Repairing a torn cell surface: make way, lysosomes to the rescue

2002 ◽  
Vol 115 (5) ◽  
pp. 873-879 ◽  
Author(s):  
Paul L. McNeil
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Actin Polymerization ◽  
Surface Membrane ◽  
Cell Cortex ◽  
Yolk Granule ◽  
Protein Markers ◽  
Filamentous Actin ◽  
Animal Cells ◽  
Fusion Plasma

Biological membranes are often described as `self-sealing' structures. If indeed membranes do have an inherent capacity for repair, does this explain how a cell can rapidly reseal a very large (1-1000 μm2)disruption in its plasma membrane? It is becoming increasingly clear that, in nucleated animal cells, the cytoplasm plays an active and essential role in resealing. A rapid and apparently chaotic membrane fusion response is initiated locally in the cytoplasm by the Ca2+ that floods in through a disruption: cytoplasmic vesicles are thereby joined with one another(homotypically) and with the surrounding plasma membrane (exocytotically). As a consequence, internal membrane is added to cell surface membrane at the disruption site. In the case of large disruptions, this addition is hypothesized to function as a `patch'. In sea urchin eggs, the internal compartment used is the yolk granule. Several recent studies have significantly advanced our understanding of how cells survive disruption-inducing injuries. In fibroblasts, the lysosome has been identified as a key organelle in resealing. Protein markers of the lysosome membrane appear on the surface of fibroblasts at sites of disruption. Antibodies against lysosome-specific proteins, introduced into the living fibroblast,inhibit its resealing response. In gastric eptithelial cells, local depolymerization of filamentous actin has been identified as a crucial step in resealing: it may function to remove a barrier to lysosome-plasma membrane contact leading to exocytotic fusion. Plasma membrane disruption in epithelial cells induces depolymerization of cortical filamentous actin and, if this depolymerization response is inhibited, resealing is blocked. In the Xenopus egg, the cortical cytoskeleton has been identified as an active participant in post-resealing repair of disruption-related damage to underlying cell cortex. A striking, highly localized actin polymerization response is observable around the margin of cortical defects. A myosin powered contraction occurring within this newly formed zone of F-actin then drives closure of the defect in a purse-string fashion.

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 Surface redistribution and release of antibody-induced caps in entamoebae.

1980 ◽  
Vol 151 (1) ◽  
pp. 184-193 ◽  
Author(s):  
J Calderón ◽  
M de Lourdes Muñoz ◽  
H M Acosta
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Surface Segregation ◽  
Surface Membrane ◽  
Single Layer ◽  
Surface Antigens ◽  
Spontaneous Release ◽  
Plasma Membrane Regeneration ◽  
Membrane Components ◽  
Radiolabeled Antibodies

Polyspecific antibodies bound to Entamoeba induced surface redistribution of membrane components toward the uroid region. Capping of surface antigens was obtained with a single layer of antibodies in E. histolytica and E. invadens. This surface segregation progressed to a large accumulation of folded plasma membrane that extruded as a defined vesicular cap. A spontaneous release of the cap at the end of the capping process took place. These released caps contained most of the antibodies that originally bound to the whole cell surface. Two-thirds of radiolabeled antibodies bound to the surface of E. histolytica were released into the medium in 2 h. Successive capping induced by repeated exposure of E. invadens to antibodies produced conglomerates of folded surface membrane, visualized as stacked caps, in proportion to the number of antibody exposures. These results indicate the remarkable ability of Entamoeba to rapidly regenerate substantial amounts of plasma membbrane. The properties of surface redistribution, liberation of caps, and plasma membrane regeneration, may contribute to the survival of the parasite in the host during infection.

scholarly journals Arp2/3- and Cofilin-coordinated Actin Dynamics Is Required for Insulin-mediated GLUT4 Translocation to the Surface of Muscle Cells

2010 ◽  
Vol 21 (20) ◽  
pp. 3529-3539 ◽  
Author(s):  
Tim Ting Chiu ◽  
Nish Patel ◽  
Alisa E. Shaw ◽  
James R. Bamburg ◽  
Amira Klip
Keyword(s):  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Muscle Cells ◽  
Actin Dynamics ◽  
Cell Cortex ◽  
Glut4 Translocation ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Rac Gtpase ◽  
Skeletal Myoblasts

GLUT4 vesicles are actively recruited to the muscle cell surface upon insulin stimulation. Key to this process is Rac-dependent reorganization of filamentous actin beneath the plasma membrane, but the underlying molecular mechanisms have yet to be elucidated. Using L6 rat skeletal myoblasts stably expressing myc-tagged GLUT4, we found that Arp2/3, acting downstream of Rac GTPase, is responsible for the cortical actin polymerization evoked by insulin. siRNA-mediated silencing of either Arp3 or p34 subunits of the Arp2/3 complex abrogated actin remodeling and impaired GLUT4 translocation. Insulin also led to dephosphorylation of the actin-severing protein cofilin on Ser-3, mediated by the phosphatase slingshot. Cofilin dephosphorylation was prevented by strategies depolymerizing remodeled actin (latrunculin B or p34 silencing), suggesting that accumulation of polymerized actin drives severing to enact a dynamic actin cycling. Cofilin knockdown via siRNA caused overwhelming actin polymerization that subsequently inhibited GLUT4 translocation. This inhibition was relieved by reexpressing Xenopus wild-type cofilin-GFP but not the S3E-cofilin-GFP mutant that emulates permanent phosphorylation. Transferrin recycling was not affected by depleting Arp2/3 or cofilin. These results suggest that cofilin dephosphorylation is required for GLUT4 translocation. We propose that Arp2/3 and cofilin coordinate a dynamic cycle of actin branching and severing at the cell cortex, essential for insulin-mediated GLUT4 translocation in muscle cells.

Primary Cilia in Locust Spermatocytes: Formation, Fate, and Possible Function

1988 ◽  
Vol 43 (5-6) ◽  
pp. 455-462 ◽  
Author(s):  
Agnes-M. Daub ◽  
Manfred Hauser
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Light Microscopy ◽  
Cell Cycle Regulation ◽  
Primary Cilia ◽  
Cell Cortex ◽  
Extracellular Medium ◽  
Intimate Association ◽  
Cycle Regulation

During locust spermatocyte development, rudimentary cilia originate from all centrioles of the doubled prophasic centrosome, located in the centrosphere and specifically linked to the nuclear envelope. Membranous vesicles at the bases of the centrioles fuse to form an intracellular ampulla that contributes the ciliary membranes. Later in prophase the ampulla’s membrane is integrated into the plasma membrane so that all primary cilia project into the extracellular medium and lose contact with the nucleus. As the centrioles remain ciliated on their way to their polar positions, w e propose a mechanism for this migration which is based on this intimate association between centrosomes and plasma membrane, on membrane fluidity and on a contractile cell cortex. We noted a translocation of the ciliated centrioles below the cell surface at the metaphase/-anaphase transition which may be regarded as “deciliation” by light microscopy. Some possible explanations for the primary cilium’s role in cell cycle regulation are suggested.

An actin barrier to resealing

2001 ◽  
Vol 114 (19) ◽  
pp. 3487-3494 ◽  
Author(s):  
Katsuya Miyake ◽  
Paul L. McNeil ◽  
Kazunori Suzuki ◽  
Rikiya Tsunoda ◽  
Naonori Sugai
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Cell Injury ◽  
Fusion Reaction ◽  
Physical Contact ◽  
Cell Cortex ◽  
Filamentous Actin ◽  
Cortical Array ◽  
Membrane Contacts ◽  
Local Cell

Plasma membrane disruption is a common form of cell injury in many normal biological environments, including many mammalian tissues. Survival depends on the initiation of a rapid resealing response that is mounted only in the presence of physiological levels of extracellular Ca2+. Vesicle-vesicle and vesicle-plasma membrane fusion events occurring in cortical cytoplasm surrounding the defect are thought to be a crucial element of the resealing mechanism. However, in mammalian cells, the vesicles used in this fusion reaction (endosomes/lysosomes) are not present in a ‘pre-docked’ configuration and so must be brought into physical contact with one another and with the plasma membrane. We propose that a requisite prelude to fusion is the disassembly in local cell cortex of the physical barrier constituted by filamentous actin. Consistent with this hypothesis, we found that rat gastric epithelial (RGM1) cell cortical staining with phalloidin was apparently reduced at presumptive disruption sites. Moreover, flow cytofluorometric analysis of wounded RGM1 populations revealed a small, but significant, Ca2+-dependent reduction in whole cell phalloidin staining. The functional significance of this disruption-induced depolymerization response was confirmed in several independent tests. Introduction into RGM1 cells of the filamentous actin-depolymerizing agent, DNase1, enhanced resealing, although cytochalasin treatment, by itself, had no effect. By contrast, when the filamentous actin cytoskeleton was stabilized experimentally, using phalloidin or jasplakinolide, resealing was strongly inhibited. Cells in wounded cultures displayed an enhanced cortical array of filamentous actin, and resealing by such cells was enhanced strongly by both cytochalasin and DNase 1, demonstrating the specific reversibility of a biologically mediated, polymerization-induced inhibition of resealing. We conclude that localized filamentous actin disassembly removes a cortical barrier standing in the way of membrane-membrane contacts leading to resealing-requisite homotypic and exocytotic fusion events.

scholarly journals Genetic dissection of early endosomal recycling highlights a TORC1-independent role for Rag GTPases

2017 ◽  
Vol 216 (10) ◽  
pp. 3275-3290 ◽  
Author(s):  
Chris MacDonald ◽  
Robert C. Piper
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Surface Membrane ◽  
Physiological Role ◽  
Amino Acid Transporters ◽  
Genetic Dissection ◽  
Cellular Processes ◽  
Rag Gtpases ◽  
Endosomal Recycling ◽  
Recycling Pathway

Endocytosed cell surface membrane proteins rely on recycling pathways for their return to the plasma membrane. Although endosome-to-plasma membrane recycling is critical for many cellular processes, much of the required machinery is unknown. We discovered that yeast has a recycling route from endosomes to the cell surface that functions efficiently after inactivation of the sec7-1 allele of Sec7, which controls transit through the Golgi. A genetic screen based on an engineered synthetic reporter that exclusively follows this pathway revealed that recycling was subject to metabolic control through the Rag GTPases Gtr1 and Gtr2, which work downstream of the exchange factor Vam6. Gtr1 and Gtr2 control the recycling pathway independently of TORC1 regulation through the Gtr1 interactor Ltv1. We further show that the early-endosome recycling route and its control though the Vam6>Gtr1/Gtr2>Ltv1 pathway plays a physiological role in regulating the abundance of amino acid transporters at the cell surface.

scholarly journals Malaria circumsporozoite protein binds to heparan sulfate proteoglycans associated with the surface membrane of hepatocytes.

1993 ◽  
Vol 177 (5) ◽  
pp. 1287-1298 ◽  
Author(s):  
U Frevert ◽  
P Sinnis ◽  
C Cerami ◽  
W Shreffler ◽  
B Takacs ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Heparan Sulfate ◽  
Target Cell ◽  
Surface Membrane ◽  
Heparan Sulfate Proteoglycans ◽  
Circumsporozoite Protein ◽  
Cell Specificity ◽  
Region Ii

During feeding by infected mosquitoes, malaria sporozoites are injected into the host's bloodstream and enter hepatocytes within minutes. The remarkable target cell specificity of this parasite may be explained by the presence of receptors for the region II-plus of the circumsporozoite protein (CS) on the basolateral domain of the plasma membrane of hepatocytes. We have now identified these receptors as heparan sulfate proteoglycans (HSPG). The binding of CS to the receptors is abolished by heparitinase treatment, indicating that the recognition of region II-plus is via the glycosaminoglycan chains. We have purified and partially characterized the CS-binding HSPGs from HepG2 cells. They have a molecular weight of 400,000-700,000, are tightly associated with the plasma membrane, and are released from the cell surface by very mild trypsinization, a property which the CS receptors share with the syndecan family of proteoglycans.

Maintenance of the filamentous actin cytoskeleton is necessary for the activation of store-operated Ca2+ channels, but not other types of plasma-membrane Ca2+ channels, in rat hepatocytes

2002 ◽  
Vol 363 (1) ◽  
pp. 117-126 ◽  
Author(s):  
Ying-Jie WANG ◽  
Roland B. GREGORY ◽  
Greg J. BARRITT
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Critical Factor ◽  
Rat Hepatocytes ◽  
Cytochalasin D ◽  
Cation Channels ◽  
Cell Cortex ◽  
Filamentous Actin ◽  
Ca2 Channels ◽  
Intracellular Messenger

The roles of the filamentous actin (F-actin) cytoskeleton and the endoplasmic reticulum (ER) in the mechanism by which store-operated Ca2+ channels (SOCs) and other plasma-membrane Ca2+ channels are activated in rat hepatocytes in primary culture were investigated using cytochalasin D as a probe. Inhibition of thapsigargin-induced Ca2+ inflow by cytochalasin D depended on the concentration and time of treatment, with maximum inhibition observed with 0.1μM cytochalasin D for 3h. Cytochalasin D (0.1μM for 3h) did not inhibit the total amount of Ca2+ released from the ER in response to thapsigargin but did alter the kinetics of Ca2+ release. The effects of cytochalasin D (0.1μM) on vasopressin-induced Ca2+ inflow were similar to those on thapsigargin-induced Ca2+ inflow, except that cytochalasin D did inhibit vasopressin-induced release of Ca2+ from the ER. Cytochalasin D (0.1μM) inhibited vasopressin-induced Mn2+ inflow (predominantly through intracellular messenger-activated non-selective cation channels), but the degree of inhibition was less than that of vasopressin-induced Ca2+ inflow (predominantly through Ca2+-selective SOCs). Maitotoxin- and hypotonic shock-induced Ca2+ inflow were enhanced rather than inhibited by 0.1μM cytochalasin D. Treatment with 0.1μM cytochalasin D substantially reduced the amount of F-actin at the cell cortex, whereas 5μM cytochalasin D increased the total amount of F-actin and caused an irregular distribution of F-actin at the cell cortex. Cytochalasin D (0.1μM) caused no significant change in the overall arrangement of the ER {monitored using 3′,3′-dihexyloxacarbocyanine iodide [DiOC6(3)] in fixed cells} but disrupted the fine structure of the smooth ER and reduced the diffusion of DiOC6(3) in the ER in live hepatocytes after photobleaching. It is concluded that (i) the concentration of cytochalasin D is a critical factor in the use of this agent as a probe to disrupt the cortical F-actin cytoskeleton in rat hepatocytes, (ii) a reduction in the amount of cortical F-actin inhibits SOCs but not intracellular messenger-activated non-selective cation channels, and (iii) inhibition of the activation of SOCs and reduction in the amount of cortical F-actin is associated with disruption of the organization of the ER.

scholarly journals Identification of detergent-resistant plasma membrane microdomains in dictyostelium: enrichment of signal transduction proteins.

1997 ◽  
Vol 8 (5) ◽  
pp. 855-869 ◽  
Author(s):  
Z Xiao ◽  
P N Devreotes
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Cell Surface ◽  
G Protein ◽  
Biochemical Characterization ◽  
Surface Membrane ◽  
Actin Binding ◽  
Membrane Microdomains ◽  
Immunogold Electron Microscopy ◽  
Membrane Structures

Unlike most other cellular proteins, the chemoattractant receptor, cAR1, of Dictyostelium is resistant to extraction by the zwitterionic detergent, CHAPS. We exploited this property to isolate a subcellular fraction highly enriched in cAR1 by flotation of CHAPS lysates of cells in sucrose density gradients. Immunogold electron microscopy studies revealed a homogeneous preparation of membrane bilayer sheets. This preparation, designated CHAPS-insoluble floating fraction (CHIEF), also contained a defined set of 20 other proteins and a single uncharged lipid. Cell surface biotinylation and preembedding immunoelectron microscopy both confirmed the plasma membrane origin of this preparation. The cell surface phosphodiesterase (PDE) and a downstream effector of cAR1, adenylate cyclase (ACA), were specifically localized in these structures, whereas the cell adhesion molecule gp80, most of the major cell surface membrane proteins, cytoskeletal components, the actin-binding integral membrane protein ponticulin, and G-protein alpha- and beta-subunits were absent. Overall, CHIFF represents about 3-5% of cell externally exposed membrane proteins. All of these results indicate that CHIFF is derived from specialized microdomains of the plasma membrane. The method of isolation is analogous to that of caveolae. However, we were unable to detect distinct caveolae-like structures on the cell surface associated with cAR1, which showed a diffuse staining profile. The discovery of CHIFF facilitates the purification of cAR1 and related signaling proteins and the biochemical characterization of receptor-mediated processes such as G-protein activation and desensitization. It also has important implications for the "fluid mosaic" model of the plasma membrane structures.

scholarly journals Function and interactions of the Ysc84/SH3yl1 family of actin- and lipid-binding proteins

2015 ◽  
Vol 43 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Agnieszka N. Urbanek ◽  
Rebekah Chan ◽  
Kathryn R. Ayscough
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Regulatory Networks ◽  
Actin Polymerization ◽  
Binding Proteins ◽  
Morphological Changes ◽  
Lipid Binding ◽  
Actin Binding ◽  
Filamentous Actin ◽  
Membrane Morphology

Understanding how actin filaments are nucleated, polymerized and disassembled in close proximity to cell membranes is an area of growing interest. Protrusion of the plasma membrane is required for cell motility, whereas inward curvature or invagination is required for endocytic events. These morphological changes in membrane are often associated with rearrangements of actin, but how the many actin-binding proteins of eukaryotes function in a co-ordinated way to generate the required responses is still not well understood. Identification and analysis of proteins that function at the interface between the plasma membrane and actin-regulatory networks is central to increasing our knowledge of the mechanisms required to transduce the force of actin polymerization to changes in membrane morphology. The Ysc84/SH3yl1 proteins have not been extensively studied, but work in both yeast and mammalian cells indicate that these proteins function at the hub of networks integrating regulation of filamentous actin (F-actin) with changes in membrane morphology.

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