scholarly journals Positioning of microtubule organizing centers by cortical pushing and pulling forces

2012 ◽  
Vol 14 (10) ◽  
pp. 105025 ◽  
Author(s):  
Nenad Pavin ◽  
Liedewij Laan ◽  
Rui Ma ◽  
Marileen Dogterom ◽  
Frank Jülicher
Keyword(s):  
Microtubule Organizing Centers ◽  
Pulling Forces ◽  
Pushing And Pulling

scholarly journals Measuring microtubule dynamics

2018 ◽  
Vol 62 (6) ◽  
pp. 725-735 ◽  
Author(s):  
Alexander James Zwetsloot ◽  
Gokhan Tut ◽  
Anne Straube
Keyword(s):  
Small Molecules ◽  
Dynamic Instability ◽  
Microtubule Dynamics ◽  
Regulatory Proteins ◽  
Microtubule Assembly ◽  
Cancer Chemotherapeutics ◽  
Pulling Forces ◽  
Inflammatory Drugs ◽  
And Function ◽  
Pushing And Pulling

Microtubules are key players in cellular self-organization, acting as structural scaffolds, cellular highways, force generators and signalling platforms. Microtubules are polar filaments that undergo dynamic instability, i.e. transition between phases of growth and shrinkage. This allows microtubules to explore the inner space of the cell, generate pushing and pulling forces and remodel themselves into arrays with different geometry and function such as the mitotic spindle. To do this, eukaryotic cells employ an arsenal of regulatory proteins to control microtubule dynamics spatially and temporally. Plants and microorganisms have developed secondary metabolites that perturb microtubule dynamics, many of which are in active use as cancer chemotherapeutics and anti-inflammatory drugs. Here, we summarize the methods used to visualize microtubules and to measure the parameters of dynamic instability to study both microtubule regulatory proteins and the action of small molecules interfering with microtubule assembly and/or disassembly.

scholarly journals Psychophysical basis for maximum pushing and pulling forces: A review and recommendations

2014 ◽  
Vol 44 (2) ◽  
pp. 281-291 ◽  
Author(s):  
Arun Garg ◽  
Thomas Waters ◽  
Jay Kapellusch ◽  
Waldemar Karwowski
Keyword(s):  
Pulling Forces ◽  
Pushing And Pulling

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 Jumping without slipping: leafhoppers (Hemiptera: Cicadellidae) possess special tarsal structures for jumping from smooth surfaces

2017 ◽  
Vol 14 (130) ◽  
pp. 20170022 ◽  
Author(s):  
Christofer J. Clemente ◽  
Hanns Hagen Goetzke ◽  
James M. R. Bullock ◽  
Gregory P. Sutton ◽  
Malcolm Burrows ◽  
...  
Keyword(s):  
High Speed ◽  
Smooth Surfaces ◽  
Velocity Dependence ◽  
Force Measurements ◽  
Acceleration Phase ◽  
Friction Forces ◽  
Anisotropic Friction ◽  
Rapid Control ◽  
Pulling Forces ◽  
Pushing And Pulling

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers ( Philaenus spumarius, Aphrophoridae) and leafhoppers ( Aphrodes bicinctus/makarovi, Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs of Philaenus froghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces. By contrast, Aphrodes leafhoppers took off without their propulsive hind legs slipping, and reached low take-off angles and high velocities on both substrates. This difference in jumping ability from smooth surfaces can be explained not only by the lower acceleration of the long-legged leafhoppers, but also by the presence of 2–9 soft pad-like structures (platellae) on their hind tarsi, which are absent in froghoppers. High-speed videos of jumping showed that platellae contact the surface briefly (approx. 3 ms) during the acceleration phase. Friction force measurements on individual hind tarsi on glass revealed that at low sliding speeds, both pushing and pulling forces were small, and insufficient to explain the recorded jumps. Only when the tarsi were pushed with higher velocities did the contact area of the platellae increase markedly, and high friction forces were produced, consistent with the observed jumps. Our findings show that leafhoppers have special adhesive footpads for jumping from smooth surfaces, which achieve firm grip and rapid control of attachment/detachment by combining anisotropic friction with velocity dependence.

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.

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