pathogenesis would depend on its ability to enter and replicate inside

pathogenesis would depend on its ability to enter and replicate inside host cells. species are among one of the main bacterial causative agents of gastroenteritis in humans and animals including livestock and the cause of the systemic disease Typhoid fever. Recent outbreaks in the United States were attributed to contaminated peanut butters cantaloupes and raw vegetables. is therefore a re-emerging zoonotic pathogen with a considerable public health burden and economic cost to society. Consequently much research has been conducted to understand and its pathogenesis and develop mechanisms by which to eliminate it and prevent transmission. A characteristic of infection is the uptake of the bacterium into non-phagocytic intestinal epithelial cells.1 2 Genes within a region of the chromosome known as pathogenicity island-1 (SPI-1) encode a type three protein secretion system (T3SS-1) 3 4 which drives bacterial invasion. T3SS-1 translocates SPI-1-encoded effector protein and effectors encoded in the chromosome in to the sponsor cell cytoplasm elsewhere.5 The coordinated actions of the effector Vegfa proteins including SipA SipC SopB/SigD SopE SopE2 and SptP modulate the host cell actin cytoskeleton to market internalisation of in to AMG706 the non-phagocytic cell inside a characteristic membrane ‘ruffle’.6 7 8 9 10 Upon entry towards the sponsor cell is present within a successively modifies the SCV using effectors secreted by T3SS-111 and the pathogenicity island-2 (SPI-2)-encoded type three secretion system (T3SS-2).12 These effector proteins facilitate interactions of the SCV with the host cell endocytic pathway leading to maturation of the SCV 13 14 and also serve to position AMG706 the SCV towards the Golgi where replication is AMG706 initiated.15 For successful invasion and replication inside host cells must spatially and temporally regulate its effector proteinsThis is particularly important in the case of effectors such as SopB which perform more than one role. outer protein B (SopB) is a phosphatidylinositol phosphatase 6 16 being composed of AMG706 a C-terminus that possesses 4-phosphatase motifs16 AMG706 and a synaptojanin-like 5-phosphatase domain.17 SopB uses its phosphatidylinositol phosphatase activity to (i) activate the Rho GTPases RhoG and Rho to mediate actin-dependent and myosin II-dependent bacterial invasion respectively;18 19 (ii) modulate the phosphatidylinositol composition of the plasma membrane to allow SCV formation;20 21 22 (iii) modulate the phosphatidylinositol composition of the SCV to allow maturation in part through the recruitment of host proteins such as Rab5 and Vps3423 and sorting nexins-1 and sorting nexins-3 24 25 and avoidance of SCV-lysosome fusion;26 (iv) activate myosin II to place the SCV in a juxtanuclear position;27 (v) activate serine protein kinase AKT to prevent host cell death via apoptosis;28 and (vi) regulate host cell chloride channel function.29 30 31 The multiple roles of SopB are permitted by regulating its activity through its N-terminal domain and its half-life. Ubiquitination of the N-terminal leads to translocation of SopB from the plasma membrane to the SCV potentially switching the role of SopB from invasion to intracellular survival.32 33 SopB can also bind Cdc42 through its N-terminal 34 35 and this too appears to be important for SopB localisation to the SCV and its spatial regulation.32 35 Although only translocated by T3SS-1 36 37 SopB is detected in cells for up to 12 h post-invasion.38 This relatively long half-life for an effector protein allows SopB to extend its role from the early stages of invasion through to the intracellular phase of survival. As the SCV locates to a juxtanuclear position close to the Golgi it has been proposed that the SCV may also interact with the host’s exocytic/secretory pathway 15 as this occurs with several intracellular pathogens e.g. AMG706 and could indeed recruit secretory vesicles from the trans-Golgi network (TGN) to the SCV in a SPI-2-dependent manner; the SPI-2-secreted effectors SseF SseG and SifA play pivotal roles in post-Golgi vesicle recruitment.40 The interaction of the SCV with the secretory pathway could potentially be important for providing replicating with nutrients and/or to provide membrane material to the growing SCV. However fusion between secretory vesicles and the SCV was not detected by Kuhle (EHEC and EPEC) gastrointestinal pathogens that like.