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Membrane curvature

Myungwoon Lee, Hongwei Yao, Byungsu Kwon, Alan J Waring, Peter Ruchala, Chandan Singh, Mei Hong
Enveloped viruses enter cells by using their fusion proteins to merge the virus lipid envelope and the cell membrane. While crystal structures of the water-soluble ectodomains of many viral fusion proteins have been determined, the structure and assembly of the C-terminal transmembrane domain (TMD) remains poorly understood. Here we use solid-state NMR to determine the backbone conformation and oligomeric structure of the TMD of the parainfluenza virus 5 (PIV5) fusion protein. 13C chemical shifts indicate that the central leucine-rich segment of the TMD is α-helical in POPC/cholesterol membranes and POPE membranes, while the Ile- and Val-rich termini shift to the β-strand conformation in the POPE membrane...
January 9, 2018: Journal of Molecular Biology
Elias T Spiliotis
The actin and microtubule cytoskeletons comprise a variety of networks with distinct architectures, dynamics and protein composition. A fundamental question in eukaryotic cell biology is how these networks are spatially and temporally controlled, so they are positioned in the right intracellular places at the right time. While significant progress has been made in understanding the self-assembly of actin and microtubule networks, less is known about how they are patterned and regulated in a site-specific manner...
January 11, 2018: Journal of Cell Science
Stephan L Grage, Sezgin Kara, Andrea Bordessa, Véronique Doan, Fabio Rizzolo, Marina Putzu, Tomáš Kubař, Anna Maria Papini, Grégory Chaume, Thierry Brigaud, Sergii Afonin, Anne S Ulrich
Peptaibols are promising drug candidates in view of their interference with cellular membranes. Knowledge of their lipid interactions and membrane-bound structure is needed for understanding their activity and should be in principle accessible by solid-state NMR. However, their unusual amino acid composition and their non-canonical conformations make it very challenging to find suitable NMR labels. Especially in the case of short sequences, new strategies are required to maximize the structural information that can be obtained from each label...
January 11, 2018: Chemistry: a European Journal
Zhanghan Wu, Maohan Su, Cheesan Tong, Min Wu, Jian Liu
Immune cells exhibit stimulation-dependent traveling waves in the cortex, much faster than typical cortical actin waves. These waves reflect rhythmic assembly of both actin machinery and peripheral membrane proteins such as F-BAR domain-containing proteins. Combining theory and experiments, we develop a mechanochemical feedback model involving membrane shape changes and F-BAR proteins that render the cortex an interesting dynamical system. We show that such cortical dynamics manifests itself as ultrafast traveling waves of cortical proteins, in which the curvature sensitivity-driven feedback always constrains protein lateral diffusion in wave propagation...
January 10, 2018: Nature Communications
Barbara Eicher, Drew Marquardt, Frederick A Heberle, Ilse Letofsky-Papst, Gerald N Rechberger, Marie-Sousai Appavou, John Katsaras, Georg Pabst
We measured the effect of intrinsic lipid curvature, J0, on structural properties of asymmetric vesicles made of palmitoyl-oleoyl-phosphatidylethanolamine (POPE; J0<0) and palmitoyl-oleoyl-phosphatidylcholine (POPC; J0∼0). Electron microscopy and dynamic light scattering were used to determine vesicle size and morphology, and x-ray and neutron scattering, combined with calorimetric experiments and solution NMR, yielded insights into leaflet-specific lipid packing and melting processes. Below the lipid melting temperature we observed strong interleaflet coupling in asymmetric vesicles with POPE inner bilayer leaflets and outer leaflets enriched in POPC...
January 9, 2018: Biophysical Journal
Dariush Mohammadyani, Naveena Yanamala, Alejandro K Samhan Arias, Alexander A Kapralov, German Stepanov, Nick Nuar, Joan Planas-Iglesias, Narinder Sanghera, Valerian E Kagan, Judith Klein-Seetharaman
The interaction between CL and cytochrome c (cyt-c), results in a gain of function of peroxidase activity by cyt-c. Despite intensive research, disagreements on nature and molecular details of this interaction remain. In particular, it is still not known how the interaction triggers the onset of apoptosis. Enzymatic characterization of peroxidase activity has highlighted the need for a critical threshold concentration of CL, a finding of profound physiological relevance in vivo. Using solution NMR, fluorescence spectroscopy, and in silico modeling approaches we here confirm that full binding of cyt-c to the membrane requires a CL:cyt-c threshold ratio of 5:1...
January 6, 2018: Biochimica et Biophysica Acta
H Wensink, Libertad Morales Anda
Chiral rodlike colloids exposed to strong depletion attraction may self-assemble into chiral membranes whose twisted director field differs from that of a 3D bulk chiral nematic. We formulate a simple microscopic variational theory to determine the elastic moduli of rods assembled into a bidimensional smectic membrane. The approach is based on a simple Onsager-Straley theory for a non-uniform director field that we apply to describe rod twist within the membrane. A microscopic approach enables a detailed estimate of the individual Frank elastic moduli (splay, twist and bend) as well as the twist penetration depth of the smectic membrane in relation to the rod density and shape...
January 9, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yu-Tzu Shih, Yi-Ping Hsueh
The endoplasmic reticulum (ER) is the biggest organelle in cells and is involved in versatile cellular processes. Formation and maintenance of ER morphology are regulated by a series of proteins controlling membrane fusion and curvature. At least six different ER morphology regulators have been demonstrated to be involved in neurological disorders-including Valosin-containing protein (VCP), Atlastin-1 (ATL1), Spastin (SPAST), Reticulon 2 (RTN2), Receptor expression enhancing protein 1 (REEP1) and RAB10-suggesting a critical role of ER formation in neuronal activity and function...
January 8, 2018: Journal of Biomedical Science
Marc Z Miskin, Kyle J Dorsey, Baris Bircan, Yimo Han, David A Muller, Paul L McEuen, Itai Cohen
Origami-inspired fabrication presents an attractive platform for miniaturizing machines: thinner layers of folding material lead to smaller devices, provided that key functional aspects, such as conductivity, stiffness, and flexibility, are persevered. Here, we show origami fabrication at its ultimate limit by using 2D atomic membranes as a folding material. As a prototype, we bond graphene sheets to nanometer-thick layers of glass to make ultrathin bimorph actuators that bend to micrometer radii of curvature in response to small strain differentials...
January 2, 2018: Proceedings of the National Academy of Sciences of the United States of America
Coline Prévost, Feng-Ching Tsai, Patricia Bassereau, Mijo Simunovic
The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many different proteins associate with curved membranes because of their ability to sense or induce membrane curvature. Typically, these processes involve a multitude of proteins making them too complex to study quantitatively in the cell. We describe a protocol to reconstitute a curved membrane in vitro, mimicking a curved cellular structure, such as the endocytic neck...
December 7, 2017: Journal of Visualized Experiments: JoVE
Amir Houshang Bahrami, Thomas R Weikl
Besides direct particle-particle interactions, nanoparticles adsorbed to biomembranes experience indirect interactions that are mediated by the membrane curvature arising from particle adsorption. In this letter, we show that the curvature-mediated interactions of adsorbed Janus particles depend on the initial curvature of the membrane prior to adsorption, i.e. on whether the membrane initially bulges towards or away from the particles in our simulations. The curvature-mediated interaction can be strongly attractive for Janus particles adsorbed to the outside of a membrane vesicle, which initially bulges away from the particles...
December 27, 2017: Nano Letters
Carol Lynn Curchoe, Uri Manor
Intracellular organelles constantly undergo fission to facilitate turnover, transport, and functional changes. The cytoskeleton has long been understood to play a role in these events, and recent work strongly suggests that several conserved molecular players cooperate with the cytoskeleton to mediate the fission process. Membrane curvature-inducing, membrane scission proteins, and force-inducing cytoskeletal proteins all cooperate to drive the fission process. Recent work suggests that the endoplasmic reticulum serves as the linchpin that orchestrates and spatially organizes fission via these curvature-inducing, scission, and force-producing molecules...
November 13, 2017: ACS Biomaterials Science & Engineering
Masumi Villeneuve, Mihoko Tanaka, Natsumi Saito, Hiroyasu Sakamoto, Yoshiteru Hayami
Mixed micelles formed in a ternary-solute aqueous solution of NaOH, iron (III)-ethylenediamine-N,N,N',N'-tetraacetic acid complex (Fe-edta) and 1,2-diheptanoyl-sn-glycero-3-phosphatidyl choline (DHPC) were studied and compared with the mixed adsorbed film reported in Part I of this series to clarify the effect of the curvature of molecular assemblies on the interactions between their Fe-edta and DHPC constituents. The critical micelle concentrations (CMCs), surface tension at the CMC, and solution pH were measured as functions of the mole fractions of NaOH and DHPC...
December 11, 2017: Chemistry and Physics of Lipids
Satyan Sharma, Manfred Lindau
The t-SNARE complex plays a central role in neuronal fusion. Its components, syntaxin-1 and SNAP25, are largely present in individual clusters and partially colocalize at the presumptive fusion site. How these protein clusters modify local lipid composition and membrane morphology is largely unknown. In this work, using coarse-grained molecular dynamics, the transmembrane domains (TMDs) of t-SNARE complexes are shown to form aggregates leading to formation of lipid nanodomains, which are enriched in cholesterol, phosphatidylinositol 4,5-bisphosphate, and gangliosidic lipids...
December 13, 2017: Journal of the American Chemical Society
Nabanita Saha, Somnath Dutta, Shankari P Datta, Srimonti Sarkar
The ESCRT pathway functions at different subcellular membranes to induce their negative curvature, and it has been largely characterized in model eukaryotes belonging to Opisthokonta. But searches of the genomes of many nonopisthokonts belonging to various supergroups indicate that some of them may harbour fewer ESCRT components. Of the genomes explored thus far, one of the most minimal set of ESCRT components was identified in the human pathogen Giardia lamblia, which belongs to Excavata. Here we report that an ESCRT-mediated pathway most likely operates at the peripheral vesicles, which are located at the cell periphery and the bare zone of this protist...
December 6, 2017: European Journal of Cell Biology
Imke A B Pijpers, Loai K E A Abdelmohsen, David S Williams, Jan C M van Hest
Biodegradable nanoarchitectures, with well-defined morphological features, are of great importance for nanomedical research; however, understanding (and thereby engineering) their formation is a substantial challenge. Herein, we uncover the supramolecular potential of PEG-PDLLA copolymers by exploring the physicochemical determinants that result in the transformation of spherical polymersomes into stomatocytes. To this end, we have engineered blended polymersomes (comprising copolymers with varying lengths of PEG), which undergo solvent-dependent reorganization inducing negative spontaneous membrane curvature...
November 21, 2017: ACS Macro Letters
Hikaru Yamamoto, Akihiro Kondo, Toshiki Itoh
Tyrosine kinases are important enzymes that mediate signal transduction at the plasma membrane. While the significance of membrane localization of tyrosine kinases has been well evaluated, the role of membrane curvature in their regulation is unknown. Here, we demonstrate that an intrinsically disordered region in the tyrosine kinase Fer acts as a membrane curvature sensor that preferentially binds to highly curved membranes in vitro. This region forms an amphipathic α-helix upon interaction with curved membranes, aligning hydrophobic residues on one side of the helical structure...
December 2, 2017: Biochemical and Biophysical Research Communications
Anders E Carlsson
Actin polymerization provides driving force to aid several types of processes that involve pulling the plasma membrane into the cell, including phagocytosis, cellular entry of large viruses, and endocytosis. In endocytosis, actin polymerization is especially important under conditions of high membrane tension or high turgor pressure. Recent modeling efforts have shown how actin polymerization can give rise to a distribution of forces around the endocytic site, and explored how these forces affect the shape dynamics; experiments have revealed the structure of the endocytic machinery in increasing detail, and demonstrated key feedback interactions between actin assembly and membrane curvature...
December 2, 2017: Current Opinion in Cell Biology
Boguslaw Sadlik, Lukasz Kolodziej, Adrian Blasiak, Mateusz Szymczak, Bartłomiej Warchal
BACKGROUND: Surgical treatment for large osteochondral lesions of the talar dome (OLTD) must restore the convexity and curvature of the talus. Here, we present midterm results and describe the modified "sandwich" reconstruction procedure. Bone defects were restored using a biological inlay consists of autologous bone chips that were mixed with bone marrow concentrate and fibrin glue and covered with a xenogeneic collagen membrane infiltrated with bone marrow concentrate and stabilized by fibrin glue...
December 2017: Foot and Ankle Surgery: Official Journal of the European Society of Foot and Ankle Surgeons
Michelle W Lee, Ernest Y Lee, Ghee Hwee Lai, Nolan W Kennedy, Ammon E Posey, Wujing Xian, Andrew L Ferguson, R Blake Hill, Gerard C L Wong
Dnm1 and Fis1 are prototypical proteins that regulate yeast mitochondrial morphology by controlling fission, the dysregulation of which can result in developmental disorders and neurodegenerative diseases in humans. Loss of Dnm1 blocks the formation of fission complexes and leads to elongated mitochondria in the form of interconnected networks, while overproduction of Dnm1 results in excessive mitochondrial fragmentation. In the current model, Dnm1 is essentially a GTP hydrolysis-driven molecular motor that self-assembles into ring-like oligomeric structures that encircle and pinch the outer mitochondrial membrane at sites of fission...
November 22, 2017: ACS Central Science
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