Iodide penetration into lipid bilayers as a probe of membrane lipid organization

In lymphocytes, the cytoskeletal protein spectrin exhibits two organizational states. Because the plasma membrane lipids of lymphocytes also display two organizational states, it was asked whether there is a relation between the organization of spectrin and of membrane lipids. When mouse thymocytes were stained with merocyanine 540 (MC540), a fluorescent lipophilic probe that binds preferentially to loosely packed, disorganized lipid bilayers, some cells fluoresced brightly and some only dimly or not at all. When the same population was stained for spectrin by indirect immunofluorescence, the spectrin in some cells was uniformly distributed, while in others it was concentrated in a unipolar aggregate. Techniques enriching for mature thymocytes selected for cells displaying low MC540 fluorescence and aggregated spectrin, the same characteristics found in peripheral blood lymphocytes. Flow cytometric sorting of thymocytes based on MC540 phenotype simultaneously sorted them by spectrin phenotype. Finally, treatment with agents that alter the distribution of spectrin caused mature lymphocytes to display high MC540 fluorescence and uniform spectrin. Thus, a relation exists between the organizational states of spectrin and of membrane lipids in lymphocytes: aggregated spectrin is found in cells with tightly organized membrane lipids, uniform spectrin in those with loosely organized lipids. Spectrin may thus be involved in modulating membrane lipid organization in lymphocytes as it is in erythrocytes. Since loosely organized lipids may promote adhesion of blood cells to reticuloendothelial cells, spectrin may thereby be involved in transducing an internally generated adhesion signal to the lymphocyte surface.

Download Full-text

Alterations in plasma membrane lipid organization during lymphocyte differentiation

Journal of Cellular Physiology ◽

10.1002/jcp.1041260308 ◽

1986 ◽

Vol 126 (3) ◽

pp. 379-388 ◽

Cited By ~ 31

Author(s):

Brian J. Del Buono ◽

Patrick L. Williamson ◽

Robert A. Schlegel

Keyword(s):

Plasma Membrane ◽

Membrane Lipid ◽

Lymphocyte Differentiation ◽

Plasma Membrane Lipid ◽

Lipid Organization

Download Full-text

Effect of fatty acid saturation in membrane lipid bilayers on simple diffusion in the presence of ethanol at high concentrations

Journal of Fermentation and Bioengineering ◽

10.1016/0922-338x(96)85141-5 ◽

1996 ◽

Vol 81 (5) ◽

pp. 406-411 ◽

Cited By ~ 29

Author(s):

Haruhiko Mizoguchi ◽

Shodo Hara

Keyword(s):

Fatty Acid ◽

Lipid Bilayers ◽

Membrane Lipid ◽

Simple Diffusion ◽

Fatty Acid Saturation ◽

High Concentrations

Download Full-text

Salicylic acid-mediated plasmodesmal closure via Remorin-dependent lipid organization

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1911892116 ◽

2019 ◽

Vol 116 (42) ◽

pp. 21274-21284 ◽

Cited By ~ 21

Author(s):

Dingquan Huang ◽

Yanbiao Sun ◽

Zhiming Ma ◽

Meiyu Ke ◽

Yong Cui ◽

...

Keyword(s):

Salicylic Acid ◽

Lipid Raft ◽

Plant Pathogens ◽

Regulatory Protein ◽

Cell Communication ◽

Direct Interaction ◽

Membrane Lipid ◽

Dependent Manner ◽

Transmission Electron ◽

Lipid Organization

Plasmodesmata (PD) are plant-specific membrane-lined channels that create cytoplasmic and membrane continuities between adjacent cells, thereby facilitating cell–cell communication and virus movement. Plant cells have evolved diverse mechanisms to regulate PD plasticity in response to numerous environmental stimuli. In particular, during defense against plant pathogens, the defense hormone, salicylic acid (SA), plays a crucial role in the regulation of PD permeability in a callose-dependent manner. Here, we uncover a mechanism by which plants restrict the spreading of virus and PD cargoes using SA signaling by increasing lipid order and closure of PD. We showed that exogenous SA application triggered the compartmentalization of lipid raft nanodomains through a modulation of the lipid raft-regulatory protein, Remorin (REM). Genetic studies, superresolution imaging, and transmission electron microscopy observation together demonstrated that Arabidopsis REM1.2 and REM1.3 are crucial for plasma membrane nanodomain assembly to control PD aperture and functionality. In addition, we also found that a 14-3-3 epsilon protein modulates REM clustering and membrane nanodomain compartmentalization through its direct interaction with REM proteins. This study unveils a molecular mechanism by which the key plant defense hormone, SA, triggers membrane lipid nanodomain reorganization, thereby regulating PD closure to impede virus spreading.

Download Full-text

Membrane Curvature Modeling and Lipid Organization in Supported Lipid Bilayers

Biophysical Journal ◽

10.1016/j.bpj.2009.12.445 ◽

2010 ◽

Vol 98 (3) ◽

pp. 78a-79a

Author(s):

Matthew I. Hoopes ◽

Roland Faller ◽

Marjorie L. Longo

Keyword(s):

Lipid Bilayers ◽

Membrane Curvature ◽

Supported Lipid Bilayers ◽

Lipid Organization

Download Full-text

Interaction of Local Anesthetics with Biomembranes Consisting of Phospholipids and Cholesterol: Mechanistic and Clinical Implications for Anesthetic and Cardiotoxic Effects

Anesthesiology Research and Practice ◽

10.1155/2013/297141 ◽

2013 ◽

Vol 2013 ◽

pp. 1-18 ◽

Cited By ~ 11

Author(s):

Hironori Tsuchiya ◽

Maki Mizogami

Keyword(s):

Lipid Bilayers ◽

Local Anesthetics ◽

Cell Membranes ◽

Membrane Lipids ◽

Transmembrane Proteins ◽

Membrane Lipid ◽

Direct Inhibition ◽

Drug Molecules ◽

Site Of Action ◽

Lipid Barriers

Despite a long history in medical and dental application, the molecular mechanism and precise site of action are still arguable for local anesthetics. Their effects are considered to be induced by acting on functional proteins, on membrane lipids, or on both. Local anesthetics primarily interact with sodium channels embedded in cell membranes to reduce the excitability of nerve cells and cardiomyocytes or produce a malfunction of the cardiovascular system. However, the membrane protein-interacting theory cannot explain all of the pharmacological and toxicological features of local anesthetics. The administered drug molecules must diffuse through the lipid barriers of nerve sheaths and penetrate into or across the lipid bilayers of cell membranes to reach the acting site on transmembrane proteins. Amphiphilic local anesthetics interact hydrophobically and electrostatically with lipid bilayers and modify their physicochemical property, with the direct inhibition of membrane functions, and with the resultant alteration of the membrane lipid environments surrounding transmembrane proteins and the subsequent protein conformational change, leading to the inhibition of channel functions. We review recent studies on the interaction of local anesthetics with biomembranes consisting of phospholipids and cholesterol. Understanding the membrane interactivity of local anesthetics would provide novel insights into their anesthetic and cardiotoxic effects.

Download Full-text

Rabies Virus-Induced Membrane Fusion Pathway

The Journal of Cell Biology ◽

10.1083/jcb.150.3.601 ◽

2000 ◽

Vol 150 (3) ◽

pp. 601-612 ◽

Cited By ~ 76

Author(s):

Yves Gaudin

Keyword(s):

Lipid Bilayers ◽

Rabies Virus ◽

Fusion Process ◽

Fusion Pore ◽

Viral Glycoprotein ◽

Rate Limiting Step ◽

Glycoprotein G ◽

Lipid Organization ◽

Target Membrane ◽

Peptide Insertion

Fusion of rabies virus with membranes is triggered at low pH and is mediated by the viral glycoprotein (G). The rabies virus-induced fusion pathway was studied by investigating the effects of exogenous lipids having various dynamic molecular shapes on the fusion process. Inverted cone-shaped lysophosphatidylcholines (LPCs) blocked fusion at a stage subsequent to fusion peptide insertion into the target membrane. Consistent with the stalk-hypothesis, LPC with shorter alkyl chains inhibited fusion at lower membrane concentrations and this inhibition was compensated by the presence of oleic acid. However, under suboptimal fusion conditions, short chain LPCs, which were translocated in the inner leaflet of the membranes, considerably reduced the lag time preceding membrane merging, resulting in faster kinetics of fusion. This indicated that the rate limiting step for fusion is the formation of a fusion pore in a diaphragm of restricted hemifusion. The previously described cold-stabilized prefusion complex was also characterized. This intermediate is at a well-advanced stage of the fusion process when the hemifusion diaphragm is destabilized, but lipid mixing is still restricted, probably by a ring-like complex of glycoproteins. I provide evidence that this state has a dynamic character and that its lipid organization can reverse back to two lipid bilayers.

Download Full-text

Asymmetric phospholipids impart novel biophysical properties to lipid bilayers allowing environmental adaptation

10.1101/2020.06.03.130450 ◽

2020 ◽

Author(s):

Paul Smith ◽

Dylan M. Owen ◽

Christian D. Lorenz ◽

Maria Makarova

Keyword(s):

Lipid Bilayers ◽

Mammalian Cells ◽

Yeast Species ◽

Membrane Lipid ◽

Head Group ◽

Biophysical Properties ◽

Biophysical Parameters ◽

Unsaturated Lipids ◽

Chain Acyl ◽

Dynamics Simulations

AbstractPhospholipids are a diverse group of biomolecules consisting of a hydrophilic head group and two hydrophobic acyl tails. The nature of the head and length and saturation of the acyl tails are important for defining the biophysical properties of lipid bilayers. It has recently been shown that the membranes of certain yeast species contain high levels of unusual asymmetric phospholipids, consisting of one long and one medium chain acyl moiety – a configuration not common in mammalian cells or other well studied model yeast species. This raises the possibility that structurally asymmetric phospholipids impart novel biophysical properties to the yeast membranes. Here, we use atomistic molecular dynamics simulations (MD) and environmentally-sensitive fluorescent membrane probes to characterize key biophysical parameters of membranes formed from asymmetric lipids for the first time. Interestingly, we show that saturated, but asymmetric phospholipids maintain membrane lipid order across a wider range of temperatures and do not require acyl tail unsaturation or sterols to maintain their properties. This may allow cells to maintain membrane fluidity even in environments which lack the oxygen required for the synthesis of unsaturated lipids and sterols.

Download Full-text