scholarly journals The role of actin and myosin II in the cell cortex of adhered and suspended cells

2021 ◽  
Author(s):  
Daniel Flormann ◽  
Kevin Kaub ◽  
Doriane Vesperini ◽  
Moritz Schu ◽  
Christoph Anton ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Cell Cortex ◽  
Cellular Processes ◽  
Actin Cortex ◽  
Nonmuscle Myosin Ii ◽  
Prediction And Control ◽  
The Many ◽  
A Minor ◽  
Microscopy Techniques ◽  
And Control

Adhesion induces dramatic morphological and mechanical changes to cells, which are reflected by changes to the actin cortex. Among the many different proteins involved in this sub-membranous layer, motor proteins (e.g., nonmuscle myosin II [NMII]) and actin nucleators (e.g., Arp2/3, formins) are known to have significant influences on its dynamics and structure. The different roles of NMII, Arp2/3, and formins in the dynamics, structure, and mechanics of the actin cortex depend on the adhesion state of the cell. In this study, we unravel the interplay between the dynamics, structure, and mechanics of the actin cortex in adhered cells and in cells in suspension. We show that treatments with extrinsic cellular perturbants lead to alterations of all three properties that are correlated. However, intrinsic actin cortex variations between different cell adhesion states lead to unexpected correlations. Surprisingly, we find that NMII minifilaments have a minor influence on the actin cortex. Using new microscopy techniques, we show that NMII minifilaments are not localized within the actin cortex, as previously thought, but concentrated in a layer beneath it. Our treatments affecting Arp2/3 and formin reveal correlations between the actin cortex characteristics. Our data build towards a comprehensive understanding of the actin cortex. This understanding allows the prediction and control of cortical changes, which is essential for the study of general cellular processes, such as cell migration, metastasis, and differentiation.

scholarly journals Generation of stress fibers through myosin-driven re-organization of the actin cortex

2020 ◽  
Author(s):  
JI Lehtimäki ◽  
EK Rajakylä ◽  
S Tojkander ◽  
P Lappalainen
Keyword(s):  
De Novo ◽  
Myosin Ii ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Cellular Processes ◽  
Actin Cortex ◽  
Muscle Myosin ◽  
Subsequent Stabilization

SummaryContractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex, and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

scholarly journals Generation of stress fibers through myosin-driven reorganization of the actin cortex

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jaakko I Lehtimäki ◽  
Eeva Kaisa Rajakylä ◽  
Sari Tojkander ◽  
Pekka Lappalainen
Keyword(s):  
De Novo ◽  
Myosin Ii ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Cellular Processes ◽  
Actin Cortex ◽  
Muscle Myosin ◽  
Subsequent Stabilization

Contractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

scholarly journals Myosin IIA drives membrane bleb retraction

2019 ◽  
Vol 30 (9) ◽  
pp. 1051-1059 ◽  
Author(s):  
Nilay Taneja ◽  
Dylan T. Burnette
Keyword(s):  
Mammalian Cells ◽  
Myosin Ii ◽  
Cross Linking ◽  
Nonmuscle Myosin ◽  
Final Phase ◽  
Biophysical Properties ◽  
Actin Cortex ◽  
Nonmuscle Myosin Ii ◽  
Membrane Blebs ◽  
Ability To Drive

Membrane blebs are specialized cellular protrusions that play diverse roles in processes such as cell division and cell migration. Blebbing can be divided into three distinct phases: bleb nucleation, bleb growth, and bleb retraction. Following nucleation and bleb growth, the actin cortex, comprising actin, cross-linking proteins, and nonmuscle myosin II (MII), begins to reassemble on the membrane. MII then drives the final phase, bleb retraction, which results in reintegration of the bleb into the cellular cortex. There are three MII paralogues with distinct biophysical properties expressed in mammalian cells: MIIA, MIIB, and MIIC. Here we show that MIIA specifically drives bleb retraction during cytokinesis. The motor domain and regulation of the nonhelical tailpiece of MIIA both contribute to its ability to drive bleb retraction. These experiments have also revealed a relationship between faster turnover of MIIA at the cortex and its ability to drive bleb retraction.

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 Effects of energy metabolism on the mechanical properties of breast cancer cells

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Marina. L. Yubero ◽  
Priscila M. Kosaka ◽  
Álvaro San Paulo ◽  
Marcos Malumbres ◽  
Montserrat Calleja ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Cell Cortex ◽  
Mechanical Resistance ◽  
Fiber Architecture ◽  
Actin Cortex ◽  
Actin Fiber ◽  
Active Processes ◽  
Cancerous Cells

Abstract Tumorigenesis induces actin cortex remodeling, which makes cancerous cells softer. Cell deformability is largely determined by myosin-driven cortical tension and actin fiber architecture at the cell cortex. However, it is still unclear what the weight of each contribution is, and how these contributions change during cancer development. Moreover, little attention has been paid to the effect of energy metabolism on this phenomenon and its reprogramming in cancer. Here, we perform precise two-dimensional mechanical phenotyping based on power-law rheology to unveil the contributions of myosin II, actin fiber architecture and energy metabolism to the deformability of healthy (MCF-10A), noninvasive cancerous (MCF-7), and metastatic (MDA-MB-231) human breast epithelial cells. Contrary to the perception that the actin cortex is a passive structure that provides mechanical resistance to the cell, we find that this is only true when the actin cortex is activated by metabolic processes. The results show marked differences in the nature of the active processes that build up cell stiffness, namely that healthy cells use ATP-driven actin polymerization whereas metastatic cells use myosin II activity. Noninvasive cancerous cells exhibit an anomalous behavior, as their stiffness is not as affected by the lack of nutrients and ATP, suggesting that energy metabolism reprogramming is used to sustain active processes at the actin cortex.

scholarly journals Anillin promotes astral microtubule-directed cortical myosin polarization

2011 ◽  
Vol 22 (17) ◽  
pp. 3165-3175 ◽  
Author(s):  
Yu Chung Tse ◽  
Alisa Piekny ◽  
Michael Glotzer
Keyword(s):  
Myosin Ii ◽  
Cell Polarization ◽  
Cell Cortex ◽  
Polar Regions ◽  
Contractile Ring ◽  
Central Spindle ◽  
Astral Microtubule ◽  
Nonmuscle Myosin Ii ◽  
Evolutionarily Conserved ◽  
Cortical Asymmetry

Assembly of a cytokinetic contractile ring is a form of cell polarization in which the equatorial cell cortex becomes differentiated from the polar regions. Microtubules direct cytokinetic polarization via the central spindle and astral microtubules. The mechanism of central spindle–directed furrow formation is reasonably well understood, but the aster-directed pathway is not. In aster-directed furrowing, cytoskeletal factors accumulate to high levels at sites distal to the asters and at reduced levels at cortical sites near the asters. In this paper, we demonstrate that the cytoskeletal organizing protein anillin (ANI-1) promotes the formation of an aster-directed furrow in Caenorhabditis elegans embryos. Microtubule-directed nonmuscle myosin II polarization is aberrant in embryos depleted of ANI-1. In contrast, microtubule-directed polarized ANI-1 localization is largely unaffected by myosin II depletion. Consistent with a role in the induction of cortical asymmetry, ANI-1 also contributes to the polarization of arrested oocytes. Anillin has an evolutionarily conserved capacity to associate with microtubules, possibly providing an inhibitory mechanism to promote polarization of the cell cortex.

scholarly journals Design Specifications for Cellular Regulation

2016 ◽  
Author(s):  
David C. Krakauer ◽  
Lydia Müller ◽  
Sonja J. Prohaska ◽  
Peter F. Stadler
Keyword(s):  
Regulatory Networks ◽  
Metabolic Flux ◽  
Cellular Regulation ◽  
Critical Feature ◽  
Cellular Processes ◽  
Design Specifications ◽  
Regulatory Systems ◽  
Common Framework ◽  
The Many ◽  
And Control

AbstractA critical feature of all cellular processes is the ability to control the rate of gene or protein expression and metabolic flux in changing environments through regulatory feedback. We review the many ways that regulation is represented through causal, logical and dynamical components. Formalizing the nature of these components promotes effective comparison among distinct regulatory networks and provides a common framework for the potential design and control of regulatory systems in synthetic biology.

Computers for data, control and simulation

1988 ◽  
Vol 46 ◽  
pp. 920-921
Author(s):  
David C. Joy
Keyword(s):  
Personal Computers ◽  
Monitoring And Control ◽  
Data Logging ◽  
Data Logger ◽  
Operational Conditions ◽  
Data Control ◽  
The Many ◽  
And Control

Personal computers (PCs) are a powerful resource in the EM Laboratory, both as a means of automating the monitoring and control of microscopes, and as a tool for quantifying the interpretation of data. Not only is a PC more versatile than a piece of dedicated data logging equipment, but it is also substantially cheaper. In this tutorial the practical principles of using a PC for these types of activities will be discussed.The PC can form the basis of a system to measure, display, record and store the many parameters which characterize the operational conditions of the EM. In this mode it is operating as a data logger. The necessary first step is to find a suitable source from which to measure each of the items of interest. It is usually possible to do this without having to make permanent corrections or modifications to the EM.

Interference mitigation in point to point wireless sensor networks using LSP protocol and time division multiplexing approach

2020 ◽  
Vol 39 (4) ◽  
pp. 5449-5458
Author(s):  
A. Arokiaraj Jovith ◽  
S.V. Kasmir Raja ◽  
A. Razia Sulthana
Keyword(s):  
Energy Consumption ◽  
Large Scale ◽  
Control Parameter ◽  
Interference Mitigation ◽  
Wireless Sensor ◽  
Point To Point ◽  
A Minor ◽  
Two Stages ◽  
Time Division ◽  
And Control

Interference in Wireless Sensor Network (WSN) predominantly affects the performance of the WSN. Energy consumption in WSN is one of the greatest concerns in the current generation. This work presents an approach for interference measurement and interference mitigation in point to point network. The nodes are distributed in the network and interference is measured by grouping the nodes in the region of a specific diameter. Hence this approach is scalable and isextended to large scale WSN. Interference is measured in two stages. In the first stage, interference is overcome by allocating time slots to the node stations in Time Division Multiple Access (TDMA) fashion. The node area is split into larger regions and smaller regions. The time slots are allocated to smaller regions in TDMA fashion. A TDMA based time slot allocation algorithm is proposed in this paper to enable reuse of timeslots with minimal interference between smaller regions. In the second stage, the network density and control parameter is introduced to reduce interference in a minor level within smaller node regions. The algorithm issimulated and the system is tested with varying control parameter. The node-level interference and the energy dissipation at nodes are captured by varying the node density of the network. The results indicate that the proposed approach measures the interference and mitigates with minimal energy consumption at nodes and with less overhead transmission.

An insight into Case Management and Challenges in Veteran Suicide Prevention

2020 ◽  
pp. 14-25
Author(s):  
Tamara Green
Keyword(s):  
Case Management ◽  
Suicide Prevention ◽  
Suicide Risk ◽  
Digital Transformation ◽  
Prevention Science ◽  
Historical Records ◽  
Military Members ◽  
Prediction And Control ◽  
And Control ◽  
Insight Into

Much of the literature, policies, programs, and investment has been made on mental health, case management, and suicide prevention of veterans. The Australian “veteran community is facing a suicide epidemic for the reasons that are extremely complex and beyond the scope of those currently dealing with them.” (Menz, D: 2019). Only limited work has considered the digital transformation of loosely and manual-based historical records and no enablement of Artificial Intelligence (A.I) and machine learning to suicide risk prediction and control for serving military members and veterans to date. This paper presents issues and challenges in suicide prevention and management of veterans, from the standing of policymakers to stakeholders, campaigners of veteran suicide prevention, science and big data, and an opportunity for the digital transformation of case management.

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