Differences in Cortical Actin Structure and Dynamics Document That Different Types of Blebs Are Formed by Distinct Mechanisms

2002 ◽  
Vol 277 (2) ◽  
pp. 161-172 ◽  
Author(s):  
Hansuli Keller ◽  
Patrick Rentsch ◽  
Jörg Hagmann
Keyword(s):  
Cortical Actin ◽  
Structure And Dynamics ◽  
Different Types ◽  
Actin Structure

scholarly journals Actin polymerization and intracellular solvent flow in cell surface blebbing.

1995 ◽  
Vol 129 (6) ◽  
pp. 1589-1599 ◽  
Author(s):  
C C Cunningham
Keyword(s):  
Cell Surface ◽  
Actin Polymerization ◽  
Surface Membrane ◽  
Control Cell ◽  
Cortical Actin ◽  
Final Size ◽  
Actin Structure ◽  
Close Study ◽  
A Cell ◽  
Solvent Flow

The cortical actin gel of eukaryotic cells is postulated to control cell surface activity. One type of protrusion that may offer clues to this regulation are the spherical aneurysms of the surface membrane known as blebs. Blebs occur normally in cells during spreading and alternate with other protrusions, such as ruffles, suggesting similar protrusive machinery is involved. We recently reported that human melanoma cell lines deficient in the actin filament cross-linking protein, ABP-280, show prolonged blebbing, thus allowing close study of blebs and their dynamics. Blebs expand at different rates of volume increase that directly predict the final size achieved by each bleb. These rates decrease as the F-actin concentration of the cells increase over time after plating on a surface, but do so at lower concentrations in ABP-280 expressing cells. Fluorescently labeled actin and phalloidin injections of blebbing cells indicate that a polymerized actin structure is not present initially, but appears later and is responsible for stopping further bleb expansion. Therefore, it is postulated that blebs occur when the fluid-driven expansion of the cell membrane is sufficiently rapid to initially outpace the local rate of actin polymerization. In this model, the rate of intracellular solvent flow driving this expansion decreases as cortical gelation is achieved, whether by factors such as ABP-280, or by concentrated actin polymers alone, thereby leading to decreased size and occurrence of blebs. Since the forces driving bleb extension would always be present in a cell, this process may influence other cell protrusions as well.

scholarly journals Archival phonograms on the musical radio as a type of service auditory documents

2020 ◽  
pp. 252-264
Author(s):  
Olexandr Mazur
Keyword(s):  
Modern Science ◽  
Classification Problem ◽  
Research Field ◽  
Research Approach ◽  
Auditory Information ◽  
Cultural Institutions ◽  
Advantages And Disadvantages ◽  
Structure And Dynamics ◽  
Different Types ◽  
Music Information

In modern high-technology conditions entire process of creating, circulation and distribution of the auditory information, accumulated in phonograms, inherits integration properties that stipulate internal unity of the structure and dynamics of the phonodocumental communication. The research, performed within the framework of Document studies, Archive studies and Musical Art, dedicated to the development of the sound recording classification problem in communication area from the position of archival phonograms selection on the musical radio as a special type of service auditory documents with specific features — types of sound carriers, specifics of the fixed sound content and specifics of the service functions. The publication develops the applying of the informational approach archival radio phonodocuments that currently stay on the periphery of the research interest even comparing to other types of the tecehnotronic documents — pictorial, audiovisual, electronic information sources, different types of the technical documentation.Phonodocumental communication has features of the complicated open area. According to the author’s idea disconnected elements from the radio sector, that were organically collected together and integrated to the balanced phonodocumental communication system. The essence and the purpose of such types of the phonoduments are clarified, also the main regularities of the formation and principles of the classification were formulated. Moreover, based on the fact that radioarchives and some other cultural institutions perform functional of the music information complex repository, this article tells about music sources preservation technologies not only in the radio copmanies archives but in libraries, museums, etc. The expansion of the research field at the expense of the advanced systematization of advantages and disadvantages of the archival radiophonogram consumer format revision was begun. The research approach that was the basis for publication helps to overcome some differences including modern science and educational literature. Keywords: Archive, Audiodocuments, Music, Radio, Service,Phonogram.

Ecological networks: From structure to dynamics

2020 ◽  
pp. 143-160
Author(s):  
Sonia Kéfi
Keyword(s):  
Mathematical Models ◽  
Numerical Simulations ◽  
Network Structure ◽  
Ecological Systems ◽  
Ecological Networks ◽  
Ecological Communities ◽  
Ecological Dynamics ◽  
Structure And Dynamics ◽  
Different Types ◽  
Recent Developments

Ecological systems are undeniably complex, including many species interacting in different ways with each other (e.g., predation, competition, facilitation, parasitism). One way of visualizing, describing, and studying this complexity is to represent them as networks, where nodes are typically species and links are interactions between these species. The study of these networks allows understanding of the rules governing the topology of their links, and assessing how network structure drives ecological dynamics. Studies on different types of ecological networks have suggested that they exhibit structural regularities, which in turn affect network dynamics and resilience to perturbations. Although the use of networks to represent ecological communities dates back to the early stages of the discipline, the last two decades have seen rapid progresses in our understanding of ecological networks, as data are collected at a faster rate and better resolution, as metrics are continuously developed to better characterize network structure and as numerical simulations of mathematical models have allowed investigating how network structure and dynamics are related in more comprehensive and realistic ecological networks. This chapter describes some of the recent developments and challenges related to the study of ecological networks. After defining networks in general, and ecological networks more specifically, recent results regarding the structure of different types of ecological networks, and what is known about their dynamics and resilience, are presented.

Possible role of a septin, SEPT1, in spreading in squamous cell carcinoma DJM-1 cells

2013 ◽  
Vol 394 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Yoko Mizutani ◽  
Hidenori Ito ◽  
Ikuko Iwamoto ◽  
Rika Morishita ◽  
Hiroyuki Kanoh ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Cortical Actin ◽  
Cell Substrate ◽  
Actin Structure ◽  
Normal Human ◽  
Immunohistochemical Analyses

Abstract We performed biochemical, histochemical and cell biological characterization of septins by focusing on SEPT1 in human skin tissues and a squamous cell carcinoma (SCC) cell line DJM-1. In immunoblotting, SEPT1, together with other septins, was detected in normal human epidermis, SCC and DJM-1. In immunohistochemical analyses, SEPT1 was detected diffusely in the cytoplasm of human epidermal cells and eccrine gland epithelial cells, and the protein level was increased in some skin tumors. In DJM-1 cells, SEPT1 together with other members of SEPT2-subgroup, SEPT4 and SEPT5, was enriched in lamellipodia and the localization was dependent on the cortical actin structure. SEPT1 distribution at lamellipodia was also observed in melanoma B16 cells. SEPT9, SEPT11 and SEPT14, in contrast, were localized along with microtubules in DJM-1 cells. In immunoprecipitation assays, SEPT1 and SEPT5 were found to form a complex in DJM-1 cells, whereas SEPT9, SEPT11 and SEPT14 formed a distinct complex with other septins including SEPT7, SEPT8 and SEPT10, in which SEPT5 was not included. When SEPT1 was silenced in DJM-1 cells, cell spreading was inhibited. These results suggest that SEPT1 may participate in cell-cell and/or cell-substrate interaction in DJM-1 and exert its function in a coordinated manner with other septins.

scholarly journals Loss of cortical actin filaments in insulin-resistant skeletal muscle cells impairs GLUT4 vesicle trafficking and glucose transport

2006 ◽  
Vol 291 (5) ◽  
pp. C860-C868 ◽  
Author(s):  
Alicia M. McCarthy ◽  
Kristen O. Spisak ◽  
Joseph T. Brozinick ◽  
Jeffrey S. Elmendorf
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Insulin Resistant ◽  
Actin Structure ◽  
Insulin Responsiveness

Study has demonstrated an essential role of cortical filamentous actin (F-actin) in insulin-regulated glucose uptake by skeletal muscle. Here, we tested whether perturbations in F-actin contributed to impaired insulin responsiveness provoked by hyperinsulinemia. In L6 myotubes stably expressing GLUT4 that carries an exofacial myc-epitope tag, acute insulin stimulation (20 min, 100 nM) increased GLUT4myc translocation and glucose uptake by ∼2-fold. In contrast, a hyperinsulinemic state, induced by inclusion of 5 nM insulin in the medium for 12 h decreased the ability of insulin to stimulate these processes. Defects in insulin signaling did not readily account for the observed disruption. In contrast, hyperinsulinemia reduced cortical F-actin. This occurred concomitant with a loss of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2), a lipid involved in cytoskeletal regulation. Restoration of plasma membrane PIP2 in hyperinsulinemic cells restored F-actin and insulin responsiveness. Consistent with these in vitro observations suggesting that the hyperinsulinemic state negatively affects cortical F-actin structure, epitrochlearis skeletal muscle from insulin-resistant hyperinsulinemic Zucker fatty rats displayed a similar loss of F-actin structure compared with that in muscle from lean insulin-sensitive littermates. We propose that a component of insulin-induced insulin resistance in skeletal muscle involves defects in PIP2/F-actin structure essential for insulin-regulated glucose transport.

scholarly journals Yeast actin patches are networks of branched actin filaments

2004 ◽  
Vol 166 (5) ◽  
pp. 629-635 ◽  
Author(s):  
Michael E. Young ◽  
John A. Cooper ◽  
Paul C. Bridgman
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Branch Ratio ◽  
Actin Assembly ◽  
Cortical Actin ◽  
Capping Protein ◽  
Negative Stain ◽  
Actin Structure ◽  
Negative Stain Electron Microscopy ◽  
Actin Patch

Cortical actin patches are the most prominent actin structure in budding and fission yeast. Patches assemble, move, and disassemble rapidly. We investigated the mechanisms underlying patch actin assembly and motility by studying actin filament ultrastructure within a patch. Actin patches were partially purified from Saccharomyces cerevisiae and examined by negative-stain electron microscopy (EM). To identify patches in the EM, we correlated fluorescence and EM images of GFP-labeled patches. Patches contained a network of actin filaments with branches characteristic of Arp2/3 complex. An average patch contained 85 filaments. The average filament was only 50-nm (20 actin subunits) long, and the filament to branch ratio was 3:1. Patches lacking Sac6/fimbrin were unstable, and patches lacking capping protein were relatively normal. Our results are consistent with Arp2/3 complex-mediated actin polymerization driving yeast actin patch assembly and motility, as described by a variation of the dendritic nucleation model.

scholarly journals Lipid Raft Targeting of the TC10 Amino Terminal Domain Is Responsible for Disruption of Adipocyte Cortical Actin

2003 ◽  
Vol 14 (9) ◽  
pp. 3578-3591 ◽  
Author(s):  
June Chunqiu Hou ◽  
Jeffrey E. Pessin
Keyword(s):  
Lipid Raft ◽  
Inhibitory Effect ◽  
Detectable Effect ◽  
Glut4 Translocation ◽  
Cortical Actin ◽  
Structural Determinants ◽  
Actin Organization ◽  
Amino Terminal ◽  
Actin Structure ◽  
Lipid Raft Microdomains

Overexpression of the Rho family member TC10α, disrupts adipocyte cortical actin structure and inhibits insulin-stimulated GLUT4 translocation when targeted to lipid raft microdomains. This appears to be independent of effecter domain function because overexpression of the wild-type (TC10/WT), constitutively GTP-bound (TC10/Q75L), and constitutively GDP bound (TC10/T31N) all inhibit adipocyte cortical actin structure and GLUT4 translocation. To examine the structural determinants responsible for these effects, we generated a series of chimera proteins between TC10 with that of H-Ras and K-Ras. Chimera containing the 79 (TC10–79/H-Ras), 41 (TC10–41/H-Ras), or 16 (TC10–16/H-Ras) amino acids of the TC10 amino terminal extension fused to H-Ras disrupted cortical actin and inhibited insulin-stimulated GLUT4 translocation. In contrast, the same amino terminal TC10 extensions fused to K-Ras had no significant effect on either GLUT4 translocation or cortical actin structure. Similarly, expression of TC10β was without effect, whereas fusion of the amino terminal 8 amino acid of TC10α onto TC10β resulted in an inhibition of insulin-stimulated GLUT4 translocation. Within the amino terminal extension point mutation analysis demonstrated that both a GAG and GPG sequences when lipid raft targeted was essential for these effects. Furthermore, expression of the amino terminal TC10 deletions ΔNT-TC10/WT or ΔNT-TC10/T31N had no detectable effect on cortical actin organization and did not perturb insulin-stimulated GLUT4 translocation. Surprisingly, however, expression of ΔNT-TC10/Q75L remained fully capable of inhibiting insulin-stimulated GLUT4 translocation without affecting cortical actin. These data demonstrate that inhibitory effect of TC10 overexpression on adipocyte cortical actin organization is due to the specific lipid raft targeting of the unusual TC10 amino terminal extension.

scholarly journals An actin nucleation complex catalyzes filament formation at sites of exocytosis

2019 ◽  
Author(s):  
Oliver Glomb ◽  
Yehui Wu ◽  
Lucia Rieger ◽  
Diana Rüthnick ◽  
Medhanie Mulaw ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Yeast Cells ◽  
Filament Formation ◽  
Cortical Actin ◽  
Peroxisomal Membrane ◽  
Directed Movement ◽  
Vesicle Docking ◽  
Actin Structure ◽  
Local Enrichment ◽  
Actin Cables

AbstractDue to the local enrichment of factors that influence its formation, dynamics, and organization, the actin cytoskeleton displays different shapes and functions within the same cell. In yeast cells post-Golgi vesicles ride on long actin cables to the bud tip. The scaffold proteins Boi1 and Boi2 participate in tethering and docking these vesicles to the plasma membrane. Here we show that Boi1/2 also recruit nucleation and elongation factors to form actin filaments at sites of exocytosis. Disrupting the physical connection between Boi1/2 and the nucleation factor Bud6 impairs filament formation in the bud, reduces the directed movement of the vesicles to the tip, and shortens their tethering time at the cortex. Artificially transplanting Boi1 from the bud tip to the peroxisomal membrane partially redirects the actin cytoskeleton and the vesicular flow towards the peroxisome, and creates an alternative, rudimentary vesicle-docking zone. We conclude that Boi1/2 is sufficient to induce the formation of a cortical actin structure that receives and aligns incoming vesicles before fusing with the membrane.

Simulation of a subtropical cyclone using the HARMONIE-AROME model

2021 ◽  
Author(s):  
Mariano Sastre ◽  
Javier Díaz Fernández ◽  
Lara Quitián Hernández ◽  
Pedro Bolgiani ◽  
Daniel Santos-Muñoz ◽  
...  
Keyword(s):  
Satellite Images ◽  
Complex Dynamics ◽  
Thermal Structure ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Economic Losses ◽  
Rapid Intensification ◽  
Structure And Dynamics ◽  
Different Types ◽  
Research Consortium

<p>According to their thermal structure and dynamics, different types of tropospheric cyclones can be defined. Subtropical cyclones (STC) are low pressure systems that share tropical and extratropical characteristics, having a hybrid thermal structure. The impacts of this kind of cyclones are typically like the ones due to tropical storms or even hurricanes, leading to widespread social damage and significant economic losses. Moreover, because of its complex dynamics and rapid intensification, these systems remain a phenomenon of interest, as well as a challenge in terms of prediction. Consequently, effective numerical model simulations become the key tool in order to reliably forecast these extreme events. In this study, a STC event, which occurred in October 2014 nearby the Canary Islands, is assessed by means of the high-resolution numerical weather prediction model HARMONIE-AROME, which is currently operated at 2.5 km grid resolution. This model was developed in the framework of the collaboration of the ten European National Meteorological Services that belong to the HIRLAM international research consortium, together with the sixteen countries that comprise the ALADIN consortium. To evaluate the performance of the simulation, airport observations and sounding data in the vicinity of the STC are considered for local analyses, and satellite images are used to assess the global cloudiness arrangement.</p>

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