Assemblies of F-actin and myosin-II minifilaments: steric hindrance and stratification at the membrane cortex

Das, Amit; Bhat, Abrar; Sknepnek, Rastko; Koester, Darius V.; Mayor, Satyajit; Rao, Madan

doi:10.1101/656082

Cited by 4 publications

(3 citation statements)

References 48 publications

(47 reference statements)

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“…Neither bundles nor asters form when the unloaded motor velocity v 0 exceeds a critical value, in which case a diffuse isotropic phase is observed. Our asters and bundles share core characteristics with those observed in experiments, such as the antiparallel alignment of filaments in sarcomeric bundles and stress fibers [31] and clusters of radial filaments in vitro [1,32] (Fig. S1).…”

supporting

confidence: 72%

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

et al. 2022

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Biological materials, such as the actin cytoskeleton, exhibit remarkable structural adaptability to various external stimuli by consuming different amounts of energy. In this Letter, we use methods from large deviation theory to identify a thermodynamic control principle for structural transitions in a model cytoskeletal network. Specifically, we demonstrate that biasing the dynamics with respect to the work done by nonequilibrium components effectively renormalizes the interaction strength between such components, which can eventually result in a morphological transition. Our work demonstrates how a thermodynamic quantity can be used to renormalize effective interactions, which in turn can tune structure in a predictable manner, suggesting a thermodynamic principle for the control of cytoskeletal structure and dynamics.

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supporting

confidence: 72%

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

et al. 2022

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“…The bundle and aster structures in this model system share the core characteristics with the in vivo structures observed in experiments, such as the antiparallel alignment of filaments in sarcomeric bundles and stress fibers [32] and the radial puncta in actomyosin networks [33]. The presence of similar experimental structures suggests that this bundle-aster transition has biological relevance.…”

Section: Motor Rigidity Controls Structuresupporting

confidence: 58%

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

Lamtyugina¹,

Qiu²,

Fodor³

et al. 2021

Preprint

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We aim to identify the control principles governing the adaptable formation of non-equilibrium structures in actomyosin networks. We build a phenomenological model and predict that biasing the energy dissipated by molecular motors should effectively renormalize the motor-mediated interactions between actin filaments. Indeed, using methods from large deviation theory, we demonstrate that biasing energy dissipation is equivalent to modulating the motor rigidity and results in an aster-tobundle transition. From the simulation statistics, we extract a relation between the biasing parameter and the corresponding normalized motor rigidity. This work elucidates the relationship between energy dissipation, effective interactions, and pattern formation in active biopolymer networks, providing a control principle of cytoskeletal structure and dynamics.The actin cytoskeleton is a paradigm of adaptive biomaterials that efficiently and accurately sense various environmental inputs and respond to them [1]. This adaptive behavior is in part enabled by the rich non-equilibrium morphological states that the actin cytoskeleton can adopt by varying, for example, component concentrations [2, 3]. Indeed, actin networks have been observed in the form of contractile bundles [4], branched lamellipodium [5], and contractile mesh structures [6], among many others. These varied non-equilibrium morphological states control important biophysical properties of the cell, such as its structural integrity, motility, and signaling [7, 8].Efforts to unravel the driving forces responsible for sustaining the various non-equilibrium morphological states have relied on experiments [2, 9-13], simulations [14,15], and theory [16] of model systems with limited cytoskeletal elements. For instance, a model system composed of actin filaments and myosin motors transitions between actin bundles and asters when the actin filament lengths and myosin concentrations are varied [9]. Recent in vitro experiments with light-sensitive motors demonstrate that actin networks can be patterned when the motors are activated by light [11]. Microtubule-kinesin systems have also been shown to exhibit remarkable structural changes as component concentrations are tuned [17]. However, a thermodynamic understanding of the underlying control principles is yet to be achieved.Recent work on simple active matter systems has provided pointers to how such a non-equilibrium thermodynamic control framework could be developed using dynamical bias [18][19][20][21]. Specifically, the seminal flocking transition in a Vicsek-like model is typically achieved

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“…4, A and B; Video S9). This could be due to the lack of free actin filaments and mechanical tension inside the clusters, forcing excess myosin filaments to leave the condensed detection zone either by detaching from the cluster or by stacking up to form three-dimensional structures above the membrane-tethered actin network as observed earlier (4,40,43).…”

Section: Myosin II Filament Flows Generate Transiently Stable Contractile Zonesmentioning

confidence: 93%

Myosin II Filament Dynamics in Actin Networks Revealed with Interferometric Scattering Microscopy

Mosby

Hundt

Young

et al. 2020

Biophysical Journal

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The plasma membrane and the underlying cytoskeletal cortex constitute active platforms for a variety of cellular processes. Recent work has shown that the remodeling acto-myosin network modifies local membrane organization, but the molecular details are only partly understood because of difficulties with experimentally accessing the relevant time and length scales. Here, we use interferometric scattering microscopy to investigate a minimal acto-myosin network linked to a supported lipid bilayer membrane. Using the magnitude of the interferometric contrast, which is proportional to molecular mass, and fast acquisition rates, we detect and image individual membrane-attached actin filaments diffusing within the acto-myosin network and follow individual myosin II filament dynamics. We quantify myosin II filament dwell times and processivity as functions of ATP concentration, providing experimental evidence for the predicted ensemble behavior of myosin head domains. Our results show how decreasing ATP concentrations lead to both increasing dwell times of individual myosin II filaments and a global change from a remodeling to a contractile state of the acto-myosin network.

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Assemblies of F-actin and myosin-II minifilaments: steric hindrance and stratification at the membrane cortex

Cited by 4 publications

References 48 publications

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

Thermodynamic Control of Activity Patterns in Cytoskeletal Networks

Myosin II Filament Dynamics in Actin Networks Revealed with Interferometric Scattering Microscopy

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