Shigella, a major etiologic agent of diarrhea, dysentery, and mortality worldwide, causes disease by invading and disseminating through the colonic mucosa. Shigella sp. are CDC/NIAID priority pathogens. After inducing their own entry into cells, bacteria move to the cell periphery by actin-based motility. At the cell periphery, they push out against the plasma membrane, forming cell extensions that are engulfed by uninfected adjacent cells, whereupon the cycle of cell-to-cell dissemination is repeated. Shigella and other intracellular pathogens enhance the process of infection by activating normal host cell signaling pathways. To activate these pathways, these microorganisms secrete into the host cell effector proteins that modulate the activity of specific host proteins. Whereas the molecular signaling events involved in S. flexneri entry into cells have been studied extensively, the signaling events involved in S. flexneri dissemination from one cell into an adjacent cell are poorly understood. In this application, we propose a detailed investigation of the molecular signaling events that occur during S. flexneri intercellular dissemination, using both targeted and genome-wide approaches. Our preliminary data indicate that the cellular diaphanous formin proteins mDia1 and mDia2, which function in the stress fiber formation pathway, are required for efficient dissemination through cell monolayers. Our data also indicate that the secreted S. flexneri proteins IpgB2, OspE1, and OspE2 are required for this process and that these proteins trigger partially redundant host signaling pathways that likely involve mDia1 and mDia2. In addition, our data indicate that IpgB2/OspE1/OspE2-independent mechanisms also contribute to dissemination. Our targeted approaches will test the hypothesis that IpgB2, OspE1, and OspE2 activate specific steps in the stress fiber formation pathway. Our genome-wide approach will examine the human genome for additional factors involved in intercellular dissemination.
Our specific aims are: 1. Characterize the mechanisms of S. flexneri IpgB2 activation of the stress fiber formation pathway;2. Characterize the roles of secreted S. flexneri effector proteins OspE1 and OspE2 in intercellular dissemination;and, 3. Identify and characterize other host factors required for S. flexneri intercellular spread using a genome- wide human siRNA screen; Our approaches are designed to generate insights not only into the molecular signaling that is required for intercellular dissemination of S. flexneri, but also into fundamental mechanisms of eukaryotic cellular and intercellular processes.
The human pathogen Shigella is a bacterium that causes diarrhea by infecting cells that line the human intestinal tract and disseminating through intestinal tissue by mechanisms that are poorly understood. The bacterium promotes dissemination by producing molecules that trigger specific responses in the infected cells that enhance the movement of bacteria into adjacent uninfected cells;we propose detailed studies into the molecular signaling involved in the dissemination of Shigella through tissue. Our results could lead to an improved understanding of how pathogens interact with human tissue and the development of better therapeutics.
|Russo, Brian C; Stamm, Luisa M; Raaben, Matthijs et al. (2016) Intermediate filaments enable pathogen docking to trigger type 3 effector translocation. Nat Microbiol 1:16025|
|Lee, Soo Young; Gertler, Frank B; Goldberg, Marcia B (2015) Vasodilator-stimulated phosphoprotein restricts cell-to-cell spread of Shigella flexneri at the cell periphery. Microbiology 161:2149-60|
|Garza-Mayers, Anna Cristina; Miller, Kelly A; Russo, Brian C et al. (2015) Shigella flexneri regulation of ARF6 activation during bacterial entry via an IpgD-mediated positive feedback loop. MBio 6:e02584|
|Lu, Richard; Herrera, Bobby Brooke; Eshleman, Heather D et al. (2015) Shigella Effector OspB Activates mTORC1 in a Manner That Depends on IQGAP1 and Promotes Cell Proliferation. PLoS Pathog 11:e1005200|
|Yi, Chae-ryun; Allen, John E; Russo, Brian et al. (2014) Systematic analysis of bacterial effector-postsynaptic density 95/disc large/zonula occludens-1 (PDZ) domain interactions demonstrates Shigella OspE protein promotes protein kinase C activation via PDLIM proteins. J Biol Chem 289:30101-13|
|Baxt, Leigh A; Goldberg, Marcia B (2014) Host and bacterial proteins that repress recruitment of LC3 to Shigella early during infection. PLoS One 9:e94653|
|Baxt, Leigh A; Garza-Mayers, Anna Cristina; Goldberg, Marcia B (2013) Bacterial subversion of host innate immune pathways. Science 340:697-701|
|Huett, Alan; Heath, Robert J; Begun, Jakob et al. (2012) The LRR and RING domain protein LRSAM1 is an E3 ligase crucial for ubiquitin-dependent autophagy of intracellular Salmonella Typhimurium. Cell Host Microbe 12:778-90|
|Jehl, Stephanie P; Doling, Amy M; Giddings, Kara S et al. (2011) Antigen-specific CD8(+) T cells fail to respond to Shigella flexneri. Infect Immun 79:2021-30|
|Stamm, Luisa M; Goldberg, Marcia B (2011) Microbiology. Establishing the secretion hierarchy. Science 331:1147-8|
Showing the most recent 10 out of 16 publications