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Membrane curvature

Nathan Nguyen, Vladimir Shteyn, Thomas J Melia
In response to intracellular stress events ranging from starvation to pathogen invasion, the cell activates one or more forms of macroautophagy. The key event in these related pathways is the de novo formation of a new organelle called the autophagosome, which surrounds and sequesters either random portions of the cytoplasm or selectively targets individual intracellular challenges. Thus the autophagosome is a flexible membrane platform with dimensions that ultimately depend upon the target cargo. The intermediate membrane, termed the phagophore or isolation membrane, is a cup-like structure with a clear concave face and a highly curved rim...
January 11, 2017: Journal of Molecular Biology
Yves F Dufrêne
Studying the structure, properties, and interactions of microbial cells is key to understanding the functions of the microbiome. Recent advances in nanotechnology have offered new tools to probe microbes at the single-molecule and single-cell levels. In this issue of ACS Nano, Kumar et al. present an atomic force microscopy method that is capable of imaging the nanoscale organization of bacterial proteins in native, curved membranes. This study represents an important step forward in the development of nanoscopy techniques for analyzing biological systems with large curvature and vertical dimensions, such as membrane vesicles and bacterial cells...
January 12, 2017: ACS Nano
Aniket Magarkar, Piotr Jurkiewicz, Christoph Allolio, Martin Hof, Pavel Jungwirth
Calcium ion is the ubiquitous messenger in cells and plays a key role in neuronal signaling and fusion of synaptic vesicles. These vesicles are typically ∼20-50 nm in diameter, and thus their interaction with calcium ions cannot be modeled faithfully with a conventional flat membrane bilayer setup. Within our newly developed molecular dynamics simulations setup, we characterize here interactions of the calcium ion with curved membrane interfaces with atomistic detail. The present molecular dynamics simulations together with time-dependent fluorescence shift experiments suggest that the mode and strength of interaction of calcium ion with a phospholipid bilayer depends on its curvature...
January 11, 2017: Journal of Physical Chemistry Letters
Ieva Ailte, Anne Berit Dyve Lingelem, Audun Sverre Kvalvaag, Simona Kavaliauskiene, Andreas Brech, Gerbrand Koster, Paul Gunnar Dommersnes, Jonas Bergan, Tore Skotland, Kirsten Sandvig
In this study, we have investigated how clathrin-dependent endocytosis is affected by exogenously added lysophospholipids (LPLs). Addition of LPLs with large head groups strongly inhibits transferrin (Tf) endocytosis in various cell lines, while LPLs with small head groups do not. Electron and total internal reflection fluorescence microscopy (EM and TIRF) reveal that treatment with lysophosphatidylinositol (LPI) with the fatty acyl group C18:0 leads to reduced numbers of invaginated clathrin-coated pits (CCPs) at the plasma membrane, fewer endocytic events per membrane area and increased lifetime of CCPs...
January 9, 2017: Traffic
Seng Koon Lim, Andrew S W Wong, Hans-Peter M de Hoog, Padmini Rangamani, Atul N Parikh, Madhavan Nallani, Sara Sandin, Bo Liedberg
Many common amphiphiles self-assemble in water to produce heterogeneous populations of discrete and symmetric but polydisperse and multilamellar vesicles isolating the encapsulated aqueous core from the surrounding bulk. But when mixtures of amphiphiles of vastly different elastic properties co-assemble, their non-uniform molecular organization can stabilize lower symmetries and produce novel shapes. Here, using high resolution electron cryomicroscopy and tomography, we identify the spontaneous formation of a membrane morphology consisting of unilamellar tubular vesicles in dilute aqueous solutions of binary mixtures of two different amphiphiles of vastly different origins...
January 6, 2017: Soft Matter
T B Stanishneva-Konovalova, N I Derkacheva, S V Polevova, O S Sokolova
Many cellular processes are associated with membrane remodeling. The BAR domain protein family plays a key role in the formation and detection of local membrane curvatures and in attracting other proteins, including the regulators of actin dynamics. Based on their structural and phylogenetic properties, BAR domains are divided into several groups which affect membrane in various ways and perform different functions in cells. However, recent studies have uncovered evidence of functional differences even within the same group...
October 2016: Acta Naturae
Ido Yofe, Kareem Soliman, Silvia G Chuartzman, Bruce Morgan, Uri Weill, Eden Yifrach, Tobias P Dick, Sara J Cooper, Christer S Ejsing, Maya Schuldiner, Einat Zalckvar, Sven Thoms
Peroxisomes are cellular organelles with vital functions in lipid, amino acid, and redox metabolism. The cellular formation and dynamics of peroxisomes are governed by PEX genes, however, the regulation of peroxisome abundance is yet poorly understood. Here we use a high-content microscopy screen to identify novel regulators of peroxisome size and abundance. Our screen led to the identification of a previously uncharacterized gene, which we term PEX35, which affects peroxisome abundance. PEX35 encodes a peroxisomal membrane protein, a remote homolog to several curvature generating human proteins...
January 3, 2017: Journal of Cell Science
Keith Promislow, Qiliang Wu
Multicomponent bilayer structures arise as the ubiquitous plasma membrane in cellular biology and as blends of amphiphilic copolymers used in electrolyte membranes, drug delivery, and emulsion stabilization within the context of synthetic chemistry. We present the multicomponent functionalized Cahn-Hilliard (mFCH) free energy as a model which allows competition between bilayers with distinct composition and between bilayers and higher codimensional structures, such as co-dimension two filaments and co-dimension three micelles...
December 31, 2016: Journal of Mathematical Biology
Ningwei Li, Nima Sharifi-Mood, Fuquan Tu, Daeyeon Lee, Ravi Radhakrishnan, Tobias Baumgart, Kathleen J Stebe
Inspired by proteins that generate membrane curvature, sense the underlying membrane geometry, and migrate driven by curvature gradients, we explore the question: Can colloids, adhered to lipid bilayers, also sense and respond to membrane geometry? We report the migration of Janus microparticles adhered to giant unilamellar vesicles elongated to present spatially varying curvatures. In our experiments, colloids migrate only when the membranes are tense, suggesting that they migrate to minimize membrane area...
December 30, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Sai Janani Ganesan, Hongcheng Xu, Silvina Matysiak
Phosphatidylserine (PS) and phosphatidylcholine (PC) are two of the major anionic and zwitterionic phospholipids in mammalian cell membranes. Ion-PS interaction is hypothesized to play a crucial role in a range of biological events including membrane fusion, lipid phase modulation, membrane protein insertion and translocation. In this study, we characterize using coarse-grained simulations, lipid nanodomain formation in PC/PS mixed bilayers. We investigate the effect of monovalent cation sizes in modulating lipid-ion binding modes and lipid demixing...
December 21, 2016: Journal of Physical Chemistry. B
Talita L Santos, Adolfo Moraes, Clovis R Nakaie, Fabio C L Almeida, Shirley Schreier, Ana Paula Valente
A large number of antimicrobial peptides (AMPs) acts with high selectivity and specificity through interactions with membrane lipid components. These peptides undergo complex conformational changes in solution; upon binding to an interface, one major conformation is stabilized. Here we describe a study of the interaction between tritrpticin (TRP3), a cathelicidin AMP, and micelles of different chemical composition. The peptide's structure and dynamics were examined using one-dimensional and two-dimensional NMR...
December 20, 2016: Biophysical Journal
I Yu Golushko, S B Rochal, V L Lorman
The tubular lipid membranes (TLMs) pulled out from vesicles are often used in in vitro studies of the interactions between curvature-inducing proteins and highly curved membranes. The protein molecules adsorbed at the membrane surface deform the TLM and couple with each other due to the induced strain. Here we propose an approach which models the single curvature-inducing protein action on the lipid bilayer by the multipole, the superposition of the point forces applied to the membrane in the region of the protein adsorption...
December 2016: European Physical Journal. E, Soft Matter
Tsogbadrakh Mishig-Ochir, Davaadulam Gombosuren, Altanchimeg Jigjid, Badamkhatan Tuguldur, Galbadrakh Chuluunbaatar, Enerelt Urnukhsaikhan, Chinar Pathak, Bong-Jin Lee
Naturally occurring antimicrobial peptides important for innate immunity are widely studied for their antimicrobial and anticancer activity. The primary target of these AMPs is believed to be the bacterial cytoplasmic membrane. However, the interaction between cytoplasmic membrane and the antimicrobial peptides remains poorly understood. Therefore to focus on the target membrane composition that is required by AMPs to interact with membranes, we have examined the interaction of the antimicrobial and anticancer active 11-residue GA-K4 (FLKWLFKWAKK) peptide with model and intact cell membranes...
December 16, 2016: Protein and Peptide Letters
Lei Zheng, Yibin Lin, Shuo Lu, Jiazhe Zhang, Mikhail Bogdanov
Lysophospholipids (LPLs) are metabolic intermediates in bacterial phospholipid turnover. Distinct from their diacyl counterparts, these inverted cone-shaped molecules share physical characteristics of detergents, enabling modification of local membrane properties such as curvature. The functions of LPLs as cellular growth factors or potent lipid mediators have been extensively demonstrated in eukaryotic cells but are still undefined in bacteria. In the envelope of Gram-negative bacteria, LPLs are derived from multiple endogenous and exogenous sources...
December 9, 2016: Biochimica et Biophysica Acta
Xin Yi, Huajian Gao
The interaction between particles and lipid biomembranes plays an essential role in many fields such as endocytosis, drug delivery, and intracellular traffic. Here we conduct a theoretical study on the incorporation of elastic particles of different sizes and rigidities into a lipid vesicle through adhesive wrapping. It is shown that while the incorporation of relatively small particles involves smooth shape evolution, the vesicle wrapping of large particles exhibits a discontinuous shape transition, followed by a protrusion of the vesicle membrane at infinitesimal cost of elastic deformation energy...
December 13, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Matthieu Fillion, Maxime Goudreault, Normand Voyer, Burkhard Bechinger, Michèle Auger
Cationic antimicrobial peptides are a component of the innate immune system of several organisms and represent an interesting alternative to fight multiresistant bacteria. In this context, we have elaborated a synthetic peptide scaffold allowing the study of the impact of different molecular determinants on the membrane interactions. The aim of the present study was to elucidate the mechanism of action of two cationic peptides that derive from a neutral 14-mer template peptide and where the hydrophilic portion is composed of a crown ether...
December 13, 2016: Biochemistry
Weria Pezeshkian, Haifei Gao, Senthil Arumugam, Ulrike Becken, Patricia Bassereau, Jean-Claude Florent, John Hjort Ipsen, Ludger Johannes, Julian C Shillcock
The bacterial Shiga toxin interacts with its cellular receptor, the glycosphingolipid globotriaosylceramide (Gb3 or CD77), as a first step to entering target cells. Previous studies have shown that toxin molecules cluster on the plasma membrane, despite the apparent lack of direct interactions between them. The precise mechanism by which this clustering occurs remains poorly defined. Here, we used vesicle and cell systems and computer simulations to show that line tension due to curvature, height, or compositional mismatch, and lipid or solvent depletion cannot drive the clustering of Shiga toxin molecules...
December 16, 2016: ACS Nano
Javier M Hernandez
Liposomes constitute a convenient biochemical model system to investigate mechanistic aspects of the membrane fusion of synaptic vesicles. The proteins responsible for mediating fusion are the SNAREs that belong to a highly conserved family of transmembrane proteins. Reconstituting SNAREs into liposomes using detergents has become a common approach not only to understand how SNAREs work, but also how fusion is regulated by the vast array of accessory proteins present at the presynapse. However, a concern has been that the high curvature stress of the small liposomes (diameters of ~40 nm) frequently used in many studies renders them prone to spontaneous fusion, bringing into question whether the measurements obtained faithfully represent SNARE-mediated fusion...
2017: Methods in Molecular Biology
Meera Shete, Manjesh Kumar, Donghun Kim, Neel Rangnekar, Dandan Xu, Berna Topuz, Kumar Varoon Agrawal, Evguenia Karapetrova, Benjamin Stottrup, Shaeel Al-Thabaiti, Sulaiman Basahel, Katabathini Narasimharao, Jeffrey D Rimer, Michael Tsapatsis
Nanoscale crystal growth control is crucial for tailoring two-dimensional (2D) zeolites (crystallites with thickness less than two unit cells) and thicker zeolite nanosheets for applications in separation membranes and as hierarchical catalysts. However, methods to control zeolite crystal growth with nanometer precision are still in their infancy. Herein, we report solution-based growth conditions leading to anisotropic epitaxial growth of 2D zeolites with rates as low as few nanometers per day. Contributions from misoriented surface nucleation and rotational intergrowths are eliminated...
January 9, 2017: Angewandte Chemie
Armando Jerome de Jesus, Hang Yin
Computer simulations have become an indispensable tool in studying molecular biological systems. The unmatched spatial and temporal resolution that it offers enables for microscopic-level views into the dynamics and mechanics of biological systems. Recent advances in hardware resources have also opened up to computer simulations the investigation of longer timescale biological processes and larger systems. The study of membrane proteins or peptides especially benefits from simulations due to difficulties related to crystallization of such proteins in a membrane environment...
2017: Methods in Molecular Biology
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