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1.
Ernest S Guadagnini S Prévost MC Soussi-Yanicostas N 《Gene expression patterns : GEP》2007,7(3):274-281
Anosmin-1, encoded by the KAL-1 gene, is the protein defective in the X-linked form of Kallmann syndrome. This human developmental disorder is characterized by defects in cell migration and axon target selection. Anosmin-1 is an extracellular matrix protein that plays a role, in vitro, in processes such as cell adhesion, neurite outgrowth, axon guidance, and axon branching. The zebrafish possesses two orthologues of the KAL-1 gene: kal1a and kal1b, which encode anosmin-1a and anosmin-1b, respectively. Previous in situ hybridization studies have shown that kal1a and kal1b mRNAs are expressed in undetermined cells of the inner ear but not in neuromast cells. Using specific antibodies against anosmin-1a and anosmin-1b, we report here that both proteins are expressed in sensory hair cells of the inner ear cristae ampullaris and the lateral line neuromasts. Accumulation of these proteins was observed mainly at the level of the hair bundle and also at the cell membrane. In neuromast hair cells, immunogold scanning electronmicroscopy demonstrated that anosmin-1a and anosmin-1b were present at the surface of the stereociliary bundle. In addition, anosmin-1a, but not anosmin-1b, was detected on the track of the ampullary nerve. This is the first report of anosmin-1 expression in sensory hair cells of the inner ear and lateral line, and along the ampullary nerve track. 相似文献
2.
Marsollier L Aubry J Coutanceau E André JP Small PL Milon G Legras P Guadagnini S Carbonnelle B Cole ST 《Cellular microbiology》2005,7(7):935-943
Mycobacterium ulcerans was first identified as the causative agent of Buruli ulcer; this cutaneous tissue-destructive process represents the third most important mycobacterial disease in humans after tuberculosis and leprosy. More recently other life traits were documented. M. ulcerans is mainly detected in humid tropical zones as part of a complex ecosystem comprising algae, aquatic insect predators of the genus Naucoris, and very likely their vegetarian preys. Coelomic plasmatocytes could be the first cells of Naucoris cimicoides to be involved in the infection process, acting as shuttle cells that deliver M. ulcerans to the salivary glands as suggested by both in vitro and in vivo approaches. Furthermore, a key element for the early and long-term establishment of M. ulcerans in Naucoridae is demonstrated by the fact that only mycolactone toxin-producing M. ulcerans isolates are able to invade the salivary glands, a site where they proliferate. Later, the raptorial legs of Naucoris are covered by M. ulcerans-containing material that displays features of biofilms. 相似文献
3.
Guillain Mikaty Magali Soyer Emilie Mairey Nelly Henry Dave Dyer Katrina T. Forest Philippe Morand Stéphanie Guadagnini Marie Christine Prévost Xavier Nassif Guillaume Duménil 《PLoS pathogens》2009,5(2)
Bacterial infections targeting the bloodstream lead to a wide array of devastating diseases such as septic shock and meningitis. To study this crucial type of infection, its specific environment needs to be taken into account, in particular the mechanical forces generated by the blood flow. In a previous study using Neisseria meningitidis as a model, we observed that bacterial microcolonies forming on the endothelial cell surface in the vessel lumen are remarkably resistant to mechanical stress. The present study aims to identify the molecular basis of this resistance. N. meningitidis forms aggregates independently of host cells, yet we demonstrate here that cohesive forces involved in these bacterial aggregates are not sufficient to explain the stability of colonies on cell surfaces. Results imply that host cell attributes enhance microcolony cohesion. Microcolonies on the cell surface induce a cellular response consisting of numerous cellular protrusions similar to filopodia that come in close contact with all the bacteria in the microcolony. Consistent with a role of this cellular response, host cell lipid microdomain disruption simultaneously inhibited this response and rendered microcolonies sensitive to blood flow–generated drag forces. We then identified, by a genetic approach, the type IV pili component PilV as a triggering factor of plasma membrane reorganization, and consistently found that microcolonies formed by a pilV mutant are highly sensitive to shear stress. Our study shows that bacteria manipulate host cell functions to reorganize the host cell surface to form filopodia-like structures that enhance the cohesion of the microcolonies and therefore blood vessel colonization under the harsh conditions of the bloodstream. 相似文献
4.
Serge Mostowy Anne Danckaert To Nam Tham Christophe Machu St��phanie Guadagnini Javier Pizarro-Cerd�� Pascale Cossart 《The Journal of biological chemistry》2009,284(17):11613-11621
Septins are filament-forming GTPases implicated in several cellular
functions, including cytokinesis. We previously showed that SEPT2, SEPT9, and
SEPT11 colocalize with several bacteria entering into mammalian non-phagocytic
cells, and SEPT2 was identified as essential for this process. Here, we
investigated the function of SEPT11, an interacting partner of SEPT9 whose
function is still poorly understood. In uninfected HeLa cells, SEPT11
depletion by siRNA increased cell size but surprisingly did not affect actin
filament formation or the colocalization of SEPT9 with actin filaments. SEPT11
depletion increased Listeria invasion, and incubating SEPT11-depleted
cells with beads coated with the Listeria surface protein InlB also
led to increased entry as compared with control cells. Strikingly, as shown by
fluorescence resonance energy transfer, the InlB-mediated stimulation of Met
signaling remained intact in SEPT11-depleted cells. Taken together, our
results show that SEPT11 is not required for the bacterial entry process and
rather restricts its efficacy. Because SEPT2 is essential for the
InlB-mediated entry of Listeria, but SEPT11 is not, our findings
distinguish the roles of different mammalian septins.Septins were discovered in the budding yeast Saccharomyces
cerevisiae (1) where they
organize into a ring at the mother-bud neck during cell division
(2). Septins are GTPases of
30-65 kDa found in most eukaryotes, except plants, sharing an essential role
in cytokinesis (3,
4). Fourteen septins have been
identified in humans and classified on the basis of sequence identity into
four distinct groups (3,
5). Septins from different
groups polymerize into hetero-oligomeric protein complexes and filaments and
may associate with cellular membranes, actin filaments, and microtubules
(6,
7). Septins are increasingly
regarded as novel cytoskeletal elements
(8), but their role in
post-mitotic events remains poorly understood.The crystal structure of the SEPT2-SEPT6-SEPT7 complex recently highlighted
that septins, as opposed to actin and microtubules, form non-polar filaments
(9). In the
SEPT7-SEPT6-SEPT2-SEPT2-SEPT6-SEPT7 complex, SEPT2 has a central role in
filament formation (9), whereas
SEPT6 is thought to be replaceable with other SEPT6 group members, including
SEPT11 (3). Widely expressed in
mammalian tissues (10), SEPT11
may also be a substitute for SEPT6 in other mammalian septin complexes such as
SEPT7-SEPT9-SEPT11 (10) or
SEPT5-SEPT7-SEPT11 (11).
Because other septins homologous to SEPT11 might compensate for its deficiency
(12), the degree to which
SEPT11 is required for septin filament structure and function is not yet
known. Listeria monocytogenes is an invasive bacterium that enters
into most mammalian cells in vitro through the interaction of the
bacterial surface protein InlB with its host cellular receptor Met, the
hepatocyte growth factor receptor
(13). We originally identified
SEPT9 associated with phagosomes containing latex beads coated with InlB
(14). Given the association of
septins with the cytoskeleton, and the importance of the cytoskeleton in
bacterial invasion, we have started investigating septin function during
infection of invasive bacteria in non-phagocytic cells. We have discovered
that SEPT9, and its interacting partners SEPT2 and SEPT11, are recruited as
0.6-μm collars next to actin at the site of entry of invasive bacteria
(15). Although functional
studies using siRNA3
have revealed an essential role for SEPT2 in regulating bacterial entry, the
role of SEPT11 has not yet been investigated. We thus addressed SEPT11
function in the context of Listeria infection. 相似文献
5.
Mathilde Bonis Chantal Ecobichon Stephanie Guadagnini Marie‐Christine Prévost Ivo G. Boneca 《Molecular microbiology》2010,78(4):809-819
The molecular basis of the regulation of specific shapes and their role for the bacterial fitness remain largely unknown. We focused in this study on the Gram‐negative and spiral‐shaped Helicobacter pylori. To colonize its unique niche, H. pylori needs to reach quickly the human gastric mucosa, by swimming to and through the mucus layer. For that reason, the specific shape of H. pylori is predicted to be necessary for optimal motility in vivo, and consequently for its colonization ability. Here, we describe the involvement of a PG‐modifying enzyme, HdpA (HP0506), in the mouse colonization ability of this bacterium, by regulating its shape. Indeed, the inactivation of the hp0506 gene led to a stocky and branched phenotype, affecting H. pylori colonization capacity despite a normal motility phenotype in vitro. In contrast, the overexpression of the hp0506 gene induced the transformation of H. pylori from rod to dividing cocci shaped bacteria. Furthermore, we demonstrated by PG analysis and enzymology, that HdpA carried both d ,d ‐carboxypeptidase and d ,d ‐endopeptidase activities. Thus, HdpA is the first enzyme belonging to the M23‐peptidase family able to perform the d ,d ‐carboxypeptidation and regulate cell shape. 相似文献
6.
Romero S Grompone G Carayol N Mounier J Guadagnini S Prevost MC Sansonetti PJ Van Nhieu GT 《Cell host & microbe》2011,9(6):508-519
Shigella, the causative agent of bacillary dysentery in?humans, invades epithelial cells, using a type III secretory system (T3SS) to inject bacterial effectors into host cells and remodel the actin cytoskeleton. ATP released through connexin hemichanels on the epithelial membrane stimulates Shigella invasion and dissemination in epithelial cells. Here, we show that prior to contact with the cell body, Shigella is captured by nanometer-thin micropodial extensions (NMEs) at a distance from the cell surface, in a process involving the T3SS tip complex proteins and stimulated by ATP- and connexin-mediated signaling. Upon bacterial contact, NMEs retract, bringing bacteria in contact with the cell body, where invasion occurs. ATP stimulates Erk1/2 activation, which controls actin retrograde flow in NMEs and their retraction. These findings reveal previously unappreciated facets of interaction of an invasive bacterium with host cells and a prominent role for Erk1/2 in the control of filopodial dynamics. 相似文献
7.
Marcelo A. Mori Vicência Micheline Sales Fabiana Louise Motta Raphael Gomes Fonseca Natalia Alenina Dioze Guadagnini Ines Schadock Elton Dias Silva Hugo A. M. Torres Edson Lucas dos Santos Charlles Heldan Castro Vania D’Almeida Sandra Andreotti Amanda Baron Campa?a Rogério A. L. Sertié Mario J. A. Saad Fabio Bessa Lima Michael Bader Jo?o Bosco Pesquero 《PloS one》2012,7(9)
Background
Kinins participate in the pathophysiology of obesity and type 2 diabetes by mechanisms which are not fully understood. Kinin B1 receptor knockout mice (B1 −/−) are leaner and exhibit improved insulin sensitivity.Methodology/Principal Findings
Here we show that kinin B1 receptors in adipocytes play a role in controlling whole body insulin action and glucose homeostasis. Adipocytes isolated from mouse white adipose tissue (WAT) constitutively express kinin B1 receptors. In these cells, treatment with the B1 receptor agonist des-Arg9-bradykinin improved insulin signaling, GLUT4 translocation, and glucose uptake. Adipocytes from B1 −/− mice showed reduced GLUT4 expression and impaired glucose uptake at both basal and insulin-stimulated states. To investigate the consequences of these phenomena to whole body metabolism, we generated mice where the expression of the kinin B1 receptor was limited to cells of the adipose tissue (aP2-B1/B1 −/−). Similarly to B1 −/− mice, aP2-B1/B1 −/− mice were leaner than wild type controls. However, exclusive expression of the kinin B1 receptor in adipose tissue completely rescued the improved systemic insulin sensitivity phenotype of B1 −/− mice. Adipose tissue gene expression analysis also revealed that genes involved in insulin signaling were significantly affected by the presence of the kinin B1 receptor in adipose tissue. In agreement, GLUT4 expression and glucose uptake were increased in fat tissue of aP2-B1/B1 −/− when compared to B1 −/− mice. When subjected to high fat diet, aP2-B1/B1 −/− mice gained more weight than B1 −/− littermates, becoming as obese as the wild types.Conclusions/Significance
Thus, kinin B1 receptor participates in the modulation of insulin action in adipocytes, contributing to systemic insulin sensitivity and predisposition to obesity. 相似文献8.
Alireza Gholami Ra?d Kassis Eléonore Real Olivier Delmas Stéphanie Guadagnini Florence Larrous Dorothée Obach Marie-Christine Prevost Yves Jacob Hervé Bourhy 《Journal of virology》2008,82(10):4774-4784
Lyssaviruses are highly neurotropic viruses associated with neuronal apoptosis. Previous observations have indicated that the matrix proteins (M) of some lyssaviruses induce strong neuronal apoptosis. However, the molecular mechanism(s) involved in this phenomenon is still unknown. We show that for Mokola virus (MOK), a lyssavirus of low pathogenicity, the M (M-MOK) targets mitochondria, disrupts the mitochondrial morphology, and induces apoptosis. Our analysis of truncated M-MOK mutants suggests that the information required for efficient mitochondrial targeting and dysfunction, as well as caspase-9 activation and apoptosis, is held between residues 46 and 110 of M-MOK. We used a yeast two-hybrid approach, a coimmunoprecipitation assay, and confocal microscopy to demonstrate that M-MOK physically associates with the subunit I of the cytochrome c (cyt-c) oxidase (CcO) of the mitochondrial respiratory chain; this is in contrast to the M of the highly pathogenic Thailand lyssavirus (M-THA). M-MOK expression induces a significant decrease in CcO activity, which is not the case with M-THA. M-MOK mutations (K77R and N81E) resulting in a similar sequence to M-THA at positions 77 and 81 annul cyt-c release and apoptosis and restore CcO activity. As expected, the reverse mutations, R77K and E81N, introduced in M-THA induce a phenotype similar to that due to M-MOK. These features indicate a novel mechanism for energy depletion during lyssavirus-induced apoptosis.During coevolution with their hosts, viruses have developed many ways of manipulating the cellular machinery of infected cells. They inhibit or induce apoptosis for their own benefit, with the purpose of increasing viral replication and spread or subverting the host''s immune response (4, 12, 51, 59).Mitochondria have several functions in the cell, including energy production, calcium buffering, and regulation of cellular apoptosis. Death signals in the intrinsic pathway of apoptosis act directly on mitochondria, leading to their dysfunction and the release of proapoptotic factors responsible for the caspase-dependent and/or -independent death pathways (43). The process is tightly regulated positively or negatively by proteins from the Bcl-2 family (32). Caspase activation can be initiated in the extrinsic pathway of apoptosis by death receptors expressed at the cell surface; this later causes mitochondrial dysfunction (8, 20).Lyssaviruses are highly neurotropic viruses associated with rabies, a fatal encephalomyelitis considered to be a reemerging zoonosis throughout most of the world (10). It has been suggested that lyssavirus-induced neuronal apoptosis (1), previously thought to be a principal cause of pathogenesis, is an important defense mechanism against lyssavirus infection (26, 34, 56). However, the molecular basis of lyssavirus-induced neuronal apoptosis is still poorly understood (16, 55). The involvement of the viral glycoprotein (G) in inducing neuronal apoptosis has been extensively shown (13, 38, 39, 45), whereas we have suggested that M is an inducer of neuronal cell death through a tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-dependent pathway (29). However, the molecular mechanism of apoptosis has not been precisely defined, and little is known about mitochondrial involvement during lyssavirus infections (46).In this study, we take advantage of the fact that Mokola virus (MOK), a member of the genotype 3 lyssaviruses (5), is known to be less pathogenic than viruses of genotype 1 and, in particular, Thailand virus (THA) (3). We report for the first time the involvement of the mitochondrial machinery during MOK-induced apoptosis. We show that the MOK matrix protein (M-MOK), a previously described apoptogenic factor (29), interacts directly with cytochrome c (cyt-c) oxidase (CcO) subunit I (CcO1), the terminal component of the mitochondrial respiratory chain (MRC). This finding is of interest, as this interaction, which is not found with M-THA, may have a key role in controlling ATP synthesis and cellular respiration during lyssavirus-induced neuronal apoptosis and may contribute to the low pathogenesis of MOK infection. 相似文献
9.
The mechanism by which blood pressure rises in the SHR strain remains to be elucidated. Also, there is a surprising lack of experimental data on the natriuretic mechanisms induced by intracerebroventricular (ICV) injection of hyperosmotic saline (HoS) in SHR. In normotensive animals ICV injection of HoS causes coordinated responses including natriuresis and inhibition of renal sympathetic nerve activity. In the present study, we hypothesized that presumable blunting of the sympathoinhibitory response to centrally injected HoS may contribute to a lack of suppression of efferent renal nerve outflow in SHR. To test this hypothesis, the present study evaluates the influence of renal denervation after central HoS injection at increasing concentration on urinary sodium handling in SHR compared with age-matched normotensive WKy rats. The study confirmed previous data showing pronounced natriuretic response to centrally HoS stimuli but also demonstrated that the creatinine clearance (C(Cr)) and fractional sodium excretion responses diminished as graded NaCl concentrations were increased in WKy rats but not in SHR. In SHR, increased FE(Na) obtained by central administration of 0.90 M NaCl was produced by increases in proximal (FEP(Na)) and post-proximal fractional urinary sodium rejection without changes in C(Cr), indicating a direct tubular effect. Renal denervation caused significant antinatriuresis by decreased C(Cr) and increased FEP(Na) reabsorption in WKy but not in SHR. This study suggests that natriuresis observed only after higher centrally HoS stimuli with a rightward shift of dose-response curve provides evidence of a down-regulation of target organ responsiveness of periventricular areas of genetic hypertensive rats. 相似文献
10.
Boneca IG Ecobichon C Chaput C Mathieu A Guadagnini S Prévost MC Colland F Labigne A de Reuse H 《Applied and environmental microbiology》2008,74(7):2095-2102
The Escherichia coli-Helicobacter pylori shuttle vector pHeL2 was modified to introduce the inducible LacI(q)-pTac system of E. coli, in which the promoters were engineered to be under the control of H. pylori RNA polymerase. The amiE gene promoter of H. pylori was taken to constitutively express the LacI(q) repressor. Expression of the reporter gene lacZ was driven by either pTac (pILL2150) or a modified version of the ureI gene promoter in which one or two LacI-binding sites and/or mutated nucleotides between the ribosomal binding site and the ATG start codon (pILL2153 and pILL2157) were introduced. Promoter activity was evaluated by measuring beta-galactosidase activity. pILL2150 is a tightly regulated expression system suitable for the analysis of genes with low-level expression, while pILL2157 is well adapted for the controlled expression of genes encoding recombinant proteins in H. pylori. To exemplify the usefulness of these tools, we constructed conditional mutants of the putative essential pbp1 and ftsI genes encoding penicillin-binding proteins 1 and 3 of H. pylori, respectively. Both genes were cloned into pILL2150 and introduced in the parental H. pylori strain N6. The chromosomally harbored pbp1 and ftsI genes were then inactivated by replacing them with a nonpolar kanamycin cassette. Inactivation was strictly dependent upon addition of isopropyl-beta-d-thiogalactopyranoside. Hence, we were able to construct the first conditional mutants of H. pylori. Finally, we demonstrated that following in vitro methylation of the recombinant plasmids, these could be introduced into a large variety of H. pylori isolates with different genetic backgrounds. 相似文献