scholarly journals Actin bundle architecture and mechanics regulate myosin II force generation

2021 ◽  
Author(s):  
Kimberly L. Weirich ◽  
Samantha Stam ◽  
Edwin Munro ◽  
Margaret L. Gardel
Keyword(s):  
Myosin Ii ◽  
Force Generation ◽  
Actin Bundle

scholarly journals Actin bundle architecture and mechanics regulate myosin II force generation

2020 ◽  
Author(s):  
Kimberly L. Weirich ◽  
Samantha Stam ◽  
Ed Munro ◽  
Margaret L. Gardel
Keyword(s):  
Actin Filaments ◽  
Myosin Ii ◽  
Force Generation ◽  
Biological Processes ◽  
Actin Bundle ◽  
Force Magnitude ◽  
Cargo Transport ◽  
Mixed Polarity ◽  
Bundle Compliance ◽  
Filament Spacing

AbstractThe actin cytoskeleton is a soft, structural material that underlies biological processes such as cell division, motility, and cargo transport. The cross-linked actin filaments self-organize into a myriad of architectures, from disordered meshworks to ordered bundles, which are hypothesized to control the actomyosin force generation that regulates cell migration, shape, and adhesion. Here, we use fluorescence microscopy and simulations to investigate how actin bundle architectures with varying polarity, spacing, and rigidity impact myosin II dynamics and force generation. Microscopy reveals that mixed polarity bundles formed by rigid cross-linkers support slow, bidirectional myosin II filament motion, punctuated by periods of stalled motion. Simulations reveal that these locations of stalled myosin motion correspond to sustained, high forces in regions of balanced actin filament polarity. By contrast, mixed polarity bundles formed by compliant, large cross-linkers support fast, bidirectional motion with no traps. Simulations indicate that trap duration is directly related to force magnitude, and that the observed increased velocity corresponds to lower forces resulting from both the increased bundle compliance and filament spacing. Our results indicate that the properties of actin structures regulate the dynamics and magnitude of myosin II forces, highlighting the importance of architecture and mechanics in regulating forces in biological materials.

scholarly journals Tuning molecular motor transport through cytoskeletal filament network organization

2018 ◽  
Author(s):  
Monika Scholz ◽  
Kimberly L. Weirich ◽  
Margaret L. Gardel ◽  
Aaron R. Dinner
Keyword(s):  
Motor Proteins ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Transport Processes ◽  
Force Generation ◽  
Transport Dynamics ◽  
Cytoskeletal Filament ◽  
A Cell ◽  
Cytoskeletal Networks ◽  
Filament Network

The interaction of motor proteins with intracellular filaments is required for transport processes and force generation in cells. Within a cell, crosslinking proteins organize cytoskeletal filaments both temporally and spatially to create dynamic, and structurally diverse networks. The architecture of these networks changes both the mechanics as well as the transport dynamics; however, the effects on transport are less well understood. Here, we compare the transport dynamics of myosin II motor proteins moving on model cytoskeletal networks created by common crosslinking proteins. We observe that motor dynamics change predictably based on the microstructure of the underlying networks and discuss how this can be utilized by cells to achieve specific transport goals.

Regulation of polarity in cells devoid of actin bundle system after treatment with inhibitors of myosin II activity

2008 ◽  
Vol 65 (9) ◽  
pp. 734-746 ◽  
Author(s):  
Maria S. Shutova ◽  
Antonina Y. Alexandrova ◽  
Jury M. Vasiliev
Keyword(s):  
Myosin Ii ◽  
Actin Bundle ◽  
In Cells

scholarly journals Distinct roles of nonmuscle myosin II isoforms for establishing tension and elasticity during cell morphodynamics

2020 ◽  
Author(s):  
Kai Weißenbruch ◽  
Justin Grewe ◽  
Kathrin Stricker ◽  
Laurent Baulesch ◽  
Ulrich S. Schwarz ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Myosin Ii ◽  
Force Generation ◽  
Nonmuscle Myosin ◽  
Cellular Processes ◽  
Scale Bridging ◽  
Crossbridge Cycle ◽  
Nonmuscle Myosin Ii ◽  
Actin Fiber ◽  
And Migration

AbstractNonmuscle myosin II (NM II) is an integral part of essential cellular processes, including adhesion and migration. Mammalian cells express up to three isoforms termed NM IIA, B, and C. We used U2OS cells to create CRISPR/Cas9-based knockouts of all three isoforms and analyzed the phenotypes on homogeneous and micropatterned substrates. We find that NM IIA is essential to build up cellular tension during initial stages of force generation, while NM IIB is necessary to elastically stabilize NM IIA-generated tension. The knockout of NM IIC has no detectable effects. A scale-bridging mathematical model explains our observations by relating actin fiber stability to the molecular rates of the myosin crossbridge cycle. We also find that NM IIA initiates and guides co-assembly of NM IIB into heterotypic minifilaments. We finally use mathematical modeling to explain the different exchange dynamics of NM IIA and B in minifilaments, as measured in FRAP experiments.

scholarly journals Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Daan Vorselen ◽  
Sarah R Barger ◽  
Yifan Wang ◽  
Wei Cai ◽  
Julie A Theriot ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Traction Force ◽  
Light Sheet ◽  
Force Generation ◽  
Actin Dynamics ◽  
Force Microscopy ◽  
Light Sheet Microscopy ◽  
Macrophage Phagocytosis ◽  
Actin Protrusions

Phagocytosis requires rapid actin reorganization and spatially controlled force generation to ingest targets ranging from pathogens to apoptotic cells. How actomyosin activity directs membrane extensions to engulf such diverse targets remains unclear. Here, we combine lattice light-sheet microscopy (LLSM) with microparticle traction force microscopy (MP-TFM) to quantify actin dynamics and subcellular forces during macrophage phagocytosis. We show that spatially localized forces leading to target constriction are prominent during phagocytosis of antibody-opsonized targets. This constriction is largely driven by Arp2/3-mediated assembly of discrete actin protrusions containing myosin 1e and 1f ('teeth') that appear to be interconnected in a ring-like organization. Contractile myosin-II activity contributes to late-stage phagocytic force generation and progression, supporting a specific role in phagocytic cup closure. Observations of partial target eating attempts and sudden target release via a popping mechanism suggest that constriction may be critical for resolving complex in vivo target encounters. Overall, our findings present a phagocytic cup-shaping mechanism that is distinct from cytoskeletal remodeling in 2D cell motility and may contribute to mechanosensing and phagocytic plasticity.

scholarly journals Nonmuscle myosin IIA dynamically guides regulatory light chain phosphorylation and assembly of nonmuscle myosin IIB

2021 ◽  
Author(s):  
Kai Weissenbruch ◽  
Magdalena Fladung ◽  
Justin Grewe ◽  
Laurent Baulesch ◽  
Ulrich Sebastian Schwarz ◽  
...  
Keyword(s):  
Light Chain ◽  
Mammalian Cells ◽  
Myosin Ii ◽  
Regulatory Light Chain ◽  
Force Generation ◽  
Nonmuscle Myosin ◽  
Force Output ◽  
Nonmuscle Myosin Ii ◽  
Phosphorylation Pattern ◽  
Regulatory Light Chain Phosphorylation

Nonmuscle myosin II minifilaments have emerged as central elements for force generation and mechanosensing by mammalian cells. Each minifilament can have a different composition and activity due to the existence of the three nonmuscle myosin II isoforms A, B and C and their respective phosphorylation pattern. We have used CRISPR/Cas9-based knockout cells, quantitative image analysis and mathematical modelling to dissect the dynamic processes that control the formation and activity of heterotypic minifilaments and found a strong asymmetry between isoforms A and B. Loss of NM IIA completely abrogates regulatory light chain phosphorylation and reduces the level of assembled NM IIB. Activated NM IIB preferentially co-assembles into pre-formed NM IIA minifilaments and stabilizes the filament in a force-dependent mechanism. NM IIC is only weakly coupled to these processes. We conclude that NM IIA and B play clearly defined complementary roles during assembly of functional minifilaments. NM IIA is responsible for the formation of nascent pioneer minifilaments. NM IIB incorporates into these and acts as a clutch that limits the force output to prevent excessive NM IIA activity. Together these two isoforms form a balanced system for regulated force generation.

scholarly journals Role of Myosin II in Motility and in Force Generation of DRG Growth Cones

2013 ◽  
Vol 104 (2) ◽  
pp. 477a
Author(s):  
Ladan Amin ◽  
Wasim Amin Sayyad ◽  
Erika Ercolini ◽  
Jelena Ban ◽  
Hiba Sheheitli ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Growth Cones ◽  
Force Generation

scholarly journals Direct visualization of human myosin II force generation using DNA origami-based thick filaments

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Keisuke Fujita ◽  
Masashi Ohmachi ◽  
Keigo Ikezaki ◽  
Toshio Yanagida ◽  
Mitsuhiro Iwaki
Keyword(s):  
Myosin Ii ◽  
Dna Origami ◽  
Force Generation ◽  
Direct Visualization ◽  
Forward Region ◽  
Thin Filaments ◽  
Arm Swing ◽  
Thick Filaments ◽  
Mechanical Unit ◽  
Muscle Myosin

AbstractThe sarcomere, the minimal mechanical unit of muscle, is composed of myosins, which self-assemble into thick filaments that interact with actin-based thin filaments in a highly-structured lattice. This complex imposes a geometric restriction on myosin in force generation. However, how single myosins generate force within the restriction remains elusive and conventional synthetic filaments do not recapitulate the symmetric bipolar filaments in sarcomeres. Here we engineered thick filaments using DNA origami that incorporate human muscle myosin to directly visualize the motion of the heads during force generation in a restricted space. We found that when the head diffuses, it weakly interacts with actin filaments and then strongly binds preferentially to the forward region as a Brownian ratchet. Upon strong binding, the two-step lever-arm swing dominantly halts at the first step and occasionally reverses direction. Our results illustrate the usefulness of our DNA origami-based assay system to dissect the mechanistic details of motor proteins.

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