title: The SPI-2 type III secretion system restricts motility of Salmonella-containing vacuoles.
abstract: Intracellular replication of Salmonella enterica occurs in membrane-bound compartments, called Salmonella-containing vacuoles (SCVs). Following invasion of epithelial cells, most SCVs migrate to a perinuclear region and replicate in close association with the Golgi network. The association of SCVs with the Golgi is dependent on the Salmonella-pathogenicity island-2 (SPI-2) type III secretion system (T3SS) effectors SseG, SseF and SifA. However, little is known about the dynamics of SCV movement. Here, we show that in epithelial cells, 2 h were required for migration of the majority of SCVs to within 5 microm from the microtubule organizing centre (MTOC), which is located in the same subcellular region as the Golgi network. This initial SCV migration was saltatory, bidirectional and microtubule-dependent. An intact Golgi, SseG and SPI-2 T3SS were dispensable for SCV migration to the MTOC, but were essential for maintenance of SCVs in that region. Live-cell imaging between 4 and 8 h post invasion revealed that the majority of wild-type SCVs displaced less than 2 microm in 20 min from their initial starting positions. In contrast, between 6 and 8 h post invasion the majority of vacuoles containing sseG, sseF or ssaV mutant bacteria displaced more than 2 microm in 20 min from their initial starting positions, with some undergoing large and dramatic movements. Further analysis of the movement of SCVs revealed that large displacements were a result of increased SCV speed rather than a change in their directionality, and that SseG influences SCV motility by restricting vacuole speed within the MTOC/Golgi region. SseG might function by tethering SCVs to Golgi-associated molecules, or by controlling microtubule motors, for example by inhibiting kinesin recruitment or promoting dynein recruitment.
authors.affiliation: Centre for Molecular Microbiology and Infection, Imperial College London, Armstrong Road, London SW7 2AZ, UK.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Ramsden
authors.forename: Luís J
authors.initials: LJ
authors.lastname: Mota
authors.forename: Sylvia
authors.initials: S
authors.lastname: Münter
authors.forename: Spencer L
authors.initials: SL
authors.lastname: Shorte
authors.forename: David W
authors.initials: DW
authors.lastname: Holden
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D004847:Epithelial Cells / Q000502:physiology*; D044404:Genomic Islands; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000378:metabolism; D022101:Microtubule-Organizing Center / Q000378:metabolism; D019779:Salmonella enterica / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000382:microbiology / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D016547:Kinesins