Active behavior of the Cytoskeleton

Jülicher, Frank; Kruse, Karsten; Prost, Jacques; Joanny, Jean‐François

doi:10.1016/j.physrep.2007.02.018

Cited by 440 publications

(544 citation statements)

References 63 publications

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“…The mechanical properties of such an acto-myosin gel can be modeled by macroscopic non-linear models which describe the cytoskeleton as a whole [212,236]. A review of these approaches can be found in [177]. Some microscopic stochastic models have also been developped (see for example [225,224]).…”

Section: Actin Filamentsmentioning

confidence: 99%

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Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

2015

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Cells are the elementary units of living organisms, which are able to carry out many vital functions. These functions rely on active processes on a microscopic scale. Therefore, they are strongly out-of-equilibrium systems, which are driven by continuous energy supply. The tasks that have to be performed in order to maintain the cell alive require transportation of various ingredients, some being small, others being large. Intracellular transport processes are able to induce concentration gradients and to carry objects to specific targets. These processes cannot be carried out only by diffusion, as cells may be crowded, and quite elongated on molecular scales. Therefore active transport has to be organized.The cytoskeleton, which is composed of three types of filaments (microtubules, actin and intermediate filaments), determines the shape of the cell, and plays a role in cell motion. It also serves as a road network for a special kind of vehicles, namely the cytoskeletal motors. These molecules can attach to a cytoskeletal filament, perform directed motion, possibly carrying along some cargo, and then detach.It is a central issue to understand how intracellular transport driven by molecular motors is regulated. The interest for this type of question was enhanced when it was discovered that intracellular transport breakdown is one of the signatures of some neuronal diseases like the Alzheimer.We give a survey of the current knowledge on microtubule based intracellular transport. Our review includes on the one hand an overview of biological facts, obtained from experiments, and on the other hand a presentation of some modeling attempts based on cellular automata. We present some background knowledge on the original and variants of the TASEP (Totally Asymmetric Simple Exclusion Process), before turning to more application oriented models. After addressing microtubule based transport in general, with a focus on in vitro experiments, and on cooperative effects in the transportation of large cargos by multiple motors, we concentrate on axonal transport, because of its relevance for neuronal diseases. Some important characteristics of axonal transport is that it takes place in a confined environment; Besides several types of motors are involved, that move in opposite directions. It is a challenge to understand how this bidirectional transport is organized. We review several features that could contribute to the efficiency of bidirectional transport in the axon, including in particular the role of motor-motor interactions and of the dynamics of the underlying microtubule network. Finally, we also discuss some open questions that may be relevant for future research in this field.

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Section: Actin Filamentsmentioning

confidence: 99%

“…An important set of work has been done on this subject using non-linear continuous models. Several reviews have been already published on this subject, to which we refer the reader for further information [177].…”

Section: Dynamics Of Molecular Motors On Filament Networkmentioning

confidence: 99%

Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

2015

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“…An alternative continuum approach is based on polar gels, see for example Kruse et al (2005); Doubrovinski and Kruse (2007) ;Joanny et al (2007);Jülicher et al (2007); CallanJones et al (2008); Kruse (2008, 2010); Callan-Jones and Jülicher (2011); Doubrovinski and Kruse (2011);Du et al (2012) or Ziebert et al (2012). The cytoplasm is modelled as a fluid with an associated vector field indicating the local actin filament orientation.…”

Section: Mathematical Modellingmentioning

confidence: 99%

“…In particular, we will restrict our model to have only one viscoelastic relaxation timescale and employ an upper-convected Maxwell model to describe the rheology of the actin network. These modelling assumptions are supported by Jülicher et al (2007) who use a convected Maxwell model to describe the actin network, although their governing equations are more complicated because the rheology is coupled to a polarization field for the actin fibres. The lamellipod is described as an upper-convected Maxwell fluid in Rubinstein et al (2009).…”

Section: Model Formulationmentioning

confidence: 99%

On a poroviscoelastic model for cell crawling

et al. 2014

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In this paper a minimal, one-dimensional, two-phase, viscoelastic, reactive, flow model for a crawling cell is presented. Two-phase models are used with a variety of constitutive assumptions in the literature to model cell motility. We use an upperconvected Maxwell model and demonstrate that even the simplest of two-phase, viscoelastic models displays features relevant to cell motility. We also show care must be exercised in choosing parameters for such models as a poor choice can lead to an ill-posed problem. A stability analysis reveals that the initially stationary, spatially uniform strip of cytoplasm starts to crawl in response to a perturbation which breaks the symmetry of the network volume fraction or network stress. We also demonstrate numerically that there is a steady travelling-wave solution in which the crawling velocity has a bell-shaped dependence on adhesion strength, in agreement with biological observation.

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“…On the other hand, significant progress has been made in the study of the dynamics of a single contractile bundle or stress fiber 2,4,11,14 and in modeling actin-myosin interaction in solution. 37,52,55 The cell contractility model of Deshpande et al 18,19 addresses the accumulation of myosin contractility and stress fibers as a function of cytoskeletal resistance. The underlying idea in the model can be described as follows: A general cytoskeletal contractility pervades the cell.…”

Section: Stress Fiber Patterns From Continuum Modelsmentioning

confidence: 99%

Band-like Stress Fiber Propagation in a Continuum and Implications for Myosin Contractile Stresses

2009

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Abstract-Stress fibers are band-like features that form with sarcomere-like actin and myosin arrangement between cell regions, resisting myosin contractility. We consider three aspects of stress fiber formation: (1) they form by cytoskeletal actin-myosin interaction when myosin contractile forces are resisted, (2) they propagate in a band-like manner, and (3) they maintain a level of stress and material continuity with the cytoskeleton. This suggests that any description of myosin force should capture the band-like propagation of stress fibers within the constraints of a continuum model. Recent studies describe myosin force as increasing proportional to the cytoskeletal resistance in that direction, but do not capture the band-like propagation of myosin stresses in a continuum. While the spreading of myosin stresses in continuum models is commonly attributed to the elliptic nature of continuum equations, we show that it comes from an incomplete description of the myosin force. Qualitative observations of cytoskeletal actin-myosin interaction indicate the interaction to be 'zipper-like'; myosin contractile forces get transmitted by bending actin filaments in directions away from that of the cytoskeletal resistance. A simple coarse-grained implementation of the lateral myosin forces that arise from the zippering action reproduces band-like stress propagation within a continuum model for the first time. This model also shows actin packing into the stress channel and its propagation along the edge for square and triangular constrained cells; features not captured earlier. Physically, the lateral contractile forces prevent stress spreading by balancing perpendicular shear forces that arise when stress channels through a continuum. Mathematically, these forces render the continuum stress equation hyperbolic. This paper presents a theoretical argument, based on continuum mechanics principles, that it is the zippering actin-myosin action that allows for band-like stress fiber propagation within a coarse-grained cytoskeletal continuum, and that any visualization of the cytoskeletal stress field should account for lateral contractile forces accompanying the much-acknowledged contractile force along a stress fiber.

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Active behavior of the Cytoskeleton

Cited by 440 publications

References 63 publications

Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

On a poroviscoelastic model for cell crawling

Band-like Stress Fiber Propagation in a Continuum and Implications for Myosin Contractile Stresses

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