scholarly journals Substrate properties modulate cell membrane roughness by way of actin filaments

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Chao-Hung Chang ◽  
Hsiao-Hui Lee ◽  
Chau-Hwang Lee
Keyword(s):  
Cell Membrane ◽  
Actin Filaments ◽  
Substrate Properties ◽  
Membrane Roughness

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 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 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 Effective Cell Membrane Tension is Independent of Substrate Stiffness

2021 ◽  
Author(s):  
Eva Kreysing ◽  
Jeffrey Mc Hugh ◽  
Sarah K. Foster ◽  
Kurt Andresen ◽  
Ryan D. Greenhalgh ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Optical Tweezers ◽  
Substrate Stiffness ◽  
Membrane Tension ◽  
Animal Cells ◽  
Traction Forces ◽  
Cortical Tension ◽  
Cellular Processes ◽  
Substrate Properties ◽  
Cells Cultured

Most animal cells are surrounded by a cell membrane and an underlying actomyosin cortex. Both structures are linked with each other, and they are under tension. Membrane tension and cortical tension both influence many cellular processes, including cell migration, division, and endocytosis. However, while actomyosin tension is regulated by substrate stiffness, how membrane tension responds to mechanical substrate properties is currently poorly understood. Here, we probed the effective membrane tension of neurons and fibroblasts cultured on glass and polyacrylamide substrates of varying stiffness using optical tweezers. In contrast to actomyosin-based traction forces, both peak forces and steady state tether forces of cells cultured on hydrogels were independent of substrate stiffness and did not change after blocking myosin II activity using blebbistatin, indicating that tether and traction forces are not directly linked with each other. Peak forces on hydrogels were about twice as high in fibroblasts if compared to neurons, indicating stronger membrane-cortex adhesion in fibroblasts. Finally, tether forces were generally higher in cells cultured on hydrogels compared to cells cultured on glass, which we attribute to substrate-dependent alterations of the actomyosin cortex and an inverse relationship between tension along stress fibres and cortical tension. Our results provide new insights into the complex regulation of membrane tension, and they pave the way for a deeper understanding of biological processes instructed by it.

Tyrosine phosphorylation of the dense plaque protein paxillin is regulated during smooth muscle contraction

1996 ◽  
Vol 271 (5) ◽  
pp. C1594-C1602 ◽  
Author(s):  
Z. Wang ◽  
F. M. Pavalko ◽  
S. J. Gunst
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Tyrosine Phosphorylation ◽  
Actin Filaments ◽  
Time Course ◽  
Smooth Muscle Contraction ◽  
External Stress ◽  
Force Development ◽  
Contraction And Relaxation

Regulation of the attachment of actin filaments to the cell membrane at membrane-associated dense plaque (MADP) sites could allow smooth muscle cells to modulate their cytostructure in response to changes in external stress. In this study, changes in the tyrosine phosphorylation of the MADP protein paxillin were measured by Western blot during the contraction and relaxation of tracheal smooth muscle strips. Tyrosine phosphorylation of paxillin increased by three- to fourfold with a time course similar to force development during contractile stimulation with acetylcholine (ACh), 5-hydroxytryptamine, and KCl and decreased during washout of contractile stimuli and during relaxation induced by forskolin. Immunoprecipitation of muscle extracts with multiple rounds of anti-phosphotyrosine antibody removed approximately 20% of the total paxillin in resting muscles and approximately 60% of paxillin in muscles maximally stimulated with ACh. These results provide the first evidence associating the tyrosine phosphorylation of paxillin with the active contraction of smooth muscle or with any functional response of a fully differentiated tissue in vivo. The results are consistent with a role for MADP proteins in the regulation of force development in smooth muscle.

LOCOMOTION OF A TWO DIMENSIONAL KERATOCYTE MODEL

2001 ◽  
Vol 09 (03) ◽  
pp. 201-219 ◽  
Author(s):  
R. SAMBETH ◽  
A. BAUMGAERTNER
Keyword(s):  
Cell Membrane ◽  
Actin Filaments ◽  
Structural Organization ◽  
Constant Flow ◽  
Nonequilibrium Distribution ◽  
Cell Velocity ◽  
Model Cell ◽  
A Cell ◽  
Asymmetric Polymerization ◽  
Rectification Process

The polymerization-induced propulsion of a model cell consisting of a cell membrane enclosing mobile actin molecules and polymerizing actin filaments is studied using Monte Carlo methods. It is shown that asymmetric polymerization alone induces a rectified motion of the cell. The structural organization of the locomoting cell exhibits an anisotropic shape induced by the anisotropic distribution of actin within the cell. This nonequilibrium distribution is maintained by a constant flow of actin molecules from the rear to the front of the cell. The efficiency of the rectification process, and hence the cell velocity, depends cooperatively on the density of actin molecules. The maximum of the cell velocity is determined by the optimal interplay between the number of filaments and the fluctuation of the cell membrane.

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.

Variation of the Rate of Extension of Actin Networks

1996 ◽  
Vol 463 ◽  
Author(s):  
Donald J. Olbris ◽  
Judith Herzfeld
Keyword(s):  
Fluid Flow ◽  
Cell Membrane ◽  
Actin Filaments ◽  
Sea Cucumber ◽  
Diffusive Flux ◽  
Bulk Fluid ◽  
Actin Networks ◽  
Self Assembling ◽  
Wide Range ◽  
Diffusive Movement

ABSTRACTSelf-assembling protein filaments are important components of a cell's superstructure. Among these, actin filaments form the backbone of protrusions and extensions such as pseudopodia. The rates at which these structures extend cover a startlingly wide range: the acrosomal process of the sea cucumber may extend 90 μm in 10 seconds, which is more than 20 times the speed at which an epithelial goldfish keratocyte crawls. We seek to explain this range by examining the delivery of actin monomers to the growing filament ends. We show that the diffusive flux of actin monomers is adequate for fueling the slower movement of crawling cells, but is insufficient to propel the quicker acrosomal process of the sea cucumber. By introducing bulk fluid flow in response to the diffusive movement of water through the cell membrane, actin delivery can be enhanced. We compare the calculated speeds to experimental observations and discuss future refinements to the model.

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