scholarly journals Polarization of Myosin II refines tissue material properties to buffer mechanical stress

2017 ◽  
Author(s):  
Maria Duda ◽  
Nargess Khalilgharibi ◽  
Nicolas Carpi ◽  
Anna Bove ◽  
Matthieu Piel ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Rho Kinase ◽  
Mechanical Damage ◽  
Mechanical Forces ◽  
Physical Damage ◽  
Tissue Responses ◽  
Adult Organism ◽  
Induced Changes

SummaryAs tissues develop, they are subjected to a variety of mechanical forces. Some of these forces, such as those required for morphogenetic movements, are instrumental to the development and sculpting of tissues. However, mechanical forces can also lead to accumulation of substantial tensile stress, which if maintained, can result in tissue damage and impair tissue function. Despite our extensive understanding of force-guided morphogenesis, we have only a limited understanding of how tissues prevent further morphogenesis, once shape is determined after development. Buffering forces to prevent cellular changes in response to fluctuations of mechanical stress is critical during the lifetime of an adult organism. Here, through the development of a novel tissue-stretching device, we uncover a mechanosensitive pathway that regulates tissue responses to mechanical stress through the polarization of Myosin II across the tissue. Mechanistically, this process is independent of conserved Rho-kinase signaling but is mediated by force-induced linear actin polymerization and depolymerization via the formin Diaphanous and actin severing protein Cofilin, respectively. Importantly, these stretch-induced actomyosin cables stiffen the tissue to limit changes in cell shape and to protect the tissue from further mechanical damage prior to stress dissipation. This tissue rigidification prevents fractures in the tissue from propagating by confining the damage locally to the injured cells. Overall this mechanism of force-induced changes in tissue mechanical properties provides a general model of force buffering that rapidly protects tissues from physical damage to preserve tissue shape.

scholarly journals Nonmuscle myosin II is responsible for maintaining endothelial cell basal tone and stress fiber integrity

2008 ◽  
Vol 295 (4) ◽  
pp. C994-C1006 ◽  
Author(s):  
Zoe M. Goeckeler ◽  
Paul C. Bridgman ◽  
Robert B. Wysolmerski
Keyword(s):  
Endothelial Cell ◽  
Light Chain ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Rho Kinase ◽  
Specific Inhibitor ◽  
Isometric Tension ◽  
Stress Fiber ◽  
Tension Development ◽  
Basal Tone

Cultured confluent endothelial cells exhibit stable basal isometric tone associated with constitutive myosin II regulatory light chain (RLC) phosphorylation. Thrombin treatment causes a rapid increase in isometric tension concomitant with myosin II RLC phosphorylation, actin polymerization, and stress fiber reorganization while inhibitors of myosin light chain kinase (MLCK) and Rho-kinase prevent these responses. These findings suggest a central role for myosin II in the regulation of endothelial cell tension. The present studies examine the effects of blebbistatin, a specific inhibitor of myosin II activity, on basal tone and thrombin-induced tension development. Although blebbistatin treatment abolished basal tension, this was accompanied by an increase in myosin II RLC phosphorylation. The increase in RLC phosphorylation was Ca2+ dependent and mediated by MLCK. Similarly, blebbistatin inhibited thrombin-induced tension without interfering with the increase in RLC phosphorylation or in F-actin polymerization. Blebbistatin did prevent myosin II filament incorporation and association with polymerizing or reorganized actin filaments leading to the disappearance of stress fibers. Thus the inhibitory effects of blebbistatin on basal tone and induced tension are consistent with a requirement for myosin II activity to maintain stress fiber integrity.

scholarly journals Rho GTPase and Shroom direct planar polarized actomyosin contractility during convergent extension

2014 ◽  
Vol 204 (4) ◽  
pp. 575-589 ◽  
Author(s):  
Sérgio de Matos Simões ◽  
Avantika Mainieri ◽  
Jennifer A. Zallen
Keyword(s):  
Rho Gtpase ◽  
Binding Protein ◽  
Myosin Ii ◽  
Rho Kinase ◽  
Actin Binding ◽  
Mechanical Forces ◽  
Convergent Extension ◽  
Planar Polarity ◽  
Axis Elongation ◽  
Actomyosin Contraction

Actomyosin contraction generates mechanical forces that influence cell and tissue structure. During convergent extension in Drosophila melanogaster, the spatially regulated activity of the myosin activator Rho-kinase promotes actomyosin contraction at specific planar cell boundaries to produce polarized cell rearrangement. The mechanisms that direct localized Rho-kinase activity are not well understood. We show that Rho GTPase recruits Rho-kinase to adherens junctions and is required for Rho-kinase planar polarity. Shroom, an asymmetrically localized actin- and Rho-kinase–binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling. In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension. These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.

scholarly journals Two distinct cytoplasmic regions of the β2 integrin chain regulate RhoA function during phagocytosis

2006 ◽  
Vol 172 (7) ◽  
pp. 1069-1079 ◽  
Author(s):  
Agnès Wiedemann ◽  
Jayesh C. Patel ◽  
Jenson Lim ◽  
Andy Tsun ◽  
Yvette van Kooyk ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Rho Gtpase ◽  
Myosin Ii ◽  
Rho Kinase ◽  
Cytoplasmic Domain ◽  
Β2 Integrin ◽  
Proximal Half ◽  
Complement Receptor 3 ◽  
Phagocytic Uptake ◽  
Shed Light

αMβ2 integrins mediate phagocytosis of opsonized particles in a process controlled by RhoA, Rho kinase, myosin II, Arp2/3, and actin polymerization. αMβ2, Rho, Arp2/3, and F-actin accumulate underneath bound particles; however, the mechanism regulating Rho function during αMβ2-mediated phagocytosis is poorly understood. We report that the binding of C3bi-opsonized sheep red blood cells (RBCs) to αMβ2 increases Rho-GTP, but not Rac-GTP, levels. Deletion of the cytoplasmic domain of β2, but not of αM, abolished Rho recruitment and activation, as well as phagocytic uptake. Interestingly, a 16–amino acid (aa) region in the membrane-proximal half of the β2 cytoplasmic domain was necessary for activating Rho. Three COOH-terminal residues (aa 758–760) were essential for β2-induced accumulation of Rho at complement receptor 3 (CR3) phagosomes. Activation of Rho was necessary, but not sufficient, for its stable recruitment underneath bound particles or for uptake. However, recruitment of active Rho was sufficient for phagocytosis. Our data shed light on the mechanism of outside-in signaling, from ligated integrins to the activation of Rho GTPase signaling.

scholarly journals A modifier screen identifies regulators of cytoskeletal architecture as mediators of Shroom-dependent changes in tissue morphology

Biology Open ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. bio055640
Author(s):  
Jeffrey D. Hildebrand ◽  
Adam D. Leventry ◽  
Omoregie P. Aideyman ◽  
John C. Majewski ◽  
James A. Haddad ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Cell Shape ◽  
Myosin Ii ◽  
Control Cell ◽  
Rho Kinase ◽  
Model Systems ◽  
Tissue Architecture ◽  
Tissue Morphology ◽  
Cell Architecture ◽  
Induced Changes

ABSTRACTRegulation of cell architecture is critical in the formation of tissues during animal development. The mechanisms that control cell shape must be both dynamic and stable in order to establish and maintain the correct cellular organization. Previous work has identified Shroom family proteins as essential regulators of cell morphology during vertebrate development. Shroom proteins regulate cell architecture by directing the subcellular distribution and activation of Rho-kinase, which results in the localized activation of non-muscle myosin II. Because the Shroom-Rock-myosin II module is conserved in most animal model systems, we have utilized Drosophila melanogaster to further investigate the pathways and components that are required for Shroom to define cell shape and tissue architecture. Using a phenotype-based heterozygous F1 genetic screen for modifiers of Shroom activity, we identified several cytoskeletal and signaling protein that may cooperate with Shroom. We show that two of these proteins, Enabled and Short stop, are required for ShroomA-induced changes in tissue morphology and are apically enriched in response to Shroom expression. While the recruitment of Ena is necessary, it is not sufficient to redefine cell morphology. Additionally, this requirement for Ena appears to be context dependent, as a variant of Shroom that is apically localized, binds to Rock, but lacks the Ena binding site, is still capable of inducing changes in tissue architecture. These data point to important cellular pathways that may regulate contractility or facilitate Shroom-mediated changes in cell and tissue morphology.

scholarly journals A Novel Regulatory Mechanism of Myosin Light Chain Phosphorylation via Binding of 14-3-3 to Myosin Phosphatase

2008 ◽  
Vol 19 (3) ◽  
pp. 1062-1071 ◽  
Author(s):  
Yasuhiko Koga ◽  
Mitsuo Ikebe
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Regulatory Mechanism ◽  
Kinase Inhibitor ◽  
Myosin Ii ◽  
Critical Role ◽  
Rho Kinase ◽  
Myosin Phosphatase ◽  
Dependent Cell ◽  
Direct Binding

Myosin II phosphorylation–dependent cell motile events are regulated by myosin light-chain (MLC) kinase and MLC phosphatase (MLCP). Recent studies have revealed myosin phosphatase targeting subunit (MYPT1), a myosin-binding subunit of MLCP, plays a critical role in MLCP regulation. Here we report the new regulatory mechanism of MLCP via the interaction between 14-3-3 and MYPT1. The binding of 14-3-3β to MYPT1 diminished the direct binding between MYPT1 and myosin II, and 14-3-3β overexpression abolished MYPT1 localization at stress fiber. Furthermore, 14-3-3β inhibited MLCP holoenzyme activity via the interaction with MYPT1. Consistently, 14-3-3β overexpression increased myosin II phosphorylation in cells. We found that MYPT1 phosphorylation at Ser472 was critical for the binding to 14-3-3. Epidermal growth factor (EGF) stimulation increased both Ser472 phosphorylation and the binding of MYPT1-14-3-3. Rho-kinase inhibitor inhibited the EGF-induced Ser472 phosphorylation and the binding of MYPT1-14-3-3. Rho-kinase specific siRNA also decreased EGF-induced Ser472 phosphorylation correlated with the decrease in MLC phosphorylation. The present study revealed a new RhoA/Rho-kinase–dependent regulatory mechanism of myosin II phosphorylation by 14-3-3 that dissociates MLCP from myosin II and attenuates MLCP activity.

scholarly journals Enhancement of mDia2 activity by Rho-kinase-dependent phosphorylation of the diaphanous autoregulatory domain

2011 ◽  
Vol 439 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Dean P. Staus ◽  
Joan M. Taylor ◽  
Christopher P. Mack
Keyword(s):  
Smooth Muscle ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Rho Kinase ◽  
Specific Gene ◽  
Related Transcription Factor ◽  
Inhibitory Domain ◽  
Serum Response ◽  
Acidic Region ◽  
Basic Region

It is clear that RhoA activates the DRF (diaphanous-related formin) mDia2 by disrupting the molecular interaction between the DAD (diaphanous autoregulatory domain) and the DID (diaphanous inhibitory domain). Previous studies indicate that a basic motif within the DAD contributes to mDia2 auto-inhibition, and results shown in the present study suggest these residues bind a conserved acidic region within the DID. Furthermore, we demonstrate that mDia2 is phosphorylated by ROCK (Rho-kinase) at two conserved residues (Thr1061 and Ser1070) just C-terminal to the DAD basic region. Phosphomimetic mutations to these residues in the context of the full-length molecule enhanced mDia2 activity as measured by increased actin polymerization, SRF (serum response factor)-dependent smooth muscle-specific gene transcription, and nuclear localization of myocardin-related transcription factor B. Biochemical and functional data indicate that the T1061E/S1070E mutation significantly inhibited the ability of DAD to interact with DID and enhanced mDia2 activation by RhoA. Taken together, the results of the present study indicate that ROCK-dependent phosphorylation of the mDia2 DAD is an important determinant of mDia2 activity and that this signalling mechanism affects actin polymerization and smooth muscle cell-specific gene expression.

scholarly journals Adhesion-dependent and Contractile Ring-independent Equatorial Furrowing during Cytokinesis in Mammalian Cells

2005 ◽  
Vol 16 (8) ◽  
pp. 3865-3872 ◽  
Author(s):  
Masamitsu Kanada ◽  
Akira Nagasaki ◽  
Taro Q.P. Uyeda
Keyword(s):  
Mammalian Cells ◽  
Rat Kidney ◽  
Myosin Ii ◽  
Rho Kinase ◽  
Cellular Slime Mold ◽  
Animal Cells ◽  
Contractile Ring ◽  
Normal Rat ◽  
Cellular Slime ◽  
Coated Surfaces

Myosin II-dependent contraction of the contractile ring drives equatorial furrowing during cytokinesis in animal cells. Nonetheless, myosin II-null cells of the cellular slime mold Dictyostelium divide efficiently when adhering to substrates by making use of polar traction forces. Here, we show that in the presence of 30 μM blebbistatin, a potent myosin II inhibitor, normal rat kidney (NRK) cells adhering to fibronectin-coated surfaces formed equatorial furrows and divided in a manner strikingly similar to myosin II-null Dictyostelium cells. Such blebbistatin-resistant cytokinesis was absent in partially detached NRK cells and was disrupted in adherent cells if the advance of their polar lamellipodia was disturbed by neighboring cells. Y-27632 (40 μM), which inhibits Rho-kinase, was similar to 30 μM blebbistatin in that it inhibited cytokinesis of partially detached NRK cells but only prolonged furrow ingression in attached cells. In the presence of 100 μM blebbistatin, most NRK cells that initiated anaphase formed tight furrows, although scission never occurred. Adherent HT1080 fibrosarcoma cells also formed equatorial furrows efficiently in the presence of 100 μM blebbistatin. These results provide direct evidence for adhesion-dependent, contractile ring-independent equatorial furrowing in mammalian cells and demonstrate the importance of substrate adhesion for cytokinesis.

scholarly journals The Rho/Rho-kinase Systems Are Involved in Rapid Pacing-induced Changes of Atrial Refractory Period in a Canine Model

2006 ◽  
Vol 22 (3) ◽  
pp. 167-173
Author(s):  
Hiroshi Furusho ◽  
Satoru Sakagami ◽  
Masayuki Takamura ◽  
Katsunori Kitano ◽  
Tsuyoshi Abe ◽  
...  
Keyword(s):  
Refractory Period ◽  
Rho Kinase ◽  
Canine Model ◽  
Rapid Pacing ◽  
Induced Changes

scholarly journals Contribution of Filopodia to Cell Migration: A Mechanical Link between Protrusion and Contraction

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Fei Xue ◽  
Deanna M. Janzen ◽  
David A. Knecht
Keyword(s):  
Cell Migration ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Temporal Distribution ◽  
Leading Edge ◽  
Distal Portion ◽  
Actin Binding ◽  
Actin Networks ◽  
Motile Cells ◽  
A Cell

Numerous F-actin containing structures are involved in regulating protrusion of membrane at the leading edge of motile cells. We have investigated the structure and dynamics of filopodia as they relate to events at the leading edge and the function of the trailing actin networks. We have found that although filopodia contain parallel bundles of actin, they contain a surprisingly nonuniform spatial and temporal distribution of actin binding proteins. Along the length of the actin filaments in a single filopodium, the most distal portion contains primarily T-plastin, while the proximal portion is primarily bound byα-actinin and coronin. Some filopodia are stationary, but lateral filopodia move with respect to the leading edge. They appear to form a mechanical link between the actin polymerization network at the front of the cell and the myosin motor activity in the cell body. The direction of lateral filopodial movement is associated with the direction of cell migration. When lateral filopodia initiate from and move toward only one side of a cell, the cell will turn opposite to the direction of filopodial flow. Therefore, this filopodia-myosin II system allows actin polymerization driven protrusion forces and myosin II mediated contractile force to be mechanically coordinated.

scholarly journals Effects of acute Rho kinase inhibition on chronic hypoxia-induced changes in proximal and distal pulmonary arterial structure and function

2011 ◽  
Vol 110 (1) ◽  
pp. 188-198 ◽  
Author(s):  
Rebecca R. Vanderpool ◽  
Ah Ram Kim ◽  
Robert Molthen ◽  
Naomi C. Chesler
Keyword(s):  
Pulmonary Artery ◽  
Pulmonary Arteries ◽  
Rho Kinase ◽  
Pressure Flow ◽  
Kinase Inhibition ◽  
Pulmonary Vasoconstriction ◽  
Pulsatile Pressure ◽  
Arterial Structure ◽  
Pulmonary Arterial ◽  
Induced Changes

Hypoxic pulmonary hypertension (HPH) is initially a disease of the small pulmonary arteries. Its severity is usually quantified by pulmonary vascular resistance (PVR). Acute Rho kinase inhibition has been found to reduce PVR toward control values in animal models, suggesting that persistent pulmonary vasoconstriction is the dominant mechanism for increased PVR. However, HPH may also cause proximal arterial changes, which are relevant to right ventricular (RV) afterload. RV afterload can be quantified by pulmonary vascular impedance, which is obtained via spectral analysis of pulsatile pressure-flow relationships. To determine the effects of HPH independent of persistent pulmonary vasoconstriction in proximal and distal arteries, we quantified pulsatile pressure-flow relationships before and after acute Rho kinase inhibition and measured pulmonary arterial structure with microcomputed tomography. In control lungs, Rho kinase inhibition decreased 0 Hz impedance (Z0), which is equivalent to PVR, from 2.1 ± 0.4 to 1.5 ± 0.2 mmHg·min·ml−1 ( P < 0.05) and tended to increase characteristic impedance (ZC) from 0.21 ± 0.01 to 0.22 ± 0.01 mmHg·min·ml−1. In HPH lungs, Rho kinase inhibition decreased Z0 ( P < 0.05) without affecting ZC. Microcomputed tomography measurements performed on lungs after acute Rho kinase inhibition demonstrated that HPH significantly decreased the unstressed diameter of the main pulmonary artery (760 ± 60 vs. 650 ± 80 μm; P < 0.05), decreased right pulmonary artery compliance, and reduced the frequency of arteries of diameter 50–100 μm (both P < 0.05). These results demonstrate that acute Rho kinase inhibition reverses many but not all HPH-induced changes in distal pulmonary arteries but does not affect HPH-induced changes in the conduit arteries that impact RV afterload.

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