scholarly journals Microtubules control cellular shape and coherence in amoeboid migrating cells

2019 ◽  
Author(s):  
Aglaja Kopf ◽  
Jörg Renkawitz ◽  
Robert Hauschild ◽  
Irute Girkontaite ◽  
Kerry Tedford ◽  
...  
Keyword(s):  
Cell Shape ◽  
Shape Control ◽  
Complex Geometry ◽  
Control Cell ◽  
Three Dimensional ◽  
Microtubule Organizing Center ◽  
Organizing Center ◽  
A Cell ◽  
Cell Shape Control ◽  
Rate Limit

Cells navigating through tissues face a fundamental challenge: while multiple cellular protrusions explore different paths through the complex geometry of an interstitial matrix the cell needs to avoid becoming too long or ramified, which might ultimately lead to a loss of physical coherence. How a cell surveys its own shape to inform the actomyosin system to retract entangled or stretched protrusions is not understood. Here, we demonstrate that spatially distinct microtubule (MT) dynamics regulate amoeboid cell migration by locally specifying the retraction of explorative protrusions. In migrating dendritic cells (DCs), the microtubule organizing center (MTOC) guides the path through a three dimensional (3D) interstitium and local MT depolymerization in protrusions remote from the MTOC triggers myosin II dependent contractility via the RhoA exchange factor Lfc. Depletion of Lfc leads to aberrant myosin localization, thereby causing two effects that rate-limit locomotion: i) impaired cell edge coordination during path-finding and ii) defective adhesion-resolution. Such compromised cell shape control is particularly hindering when cells navigate through geometrically complex microenvironments, where it leads to entanglement and ultimately fragmentation of the cell body. Our data demonstrate that MTs control cell shape and coherence by locally controlling protrusion-retraction dynamics of the actomyosin system.

scholarly journals Microtubules control cellular shape and coherence in amoeboid migrating cells

2020 ◽  
Vol 219 (6) ◽  
Author(s):  
Aglaja Kopf ◽  
Jörg Renkawitz ◽  
Robert Hauschild ◽  
Irute Girkontaite ◽  
Kerry Tedford ◽  
...  
Keyword(s):  
Cell Shape ◽  
Shape Control ◽  
Microtubule Depolymerization ◽  
Microtubule Organizing Center ◽  
Amoeboid Cell ◽  
Actomyosin Contractility ◽  
Organizing Center ◽  
A Cell ◽  
And Control ◽  
Rate Limit

Cells navigating through complex tissues face a fundamental challenge: while multiple protrusions explore different paths, the cell needs to avoid entanglement. How a cell surveys and then corrects its own shape is poorly understood. Here, we demonstrate that spatially distinct microtubule dynamics regulate amoeboid cell migration by locally promoting the retraction of protrusions. In migrating dendritic cells, local microtubule depolymerization within protrusions remote from the microtubule organizing center triggers actomyosin contractility controlled by RhoA and its exchange factor Lfc. Depletion of Lfc leads to aberrant myosin localization, thereby causing two effects that rate-limit locomotion: (1) impaired cell edge coordination during path finding and (2) defective adhesion resolution. Compromised shape control is particularly hindering in geometrically complex microenvironments, where it leads to entanglement and ultimately fragmentation of the cell body. We thus demonstrate that microtubules can act as a proprioceptive device: they sense cell shape and control actomyosin retraction to sustain cellular coherence.

scholarly journals A contractile and counterbalancing adhesion system controls the 3D shape of crawling cells

2014 ◽  
Vol 205 (1) ◽  
pp. 83-96 ◽  
Author(s):  
Dylan T. Burnette ◽  
Lin Shao ◽  
Carolyn Ott ◽  
Ana M. Pasapera ◽  
Robert S. Fischer ◽  
...  
Keyword(s):  
Cell Shape ◽  
Shape Control ◽  
Three Dimensional ◽  
Focal Adhesions ◽  
Live Cell Microscopy ◽  
Microscopy Data ◽  
Pulling Force ◽  
Cell Shape Control ◽  
Cell Microscopy ◽  
Shape Changes

How adherent and contractile systems coordinate to promote cell shape changes is unclear. Here, we define a counterbalanced adhesion/contraction model for cell shape control. Live-cell microscopy data showed a crucial role for a contractile meshwork at the top of the cell, which is composed of actin arcs and myosin IIA filaments. The contractile actin meshwork is organized like muscle sarcomeres, with repeating myosin II filaments separated by the actin bundling protein α-actinin, and is mechanically coupled to noncontractile dorsal actin fibers that run from top to bottom in the cell. When the meshwork contracts, it pulls the dorsal fibers away from the substrate. This pulling force is counterbalanced by the dorsal fibers’ attachment to focal adhesions, causing the fibers to bend downward and flattening the cell. This model is likely to be relevant for understanding how cells configure themselves to complex surfaces, protrude into tight spaces, and generate three-dimensional forces on the growth substrate under both healthy and diseased conditions.

Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography

1994 ◽  
Vol 52 ◽  
pp. 310-311
Author(s):  
M.B. Braunfeld ◽  
M. Moritz ◽  
B.M. Alberts ◽  
J.W. Sedat ◽  
D.A. Agard
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Vital Role ◽  
Complex Nature ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Nucleation Sites ◽  
Dimensional Reconstruction ◽  
Organizing Center ◽  
Resolution Model

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.

scholarly journals Fierce Competition between Toxoplasma and Chlamydia for Host Cell Structures in Dually Infected Cells

2012 ◽  
Vol 12 (2) ◽  
pp. 265-277 ◽  
Author(s):  
Julia D. Romano ◽  
Catherine de Beaumont ◽  
Jose A. Carrasco ◽  
Karen Ehrenman ◽  
Patrik M. Bavoil ◽  
...  
Keyword(s):  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Productive Infection ◽  
Microtubule Organizing Center ◽  
Nutrient Pools ◽  
Content Type ◽  
Cell Structures ◽  
Organizing Center ◽  
A Cell ◽  
Fierce Competition

ABSTRACTThe prokaryoteChlamydia trachomatisand the protozoanToxoplasma gondii, two obligate intracellular pathogens of humans, have evolved a similarmodus operandito colonize their host cell and salvage nutrients from organelles. In order to gain fundamental knowledge on the pathogenicity of these microorganisms, we have established a cell culture model whereby single fibroblasts are coinfected byC. trachomatisandT. gondii. We previously reported that the two pathogens compete for the same nutrient pools in coinfected cells and thatToxoplasmaholds a significant competitive advantage overChlamydia. Here we have expanded our coinfection studies by examining the respective abilities ofChlamydiaandToxoplasmato co-opt the host cytoskeleton and recruit organelles. We demonstrate that the two pathogen-containing vacuoles migrate independently to the host perinuclear region and rearrange the host microtubular network around each vacuole. However,ToxoplasmaoutcompetesChlamydiato the host microtubule-organizing center to the detriment of the bacterium, which then shifts to a stress-induced persistent state. Solely in cells preinfected withChlamydia, the centrosomes become associated with the chlamydial inclusion, while theToxoplasmaparasitophorous vacuole displays growth defects. Both pathogens fragment the host Golgi apparatus and recruit Golgi elements to retrieve sphingolipids. This study demonstrates that the productive infection by bothChlamydiaandToxoplasmadepends on the capability of each pathogen to successfully adhere to a finely tuned developmental program that aims to remodel the host cell for the pathogen's benefit. In particular, this investigation emphasizes the essentiality of host organelle interception by intravacuolar pathogens to facilitate access to nutrients.

scholarly journals The Arabidopsis SPIKE1 Gene Is Required for Normal Cell Shape Control and Tissue Development

2002 ◽  
Vol 14 (1) ◽  
pp. 101-118 ◽  
Author(s):  
Jin-Long Qiu ◽  
Ross Jilk ◽  
M. David Marks ◽  
Daniel B. Szymanski
Keyword(s):  
Cell Shape ◽  
Normal Cell ◽  
Shape Control ◽  
Tissue Development ◽  
Cell Shape Control
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