Transbilayer effects of ethanol on fluidity of brain membrane leaflets

Schroeder, Friedhelm; Morrison, William J.; Gorka, Christine; Wood, W. Gibson

doi:10.1016/0005-2736(88)90460-9

Cited by 85 publications

(55 citation statements)

References 39 publications

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“…Thus, based on the similarities of charged polar head groups, it may be postulated that DPH-TMA (a zwitterionic polar head group) and DPH-Pro (an anionic polar head group) are translocated by plasma membrane flippases and/or scramblases to distribute similarly to their zwitterionic and anionic phospholipid counterparts. Finally, in support of the finding that leaflet-selective DPH-TMA and DPH-Pro show a more rigid cytofacial leaflet and a more fluid exofacial leaflet (39), studies with a nonflipping ESR probe inserted into right side-out and inside-out oriented plasma membranes confirm the more rigid cytofacial leaflet and more fluid exofacial leaflet (41).…”

Section: Structure Of Hepatocyte Plasma Membrane Lipid Raft and Nonrasupporting

confidence: 58%

“…The leaflet selectivity of each of the probes (i.e., transbilayer distribution) within isolated plasma membrane fragments was verified by leaflet-selective quenching studies performed as reviewed in Refs. 35, 36 and detailed in the following individually cited papers showing that the inner and outer leaflets of isolated plasma membrane vesicles/fragments differ in fluidity: i) leaflet-selective quenching of DPH (nonselectively partitions into both leaflets) (37)(38)(39); ii) studies with right side-out and inside-out plasma membranes (38); iii) studies with the leaflet-selective DPH derivatives DPH-TMA and DPH-Pro (39), which are anchored closer to the membrane surface than DPH (40); iv) spin-label probes and purified right side-out and inside-out oriented plasma membranes (41); and v) model membrane studies of fluidity of outer versus inner leaflet phospholipid mixtures (42). Based on the these previous findings, fluorescence polarization of the leaflet-selective DPH derivatives DPH-TMA and DPH-Pro were used to measure the transbilayer fluidity gradient in hepatocyte plasma membrane lipid rafts and nonrafts exactly as described earlier (13,39).…”

Section: Structure Of Hepatocyte Plasma Membrane Lipid Raft and Nonramentioning

confidence: 99%

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SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes

Atshaves¹,

McIntosh²,

Payne³

et al. 2007

Journal of Lipid Research

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Although reverse cholesterol transport from peripheral cell types is mediated through plasma membrane microdomains termed lipid rafts, almost nothing is known regarding the existence, protein/lipid composition, or structure of these putative domains in liver hepatocytes, cells responsible for the net removal of cholesterol from the body. Lipid rafts purified from hepatocyte plasma membranes by a nondetergent affinity chromatography method were: i) present at 33 6 3% of total plasma membrane protein; ii) enriched in key proteins of the reverse cholesterol pathway [scavenger receptor class B type I (SR-B1), ABCA1, P-glycoprotein (P-gp), sterol carrier protein-2 (SCP-2)]; iii) devoid of caveolin-1; iv) enriched in cholesterol, sphingomyelin, GM1, and phospholipids low in polyunsaturated fatty acid and double bond index; and v) exhibited an intermediate liquid-ordered lipid phase with significant transbilayer fluidity gradient. Ablation of the gene encoding SCP-2 significantly altered lipid rafts to: i) increase the proportion of lipid rafts present, thereby increasing raft total content of ABCA1, P-gp, and SR-B1; ii) increase total phospholipids while decreasing GM1 in lipid rafts; iii) decrease the fluidity of lipid rafts, consistent with the increased intermediate liquid-ordered phase; and iv) abolish the lipid raft transbilayer fluidity gradient. Thus, despite the absence of caveolin-1 in liver hepatocytes, lipid rafts represented nearly one-third of the mouse hepatocyte plasma membrane proteins and displayed unique protein, lipid, and biophysical properties that were differentially regulated by SCP-2 expression. Although all cells synthesize cholesterol, only liver and steroidogenic tissues effect net cholesterol removal. Reverse cholesterol transport (RCT) from peripheral tissues to liver for oxidation and excretion is the major physiological pathway for the net cholesterol elimination from the body. Although increasing evidence indicates that plasma membrane microdomains, termed lipid rafts/caveolae, compartmentalize cell surface proteins that mediate HDLcholesterol uptake/efflux in peripheral cells, the existence and/or significance of such domains in hepatocyte plasma membranes is not completely clear, especially in view of the nearly negligible levels of caveolin-1 in liver. However, an overall scheme is beginning to evolve based largely on findings with peripheral cells (reviewed in Ref. 1).First, peripheral cells (fibroblasts, muscle, and endothelial cells) are rich in both lipid rafts and caveolae (a subset of lipid rafts rich in several components of the RCT pathway) but are relatively poor in intracellular cholesterol binding proteins such as sterol carrier protein-2 (SCP-2) that facilitate cholesterol retention rather than efflux (reviewed in Refs. 1, 2). Cholesterol effluxes from peripheral cells to HDL by a process facilitated by: i) the HDL receptor scavenger receptor class B type I (SR-B1) (3); ii) ABCA1, a protein that mediates cholesterol and phosphatidylcholine desorption from the pla...

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Section: Structure Of Hepatocyte Plasma Membrane Lipid Raft and Nonrasupporting

confidence: 58%

Section: Structure Of Hepatocyte Plasma Membrane Lipid Raft and Nonramentioning

confidence: 99%

SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes

Atshaves¹,

McIntosh²,

Payne³

et al. 2007

Journal of Lipid Research

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“…The finding of rapid transbilayer sterol movement suggested that the asymmetric transbilayer distribution in the plasma membrane was not due to restricted movement of cholesterol from one leaflet to the other, but was instead a property of the lipid bilayer itself. DHE transbilayer distribution has broad applicability in studies of the action of anesthetics, cholesterol lowering drugs (statins), alcohol (chronic and acute), lupus erythematosus, aging, apoE, and sterol carrier proteins all of which can alter plasma membrane or synaptosomal plasma membrane transbilayer sterol distribution and/or transbilayer fluidity (26,135,136,145,149,150,154,(161)(162)(163)(164)(165)(166)(167)(168)(169)(170)(171)(172).Second, the DHE lateral distribution in both model and biological membranes was not uniform, but instead reflected sterol-rich and poor domains (rev. in (54,55).…”

mentioning

confidence: 99%

Fluorescence Techniques Using Dehydroergosterol to Study Cholesterol Trafficking

McIntosh

Atshaves

Huang

et al. 2008

Lipids

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Cholesterol itself has very few structural/chemical features suitable for real-time imaging in living cells. Thus, the advent of dehydroergosterol [ergosta-5,7,9(11),22-tetraen-3β-ol, DHE] the fluorescent sterol most structurally and functionally similar to cholesterol to date, has proven to be a major asset for real-time probing/elucidating the sterol environment and intracellular sterol trafficking in living organisms. DHE is a naturally-occurring, fluorescent sterol analog that faithfully mimics many of the properties of cholesterol. Because these properties are very sensitive to sterol structure and degradation, such studies require the use of extremely pure (>98%) quantities of fluorescent sterol. DHE is readily bound by cholesterol-binding proteins, is incorporated into lipoproteins (from the diet of animals or by exchange in vitro), and for real-time imaging studies is easily incorporated into cultured cells where it co-distributes with endogenous sterol. Incorporation from an ethanolic stock solution to cell culture media is effective, but this process forms an aqueous dispersion of dehydroergosterol crystals which can result in endocytic cellular uptake and distribution into lysosomes which is problematic in imaging DHE at the plasma membrane of living cells. In contrast, monomeric DHE can be incorporated from unilamellar vesicles by exchange/fusion with the plasma membrane or from DHE-methyl-β-cyclodextrin (DHE-MβCD) complexes by exchange with the plasma membrane. Both of the latter techniques can deliver large quantities of monomeric dehydroergosterol with significant distribution into the plasma membrane. The properties and behavior of DHE in protein-binding, lipoproteins, model membranes, biological membranes, lipid rafts/caveolae, and real-time imaging in living cells indicate that this naturally-occurring fluorescent sterol is a useful mimic for probing the properties of cholesterol in these systems. Keywordsdehydroergosterol; cholesterol; ergosterol; fluorescent sterols; microscopy Historical PerspectiveIn order to resolve the dynamics and factors governing cholesterol trafficking within cells, it is important to recognize that the cholesterol molecule has very few polar constituents (Fig. 1A). Consequently, cholesterol is poorly soluble in aqueous environments such as cytosol as evidenced by critical micellar concentrations of cholesterol and other sterols being very low, *To whom correspondence should be addressed: Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 862-1433, FAX: (979) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript near 20-30 nM (1-5). The physiological impact of cholesterol's low aqueous solubility is that spontaneous cholesterol desorption from the cytofacial leaflet of the plasma membrane or lysosomal membrane into the cytosol for transfer to intracellular sites for esterification, oxidation, or secretion is extremely slow (t 1/2 3 hours-days) (6-9). Therefore, it is important to resolve factors...

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“…There may also be direct effects of the contaminants on the sample, especially in soft, biological experiments. For example, it is well known that the presence of alcohols (from the cleaning procedure) can fluidify gel-phase lipid bilayers [71][72][73] , rendering sub-nanometer level resolution impossible. If high-resolution is not possible, care should be first taken in the cleaning process, focusing especially on any equipment that comes into contact with the imaging solution.…”

Section: Discussionmentioning

confidence: 99%

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Miller

Trewby

Payam

et al. 2016

JoVE

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Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown that when operated in amplitude-modulation (tapping) mode, atomic or molecular-level resolution images can be achieved over a wide range of soft and hard samples in liquid. In these situations, small oscillation amplitudes (SAM-AFM) enhance the resolution by exploiting the solvated liquid at the surface of the sample. Although the technique has been successfully applied across fields as diverse as materials science, biology and biophysics and surface chemistry, obtaining high-resolution images in liquid can still remain challenging for novice users. This is partly due to the large number of variables to control and optimize such as the choice of cantilever, the sample preparation, and the correct manipulation of the imaging parameters. Here, we present a protocol for achieving high-resolution images of hard and soft samples in fluid using SAM-AFM on a commercial instrument. Our goal is to provide a step-by-step practical guide to achieving high-resolution images, including the cleaning and preparation of the apparatus and the sample, the choice of cantilever and optimization of the imaging parameters. For each step, we explain the scientific rationale behind our choices to facilitate the adaptation of the methodology to every user's specific system.

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Transbilayer effects of ethanol on fluidity of brain membrane leaflets

Cited by 85 publications

References 39 publications

SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes

SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes

Fluorescence Techniques Using Dehydroergosterol to Study Cholesterol Trafficking

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

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