scholarly journals Filamin A mediates isotropic distribution of applied force across the actin network

2019 ◽  
Vol 218 (8) ◽  
pp. 2481-2491 ◽  
Author(s):  
Abhishek Kumar ◽  
Maria S. Shutova ◽  
Keiichiro Tanaka ◽  
Daniel V. Iwamoto ◽  
David A. Calderwood ◽  
...  
Keyword(s):  
Mechanical Strain ◽  
Focal Adhesions ◽  
High Resolution Electron Microscopy ◽  
Filamin A ◽  
Actin Network ◽  
Force Transmission ◽  
Cortical Actin ◽  
Isotropic Distribution ◽  
Elastic Substrates ◽  
Applied Forces

Cell sensing of externally applied mechanical strain through integrin-mediated adhesions is critical in development and physiology of muscle, lung, tendon, and arteries, among others. We examined the effects of strain on force transmission through the essential cytoskeletal linker talin. Using a fluorescence-based talin tension sensor (TS), we found that uniaxial stretch of cells on elastic substrates increased tension on talin, which was unexpectedly independent of the orientation of the focal adhesions relative to the direction of strain. High-resolution electron microscopy of the actin cytoskeleton revealed that stress fibers (SFs) are integrated into an isotropic network of cortical actin filaments in which filamin A (FlnA) localizes preferentially to points of intersection between SFs and cortical actin. Knockdown (KD) of FlnA resulted in more isolated, less integrated SFs. After FlnA KD, tension on talin was polarized in the direction of stretch, while FlnA reexpression restored tensional symmetry. These data demonstrate that a FlnA-dependent cortical actin network distributes applied forces over the entire cytoskeleton–matrix interface.

External mechanical strain regulates membrane targeting of Rho GTPases by controlling microtubule assembly

2003 ◽  
Vol 284 (3) ◽  
pp. C627-C639 ◽  
Author(s):  
Andrew J. Putnam ◽  
James J. Cunningham ◽  
Brendan B. L. Pillemer ◽  
David J. Mooney
Keyword(s):  
Rho Gtpases ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Mechanical Strain ◽  
Focal Adhesions ◽  
Small Gtpases ◽  
Microtubule Assembly ◽  
A Cell ◽  
Applied Forces ◽  
Triton X

Transmission of externally applied mechanical forces to the interior of a cell requires coordination of biochemical signaling pathways with changes in cytoskeletal assembly and organization. In this study, we addressed one potential mechanism for this signal integration by applying uniform single external mechanical strains to aortic smooth muscle cells (SMCs) via their adhesion substrate. A tensile strain applied to the substrate for 15 min significantly increased microtubule (MT) assembly by 32 ± 7%, with no apparent effect on the cells' focal adhesions as revealed by immunofluorescence and quantitative analysis of Triton X-100-insoluble vinculin levels. A compressive strain decreased MT mass by 24 ± 9% but did not influence the level of vinculin in focal adhesions. To understand the decoupling of these two cell responses to mechanical strain, we examined a redistribution of the small GTPases RhoA and Rac. Tensile strain was found to decrease the amount of membrane-associated RhoA and Rac by 70 ± 9% and 45 ± 11%, respectively, compared with static controls. In contrast, compressive strain increased membrane-associated RhoA and Rac levels by 74 ± 17% and 36 ± 13%, respectively. Disruption of the MT network by prolonged treatments with low doses of either nocodazole or paclitaxel before the application of strain abolished the redistribution of RhoA and Rac in response to the applied forces. Combined, these results indicate that the effects of externally applied mechanical strain on the distribution and activation of the Rho family GTPases require changes in the state of MT polymerization.

scholarly journals The PtdIns3P-binding protein Phafin2 escorts macropinosomes through the cortical actin cytoskeleton

2017 ◽  
Author(s):  
Kay Oliver Schink ◽  
Kia Wee Tan ◽  
Hélène Spangenberg ◽  
Domenica Martorana ◽  
Marte Sneeggen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Binding Protein ◽  
Extracellular Fluid ◽  
Cancer Development ◽  
Cross Linking ◽  
Filamin A ◽  
Actin Network ◽  
Cortical Actin ◽  
Cell Centre

AbstractUptake of large volumes of extracellular fluid by actin-dependent macropinocytosis plays important roles in infection, immunity and cancer development. A key question is how large macropinosomes are able to squeeze through the dense actin network underlying the plasma membrane in order to move towards the cell centre for maturation. Here we show that, immediately after macropinosomes have been sealed off from the plasma membrane, the PH-and FYVE domain-containing protein Phafin2 is recruited by a mechanism that involves binding to phosphatidylinositol 3-phosphate (PtdIns3P) generated in a non-canonical manner. Phafin2 in turn regulates the actin cross-linking protein Filamin A to promote entry of macropinosomes through the subcortical actin matrix and subsequent maturation. Depletion of Phafin2 inhibits macropinocytic internalization and maturation. We conclude that PtdIns3P and its effector Phafin2 are key components of a system that allows nascent macropinosomes to navigate through the dense subcortical actin network.

scholarly journals Direct observation of a coil-to-helix contraction triggered by vinculin binding to talin

2020 ◽  
Vol 6 (21) ◽  
pp. eaaz4707 ◽  
Author(s):  
Rafael Tapia-Rojo ◽  
Alvaro Alonso-Caballero ◽  
Julio M. Fernandez
Keyword(s):  
Focal Adhesions ◽  
Interaction Force ◽  
Magnetic Tweezers ◽  
Feedback Mechanism ◽  
Force Transmission ◽  
Mechanical Coupling ◽  
Negative Feedback Mechanism ◽  
The Reformation ◽  
Energy Penalty ◽  
First Time

Vinculin binds unfolded talin domains in focal adhesions, which recruits actin filaments to reinforce the mechanical coupling of this organelle. However, it remains unknown how this interaction is regulated and its impact on the force transmission properties of this mechanotransduction pathway. Here, we use magnetic tweezers to measure the interaction between vinculin head and the talin R3 domain under physiological forces. For the first time, we resolve individual binding events as a short contraction of the unfolded talin polypeptide caused by the reformation of the vinculin-binding site helices, which dictates a biphasic mechanism that regulates this interaction. Force favors vinculin binding by unfolding talin and exposing the vinculin-binding sites; however, the coil-to-helix contraction introduces an energy penalty that increases with force, defining an optimal binding regime. This mechanism implies that the talin-vinculin-actin association could operate as a negative feedback mechanism to stabilize force on focal adhesions.

In silico CDM model sheds light on force transmission in cell from focal adhesions to nucleus

2016 ◽  
Vol 49 (13) ◽  
pp. 2625-2634 ◽  
Author(s):  
Jean-Louis Milan ◽  
Ian Manifacier ◽  
Kevin M. Beussman ◽  
Sangyoon J. Han ◽  
Nathan J. Sniadecki ◽  
...  
Keyword(s):  
In Silico ◽  
Focal Adhesions ◽  
Force Transmission

scholarly journals Kinematic Synthesis of Tendon-Driven Manipulators with Isotropic Transmission Characteristics

1993 ◽  
Vol 115 (4) ◽  
pp. 884-891 ◽  
Author(s):  
Yeong-Jeong Ou ◽  
Lung-Wen Tsai
Keyword(s):  
Jacobian Matrix ◽  
Null Vector ◽  
Force Distribution ◽  
Force Transmission ◽  
Transmission Characteristics ◽  
Kinematic Synthesis ◽  
End Effector ◽  
Structure Matrix ◽  
Applied Forces ◽  
Matrix Design

This paper presents a methodology for kinematic synthesis of tendon-driven manipulators with isotropic transmission characteristics. The force transmission characteristics, from the end-effector space to the actuator space, has been investigated. It is shown that tendon forces required to act against externally applied forces are functions of the structure matrix, its null vector, and the manipulator Jacobian matrix. Design equations for synthesizing a manipulator to possess isotropic transmission characteristics are derived. It is shown that manipulators which possess isotropic transmission characteristics have much better force distribution among their tendons.

scholarly journals Coupled myosin VI motors facilitate unidirectional movement on an F-actin network

2009 ◽  
Vol 187 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Sivaraj Sivaramakrishnan ◽  
James A. Spudich
Keyword(s):  
Single Molecule ◽  
Membrane Trafficking ◽  
Cell Periphery ◽  
Myosin Vi ◽  
Actin Network ◽  
Cortical Actin ◽  
Actin Cortex ◽  
Unidirectional Movement ◽  
Transport Vesicle ◽  
Pointed End

Unconventional myosins interact with the dense cortical actin network during processes such as membrane trafficking, cell migration, and mechanotransduction. Our understanding of unconventional myosin function is derived largely from assays that examine the interaction of a single myosin with a single actin filament. In this study, we have developed a model system to study the interaction between multiple tethered unconventional myosins and a model F-actin cortex, namely the lamellipodium of a migrating fish epidermal keratocyte. Using myosin VI, which moves toward the pointed end of actin filaments, we directly determine the polarity of the extracted keratocyte lamellipodium from the cell periphery to the cell nucleus. We use a combination of experimentation and simulation to demonstrate that multiple myosin VI molecules can coordinate to efficiently transport vesicle-size cargo over 10 µm of the dense interlaced actin network. Furthermore, several molecules of monomeric myosin VI, which are nonprocessive in single molecule assays, can coordinate to transport cargo with similar speeds as dimers.

scholarly journals In vivo dynamics of the cortical actin network revealed by fast-scanning atomic force microscopy

Microscopy ◽  
2017 ◽  
Vol 66 (4) ◽  
pp. 272-282 ◽  
Author(s):  
Yanshu Zhang ◽  
Aiko Yoshida ◽  
Nobuaki Sakai ◽  
Yoshitsugu Uekusa ◽  
Masahiro Kumeta ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Actin Network ◽  
Cortical Actin ◽  
Force Microscopy ◽  
Atomic Force

scholarly journals Piezo2 channel regulates RhoA and actin cytoskeleton to promote cell mechanobiological responses

2018 ◽  
Vol 115 (8) ◽  
pp. 1925-1930 ◽  
Author(s):  
Carlos Pardo-Pastor ◽  
Fanny Rubio-Moscardo ◽  
Marina Vogel-González ◽  
Selma A. Serra ◽  
Alexandros Afthinos ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Nuclear Translocation ◽  
Focal Adhesions ◽  
Leading Edge ◽  
Force Transmission ◽  
Cellular Processes ◽  
Fyn Kinase ◽  
Downstream Effector ◽  
Metastatic Cells

Actin polymerization and assembly into stress fibers (SFs) is central to many cellular processes. However, how SFs form in response to the mechanical interaction of cells with their environment is not fully understood. Here we have identified Piezo2 mechanosensitive cationic channel as a transducer of environmental physical cues into mechanobiological responses. Piezo2 is needed by brain metastatic cells from breast cancer (MDA-MB-231-BrM2) to probe their physical environment as they anchor and pull on their surroundings or when confronted with confined migration through narrow pores. Piezo2-mediated Ca2+ influx activates RhoA to control the formation and orientation of SFs and focal adhesions (FAs). A possible mechanism for the Piezo2-mediated activation of RhoA involves the recruitment of the Fyn kinase to the cell leading edge as well as calpain activation. Knockdown of Piezo2 in BrM2 cells alters SFs, FAs, and nuclear translocation of YAP; a phenotype rescued by overexpression of dominant-positive RhoA or its downstream effector, mDia1. Consequently, hallmarks of cancer invasion and metastasis related to RhoA, actin cytoskeleton, and/or force transmission, such as migration, extracellular matrix degradation, and Serpin B2 secretion, were reduced in cells lacking Piezo2.

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