scholarly journals Direct visualization of Ras proteins in spatially distinct cell surface microdomains

2003 ◽  
Vol 160 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Ian A. Prior ◽  
Cornelia Muncke ◽  
Robert G. Parton ◽  
John F. Hancock
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Lipid Rafts ◽  
Membrane Lipid ◽  
Point Pattern Analysis ◽  
Immunogold Electron Microscopy ◽  
Point Pattern ◽  
Ras Proteins ◽  
Outer Leaflet ◽  
Spatial Point Pattern Analysis

Localization of signaling complexes to specific microdomains coordinates signal transduction at the plasma membrane. Using immunogold electron microscopy of plasma membrane sheets coupled with spatial point pattern analysis, we have visualized morphologically featureless microdomains, including lipid rafts, in situ and at high resolution. We find that an inner-plasma membrane lipid raft marker displays cholesterol-dependent clustering in microdomains with a mean diameter of 44 nm that occupy 35% of the cell surface. Cross-linking an outer-leaflet raft protein results in the redistribution of inner leaflet rafts, but they retain their modular structure. Analysis of Ras microlocalization shows that inactive H-ras is distributed between lipid rafts and a cholesterol-independent microdomain. Conversely, activated H-ras and K-ras reside predominantly in nonoverlapping, cholesterol-independent microdomains. Galectin-1 stabilizes the association of activated H-ras with these nonraft microdomains, whereas K-ras clustering is supported by farnesylation, but not geranylgeranylation. These results illustrate that the inner plasma membrane comprises a complex mosaic of discrete microdomains. Differential spatial localization within this framework can likely account for the distinct signal outputs from the highly homologous Ras proteins.

scholarly journals High-Resolution FRET Microscopy of Cholera Toxin B-Subunit and GPI-anchored Proteins in Cell Plasma Membranes

2000 ◽  
Vol 11 (5) ◽  
pp. 1645-1655 ◽  
Author(s):  
Anne K. Kenworthy ◽  
Nadezda Petranova ◽  
Michael Edidin
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Cholera Toxin ◽  
Lipid Rafts ◽  
Plasma Membranes ◽  
Membrane Lipid ◽  
Cholera Toxin B Subunit ◽  
Toxin B ◽  
Cholera Toxin B ◽  
B Subunit

“Lipid rafts” enriched in glycosphingolipids (GSL), GPI-anchored proteins, and cholesterol have been proposed as functional microdomains in cell membranes. However, evidence supporting their existence has been indirect and controversial. In the past year, two studies used fluorescence resonance energy transfer (FRET) microscopy to probe for the presence of lipid rafts; rafts here would be defined as membrane domains containing clustered GPI-anchored proteins at the cell surface. The results of these studies, each based on a single protein, gave conflicting views of rafts. To address the source of this discrepancy, we have now used FRET to study three different GPI-anchored proteins and a GSL endogenous to several different cell types. FRET was detected between molecules of the GSL GM1 labeled with cholera toxin B-subunit and between antibody-labeled GPI-anchored proteins, showing these raft markers are in submicrometer proximity in the plasma membrane. However, in most cases FRET correlated with the surface density of the lipid raft marker, a result inconsistent with significant clustering in microdomains. We conclude that in the plasma membrane, lipid rafts either exist only as transiently stabilized structures or, if stable, comprise at most a minor fraction of the cell surface.

scholarly journals Transport of a fluorescent phosphatidylcholine analog from the plasma membrane to the Golgi apparatus.

1984 ◽  
Vol 99 (2) ◽  
pp. 742-751 ◽  
Author(s):  
R G Sleight ◽  
R E Pagano
Keyword(s):  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Fluorescent Protein ◽  
Chinese Hamster ◽  
Membrane Lipid ◽  
Lipid Transfer ◽  
Outer Leaflet ◽  
Membrane Lipid Bilayer ◽  
Fluorescent Lipid

We have examined the internalization and degradation of a fluorescent analog of phosphatidylcholine after its insertion into the plasma membrane of cultured Chinese hamster fibroblasts. 1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)-aminocaproyl phosphatidylcholine (C6-NBD-PC) was incorporated into the cell surface by liposome-cell lipid transfer at 2 degrees C. The fluorescent lipid remained localized at the plasma membrane as long as the cells were kept at 2 degrees C; however, when the cells were warmed to 37 degrees C, internalization of some of the fluorescent lipid occurred. Most of the internalized C6-NBD-PC accumulated in the Golgi apparatus although a small amount was found randomly distributed throughout the cytoplasm in punctate fluorescent structures. Internalization of the fluorescent lipid at 37 degrees C was blocked by the presence of inhibitors of endocytosis. Incubation of cells containing C6-NBD-PC at 37 degrees C resulted in a rapid degradation of the fluorescent lipid. This degradation occurred predominantly at the plasma membrane. The degradation of C6-NBD-PC resulted in the release of NBD-fatty acid into the medium. We have compared the internalization of the fluorescent lipid with that of a fluorescent protein bound to the cell surface. Both fluorescent lipid and protein remained at the plasma membrane at 2 degrees C and neither were internalized at 37 degrees C in the presence of inhibitors of endocytosis. However, when incubated at 37 degrees C under conditions that permit endocytosis, the two fluorescent species appeared at different intracellular sites. Our data suggest that there is no transmembrane movement of C6-NBD-PC and that the fluorescent probe reflects the internalization of the outer leaflet of the plasma membrane lipid bilayer. The results are consistent with the Golgi apparatus as being the primary delivery site of phospholipid by bulk membrane movement from the plasma membrane.

scholarly journals Spatial point-pattern analysis as a powerful tool in identifying pattern-process relationships in plant ecology: an updated review

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Mariem Ben-Said
Keyword(s):  
Spatial Patterns ◽  
Pattern Analysis ◽  
Biotic Interactions ◽  
Plant Ecology ◽  
Point Pattern Analysis ◽  
Point Pattern ◽  
Summary Statistics ◽  
Spatial Point Pattern ◽  
Spatial Point ◽  
Spatial Point Pattern Analysis

Abstract Background Ecological processes such as seedling establishment, biotic interactions, and mortality can leave footprints on species spatial structure that can be detectable through spatial point-pattern analysis (SPPA). Being widely used in plant ecology, SPPA is increasingly carried out to describe biotic interactions and interpret pattern-process relationships. However, some aspects are still subjected to a non-negligible debate such as required sample size (in terms of the number of points and plot area), the link between the low number of points and frequently observed random (or independent) patterns, and relating patterns to processes. In this paper, an overview of SPPA is given based on rich and updated literature providing guidance for ecologists (especially beginners) on summary statistics, uni-/bi-/multivariate analysis, unmarked/marked analysis, types of marks, etc. Some ambiguities in SPPA are also discussed. Results SPPA has a long history in plant ecology and is based on a large set of summary statistics aiming to describe species spatial patterns. Several mechanisms known to be responsible for species spatial patterns are actually investigated in different biomes and for different species. Natural processes, plant environmental conditions, and human intervention are interrelated and are key drivers of plant spatial distribution. In spite of being not recommended, small sample sizes are more common in SPPA. In some areas, periodic forest inventories and permanent plots are scarce although they are key tools for spatial data availability and plant dynamic monitoring. Conclusion The spatial position of plants is an interesting source of information that helps to make hypotheses about processes responsible for plant spatial structures. Despite the continuous progress of SPPA, some ambiguities require further clarifications.

1P-0227 Apolipoprotein A-1 interaction with plasma membrane lipid rafts controls cholesterol export from macrophages

2003 ◽  
Vol 4 (2) ◽  
pp. 69 ◽  
Author(s):  
W. Jessup ◽  
K. Gaus ◽  
L. Kritharides ◽  
A. Boettcher ◽  
W. Drobnik ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Rafts ◽  
Membrane Lipid ◽  
Apolipoprotein A ◽  
Plasma Membrane Lipid

scholarly journals Geospatial tools : for the visualization and analysis of local news distribution

2021 ◽  
Author(s):  
Claus Rinner ◽  
Andrew Komaromy ◽  
April Lindgren
Keyword(s):  
Geographic Distribution ◽  
News Media ◽  
Spatial Data ◽  
Visual Analysis ◽  
News Coverage ◽  
Point Pattern Analysis ◽  
Point Pattern ◽  
Local News ◽  
Spatial Point Pattern Analysis ◽  
Geospatial Tools

Geographic Information Systems (GIS) enable the integration, mapping, and analysis of data across numerous domains. It has been estimated that 80 per cent of all data collected by governments and businesses contain geographic references, and the news media are no exception. We will explain how we conceptualize news items as spatial data points and illustrate how GIS can be used to manage and analyze them using a sample of geographic references from local news items published in the Toronto Star newspaper. The analysis makes use of cartographic mapping for visual analysis of local news distribution and geospatial tools for quantitative–statistical analysis of emerging patterns. The objective of this paper is to illustrate how computer-based mapping tools can be used to analyze the geographic distribution of news in order to identify concentrations and gaps in local news coverage within a given area and thus better understand issues and trends in local news reporting. Keywords : geographic distribution, GIS, local news, spatial point pattern analysis

scholarly journals Moderate Static Magnetic Field (6 mT)-Induced Lipid Rafts Rearrangement Increases Silver NPs Uptake in Human Lymphocytes

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1398
Author(s):  
Cristian Vergallo ◽  
Elisa Panzarini ◽  
Bernardetta Anna Tenuzzo ◽  
Stefania Mariano ◽  
Ada Maria Tata ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Human Lymphocytes ◽  
Peripheral Blood Lymphocytes ◽  
Membrane Lipid ◽  
Membrane Perturbation ◽  
Plasma Membrane Lipid ◽  
Silver Nps ◽  
Surface Ligand

One of the most relevant drawbacks in medicine is the ability of drugs and/or imaging agents to reach cells. Nanotechnology opened new horizons in drug delivery, and silver nanoparticles (AgNPs) represent a promising delivery vehicle for their adjustable size and shape, high-density surface ligand attachment, etc. AgNPs cellular uptake involves different endocytosis mechanisms, including lipid raft-mediated endocytosis. Since static magnetic fields (SMFs) exposure induces plasma membrane perturbation, including the rearrangement of lipid rafts, we investigated whether SMF could increase the amount of AgNPs able to pass the peripheral blood lymphocytes (PBLs) plasma membrane. To this purpose, the effect of 6-mT SMF exposure on the redistribution of two main lipid raft components (i.e., disialoganglioside GD3, cholesterol) and on AgNPs uptake efficiency was investigated. Results showed that 6 mT SMF: (i) induces a time-dependent GD3 and cholesterol redistribution in plasma membrane lipid rafts and modulates gene expression of ATP-binding cassette transporter A1 (ABCA1), (ii) increases reactive oxygen species (ROS) production and lipid peroxidation, (iii) does not induce cell death and (iv) induces lipid rafts rearrangement, that, in turn, favors the uptake of AgNPs. Thus, it derives that SMF exposure could be exploited to enhance the internalization of NPs-loaded therapeutic or diagnostic molecules.

scholarly journals Membrane lipid rafts are disturbed in the response of rat skeletal muscle to short-term disuse

2017 ◽  
Vol 312 (5) ◽  
pp. C627-C637 ◽  
Author(s):  
Alexey M. Petrov ◽  
Violetta V. Kravtsova ◽  
Vladimir V. Matchkov ◽  
Alexander N. Vasiliev ◽  
Andrey L. Zefirov ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Motor Nerve ◽  
Membrane Lipid ◽  
Hindlimb Suspension ◽  
Cholera Toxin B Subunit ◽  
Plasma Membrane Lipid ◽  
Intracellular Ca

Marked loss of skeletal muscle mass occurs under various conditions of disuse, but the molecular and cellular mechanisms leading to atrophy are not completely understood. We investigate early molecular events that might play a role in skeletal muscle remodeling during mechanical unloading (disuse). The effects of acute (6–12 h) hindlimb suspension on the soleus muscles from adult rats were examined. The integrity of plasma membrane lipid rafts was tested utilizing cholera toxin B subunit or fluorescent sterols. In addition, resting intracellular Ca2+ level was analyzed. Acute disuse disturbed the plasma membrane lipid-ordered phase throughout the sarcolemma and was more pronounced in junctional membrane regions. Ouabain (1 µM), which specifically inhibits the Na-K-ATPase α2 isozyme in rodent skeletal muscles, produced similar lipid raft changes in control muscles but was ineffective in suspended muscles, which showed an initial loss of α2 Na-K-ATPase activity. Lipid rafts were able to recover with cholesterol supplementation, suggesting that disturbance results from cholesterol loss. Repetitive nerve stimulation also restores lipid rafts, specifically in the junctional sarcolemma region. Disuse locally lowered the resting intracellular Ca2+ concentration only near the neuromuscular junction of muscle fibers. Our results provide evidence to suggest that the ordering of lipid rafts strongly depends on motor nerve input and may involve interactions with the α2 Na-K-ATPase. Lipid raft disturbance, accompanied by intracellular Ca2+ dysregulation, is among the earliest remodeling events induced by skeletal muscle disuse.

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