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Membrane curvature

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https://www.readbyqxmd.com/read/28647060/lipid-droplets-can-spontaneously-bud-off-from-a-symmetric-bilayer
#1
François Deslandes, Abdou Rachid Thiam, Lionel Forêt
Lipid droplets (LDs) are cytosolic organelles that protrude from the endoplasmic reticulum membrane under energy-rich conditions. How an LD buds off from the endoplasmic reticulum bilayer is still elusive. By using a continuous media description, we computed the morphology of a lipid droplet embedded in between two identical monolayers of a bilayer. We found that beyond a critical volume, the droplet morphology abruptly transits from a symmetrical elongated lens to a spherical protrusion. This budding transition does not require any energy-consuming machinery, or curvature-inducing agent, or intrinsic asymmetry of the bilayer; it is solely driven by the large interfacial energy of the LD, as opposed to the bilayer surface tension...
June 21, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28645851/nanotubes-connecting-b-lymphocytes-high-impact-of-differentiation-dependent-lipid-composition-on-their-growth-and-mechanics
#2
Eszter A Tóth, Ádám Oszvald, Mária Péter, Gábor Balogh, Anikó Osteikoetxea-Molnár, Tamás Bozó, Edina Szabó-Meleg, Miklós Nyitrai, Imre Derényi, Miklós Kellermayer, Toshiyuki Yamaji, Kentaro Hanada, László Vígh, János Matkó
Nanotubes (NTs) are thin, long membranous structures forming novel, yet poorly known communication pathways between various cell types. Key mechanisms controlling their growth still remained poorly understood. Since NT-forming capacity of immature and mature B cells was found largely different, we investigated how lipid composition and molecular order of the membrane affect NT-formation. Screening B cell lines with various differentiation stages revealed that NT-growth linearly correlates with membrane ganglioside levels, while it shows maximum as a function of cholesterol level...
June 20, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28644713/an-unstructured-loop-that-is-critical-for-interactions-of-the-stalk-domain-of-drp1-with-saturated-phosphatidic-acid
#3
Yoshihiro Adachi, Miho Iijima, Hiromi Sesaki
Dynamin-related protein 1 (Drp1) is a dynamin superfamily GTPase, which drives membrane constriction during mitochondrial division. To mediate mitochondrial division, Drp1 is recruited to the mitochondrial outer membrane and is assembled into the division machinery. We previously showed that Drp1 interacts with phosphatidic acid (PA) and saturated phospholipids in the mitochondrial membrane, and this interaction restrains Drp1 in initiating the constriction of mitochondria. Here, we show that the role of saturated acyl chains of phospholipids is independent of their contribution to the membrane curvature or lipid packing suggesting their direct interaction with Drp1...
June 23, 2017: Small GTPases
https://www.readbyqxmd.com/read/28644472/placing-and-shaping-liposomes-with-reconfigurable-dna-nanocages
#4
Zhao Zhang, Yang Yang, Frederic Pincet, Marc C Llaguno, Chenxiang Lin
The diverse structure and regulated deformation of lipid bilayer membranes are among a cell's most fascinating features. Artificial membrane-bound vesicles, known as liposomes, are versatile tools for modelling biological membranes and delivering foreign objects to cells. To fully mimic the complexity of cell membranes and optimize the efficiency of delivery vesicles, controlling liposome shape (both statically and dynamically) is of utmost importance. Here we report the assembly, arrangement and remodelling of liposomes with designer geometry: all of which are exquisitely controlled by a set of modular, reconfigurable DNA nanocages...
June 23, 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28639939/model-for-a-novel-membrane-envelope-in-a-filamentous-hyperthermophilic-virus
#5
Edward H Egelman, Peter M Kasson, Frank DiMaio, Xiong Yu, Soizick Lucas-Staat, Mart Krupovic, Stefan Schouten, David Prangishvili
Biological membranes create compartments, and are usually formed by lipid bilayers. However, in hyperthermophilic archaea that live optimally at temperatures above 80°C the membranes are monolayers which resemble fused bilayers. Many double-stranded DNA viruses which parasitize such hosts, including the filamentous virus AFV1 of Acidianus hospitalis, are enveloped with a lipid-containing membrane. Using cryo-EM, we show that the membrane in AFV1 is a ~2 nm-thick monolayer, approximately half the expected membrane thickness, formed by host membrane-derived lipids which adopt a U-shaped 'horseshoe' conformation...
June 22, 2017: ELife
https://www.readbyqxmd.com/read/28634030/effects-of-membrane-curvature-and-ph-on-proton-pumping-activity-of-single-cytochrome-bo3-enzymes
#6
Mengqiu Li, Sanobar Khan, Honglin Rong, Roman Tuma, Nikos S Hatzakis, Lars J C Jeuken
The molecular mechanism of proton pumping by heme-copper oxidases (HCO) has intrigued the scientific community since it was first proposed. We have recently reported a novel technology that enables the continuous characterisation of proton transport activity of a HCO and ubiquinol oxidase from Escherichia coli, cytochrome bo3, for hundreds of seconds on the single enzyme level (Li et al. J Am Chem Soc 137 (2015) 16055-16063). Here, we have extended these studies by additional experiments and analyses of the proton transfer rate as a function of proteoliposome size and pH at the N- and P-side of single HCOs...
June 17, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28632157/development-of-a-novel-transparent-flexible-capacitive-micromachined-ultrasonic-transducer
#7
Da-Chen Pang, Cheng-Min Chang
This paper presents the world's first transparent flexible capacitive micromachined ultrasonic transducer (CMUT) that was fabricated through a roll-lamination technique. This polymer-based CMUT has advantages of transparency, flexibility, and non-contacting detection which provide unique functions in display panel applications. Comprising an indium tin oxide-polyethylene terephthalate (ITO-PET) substrate, SU-8 sidewall and vibrating membranes, and silver nanowire transparent electrode, the transducer has visible-light transmittance exceeding 80% and can operate on curved surfaces with a 40 mm radius of curvature...
June 20, 2017: Sensors
https://www.readbyqxmd.com/read/28631801/morphology-of-elastic-nematic-liquid-crystal-membranes
#8
Pardis Rofouie, Damiano Pasini, Alejandro D Rey
Liquid crystalline phases found in many biological materials, such as actin, DNA, cellulose, and collagen can be responsible for the deformation of cell membranes. In this paper, cell membrane deformation is investigated through the coupling between liquid crystal anisotropy and membrane bending elasticity. The generalized shape equation for anisotropic interfaces, which resort to the Cahn-Hoffman capillarity vector, the Rapini-Papoular anchoring energy, and the Helfrich elastic energy, is applied to gain insight into the deformation of closed liquid crystal membranes...
June 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/28630157/pore-formation-by-dimeric-bak-and-bax-an-unusual-pore
#9
REVIEW
Rachel T Uren, Sweta Iyer, Ruth M Kluck
Apoptotic cell death via the mitochondrial pathway occurs in all vertebrate cells and requires the formation of pores in the mitochondrial outer membrane. Two Bcl-2 protein family members, Bak and Bax, form these pores during apoptosis, and how they do so has been investigated for the last two decades. Many of the conformation changes that occur during their transition to pore-forming proteins have now been delineated. Notably, biochemical, biophysical and structural studies indicate that symmetric homodimers are the basic unit of pore formation...
August 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28628337/buckling-under-pressure-curvature-based-lipid-segregation-and-stability-modulation-in-cardiolipin-containing-bilayers
#10
Kevin J Boyd, Nathan N Alder, Eric R May
Mitochondrial metabolic function is affected by the morphology and protein organization of the mitochondrial inner membrane (MIM). Cardiolipin (CL) is a unique tetra-acyl lipid that is involved in the maintenance of the highly-curved shape of the MIM as well as spatial organization of the proteins necessary for respiration and oxidative phosphorylation. Cardiolipin has been suggested to self-organize into lipid domains due to its inverted conical molecular geometry, though the driving forces for this organization are not fully understood...
June 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28608781/nano-and-microparticles-at-fluid-and-biological-interfaces
#11
Sabyasachi Dasgupta, Thorsten Auth, Gerhard Gompper
Systems with interfaces are abundant in both technological applications and biology. While a fluid interface separates two fluids, membranes separate the inside of vesicles from the outside, the interior of biological cells from the environment, and compartmentalize cells into organelles. The physical properties of interfaces are characterized by interface tension, those of membranes are characterized by bending and stretching elasticity. Amphiphilic molecules like surfactants that are added to a system with two immiscible fluids decrease the interface tension and induce a bending rigidity...
June 13, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28604678/dynamic-subunit-turnover-in-escrt-iii-assemblies-is-regulated-by-vps4-to-mediate-membrane-remodelling-during-cytokinesis
#12
Beata E Mierzwa, Nicolas Chiaruttini, Lorena Redondo-Morata, Joachim Moser von Filseck, Julia König, Jorge Larios, Ina Poser, Thomas Müller-Reichert, Simon Scheuring, Aurélien Roux, Daniel W Gerlich
The endosomal sorting complex required for transport (ESCRT)-III mediates membrane fission in fundamental cellular processes, including cytokinesis. ESCRT-III is thought to form persistent filaments that over time increase their curvature to constrict membranes. Unexpectedly, we found that ESCRT-III at the midbody of human cells rapidly turns over subunits with cytoplasmic pools while gradually forming larger assemblies. ESCRT-III turnover depended on the ATPase VPS4, which accumulated at the midbody simultaneously with ESCRT-III subunits, and was required for assembly of functional ESCRT-III structures...
June 12, 2017: Nature Cell Biology
https://www.readbyqxmd.com/read/28597524/loosening-of-lipid-packing-promotes-oligoarginine-entry-into-cells
#13
Tomo Murayama, Toshihiro Masuda, Sergii Afonin, Kenichi Kawano, Tomoka Takatani-Nakase, Hiroki Ida, Yasufumi Takahashi, Takeshi Fukuma, Anne S Ulrich, Shiroh Futaki
Despite extensive use of arginine-rich cell-penetrating peptides (CPPs)-including octaarginine (R8)-as intracellular delivery vectors, mechanisms for their internalization are still under debate. Lipid packing in live cell membranes was characterized using a polarity-sensitive dye (di-4-ANEPPDHQ), and evaluated in terms of generalized polarization. Treatment with membrane curvature-inducing peptides led to significant loosening of the lipid packing, resulting in an enhanced R8 penetration. Pyrenebutyrate (PyB) is known to facilitate R8 membrane translocation by working as a hydrophobic counteranion...
June 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28596722/unique-structural-features-of-membrane-bound-c-terminal-domain-motifs-modulate-complexin-inhibitory-function
#14
David Snead, Alex L Lai, Rachel T Wragg, Daniel A Parisotto, Trudy F Ramlall, Jeremy S Dittman, Jack H Freed, David Eliezer
Complexin is a small soluble presynaptic protein that interacts with neuronal SNARE proteins in order to regulate synaptic vesicle exocytosis. While the SNARE-binding central helix of complexin is required for both the inhibition of spontaneous fusion and the facilitation of synchronous fusion, the disordered C-terminal domain (CTD) of complexin is specifically required for its inhibitory function. The CTD of worm complexin binds to membranes via two distinct motifs, one of which undergoes a membrane curvature dependent structural transition that is required for efficient inhibition of neurotransmitter release, but the conformations of the membrane-bound motifs remain poorly characterized...
2017: Frontiers in Molecular Neuroscience
https://www.readbyqxmd.com/read/28593141/glycosyl-chains-and-25-hydroxycholesterol-contribute-to-the-intracellular-transport-of-amyloid-beta-a%C3%AE-42-in-jurkat-t-cells
#15
Neha Sharma, KeangOK Baek, Huong T T Phan, Naofumi Shimokawa, Masahiro Takagi
Amyloid beta (Aβ) is a peptide responsible for the development of Alzheimer's disease (AD). Misfolding and accumulation of endogenous Aβ can lead to neural cell apoptosis through endoplasmic reticulum (ER) stress. Added exogenous Aβ can also result in ER stress, leading to neurotoxicity and apoptosis, which is identical to that caused by the endogenous peptide. We have speculated that the endocytic transport of Aβ causes ER stress and have previously shown that the oxysterol, in particular, 7-ketocholesterol (7-keto) induces more surface interaction between Aβ-42 and Jurkat cells than cholesterol...
June 2017: FEBS Open Bio
https://www.readbyqxmd.com/read/28591608/ceramide-c16-is-a-versatile-modulator-of-phosphatidylethanolamine-polymorphism
#16
Mahmoudreza Doroudgar, Michel Lafleur
Ceramide-C16 (CerC16) is a sphingolipid associated with several diseases like diabetes, obesity, Parkinson disease, and certain types of cancers. As a consequence, research efforts are devoted to identify the impact of CerC16 on the behavior of membranes, and to understand how it is involved in these diseases. In this work, we investigated the impacts of CerC16 (up to 20 mol %) on the lipid polymorphism of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), using differential scanning calorimetry, and sequential (2)H and (31)P solid-state nuclear magnetic resonance spectroscopy...
June 6, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28588593/salinity-induced-palmella-formation-mechanism-in-halotolerant-algae-dunaliella-salina-revealed-by-quantitative-proteomics-and-phosphoproteomics
#17
Sijia Wei, Yangyang Bian, Qi Zhao, Sixue Chen, Jiawei Mao, Chunxia Song, Kai Cheng, Zhen Xiao, Chuanfang Zhang, Weimin Ma, Hanfa Zou, Mingliang Ye, Shaojun Dai
Palmella stage is critical for some unicellular algae to survive in extreme environments. The halotolerant algae Dunaliella salina is a good single-cell model for studying plant adaptation to high salinity. To investigate the molecular adaptation mechanism in salinity shock-induced palmella formation, we performed a comprehensive physiological, proteomics and phosphoproteomics study upon palmella formation of D. salina using dimethyl labeling and Ti(4+)-immobilized metal ion affinity chromatography (IMAC) proteomic approaches...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28588242/photoswitchable-phospholipid-fret-acceptor-detergent-free-intermembrane-transfer-assay-of-fluorescent-lipid-analogs
#18
Mariko Sumi, Asami Makino, Takehiko Inaba, Yasushi Sako, Fumihiro Fujimori, Peter Greimel, Toshihide Kobayashi
We have developed and characterized a novel photoswitchable phospholipid analog termed N-nitroBIPS-DPPG. The fluorescence can be switched on and off repeatedly with minimal photobleaching by UV or visible light exposure, respectively. The rather large photochromic head group is inserted deeply into the interfacial membrane region conferring a conical overall lipid shape, preference for a positive curvature and only minimal intermembrane transfer. Utilizing the switchable NBD fluorescence quenching ability of N-nitroBIPS-DPPG, a detergent free intermembrane transfer assay system for NBD modified lipids was demonstrated and validated...
June 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28587828/diphytanoyl-lipids-as-model-systems-for-studying-membrane-active-peptides
#19
Sezgin Kara, Sergii Afonin, Oleg Babii, Anton N Tkachenko, Igor V Komarov, Anne S Ulrich
The branched chains in diphytanoyl lipids provide membranes with unique properties, such as high chemical/physical stability, low water permeability, and no gel-to-fluid phase transition at ambient temperature. Synthetic diphytanoyl phospholipids are often used as model membranes for electrophysiological experiments. To evaluate whether these sturdy lipids are also suitable for solid-state NMR, we have examined their interactions with a typical amphiphilic peptide in comparison with straight-chain lipids. First, their phase properties were monitored using (31)P-NMR, and the structural behaviour of the antimicrobial peptide PGLa was studied by (19)F-NMR and circular dichroism in oriented membrane samples...
June 3, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28581510/nanoscale-manipulation-of-membrane-curvature-for-probing-endocytosis-in-live-cells
#20
Wenting Zhao, Lindsey Hanson, Hsin-Ya Lou, Matthew Akamatsu, Praveen D Chowdary, Francesca Santoro, Jessica R Marks, Alexandre Grassart, David G Drubin, Yi Cui, Bianxiao Cui
Clathrin-mediated endocytosis (CME) involves nanoscale bending and inward budding of the plasma membrane, by which cells regulate both the distribution of membrane proteins and the entry of extracellular species. Extensive studies have shown that CME proteins actively modulate the plasma membrane curvature. However, the reciprocal regulation of how the plasma membrane curvature affects the activities of endocytic proteins is much less explored, despite studies suggesting that membrane curvature itself can trigger biochemical reactions...
June 5, 2017: Nature Nanotechnology
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