Nathalie Sauvonnet

Nathalie Sauvonnet
Institut Pasteur International Network · Department of Cell Biology and Infection of Paris

PhD, HDR

About

70
Publications
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2,479
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Publications

Publications (70)
Article
G-protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammati...
Article
Full-text available
Environmental Enteric Dysfunction (EED) refers to an incompletely defined syndrome of inflammation, reduced absorptive capacity, and reduced barrier function in the small intestine. It is widespread among children and adults in low- and middle-income countries and is also associated with poor sanitation and certain gut infections possibly resulting...
Chapter
Invasive pathogenic bacteria exploit the host cell cytoskeleton and intracellular signaling pathways inducing their own uptake into non-phagocytic cells. After entry, some bacteria establish their replicative niche inside a membrane-bound compartment, while others escape to the cytosol where they replicate and disseminate to neighboring cells by me...
Preprint
Full-text available
G protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammati...
Article
Full-text available
SARS-CoV-2 infection results in impaired interferon response in patients with severe COVID-19. However, how SARS-CoV-2 interferes with host immune responses is incompletely understood. Here, we sequence small RNAs from SARS-CoV-2-infected human cells and identify a microRNA (miRNA) derived from a recently evolved region of the viral genome. We show...
Article
The interleukin-2 receptor (IL-2R) is a cytokine receptor essential for immunity that transduces proliferative signals regulated by its uptake and degradation. IL-2R is a well-known marker of clathrin-independent endocytosis (CIE), a process devoid of any coat protein, raising the question of how the CIE vesicle is generated. Here, we investigated...
Preprint
SARS-CoV-2 infection results in impaired interferon response in severe COVID-19 patients. However, how SARS-CoV-2 interferes with host immune response is incompletely understood. Here, we sequenced small RNAs from SARS-CoV-2-infected human cells and identified a micro RNA (miRNA) encoded in a recently evolved region of the viral genome. We show tha...
Article
Full-text available
Infectious diseases remain the subject of intense research. This topic reaches a new era towards the study of host‐pathogen interactions mechanisms at the tissue scale. The past few years have hence witnessed the emergence of new methods. Among them, organ‐on‐chip, which combines biomaterial technology, microfluidic and tissue engineering to recrea...
Chapter
Full-text available
Determination of protein stoichiometry in living cells is key to understanding basic biological processes. This is particularly important for receptor-mediated endocytosis, a highly regulated mechanism that requires the sequential assembly of numerous factors. Here, we describe a quantitative approach to analyze receptor clustering dynamics at the...
Article
Erratum in Bioengineered Human Organ-on-Chip Reveals Intestinal Microenvironment and Mechanical Forces Impacting Shigella Infection. [Cell Host Microbe. 2019]
Article
Intestinal epithelial cells are constantly exposed to pathogens and mechanical forces. However, the impact of mechanical forces on infections leading to diarrheal diseases remains largely unknown. Here, we addressed whether flow and peristalsis impact the infectivity of the human pathogen Shigella within a 3D colonic epithelium using Intestine-Chip...
Article
Intracellular trafficking pathways in eukaryotic cells are essential to maintain organelle identity and structure, and to regulate cell communication with its environment. Shigella flexneri invades and subverts the human colonic epithelium by the injection of virulence factors through a type 3 secretion system (T3SS). In this work, we report the mu...
Article
Full-text available
Elucidating protein functions and molecular organisation requires to localise precisely single or aggregated molecules and analyse their spatial distributions. We develop a statistical method SODA (Statistical Object Distance Analysis) that uses either micro- or nanoscopy to significantly improve on standard co-localisation techniques. Our method c...
Article
Cholesterol is doubtless one of the most studied bio-molecules, which unfortunately features low emitting properties, precluding its in vivo study by fluorescence experiments. The design of fluorescent analogues of cholesterol is thus an appealing challenge in biochemistry, which simultaneously requires minor changes in its chemical structure (to r...
Article
Full-text available
Eukaryotic cells internalize cargos specifically through clathrin-mediated endocytosis (CME) or clathrin-independent endocytosis (CIE). EndophilinA2 was shown as preferentially implicated in CIE, although initially involved in CME. Here, we investigated the native interplay of endophilinA2 and dynamin2 during CME as compared to CIE. We developed an...
Article
Full-text available
Unlabelled: The live attenuated yellow fever virus (YFV) vaccine 17D stands as a "gold standard" for a successful vaccine. 17D was developed empirically by passaging the wild-type Asibi strain in mouse and chicken embryo tissues. Despite its immense success, the molecular determinants for virulence attenuation and immunogenicity of the 17D vaccine...
Data
Transfection of dynamin-2 siRNA impairs transferrin receptor (CD71) internalization. HeLa cells were transfected with an siRNA pool to dynamin-2 (siDyn-2) or the nontargeting negative control (siNT). Cell surface expression of CD71 was assessed 72 h posttransfection by flow cytometry. Download
Data
The 17D vaccine infects human hepatocyte cell lines more efficiently than the parental strain Asibi. Huh7 or HepG2 cells were infected with YFV 17D or Asibi at an MOI of 1. Twenty-four hours after infection, the percentage of infected cells was assessed by flow cytometry using the 2D12 anti-YFV E protein MAb. Download
Data
siRNAs directed against the clathrin heavy chain and caveolin-1 do not impair 17D infection in several human cell lines. Cells of the HeLa, 293T, and Huh7.5 cell lines were transfected with an siRNA pool targeting clathrin heavy chain (siCHC) or caveolin-1 (siCav1) or the nontargeting negative control (siNT). (A) Silencing of CHC and caveolin-1 wer...
Data
Primers used for semiquantitative and real-time PCR.
Data
17D entry is not mediated by the clathrin-independent (CI) pathway that drives IL-2Rβ endocytosis. Download
Data
17D infection is independent of the IL-2Rβ clathrin-independent pathway. Hep2β cells were transfected with siRNA targeting the clathrin heavy chain (siCHC), ATP6V1β2 (siATPB6V1B2), Pak1, Rac1, or cortactin (siCTTN) or the nontargeting negative control (siNT). (A) Silencing was assessed by immunoblotting 72 h posttransfection. (B) Quantification of...
Data
E380 mutant Asibi RVPs are highly sensitive to CHC depletion. HeLa cells were transfected with an siRNA pool targeting the clathrin heavy chain (siCHC) or ATP6V1β2 or a nontargeting siRNA (siNT) as a negative control and then infected with the indicated RVPs 72 h posttransfection. Infection was assessed 24 h later by flow cytometry using the anti-Y...
Data
Effect of clathrin-mediated endocytosis inhibition on 17D and Asibi infection. HeLa cells were transfected with an siRNA pool to clathrin heavy chain (siCHC) or ATP6V1β2 (siATPB6V1B2) or the nontargeting negative control (siNT). (A) Silencing of CHC and ATP6V1β2 was assessed 72 h posttransfection by immunoblotting. (B) Cell surface expression of tr...
Article
Full-text available
Endocytosis controls many functions including nutrient uptake, cell division, migration and signal transduction. A clathrin- and caveolin-independent endocytosis pathway is used by important physiological cargos, including interleukin-2 receptors (IL-2R). However, this process lacks morphological and dynamic data. Our electron microscopy (EM) and t...
Article
Full-text available
The quantitative analysis of molecule interactions in bioimaging is key for understanding the molecular orchestration of cellular processes and is generally achieved through the study of the spatial colocalization between the different populations of molecules. Colocalization methods are traditionally divided into pixel-based methods that measure g...
Article
Full-text available
Endocytosis is required for internalization of micronutrients and turnover of membrane components. Endophilin has been assigned as a component of clathrin-mediated endocytosis. Here we show in mammalian cells that endophilin marks and controls a fast-acting tubulovesicular endocytic pathway that is independent of AP2 and clathrin, activated upon li...
Article
Full-text available
Dynamin superfamily molecular motors use guanosine triphosphate (GTP) as a source of energy for membrane-remodeling events. We found that knockdown of nucleoside diphosphate kinases (NDPKs) NM23-H1/H2, which produce GTP through adenosine triphosphate (ATP)–driven conversion of guanosine diphosphate (GDP), inhibited dynamin-mediated endocytosis. NM2...
Article
Full-text available
CCR5 binds the chemokines CCL3, CCL4, CCL5 and is the major co-receptor for HIV-1 entry into target cells. Chemokines are supposed to form a natural barrier against HIV-1 infection. However, we showed that their antiviral activity is limited by CCR5 adopting low-chemokine affinity conformations at the cell surface. Here, we investigated whether a p...
Article
Full-text available
One major question in molecular biology is whether the spatial distribution of observed molecules is random or organized in clusters. Indeed, this analysis gives information about molecules' interactions and physical interplay with their environment. The standard tool for analyzing molecules' distribution statistically is the Ripley's K function, w...
Article
Full-text available
Class I phosphoinositide 3-kinase (PI3K) is a lipid kinase playing key roles in many signaling pathways regulating cell survival and growth. Besides its important role in signal transduction, PI3K is also involved in actin and membrane reorganization such as protrusion, adhesion, phagocytosis and macropinocytosis. Receptor-mediated endocytosis is i...
Article
Full-text available
Receptor-mediated endocytosis is an essential process used by eukaryotic cells to internalise many molecules. Several clathrin-independent endocytic routes exist but the molecular mechanism of each pathway remains to be uncovered. This study focuses on a clathrin-independent, dynamin-dependent pathway used by interleukin 2 receptors (IL-2R), essent...
Article
Full-text available
Various pathogenic clostridia produce binary protein toxins associated with enteric diseases of humans and animals. Separate binding/translocation (B) components bind to a protein receptor on the cell surface, assemble with enzymatic (A) component(s), and mediate endocytosis of the toxin complex. Ultimately there is translocation of A component(s)...
Article
Shigella infection causes destruction of the human colonic epithelial barrier. The Golgi network and recycling endosomes are essential for maintaining epithelial barrier function. Here we show that Shigella epithelial invasion induces fragmentation of the Golgi complex with consequent inhibition of both secretion and retrograde transport in the inf...
Article
Growing evidence indicates that kinases are central to the regulation of endocytic pathways. Previously, we identified p21-activated kinase 1 (Pak1) as the first specific regulator of clathrin- and caveolae-independent endocytosis used by the interleukin 2 receptor subunit (IL-2R). Here, we address the mechanism by which Pak1 regulates IL-2Rbeta en...
Chapter
Recent advances in fluorescence microscopy provide us with an unprecedented powerful way to observe many biological objects (pathogens, vesicles, single molecules, etc.) and events (intracellular trafficking, adhesion, migration, pathogens entry) in the living cell under multiple experimental conditions. To understand the underlying biological phen...
Article
Inactivation of different small GTPases upon their glucosylation by lethal toxin from Clostridium sordellii strain IP82 (LT-82) is already known to lead to cell rounding, adherens junction (AJ) disorganization and actin depolymerization. In the present work, we observed that LT-82 induces a rapid dephosphorylation of paxillin, a protein regulating...
Article
Full-text available
The facilitative glucose transporter GLUT4, a recycling membrane protein, is required for dietary glucose uptake into muscle and fat cells. GLUT4 is also responsible for the increased glucose uptake by myofibres during muscle contraction. Defects in GLUT4 membrane traffic contribute to loss of insulin-stimulated glucose uptake in insulin resistance...
Chapter
Recent advances in uorescence microscopy provide us with an unprecedented powerful way to observe many biological objects (pathogens, vesicles, single molecules, etc.) and events (intracellular traficking, adhesion, migration, pathogens entry) in the living cell under multiple experimental conditions. To un- derstand the underlying biological pheno...
Article
There are several endocytic pathways, which are either dependent on or independent of clathrin. This study focuses on a poorly characterized mechanism-clathrin- and caveolae-independent endocytosis-used by the interleukin-2 receptor beta (IL-2R beta). We address the question of its regulation in comparison with the clathrin-dependent pathway. First...
Article
Full-text available
Endocytosis is critical for many cellular functions. We show that endocytosis of the common gammac cytokine receptor is clathrin independent by using a dominant-negative mutant of Eps15 or RNA interference to knock down clathrin heavy chain. This pathway is synaptojanin independent and requires the GTPase dynamin. In addition, this process requires...
Article
Full-text available
Interleukin 2 receptors (IL-2R) belong to the cytokine receptor family and share subunits with other members of the family. They are essential in T cell activation and in maintaining homeostatic immune responses. These receptors do not have an intrinsic kinase activity and use multiple signalling pathways. Their endocytic pathway is different from...
Article
Phosphatidylinositol 3-kinase (PI 3-kinase) and its target protein kinase B (Akt) are involved in various processes including internalization, chemotaxis and proliferation. We analysed the activation of Akt in J774 macrophages infected with virulent (pYV+) or avirulent (pYV-) Yersinia enterocolitica. During the early stage of infection with pYV+ an...
Article
Full-text available
The Yop virulon, which comprises a complete type III secretion system and secreted proteins, allows bacteria from the genus Yersinia to resist the nonspecific immune response of the host. This virulon, which is encoded by a plasmid called pYV in Yersinia enterocolitica, enables extracellular bacteria to inject six Yop effectors (YopE, -H, -T, -O, -...
Article
Full-text available
The Yop virulon, which comprises a complete type III secretion system and secreted proteins, allows bacteria from the genus Yersinia to resist the nonspecific immune response of the host. This virulon, which is encoded by a plasmid called pYV in Yersinia enterocolitica, enables extracellular bacteria to inject six Yop effectors (YopE, -H, -T, -O, -...
Article
Full-text available
When expressed in Escherichia coli, the 15Klebsiella oxytoca pul genes that encode the so-called Pul secreton or type II secretion machinery promote pullulanase secretion and the assembly of one of the secreton components, PulG, into pili. Besides these pul genes, efficient pullulanase secretion also requires the host dsbA gene, encoding a periplas...
Article
Full-text available
The secreton (type II secretion) and type IV pilus biogenesis branches of the general secretory pathway in Gram-negative bacteria share many features that suggest a common evolutionary origin. Five components of the secreton, the pseudopilins, are similar to subunits of type IV pili. Here, we report that when the 15 genes encoding the pullulanase s...
Article
Full-text available
Escherichia coli K-12 possesses at least 16 chromosomal genes related to genes involved in the formation of type IV pili in other gram-negative bacteria. However, E. coli K-12 does not produce type IV pili when grown under standard laboratory conditions. The results of reverse transcription-PCR, operon fusion analysis, and immunoblotting demonstrat...
Article
Full-text available
Linker and deletion mutagenesis and gene fusions were used to probe the possible domain structure of the dodecameric outer membrane secretin PulD from the pullulanase secretion pathway of Klebsiella oxytoca. Insertions of 24 amino acids close to or within strongly predicted and highly conserved amphipathic beta strands in the C-terminal half of the...
Article
Results from previous studies have suggested that an intramolecular disulphide bond in the exoprotein pullulanase is needed for its recognition and transport across the outer membrane. This interpretation of the data is shown here to be incorrect: pullulanase devoid of all potential disulphide bonds is secreted with apparently the same efficiency a...
Article
The main terminal branch (MTB) of the general secretory pathway is used by a wide variety of Gram− bacteria to transport exoproteins from the periplasm to the outside milieu. Recent work has led to the identification of the function of two of its 14 (or more) components: an enzyme with type-IV prepilin peptidase activity and a chaperone-like protei...
Article
Pullulanase of Klebsiella oxytoca is one of a wide variety of extracellular proteins that are secreted by Gram-negative bacteria by the complex main terminal branch (MTB) of the general secretory pathway. The roles of some of the 14 components of the MTB are now becoming clear. In this review it is proposed that most of these proteins form a comple...
Article
Pullulanase (PulA) is a 116kDa amylolytic lipoprotein secreted by the Gram-negative bacterium Klebsiella oxytoca via the general secretory pathway. A deletion strategy was used in an attempt to determine the nature and the location of the secretion signal(s) in PulA presumed to be necessary for its specific secretion. The starting material was a ge...
Chapter
One of the basic principles underlying current studies of transmembrane protein traffic is that protein sorting is signal mediated. According to experimentally verified dogma, proteins without targeting signals remain in the cell compartment in which they are synthesised whereas proteins with targeting signals are recognised by receptors in the mem...