-
Chemistry and Physics of Lipids Sep 2016Sterols are important components of eukaryotic membranes, but rare in bacteria. Some bacteria obtain sterols from their host or environment. In some cases, these sterols... (Review)
Review
Sterols are important components of eukaryotic membranes, but rare in bacteria. Some bacteria obtain sterols from their host or environment. In some cases, these sterols form membrane domains analogous the lipid rafts proposed to exist in eukaryotic membranes. This review describes the properties and roles of sterols in Borrelia and Helicobacter.
Topics: Bacteria; Biological Transport; Cholesterol; Membrane Microdomains; Membrane Proteins
PubMed: 26964703
DOI: 10.1016/j.chemphyslip.2016.03.002 -
Langmuir : the ACS Journal of Surfaces... Nov 2022For the first time, HMG-CoA reductase, the membrane protein responsible for cholesterol synthesis, was incorporated into a lipid membrane consisting of DOPC:Chol:SM at a...
For the first time, HMG-CoA reductase, the membrane protein responsible for cholesterol synthesis, was incorporated into a lipid membrane consisting of DOPC:Chol:SM at a 1:1:1 molar ratio, which mimics the lipid rafts of cell membranes. The membrane containing the protein was generated in the form of either a proteoliposomes or a film obtained by spreading the proteoliposomes at the air-water interface to prepare a protein-rich and stable lipid layer over time. The lipid vesicle parameters were characterized using dynamic light scattering (DLS) and fluorescence microscopy. The incorporation of HMG-CoA reductase was reflected in the increased size of the proteoliposomes compared to that of the empty liposomes of model rafts. Enzyme reconstitution was confirmed by measuring the activity of NADPH, which participates in the catalytic process. The thin lipid raft films formed by spreading liposomes and proteoliposomes at the air-water interface were investigated using the Langmuir technique. The activities of the HMG-CoA reductase films were preserved over time, and the two lipid raft systems, nanoparticles and films, were exposed to solutions of fluvastatin, a HMG-CoA reductase inhibitor commonly used in the treatment of hypercholesterolemia. Both lipid raft systems constructed were useful membrane models for the determination of reductase activity and for monitoring the statin inhibitory effects and may be used for investigating other integral membrane proteins during exposure to inhibitors/activators considered to be potential drugs.
Topics: Hydroxymethylglutaryl-CoA Reductase Inhibitors; Membrane Proteins; Liposomes; Fluvastatin; Membrane Microdomains; Water
PubMed: 36335466
DOI: 10.1021/acs.langmuir.2c02115 -
Biochimica Et Biophysica Acta.... Feb 2022Methods for efficient cyclodextrin-induced lipid exchange have been developed in our lab. These make it possible to almost completely replace the lipids in the outer... (Review)
Review
Methods for efficient cyclodextrin-induced lipid exchange have been developed in our lab. These make it possible to almost completely replace the lipids in the outer leaflet of artificial membranes or the plasma membranes of living cells with exogenous lipids. Lipid replacement/substitution allows detailed studies of how lipid composition and asymmetry influence the structure and function of membrane domains and membrane proteins. In this review, we both summarize progress on cyclodextrin exchange in cells, mainly by the use of methyl-alpha cyclodextrin to exchange phospholipids and sphingolipids, and discuss the issues to consider when carrying out lipid exchange experiments upon cells. Issues that impact interpretation of lipid exchange are also discussed. This includes how overly naïve interpretation of how lipid exchange-induced changes in domain formation can impact protein function.
Topics: Lipid Metabolism; Membrane Lipids; Membrane Microdomains; Membrane Proteins; Mutation, Missense; Phospholipids; alpha-Cyclodextrins
PubMed: 34534531
DOI: 10.1016/j.bbamem.2021.183774 -
International Journal of Molecular... Jul 2023This paper deals with the problems encountered in the study of eukaryotic cell membranes. A discussion on the structure and composition of membranes, lateral... (Review)
Review
This paper deals with the problems encountered in the study of eukaryotic cell membranes. A discussion on the structure and composition of membranes, lateral heterogeneity of membranes, lipid raft formation, and involvement of actin and cytoskeleton networks in the maintenance of membrane structure is included. Modern methods for the study of membranes and their constituent domains are discussed. Various simplified models of biomembranes and lipid rafts are presented. Computer modelling is considered as one of the most important methods. This is stated that from the study of the plasma membrane structure, it is desirable to proceed to the diverse membranes of all organelles of the cell. The qualitative composition and molar content of individual classes of polar lipids, free sterols and proteins in each of these membranes must be considered. A program to create an open access electronic database including results obtained from the membrane modelling of individual cell organelles and the key sites of the membranes, as well as models of individual molecules composing the membranes, has been proposed.
Topics: Eukaryotic Cells; Cholesterol; Cell Membrane; Sterols; Membrane Microdomains; Computer Simulation
PubMed: 37446404
DOI: 10.3390/ijms241311226 -
International Journal of Biological... Nov 2022Phenylketonuria (PKU) is a metabolic disorder connected to an excess of phenylalanine (Phe) in the blood and tissues, with neurological consequences. The disease's...
Phenylketonuria (PKU) is a metabolic disorder connected to an excess of phenylalanine (Phe) in the blood and tissues, with neurological consequences. The disease's molecular bases seem to be related to the accumulation of Phe at the cell membrane surface. Radiological outcomes in the brain demonstrate decreased water diffusivity in white matter, involving axon dysmyelination of not yet understood origin. We used a biophysical approach and model membranes to extend our knowledge of Phe-membrane interaction by clarifying Phe's propensity to affect membrane structure and dynamics based on lipid composition, with emphasis on modulating cholesterol and glycolipid components to mimic raft domains and myelin sheath membranes. Phe showed affinity for the investigated membrane mimics, mainly affecting the Phe-facing membrane leaflet. The surfaces of our neuronal membrane raft mimics were strong anchoring sites for Phe, showing rigidifying effects. From a therapeutic perspective, we further investigated the role of doxycycline, known to disturb Phe packing, unveiling its action as a competitor in Phe interactions with the membrane, suggesting its potential for treatment in the early stages of PKU. Our results suggest how Phe accumulation in extracellular fluids can impede normal growth of myelin sheaths by interfering with membrane slipping and by remodulating free water and myelin-associated water contents.
Topics: Humans; Phenylalanine; Glycolipids; Phenylketonurias; Brain; Water
PubMed: 36099998
DOI: 10.1016/j.ijbiomac.2022.09.062 -
Cytometry. Part a : the Journal of the... Jul 2008The evolutionarily developed microdomain structure of biological membranes has gained more and more attention in the past decade. The caveolin-free "membrane rafts," the... (Review)
Review
The evolutionarily developed microdomain structure of biological membranes has gained more and more attention in the past decade. The caveolin-free "membrane rafts," the caveolin-expressing rafts (caveolae), as well as other membrane microdomains seem to play an essential role in controlling and coordinating cell-surface molecular recognition, internalization/endocytosis of the bound molecules or pathogenic organisms and in regulation of transmembrane signal transduction processes. Therefore, in many research fields (e.g. neurobiology and immunology), there is an ongoing need to understand the nature of these microdomains and to quantitatively characterize their lipid and protein composition under various physiological and pathological conditions. Flow and image cytometry offer many sophisticated and routine tools to study these questions. In this review, we give an overview of the past efforts to detect and characterize these membrane microdomains by the use of classical cytometric technologies, and finally we will discuss the results and perspectives of a new line of raft cytometry, the "high throughput screening assays of membrane microdomains," based on "lipidomic" and "proteomic" approaches.
Topics: Animals; Caveolae; Cell Membrane; Detergents; Flow Cytometry; Fluorescence Resonance Energy Transfer; Humans; Image Cytometry; Lipids; Membrane Lipids; Membrane Microdomains; Protein Structure, Tertiary; Proteomics
PubMed: 18473380
DOI: 10.1002/cyto.a.20572 -
Journal of Neurochemistry Nov 2007Glycosphingolipids (GSLs) and glycoproteins are ubiquitous components of mammalian cell membranes. GSLs are especially enriched in the nervous system and significantly... (Review)
Review
Glycosphingolipids (GSLs) and glycoproteins are ubiquitous components of mammalian cell membranes. GSLs are especially enriched in the nervous system and significantly contribute to membrane organization and a variety of cellular functions. Current body of evidence suggests that GSLs along with cholesterol are enriched in discrete membrane domains that associate specific proteins. Current notion of membrane organization is that, the GSL-cholesterol-enriched membrane domains known as 'lipid rafts' float in the phospholipid-enriched bulk of the membrane and regulate the cell signaling by facilitating the lipid-protein/protein-protein interactions. The sizeable literature accumulated during the last decade has provided some insight into the organization and function of rafts; however, they still remain perplexing. In recent years, an appealing concept of lipid raft heterogeneity has emerged. GSL- and glycosylphosphatidylinositol-anchored proteins are considered as the crucial pivots of heterogeneous rafts. This review deals with the enigma of organizational and functional heterogeneity of lipid rafts and discusses the dynamic coalescence of heterogeneous rafts during signaling that can explain the specificity of raft-regulated cellular signaling events.
Topics: Animals; Cell Membrane; Membrane Lipids; Membrane Microdomains; Models, Biological
PubMed: 17986148
DOI: 10.1111/j.1471-4159.2007.04720.x -
FEBS Letters Jun 2020In mammals, polysialic acid (polySia) attached to a small number of transmembrane protein carriers occurs on the surface of plasma membranes of neural, cancer, immune,...
In mammals, polysialic acid (polySia) attached to a small number of transmembrane protein carriers occurs on the surface of plasma membranes of neural, cancer, immune, and placental trophoblast cells. Here, our goal was to demonstrate the presence of polySia on exosomes and its effect on membrane properties. We isolated exosomes and found that polysialylated exosomes in fetal bovine serum originate mostly from placental trophoblasts, while in calf bovine serum, they originate from immune cells. Enzymatic removal of polySia chains from the exosomal surface makes the membrane surface potential more positive, transmembrane potential more negative, and reduces the activation energy for membrane anisotropy changes. We demonstrate for the first time that exosomes could interact through polySia-raft interactions. We suggest that polysialylation of exosomal membrane can have a thermo-protecting effect and can modulate exosome-plasma membrane interactions.
Topics: Anisotropy; Cell Line, Tumor; Exosomes; Fluorescence Resonance Energy Transfer; Humans; Membrane Microdomains; Membrane Potentials; Sialic Acids; Temperature
PubMed: 32279314
DOI: 10.1002/1873-3468.13785 -
ACS Applied Materials & Interfaces Dec 2022Lipid rafts are highly ordered regions of the plasma membrane enriched in signaling proteins and lipids. Their biological potential is realized in exosomes, a subclass...
Lipid rafts are highly ordered regions of the plasma membrane enriched in signaling proteins and lipids. Their biological potential is realized in exosomes, a subclass of extracellular vesicles (EVs) that originate from the lipid raft domains. Previous studies have shown that EVs derived from human placental mesenchymal stromal cells (PMSCs) possess strong neuroprotective and angiogenic properties. However, clinical translation of EVs is challenged by very low, impure, and heterogeneous yields. Therefore, in this study, lipid rafts are validated as a functional biomaterial that can recapitulate the exosomal membrane and then be synthesized into biomimetic nanovesicles. Lipidomic and proteomic analyses show that lipid raft isolates retain functional lipids and proteins comparable to PMSC-EV membranes. PMSC-derived lipid raft nanovesicles (LRNVs) are then synthesized at high yields using a facile, extrusion-based methodology. Evaluation of biological properties reveals that LRNVs can promote neurogenesis and angiogenesis through modulation of lipid raft-dependent signaling pathways. A proof-of-concept methodology further shows that LRNVs could be loaded with proteins or other bioactive cargo for greater disease-specific functionalities, thus presenting a novel type of biomimetic nanovesicles that can be leveraged as targeted therapeutics for regenerative medicine.
Topics: Female; Humans; Pregnancy; Proteomics; Placenta; Membrane Microdomains; Cell Membrane; Proteins; Lipids
PubMed: 36448709
DOI: 10.1021/acsami.2c13868 -
Frontiers in Cell and Developmental... 2016Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental... (Review)
Review
Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.
PubMed: 28119913
DOI: 10.3389/fcell.2016.00154