of actomyosin, which, in turn, is associated with basal-apical cell polarization.

scholarly journals Assembly and Activity of the WASH Molecular Machine: Distinctive Features at the Crossroads of the Actin and Microtubule Cytoskeletons

2021 ◽  
Vol 9 ◽  
Author(s):  
Artem I. Fokin ◽  
Alexis M. Gautreau
Keyword(s):  
Cell Cortex ◽  
Membrane Remodeling ◽  
Distinctive Features ◽  
Actin Networks ◽  
Capping Protein ◽  
Endosomal Membrane ◽  
Pulling Forces ◽  
Endosomal Membranes ◽  
Privileged Site ◽  
Pushing And Pulling

The Arp2/3 complex generates branched actin networks at different locations of the cell. The WASH and WAVE Nucleation Promoting Factors (NPFs) activate the Arp2/3 complex at the surface of endosomes or at the cell cortex, respectively. In this review, we will discuss how these two NPFs are controlled within distinct, yet related, multiprotein complexes. These complexes are not spontaneously assembled around WASH and WAVE, but require cellular assembly factors. The centrosome, which nucleates microtubules and branched actin, appears to be a privileged site for WASH complex assembly. The actin and microtubule cytoskeletons are both responsible for endosome shape and membrane remodeling. Motors, such as dynein, pull endosomes and extend membrane tubules along microtubule tracks, whereas branched actin pushes onto the endosomal membrane. It was recently uncovered that WASH assembles a super complex with dynactin, the major dynein activator, where the Capping Protein (CP) is exchanged from dynactin to the WASH complex. This CP swap initiates the first actin filament that primes the autocatalytic nucleation of branched actin at the surface of endosomes. Possible coordination between pushing and pulling forces in the remodeling of endosomal membranes is discussed.

scholarly journals F-actin asymmetry and the endoplasmic reticulum–associated TCC-1 protein contribute to stereotypic spindle movements in the Caenorhabditis elegans embryo

2013 ◽  
Vol 24 (14) ◽  
pp. 2201-2215 ◽  
Author(s):  
Christian W. H. Berends ◽  
Javier Muñoz ◽  
Vincent Portegijs ◽  
Ruben Schmidt ◽  
Ilya Grigoriev ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Caenorhabditis Elegans ◽  
Coiled Coil ◽  
Meiotic Spindle ◽  
Cell Cortex ◽  
Endoplasmic Reticulum Membrane ◽  
Cell Periphery ◽  
Α Subunit ◽  
Spindle Positioning ◽  
Pulling Forces

The microtubule spindle apparatus dictates the plane of cell cleavage in animal cells. During development, dividing cells control the position of the spindle to determine the size, location, and fate of daughter cells. Spindle positioning depends on pulling forces that act between the cell periphery and astral microtubules. This involves dynein recruitment to the cell cortex by a heterotrimeric G-protein α subunit in complex with a TPR-GoLoco motif protein (GPR-1/2, Pins, LGN) and coiled-coil protein (LIN-5, Mud, NuMA). In this study, we searched for additional factors that contribute to spindle positioning in the one-cell Caenorhabditis elegans embryo. We show that cortical actin is not needed for Gα–GPR–LIN-5 localization and pulling force generation. Instead, actin accumulation in the anterior actually reduces pulling forces, possibly by increasing cortical rigidity. Examining membrane-associated proteins that copurified with GOA-1 Gα, we found that the transmembrane and coiled-coil domain protein 1 (TCC-1) contributes to proper spindle movements. TCC-1 localizes to the endoplasmic reticulum membrane and interacts with UNC-116 kinesin-1 heavy chain in yeast two-hybrid assays. RNA interference of tcc-1 and unc-116 causes similar defects in meiotic spindle positioning, supporting the concept of TCC-1 acting with kinesin-1 in vivo. These results emphasize the contribution of membrane-associated and cortical proteins other than Gα–GPR–LIN-5 in balancing the pulling forces that position the spindle during asymmetric cell division.

scholarly journals Dynactin binding to tyrosinated microtubules promotes centrosome centration in C. elegans by enhancing dynein-mediated organelle transport

2017 ◽  
Author(s):  
Daniel José Barbosa ◽  
Joana Duro ◽  
Dhanya K. Cheerambathur ◽  
Bram Prevo ◽  
Ana Xavier Carvalho ◽  
...  
Keyword(s):  
Binding Activity ◽  
Organelle Transport ◽  
Cell Cortex ◽  
Cell Periphery ◽  
Animal Cells ◽  
Spindle Positioning ◽  
C Elegans ◽  
Pulling Forces

ABSTRACTThe microtubule-based motor dynein generates pulling forces for centrosome centration and mitotic spindle positioning in animal cells. How the essential dynein activator dynactin regulates these functions of the motor is incompletely understood. Here, we dissect the role of dynactin’s microtubule binding activity, located in p150’s CAP-Gly domain and an adjacent basic patch, in the C. elegans zygote. Using precise mutants engineered by genome editing, we show that microtubule tip tracking of dynein-dynactin is dispensable for targeting the motor to the cell cortex and for generating cortical pulling forces. Instead, p150 CAP-Gly mutants inhibit cytoplasmic pulling forces responsible for centration of centrosomes and attached pronuclei. The centration defects are mimicked by mutations of the C-terminal tyrosine of α-tubulin, and both p150 CAP-Gly and tubulin tyrosination mutants decrease the frequency of organelle transport from the cell periphery towards centrosomes during centration. In light of recent work on dynein-dynactin motility in vitro, our results suggest that p150 GAP-Gly domain binding to tyrosinated microtubules promotes initiation of dynein-mediated organelle transport in the dividing embryo, and that this function of dynactin is important for generating robust cytoplasmic pulling forces for centrosome centration.

scholarly journals Posttranslational modification of distinct microtubule subpopulations during cell polarization and differentiation in the mouse preimplantation embryo.

1989 ◽  
Vol 108 (2) ◽  
pp. 543-551 ◽  
Author(s):  
E Houliston ◽  
B Maro
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Types ◽  
Cell Polarization ◽  
Cell Cortex ◽  
Microtubule Network ◽  
Alpha Tubulin ◽  
Cell Biol ◽  
Distinct Cell ◽  
The Difference

During the course of preimplantation development, the cells of the mouse embryo undergo both a major subcellular reorganization (at the time of compaction) and, subsequently, a process of differentiation as the phenotypes of trophectoderm and inner cell mass cell types diverge. We have used antibodies specific for tyrosinated (Kilmartin, J. V., B. Wright, and C. Milstein. 1982. J. Cell Biol. 93:576-582) and acetylated (Piperno, G., and M. T. Fuller. 1985. J. Cell Biol. 101:2085-2094) alpha-tubulin in immunofluorescence studies and found that subsets of microtubules can be distinguished within and between cells during the course of these events. Whereas all microtubules contained tyrosinated alpha-tubulin, acetylated alpha-tubulin was detected only in a subpopulation, located predominantly in the cell cortices. Striking differences developed between the distribution of the two populations during the course of development. Firstly, whereas the microtubule population as a whole tends to redistribute towards the apical domain of cells as they polarize during compaction (Houliston, E., S. J. Pickering, and B. Maro. 1987. J. Cell Biol. 104:1299-1308), the microtubules recognized by the antiacetylated alpha-tubulin antibody became enriched in the basal part of the cell cortex. After asymmetric division of polarized cells to generate two distinct cell types (termed inside and outside cells) we found that, despite the relative abundance of microtubules in outside cells, acetylated microtubules accumulated preferentially in inside cells. Treatment with nocodazole demonstrated that within each cell type acetylated microtubules were the more stable ones; however, the difference in composition of the microtubule network between cell types was not accompanied by a greater stability of the microtubule network in inside cells.

scholarly journals Membrane-mediated interactions induce spontaneous filament bundling

2018 ◽  
Author(s):  
Afshin Vahid ◽  
George Dadunashvili ◽  
Timon Idema
Keyword(s):  
Actin Filaments ◽  
Living Cells ◽  
Natural Consequence ◽  
Microtubule Network ◽  
Parallel Structures ◽  
Pulling Forces ◽  
Membrane Protrusions ◽  
A Cell ◽  
Cytoskeletal Elements ◽  
Pushing And Pulling

AbstractThe plasma membrane and cytoskeleton of living cells are closely coupled dynamical systems. Internal cytoskeletal elements such as actin filaments and microtubules continually exert forces on the membrane, resulting in the formation of membrane protrusions. In this paper we investigate the interplay between the shape of a cell distorted by pushing and pulling forces generated by microtubules and the resulting rearrangement of the microtubule network. From analytical calculations, we find that two microtubules that deform the vesicle can both attract or repel each other, depending on their angular separations and the direction of the imposed forces. We also show how the existence of attractive interactions between multiple microtubules can be deduced analytically, and further explore general interactions through Monte Carlo simulations. Our results suggest that the commonly reported parallel structures of microtubules in both biological and artificial systems can be a natural consequence of membrane mediated interactions.

scholarly journals Microtubules orchestrate local translation to enable cardiac growth

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Emily A. Scarborough ◽  
Keita Uchida ◽  
Maria Vogel ◽  
Noa Erlitzki ◽  
Meghana Iyer ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Cell Periphery ◽  
Local Translation ◽  
Microtubule Network ◽  
Critical Determinant ◽  
Translation Rate ◽  
Cardiac Growth ◽  
Translational Machinery ◽  
Microtubule Motor ◽  
Discrete Domains

AbstractHypertension, exercise, and pregnancy are common triggers of cardiac remodeling, which occurs primarily through the hypertrophy of individual cardiomyocytes. During hypertrophy, stress-induced signal transduction increases cardiomyocyte transcription and translation, which promotes the addition of new contractile units through poorly understood mechanisms. The cardiomyocyte microtubule network is also implicated in hypertrophy, but via an unknown role. Here, we show that microtubules are indispensable for cardiac growth via spatiotemporal control of the translational machinery. We find that the microtubule motor Kinesin-1 distributes mRNAs and ribosomes along microtubule tracks to discrete domains within the cardiomyocyte. Upon hypertrophic stimulation, microtubules redistribute mRNAs and new protein synthesis to sites of growth at the cell periphery. If the microtubule network is disrupted, mRNAs and ribosomes collapse around the nucleus, which results in mislocalized protein synthesis, the rapid degradation of new proteins, and a failure of growth, despite normally increased translation rates. Together, these data indicate that mRNAs and ribosomes are actively transported to specific sites to facilitate local translation and assembly of contractile units, and suggest that properly localized translation – and not simply translation rate – is a critical determinant of cardiac hypertrophy. In this work, we find that microtubule based-transport is essential to couple augmented transcription and translation to productive cardiomyocyte growth during cardiac stress.

The Kar3p and Kip2p motors function antagonistically at the spindle poles to influence cytoplasmic microtubule numbers

1998 ◽  
Vol 111 (3) ◽  
pp. 295-301 ◽  
Author(s):  
A. Huyett ◽  
J. Kahana ◽  
P. Silver ◽  
X. Zeng ◽  
W.S. Saunders
Keyword(s):  
Molecular Motors ◽  
Motor Proteins ◽  
Single Gene ◽  
Intermediate Phenotype ◽  
Microtubule Network ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoplasmic Microtubule ◽  
Spindle Poles ◽  
Microtubule Motors ◽  
Microtubule Growth

Microtubules provide the substrate for intracellular trafficking by association with molecular motors of the kinesin and dynein superfamilies. Motor proteins are generally thought to function as force generating units for transport of various cargoes along the microtubule polymer. Recent work suggests additional roles for motor proteins in changing the structure of the microtubule network itself. We report here that in the budding yeast Saccharomyces cerevisiae microtubule motors have antagonistic effects on microtubule numbers and lengths. As shown previously, loss of the Kar3p motor stimulates cytoplasmic microtubule growth while loss of Kip2p leads to a sharp reduction in cytoplasmic microtubule numbers. Loss of both the Kip2p and Kar3p motors together in the same cell produces an intermediate phenotype, suggesting that these two motors act in opposition to control cytoplasmic microtubule density. A Kip2p-GFP fusion from single gene expression is most concentrated at the spindle poles, as shown previously for an epitope tagged Kar3p-HA, suggesting both of these motors act from the minus ends of the microtubules to influence microtubule numbers.

Internalization of activated platelet-derived growth factor receptor-phosphatidylinositol-3' kinase complexes: potential interactions with the microtubule cytoskeleton

1993 ◽  
Vol 13 (10) ◽  
pp. 6052-6063
Author(s):  
R Kapeller ◽  
R Chakrabarti ◽  
L Cantley ◽  
F Fay ◽  
S Corvera
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinases ◽  
Growth Factor Receptor ◽  
Endocytic Pathway ◽  
Platelet Derived Growth Factor ◽  
Cell Periphery ◽  
Perinuclear Region ◽  
High Concentration ◽  
Microtubule Cytoskeleton ◽  
Microtubule Network

Phosphatidylinositol (PI)-3' kinase catalyzes the formation of PI 3,4-diphosphate and PI 3,4,5-triphosphate in response to stimulation of cells by platelet-derived growth factor (PDGF). Here we report that tyrosine-phosphorylated PDGF receptors, the p85 subunit of PI-3' kinase (p85), and activated PI-3' kinase are found in isolated clathrin-coated vesicles within 2 min of exposure of cells to PDGF, indicating that both receptor and activated PI-3' kinase enter the endocytic pathway. Immunofluorescence analysis of p85 in serum-starved cells revealed a punctate/reticular staining pattern, concentrated in the perinuclear region and displaying high focal concentration at the centrosome. In addition, partial coalignment of p85 with microtubules was observed after optical sectioning microscopy and image reconstruction. The association of p85 with the microtubule network was further evidenced by the microtubule-depolymerizing drug nocodazole, which caused a redistribution of p85 from the perinuclear region to the cell periphery. Interestingly, the most significant effect of PDGF on the distribution of p85 was an increase in the staining intensity of this protein in the perinuclear region, and this effect was eliminated by prior treatment of cells with nocodazole. These results suggest that PDGF receptor-p85 complexes internalize and transit in association with the microtubule cytoskeleton. In addition, the high concentration of p85 in intracellular structures in the absence of PDGF stimulation suggests additional roles for this protein independent of its association with receptor tyrosine kinases.

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