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Articles de revues sur le sujet "Protein Mediated Membrane Fusion"
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Stegmann, T., R. W. Doms et A. Helenius. « Protein-Mediated Membrane Fusion ». Annual Review of Biophysics and Biophysical Chemistry 18, no 1 (juin 1989) : 187–211. http://dx.doi.org/10.1146/annurev.bb.18.060189.001155.
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Benhaim, Mark A., et Kelly K. Lee. « New Biophysical Approaches Reveal the Dynamics and Mechanics of Type I Viral Fusion Machinery and Their Interplay with Membranes ». Viruses 12, no 4 (8 avril 2020) : 413. http://dx.doi.org/10.3390/v12040413.
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Protein-mediated membrane fusion is a highly regulated biological process essential for cellular and organismal functions and infection by enveloped viruses. During viral entry the membrane fusion reaction is catalyzed by specialized protein machinery on the viral surface. These viral fusion proteins undergo a series of dramatic structural changes during membrane fusion where they engage, remodel, and ultimately fuse with the host membrane. The structural and dynamic nature of these conformational changes and their impact on the membranes have long-eluded characterization. Recent advances in structural and biophysical methodologies have enabled researchers to directly observe viral fusion proteins as they carry out their functions during membrane fusion. Here we review the structure and function of type I viral fusion proteins and mechanisms of protein-mediated membrane fusion. We highlight how recent technological advances and new biophysical approaches are providing unprecedented new insight into the membrane fusion reaction.
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Boonstra, Sander, Jelle S. Blijleven, Wouter H. Roos, Patrick R. Onck, Erik van der Giessen et Antoine M. van Oijen. « Hemagglutinin-Mediated Membrane Fusion : A Biophysical Perspective ». Annual Review of Biophysics 47, no 1 (20 mai 2018) : 153–73. http://dx.doi.org/10.1146/annurev-biophys-070317-033018.
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Influenza hemagglutinin (HA) is a viral membrane protein responsible for the initial steps of the entry of influenza virus into the host cell. It mediates binding of the virus particle to the host-cell membrane and catalyzes fusion of the viral membrane with that of the host. HA is therefore a major target in the development of antiviral strategies. The fusion of two membranes involves high activation barriers and proceeds through several intermediate states. Here, we provide a biophysical description of the membrane fusion process, relating its kinetic and thermodynamic properties to the large conformational changes taking place in HA and placing these in the context of multiple HA proteins working together to mediate fusion. Furthermore, we highlight the role of novel single-particle experiments and computational approaches in understanding the fusion process and their complementarity with other biophysical approaches.
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Kumar, Pawan, Samit Guha et Ulf Diederichsen. « SNARE protein analog-mediated membrane fusion ». Journal of Peptide Science 21, no 8 (7 avril 2015) : 621–29. http://dx.doi.org/10.1002/psc.2773.
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Stiasny, Karin, et Franz X. Heinz. « Flavivirus membrane fusion ». Journal of General Virology 87, no 10 (1 octobre 2006) : 2755–66. http://dx.doi.org/10.1099/vir.0.82210-0.
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Flavivirus membrane fusion is mediated by a class II viral fusion protein, the major envelope protein E, and the fusion process is extremely fast and efficient. Understanding of the underlying mechanisms has been advanced significantly by the determination of E protein structures in their pre- and post-fusion conformations and by the elucidation of the quarternary organization of E proteins in the viral envelope. In this review, these structural data are discussed in the context of functional and biochemical analyses of the flavivirus fusion mechanism and its characteristics are compared with those of other class II- and class I-driven fusion processes.
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Fu, Jiawen, Lin Zhao, Juan Yang, Heming Chen, Shinuo Cao et Honglin Jia. « An unconventional SNARE complex mediates exocytosis at the plasma membrane and vesicular fusion at the apical annuli in Toxoplasma gondii ». PLOS Pathogens 19, no 3 (27 mars 2023) : e1011288. http://dx.doi.org/10.1371/journal.ppat.1011288.
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Exocytosis is a key active process in cells by which proteins are released in bulk via the fusion of exocytic vesicles with the plasma membrane. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein-mediated vesicle fusion with the plasma membrane is essential in most exocytotic pathways. In mammalian cells, the vesicular fusion step of exocytosis is normally mediated by Syntaxin-1 (Stx1) and SNAP25 family proteins (SNAP25 and SNAP23). However, in Toxoplasma gondii, a model organism of Apicomplexa, the only SNAP25 family protein, with a SNAP29-like molecular structure, is involved in vesicular fusion at the apicoplast. Here, we reveal that an unconventional SNARE complex comprising TgStx1, TgStx20, and TgStx21 mediates vesicular fusion at the plasma membrane. This complex is essential for the exocytosis of surface proteins and vesicular fusion at the apical annuli in T. gondii.
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Taylor, Gwen M., et David Avram Sanders. « The Role of the Membrane-spanning Domain Sequence in Glycoprotein-mediated Membrane Fusion ». Molecular Biology of the Cell 10, no 9 (septembre 1999) : 2803–15. http://dx.doi.org/10.1091/mbc.10.9.2803.
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The role of glycoprotein membrane-spanning domains in the process of membrane fusion is poorly understood. It has been demonstrated that replacing all or part of the membrane-spanning domain of a viral fusion protein with sequences that encode signals for glycosylphosphatidylinositol linkage attachment abrogates membrane fusion activity. It has been suggested, however, that the actual amino acid sequence of the membrane-spanning domain is not critical for the activity of viral fusion proteins. We have examined the function of Moloney murine leukemia virus envelope proteins with substitutions in the membrane-spanning domain. Envelope proteins bearing substitutions for proline 617 are processed and incorporated into virus particles normally and bind to the viral receptor. However, they possess greatly reduced or undetectable capacities for the promotion of membrane fusion and infectious virus particle formation. Our results imply a direct role for the residues in the membrane-spanning domain of the murine leukemia virus envelope protein in membrane fusion and its regulation. They also support the thesis that membrane-spanning domains possess a sequence-dependent function in other protein-mediated membrane fusion events.
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Johnson, Colin P., et Edwin R. Chapman. « Otoferlin is a calcium sensor that directly regulates SNARE-mediated membrane fusion ». Journal of Cell Biology 191, no 1 (4 octobre 2010) : 187–97. http://dx.doi.org/10.1083/jcb.201002089.
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Otoferlin is a large multi–C2 domain protein proposed to act as a calcium sensor that regulates synaptic vesicle exocytosis in cochlear hair cells. Although mutations in otoferlin have been associated with deafness, its contribution to neurotransmitter release is unresolved. Using recombinant proteins, we demonstrate that five of the six C2 domains of otoferlin sense calcium with apparent dissociation constants that ranged from 13–25 µM; in the presence of membranes, these apparent affinities increase by up to sevenfold. Using a reconstituted membrane fusion assay, we found that five of the six C2 domains of otoferlin stimulate membrane fusion in a calcium-dependent manner. We also demonstrate that a calcium binding–deficient form of the C2C domain is incapable of stimulating membrane fusion, further underscoring the importance of calcium for the protein’s function. These results demonstrate for the first time that otoferlin is a calcium sensor that can directly regulate soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor–mediated membrane fusion reactions.
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Kingsley, David H., Ali Behbahani, Afshin Rashtian, Gary W. Blissard et Joshua Zimmerberg. « A Discrete Stage of Baculovirus GP64-mediated Membrane Fusion ». Molecular Biology of the Cell 10, no 12 (décembre 1999) : 4191–200. http://dx.doi.org/10.1091/mbc.10.12.4191.
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Viral fusion protein trimers can play a critical role in limiting lipids in membrane fusion. Because the trimeric oligomer of many viral fusion proteins is often stabilized by hydrophobic 4-3 heptad repeats, higher-order oligomers might be stabilized by similar sequences. There is a hydrophobic 4-3 heptad repeat contiguous to a putative oligomerization domain of Autographa californica multicapsid nucleopolyhedrovirus envelope glycoprotein GP64. We performed mutagenesis and peptide inhibition studies to determine if this sequence might play a role in catalysis of membrane fusion. First, leucine-to-alanine mutants within and flanking the amino terminus of the hydrophobic 4-3 heptad repeat motif that oligomerize into trimers and traffic to insect Sf9 cell surfaces were identified. These mutants retained their wild-type conformation at neutral pH and changed conformation in acidic conditions, as judged by the reactivity of a conformationally sensitive mAb. These mutants, however, were defective for membrane fusion. Second, a peptide encoding the portion flanking the GP64 hydrophobic 4-3 heptad repeat was synthesized. Adding peptide led to inhibition of membrane fusion, which occurred only when the peptide was present during low pH application. The presence of peptide during low pH application did not prevent low pH–induced conformational changes, as determined by the loss of a conformationally sensitive epitope. In control experiments, a peptide of identical composition but different sequence, or a peptide encoding a portion of the Ebola GP heptad motif, had no effect on GP64-mediated fusion. Furthermore, when the hemagglutinin (X31 strain) fusion protein of influenza was functionally expressed in Sf9 cells, no effect on hemagglutinin-mediated fusion was observed, suggesting that the peptide does not exert nonspecific effects on other fusion proteins or cell membranes. Collectively, these studies suggest that the specific peptide sequences of GP64 that are adjacent to and include portions of the hydrophobic 4-3 heptad repeat play a dynamic role in membrane fusion at a stage that is downstream of the initiation of protein conformational changes but upstream of lipid mixing.
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Grothe, Tobias, Julia Nowak, Reinhard Jahn et Peter Jomo Walla. « Selected tools to visualize membrane interactions ». European Biophysics Journal 50, no 2 (mars 2021) : 211–22. http://dx.doi.org/10.1007/s00249-021-01516-6.
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AbstractIn the past decade, we developed various fluorescence-based methods for monitoring membrane fusion, membrane docking, distances between membranes, and membrane curvature. These tools were mainly developed using liposomes as model systems, which allows for the dissection of specific interactions mediated by, for example, fusion proteins. Here, we provide an overview of these methods, including two-photon fluorescence cross-correlation spectroscopy and intramembrane Förster energy transfer, with asymmetric labelling of inner and outer membrane leaflets and the calibrated use of transmembrane energy transfer to determine membrane distances below 10 nm. We discuss their application range and their limitations using examples from our work on protein-mediated vesicle docking and fusion.
Thèses sur le sujet "Protein Mediated Membrane Fusion"
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Howard, Megan Wilder. « Coronavirus mediated membrane fusion / ». Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2008. http://proquest.umi.com/pqdweb?did=1552538711&sid=1&Fmt=6&clientId=18952&RQT=309&VName=PQD.
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Thesis (Ph.D. in Microbiology) -- University of Colorado Denver, 2008.Typescript. Includes bibliographical references (leaves 161-183). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;
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Mair, Caroline. « Membrane fusion mediated by the influenza virus hemagglutinin ». Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17217.
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Der Eintritt von Influenza A Viren in Wirtszellen erfolgt anhand des Hämagglutinin (HA) Proteins. Neueste Entwicklungen zielen darauf ab, die fusionsinduzierende Konformations-änderung des HA und damit die Freisetzung des viralen Genoms in die Wirtszelle zu inhibieren. Der Fusionsprozess ist pH-abhängig da nur bei einem niedrigen pH-Wert (~5.0-6.0) die Protonierung bestimmter Reste innerhalb des HA eine Konformationsänderung, und somit die Membranfusion, auslöst. Die Identifizierung von konservierten, titrierbaren Resten und die Aufklärung der Strukturveränderungen im HA ermöglichen eine gezielte Entwicklung neuer antiviraler Medikamente. In dieser Arbeit wurden bestimmte Histidine im HA mittels umfassender experimenteller und theoretischer Methoden als potentielle pH-Sensoren untersucht. Dabei konnte das Histidin an Position 184 als wichtiger Schalter der pH-induzierten Konformationsänderung identifiziert werden. Außerdem bewirkte der Austausch des geladenen Rests an Position 216 in der Nähe des His184 eine Veränderung der pH-Abhängigkeit des H5 HA aufgrund der Beeinflussung des pKa-Werts des His184. Da die Mutation R216E im HA des hochpathogenen H5N1 Virus in allen Isolaten während der Vogelvirenseuche im Jahr 2003/04 detektiert wurde, deutet das Ergebnis daraufhin, dass diese Mutation zur Entstehung des hochvirulenten Vogelvirus und dessen Adaptierung an den Menschen beigetragen hat. In diesem Zusammenhang wurde auch der Einfluss der pH-Abhängigkeit des HA auf die Fusion und Infektiosität von Viren in lebenden Zellen getestet. Eine destabilisierende Mutation im HA eines rekombinanten WSN-H3 Virus reduzierte dessen Infektions- und Replikationseffizienz in MDCK-Zellen, was auf den endosomalen pH-Wert dieser Zellen zurückgeführt werden konnte. Die Messung der Virus-Endosom-Fusionskinetik in lebenden Zellen machte außerdem die Bedeutung der pH-Abhängigkeit des HA für den Zeitpunkt der Membranfusion und dessen Einfluss auf die Effizienz der Virusinfektion deutlich.The entry of influenza A virus into host cells is established by the hemagglutinin (HA) protein. New antiviral strategies aim to inhibit the fusion inducing conformational change of HA and thereby liberation of the viral genome into the cell. This process is strictly pH dependent since the conformational change of HA initiating the fusion of membranes only occurs upon protonation of yet unknown residues within HA at low pH (~5.0-6.0). The identification of conserved titrable residues and better understanding of the sequential structural rearrangements within HA may facilitate the development of new broad-spectrum antivirals. In the present work His184 and His110 were characterized as potential pH sensors by a comprehensive mutational and computational analysis. The results suggest that His184, but not His110, is an important regulator of HA conformational change at low pH. Furthermore, an exchange of charge at position 216 in vicinity to His184 was shown to alter the pH dependence of conformational change and of fusion in correlation to the known pKa dependence of histidines on neighboring residues. The result advocates that the mutation R216E, which emerged in the highly pathogenic H5 HA in 2003-2004, contributed to an altered acid stability of H5 HA via its effect on His184 and thus to the adaptation of avian H5N1 viruses to the human host. Therefore, the role of an altered acid stability of HA for viral fusion and infectivity in living cells was assessed. Recombinant viruses containing a destabilizing mutation in the HA protein were found to have a reduced infectivity and replication efficiency in MDCK cells compared to the respective wild type. Studying virus-endosome fusion kinetics in these cells we could resolve a significant difference in the timing of fusion induction suggesting that the time-point of fusion is a critical determinant of viral infection efficiency which depends on the endosomal acidification as well as on the acid stability of HA.
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Liu, Tina Yu. « Mechanism of endoplasmic reticulum membrane fusion mediated by the Atlastin GTPase ». Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13064987.
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How organelles acquire their unique shapes is a fundamental question of cell biology. The peripheral endoplasmic reticulum (ER) consists of a vast network of membrane sheets and tubules, the formation of which requires homotypic membrane fusion. Previous studies suggest that the dynamin-like GTPase, atlastin (ATL), mediates ER fusion, but the mechanism by which this occurs is unclear. In this study, I investigate 1) the role of dimerization and conformational changes in the N-terminal domain of ATL, 2) how the C-terminal amphipathic helix and the transmembrane domain of ATL cooperate with the N-terminal domain, and 3) the formation of cis and trans ATL dimers in the fusion mechanism.
ATL has a cytosolic N-terminal domain, consisting of a GTPase domain and three-helix bundle (3HB), followed by two transmembrane segments (TMs) and a cytosolic C-terminal tail (CT). Crystal structures of ATL and biochemical experiments suggest that nucleotide-dependent dimerization between ATL molecules sitting in different membranes can tether the membranes together. A subsequent conformational change triggered by GTP hydrolysis could pull the membranes toward one another for fusion. This mechanism is supported by in vitro membrane tethering and fusion assays using vesicles containing full-length Drosophila ATL.
The CT and TMs of ATL are also required for efficient membrane fusion. A synthetic peptide corresponding to a conserved amphipathic helix in the CT can act in trans to restore the fusion activity of a tailless ATL mutant. We characterize CT mutants to show that the C-terminal helix promotes fusion by perturbing the lipid bilayer. The TMs of ATL also mediate nucleotide-independent oligomerization, which may allow ATL molecules in the same membrane to synchronously undergo the conformational change leading to fusion.
Lastly, we show that continuous GTP hydrolysis is required for membrane tethering, occasionally resulting in fusion. The N-terminal cytosolic domain mediates trans dimer formation between ATL molecules on different membranes. GTP binding induces dimerization through the GTPase domains and 3HBs. We propose that GTP hydrolysis and phosphate release are required not just to drive fusion, but also to dissociate cis dimers that form on the same membrane, thus allowing ATL molecules to form trans dimers.
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Stone-Hulslander, Judith. « Mechanisms of Newcastle Disease Virus-Mediated Membrane Fusion : A Dissertation ». eScholarship@UMMS, 1999. https://escholarship.umassmed.edu/gsbs_diss/131.
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For many paramyxoviruses, including Newcastle disease virus (NDV), syncytia formation requires the expression of both surface glycoproteins (HN and F) in the same cell, and evidence suggests that fusion involves a specific interaction between the HN and F proteins (23, 73). Because a potential interaction in paramyxovirus infected cells has never been clearly demonstrated, such an interaction was explored in Chapter 2 using coimmunoprecipitation and crosslinking. Both HN and F proteins could be precipitated with heterologous antisera after a five minute radioactive pulse as well as after a two hour chase in non-radioactive media, but at low levels. Chemical crosslinking increased detection of complexes containing HN and F proteins at the cell surface. After crosslinking, intermediate as well as high molecular weight species containing both proteins were precipitated with monospecific antisera. Precipitation of proteins with anti-HN after crosslinking resulted in the detection of complexes which electrophoresed in the stacker region of the gel, from 160-300 kD, at 150 kD and at 74 kD. Precipitates obtained with anti-F after crosslinking contained species which migrated in the stacker region of the gel, between 160-300 kD, at 120 kD and at 66 kD. The 3-4 discrete complexes ranging in size from 160-300 kD contained both HN and F proteins when precipitated with either HN or F antisera. That crosslinking of complexes containing both HN and F proteins was not simply a function of overexpression of viral glycoproteins at the cell surface was addressed by demonstrating crosslinking at early time points post infection, when levels of viral surface glycoproteins are low. Use of cells infected with an avirulent strain of NDV showed that chemically crosslinked HN and F proteins were precipitated independent of cleavage of F0. Furthermore, under conditions that maximized HN protein binding to its receptor, there was no change in the percentages of HN and F0 proteins precipitated with heterologous antisera, but a decrease in F1protein precipitated was observed upon attachment. These data argue that the HN and F proteins interact in the RER. Upon attachment of the HN protein to its receptor, the HN protein undergoes a conformational change which causes a subsequent change in the associated F protein, releasing the hydrophobic fusion peptide into the target membrane and initiating fusion.
Chapter 3 explores the stalk region of the NDV HN protein, which has been implicated in both fusion promotion and virus specificity of that activity. The NDV F protein contains two heptad repeat motifs which have been shown by site-directed mutagenesis to be critical for fusion (7, 51, 57). Heptad repeat motifs mediate protein-protein interactions by enabling the formation of coiled-coils. Upon analysis of the stalk region of the NDV HN protein, we identified two heptad repeats. Secondary structure analysis of these repeats suggested the potential for these regions to form alpha-helices. To investigate the importance of this sequence motif for fusion promotion, we mutated the hydrophobic "a" position amino acids of each heptad repeat to alanine or methionine. In addition, hydrophobic amino acids in other positions were also changed to alanine. Every mutant protein retained levels of attachment activity that was greater than or equal to the wild-type protein and bound to conformation-specific monoclonal as well as polyclonal antisera. Neuraminidase activity was variably affected. Every mutation, however, showed a dramatic decrease in fusion promotion activity. The phenotypes of these mutant proteins indicate that individual amino acids within the heptad repeat region of the stalk domain of the HN protein are important for the fusion promotion activity of the protein. These data are consistent with the idea that the HN protein associates with the F protein via specific interactions between the heptad repeat regions of both proteins.
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Atfield, Rachel Sarah. « Herpes simplex virus glycoprotein-mediated membrane fusion ». Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615860.
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Chen, Yong. « Structural and functional studies on SNAREs-mediated membrane fusion ». [Ames, Iowa : Iowa State University], 2006.
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Lu, Xiaobing. « Studies of intermediates and regulation in SNARE-mediated membrane fusion ». [Ames, Iowa : Iowa State University], 2008.
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Abdulreda, Midhat H. « Investigation of Snare-Mediated Membrane Fusion Mechanism Using Atomic Force Microscope Spectroscopy ». Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_dissertations/55.
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Membrane fusion is essential for survival in eukaryotic cells. Many physiological processes such as endocytosis and exocytosis are mediated by membrane fusion, which is driven by highly specialized and conserved family of proteins. Neuronal soluble Nethylmaleimide- sensitive factor attachment protein receptors (SNAREs) mediate vesicle fusion with the plasma membrane during neurotransmitter release; however, the mechanism for SNARE-mediated membrane fusion remains to be established. In the current work, we aimed at investigating this mechanism using atomic force microscope (AFM) spectroscopy. We established an AFM lipid bilayer system, which proved effective in detecting fusion of bilayers and measuring compression forces required to generate fusion. It also revealed that SNARE-mediated membrane fusion proceeds through an intermediate hemifused state. Using this system, we revealed the energy landscape for membrane fusion using a dynamic force approach. We carried out compression force measurements at different compression rates and a significant reduction in the force was observed when SNAREs were present in the bilayers. The results also indicated that a single energy barrier governed membrane fusion in our experimental system. The energy barrier is characterized by its width and height, which determine the slope of the activation potential. With SNAREs in the opposing (trans) bilayers, the width of the barrier increased > 2 fold, which is interpreted as an increase in the compressibility of the membranes and subsequently a greater ease in their deformation and fusion under compression. Moreover, specific perturbations to the SNARE interaction interfered with the observed facilitation of membrane fusion, which indicated the involvement of SNAREs in the observed fusion facilitation and increase in the fusion rate. Furthermore, dissociation kinetics analysis of the SNARE interaction revealed a strong binding force during trans SNARE-complex formation, and a correlation between the strength of the SNARE interaction and the degree of fusion facilitation was established. In conclusion, the present findings provide support for a mechanism for SNAREmediated membrane fusion, where trans-interaction between SNAREs provides close apposition of the membranes and reduces fusion energy requirements by locally destabilizing the bilayers, in which the SNAREs are anchored, through pulling on or tilting of their transmembrane segments.
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Webb, Stacy. « Viral Fusion Protein TM-TM Interactions : Modulators of Protein Function and Potential Antiviral Targets ». UKnowledge, 2017. http://uknowledge.uky.edu/biochem_etds/30.
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Enveloped viruses, such as HIV, influenza, and Ebola, utilize surface glycoproteins to bind and fuse with a target cell membrane. This fusion event is necessary for release of viral genomic material so the virus can ultimately reproduce and spread. The recently emerged Hendra virus (HeV) is a negative-sense, single-stranded RNA paramyxovirus that presents a considerable threat to human health as there are currently no human vaccines or antivirals available. The HeV utilizes two surface glycoproteins, the fusion protein (F) and the attachment protein (G), to drive membrane fusion. Through this process, the F protein undergoes an irreversible conformational change, transitioning from a meta-stable pre-fusion conformation to a more thermodynamically stable post-fusion structure. Understanding the elements which control stability of the pre-fusion state and triggering to the post-fusion conformation is important for understanding F protein function. Studies that replace or mutate the TM domain of the F protein of several viruses implicated the TM domain in the fusion process, but the structural and molecular details in fusion remain unclear. Previously, analytical ultracentrifugation was used to demonstrate that isolated TM domains of HeV F protein associate in a monomer-trimer equilibrium. To determine factors driving this association, we analyzed the sequence of several paramyxovirus F protein TM domains and found a heptad repeat of β-branched residues. Analysis of the HeV F TM domain specifically revealed a heptad repeat leucine-isoleucine zipper motif (LIZ). Replacement of the LIZ with alanine resulted in dramatically reduced TM-TM association. Mutation of the LIZ in the whole protein resulted in decreased protein expression and pre-fusion conformation. To further understand the role of the TM domain, the TM domain was targeted as a potential modulator of F protein stability and function. Exogenous HeV F TM constructs were co-expressed with the full length F protein in Vero cells to analyze the effects on protein expression. Co-expression of the exogenous HeV F TM constructs dramatically reduced the expression of HeV F. However, the co-expression of exogenous HeV F TM constructs with a different paramyxovirus F protein, PIV5 F, did not strongly affect PIV5 F expression levels, suggesting that the interaction of the exogenous TM constructs is specific. Fusion assays revealed that HeV F TM constructs dramatically reduced HeV F, but not PIV5 F fusion activity. We hypothesize that the short exogenous HeV TM constructs associate with the TM domain from full-length HeV F, resulting in pre-mature triggering or protein misfolding. The work presented here demonstrates that specific elements in the TM domain contribute to TM association and pre-fusion protein stability. Furthermore, targeting these interactions may be a viable approach for antiviral development against this important pathogen.
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Kuwana, Tomomi. « Characterisation of a lysosomal protein that interfrers with membrane fusion assays ». Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337875.
Texte intégralLivres sur le sujet "Protein Mediated Membrane Fusion"
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Alcott, Brett Eugene. Nanoscale Electrical and Coarse-grained Molecular Dynamics Studies of Influenza Hemagglutinin-mediated Membrane Fusion Pores. [New York, N.Y.?] : [publisher not identified], 2017.
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Bilimoria, Darius M. Studies involving measles virus receptor interaction and inhibitors of virus mediated membrane fusion (a prelude to a small animal model and antiviral agents directed). Ottawa : National Library of Canada, 1998.
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Baciu, Cristina Luminita. Advances in the investigation of protein adsorption : New sensing platforms based on nanoscopic devices for probing lipid membrane mediated interactions. VDM Verlag Dr. Müller, 2010.
Trouver le texte intégralChapitres de livres sur le sujet "Protein Mediated Membrane Fusion"
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Ohnishi, Shun-ichi, et Masayuki Murata. « Molecular Mechanism of Protein-Mediated Low ph-Induced Membrane Fusions ». Dans Molecular Mechanisms of Membrane Fusion, 357–66. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1659-6_26.
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Jérôme Vicogne et Jeffrey E. Pessin. « SNARE-Mediated Fusion of LIposomes ». Dans Membrane Trafficking, 241–51. Totowa, NJ : Humana Press, 2008. http://dx.doi.org/10.1007/978-1-59745-261-8_18.
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Vites, Olga, et Reinhard Jahn. « Molecular Mechanisms of Intracellular Membrane Fusion ». Dans Protein-Lipid Interactions, 245–77. Weinheim, FRG : Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527606769.ch11.
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Doms, Robert W., et Ari Helenius. « Properties of a Viral Fusion Protein ». Dans Molecular Mechanisms of Membrane Fusion, 385–98. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1659-6_28.
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Arnold, Klaus, Andreas Herrmann, Klaus Gawrisch et Lothar Pratsch. « Water-Mediated Effects of PEG on Membrane Properties and Fusion ». Dans Molecular Mechanisms of Membrane Fusion, 255–72. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1659-6_19.
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Dall-Bauman, Liese, et Cornelius F. Ivory. « Protein Separation via Affinity-Mediated Membrane Transport ». Dans ACS Symposium Series, 188–211. Washington, DC : American Chemical Society, 1990. http://dx.doi.org/10.1021/bk-1990-0419.ch010.
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Zaks, William J., et Carl E. Creutz. « Membrane Fusion in Model Systems for Exocytosis : Characterization of Chromaffin Granule Fusion Mediated by Synexin and Calelectrin ». Dans Molecular Mechanisms of Membrane Fusion, 325–40. Boston, MA : Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1659-6_24.
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Lai, Alex L., Yinling Li et Lukas K. Tamm. « Interplay of Proteins and Lipids in Virus Entry by Membrane Fusion ». Dans Protein-Lipid Interactions, 279–303. Weinheim, FRG : Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527606769.ch12.
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Simunovic, Mijo, et Gregory A. Voth. « Simulating Protein-Mediated Membrane Remodeling at Multiple Scales ». Dans Physics of Biological Membranes, 351–84. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00630-3_14.
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Tatarchuk, Alexander, Valentina Sulimova, Ivan Torshin, Vadim Mottl et David Windridge. « Supervised Selective Kernel Fusion for Membrane Protein Prediction ». Dans Pattern Recognition in Bioinformatics, 98–109. Cham : Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09192-1_9.
Texte intégralActes de conférences sur le sujet "Protein Mediated Membrane Fusion"
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Moiseeva, Ye M., Yu S. Gusev, I. V. Volokhina, V. V. Fadeev, S. I. Mazilov et M. I. Chumakov. « Editing of genes coding protein involved in maize gamete membrane interaction and fusion ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.174.
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Tsumoto, Kanta, Koki Kamiya, Sayaka Kitaoka, Shin Ogata, Masahiro Tomita et Tetsuro Yoshimura. « G protein coupled receptors (GPCRs) reconstituted on recombinant proteoliposomes using baculovirus-liposome membrane fusion ». Dans 2009 International Symposium on Micro-NanoMechatronics and Human Science (MHS). IEEE, 2009. http://dx.doi.org/10.1109/mhs.2009.5351994.
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Thomas, Antony, Paige Baldwin et Yaling Liu. « Ultrasound Mediated Enhancement of Nanoparticle Uptake in PC-3 Cancer Cells ». Dans ASME 2013 2nd Global Congress on NanoEngineering for Medicine and Biology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/nemb2013-93115.
Texte intégralRésumé :
Ultrasound in the presence of microbubbles brings in transient increase in cell membrane permeability, which allows the entry of foreign molecules into cells. This platform has been applied in in vitro and in vivo gene delivery studies in recent years[1–2]. The frequently used microbubbles are air or inert gas encapsulated in a protein, lipid or polymer which is commonly used as FDA approved contrast agents in diagnostic ultrasound. On exposure to ultrasound the microbubbles lead to formation of small pores on the cell membrane. This work concentrates on application of this platform to enhance cellular uptake of nanoparticles and thereby achieve enhanced drug delivery. Nanoparticles can be manipulated at the nano level and have been applied in the realm of cancer detection and treatment for imaging, targeting tumors, and drug delivery purposes [2].
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Enouf, J., R. Bredoux, A. Giraud, N. Bourdeau et S. Levy-Toledano. « POSSIBLE RELATIONSHIP BETWEEN THE 23-kDa PHOSPHOPROTEIN AND THE IP3 -INDUCED Ca2+RELEASE IN HUMAN PLATELETS ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644516.
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The regulation of Ca2+ concentration in human platelets involves intracellular membranes i.e. dense tubular system (DTS). Agonist-induced platelet activation generates inositol 1,4,5 trisphosphate (IP3) which is responsible for Ca2+ mobilization from DTS. However, its mechanism of action is still unknown. cAMP has been shown to regulate Ca2+ transport by isolated membrane vesicles. This effect was correlated with the phosphorylation of a 23 kDa protein. We investigated whether this phosphorylation could play a role in the mechanism of IP3-induced Ca release.We isolated a membrane fraction enriched in intracellular membranes, which actively sequesters Ca2++. The Ca2+ uptake was mediated by a characterized (Ca2+ + Mg2+)-ATPase of a molecular weight 120 kDa. As well, the characterization of the 23-kDa protein phosphorylation by the catalytic subunit of the cAMP dependent protein kinase (C. Sub.) has been achieved. IP^-induced Ca release was tested on our membrane preparations. The transient effect was maximal at one minute and a dose-response curve was obtained.The cAMP dependent phosphorylation of the 23-kDa protein increased the Ca2+ liberation induced by IP by two fold whatever the IP3 concentration. The addition on the protein kinase inhibitor inhibited the IP3 -induced Ca2+ release.The effect of IP3 on the cAMP-mediated phosphorylation of the 23-kDa protein has been examinated.A dose dependent stimu-ulation of the 23-kDa protein phosphorylation in the presence of C. Sub. was initiated by IP3. The maximal effect was observed after 1-2 min and obtained with an IP3 concentration similar to that producing the maximal calcium release. The stimulation of the phosphorylation by IP3 was detected in the absence of Ca2+ and in the presence of phosphatase inhibitors.Therefore, we suggest a possible correlation between cAMP dependent phosphorylation of the 23-kDa protein and the IP3-induced Ca2+ release in human platelet membrane vesicles.
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Muddana, Hari S., Ramachandra R. Gullapalli et Peter J. Butler. « Tension Induces Changes in Lipid Lateral Diffusion in Model Fluid-Phase Membranes ». Dans ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206867.
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Shear stress due to blood flow on endothelial cells elicits numerous responses including G-protein coupled receptor activation and integrin-mediated signaling. Shear-induced change in membrane fluidity has been suggested to be one of the earliest mechanosensing mechanism involved in these processes [1, 2]. Alternatively, it has been suggested that shear forces are transduced through glycocalyx directly to transmembrane proteins and cytoskeleton [3], with very little shear force sensed by the membrane. It is not yet clear whether physiological tensions can alter membrane fluidity significantly.
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Yin, Lihong, Pravin Rao, Jianghua Wang, Michael Ittmann et Warren D. W. Heston. « Abstract 4057 : Negative regulation of prostate specific membrane antigen by androgen is mediated byTMPRSS2-ERGgene fusion in VCaP prostate cancer cells ». Dans Proceedings : AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010 ; Washington, DC. American Association for Cancer Research, 2010. http://dx.doi.org/10.1158/1538-7445.am10-4057.
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Carroll, R. C. « OPPOSITIONAL REGULATION OF PLATELET CALCIUM FLUX BY cAMP-MEDIATED PHOSPHORYLATION OF GLYCOPROTEIN lb ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643630.
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Glycoprotein (GP) lb, a surface receptor for von Willebrand's factor and thrombin, is composed of two disulfide-linked subunits (alpha - 130 kDa; and beta - 25 kDa). No significance has yet been attributed to the finding that the GPIb beta subunit is the only platelet glycopeptide which is phosphorylated in situ. GPIb can be quantitatively isolated from Triton X-100 wfibTeTlatelet lysates by monoclonal antibody (AN51) to GPIb and Protein A-Sepharose. Using this technique, I find that phosphorylation of the GPIb-beta subunit increased up to three-fold upon exposure of 32P-labeled platelets to agents which increase .platelet cAMP levels. In fact, this glycopeptide is identical to the phospho-peptide identified as 24P in a previous study (Cox et al., J. Cell Biol. 98:8-15, 1984). The phosphorylation of 24P was shown to correlate with cAMP-mediated reversal of platelet activation. This phosphopeptide has also been linked to enhanced calcium uptake by microsomes from platelets pretreated with cAMP elevating agents relative to untreated controls ( Fox et al_., Biochem. J. 184:651-666, 1979). I have further fractionatecTthese membrane fractions by centrifugation on 15% to 55% sucrose gradients and correlated a better than 5-fold enhanced calcium uptake with membrane fractions enriched in phosphorylated GPIb-beta. Confirming evidence was obtained using Bernard-Soulier platelets missing the GPIb complex. These platelets not only lack the 24P phosphopeptide, their activation is not readily reversible by cAMP elevating agents. These studies suggest a major role for GPIb in the inhibition/reversal of platelet activation by cAMP. My hypothesis is that GPIb phosphorylation either stimulates calcium efflux or blocks influx across the platelet plasma membrane.
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Mohamedali, Khalid, Shabnam Mohandessi, Lawrence Cheung, Michael G. Rosenblum et Madhuri Wadehra. « Abstract 4937 : Targeting epithelial membrane protein 2 on breast tumor cells with a fusion construct containing the serine protease granzyme B ». Dans Proceedings : AACR Annual Meeting 2018 ; April 14-18, 2018 ; Chicago, IL. American Association for Cancer Research, 2018. http://dx.doi.org/10.1158/1538-7445.am2018-4937.
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Li, Jianrong, Tianle Cheng et Martin Y. M. Chiang. « Finite Element Modelling of Cell Adhesion Mediated by Receptor-Ligand Binding ». Dans ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206297.
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The process of cell adhesion and spreading on the extracellular matrix (ECM) protein layer is mediated by the interaction of cell receptors and ECM ligands [1]. Receptors diffuse along the cell membrane surface and interact with ligands in ECM to form bonds. Cells spread and the adhesion zone grows as bond formation at the adhesion front increases to a critical level. This process involves coupling of reaction-diffusion and mechanical contact between cells and ECM. In this study, a novel numerical algorithm is developed to implement this coupling into the finite element method for modeling the process of cell adhesion and spreading. By taking the mass diffusion and the user-defined gap conductance features provided in a commercial FEM code, Abaqus [2], the process has been solved in an integrated and fully coupled manner. Preliminary results have been obtained from the simulation of cell spreading on a rigid substrate. The influence of glycocalyx layer (present at cell surface) on the adhesion development has also been incorporated into the modeling.
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Rao, G. H. R., J. M. Gerrard et J. G. White. « EPINEPHRINE INDUCED POTENTIATION OF ARACHIDONATE AGGREGATION IN OUIN 2 LOADED PLATELETS IS NOT MEDIATED BY ELEVATION OF CYTOSOLIC CALCIUM ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643761.
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Previous studies have demonstrated that chelation of ionized cytosolic calcium by Ouin 2 leads to a refractory state in platelets.However, epinephrine (Epi) induced membranemodulation restored the sensitivity of Ouin 2loaded platelets to the action of agonists.Further studies with Ouin 2 and Fura 2 suggested that Epi induced recovery of sensitivity by refractory platelets to aggregation by arachidonate does not require elevation of cytosolic calcium. To further delineate the role of calcium in membrane modulation, we followed phosphoinositol metabolism and myosinlight chain phosphorylation using radiolabeled platelets. The total amount of PI metabolites generated after exposure to Epi, AA or Epi + AA were significantly less than that formed after 0.1 μ thrombin stimulation. Ouin 2 at 40 μM concentration had no inhibitory effect on PI hydrolysis. However, at this concentration it effectively blocked AA induced aggregation. Although Epi treatment restored the sensitivity of Ouin 2 loaded platelets to the action of AA, it did not enhance the formation of increased quantitites of PI metabolites. Similar to earlierstudies, Ouin 2 loading effectively blocked phosphorylation of myosin light chain (20 K).Although a combination of Epi + AA restoredsome phosphorylation of 20 K protein in Ouin2 loaded platelets, the degree of phosphorylation was significantly less than that achieved in control stimulated platelets. Resultsof these studies suggest that Epi induced restoration of sensitivity to refractory, Ouin2 loaded platelets is not mediated by 1) significant elevation of cytosolic calcium, 2) enhanced production of PI metabolites, 3) increased phosphorylation of 20 K protein. Epiinduced membrane modulation is a novel, independent mechanism capable of restoring sensitivity to agonists in platelets with compromised function.
Rapports d'organisations sur le sujet "Protein Mediated Membrane Fusion"
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Avni, Adi, et Gitta L. Coaker. Proteomic investigation of a tomato receptor like protein recognizing fungal pathogens. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600030.bard.
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Maximizing food production with minimal negative effects on the environment remains a long-term challenge for sustainable food production. Microbial pathogens cause devastating diseases, minimizing crop losses by controlling plant diseases can contribute significantly to this goal. All plants possess an innate immune system that is activated after recognition of microbial-derived molecules. The fungal protein Eix induces defense responses in tomato and tobacco. Plants recognize Eix through a leucine-rich-repeat receptor- like-protein (LRR-RLP) termed LeEix. Despite the knowledge obtained from studies on tomato, relatively little is known about signaling initiated by RLP-type immune receptors. The focus of this grant proposal is to generate a foundational understanding of how the tomato xylanase receptor LeEix2 signals to confer defense responses. LeEix2 recognition results in pattern triggered immunity (PTI). The grant has two main aims: (1) Isolate the LeEix2 protein complex in an active and resting state; (2) Examine the biological function of the identified proteins in relation to LeEix2 signaling upon perception of the xylanase elicitor Eix. We used two separate approaches to isolate receptor interacting proteins. Transgenic tomato plants expressing LeEix2 fused to the GFP tag were used to identify complex components at a resting and activated state. LeEix2 complexes were purified by mass spectrometry and associated proteins identified by mass spectrometry. We identified novel proteins that interact with LeEix receptor by proteomics analysis. We identified two dynamin related proteins (DRPs), a coiled coil – nucleotide binding site leucine rich repeat (SlNRC4a) protein. In the second approach we used the split ubiquitin yeast two hybrid (Y2H) screen system to identified receptor-like protein kinase At5g24010-like (SlRLK-like) (Solyc01g094920.2.1) as an interactor of LeEIX2. We examined the role of SlNRC4a in plant immunity. Co-immunoprecipitation demonstrates that SlNRC4a is able to associate with different PRRs. Physiological assays with specific elicitors revealed that SlNRC4a generally alters PRR-mediated responses. SlNRC4a overexpression enhances defense responses while silencing SlNRC4 reduces plant immunity. We propose that SlNRC4a acts as a non-canonical positive regulator of immunity mediated by diverse PRRs. Thus, SlNRC4a could link both intracellular and extracellular immune perception. SlDRP2A localizes at the plasma membrane. Overexpression of SlDRP2A increases the sub-population of LeEIX2 inVHAa1 endosomes, and enhances LeEIX2- and FLS2-mediated defense. The effect of SlDRP2A on induction of plant immunity highlights the importance of endomembrane components and endocytosis in signal propagation during plant immune . The interaction of LeEIX2 with SlRLK-like was verified using co- immunoprecipitation and a bimolecular fluorescence complementation assay. The defence responses induced by EIX were markedly reduced when SlRLK-like was over-expressed, and mutation of slrlk-likeusing CRISPR/Cas9 increased EIX- induced ethylene production and SlACSgene expression in tomato. Co-expression of SlRLK-like with different RLPs and RLKs led to their degradation, apparently through an endoplasmic reticulum-associated degradation process. We provided new knowledge and expertise relevant to expression of specific be exploited to enhance immunity in crops enabling the development of novel environmentally friendly disease control strategies.
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Chen, Junping, Zach Adam et Arie Admon. The Role of FtsH11 Protease in Chloroplast Biogenesis and Maintenance at Elevated Temperatures in Model and Crop Plants. United States Department of Agriculture, mai 2013. http://dx.doi.org/10.32747/2013.7699845.bard.
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specific objectives of this proposal were to: 1) determine the location, topology, and oligomerization of FtsH11 protease; 2) identify the substrate/s of FtsH11 and the downstream components involved in maintaining thermostability of chloroplasts; 3) identify new elements involved in FtsH11 protease regulatory network related to HT adaptation processes in chloroplast; 4) Study the role of FtsH11 homologs from crop species in HT tolerance. Background to the topic: HT-tolerant varieties that maintain high photosynthetic efficiency at HT, and cope better with daily and seasonal temperature fluctuations are in great need to alleviate the effect of global warming on food production. Photosynthesis is a very complex process requiring accurate coordination of many complex systems and constant adjustments to the changing environments. Proteolytic activities mediated by various proteases in chloroplast are essential part of this process and critical for maintaining normal chloroplast functions under HT. However, little is known about mechanisms that contribute to adaptation of photosynthetic processes to HT. Our study has shown that a chloroplast-targeted Arabidopsis FtsH11 protease plays an essential and specific role in maintaining thermostability of thylakoids and normal photosynthesis at moderate HT. We hypothesized that FtsH11 homologs recently identified in other plant species might have roles similarly to that of AtFtsH1. Thus, dissecting the underlying mechanisms of FtsH11 in the adaptation mechanisms in chloroplasts to HT stress and other elements involved will aid our effort to produce more agricultural products in less favorable environments. Major conclusions, solutions, achievements - Identified the chloroplast inner envelope membrane localization of FtsH11. - Revealed a specific association of FtsH11 with the a and b subunits of CPN60. - Identified the involvement of ARC6, a protein coordinates chloroplast division machineries in plants, in FtsH11 mediated HT adaptation process in chloroplast. -Reveal possible association of a polyribonucleotide nucleotidyltransferase (cpPNPase), coded by At3G03710, with FtsH11 mediated HT adaptation process in chloroplast. - Mapped 4 additional loci in FtsH11 mediated HT adaptation network in chloroplast. - Demonstrated importance of the proteolytic activity of FtsH11 for thermotolerance, in addition to the ATPase activity. - Demonstrated a conserved role of plant FtsH11 proteases in chloroplast biogenesis and in maintaining structural and functional thermostability of chloroplast at elevated temperatures. Implications, both scientific and agricultural:Three different components interacting with FtsH11 were identified during the course of this study. At present, it is not known whether these proteins are directly involved in FtsH11mediated thermotolerance network in chloroplast and/or how these elements are interrelated. Studies aiming to connect the dot among biological functions of these networks are underway in both labs. Nevertheless, in bacteria where it was first studied, FtsH functions in heat shock response by regulating transcription level of σ32, a heat chock factor regulates HSPsexpression. FtsH also involves in control of biosynthesis of membrane components and quality control of membrane proteins etc. In plants, both Arc 6 and CPN60 identified in this study are essential in chloroplast division and developments as mutation of either one impairs chloroplast division in Arabidopsis. The facts that we have found the specific association of both α and β CPN60 with FtsH11 protein biochemically, the suppression/ enhancement of ftsh11 thermosensitive phenotype by arc6 /pnp allele genetically, implicate inter-connection of these networks via FtsH11 mediated network(s) in regulating the dynamic adaptation processes of chloroplast to temperature increases at transcriptional, translational and post-translational levels. The conserved role of FtsH11 proteases in maintaining thermostability of chloroplast at HT demonstrated here provides a foundation for improving crop photosynthetic performance at high temperatures.
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Elbaum, Michael, et Peter J. Christie. Type IV Secretion System of Agrobacterium tumefaciens : Components and Structures. United States Department of Agriculture, mars 2013. http://dx.doi.org/10.32747/2013.7699848.bard.
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Objectives: The overall goal of the project was to build an ultrastructural model of the Agrobacterium tumefaciens type IV secretion system (T4SS) based on electron microscopy, genetics, and immunolocalization of its components. There were four original aims: Aim 1: Define the contributions of contact-dependent and -independent plant signals to formation of novel morphological changes at the A. tumefaciens polar membrane. Aim 2: Genetic basis for morphological changes at the A. tumefaciens polar membrane. Aim 3: Immuno-localization of VirB proteins Aim 4: Structural definition of the substrate translocation route. There were no major revisions to the aims, and the work focused on the above questions. Background: Agrobacterium presents a unique example of inter-kingdom gene transfer. The process involves cell to cell transfer of both protein and DNA substrates via a contact-dependent mechanism akin to bacterial conjugation. Transfer is mediated by a T4SS. Intensive study of the Agrobacterium T4SS has made it an archetypal model for the genetics and biochemistry. The channel is assembled from eleven protein components encoded on the B operon in the virulence region of the tumor-inducing plasmid, plus an additional coupling protein, VirD4. During the course of our project two structural studies were published presenting X-ray crystallography and three-dimensional reconstruction from electron microscopy of a core complex of the channel assembled in vitro from homologous proteins of E. coli, representing VirB7, VirB9, and VirB10. Another study was published claiming that the secretion channels in Agrobacterium appear on helical arrays around the membrane perimeter and along the entire length of the bacterium. Helical arrangements in bacterial membranes have since fallen from favor however, and that finding was partially retracted in a second publication. Overall, the localization of the T4SS within the bacterial membranes remains enigmatic in the literature, and we believe that our results from this project make a significant advance. Summary of achievements : We found that polar inflations and other membrane disturbances relate to the activation conditions rather than to virulence protein expression. Activation requires low pH and nutrient-poor medium. These stress conditions are also reflected in DNA condensation to varying degrees. Nonetheless, they must be considered in modeling the T4SS as they represent the relevant conditions for its expression and activity. We identified the T4SS core component VirB7 at native expression levels using state of the art super-resolution light microscopy. This marker of the secretion system was found almost exclusively at the cell poles, and typically one pole. Immuno-electron microscopy identified the protein at the inner membrane, rather than at bridges across the inner and outer membranes. This suggests a rare or transient assembly of the secretion-competent channel, or alternatively a two-step secretion involving an intermediate step in the periplasmic space. We followed the expression of the major secreted effector, VirE2. This is a single-stranded DNA binding protein that forms a capsid around the transferred oligonucleotide, adapting the bacterial conjugation to the eukaryotic host. We found that over-expressed VirE2 forms filamentous complexes in the bacterial cytoplasm that could be observed both by conventional fluorescence microscopy and by correlative electron cryo-tomography. Using a non-retentive mutant we observed secretion of VirE2 from bacterial poles. We labeled the secreted substrates in vivo in order detect their secretion and appearance in the plant cells. However the low transfer efficiency and significant background signal have so far hampered this approach.
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Epel, Bernard, et Roger Beachy. Mechanisms of intra- and intercellular targeting and movement of tobacco mosaic virus. United States Department of Agriculture, novembre 2005. http://dx.doi.org/10.32747/2005.7695874.bard.
Texte intégralRésumé :
To cause disease, plant viruses must replicate and spread locally and systemically within the host. Cell-to-cell virus spread is mediated by virus-encoded movement proteins (MPs), which modify the structure and function of plasmodesmata (Pd), trans-wall co-axial membranous tunnels that interconnect the cytoplasm of neighboring cells. Tobacco mosaic virus (TMV) employ a single MP for cell- cell spread and for which CP is not required. The PIs, Beachy (USA) and Epel (Israel) and co-workers, developed new tools and approaches for study of the mechanism of spread of TMV that lead to a partial identification and molecular characterization of the cellular machinery involved in the trafficking process. Original research objectives: Based on our data and those of others, we proposed a working model of plant viral spread. Our model stated that MPᵀᴹⱽ, an integral ER membrane protein with its C-terminus exposed to the cytoplasm (Reichel and Beachy, 1998), alters the Pd SEL, causes the Pd cytoplasmic annulus to dilate (Wolf et al., 1989), allowing ER to glide through Pd and that this gliding is cytoskeleton mediated. The model claimed that in absence of MP, the ER in Pd (the desmotubule) is stationary, i.e. does not move through the Pd. Based on this model we designed a series of experiments to test the following questions: -Does MP potentiate ER movement through the Pd? - In the presence of MP, is there communication between adjacent cells via ER lumen? -Does MP potentiate the movement of cytoskeletal elements cell to cell? -Is MP required for cell-to-cell movement of ER membranes between cells in sink tissue? -Is the binding in situ of MP to RNA specific to vRNA sequences or is it nonspecific as measured in vitro? And if specific: -What sequences of RNA are involved in binding to MP? And finally, what host proteins are associated with MP during intracellular targeting to various subcellular targets and what if any post-translational modifications occur to MP, other than phosphorylation (Kawakami et al., 1999)? Major conclusions, solutions and achievements. A new quantitative tool was developed to measure the "coefficient of conductivity" of Pd to cytoplasmic soluble proteins. Employing this tool, we measured changes in Pd conductivity in epidermal cells of sink and source leaves of wild-type and transgenic Nicotiana benthamiana (N. benthamiana) plants expressing MPᵀᴹⱽ incubated both in dark and light and at 16 and 25 ᵒC (Liarzi and Epel, 2005 (appendix 1). To test our model we measured the effect of the presence of MP on cell-to-cell spread of a cytoplasmic fluorescent probe, of two ER intrinsic membrane protein-probes and two ER lumen protein-probes fused to GFP. The effect of a mutant virus that is incapable of cell-to-cell spread on the spread of these probes was also determined. Our data shows that MP reduces SEL for cytoplasmic molecules, dilates the desmotubule allowing cell-cell diffusion of proteins via the desmotubule lumen and reduces the rate of spread of the ER membrane probes. Replicase was shown to enhance cell-cell spread. The data are not in support of the proposed model and have led us to propose a new model for virus cell-cell spread: this model proposes that MP, an integral ER membrane protein, forms a MP:vRNAER complex and that this ER-membrane complex diffuses in the lipid milieu of the ER into the desmotubule (the ER within the Pd), and spreads cell to cell by simple diffusion in the ER/desmotubule membrane; the driving force for spread is the chemical potential gradient between an infected cell and contingent non-infected neighbors. Our data also suggests that the virus replicase has a function in altering the Pd conductivity. Transgenic plant lines that express the MP gene of the Cg tobamovirus fused to YFP under the control the ecdysone receptor and methoxyfenocide ligand were generated by the Beachy group and the expression pattern and the timing and targeting patterns were determined. A vector expressing this MPs was also developed for use by the Epel lab . The transgenic lines are being used to identify and isolate host genes that are required for cell-to-cell movement of TMV/tobamoviruses. This line is now being grown and to be employed in proteomic studies which will commence November 2005. T-DNA insertion mutagenesis is being developed to identify and isolate host genes required for cell-to-cell movement of TMV.
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Mevarech, Moshe, Jeremy Bruenn et Yigal Koltin. Virus Encoded Toxin of the Corn Smut Ustilago Maydis - Isolation of Receptors and Mapping Functional Domains. United States Department of Agriculture, septembre 1995. http://dx.doi.org/10.32747/1995.7613022.bard.
Texte intégralRésumé :
Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. Resistance to the toxins is conferred by recessive nuclear genes. The toxins are encoded by genomic segments of resident double-strande RNA viruses. The best characterized toxin, KP6, is composed of two polypeptides, a and b, which are not covalently linked. It is encoded by P6M2 dsRNA, which has been cloned, sequenced and expressed in a variety of systems. In this study we have shown that the toxin acts on the membranes of sensitive cells and that both polypeptides are required for toxin activity. The toxin has been shown to function by creating new pores in the cell membrane and disrupting ion fluxes. The experiments performed on artificial phospholipid bilayers indicated that KP6 forms large voltage-independent, cation-selective channels. Experiments leading to the resolution of structure-function relationship of the toxin by in vitro analysis have been initiated. During the course of this research the collaboration also yielded X-ray diffracion data of the crystallized a polypeptide. The effect of the toxin on the pathogen has been shown to be receptor-mediated. A potential receptor protein, identified in membrane fractions of sensitive cells, was subjected to tryptic hydrolysis followed by amino-acid analysis. The peptides obtained were used to isolate a cDNA fragment by reverse PCR, which showed 30% sequence homology to the human HLA protein. Analysis of other toxins secreted by U. maydis, KP1 and KP4, have demonstrated that, unlike KP6, they are composed of a single polypeptide. Finally, KP6 has been expressed in transgenic tobacco plants, indicating that accurate processing by Kex2p-like activity occurs in plants as well. Using tobacco as a model system, we determined that active antifungal toxins can be synthesized and targeted to the outside of transgenic plant cells. If this methodology can be applied to other agronomically crop species, then U. maydis toxins may provide a novel means for biological control of pathogenic fungi.
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Leitner, Gabriel, et Naomi Balaban. Novel Immunotherapeutic Agent for the Treatment and Prevention of Staphylococcal Mastitis in Dairy Cows. United States Department of Agriculture, janvier 2009. http://dx.doi.org/10.32747/2009.7709880.bard.
Texte intégralRésumé :
Staphylococci are the most common and costly mammary disease of dairy cattle worldwide. TRAP, a membrane associated 167AA protein, is highly conserved among staphylococci. The aims of this study were to test the safety and efficacy of recombinant TRAP (rTRAP) vaccine in dairy animals. The vaccine was safe as 2-3 subcutaneous injections of rTRAP (54–100μg) with adjuvant ISA 206 to cows and goats did not lead to any abnormal symptoms of sensitivity to the vaccine. The rTRAP vaccine was immunogenic and caused the induction of a humoral immune response that remained high for at least 160 days post second immunization. rTRAP vaccine also elicited a cell-mediated immune response (memory CD4+ and CD8+ T cells), as determined by lymphocyte proliferation assays. The rTRAP vaccine was efficacious as at parturition, only 13.5% heifers in the immunized group were infected with Staphylococcus chromogenes as compared to 42.9% in the non immunized group. Additionally, when cows were immunized in mid-lactation, the difference between somatic cell count (SCC) in immunized and control animals was profound (45±7 vs. 470±194, respectively). At the same time, the difference in milk yield was also evident (48.3±1.4 vs. 44.3±0.9 l/day, respectively). Put together, these studies indicate the value of the rTRAP vaccine in preventing new udder infections by staphylococci, which significantly lead to lowered SCC and some increase in milk yield. TRAP is conserved among all strains and species and is constitutively expressed in any strain of S. aureus or CNS tested so far, including those isolated from cows. TRAP may thus serve as a universal anti-staphylococcus vaccine.
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Leitner, Gabriel, et Naomi Balaban. Novel Immunotherapeutic Agent for the Treatment and Prevention of Staphylococcal Mastitis in Dairy Cows. United States Department of Agriculture, janvier 2009. http://dx.doi.org/10.32747/2009.7695866.bard.
Texte intégralRésumé :
Staphylococci are the most common and costly mammary disease of dairy cattle worldwide. TRAP, a membrane associated 167AA protein, is highly conserved among staphylococci. The aims of this study were to test the safety and efficacy of recombinant TRAP (rTRAP) vaccine in dairy animals. The vaccine was safe as 2-3 subcutaneous injections of rTRAP (54–100μg) with adjuvant ISA 206 to cows and goats did not lead to any abnormal symptoms of sensitivity to the vaccine. The rTRAP vaccine was immunogenic and caused the induction of a humoral immune response that remained high for at least 160 days post second immunization. rTRAP vaccine also elicited a cell-mediated immune response (memory CD4+ and CD8+ T cells), as determined by lymphocyte proliferation assays. The rTRAP vaccine was efficacious as at parturition, only 13.5% heifers in the immunized group were infected with Staphylococcus chromogenes as compared to 42.9% in the non immunized group. Additionally, when cows were immunized in mid-lactation, the difference between somatic cell count (SCC) in immunized and control animals was profound (45±7 vs. 470±194, respectively). At the same time, the difference in milk yield was also evident (48.3±1.4 vs. 44.3±0.9 l/day, respectively). Put together, these studies indicate the value of the rTRAP vaccine in preventing new udder infections by staphylococci, which significantly lead to lowered SCC and some increase in milk yield. TRAP is conserved among all strains and species and is constitutively expressed in any strain of S. aureus or CNS tested so far, including those isolated from cows. TRAP may thus serve as a universal anti-staphylococcus vaccine.
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Christopher, David A., et Avihai Danon. Plant Adaptation to Light Stress : Genetic Regulatory Mechanisms. United States Department of Agriculture, mai 2004. http://dx.doi.org/10.32747/2004.7586534.bard.
Texte intégralRésumé :
Original Objectives: 1. Purify and biochemically characterize RB60 orthologs in higher plant chloroplasts; 2. Clone the gene(s) encoding plant RB60 orthologs and determine their structure and expression; 3. Manipulate the expression of RB60; 4. Assay the effects of altered RB60 expression on thylakoid biogenesis and photosynthetic function in plants exposed to different light conditions. In addition, we also examined the gene structure and expression of RB60 orthologs in the non-vascular plant, Physcomitrella patens and cloned the poly(A)-binding protein orthologue (43 kDa RB47-like protein). This protein is believed to a partner that interacts with RB60 to bind to the psbA5' UTR. Thus, to obtain a comprehensive view of RB60 function requires analysis of its biochemical partners such as RB43. Background & Achievements: High levels of sunlight reduce photosynthesis in plants by damaging the photo system II reaction center (PSII) subunits, such as D1 (encoded by the chloroplast tpsbAgene). When the rate of D1 synthesis is less than the rate of photo damage, photo inhibition occurs and plant growth is decreased. Plants use light-activated translation and enhanced psbAmRNA stability to maintain D1 synthesis and replace the photo damaged 01. Despite the importance to photosynthetic capacity, these mechanisms are poorly understood in plants. One intriguing model derived from the algal chloroplast system, Chlamydomonas, implicates the role of three proteins (RB60, RB47, RB38) that bind to the psbAmRNA 5' untranslated leader (5' UTR) in the light to activate translation or enhance mRNA stability. RB60 is the key enzyme, protein D1sulfide isomerase (Pill), that regulates the psbA-RN :Binding proteins (RB's) by way of light-mediated redox potentials generated by the photosystems. However, proteins with these functions have not been described from higher plants. We provided compelling evidence for the existence of RB60, RB47 and RB38 orthologs in the vascular plant, Arabidopsis. Using gel mobility shift, Rnase protection and UV-crosslinking assays, we have shown that a dithiol redox mechanism which resembles a Pill (RB60) activity regulates the interaction of 43- and 30-kDa proteins with a thermolabile stem-loop in the 5' UTR of the psbAmRNA from Arabidopsis. We discovered, in Arabidopsis, the PD1 gene family consists of II members that differ in polypeptide length from 361 to 566 amino acids, presence of signal peptides, KDEL motifs, and the number and positions of thioredoxin domains. PD1's catalyze the reversible formation an disomerization of disulfide bonds necessary for the proper folding, assembly, activity, and secretion of numerous enzymes and structural proteins. PD1's have also evolved novel cellular redox functions, as single enzymes and as subunits of protein complexes in organelles. We provide evidence that at least one Pill is localized to the chloroplast. We have used PDI-specific polyclonal and monoclonal antisera to characterize the PD1 (55 kDa) in the chloroplast that is unevenly distributed between the stroma and pellet (containing membranes, DNA, polysomes, starch), being three-fold more abundant in the pellet phase. PD1-55 levels increase with light intensity and it assembles into a high molecular weight complex of ~230 kDa as determined on native blue gels. In vitro translation of all 11 different Pill's followed by microsomal membrane processing reactions were used to differentiate among PD1's localized in the endoplasmic reticulum or other organelles. These results will provide.1e insights into redox regulatory mechanisms involved in adaptation of the photosynthetic apparatus to light stress. Elucidating the genetic mechanisms and factors regulating chloroplast photosynthetic genes is important for developing strategies to improve photosynthetic efficiency, crop productivity and adaptation to high light environments.
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Philosoph-Hadas, Sonia, Peter B. Kaufman, Shimon Meir et Abraham H. Halevy. Inhibition of the Gravitropic Shoot Bending in Stored Cut Flowers Through Control of Their Graviperception : Involvement of the Cytoskeleton and Cytosolic Calcium. United States Department of Agriculture, décembre 2005. http://dx.doi.org/10.32747/2005.7586533.bard.
Texte intégralRésumé :
Original objectives: The basic goal of the present project was to study the mechanism involved in shoot graviperception and early transduction, in order to determine the sequence of events operating in this process. This will enable to control the entire process of gravity-induced differential growth without affecting vertical growth processes essential for development. Thus, several new postulated interactions, operating at the perception and early transduction stages of the signaling cascade leading to auxin-mediated bending, were proposed to be examined in snapdragon spikes and oat shoot pulvini, according to the following research goals: 1) Establish the role of amyloplasts as gravireceptors in shoots; 2) Investigate gravity-induced changes in the integrity of shoot actin cytoskeleton (CK); 3) Study the cellular interactions among actin CK, statoliths and cell membranes (endoplasmic reticulum - ER, plasma membrane - PM) during shoot graviperception; 4) Examine mediation of graviperception by modulations of cytosolic calcium - [Ca2+]cyt, and other second messengers (protein phosphorylation, inositol 1,4,5-trisphosphate - IP3). Revisions: 1) Model system: in addition to snapdragon (Antirrhinum majus L.) spikes and oat (Avena sativa) shoot pulvini, the model system of maize (Zea mays) primary roots was targeted to confirm a more general mechanism for graviperception. 2) Research topic: brassinolide, which were not included in the original plan, were examined for their regulatory role in gravity perception and signal transduction in roots, in relation to auxin and ethylene. Background to the topic: The negative gravitropic response of shoots is a complex multi-step process that requires the participation of various cellular components acting in succession or in parallel. Most of the long-lasting studies regarding the link between graviperception and cellular components were focused mainly on roots, and there are relatively few reports on shoot graviperception. Our previous project has successfully characterized several key events occurring during shoot bending of cut flowers and oat pulvini, including amyloplast displacement, hormonal interactions and differential growth analysis. Based on this evidence, the present project has focused on studying the initial graviperception process in flowering stems and cereal shoots. Major conclusions and achievements: 1) The actin and not the microtubule (MT) CK is involved in the graviperception of snapdragon shoots. 2) Gravisensing, exhibited by amyloplast displacement, and early transduction events (auxin redistribution) in the gravitropic response of snapdragon spikes are mediated by the acto-myosin complex. 3) MTs are involved in stem directional growth, which occurs during gravitropism of cut snapdragon spikes, but they are not necessary for the gravity-induced differential growth. 4) The role of amyloplasts as gravisensors in the shoot endodermis was demonstrated for both plant systems. 5) A gravity-induced increase in IP.
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Coplin, David, Isaac Barash et Shulamit Manulis. Role of Proteins Secreted by the Hrp-Pathways of Erwinia stewartii and E. herbicola pv. gypsophilae in Eliciting Water-Soaking Symptoms and Initiating Galls. United States Department of Agriculture, juin 2001. http://dx.doi.org/10.32747/2001.7580675.bard.
Texte intégralRésumé :
Many bacterial pathogens of plants can inject pathogenicity proteins into host cells using a specialized type III secretion system encoded by hrpgenes. This system deliver effector proteins, into plant cells that function in both susceptible and resistant interactions. We have found that the virulence of Erwinia stewartii(Es; syn. Pantoea stewartii) and Erwinia herbicola pv. gypsophilae (Ehg, syn. Pantoea agglomerans), which cause Stewart's wilt of corn and galls on Gypsophila, respectively, depends on hrpgenes. The major objectives of this project were: To increase expression of hrpgenes in order to identify secreted proteins; to identify genes for proteins secreted by the type-III systems and determine if they are required for pathogenicity; and to determine if the secreted proteins can function within eukaryotic cells. We found that transcription of the hrp and effector genes in Es and Ehg is controlled by at least four genes that constitute a regulatory cascade. Environmental and/or physiological signaling appears to be mediated by the HrpX/HrpY two component system, with HrpX functioning as a sensor-kinase and HrpY as a response regulator. HrpYupregulateshrpS, which encodes a transcriptional enhancer. HrpS then activates hrpL, which encodes an alternate sigma factor that recognizes "hrp boxes". All of the regulatory genes are essential for pathogenicity, except HrpX, which appears only to be required for induction of the HR in tobacco by Es. In elucidating this regulatory pathway in both species, we made a number of significant new discoveries. HrpX is unusual for a sensor-kinase because it is cytoplasmic and contains PAS domains, which may sense the redox state of the bacterium. In Es, a novel methyl-accepting protein may function upstream of hrpY and repress hrp gene expression in planta. The esaIR quorum sensing system in Es represses hrp gene expression in Es in response to cell-density. We have discovered six new type III effector proteins in these species, one of which (DspE in Ehg and WtsE in Es) is common to both pathogens. In addition, Es wtsG, which is a homolog of an avrPpiB from P. syringae pv. pisi, and an Ehg ORF, which is a homolog of P. syringae pv. phaseolicola AvrPphD, were both demonstrated to encode virulence proteins. Two plasmidborne, Ehg Hop proteins, HsvG and PthG, are required for infection of gypsophilia, but interestingly, PthG also acts as an Avr elicitor in beets. Using a calmodulin-dependent adenylate cyclase (cyaA) reporter gene, we were successful in demonstrating that an HsvG-CyaA fusion protein can be transferred into human HeLa cells by the type-III system of enteropathogenic E. coli. This is a highly significant accomplishment because it is the first direct demonstration that an effector protein from a plant pathogenic bacterium is capable of being translocated into a eukaryotic cell by a type-III secretion system. Ehg is considered a limiting factor in Gypsophila production in Israel and Stewart’s Wilt is a serious disease in the Eastern and North Central USA, especially on sweet corn in epidemic years. We believe that our basic research on the characterization of type III virulence effectors should enable future identification of their receptors in plant cells. This may lead to novel approaches for genetically engineering resistant plants by modifying their receptors or inactivating effectors and thus blocking the induction of the susceptible response. Alternatively, hrp gene regulation might also provide a target for plant produced compounds that interfere with recognition of the host by the pathogen. Such strategies would be broadly applicable to a wide range of serious bacterial diseases on many crops throughout the USA and Israel.