11 results on '"Gallardo, Cesar"'
Search Results
2. IpaA reveals distinct modes of vinculin activation during Shigella invasion and cell-matrix adhesion.
- Author
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Cocom-Chan, Benjamin, Khakzad, Hamed, Konate, Mahamadou, Aguilar, Daniel Isui, Bello, Chakir, Valencia-Gallardo, Cesar, Zarrouk, Yosra, Fattaccioli, Jacques, Mauviel, Alain, Javelaud, Delphine, and Van Nhieu, Guy Tran
- Published
- 2024
- Full Text
- View/download PDF
3. Accurate Analytical Model for Synchronous Reluctance Machine With Multiple Flux Barriers Considering the Slotting Effect.
- Author
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Gallardo, Cesar, Tapia, Juan A., Degano, Michele, and Mahmoud, Hanafy
- Subjects
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RELUCTANCE motors , *AIR gap flux , *ELECTRIC flux , *FINITE element method , *ACTINIC flux , *MAGNETIC circuits - Abstract
This article presents an accurate analytical model (AM) for synchronous reluctance machine (SynRM) that incorporates the effect of stator slots on the air gap flux density and torque waveforms. From the formulation of magnetic potential in the air gap for both the stator and rotor, the flux density is obtained, considering the first harmonic of the flux density and the electric loading, the average torque is calculated using the Lorentz’s force. The ripple torque is obtained from the energy stored in magnetic circuit. The method is developed for a rotor with one flux barrier per pole and then extended to a larger number of barriers. To validate the results obtained by the AM proposed finite element analysis have been carried out. Several comparisons have been derived considering different rotor positions as well as different harmonic orders, and the pros and cons of the method are highlighted. The model performs fast and can predict results with high accuracy, and can be adopted to speed up the preliminary design and optimizations of this type of motors, with respect to finite element. In addition, from the analytical expressions it is possible to obtain all the correlations between electrical, magnetic, and geometrical characteristics of the machine, with the advantage of enabling a faster machine design. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Vinculin targeting by Shigella IpaA promotes stable cell adhesion independent of mechanotransduction
- Author
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Valencia-Gallardo, Cesar, Aguilar-Salvador, Daniel-Isui, Khakzad, Hamed, Bou-Nader, Charles, Malosse, Christian, Lima, Diogo Borges, Bello, Chakir, Cocom-Chan, Benjamin, Quenech’Du, Nicole, Mazhar, Bilal, Javelaud, Delphine, Fattaccioli, Jacques, Mauviel, Alain, Fontecave, Marc, Asnacios, Atef, Chamot-Rooke, Julia, Malmström, Lars, and Van Nhieu, Guy Tran
- Subjects
macromolecular substances - Abstract
Shigella , the causative agent of bacillary dysentery, invades epithelial cells by injecting type III effectors that locally reorganize the actin cytoskeleton 1 . The type III effector IpaA targets the focal adhesion protein vinculin to induce bacterial adhesion associated with the recruitment of mature focal adhesion markers, despite the inability of bacteria to exert significant counter-forces 2, 3 . Here, we show that three vinculin-binding sites (VBSs) exposed at the IpaA C-terminus act in a cooperative manner to trigger a yet unreported mode of vinculin activation through specific interactions with sites in the vinculin head sub-domain D2. Structural modeling based on the mass spectrometry identification of interacting residues by cross-linking indicated that upon IpaA binding to vinculin D2, vinculin head sub-domains undergo major conformational changes leading to higher order heterocomplexes and vinculin homo-trimers. IpaA-mediated vinculin activation induces the formation of large and stable focal adhesions resisting the action of actin relaxing drugs. This property enables IpaA to rapidly elicit strong cell adhesion to fibronectin-coated substrates. While Shigella IpaA promotes strong adhesion in the absence of mechanotransduction, its mode of vinculin activation likely reflects a key step during maturation of cell adhesions driven by acto-myosin contractility.
- Published
- 2019
- Full Text
- View/download PDF
5. Shigella IpaA Binding to Talin Stimulates Filopodial Capture and Cell Adhesion
- Author
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Valencia-Gallardo, Cesar, Bou-Nader, Charles, Aguilar-Salvador, Daniel-Isui, Carayol, Nathalie, Quenech’Du, Nicole, Pecqueur, Ludovic, Park, HaJeung, Fontecave, Marc, Izard, Tina, Tran Van Nhieu, Guy, Centre interdisciplinaire de recherche en biologie (CIRB), Labex MemoLife, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Collège de France (CdF (institution))-Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie des Processus Biologiques (LCPB), Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Chaire Chimie des processus biologiques, and Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[SDV]Life Sciences [q-bio] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2019
6. Shubayqa 6 : a new Late Natufian and Pre-Pottery Neolithic A settlement in north-east Jordan
- Author
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Arranz Otaegui, Amaia, Boaretto, Elisabetta, Bocaege, Emmy, Estrup, Erin, Martinez-Gallardo, Cesar, Pantos, Alexis, University of Copenhagen = Københavns Universitet (KU), Weizmann Institute of Science [Rehovot, Israël], De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie (PACEA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Chercheur indépendant, and Glasgow School of Art
- Subjects
[SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory ,Neolithic ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2016
7. The Shigella type III effector IpgD recodes Ca2+ signals during invasion of epithelial cells.
- Author
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Sun, Chun Hui, Wacquier, Benjamin, Aguilar, Daniel I, Carayol, Nathalie, Denis, Kevin, Boucherie, Sylviane, Valencia‐Gallardo, Cesar, Simsek, Ceren, Erneux, Christophe, Lehman, Alexandre, Enninga, Jost, Arbibe, Laurence, Sansonetti, Philippe, Dupont, Geneviève, Combettes, Laurent, and Tran Van Nhieu, Guy
- Subjects
SHIGELLA ,EPITHELIAL cells ,CALPAIN genetics ,PROTEINASE genetics ,PATHOGENIC microorganisms - Abstract
The role of second messengers in the diversion of cellular processes by pathogens remains poorly studied despite their importance. Among these, Ca
2+ virtually regulates all known cell processes, including cytoskeletal reorganization, inflammation, or cell death pathways. Under physiological conditions, cytosolic Ca2+ increases are transient and oscillatory, defining the so-called Ca2+ code that links cell responses to specific Ca2+ oscillatory patterns. During cell invasion, Shigella induces atypical local and global Ca2+ signals. Here, we show that by hydrolyzing phosphatidylinositol-(4,5)bisphosphate, the Shigella type III effector IpgD dampens inositol-(1,4,5)trisphosphate (InsP3 ) levels. By modifying InsP3 dynamics and diffusion, IpgD favors the elicitation of long-lasting local Ca2+ signals at Shigella invasion sites and converts Shigella-induced global oscillatory responses into erratic responses with atypical dynamics and amplitude. Furthermore, IpgD eventually inhibits InsP3 -dependent responses during prolonged infection kinetics. IpgD thus acts as a pathogen regulator of the Ca2+ code implicated in a versatility of cell functions. Consistent with this function, IpgD prevents the Ca2+ -dependent activation of calpain, thereby preserving the integrity of cell adhesion structures during the early stages of infection. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
8. Cytoskeletal mechanics during S higella invasion and dissemination in epithelial cells.
- Author
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Valencia‐Gallardo, Cesar M., Carayol, Nathalie, and Tran Van Nhieu, Guy
- Subjects
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BACTERIA cytoskeleton , *ACTIN , *BIOMECHANICS , *SHIGELLA , *EPITHELIAL cells , *MICROBIAL invasiveness - Abstract
The actin cytoskeleton is key to the barrier function of epithelial cells, by permitting the establishment and maintenance of cell-cell junctions and cell adhesion to the basal matrix. Actin exists under monomeric and polymerized filamentous form and its polymerization following activation of nucleation promoting factors generates pushing forces, required to propel intracellular microorganisms in the host cell cytosol or for the formation of cell extensions that engulf bacteria. Actin filaments can associate with adhesion receptors at the plasma membrane via cytoskeletal linkers. Membrane anchored to actin filaments are then subjected to the retrograde flow that may pull membrane-bound bacteria inside the cell. To induce its internalization by normally non-phagocytic cells, bacteria need to establish adhesive contacts and trick the cell into apply pulling forces, and/or to generate protrusive forces that deform the membrane surrounding its contact site. In this review, we will focus on recent findings on actin cytoskeleton reorganization within epithelial cells during invasion and cell-to-cell spreading by the enteroinvasive pathogen S higella, the causative agent of bacillary dysentery. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
9. Shigella IpaA Binding to Talin Stimulates Filopodial Capture and Cell Adhesion.
- Author
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Valencia-Gallardo C, Bou-Nader C, Aguilar-Salvador DI, Carayol N, Quenech'Du N, Pecqueur L, Park H, Fontecave M, Izard T, and Tran Van Nhieu G
- Subjects
- Antigens, Bacterial genetics, Bacterial Proteins genetics, Crystallography, X-Ray, HeLa Cells, Humans, Protein Domains, Pseudopodia genetics, Pseudopodia metabolism, Shigella flexneri genetics, Shigella flexneri metabolism, Static Electricity, Talin genetics, Talin metabolism, Antigens, Bacterial chemistry, Bacterial Proteins chemistry, Cell Adhesion, Pseudopodia chemistry, Shigella flexneri chemistry, Talin chemistry
- Abstract
The Shigella type III effector IpaA contains three binding sites for the focal adhesion protein vinculin (VBSs), which are involved in bacterial invasion of host cells. Here, we report that IpaA VBS3 unexpectedly binds to talin. The 2.5 Å resolution crystal structure of IpaA VBS3 in complex with the talin H1-H4 helices shows a tightly folded α-helical bundle, which is in contrast to the bundle unraveling upon vinculin interaction. High-affinity binding to talin H1-H4 requires a core of hydrophobic residues and electrostatic interactions conserved in talin VBS H46. Remarkably, IpaA VBS3 localizes to filopodial distal adhesions enriched in talin, but not vinculin. In addition, IpaA VBS3 binding to talin was required for filopodial adhesions and efficient capture of Shigella. These results point to the functional diversity of VBSs and support a specific role for talin binding by a subset of VBSs in the formation of filopodial adhesions., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
10. The Shigella type III effector IpgD recodes Ca 2+ signals during invasion of epithelial cells.
- Author
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Sun CH, Wacquier B, Aguilar DI, Carayol N, Denis K, Boucherie S, Valencia-Gallardo C, Simsek C, Erneux C, Lehman A, Enninga J, Arbibe L, Sansonetti P, Dupont G, Combettes L, and Tran Van Nhieu G
- Subjects
- Calpain metabolism, Cell Adhesion, HeLa Cells, Humans, Signal Transduction, Bacterial Proteins metabolism, Calcium metabolism, Dysentery, Bacillary metabolism, Host-Pathogen Interactions, Phosphoric Monoester Hydrolases metabolism, Phosphotransferases (Alcohol Group Acceptor) metabolism, Shigella flexneri physiology
- Abstract
The role of second messengers in the diversion of cellular processes by pathogens remains poorly studied despite their importance. Among these, Ca
2+ virtually regulates all known cell processes, including cytoskeletal reorganization, inflammation, or cell death pathways. Under physiological conditions, cytosolic Ca2+ increases are transient and oscillatory, defining the so-called Ca2+ code that links cell responses to specific Ca2+ oscillatory patterns. During cell invasion, Shigella induces atypical local and global Ca2+ signals. Here, we show that by hydrolyzing phosphatidylinositol-(4,5)bisphosphate, the Shigella type III effector IpgD dampens inositol-(1,4,5)trisphosphate (InsP3 ) levels. By modifying InsP3 dynamics and diffusion, IpgD favors the elicitation of long-lasting local Ca2+ signals at Shigella invasion sites and converts Shigella -induced global oscillatory responses into erratic responses with atypical dynamics and amplitude. Furthermore, IpgD eventually inhibits InsP3 -dependent responses during prolonged infection kinetics. IpgD thus acts as a pathogen regulator of the Ca2+ code implicated in a versatility of cell functions. Consistent with this function, IpgD prevents the Ca2+ -dependent activation of calpain, thereby preserving the integrity of cell adhesion structures during the early stages of infection., (© 2017 The Authors.)- Published
- 2017
- Full Text
- View/download PDF
11. Novel vinculin binding site of the IpaA invasin of Shigella.
- Author
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Park H, Valencia-Gallardo C, Sharff A, Tran Van Nhieu G, and Izard T
- Subjects
- Antigens, Bacterial, Bacterial Proteins, Binding Sites, Crystallography, X-Ray, Dysentery, Bacillary genetics, Dysentery, Bacillary metabolism, HeLa Cells, Humans, Molecular Mimicry physiology, Protein Structure, Secondary, Protein Structure, Tertiary, Shigella flexneri genetics, Shigella flexneri pathogenicity, Talin chemistry, Talin genetics, Talin metabolism, Vinculin genetics, Shigella flexneri chemistry, Shigella flexneri metabolism, Vinculin chemistry, Vinculin metabolism
- Abstract
Internalization of Shigella into host epithelial cells, where the bacteria replicates and spreads to neighboring cells, requires a type 3 secretion system (T3SS) effector coined IpaA. IpaA binds directly to and activates the cytoskeletal protein vinculin after injection in the host cell cytosol, and this was previously thought to be directed by two amphipathic α-helical vinculin-binding sites (VBS) found in the C-terminal tail domain of IpaA. Here, we report a third VBS, IpaA-VBS3, that is located N-terminal to the other two VBSs of IpaA and show that one IpaA molecule can bind up to three vinculin molecules. Biochemical in vitro Shigella invasion assays and the 1.6 Å crystal structure of the vinculin·IpaA-VBS3 complex showed that IpaA-VBS3 is functionally redundant with the other two IpaA-VBSs in cell invasion and in activating the latent F-actin binding functions of vinculin. Multiple VBSs in IpaA are reminiscent of talin, which harbors 11 VBSs. However, most of the talin VBSs have low affinity and are buried in helix bundles, whereas all three of the VBSs of IpaA are high affinity, readily available, and in close proximity to each other in the IpaA structure. Although deletion of IpaA-VBS3 has no detectable effects on Shigella invasion of epithelial cells, deletion of all three VBSs impaired bacterial invasion to levels found in an ipaA null mutant strain. Thus, IpaA-directed mimicry of talin in activating vinculin occurs through three high affinity VBSs that are essential for Shigella pathogenesis.
- Published
- 2011
- Full Text
- View/download PDF
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