In vitro modulation of rat adipocyte ghost membrane fluidity by cholesterol oxysterols

1995 ◽  
Vol 51 (7) ◽  
pp. 731-737 ◽  
Author(s):  
W. F. Lau ◽  
N. P. Das
Keyword(s):  
Membrane Fluidity

scholarly journals TheEscherichia coliβ-Barrel Assembly Machinery Is Sensitized to Perturbations under High Membrane Fluidity

2018 ◽  
Vol 201 (1) ◽  
Author(s):  
Kelly M. Storek ◽  
Rajesh Vij ◽  
Dawei Sun ◽  
Peter A. Smith ◽  
James T. Koerber ◽  
...  
Keyword(s):  
Amino Acid ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Membrane Fluidity ◽  
Amino Acid Substitutions ◽  
Inhibitory Antibody ◽  
Critical Determinant ◽  
Gram Negative ◽  
Growth Environment

ABSTRACTIntegral β-barrel membrane proteins are folded and inserted into the Gram-negative bacterial outer membrane by the β-barrel assembly machine (BAM). This essential complex, composed of a β-barrel protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE, resides in the outer membrane, a unique asymmetrical lipid bilayer that is difficult to recapitulatein vitro. Thus, the probing of BAM function in living cells is critical to fully understand the mechanism of β-barrel folding. We recently identified an anti-BamA monoclonal antibody, MAB1, that is a specific and potent inhibitor of BamA function. Here, we show that the inhibitory effect of MAB1 is enhanced when BAM function is perturbed by either lowering the level of BamA or removing the nonessential BAM lipoproteins, BamB, BamC, or BamE. The disruption of BAM reduces BamA activity, increases outer membrane (OM) fluidity, and activates the σEstress response, suggesting the OM environment and BAM function are interconnected. Consistent with this idea, an increase in the membrane fluidity through changes in the growth environment or alterations to the lipopolysaccharide in the outer membrane is sufficient to provide resistance to MAB1 and enable the BAM to tolerate these perturbations. Amino acid substitutions in BamA at positions in the outer membrane spanning region or the periplasmic space remote from the extracellular MAB1 binding site also provide resistance to the inhibitory antibody. Our data highlight that the outer membrane environment is a critical determinant in the efficient and productive folding of β-barrel membrane proteins by BamA.IMPORTANCEBamA is an essential component of the β-barrel assembly machine (BAM) in the outer membranes of Gram-negative bacteria. We have used a recently described inhibitory anti-BamA antibody, MAB1, to identify the molecular requirements for BAM function. Resistance to this antibody can be achieved through changes to the outer membrane or by amino acid substitutions in BamA that allosterically affect the response to MAB1. Sensitivity to MAB1 is achieved by perturbing BAM function. By using MAB1 activity and functional assays as proxies for BAM function, we link outer membrane fluidity to BamA activity, demonstrating that an increase in membrane fluidity sensitizes the cells to BAM perturbations. Thus, the search for potential inhibitors of BamA function must consider the membrane environment in which β-barrel folding occurs.

Action of metformin on erythrocyte membrane fluidity in vitro and in vivo

1997 ◽  
Vol 337 (1) ◽  
pp. 103-110 ◽  
Author(s):  
Sylvaine Muller ◽  
Sylvie Denet ◽  
Harilaos Candiloros ◽  
Roger Barrois ◽  
Nicolas Wiernsperger ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Erythrocyte Membrane ◽  
Erythrocyte Membrane Fluidity

Effects of membrane lipid and fluidity modifications on HIV-1 infectibility of primate lymphocytes in vitro

1990 ◽  
Vol 10 (3) ◽  
pp. 263-270 ◽  
Author(s):  
J. Pascal Zimmer ◽  
Hans A. Lehr ◽  
Christoph Hübner ◽  
Stephan G. Lindner ◽  
Ralf Ramsperger ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Fluidity ◽  
Lipid Composition ◽  
Membrane Lipid ◽  
Serum Factors ◽  
Membrane Lipid Composition ◽  
Plasma Membrane Lipid ◽  
Hiv 1

Although most non-human primates, except the chimpanzee and the gibbon in vivo are not infectible by HIV-1, lymphocytes of several of these species can be infected by HIV-1 in vitro.In order to investigate whether the in vitro infectibility of primate lymphocytes might be attributed to plasma membrane adaptation processes or to serum factors, we compared HIV-1 infectibility of cultivated peripheral blood lymphocytes of macaques and of baboons on day one and on day ten of cultivation. These data were correlated to plasma membrane lipid composition and membrane fluidity.We found a correlation between increased HIV-1 in vitro infectibility and changes in plasma membrane lipid composition resulting in decreased membrane fluidity of cultured primate lymphocytes.

Lindane-induced modifications to membrane lipid structure: Effect on membrane fluidity after subchronic treament

1992 ◽  
Vol 12 (4) ◽  
pp. 303-311 ◽  
Author(s):  
M. T. Gutierrez-Ocaña ◽  
S. Senar ◽  
M. A. Perez-Albarsanz ◽  
M. N. Recio
Keyword(s):  
Membrane Fluidity ◽  
Phospholipid Composition ◽  
Membrane Lipid ◽  
Ventral Prostate ◽  
Lipid Structure ◽  
Rat Ventral Prostate ◽  
Polarization Technique ◽  
Lipid Pattern ◽  
Altered Lipid

Chronic lindane intoxication by injecting subcutaneously the toxicant, resulted in an altered lipid pattern in rat ventral prostate membranes. An increase of membrane fluidity was also observed using a fluorescence polarization technique. When in vitro experiments were carried out with both treated and untreated rats, an interesting lack of parallelism was found, which could indicate the development of a resistance to membrane disordering by lindane. The observed changes in cholesterol and phospholipid composition are also consistent with the hypothesis that lindane perturbs the lipid matrix of membranes, possibly inducing complex compensatory changes in the membrane lipid composition.

scholarly journals Flotillin mediated membrane fluidity controls peptidoglycan synthesis and MreB movement

2019 ◽  
Author(s):  
Aleksandra Zielińska ◽  
Abigail Savietto ◽  
Anabela de Sousa Borges ◽  
Denis Martinez ◽  
Melanie Berbon ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Protein Interactions ◽  
Protein Complexes ◽  
Direct Control ◽  
Protein Protein Interactions ◽  
Cellular Compartment ◽  
Peptidoglycan Synthesis ◽  
Synthetic Proteins ◽  
Formation Of Complexes

AbstractThe bacterial plasma membrane is an important cellular compartment. In recent years it has become obvious that protein complexes and lipids are not uniformly distributed within membranes. Current hypotheses suggest that flotillin proteins are required for the formation of complexes of membrane proteins including cell-wall synthetic proteins. We show here that bacterial flotillins are important factors for membrane fluidity homeostasis. Loss of flotillins leads to a decrease in membrane fluidity that in turn leads to alterations in MreB dynamics and, as a consequence, in peptidoglycan synthesis. These alterations are reverted when membrane fluidity is restored by a chemical fluidizer. In vitro, the addition of a flotillin increases membrane fluidity of liposomes. Our data support a model in which flotillins are required for direct control of membrane fluidity rather than for the formation of protein complexes via direct protein-protein interactions.

scholarly journals Regulation of lipid saturation without sensing membrane fluidity

2019 ◽  
Author(s):  
Stephanie Ballweg ◽  
Erdinc Sezgin ◽  
Dorith Wunnicke ◽  
Inga Hänelt ◽  
Robert Ernst
Keyword(s):  
Membrane Fluidity ◽  
Molecular Mechanisms ◽  
Transmembrane Helix ◽  
Membrane Properties ◽  
Spectroscopic Techniques ◽  
Measured Variable ◽  
Homeoviscous Adaptation ◽  
Acyl Chains ◽  
Single Sensor

Abstract/SummaryCells maintain membrane fluidity by regulating lipid saturation, but the molecular mechanisms of this homeoviscous adaptation remain poorly understood. Here, we have reconstituted the core machinery for sensing and regulating lipid saturation in baker’s yeast to directly characterize its response to defined membrane environments. Using spectroscopic techniques and in vitro ubiquitylation, we uncover a unique sensitivity of the transcriptional regulator Mga2 to the abundance, position, and configuration of double bonds in lipid acyl chains and provide unprecedented insight into the molecular rules of membrane adaptivity. Our data challenge the prevailing hypothesis that membrane viscosity serves as the measured variable for regulating lipid saturation. Rather, we show that the signaling output of Mga2 correlates with the size of a single sensor residue in the transmembrane helix, which senses the lateral pressure and/or compressibility profile in a defined region of the membrane. Our findings suggest that membrane property sensors have evolved remarkable sensitivities to highly specific aspects of membrane structure and dynamics, thus paving the way toward the development of genetically encoded reporters for such membrane properties in the future.

scholarly journals Bicarbonate-Stimulated Membrane Reorganization in Stallion Spermatozoa

2021 ◽  
Vol 9 ◽  
Author(s):  
Paula Piccolo Maitan ◽  
Elizabeth G. Bromfield ◽  
Romy Hoogendijk ◽  
Miguel Ricardo Leung ◽  
Tzviya Zeev-Ben-Mordehai ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Fluidity ◽  
Electron Tomography ◽  
Mammalian Species ◽  
Phospholipid Composition ◽  
Defined Medium ◽  
Vital Role ◽  
Membrane Reorganization ◽  
Viable Sperm

Classical in vitro fertilization (IVF) is still poorly successful in horses. This lack of success is thought to be due primarily to inadequate capacitation of stallion spermatozoa under in vitro conditions. In species in which IVF is successful, bicarbonate, calcium, and albumin are considered the key components that enable a gradual reorganization of the sperm plasma membrane that allows the spermatozoa to undergo an acrosome reaction and fertilize the oocyte. The aim of this work was to comprehensively examine contributors to stallion sperm capacitation by investigating bicarbonate-induced membrane remodelling steps, and elucidating the contribution of cAMP signalling to these events. In the presence of capacitating media containing bicarbonate, a significant increase in plasma membrane fluidity was readily detected using merocyanine 540 staining in the majority of viable spermatozoa within 15 min of bicarbonate exposure. Specific inhibition of soluble adenylyl cyclase (sAC) in the presence of bicarbonate by LRE1 significantly reduced the number of viable sperm with high membrane fluidity. This suggests a vital role for sAC-mediated cAMP production in the regulation of membrane fluidity. Cryo-electron tomography of viable cells with high membrane fluidity revealed a range of membrane remodelling intermediates, including destabilized membranes and zones with close apposition of the plasma membrane and the outer acrosomal membrane. However, lipidomic analysis of equivalent viable spermatozoa with high membrane fluidity demonstrated that this phenomenon was neither accompanied by a gross change in the phospholipid composition of stallion sperm membranes nor detectable sterol efflux (p > 0.05). After an early increase in membrane fluidity, a significant and cAMP-dependent increase in viable sperm with phosphatidylserine (PS), but not phosphatidylethanolamine (PE) exposure was noted. While the events observed partly resemble findings from the in vitro capacitation of sperm from other mammalian species, the lack of cholesterol removal appears to be an equine-specific phenomenon. This research will assist in the development of a defined medium for the capacitation of stallion sperm and will facilitate progress toward a functional IVF protocol for horse gametes.

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