title: The Salmonella effector SteA binds phosphatidylinositol 4-phosphate for subcellular targeting within host cells.
abstract: Many bacterial pathogens use specialized secretion systems to deliver virulence effector proteins into eukaryotic host cells. The function of these effectors depends on their localization within infected cells, but the mechanisms determining subcellular targeting of each effector are mostly elusive. Here, we show that the Salmonella type III secretion effector SteA binds specifically to phosphatidylinositol 4-phosphate [PI(4)P]. Ectopically expressed SteA localized at the plasma membrane (PM) of eukaryotic cells. However, SteA was displaced from the PM of Saccharomyces cerevisiae in mutants unable to synthesize the local pool of PI(4)P and from the PM of HeLa cells after localized depletion of PI(4)P. Moreover, in infected cells, bacterially translocated or ectopically expressed SteA localized at the membrane of the Salmonella-containing vacuole (SCV) and to Salmonella-induced tubules; using the PI(4)P-binding domain of the Legionella type IV secretion effector SidC as probe, we found PI(4)P at the SCV membrane and associated tubules throughout Salmonella infection of HeLa cells. Both binding of SteA to PI(4)P and the subcellular localization of ectopically expressed or bacterially translocated SteA were dependent on a lysine residue near the N-terminus of the protein. Overall, this indicates that binding of SteA to PI(4)P is necessary for its localization within host cells.
authors.affiliation: UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (FCT NOVA), Caparica, Portugal.|Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal.
authors.forename: Lia
authors.initials: L
authors.lastname: Domingues
authors.affiliation: Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), Madrid, Spain.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Ismail
authors.affiliation: UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (FCT NOVA), Caparica, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Charro
authors.affiliation: Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Rodríguez-Escudero
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Holden
authors.affiliation: Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Molina
authors.affiliation: Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid and Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), Madrid, Spain.
authors.forename: Víctor J
authors.initials: VJ
authors.lastname: Cid
authors.affiliation: UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (FCT NOVA), Caparica, Portugal.|Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal.
authors.forename: Luís Jaime
authors.initials: LJ
authors.lastname: Mota
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000382:microbiology; D006367:HeLa Cells / Q000382:microbiology; D054884:Host-Pathogen Interactions / Q000502:physiology*; D006801:Humans; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D012480:Salmonella Infections / Q000378:metabolism / Q000382:microbiology; D012486:Salmonella typhimurium / Q000378:metabolism* / Q000472:pathogenicity; D014617:Vacuoles / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D018129:Phosphatidylinositol Phosphates; D011994:Recombinant Proteins; C000590973:SteA protein, Salmonella typhimurium; D037521:Virulence Factors; C037178:phosphatidylinositol 4-phosphate