title: Secretion of type III effectors into host cells in real time.
abstract: Type III secretion (T3S) systems are key features of many gram-negative bacteria that translocate T3S effector proteins directly into eukaryotic cells. There, T3S effectors exert many effects, such as cellular invasion or modulation of host immune responses. Studying spatiotemporal orchestrated secretion of various effectors has been difficult without disrupting their functions. Here we developed a new approach using Shigella flexneri T3S as a model to investigate bacterial translocation of individual effectors via multidimensional time-lapse microscopy. We demonstrate that direct fluorescent labeling of tetracysteine motif-tagged effectors IpaB and IpaC is possible in situ without loss of function. Studying the T3S kinetics of IpaB and IpaC ejection from individual bacteria, we found that the entire pools of IpaB and IpaC were released concurrently upon host cell contact, and that 50% of each effector was secreted in 240 s. This method allows an unprecedented analysis of the spatiotemporal events during T3S.
authors.affiliation: INSERM U389, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France. jostenn@pasteur.fr
authors.forename: Jost
authors.initials: J
authors.lastname: Enninga
authors.forename: Joëlle
authors.initials: J
authors.lastname: Mounier
authors.forename: Philippe
authors.initials: P
authors.lastname: Sansonetti
authors.forename: Guy
authors.initials: G
authors.lastname: Tran Van Nhieu
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D018715:Microscopy, Video / Q000379:methods; D021381:Protein Transport; D012763:Shigella flexneri / Q000378:metabolism* / Q000472:pathogenicity*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D005456:Fluorescent Dyes; C087447:ipaB protein, Shigella; C092342:IpaC protein, Shigella; D003545:Cysteine