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Journal of Lipid Research Feb 2020A fundamental feature of the eukaryotic cell membrane is the asymmetric arrangement of lipids in its two leaflets. A cell invests significant energy to maintain this...
A fundamental feature of the eukaryotic cell membrane is the asymmetric arrangement of lipids in its two leaflets. A cell invests significant energy to maintain this asymmetry and uses it to regulate important biological processes, such as apoptosis and vesiculation. The dynamic coupling of the inner or cytoplasmic and outer or exofacial leaflets is a challenging open question in membrane biology. Here, we combined fluorescence lifetime imaging microscopy (FLIM) with imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS) to differentiate the dynamics and organization of the two leaflets of live mammalian cells. We characterized the biophysical properties of fluorescent analogs of phosphatidylcholine, sphingomyelin, and phosphatidylserine in the plasma membrane of two mammalian cell lines (CHO-K1 and RBL-2H3). Because of their specific transverse membrane distribution, these probes allowed leaflet-specific investigation of the plasma membrane. We compared the results of the two methods having different temporal and spatial resolution. Fluorescence lifetimes of fluorescent lipid analogs were in ranges characteristic for the liquid ordered phase in the outer leaflet and for the liquid disordered phase in the inner leaflet. The observation of a more fluid inner leaflet was supported by free diffusion in the inner leaflet, with high average diffusion coefficients. The liquid ordered phase in the outer leaflet was accompanied by slower diffusion and diffusion with intermittent transient trapping. Our results show that the combination of FLIM and ITIR-FCS with specific fluorescent lipid analogs is a powerful tool for investigating lateral and transbilayer characteristics of plasma membrane in live cell lines.
Topics: Animals; Cell Line; Cell Membrane; Lipids; Microscopy, Fluorescence; Molecular Structure; Spectrometry, Fluorescence; Unilamellar Liposomes
PubMed: 31857388
DOI: 10.1194/jlr.D119000364 -
Biochimica Et Biophysica Acta Apr 2009Epithelial cells form a barrier against the environment, but are also required for the regulated exchange of molecules between an organism and its surroundings.... (Review)
Review
Epithelial cells form a barrier against the environment, but are also required for the regulated exchange of molecules between an organism and its surroundings. Epithelial cells are characterised by a remarkable polarization of their plasma membrane, evidenced by the appearance of structurally, compositionally, and functionally distinct surface domains. Here we consider the (in)dependence of epithelial cell polarisation and the function of smaller plasma membrane domains (e.g. adherens junctions, gap junctions, tight junctions, apical lipid rafts, caveolae, and clathrin-coated pits) in the development and maintenance of cell surface polarity. Recent evidence of cross-talk and/or overlap between the different cell-cell junction components and alternate functions of junction components, including gene expression regulation, are discussed in the context of cell surface polarity.
Topics: Adherens Junctions; Animals; Caveolae; Cell Adhesion; Cell Membrane; Cell Polarity; Coated Pits, Cell-Membrane; Desmosomes; Epithelial Cells; Gap Junctions; Humans; Lipid Bilayers; Membrane Microdomains; Signal Transduction; Tight Junctions
PubMed: 18706883
DOI: 10.1016/j.bbamem.2008.07.015 -
Nature Chemical Biology Jun 2023Plasma membrane heterogeneity has been tied to a litany of cellular functions and is often explained by analogy to membrane phase separation; however, models based on...
Plasma membrane heterogeneity has been tied to a litany of cellular functions and is often explained by analogy to membrane phase separation; however, models based on phase separation alone fall short of describing the rich organization available within cell membranes. Here we present comprehensive experimental evidence motivating an updated model of plasma membrane heterogeneity in which membrane domains assemble in response to protein scaffolds. Quantitative super-resolution nanoscopy measurements in live B lymphocytes detect membrane domains that emerge upon clustering B cell receptors (BCRs). These domains enrich and retain membrane proteins based on their preference for the liquid-ordered phase. Unlike phase-separated membranes that consist of binary phases with defined compositions, membrane composition at BCR clusters is modulated through the protein constituents in clusters and the composition of the membrane overall. This tunable domain structure is detected through the variable sorting of membrane probes and impacts the magnitude of BCR activation.
Topics: Cell Membrane; Membrane Proteins; Membrane Microdomains
PubMed: 36997644
DOI: 10.1038/s41589-023-01268-8 -
Annual Review of Biochemistry 2011Eukaryotic organelles can interact with each other through stable junctions where the two membranes are kept in close apposition. The junction that connects the... (Review)
Review
Eukaryotic organelles can interact with each other through stable junctions where the two membranes are kept in close apposition. The junction that connects the endoplasmic reticulum to the plasma membrane (ER-PM junction) is unique in providing a direct communication link between the ER and the PM. In a recently discovered signaling process, STIM (stromal-interacting molecule) proteins sense a drop in ER Ca(2+) levels and directly activate Orai PM Ca(2+) channels across the junction space. In an inverse process, a voltage-gated PM Ca(2+) channel can directly open ER ryanodine-receptor Ca(2+) channels in striated-muscle cells. Although ER-PM junctions were first described 50 years ago, their broad importance in Ca(2+) signaling, as well as in the regulation of cholesterol and phosphatidylinositol lipid transfer, has only recently been realized. Here, we discuss research from different fields to provide a broad perspective on the structures and unique roles of ER-PM junctions in controlling signaling and metabolic processes.
Topics: Animals; Cell Communication; Cell Membrane; Endoplasmic Reticulum; Humans; Intracellular Membranes; Membrane Proteins; Protein Isoforms; Signal Transduction
PubMed: 21548779
DOI: 10.1146/annurev-biochem-061609-165311 -
The Journal of General Physiology Aug 2019The plasma membrane separates a cell from its external environment. All materials and signals that enter or leave the cell must cross this hydrophobic barrier.... (Review)
Review
The plasma membrane separates a cell from its external environment. All materials and signals that enter or leave the cell must cross this hydrophobic barrier. Understanding the architecture and dynamics of the plasma membrane has been a central focus of general cellular physiology. Both light and electron microscopy have been fundamental in this endeavor and have been used to reveal the dense, complex, and dynamic nanoscale landscape of the plasma membrane. Here, I review classic and recent developments in the methods used to image and study the structure of the plasma membrane, particularly light, electron, and correlative microscopies. I will discuss their history and use for mapping the plasma membrane and focus on how these tools have provided a structural framework for understanding the membrane at the scale of molecules. Finally, I will describe how these studies provide a roadmap for determining the nanoscale architecture of other organelles and entire cells in order to bridge the gap between cellular form and function.
Topics: Animals; Cell Membrane; History, 20th Century; History, 21st Century; Humans; Microscopy, Electron; Microscopy, Fluorescence
PubMed: 31253697
DOI: 10.1085/jgp.201812227 -
Microbiological Reviews Jun 1995The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the... (Review)
Review
The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the lipid bilayer. Since most lipid-synthesizing enzymes in Saccharomyces cerevisiae are located in intracellular organelles, an extensive flux of lipids from these organelles to the plasma membrane is required. Although the pathway of protein traffic to the plasma membrane is similar to that of most of the lipids, the bulk flow of lipids is separate from vesicle-mediated protein transport. Recent advances in the analysis of membrane budding and membrane fusion indicate that the mechanisms of protein transport from the endoplasmic reticulum to the Golgi and from the Golgi to plasma membrane are similar. The majority of plasma membrane proteins transport solutes across the membrane. A number of ATP-dependent export systems have been detected that couple the hydrolysis of ATP to transport of molecules out of the cell. The hydrolysis of ATP by the plasma membrane H(+)-ATPase generates a proton motive force which is used to drive secondary transport processes. In S. cerevisiae, many substrates are transported by more than one system. Transport of monosaccharide is catalyzed by uniport systems, while transport of disaccharides, amino acids, and nucleosides is mediated by proton symport systems. Transport activity can be regulated at the level of transcription, e.g., induction and (catabolite) repression, but transport proteins can also be affected posttranslationally by a process termed catabolite inactivation. Catabolite inactivation is triggered by the addition of fermentable sugars, intracellular acidification, stress conditions, and/or nitrogen starvation. Phosphorylation and/or ubiquitination of the transport proteins has been proposed as an initial step in the controlled inactivation and degradation of the target enzyme. The use of artificial membranes, like secretory vesicles and plasma membranes fused with proteoliposomes, as model systems for studies on the mechanism and regulation of transport is evaluated.
Topics: Amino Acid Sequence; Biological Transport; Cell Membrane; Membrane Lipids; Molecular Sequence Data; Saccharomyces cerevisiae
PubMed: 7603412
DOI: 10.1128/mr.59.2.304-322.1995 -
BioEssays : News and Reviews in... Feb 2016The fundamental mechanisms of protein and lipid organization at the plasma membrane have continued to engage researchers for decades. Among proposed models, one idea has... (Review)
Review
The fundamental mechanisms of protein and lipid organization at the plasma membrane have continued to engage researchers for decades. Among proposed models, one idea has been particularly successful which assumes that sterol-dependent nanoscopic phases of different lipid chain order compartmentalize proteins, thereby modulating protein functionality. This model of membrane rafts has sustainably sparked the fields of membrane biophysics and biology, and shifted membrane lipids into the spotlight of research; by now, rafts have become an integral part of our terminology to describe a variety of cell biological processes. But is the evidence clear enough to continue supporting a theoretical concept which has resisted direct proof by observation for nearly twenty years? In this essay, we revisit findings that gave rise to and substantiated the raft hypothesis, discuss its impact on recent studies, and present alternative mechanisms to account for plasma membrane heterogeneity.
Topics: Cell Membrane; Membrane Lipids; Membrane Proteins
PubMed: 26666984
DOI: 10.1002/bies.201500150 -
The EMBO Journal Aug 2006Cell membranes are fascinating supramolecular aggregates that not only form a barrier between compartments but also harbor many chemical reactions essential to the... (Comparative Study)
Comparative Study Review
Cell membranes are fascinating supramolecular aggregates that not only form a barrier between compartments but also harbor many chemical reactions essential to the existence and functioning of a cell. Here, it is proposed to review the molecular dynamics and mosaic organization of the plasma membrane, which are thought to have important functional implications. We will first summarize the basic concepts of Brownian diffusion and lipid domain formation in model membranes and then track the development of ideas and tools in this field, outlining key results obtained on the dynamic processes at work in membrane structure and assembly. We will focus in particular on findings made using fluorescent labeling and imaging procedures to record these dynamic processes. We will also discuss a few examples showing the impact of lateral diffusion on cell signal transduction, and outline some future methodological challenges which must be met before we can answer some of the questions arising in this field of research.
Topics: Animals; Cell Membrane; Humans; Kinetics; Membrane Fluidity; Membrane Microdomains; Models, Biological; Signal Transduction; Spectrometry, Fluorescence
PubMed: 16900097
DOI: 10.1038/sj.emboj.7601204 -
Biochimica Et Biophysica Acta.... Sep 2017The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an...
The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an active role and regulates receptor distribution and function by its composition and the interaction of its lipid components with embedded and surrounding proteins. Furthermore, it is not a homogenous fluid but contains lipid and protein domains of various sizes and characteristic lifetimes which are important in regulating receptor function and signaling. The precise lateral organization of the plasma membrane, the differences between the inner and outer leaflet, and the influence of the cytoskeleton are still debated. Furthermore, there is a lack of comparisons of the organization and dynamics of the plasma membrane of different cell types. Therefore, we used four different specific membrane markers to test the lateral organization, the differences between the inner and outer membrane leaflet, and the influence of the cytoskeleton of up to five different cell lines, including Chinese hamster ovary (CHO-K1), Human cervical carcinoma (HeLa), neuroblastoma (SH-SY5Y), fibroblast (WI-38) and rat basophilic leukemia (RBL-2H3) cells by Imaging Total Internal Reflection (ITIR)-Fluorescence Correlation Spectroscopy (FCS). We measure diffusion in the temperature range of 298-310K to measure the Arrhenius activation energy (E) of diffusion and apply the FCS diffusion law to obtain information on the spatial organization of the probe molecules on the various cell membranes. Our results show clear differences of the FCS diffusion law and E for the different probes in dependence of their localization. These differences are similar in the outer and inner leaflet of the membrane. However, these values can differ significantly between different cell lines raising the question how molecular plasma membrane events measured in different cell lines can be compared. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
Topics: Animals; CHO Cells; Cell Membrane; Cricetinae; Cricetulus; Cytoskeleton; Fibroblasts; HeLa Cells; Humans; Lipid Bilayers; Membrane Microdomains; Rats; Spectrometry, Fluorescence
PubMed: 27998689
DOI: 10.1016/j.bbamem.2016.12.009 -
Traffic (Copenhagen, Denmark) Oct 2018A cell is able to sense the biomechanical properties of the environment such as the rigidity of the extracellular matrix and adapt its tension via regulation of plasma... (Review)
Review
A cell is able to sense the biomechanical properties of the environment such as the rigidity of the extracellular matrix and adapt its tension via regulation of plasma membrane and underlying actomyosin meshwork properties. The cell's ability to adapt to the changing biomechanical environment is important for cellular homeostasis and also cell dynamics such as cell growth and motility. Membrane trafficking has emerged as an important mechanism to regulate cell biomechanics. In this review, we summarize the current understanding of the role of cell mechanics in exocytosis, and reciprocally, the role of exocytosis in regulating cell mechanics. We also discuss how cell mechanics and membrane trafficking, particularly exocytosis, can work together to regulate cell polarity and motility.
Topics: Animals; Biomechanical Phenomena; Cell Membrane; Cell Movement; Cell Polarity; Exocytosis; Humans; Membrane Fusion; Protein Transport
PubMed: 29943478
DOI: 10.1111/tra.12584