title: Shigella flexneri DegP facilitates IcsA surface expression and is required for efficient intercellular spread.
abstract: A degP mutant of Shigella flexneri was identified in a screen for insertion mutants that invaded cultured cells but did not form wild-type plaques in monolayers. The degP mutant SM1100 invaded Henle cells at wild-type levels and induced apoptosis in macrophages but formed smaller plaques than those formed by wild-type S. flexneri in confluent monolayers of Henle and Caco-2 cells. The proportion of SM1100 bacteria with IcsA localized to the bacterial pole, a process required for actin polymerization into actin "tails," was reduced compared to results with wild-type bacteria. The reduction in proper IcsA localization may account for the reduced plaque size of the degP mutant. Although DegP is a protease, the protease activity of S. flexneri DegP was not required for IcsA localization or the formation of plaques in Henle cell monolayers. DegP was also required for efficient polar IcsA localization in E. coli expressing icsA. In addition, the growth or survival of SM1100 was compromised compared to that of the wild type at elevated temperatures and in acidic conditions.
authors.affiliation: Institute for Cellular and Molecular Biology and Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Georgiana E
authors.initials: GE
authors.lastname: Purdy
authors.forename: Mei
authors.initials: M
authors.lastname: Hong
authors.forename: Shelley M
authors.initials: SM
authors.lastname: Payne
mesh_terms: D000199:Actins / Q000737:chemistry; D001426:Bacterial Proteins; D018938:Caco-2 Cells; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000502:physiology*; D006801:Humans; D018384:Oxidative Stress; D033903:Periplasmic Proteins / Q000502:physiology*; D012697:Serine Endopeptidases / Q000502:physiology*; D012763:Shigella flexneri / Q000378:metabolism / Q000472:pathogenicity*; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism*; D014774:Virulence
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; D014157:Transcription Factors; C058483:virG protein, Shigella flexneri; C061682:DegP protease; D012697:Serine Endopeptidases