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  • Journal article
    Planamente S, Salih O, Manoli E, Albesa-Jove D, Freemont PS, Filloux AAMet al., 2016,

    TssA forms a gp6-like ring attached to the type VI secretion sheath

    , EMBO Journal, Vol: 35, Pages: 1613-1627, ISSN: 0261-4189

    The type VI secretion system (T6SS) is a supra-molecular bacterial complex that resembles phage tails. It is a killing machine which fires toxins into target cells upon contraction of its TssBC sheath. Here, we show that TssA1 is a T6SS component forming dodecameric ring structures whose dimensions match those of the TssBC sheath and which can accommodate the inner Hcp tube. The TssA1 ring complex binds the T6SS sheath and impacts its behaviour in vivo. In the phage, the first disc of the gp18 sheath sits on a baseplate wherein gp6 is a dodecameric ring. We found remarkable sequence and structural similarities between TssA1 and gp6 C-termini, and propose that TssA1 could be a baseplate component of the T6SS. Furthermore, we identified similarities between TssK1 and gp8, the former interacting with TssA1 while the latter is found in the outer radius of the gp6 ring. These observations, combined with similarities between TssF and gp6N-terminus or TssG and gp53, lead us to propose a comparative model between the phage baseplate and the T6SS.

  • Journal article
    Holmes AH, Gill SK, Hui K, Farne H, Garnett JP, Baines DL, Moore LSP, Filloux A, Tregoning JS, Gill SK, Hui K, Farne H, Garnett JP, Baines DL, Moore LSP, Holmes AH, Filloux A, Tregoning JSet al., 2016,

    Increased airway glucose increases airway bacterial load in hyperglycaemia

    , Scientific Reports, Vol: 6, ISSN: 2045-2322

    Diabetes is associated with increased frequency of hospitalization due to bacterial lung infection.We hypothesize that increased airway glucose caused by hyperglycaemia leads to increasedbacterial loads. In critical care patients, we observed that respiratory tract bacterial colonisationis significantly more likely when blood glucose is high. We engineered mutants in genesaffecting glucose uptake and metabolism (oprB, gltK, gtrS and glk) in Pseudomonas aeruginosa,strain PAO1. These mutants displayed attenuated growth in minimal medium supplemented withglucose as the sole carbon source. The effect of glucose on growth in vivo was tested usingstreptozocin-induced, hyperglycaemic mice, which have significantly greater airway glucose.Bacterial burden in hyperglycaemic animals was greater than control animals when infected withwild type but not mutant PAO1. Metformin pre-treatment of hyperglycaemic animals reducedboth airway glucose and bacterial load. These data support airway glucose as a criticaldeterminant of increased bacterial load during diabetes.

  • Journal article
    Sirianni A, Krokowski S, Lobato-Márquez D, Buranyi S, Pfanzelter J, Galea D, Willis A, Culley S, Henriques R, Larrouy-Maumus G, Hollinshead M, Sancho-Shimizu V, Way M, Mostowy Set al., 2016,

    Mitochondria mediate septin cage assembly to promote autophagy of Shigella

    , EMBO Reports, Vol: 17, ISSN: 1469-221X

    Septins, cytoskeletal proteins with well-characterised roles in cytokinesis, form cage-like structures around cytosolic Shigella flexneri and promote their targeting to autophagosomes. However, the processes underlying septin cage assembly, and whether they influence S. flexneri proliferation, remain to be established. Using single cell analysis, we show that septin cages inhibit S. flexneri proliferation. To study mechanisms of septin cage assembly, we used proteomics and found mitochondrial proteins associate with septins in S. flexneriinfected cells. Strikingly, mitochondria associated with S. flexneri promote septin assembly into the cages that entrap bacteria for autophagy. We demonstrate that the cytosolic GTPase dynamin-related protein 1 (Drp1) interacts with septins to enhance mitochondrial fission. To avoid autophagy, actin-polymerising Shigella fragment mitochondria to escape from septin caging. Our results have demonstrated a role for mitochondria in anti-Shigella autophagy, and uncovered a fundamental link between septin assembly and mitochondria.

  • Journal article
    Furniss RCD, Slater S, Frankel G, Clements Aet al., 2016,

    Enterohaemorrhagic E. coli modulates an ARF6:Rab35 signalling axis to prevent recycling endosome maturation during infection

    , Journal of Molecular Biology, Vol: 428, Pages: 3399-3407, ISSN: 1089-8638

    Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC/EHEC) manipulate a plethora of host cell processes to establish infection of the gut mucosa. This manipulation is achieved via the injection of bacterial effector proteins into host cells using a Type III secretion system. We have previously reported that the conserved EHEC and EPEC effector EspG disrupts recycling endosome function, reducing cell surface levels of host receptors through accumulation of recycling cargo within the host cell. Here we report that EspG interacts specifically with the small GTPases ARF6 and Rab35 during infection. These interactions target EspG to endosomes and prevent Rab35-mediated recycling of cargo to the host cell surface. Furthermore, we show that EspG has no effect on Rab35-mediated uncoating of newly formed endosomes, and instead leads to the formation of enlarged EspG/TfR/Rab11 positive, EEA1/Clathrin negative stalled recycling structures. Thus, this paper provides a molecular framework to explain how EspG disrupts recycling whilst also reporting the first known simultaneous targeting of ARF6 and Rab35 by a bacterial pathogen.

  • Journal article
    Rolhion N, Furniss R, Grabe G, Ryan A, Liu M, Matthews S, Holden DWet al., 2016,

    Inhibition of nuclear transport of NF-kB p65 by the Salmonella type III secretion system effector Sp

    , Plos Pathogens, Vol: 12, ISSN: 1553-7374

    Salmonella enterica replicates in macrophages through the action of effector proteins translocated across the vacuolar membrane by a type III secretion system (T3SS). Here we show that the SPI-2 T3SS effector SpvD suppresses proinflammatory immune responses. SpvD prevented activation of an NF-ĸB-dependent promoter and caused nuclear accumulation of importin-α, which is required for nuclear import of p65. SpvD interacted specifically with the exportin Xpo2, which mediates nuclear-cytoplasmic recycling of importins. We propose that interaction between SpvD and Xpo2 disrupts the normal recycling of importin-α from the nucleus, leading to a defect in nuclear translocation of p65 and inhibition of activation of NF-ĸB regulated promoters. SpvD down-regulated pro-inflammatory responses and contributed to systemic growth of bacteria in mice. This work shows that a bacterial pathogen can manipulate host cell immune responses by interfering with the nuclear transport machinery.

  • Journal article
    Percy M, Karinou E, Webb A, Grundling Aet al., 2016,

    Identification of a lipoteichoic acid glycosyltransferase enzyme reveals that GW-domain containing proteins can be retained in the cell wall of Listeria monocytogenes in the absence of lipoteichoic acid or its modifications

    , Journal of Bacteriology, Vol: 198, Pages: 2029-2042, ISSN: 1098-5530

    Listeria monocytogenes is a food-borne Gram-positive bacterial pathogen and many of its virulence factors are either secreted proteins, or proteins covalently or non-covalently-attached to the cell wall. Previous work has indicated that non-covalently-attached proteins with GW domains are retained in the cell wall by binding to the cell wall polymer lipoteichoic acid (LTA). LTA is a glycerolphosphate polymer, which is modified in L. monocytogenes with galactose and D-alanine residues. We identified Lmo0933 as the cytoplasmic glycosyltransferase required for the LTA glycosylation process and renamed the protein GtlA for glycosyltransferase LTA A. Using L. monocytogenes mutants lacking galactose or D-alanine modifications or the complete LTA polymer, we show that GW-domain proteins are still retained within the cell wall, indicating that other cell wall polymers are involved in the retention of GW-domain proteins. Further experiments reveal peptidoglycan as the binding receptor as a purified GW domainfusion protein can bind to L. monocytogenes cells lacking wall teichoic acid (WTA) as well as purified peptidoglycan derived from a wild-type or WTA-negative strain. With this, we not only identified the first enzyme involved in the LTA glycosylation process, but we also provide new insight into the binding mechanism of non-covalently attached cell wall proteins.

  • Journal article
    Santos AJM, Durkin C, Helaine S, Boucrot E, Holden DWet al., 2016,

    Clustered intracellular Salmonella Typhimurium Blocks Host Cell Cytokinesis

    , Infection and Immunity, Vol: 84, Pages: 2149-2158, ISSN: 1098-5522

    Several bacterial pathogens and viruses interfere with the cell cycle of their host cells to enhance virulence. This is especially apparent in bacteria that colonise the gut epithelium, where inhibition of the cell cycle of infected cells enhances the intestinal colonisation. We found that intracellular Salmonella enterica Typhimurium induced the binucleation of a large proportion of epithelial cells by 14 hours post invasion, which was dependent on an intact Salmonella pathogenicity island-2 (SPI-2) type 3 secretion system. The SPI-2 effectors SseF and SseG were required to induce binucleation. SseF and SseG are known to maintain microcolonies of Salmonella-containing vacuoles close to the microtubule organising centre of infected epithelial cells. During host cell division these clustered microcolonies prevented the correct localisation of members of the chromosomal passenger complex and mitotic kinesin-like protein 1, and consequently prevented cytokinesis. Tetraploidy, arising from a cytokinesis defect, is known to have a deleterious effect on subsequent cell divisions, either resulting in chromosomal instabilities or cell cycle arrest. In infected mice, proliferation of small intestinal epithelial cells was compromised in an SseF/SseG-dependent manner, suggesting that cytokinesis failure caused by S. Typhimurium delays epithelial cell turnover in the intestine.

  • Journal article
    Lund-Palau H, Turnbull AR, Bush A, Bardin E, Cameron L, Soren O, Wierre-Gore N, Alton EW, Bundy JG, Connett G, Faust SN, Filloux A, Freemont P, Jones A, Khoo V, Morales S, Murphy R, Pabary R, Simbo A, Schelenz S, Takats Z, Webb J, Williams HD, Davies JCet al., 2016,

    Pseudomonas aeruginosa infection in cystic fibrosis: pathophysiological mechanisms and therapeutic approaches

    , Expert Review of Respiratory Medicine, Vol: 10, Pages: 685-697, ISSN: 1747-6348

    Pseudomonas aeruginosa is a remarkably versatile environmental bacterium with an extraordinary capacity to infect the cystic fibrosis (CF) lung. Infection with P. aeruginosa occurs early, and although eradication can be achieved following early detection, chronic infection occurs in over 60% of adults with CF. Chronic infection is associated with accelerated disease progression and increased mortality. Extensive research has revealed complex mechanisms by which P. aeruginosa adapts to and persists within the CF airway. Yet knowledge gaps remain, and prevention and treatment strategies are limited by the lack of sensitive detection methods and by a narrow armoury of antibiotics. Further developments in this field are urgently needed in order to improve morbidity and mortality in people with CF. Here, we summarize current knowledge of pathophysiological mechanisms underlying P. aeruginosa infection in CF. Established treatments are discussed, and an overview is offered of novel detection methods and therapeutic strategies in development.

  • Journal article
    Chambonnier G, Roux L, Redelberger D, Fadel F, Filloux A, Sivaneson M, de Bentzmann S, Bordi Cet al., 2016,

    The Hybrid Histidine Kinase LadS Forms a Multicomponent Signal Transduction System with the GacS/GacA Two-Component System in Pseudomonas aeruginosa.

    , PLOS Genetics, Vol: 12, ISSN: 1553-7390

    In response to environmental changes, Pseudomonas aeruginosa is able to switch from a planktonic (free swimming) to a sessile (biofilm) lifestyle. The two-component system (TCS) GacS/GacA activates the production of two small non-coding RNAs, RsmY and RsmZ, but four histidine kinases (HKs), RetS, GacS, LadS and PA1611, are instrumental in this process. RetS hybrid HK blocks GacS unorthodox HK autophosphorylation through the formation of a heterodimer. PA1611 hybrid HK, which is structurally related to GacS, interacts with RetS in P. aeruginosa in a very similar manner to GacS. LadS hybrid HK phenotypically antagonizes the function of RetS by a mechanism that has never been investigated. The four sensors are found in most Pseudomonas species but their characteristics and mode of signaling may differ from one species to another. Here, we demonstrated in P. aeruginosa that LadS controls both rsmY and rsmZ gene expression and that this regulation occurs through the GacS/GacA TCS. We additionally evidenced that in contrast to RetS, LadS signals through GacS/GacA without forming heterodimers, either with GacS or with RetS. Instead, we demonstrated that LadS is involved in a genuine phosphorelay, which requires both transmitter and receiver LadS domains. LadS signaling ultimately requires the alternative histidine-phosphotransfer domain of GacS, which is here used as an Hpt relay by the hybrid kinase. LadS HK thus forms, with the GacS/GacA TCS, a multicomponent signal transduction system with an original phosphorelay cascade, i.e. H1LadS→D1LadS→H2GacS→D2GacA. This highlights an original strategy in which a unique output, i.e. the modulation of sRNA levels, is controlled by a complex multi-sensing network to fine-tune an adapted biofilm and virulence response.

  • Journal article
    Armstrong-James DPH, 2016,

    Calcineurin Orchestrates Lateral Transfer of Aspergillus fumigatus during Macrophage Cell Death

    , American Journal of Respiratory and Critical Care Medicine, Vol: 194, Pages: 1127-1139, ISSN: 1535-4970

    Rationale: Pulmonary aspergillosis is a lethal mold infection in the immunocompromised host. Understanding initial control of infection and how this is altered in the immunocompromised host are key goals for comprehension of the pathogenesis of pulmonary aspergillosis.Objectives: To characterize the outcome of human macrophage infection with Aspergillus fumigatus and how this is altered in transplant recipients on calcineurin inhibitor immunosuppressants.Methods: We defined the outcome of human macrophage infection with A. fumigatus, as well as the impact of calcineurin inhibitors, through a combination of single-cell fluorescence imaging, transcriptomics, proteomics, and in vivo studies.Measurements and Main Results: Macrophage phagocytosis of A. fumigatus enabled control of 90% of fungal germination. However, fungal germination in the late phagosome led to macrophage necrosis. During programmed necroptosis, we observed frequent cell–cell transfer of A. fumigatus between macrophages, which assists subsequent control of germination in recipient macrophages. Lateral transfer occurred through actin-dependent exocytosis of the late endosome in a vasodilator-stimulated phosphoprotein envelope. Its relevance to the control of fungal germination was also shown by direct visualization in our zebrafish aspergillosis model in vivo. The calcineurin inhibitor FK506 (tacrolimus) reduced cell death and lateral transfer in vitro by 50%. This resulted in uncontrolled fungal germination in macrophages and also resulted in hyphal escape.Conclusions: These observations identify programmed, necrosis-dependent lateral transfer of A. fumigatus between macrophages as an important host strategy for controlling fungal germination. This process is critically dependent on calcineurin. Our studies provide fundamental insights into the pathogenesis of pulmonary aspergillosis in the immunocompromised host.

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