title: A Genome-Wide siRNA Screen Implicates Spire1/2 in SipA-Driven Salmonella Typhimurium Host Cell Invasion.
abstract: Salmonella Typhimurium (S. Tm) is a leading cause of diarrhea. The disease is triggered by pathogen invasion into the gut epithelium. Invasion is attributed to the SPI-1 type 3 secretion system (T1). T1 injects effector proteins into epithelial cells and thereby elicits rearrangements of the host cellular actin cytoskeleton and pathogen invasion. The T1 effector proteins SopE, SopB, SopE2 and SipA are contributing to this. However, the host cell factors contributing to invasion are still not completely understood. To address this question comprehensively, we used Hela tissue culture cells, a genome-wide siRNA library, a modified gentamicin protection assay and S. TmSipA, a sopBsopE2sopE mutant which strongly relies on the T1 effector protein SipA to invade host cells. We found that S. TmSipA invasion does not elicit membrane ruffles, nor promote the entry of non-invasive bacteria "in trans". However, SipA-mediated infection involved the SPIRE family of actin nucleators, besides well-established host cell factors (WRC, ARP2/3, RhoGTPases, COPI). Stage-specific follow-up assays and knockout fibroblasts indicated that SPIRE1 and SPIRE2 are involved in different steps of the S. Tm infection process. Whereas SPIRE1 interferes with bacterial binding, SPIRE2 influences intracellular replication of S. Tm. Hence, these two proteins might fulfill non-redundant functions in the pathogen-host interaction. The lack of co-localization hints to a short, direct interaction between S. Tm and SPIRE proteins or to an indirect effect.
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule Zurich, CH-8093, Zurich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Andritschke
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule Zurich, CH-8093, Zurich, Switzerland.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Dilling
authors.affiliation: Biozentrum, University of Basel, CH-4056, Basel, Switzerland.
authors.forename: Mario
authors.initials: M
authors.lastname: Emmenlauer
authors.affiliation: Department of Neurology, University of Regensburg, DE- 93040, Regensburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Welz
authors.affiliation: Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zurich, CH-4058, Basel, Switzerland.|SIB Swiss Institute for Bioinformatics, 4058, Basel, Switzerland.
authors.forename: Fabian
authors.initials: F
authors.lastname: Schmich
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule Zurich, CH-8093, Zurich, Switzerland.|Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, CH-8091, Zurich, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Misselwitz
authors.affiliation: Biozentrum, University of Basel, CH-4056, Basel, Switzerland.
authors.forename: Pauli
authors.initials: P
authors.lastname: Rämö
authors.affiliation: Zoological Institute, Technische Universität Braunschweig, D-38106, Braunschweig, Germany.|Department of Cell Biology, Helmholtz Centre for Infection Research, D-38124, Braunschweig, Germany.
authors.forename: Klemens
authors.initials: K
authors.lastname: Rottner
authors.affiliation: Department of Neurology, University of Regensburg, DE- 93040, Regensburg, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Kerkhoff
authors.affiliation: Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030, Vienna, Austria.
authors.forename: Teiji
authors.initials: T
authors.lastname: Wada
authors.affiliation: Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030, Vienna, Austria.
authors.forename: Josef M
authors.initials: JM
authors.lastname: Penninger
authors.affiliation: Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zurich, CH-4058, Basel, Switzerland.|SIB Swiss Institute for Bioinformatics, 4058, Basel, Switzerland.
authors.forename: Niko
authors.initials: N
authors.lastname: Beerenwinkel
authors.affiliation: Light Microscopy Center, Eidgenössische Technische Hochschule Zurich, CH-8093, Zurich, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Horvath
authors.affiliation: Biozentrum, University of Basel, CH-4056, Basel, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehio
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule Zurich, CH-8093, Zurich, Switzerland.
authors.forename: Wolf-Dietrich
authors.initials: WD
authors.lastname: Hardt
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D055106:Genome-Wide Association Study / Q000379:methods*; D006367:HeLa Cells / Q000378:metabolism / Q000382:microbiology; D054884:Host-Pathogen Interactions / Q000502:physiology*; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C000592292:SPIRE1 protein, human; C000608602:SPIRE2 protein, human; C118287:SipA protein, Salmonella