scholarly journals Control of Lipid Domain Organization by a Biomimetic Contractile Actomyosin Cortex

2016 ◽  
Author(s):  
Sven K. Vogel ◽  
Ferdinand Greiss ◽  
Alena Khmelinskaia ◽  
Petra Schwille
Keyword(s):  
Cell Membrane ◽  
Actin Filaments ◽  
Shape Change ◽  
Line Tension ◽  
Membrane Domains ◽  
Lipid Domain ◽  
Actin Cortex ◽  
Control Dynamic ◽  
Underlying Mechanisms ◽  
Lateral Organization

AbstractThe cell membrane is a heterogeneously organized composite with lipid-protein micro-domains. The contractile actin cortex may govern the lateral organization of these domains in the cell membrane, yet the underlying mechanisms are not known. We recently reconstituted minimal actin cortices (MACs) (Vogel et al, 2013b) and here advanced our assay to investigate effects of rearranging actin filaments on the lateral membrane organization by introducing various phase-separated lipid mono-and bilayers to the MACs. The addition of actin filaments reorganized membrane domains. We found that the process reached a steady state where line tension and lateral crowding balanced. Moreover, the phase boundary allowed myosin driven actin filament rearrangements to actively move individual lipid domains, often accompanied by their shape change, fusion or splitting. Our findings illustrate how actin cortex remodeling in cells may control dynamic rearrangements of lipids and other molecules inside domains without directly binding to actin filaments.

scholarly journals Control of lipid domain organization by a biomimetic contractile actomyosin cortex

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Sven Kenjiro Vogel ◽  
Ferdinand Greiss ◽  
Alena Khmelinskaia ◽  
Petra Schwille
Keyword(s):  
Cell Membrane ◽  
Actin Filaments ◽  
Shape Change ◽  
Line Tension ◽  
Membrane Domains ◽  
Lipid Domain ◽  
Actin Cortex ◽  
Control Dynamic ◽  
Underlying Mechanisms ◽  
Lateral Organization

The cell membrane is a heterogeneously organized composite with lipid-protein micro-domains. The contractile actin cortex may govern the lateral organization of these domains in the cell membrane, yet the underlying mechanisms are not known. We recently reconstituted minimal actin cortices (MACs) (Vogel et al., 2013b) and here advanced our assay to investigate effects of rearranging actin filaments on the lateral membrane organization by introducing various phase-separated lipid mono- and bilayers to the MACs. The addition of actin filaments reorganized membrane domains. We found that the process reached a steady state where line tension and lateral crowding balanced. Moreover, the phase boundary allowed myosin driven actin filament rearrangements to actively move individual lipid domains, often accompanied by their shape change, fusion or splitting. Our findings illustrate how actin cortex remodeling in cells may control dynamic rearrangements of lipids and other molecules inside domains without directly binding to actin filaments.

scholarly journals Force Mapping Study of Actinoporin Effect in Membranes Presenting Phase Domains

Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 669
Author(s):  
Katia Cosentino ◽  
Edward Hermann ◽  
Nicolai von Kügelgen ◽  
Joseph D. Unsay ◽  
Uris Ros ◽  
...  
Keyword(s):  
Line Tension ◽  
Lipid Phase ◽  
Membrane Domains ◽  
Lipid Domain ◽  
Force Microscopy ◽  
Membrane Affinity ◽  
Atomic Force ◽  
Force Mapping ◽  
Equinatoxin Ii ◽  
Mechanical Information

Equinatoxin II (EqtII) and Fragaceatoxin C (FraC) are pore-forming toxins (PFTs) from the actinoporin family that have enhanced membrane affinity in the presence of sphingomyelin (SM) and phase coexistence in the membrane. However, little is known about the effect of these proteins on the nanoscopic properties of membrane domains. Here, we used combined confocal microscopy and force mapping by atomic force microscopy to study the effect of EqtII and FraC on the organization of phase-separated phosphatidylcholine/SM/cholesterol membranes. To this aim, we developed a fast, high-throughput processing tool to correlate structural and nano-mechanical information from force mapping. We found that both proteins changed the lipid domain shape. Strikingly, they induced a reduction in the domain area and circularity, suggesting a decrease in the line tension due to a lipid phase height mismatch, which correlated with proteins binding to the domain interfaces. Moreover, force mapping suggested that the proteins affected the mechanical properties at the edge, but not in the bulk, of the domains. This effect could not be revealed by ensemble force spectroscopy measurements supporting the suitability of force mapping to study local membrane topographical and mechanical alterations by membranotropic proteins.

Line tension and the penetration of a cell membrane by an oil drop

1967 ◽  
Vol 17 (2) ◽  
pp. 246-251 ◽  
Author(s):  
N.L. Gershfeld ◽  
R.J. Good
Keyword(s):  
Cell Membrane ◽  
Line Tension ◽  
A Cell

scholarly journals αE-catenin actin-binding domain alters actin filament conformation and regulates binding of nucleation and disassembly factors

2013 ◽  
Vol 24 (23) ◽  
pp. 3710-3720 ◽  
Author(s):  
Scott D. Hansen ◽  
Adam V. Kwiatkowski ◽  
Chung-Yueh Ouyang ◽  
HongJun Liu ◽  
Sabine Pokutta ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Binding Domain ◽  
Actin Binding ◽  
Filamentous Actin ◽  
Filament Structure ◽  
Actin Binding Domain ◽  
Filament Bundles ◽  
Underlying Mechanisms ◽  
Cell Cell

The actin-binding protein αE-catenin may contribute to transitions between cell migration and cell–cell adhesion that depend on remodeling the actin cytoskeleton, but the underlying mechanisms are unknown. We show that the αE-catenin actin-binding domain (ABD) binds cooperatively to individual actin filaments and that binding is accompanied by a conformational change in the actin protomer that affects filament structure. αE-catenin ABD binding limits barbed-end growth, especially in actin filament bundles. αE-catenin ABD inhibits actin filament branching by the Arp2/3 complex and severing by cofilin, both of which contact regions of the actin protomer that are structurally altered by αE-catenin ABD binding. In epithelial cells, there is little correlation between the distribution of αE-catenin and the Arp2/3 complex at developing cell–cell contacts. Our results indicate that αE-catenin binding to filamentous actin favors assembly of unbranched filament bundles that are protected from severing over more dynamic, branched filament arrays.

Development of macrociliary cells in Beroe. I. Actin bundles and centriole migration

1988 ◽  
Vol 89 (1) ◽  
pp. 67-80
Author(s):  
S. Tamm ◽  
S.L. Tamm
Keyword(s):  
Cell Membrane ◽  
Basal Body ◽  
Actin Filaments ◽  
Close Association ◽  
Directed Assembly ◽  
Double Layers ◽  
Basal Bodies ◽  
Apical Surface ◽  
Actin Bundle ◽  
Microfilament Bundle

Differentiation of macrociliary cells on regenerating lips of the ctenophore Beroe was studied by transmission electron microscopy. In this study of early development, we found that basal bodies for macrocilia arise by an acentriolar pathway near the nucleus and Golgi apparatus, in close association with plaques of dense fibrogranular bodies. Procentrioles are often aligned side-by-side in double layers with the cartwheel ends facing outward toward the surrounding plaques of dense granules. Newly formed basal bodies then disband from groups and develop a long striated rootlet at one end. At the same time, an array of microfilaments arises in the basal cytoplasm. The microfilaments are arranged in parallel strands oriented toward the cell surface. The basal body-rootlet units are transported to the apical surface in close association with the assembling actin filament bundle. Microfilaments run parallel to and alongside the striated rootlets, to which they often appear attached. Basal body-rootlet units migrate at the heads of trails of microfilaments, as if they are pushed upwards by elongation of their attached actin filaments. Near the apical surface the actin bundle curves and runs below the cell membrane. Newly arrived basal body-rootlets tilt upwards out of the microfilament bundle to contact the cell membrane and initiate ciliogenesis. The basal bodies tilt parallel to the flat sides of the rootlets, and away from the direction in which the basal feet point. The actin bundle continues to enlarge during ciliogenesis. These results suggest that basal body migration may be driven by the directed assembly of attached actin filaments.

scholarly journals A myosin-7B–dependent endocytosis pathway mediates cellular entry of α-synuclein fibrils and polycation-bearing cargos

2020 ◽  
Vol 117 (20) ◽  
pp. 10865-10875 ◽  
Author(s):  
Qi Zhang ◽  
Yue Xu ◽  
Juhyung Lee ◽  
Michal Jarnik ◽  
Xufeng Wu ◽  
...  
Keyword(s):  
Cell Surface ◽  
Actin Filaments ◽  
Membrane Dynamics ◽  
Cell Entry ◽  
Sulfate Proteoglycan ◽  
Actin Network ◽  
Coated Pits ◽  
Endocytosis Pathway ◽  
Underlying Mechanisms ◽  
Pathological Event

Cell-to-cell transmission of misfolding-prone α-synuclein (α-Syn) has emerged as a key pathological event in Parkinson’s disease. This process is initiated when α-Syn–bearing fibrils enter cells via clathrin-mediated endocytosis, but the underlying mechanisms are unclear. Using a CRISPR-mediated knockout screen, we identify SLC35B2 and myosin-7B (MYO7B) as critical endocytosis regulators for α-Syn preformed fibrils (PFFs). We show that SLC35B2, as a key regulator of heparan sulfate proteoglycan (HSPG) biosynthesis, is essential for recruiting α-Syn PFFs to the cell surface because this process is mediated by interactions between negatively charged sugar moieties of HSPGs and clustered K-T-K motifs in α-Syn PFFs. By contrast, MYO7B regulates α-Syn PFF cell entry by maintaining a plasma membrane-associated actin network that controls membrane dynamics. Without MYO7B or actin filaments, many clathrin-coated pits fail to be severed from the membrane, causing accumulation of large clathrin-containing “scars” on the cell surface. Intriguingly, the requirement for MYO7B in endocytosis is restricted to α-Syn PFFs and other polycation-bearing cargos that enter cells via HSPGs. Thus, our study not only defines regulatory factors for α-Syn PFF endocytosis, but also reveals a previously unknown endocytosis mechanism for HSPG-binding cargos in general, which requires forces generated by MYO7B and actin filaments.

scholarly journals Helical buckling of actin inside filopodia generates traction

2014 ◽  
Vol 112 (1) ◽  
pp. 136-141 ◽  
Author(s):  
Natascha Leijnse ◽  
Lene B. Oddershede ◽  
Poul M. Bendix
Keyword(s):  
Cell Membrane ◽  
Rotational Motion ◽  
Actin Filaments ◽  
Cell Communication ◽  
Confocal Imaging ◽  
Actin Bundle ◽  
Cellular Processes ◽  
Membrane Protrusions ◽  
A Cell ◽  
Helical Buckling

Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell–cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.

scholarly journals Analysis of the role of microfilaments and microtubules in acquisition of bipolarity and elongation of fibroblasts in hydrated collagen gels.

1984 ◽  
Vol 99 (2) ◽  
pp. 536-549 ◽  
Author(s):  
J J Tomasek ◽  
E D Hay
Keyword(s):  
Actin Cytoskeleton ◽  
Shape Change ◽  
Cell Cortex ◽  
Collagen Gels ◽  
Actin Cortex ◽  
Microtubule Disruption ◽  
Corneal Fibroblasts ◽  
Fourth Step ◽  
Collagenous Stroma

Fibroblasts in situ reside within a collagenous stroma and are elongate and bipolar in shape. If isolated and grown on glass, they change from elongate to flat shape, lose filopodia, and acquire ruffles. This shape change can be reversed to resemble that in situ by suspending the cells in hydrated collagen gels. In this study of embryonic avian corneal fibroblasts grown in collagen gels, we describe for the first time the steps in the acquisition of the elongate shape and analyze the effect of cytoskeleton-disrupting drugs on filopodial activity, assumption of bipolarity, and cell elongation within extracellular matrix. We have previously shown by immunofluorescence that filopodia contain actin but not myosin and are free of organelles. The cell cortex is rich in actin and the cytosol, in myosin. By using antitubulin, we show in the present study that microtubules are aligned along the long axis of the bipolar cell body. The first step in assumption of the elongate shape is extension of filopodia by the round cells suspended in collagen, and this is not significantly affected by the drugs we used: taxol to stabilize microtubules; nocodazole to disassemble microtubules; and cytochalasin D to disrupt microfilaments. The second step, movement of filopodia to opposite ends of the cell, is disrupted by cytochalasin, but not by taxol or nocodazole. The third step, extension of pseudopodia and acquisition of bipolarity similarly requires intact actin, but not microtubules. If fibroblasts are allowed to become bipolar before drug treatment, moreover, they remain so in the presence of the drugs. To complete the fourth step, extensive elongation of the cell, both intact actin and microtubules are required. Retraction of the already elongated cell occurs on microtubule disruption, but retraction requires an intact actin cytoskeleton. We suggest that the cell interacts with surrounding collagen fibrils via its actin cytoskeleton to become bipolar in shape, and that microtubules interact with the actin cortex to bring about the final elongation of the fibroblast.

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