scholarly journals Membrane-MEDYAN: Simulating Deformable Vesicles Containing Complex Cytoskeletal Networks

2021 ◽  
Author(s):  
Haoran Ni ◽  
Garegin A. Papoian
Keyword(s):  
Plasma Membrane ◽  
Leading Edge ◽  
Membrane Dynamics ◽  
New Model ◽  
Biological Matter ◽  
Membrane Cytoskeleton ◽  
Filament Bundles ◽  
Membrane Protrusions ◽  
Cytoskeletal Networks ◽  
Shed Light

AbstractThe plasma membrane defines the shape of the cell and plays an indispensable role in bridging intra- and extra-cellular environments. Mechanochemical interactions between plasma membrane and cytoskeleton are vital for cell biomechanics and mechanosensing. A computational model that comprehensively captures the complex, cell-scale cytoskeleton-membrane dynamics is still lacking. In this work, we introduce a triangulated membrane model that accounts for membrane’s elastic properties, as well as for membrane-filament steric interactions. The corresponding force-field was incorporated into the active biological matter simulation platform, MEDYAN (“Mechanochemical Dynamics of Active Networks”). Simulations using the new model shed light on how actin filament bundling affects generation of tubular membrane protrusions. In particular, we used membrane-MEDYAN simulations to investigate protrusion initiation and dynamics while varying geometries of filament bundles, membrane rigidities and local G-Actin concentrations. We found that bundles’ protrusion propensities sensitively depend on the synergy between bundle thickness and inclination angle at which the bundle approaches the membrane. The new model paves the way for simulations of biological systems involving intricate membrane-cytoskeleton interactions, such as occurring at the leading edge and the cortex, eventually helping to uncover the fundamental principles underlying the active matter organization in the vicinity of the membrane.

Cellular and Molecular Events Underlying the Interaction of Hematopoietic Stem and Progenitor Cells with Mesenchymal Stem Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2309-2309
Author(s):  
Nicola Bauer ◽  
Ana-Violeta Fonseca ◽  
Daniel Freund ◽  
Sabine Boxberger ◽  
Joachim Oswald ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Stem Cell ◽  
Plasma Membrane ◽  
Stem Cell Transplantation ◽  
Leading Edge ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells ◽  
Membrane Protrusions ◽  
Blood Stem Cell Transplantation

Abstract Understanding the mechanisms underlying the reconstitution of the hematopoietic system after blood stem cell transplantation is of crucial importance for improving therapeutic modalities. In order to address these issues, we have recently established a novel co-culture system consisting of immuno-isolated human CD34+ hematopoietic stem and progenitor cells (HSPCs) growing on primary human mesenchymal stem cells (MSCs) as feeder layer in the presence of relevant cytokines. Here we have investigated i) the morphological modification of HSPCs induced by their interaction with MSCs; ii) the sub-cellular localization of the stem cell markers CD34 and CD133 (prominin-1) as well as other cell surface molecules potentially involved in such intercellular interaction, and iii) the intracellular pathway(s) responsible for the migration as well as the interaction of HSPCs with MSCs. The scanning electron microscopy analysis revealed that the adherent HSPCs display various morphologies; they are either round with, in some cases, the appearance of a microvillar pole or exhibit several distinct types of plasma membrane protrusions such as lamellipodium, filopodium and magnupodium. We could also observe very long and thin plasma membrane processes between adjacent HSPCs suggesting the formation of nanotubes, which have been implicated in intercellular communication. As previously reported (Giebel et al., 2004, Blood, 104:2332), the highly motile HSPCs acquire a polarized cell shape with the formation of a uropod at the rear pole and a leading edge at the front pole. The immunofluorescence analyses revealed that CD34 is randomly distributed over the entire surface of HSPCs, irrespective of their morphological shape, whereas CD133 shows various specific sub-cellular localizations, which are depending on the state of the cell. In migrating cells, CD133 is concentrated in the uropod at the rear pole, which contrasts with the enriched localization of the adhesion receptor β2 integrin in the leading edge. In HSPCs harboring other types of plasma membrane protrusions, which are in close contact with the feeder cell layer, CD133 is concentrated therein. In round adhesive cells, CD133 is located in one pole of the cell suggesting that the HSPCs are highly polarized even in the absence of plasma membrane outgrowths. Interestingly, the formation of uropod and microvillus-like structures is highly reduced in presence of Y-27632 inhibitor suggesting that the Rho GTPase/ROCK pathway is somehow involved in the polarization of HSPCs. Time lapse videomicroscopy revealed that the retraction of filopodia is also affected in Y-27632-treated HSPCs as well as their migration. Taken together, these data provide new insights regarding the molecular cell biology of HSPCs, and increase our understanding of cellular events associated with mobilization and engraftment in the context of blood stem cell transplantation.

scholarly journals Measurement of dynamic membrane mechanosensation using optical tweezers

2021 ◽  
Author(s):  
Xuanling Li ◽  
Xing Liu ◽  
Xiaoyu Song ◽  
Yinmei Li ◽  
Ming Li ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Optical Tweezers ◽  
Environmental Changes ◽  
Quantitative Measure ◽  
Relaxation Curve ◽  
Membrane Dynamics ◽  
Molecular Organization ◽  
Cytoskeletal Remodeling ◽  
Relaxation Curves ◽  
Membrane Tether

Abstract Many cellular processes are orchestrated by dynamic changes in the plasma membrane to form membrane projections and endocytic vesicles in response to extracellular environmental changes. Our previous studies show that ARF6-ACAP4-ezrin signaling regulates membrane dynamics and curvature in response to EGF stimulation. However, there is no quantitative measurement to relate molecular organization of membrane cytoskeletal remodeling to stimulus-elicited mechanosensation on the plasma membrane. Optical tweezers is a powerful tool in the study of membrane tension. Comparing to pulling out an entire membrane tether at one time, the step-like method is more efficient because multiple relaxation curves can be obtained from one membrane tether. Fewer models describe relaxation curves to characterize mechanical properties of cell membrane. Here we establish a new method to measure the membrane relaxation curve of HeLa cells judged by the relationship between membrane tether diameter and tensions. We obtained effective viscosities and static tensions by fitting relaxation curves to our model. We noticed the delicate structure of relaxation curves contains information of cytoskeletal remodeling and lateral protein diffusion. Our study established a quantitative measure to characterize the mechanosensation of epithelial cells in response to stimulus-elicited membrane dynamics.

scholarly journals Endocytosis: a review of mechanisms and plasma membrane dynamics

1983 ◽  
Vol 210 (1) ◽  
pp. 1-13 ◽  
Author(s):  
J M Besterman ◽  
R B Low
Keyword(s):  
Plasma Membrane ◽  
Membrane Dynamics

scholarly journals HIV-1 requires Arf6-mediated membrane dynamics to efficiently enter and infect T lymphocytes

2011 ◽  
Vol 22 (8) ◽  
pp. 1148-1166 ◽  
Author(s):  
Laura García-Expósito ◽  
Jonathan Barroso-González ◽  
Isabel Puigdomènech ◽  
José-David Machado ◽  
Julià Blanco ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Lymphocytes ◽  
Viral Entry ◽  
Membrane Trafficking ◽  
Membrane Dynamics ◽  
Viral Fusion ◽  
Viral Attachment ◽  
Immunodeficiency Virus ◽  
Vesicular Stomatitis ◽  
Hiv 1

As the initial barrier to viral entry, the plasma membrane along with the membrane trafficking machinery and cytoskeleton are of fundamental importance in the viral cycle. However, little is known about the contribution of plasma membrane dynamics during early human immunodeficiency virus type 1 (HIV-1) infection. Considering that ADP ribosylation factor 6 (Arf6) regulates cellular invasion via several microorganisms by coordinating membrane trafficking, our aim was to study the function of Arf6-mediated membrane dynamics on HIV-1 entry and infection of T lymphocytes. We observed that an alteration of the Arf6–guanosine 5′-diphosphate/guanosine 5′-triphosphate (GTP/GDP) cycle, by GDP-bound or GTP-bound inactive mutants or by specific Arf6 silencing, inhibited HIV-1 envelope–induced membrane fusion, entry, and infection of T lymphocytes and permissive cells, regardless of viral tropism. Furthermore, cell-to-cell HIV-1 transmission of primary human CD4+T lymphocytes was inhibited by Arf6 knockdown. Total internal reflection fluorescence microscopy showed that Arf6 mutants provoked the accumulation of phosphatidylinositol-(4,5)-biphosphate–associated structures on the plasma membrane of permissive cells, without affecting CD4-viral attachment but impeding CD4-dependent HIV-1 entry. Arf6 silencing or its mutants did not affect fusion, entry, and infection of vesicular stomatitis virus G–pseudotyped viruses or ligand-induced CXCR4 or CCR5 endocytosis, both clathrin-dependent processes. Therefore we propose that efficient early HIV-1 infection of CD4+T lymphocytes requires Arf6-coordinated plasma membrane dynamics that promote viral fusion and entry.

scholarly journals The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans

PLoS Genetics ◽  
2016 ◽  
Vol 12 (4) ◽  
pp. e1006010 ◽  
Author(s):  
Serena A. D’Souza ◽  
Luckshi Rajendran ◽  
Rachel Bagg ◽  
Louis Barbier ◽  
Derek M. van Pel ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Caenorhabditis Elegans ◽  
Map Kinase ◽  
Motor Neurons ◽  
Leading Edge ◽  
P38 Map Kinase ◽  
Endosomal Trafficking ◽  
Guidance Cue ◽  
Map Kinase Pathway ◽  
Kinase Pathway

The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle’s plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue.

scholarly journals Subcellular optogenetic activation of Cdc42 controls local and distal signaling to drive immune cell migration

2016 ◽  
Vol 27 (9) ◽  
pp. 1442-1450 ◽  
Author(s):  
Patrick R. O’Neill ◽  
Vani Kalyanaraman ◽  
N. Gautam
Keyword(s):  
Cell Migration ◽  
Intracellular Signaling ◽  
Immune Cell ◽  
Leading Edge ◽  
Signaling Networks ◽  
Membrane Protrusions ◽  
A Cell ◽  
Immune Cell Migration ◽  
Directional Cell Migration ◽  
Rhoa Signaling

Migratory immune cells use intracellular signaling networks to generate and orient spatially polarized responses to extracellular cues. The monomeric G protein Cdc42 is believed to play an important role in controlling the polarized responses, but it has been difficult to determine directly the consequences of localized Cdc42 activation within an immune cell. Here we used subcellular optogenetics to determine how Cdc42 activation at one side of a cell affects both cell behavior and dynamic molecular responses throughout the cell. We found that localized Cdc42 activation is sufficient to generate polarized signaling and directional cell migration. The optically activated region becomes the leading edge of the cell, with Cdc42 activating Rac and generating membrane protrusions driven by the actin cytoskeleton. Cdc42 also exerts long-range effects that cause myosin accumulation at the opposite side of the cell and actomyosin-mediated retraction of the cell rear. This process requires the RhoA-activated kinase ROCK, suggesting that Cdc42 activation at one side of a cell triggers increased RhoA signaling at the opposite side. Our results demonstrate how dynamic, subcellular perturbation of an individual signaling protein can help to determine its role in controlling polarized cellular responses.

scholarly journals Blebs Promote Cell Survival by Assembling Oncogenic Signaling Hubs

2021 ◽  
Author(s):  
Andrew D. Weems ◽  
Erik S. Welf ◽  
Meghan K. Driscoll ◽  
Hanieh Mazloom-Farsibaf ◽  
Bo-Jui Chang ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Surrounding Tissue ◽  
Pi3k Signaling ◽  
Oncogenic Signaling ◽  
Anoikis Resistance ◽  
Cancer Disease ◽  
Substrate Adhesion ◽  
Promote Cell Survival ◽  
Membrane Protrusions ◽  
Signaling Organelles

AbstractFor most human cells, anchorage is a key necessity for survival. Cell-substrate adhesion activates diverse signaling pathways, without which cells undergo anoikis – a form of programmed cell death1. Acquisition of anoikis resistance is a pivotal step in cancer disease progression, as metastasizing cancer cells often lose firm attachment to surrounding tissue2–5. In these poorly attached states, cells often adopt rounded morphologies and form small hemispherical plasma membrane protrusions called blebs6–13. Bleb function has long been investigated in the context of amoeboid migration but is far less deeply examined in other scenarios14–19. Here we show by quantitative subcellular 3D imaging and manipulation of cell morphological states that blebbing triggers the formation of membrane-proximal signaling hubs that initiate signaling cascades leading to anoikis resistance. Specifically, in melanoma cells we discovered that blebbing generates plasma membrane contours that recruit curvature sensing septin proteins, which scaffold constitutively active mutant NRAS and effectors, driving the upregulation of ERK and PI3K signaling. Inhibition of blebs or septins has little effect on the survival of well-adhered cells, but in detached cells causes NRAS mislocalization, reduced MAPK and PI3K signaling, and ultimately, death. These data unveil an unanticipated morphological requirement for mutant NRAS to operate as an effective oncoprotein, suggesting novel clinical targets for the treatment of NRAS-driven melanoma. Furthermore, they define an unforeseen role for blebs as potent signaling organelles capable of integrating myriad cellular information flows into concerted signaling responses, in this case granting robust anoikis resistance.Abstract Figure

scholarly journals Organization of talin and vinculin in adhesion plaques of wet-cleaved chicken embryo fibroblasts

1991 ◽  
Vol 100 (3) ◽  
pp. 579-587 ◽  
Author(s):  
C.A. Feltkamp ◽  
M.A. Pijnenburg ◽  
E. Roos
Keyword(s):  
Chicken Embryo ◽  
Close Contact ◽  
Membrane Cytoskeleton ◽  
Cytoskeletal Network ◽  
Microfilament Bundles ◽  
Filament Bundles ◽  
Adhesion Plaques ◽  
Embryo Fibroblasts ◽  
Surrounding Membrane ◽  
Chicken Embryo Fibroblasts

We have studied the fine structure of adhesion plaques in chicken embryo fibroblasts (CEF) and visualized the localization of vinculin and talin using immunoelectron microscopy on CEF opened by ‘wet-cleaving’. This procedure, performed with nitrocellulose on cells grown on electron microscope grids, cleaved the CEF close to the inner face of the ventral membrane or at a slightly higher level through the cytoplasm. In the resulting preparations, adhesion plaques were identified by their localization at the end of microfilament bundles and by their density of vinculin and talin. The plaques showed a substructure of moderately electron-dense parallel bands that were interconnected. Both the parallel bands as well as the interconnecting threads showed a high density of vinculin and talin labels, whereas neither the surrounding membrane cytoskeleton nor the overlaying bundled microfilaments were labeled. In stereomicrographs, we observed no difference between the distances from vinculin or talin label, respectively, to the plasma membrane. In early spreading cells, vinculin and talin were found to be deposited simultaneously in fine radiating streaks that covered rather large parts of the ventral membrane at areas of close contact with the substratum. These streaks, which were initially overlayed by an isotropic cytoskeletal network without filament bundles, were the apparent precursors of later formed adhesion plaques. These observations suggest that there are no separate layers of talin and vinculin, but rather that adhesion plaques consist of a dense network of talin and vinculin. The observations strongly support the model proposed by Bendori et al. (1989), J. Cell Biol. 108, 2383–2393, that was based on the location of vinculin- and talin-binding sites in the vinculin molecule.

Neurofibromatosis 2 tumor suppressor protein colocalizes with ezrin and CD44 and associates with actin-containing cytoskeleton

1997 ◽  
Vol 110 (18) ◽  
pp. 2249-2260 ◽  
Author(s):  
M. Sainio ◽  
F. Zhao ◽  
L. Heiska ◽  
O. Turunen ◽  
M. den Bakker ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Tumor Suppressor ◽  
Cytochalasin B ◽  
Insoluble Fraction ◽  
Tumor Suppressor Protein ◽  
Homologous Proteins ◽  
Neurofibromatosis 2 ◽  
Erm Proteins ◽  
293 Cells ◽  
Membrane Protrusions

Neurofibromatosis 2 (NF2) protein (merlin; schwannomin) is a tumor suppressor involved in tumorigenesis of NF2-associated and sporadic schwannomas and meningiomas. The protein shares the domain structure of three homologous proteins: ezrin, radixin and moesin (ERM). ERM proteins function as membrane organizers and may act as linkers between plasma membrane molecules, such as CD44 and ICAM-2, and the cytoskeleton. We analyzed the distribution and effects of transfected NF2 protein in COS-1, CHO and 293 cells, and endogenous NF2 protein in U251 glioma cells. The distribution was compared to ezrin, CD44 and F-actin. Both transfected and endogenous NF2 protein localized underneath the plasma membrane in a pattern typical of an ERM protein. In COS-1 transfectants, NF2 protein typically codistributed with ezrin but, in cells with poorly developed actin cytoskeleton, it replaced ezrin in filopodia and ruffling edges. NF2 protein colocalized with CD44, which in transfected cells accumulated into restructured cell membrane protrusions. The association of CD44 and NF2 protein was further suggested by binding of CD44 from cellular lysates to recombinant NF2 protein. Interaction between NF2 protein and the actin-containing cytoskeleton was indicated by partial colocalization, by cytochalasin B-induced coclustering, and by retention of NF2 protein in the detergent-insoluble fraction. Transfected NF2 protein induced morphogenic changes. The cells contained restructured membrane extensions and blebs, and CHO cells expressing NF2 protein were more elongated than control transfectants. In conclusion, NF2 protein possesses functional properties of an ERM family member.

Ultrastructural Changes in the Surface Layers of the Newt's Egg in Relation to the Mechanism of Its Cleavage

1970 ◽  
Vol 6 (1) ◽  
pp. 207-227 ◽  
Author(s):  
G. G. SELMAN ◽  
M. M. PERRY
Keyword(s):  
Plasma Membrane ◽  
Leading Edge ◽  
Ultrastructural Changes ◽  
Cortical Layers ◽  
Active Growth ◽  
Structural Modifications ◽  
Cell Cleavage ◽  
Surface Irregularities ◽  
Dense Band ◽  
10 Nm Filaments

The surface and cortical layers of an uncleaved newt egg have a characteristic ultrastructure which remains unaltered during cleavage; ultrastructural changes are confined to the region of the furrow. At the onset of cleavage there is a dipping inwards of the rough heavily pigmented animal surface to form a groove. Along the bottom of the groove the surface irregularities are reduced and a dense band (0.1 µm thick and 16 µm wide) is formed immediately below the plasma membrane. Within this band there are parallel filaments, 8-10 nm in diameter, oriented in the direction of the future furrow. No structural modifications were observed below the cortical layers of the leading part of the furrow apart from accumulations of granules and the mid-bodies of the spindle remnant. It is proposed that the dipping-in of the groove is due to contraction within the filamentous band, rather than contraction in a sheet of subcortical gel as proposed previously. The filamentous band persists below the furrow during the later stages of cleavage. The new unpigmented surface first forms as a strip across the animal surface and begins to grow at the bottom of the groove. Over most of its area, it is much smoother than the pigmented surface and has less material on the outside of the plasma membrane. There are microvilli along the bottom of the groove. The join between the new unpigmented and the old pigmented surface is abrupt. As the new unpigmented surface grows in extent, a narrow furrow forms below the lowest part of the groove and progresses towards the vegetal surface. For most of its length the furrow is between 10-nm and 0.5 µm wide, but at its leading edge it is 2 µ wide with microvilli on its surface and 10-nm filaments below the plasma membrane. It is concluded that the progressive formation of the furrow is due to active growth of new unpigmented cell surface. At late cleavage a ridge 10 µm high forms at the join between the new and old surface. After cleavage the ridges approach and meet to form the intercellular junction by which daughter blastomeres are held together along the animal surface. The mechanism of cell cleavage in the newt egg and in other forms is discussed in the light of the present observations.

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