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Membrane fusion

Hung-Lun Hsu, Jean K Millet, Deirdre A Costello, Gary R Whittaker, Susan Daniel
Virus pseudotyping is a useful and safe technique for studying entry of emerging strains of influenza virus. However, few studies have compared different reassortant combinations in pseudoparticle systems, or compared entry kinetics of native viruses and their pseudotyped analogs. Here, vesicular stomatitis virus (VSV)-based pseudovirions displaying distinct influenza virus envelope proteins were tested for fusion activity. We produced VSV pseudotypes containing the prototypical X-31 (H3) HA, either alone or with strain-matched or mismatched N2 NAs...
October 18, 2016: Scientific Reports
Jia Shi, Jian-Bo Yu, Wei Liu, Dan Wang, Yuan Zhang, Li-Rong Gong, Shu-An Dong, Da-Quan Liu
Acute respiratory distress syndrome (ARDS) is one of the most devastating complications of sepsis lacking of effective therapy. Mitochondrial dynamics undergoing continuous fusion and fission play a crucial role in mitochondrial structure and function. Fis1, as a small protein located on the outer membrane of mitochondria, has been thought to be an important protein mediated mitochondrial fission. During ARDS, alveolar macrophages suffer from increased oxidative stress and apoptosis, and also accompanied by disrupted mitochondrial dynamics...
October 14, 2016: Experimental Cell Research
Jovan Nikolic, Ahmet Civas, Zoé Lama, Cécile Lagaudrière-Gesbert, Danielle Blondel
Stress granules (SGs) are membrane-less dynamic structures consisting of mRNA and protein aggregates that form rapidly in response to a wide range of environmental cellular stresses and viral infections. They act as storage sites for translationally silenced mRNAs under stress conditions. During viral infection, SG formation results in the modulation of innate antiviral immune responses, and several viruses have the ability to either promote or prevent SG assembly. Here, we show that rabies virus (RABV) induces SG formation in infected cells, as revealed by the detection of SG-marker proteins Ras GTPase-activating protein-binding protein 1 (G3BP1), T-cell intracellular antigen 1 (TIA-1) and poly(A)-binding protein (PABP) in the RNA granules formed during viral infection...
October 2016: PLoS Pathogens
Dario Vazquez-Albacete, Ana Mafalda Cavaleiro, Ulla Christensen, Susanna Seppälä, Birger Lindberg Møller, Morten H H Nørholm
Membrane-associated Cytochromes P450 (P450s) are one of the most important enzyme families for biosynthesis of plant-derived medicinal compounds. However, the hydrophobic nature of P450s makes their use in robust cell factories a challenge. Here we explore a small library of N-terminal expression tag chimeras of the model plant P450 CYP79A1 in different Escherichia coli strains. Using a high-throughput screening platform based on C-terminal GFP fusions, we identify several highly expressing and robustly performing chimeric designs...
October 17, 2016: Biotechnology and Bioengineering
Huan-Yuan Chen, Dapi Meng-Lin Chiang, Zi-Jing Lin, Chia-Chun Hsieh, Gung-Chian Yin, I-Chun Weng, Peter Guttermann, Stephan Werner, Katja Henzler, Gerd Schneider, Lee-Jene Lai, Fu-Tong Liu
Mast cells play an important role in allergic responses. During activation, these cells undergo degranulation, a process by which various kinds of mediators stored in the granules are released. Granule homeostasis in mast cells has mainly been studied by electron microscopy (EM), where the fine structures of subcellular organelles are partially destroyed during sample preparation. Migration and fusion of granules have not been studied in detail in three dimensions (3D) in unmodified samples. Here, we utilized soft X-ray tomography (SXT) coupled with fluorescence microscopy to study the detailed structures of organelles during mast cell activation...
October 17, 2016: Scientific Reports
Alexandros Koutsioubas
Supported lipid bilayers on planar surfaces constitute an archetypical experimental system for the study of biological membranes. The popularity of these ordered molecular layers in the literature, is on one hand related to the simplicity of their preparation using the method of vesicle fusion and on the other hand to their compatibility with a multitude of surface sensitive experimental probes. Neutron reflectivity has proven as an important experimental method for the investigation of such systems with the ability to provide sub-nanometer structural information perpendicular to the supporting plane...
October 17, 2016: Journal of Physical Chemistry. B
Adam Kawałek, Chandhuru Jagadeesan, Ida J van der Klei
The non-bilayer forming lipids cardiolipin (CL) and phosphatidylethanolamine (PE) modulate membrane curvature, facilitate membrane fusion and affect the stability and function of membrane proteins. Yeast peroxisomal membranes contain significant amounts of CL and PE. We analysed the effect of CL deficiency and PE depletion on peroxisome biogenesis and proliferation in Saccharomyces cerevisiae. Our data indicate that deletion of CRD1, which encodes cardiolipin synthase, does not affect peroxisome biogenesis or abundance, both at peroxisome repressing (glucose) or inducing (oleate) growth conditions...
October 13, 2016: Biochemical and Biophysical Research Communications
Z Schultzhaus, T B Johnson, B D Shaw
Cell growth necessitates extensive membrane remodeling events including vesicle fusion or fission, processes that are regulated by coat proteins. The hyphal cells of filamentous fungi concentrate both exocytosis and endocytosis at the apex. This investigation focuses on clathrin in Aspergillus nidulans, with the aim of understanding its role in membrane remodeling in growing hyphae. We examined clathrin heavy chain (ClaH-GFP) which localized to three distinct subcellular structures: late Golgi (trans-Golgi equivalents of filamentous fungi), which are concentrated just behind the hyphal tip but are intermittently present throughout all hyphal cells; the region of concentrated endocytosis just behind the hyphal apex (the "endocytic collar"); and small, rapidly moving puncta that were seen trafficking long distances in nearly all hyphal compartments...
October 14, 2016: Molecular Microbiology
Tiziano Gaiotto, Simon E Hufton
Cross-neutralising monoclonal antibodies against influenza hemagglutinin (HA) are of considerable interest as both therapeutics and diagnostic tools. We have recently described five different single domain antibodies (nanobodies) which share this cross-neutralising activity and suggest their small size, high stability, and cleft binding properties may present distinct advantages over equivalent conventional antibodies. We have used yeast display in combination with deep mutational scanning to give residue level resolution of positions in the antibody-HA interface which are crucial for binding...
2016: PloS One
Yangdong Sun, Qiao Ye, Min Wu, Yonghong Wu, Chenggang Zhang, Weiqun Yan
This study aimed to validate the high yield and soluble expression of proteins carrying the transactivator of transcription (Tat) peptide tag, and further explored the potential mechanism by which the Tat tag increases expression. Escherichia coli superoxide dismutase (SOD) proteins, including SodA, SodB and SodC, were selected for analysis. As expected, the yields and the solubility of Tat-tagged proteins were higher than those of Tat-free proteins, and similar results were observed for the total SOD enzyme activity...
October 14, 2016: Experimental & Molecular Medicine
C M Wong, L A Nash, J Del Papa, K L Poulin, T Falls, J C Bell, R J Parks
When injected directly into a tumor mass, adenovirus (Ad) vectors only transduce cells immediately along the injection tract. Expression of fusogenic proteins from the Ad vector can lead to syncytium formation, which efficiently spreads the therapeutic effect. Fusogenic proteins can also cause cancer cell death directly, and enhance the release of exosome-like particles containing tumor-associated antigens, which boosts the anti-tumor immune response. In this study, we have examined whether delivery of an early region 1 (E1)-deleted, replication-defective Ad vector encoding the reptilian reovirus p14 fusion-associated small transmembrane (FAST) protein can provide therapeutic efficacy in an immunocompetent mouse tumor model...
October 14, 2016: Cancer Gene Therapy
Yuantai Wu, Mehmet Takar, Andrea A Cuentas-Condori, Todd R Graham
NEO1 is an essential gene in budding yeast and belongs to a highly conserved subfamily of P-type ATPase genes that encode phospholipid flippases. Inactivation of temperature sensitive neo1(ts) alleles produces pleiomorphic defects in the secretory and endocytic pathways, including fragmented vacuoles. A screen for multicopy suppressors of neo1-2(ts) growth defects yielded YPT7, which encodes a Rab7 homolog involved in SNARE-dependent vacuolar fusion. YPT7 suppressed the vacuole fragmentation phenotype of neo1-2, but did not suppress Golgi-associated protein trafficking defects...
July 2016: Cellular Logistics
Maarten Danial, Angela Stauffer, Frederik R Wurm, Michael J Root, Harm-Anton Klok
A popular strategy to overcome the limited plasma half-life of peptide heptad repeat 2 (HR2) fusion inhibitors against HIV-1 is through conjugation with biocompatible polymers such as poly(ethylene glycol) (PEG). However, despite improved resistance to proteolysis and reduced renal elimination, covalent attachment of polymers often causes a loss in therapeutic potency. In this study, we investigated the molecular origins of the loss in potency upon conjugation of linear, mid-functional and hyperbranched PEG-like polymers to peptides that inhibit HIV-1 - host cell membrane fusion...
October 13, 2016: Bioconjugate Chemistry
Shuting Xu, Aurélie Ducroux, Aparna Ponnurangam, Gabrielle Vieyres, Sergej Franz, Mathias Müsken, Thomas Zillinger, Angelina Malassa, Ellen Ewald, Veit Hornung, Winfried Barchet, Susanne Häussler, Thomas Pietschmann, Christine Goffinet
Upon sensing cytoplasmic retroviral DNA in infected cells, cyclic GMP-AMP (cGAMP) synthase (cGAS) produces the cyclic dinucleotide cGAMP, which activates STING to trigger a type I interferon (IFN) response. We find that membrane fusion-inducing contact between donor cells expressing the HIV envelope (Env) and primary macrophages endogenously expressing the HIV receptor CD4 and coreceptor enable intercellular transfer of cGAMP. This cGAMP exchange results in STING-dependent antiviral IFN responses in target macrophages and protection from HIV infection...
October 12, 2016: Cell Host & Microbe
J Zhang, Y Wang, H Guo, Z Mao, C Ge
Pseudomonas plecoglossicida NB2011, the causative agent of visceral granulomas disease in farmed Larimichthys crocea in China, encodes a predicted type three effector PP_ExoU, a homolog of the cytotoxin ExoU of Pseudomonas aeruginosa. In this study, secretion of PP_ExoU was tested in various broth, the protein was expressed with the pET30a prokaryotic system, the phospholipase A (PLA) activity of the recombinant protein was determined with fluorogenic phospholipid substrates, fusion expression with green fluorescent protein in transfected HeLa cells was investigated, and the lactate dehydrogenase (LDH) level was measured...
October 13, 2016: Journal of Fish Diseases
Zifan Gong, Mackenzie T Walls, Alisha N Karley, Amy J Karlsson
Cell-penetrating peptides (CPPs) are a class of small peptides that are able to cross cell membranes via direct translocation or endocytosis. They have been widely used to deliver tethered bioactive molecules to cells, but recombinantly producing CPPs as fusions to protein cargo leads to low yields. We used Escherichia coli cells to recombinantly produce genetic fusions of NPFSD (derived from a yeast endocytosis signal) and pVEC (derived from a murine vascular endothelium cadherin) to the N-terminus of green fluorescent protein (GFP) with and without a flexible glycine-serine linker between the CPP and GFP...
October 12, 2016: Molecular Biotechnology
T N Figueira, L M Palermo, A S Veiga, D Huey, C A Alabi, N C Santos, J C Welsch, C Mathieu, B Horvat, S Niewiesk, A Moscona, M A R B Castanho, M Porotto
: Measles virus (MV) infection is undergoing resurgence and remains one of the leading causes of death among young children worldwide despite the availability of an effective measles vaccine. MV infects its target cells by coordinated action of the MV hemagglutinin (H) and fusion (F) envelope glycoproteins; upon receptor engagement by H, the pre-fusion F undergoes a structural transition, extending and inserting into the target cell membrane and then re-folding into a post-fusion structure that fuses the viral and cell membranes...
October 12, 2016: Journal of Virology
Kazuya Shirato, Kazuhiko Kanou, Miyuki Kawase, Shutoku Matsuyama
: Human coronavirus 229E (HCoV-229E), a causative agent of the common cold, enters host cells via two distinct pathways: one is mediated by cell surface proteases, particularly transmembrane protease serine 2 (TMPRSS2), and the other by endosomal cathepsin L. Thus, specific inhibitors of these proteases block virus infection. However, it is unclear which of these pathways is actually utilized by HCoV-229E in the human respiratory tract. Here, we examined the mechanism of cell entry used by a pseudotyped virus bearing the HCoV-229E spike (S) protein in the presence/absence of protease inhibitors...
October 12, 2016: Journal of Virology
Paulo S Pinheiro, Sébastien Houy, Jakob B Sørensen
The molecular mechanisms for calcium-triggered membrane fusion have long been sought for, and detailed models now exist that account for at least some of the functions of the many proteins involved in the process. Key players in the fusion reaction are a group of proteins that, upon binding to calcium, trigger the merger of cargo-filled vesicles with the plasma membrane. Low-affinity, fast-kinetics calcium sensors of the synaptotagmin family - especially synaptotagmin-1 and synaptotagmin-2 - are the main calcium sensors for fast exocytosis triggering in many cell types...
October 12, 2016: Journal of Neurochemistry
Saghi Sepehri, Lotfollah Saghaie, Afshin Fassihi
The fusion of viral and host cell membranes is mediated using gp41 subunit of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein. As the HIV-1 enters the host cells, the two helical regions (HR1 and HR2) in the ectodomain of gp41 form a six-helix bundle, which carries the target and viral cell membranes to close proximity. Steps of this process serve as attractive targets for developing HIV-1 fusion inhibitors. Identification of some novel HIV fusion inhibitors with the goal of blocking the formation of the six-helix bundle was accomplished by computer-aided drug design techniques...
October 12, 2016: Molecular Informatics
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