scholarly journals Spatial integration of mechanical forces by α-actinin establishes actin network symmetry

2019 ◽  
Vol 132 (22) ◽  
pp. jcs236604 ◽  
Author(s):  
Fabrice Senger ◽  
Amandine Pitaval ◽  
Hajer Ennomani ◽  
Laetitia Kurzawa ◽  
Laurent Blanchoin ◽  
...  
Keyword(s):  
Mechanical Forces ◽  
Spatial Integration ◽  
Actin Network

scholarly journals Spatial integration of mechanical forces by alpha-actinin establishes actin network symmetry

2019 ◽  
Author(s):  
Fabrice Senger ◽  
Amandine Pitaval ◽  
Hajer Ennomani ◽  
Laetitia Kurzawa ◽  
Laurent Blanchoin ◽  
...  
Keyword(s):  
Network Architecture ◽  
Spatial Organization ◽  
Global Network ◽  
Mechanical Forces ◽  
Spatial Integration ◽  
Actin Network ◽  
Entire Cell ◽  
Extracellular Microenvironment ◽  
Extracellular Environment

Cell and tissue morphogenesis depend on the production and spatial organization of tensional forces in the actin cytoskeleton. Actin network architecture is complex because it is made of distinct modules in which filaments adopt a variety of organizations. The assembly and dynamics of these modules is well described but the self-organisation rules directing the global network architecture are much less understood. Here we investigated the mechanism regulating the interplay between network architecture and the geometry of cell’s extracellular environment. We found that α-actinin, a filament crosslinker, is essential for network symmetry to be consistent with extracellular microenvironment symmetry. It appeared to be required for the interconnection of transverse arcs with radial fibres to ensure an appropriate balance between forces at cell adhesions and across the entire actin network. Furthermore, the connectivity of the actin network appeared necessary for the cell ability to integrate and adapt to complex patterns of extracellular cues as they migrate. Altogether, our study has unveiled a role of actin-filament crosslinking in the physical integration of mechanical forces throughout the entire cell, and the role of this integration in the establishment and adaptation of intracellular symmetry axes in accordance with the geometry of extracellular cues.

Force-dependent vinculin binding to talin in live cells: a crucial step in anchoring the actin cytoskeleton to focal adhesions

2014 ◽  
Vol 306 (6) ◽  
pp. C607-C620 ◽  
Author(s):  
Hiroaki Hirata ◽  
Hitoshi Tatsumi ◽  
Chwee Teck Lim ◽  
Masahiro Sokabe
Keyword(s):  
Actin Cytoskeleton ◽  
Focal Adhesions ◽  
Living Cells ◽  
Live Cells ◽  
Mechanical Forces ◽  
Actin Network ◽  
Crucial Step

Mechanical forces play a pivotal role in the regulation of focal adhesions (FAs) where the actin cytoskeleton is anchored to the extracellular matrix through integrin and a variety of linker proteins including talin and vinculin. The localization of vinculin at FAs depends on mechanical forces. While in vitro studies have demonstrated the force-induced increase in vinculin binding to talin, it remains unclear whether such a mechanism exists at FAs in vivo. In this study, using fibroblasts cultured on elastic silicone substrata, we have examined the role of forces in modulating talin-vinculin binding at FAs. Stretching the substrata caused vinculin accumulation at talin-containing FAs, and this accumulation was abrogated by expressing the talin-binding domain of vinculin (domain D1, which inhibits endogenous vinculin from binding to talin). These results indicate that mechanical forces loaded to FAs facilitate vinculin binding to talin at FAs. In cell-protruding regions, the actin network moved backward over talin-containing FAs in domain D1-expressing cells while it was anchored to FAs in control cells, suggesting that the force-dependent vinculin binding to talin is crucial for anchoring the actin cytoskeleton to FAs in living cells.

scholarly journals Cytokinesis in vertebrate cells initiates by contraction of an equatorial actomyosin network composed of randomly oriented filaments

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Felix Spira ◽  
Sara Cuylen-Haering ◽  
Shalin Mehta ◽  
Matthias Samwer ◽  
Anne Reversat ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Local Network ◽  
Polarization Microscopy ◽  
Cleavage Furrow ◽  
Mechanical Forces ◽  
Biological Processes ◽  
Actin Network ◽  
Animal Cells ◽  
Mechanical Tension ◽  
Cortical Tension

The actomyosin ring generates force to ingress the cytokinetic cleavage furrow in animal cells, yet its filament organization and the mechanism of contractility is not well understood. We quantified actin filament order in human cells using fluorescence polarization microscopy and found that cleavage furrow ingression initiates by contraction of an equatorial actin network with randomly oriented filaments. The network subsequently gradually reoriented actin filaments along the cell equator. This strictly depended on myosin II activity, suggesting local network reorganization by mechanical forces. Cortical laser microsurgery revealed that during cytokinesis progression, mechanical tension increased substantially along the direction of the cell equator, while the network contracted laterally along the pole-to-pole axis without a detectable increase in tension. Our data suggest that an asymmetric increase in cortical tension promotes filament reorientation along the cytokinetic cleavage furrow, which might have implications for diverse other biological processes involving actomyosin rings.

The Palestinian Refugee Camps In Jordan: Between National Identity and Socio-economic Integration

2004 ◽  
Vol 2 (2) ◽  
pp. 198-221 ◽  
Author(s):  
Ala Al-Hamarneh
Keyword(s):  
United Nations ◽  
Collective Memory ◽  
Economic Integration ◽  
Refugee Camps ◽  
Spatial Integration ◽  
Political Activities ◽  
Cultural Traditions ◽  
The Past ◽  
Distinct Character ◽  
Palestinian Refugee

At least 50 per cent of the population of Jordan is of Palestinian origin. Some 20 per cent of the registered refugees live in ten internationally organized camps, and another 20 per cent in four locally organized camps and numerous informal camps. The camps organized by the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) play a major role in keeping Palestinian identity alive. That identity reflects the refugees' rich cultural traditions, political activities, as well as their collective memory, and the distinct character of each camp. Over the past two decades integration of the refugees within Jordanian society has increased. This paper analyses the transformation of the identity of the camp dwellers, as well as their spatial integration in Jordan, and other historical and contemporary factors contributing to this transformation.

Polypeptides Folding: Rules for the Calculation of the Backbone Dihedral Angles φ starting from the Amino Acid Sequence

2020 ◽  
Author(s):  
Michele Larocca
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Theoretical Approach ◽  
Polypeptide Chain ◽  
Hydrophobic Effect ◽  
Side Chain ◽  
Dihedral Angles ◽  
Mechanical Forces ◽  
Specific Chemical

<p>Protein folding is strictly related to the determination of the backbone dihedral angles and depends on the information contained in the amino acid sequence as well as on the hydrophobic effect. To date, the type of information embedded in the amino acid sequence has not yet been revealed. The present study deals with these problematics and aims to furnish a possible explanation of the information contained in the amino acid sequence, showing and reporting rules to calculate the backbone dihedral angles φ. The study is based on the development of mechanical forces once specific chemical interactions are established among the side chain of the residues in a polypeptide chain. It aims to furnish a theoretical approach to predict backbone dihedral angles which, in the future, may be applied to computational developments focused on the prediction of polypeptide structures.</p>

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