scholarly journals Shape remodeling and blebbing of active cytoskeletal vesicles

2016 ◽  
Vol 2 (4) ◽  
pp. e1500465 ◽  
Author(s):  
Etienne Loiseau ◽  
Jochen A. M. Schneider ◽  
Felix C. Keber ◽  
Carina Pelzl ◽  
Gladys Massiera ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Contractile Activity ◽  
Lipid Vesicles ◽  
Building Blocks ◽  
Living Cells ◽  
Force Balance ◽  
Actin Network ◽  
Shape Transformation ◽  
Cytoskeletal Network ◽  
Morphological Transformations

Morphological transformations of living cells, such as shape adaptation to external stimuli, blebbing, invagination, or tethering, result from an intricate interplay between the plasma membrane and its underlying cytoskeleton, where molecular motors generate forces. Cellular complexity defies a clear identification of the competing processes that lead to such a rich phenomenology. In a synthetic biology approach, designing a cell-like model assembled from a minimal set of purified building blocks would allow the control of all relevant parameters. We reconstruct actomyosin vesicles in which the coupling of the cytoskeleton to the membrane, the topology of the cytoskeletal network, and the contractile activity can all be precisely controlled and tuned. We demonstrate that tension generation of an encapsulated active actomyosin network suffices for global shape transformation of cell-sized lipid vesicles, which are reminiscent of morphological adaptations in living cells. The observed polymorphism of our cell-like model, such as blebbing, tether extrusion, or faceted shapes, can be qualitatively explained by the protein concentration dependencies and a force balance, taking into account the membrane tension, the density of anchoring points between the membrane and the actin network, and the forces exerted by molecular motors in the actin network. The identification of the physical mechanisms for shape transformations of active cytoskeletal vesicles sets a conceptual and quantitative benchmark for the further exploration of the adaptation mechanisms of cells.

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 Mechanical Properties of Organelles Driven by Microtubule-Dependent Molecular Motors in Living Cells

PLoS ONE ◽  
2011 ◽  
Vol 6 (4) ◽  
pp. e18332 ◽  
Author(s):  
Luciana Bruno ◽  
Marcelo Salierno ◽  
Diana E. Wetzler ◽  
Marcelo A. Despósito ◽  
Valeria Levi
Keyword(s):  
Mechanical Properties ◽  
Molecular Motors ◽  
Living Cells

scholarly journals Dissection of molecular assembly dynamics by tracking orientation and position of single molecules in live cells

2016 ◽  
Vol 113 (42) ◽  
pp. E6352-E6361 ◽  
Author(s):  
Shalin B. Mehta ◽  
Molly McQuilken ◽  
Patrick J. La Riviere ◽  
Patricia Occhipinti ◽  
Amitabh Verma ◽  
...  
Keyword(s):  
Single Molecule ◽  
Leading Edge ◽  
Living Cells ◽  
Molecular Assembly ◽  
Higher Order ◽  
Live Cells ◽  
Actin Network ◽  
Position And Orientation ◽  
Orientation Of Molecules

Regulation of order, such as orientation and conformation, drives the function of most molecular assemblies in living cells but remains difficult to measure accurately through space and time. We built an instantaneous fluorescence polarization microscope, which simultaneously images position and orientation of fluorophores in living cells with single-molecule sensitivity and a time resolution of 100 ms. We developed image acquisition and analysis methods to track single particles that interact with higher-order assemblies of molecules. We tracked the fluctuations in position and orientation of molecules from the level of an ensemble of fluorophores down to single fluorophores. We tested our system in vitro using fluorescently labeled DNA and F-actin, in which the ensemble orientation of polarized fluorescence is known. We then tracked the orientation of sparsely labeled F-actin network at the leading edge of migrating human keratinocytes, revealing the anisotropic distribution of actin filaments relative to the local retrograde flow of the F-actin network. Additionally, we analyzed the position and orientation of septin-GFP molecules incorporated in septin bundles in growing hyphae of a filamentous fungus. Our data indicate that septin-GFP molecules undergo positional fluctuations within ∼350 nm of the binding site and angular fluctuations within ∼30° of the central orientation of the bundle. By reporting position and orientation of molecules while they form dynamic higher-order structures, our approach can provide insights into how micrometer-scale ordered assemblies emerge from nanoscale molecules in living cells.

scholarly journals An Appraisal of the Field of Metallomics and the Roles of Metal Ions in Biochemistry and Cell Signaling

2021 ◽  
Vol 11 (22) ◽  
pp. 10846
Author(s):  
Wolfgang Maret
Keyword(s):  
Applied Sciences ◽  
Metal Ions ◽  
Evolutionary History ◽  
Chemical Elements ◽  
Building Blocks ◽  
Living Cells ◽  
Manufacturing Processes ◽  
Essential Metals ◽  
Essential Metal ◽  
Functional Consequences

Humans require about 20 chemical elements. Half of them are essential metal ions. Many additional, non-essential metal ions are present in our bodies through environmental exposures, including in our diet, with functional consequences. Their accumulation is accelerated due to the increasing pollution of soil, air, water and manufacturing processes that employ chemical elements to which we have not been exposed in our evolutionary history. Yet other metal ions are essential for other forms of life, which calls on life scientists to consider the interactions of life processes with most of the chemical elements in the periodic table. Only in this century have attempts been made to integrate specialty disciplines into a science of bioelements called metallomics. Metallomics forms a fifth group when added to the traditional four building blocks of living cells and their areas of investigations, i.e., sugars (glycomics), fats (lipidomics), proteins (proteomics) and nucleic acids (genomics). Neither an understanding of all the essential metals and their interactions nor the functional impacts of the non-essential metals for life, except established toxic elements such as lead, are widely perceived as important in the basic science communities and in the applied sciences such as medicine and engineering. It is a remarkable oversight that this article attempts to address with representative examples.

scholarly journals Structures of FHOD1-Nesprin1/2 complexes reveal alternate binding modes for the FH3 domain of formins

2020 ◽  
Author(s):  
Sing Mei Lim ◽  
Victor E. Cruz ◽  
Susumu Antoku ◽  
Gregg G. Gundersen ◽  
Thomas U. Schwartz
Keyword(s):  
Complex Structure ◽  
Binding Mode ◽  
Eukaryotic Cells ◽  
Binding Modes ◽  
Actin Network ◽  
Nuclear Movement ◽  
Spectrin Repeat ◽  
Major Activity ◽  
Binding Partners ◽  
Cytoskeletal Network

ABSTRACTThe nuclear position in eukaryotic cells is controlled by a nucleo-cytoskeletal network, with important roles in cell differentiation, division and movement. Forces are transmitted through conserved linker of nucleoskeleton and cytoskeleton (LINC) complexes that traverse the nuclear envelope and engage on either side of the membrane with diverse binding partners. Nesprin-2 giant (Nes2G), a LINC element in the outer nuclear membrane, connects to the actin network directly as well as through FHOD1, a formin whose major activity is bundling actin. Much of the molecular details of this process remain poorly understood. Here, we report the crystal structure of Nes2G bound to FHOD1. We show that the G-binding domain of FHOD1 is rather a spectrin repeat binding enhancer for the neighboring FH3 domain, possibly establishing a common binding mode among this subclass of formins. The FHOD1-Nes2G complex structure suggests that spectrin repeat binding by FHOD1 is likely not regulated by the DAD helix of FHOD1. Finally, we establish that Nes1G also has one FHOD1 binding spectrin repeat, indicating that these abundant, giant Nesprins have overlapping functions in actin-bundle recruitment for nuclear movement.

scholarly journals Development of Artificial Cell Models Using Microfluidic Technology and Synthetic Biology

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 559 ◽  
Author(s):  
Koki Kamiya
Keyword(s):  
Synthetic Biology ◽  
Cell Membrane ◽  
Lipid Bilayer ◽  
Lipid Membranes ◽  
Lipid Vesicles ◽  
Optical Microscope ◽  
Living Cells ◽  
Biochemical Properties ◽  
Cell Models ◽  
Artificial Cell

Giant lipid vesicles or liposomes are primarily composed of phospholipids and form a lipid bilayer structurally similar to that of the cell membrane. These vesicles, like living cells, are 5–100 μm in diameter and can be easily observed using an optical microscope. As their biophysical and biochemical properties are similar to those of the cell membrane, they serve as model cell membranes for the investigation of the biophysical or biochemical properties of the lipid bilayer, as well as its dynamics and structure. Investigation of membrane protein functions and enzyme reactions has revealed the presence of soluble or membrane proteins integrated in the giant lipid vesicles. Recent developments in microfluidic technologies and synthetic biology have enabled the development of well-defined artificial cell models with complex reactions based on the giant lipid vesicles. In this review, using microfluidics, the formations of giant lipid vesicles with asymmetric lipid membranes or complex structures have been described. Subsequently, the roles of these biomaterials in the creation of artificial cell models including nanopores, ion channels, and other membrane and soluble proteins have been discussed. Finally, the complex biological functions of giant lipid vesicles reconstituted with various types of biomolecules has been communicated. These complex artificial cell models contribute to the production of minimal cells or protocells for generating valuable or rare biomolecules and communicating between living cells and artificial cell models.

scholarly journals Nanoparticle-Lipid Interaction: Job Scattering Plots to Differentiate Vesicle Aggregation from Supported Lipid Bilayer Formation

2018 ◽  
Vol 2 (4) ◽  
pp. 50 ◽  
Author(s):  
Fanny Mousseau ◽  
Evdokia Oikonomou ◽  
Victor Baldim ◽  
Stéphane Mornet ◽  
Jean-François Berret
Keyword(s):  
Lipid Bilayers ◽  
Lipid Vesicles ◽  
Living Cells ◽  
Supported Lipid Bilayers ◽  
Supported Lipid Bilayer ◽  
Mixed Aggregates ◽  
Method Of Continuous Variation ◽  
The Impact ◽  
Analytical Expressions ◽  
Lipid Interaction

The impact of nanomaterials on lung fluids, or on the plasma membrane of living cells, has prompted researchers to examine the interactions between nanoparticles and lipid vesicles. Recent studies have shown that nanoparticle-lipid interaction leads to a broad range of structures including supported lipid bilayers (SLB), particles adsorbed at the surface or internalized inside vesicles, and mixed aggregates. Currently, there is a need to have simple protocols that can readily evaluate the structures made from particles and vesicles. Here we apply the method of continuous variation for measuring Job scattering plots and provide analytical expressions for the scattering intensity in various scenarios. The result that emerges from the comparison between experiments and modeling is that electrostatics play a key role in the association, but it is not sufficient to induce the formation of supported lipid bilayers.

Sign in / Sign up

Export Citation Format

Share Document