title: Biogenesis of Salmonella enterica serovar typhimurium membrane vesicles provoked by induction of PagC.
abstract: Gram-negative bacteria ubiquitously release membrane vesicles (MVs) into the extracellular milieu. Although MVs are the product of growing bacteria, not of cell lysis or death, the regulatory mechanisms underlying MV formation remained unknown. We have found that MV biogenesis is provoked by the induction of PagC, a Salmonella-specific protein whose expression is activated by conditions that mimic acidified macrophage phagosomes. PagC is a major constituent of Salmonella MVs, and increased expression accelerates vesiculation. Expression of PagC is regulated at the posttranscriptional and/or posttranslational level in a sigmaS (RpoS)-dependent manner. Serial quantitative analysis has demonstrated that MV formation can accelerate when the quantity of the MV constituents, OmpX and PagC, rises. Overproduction of PagC dramatically impacts the difference in the relative amount of vesiculation, but the corresponding overproduction of OmpX was less pronounced. Quantitative examination of the ratios of PagC and OmpX in the periplasm, outer membrane, and MVs demonstrates that PagC is preferentially enriched in MVs released from Salmonella cells. This suggests that specific protein sorting mechanisms operate when MVs are formed. The possible role(s) of PagC-MV in host cells is discussed.
authors.affiliation: Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kitagawa
authors.forename: Akiko
authors.initials: A
authors.lastname: Takaya
authors.forename: Mai
authors.initials: M
authors.lastname: Ohya
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Mizunoe
authors.forename: Akemi
authors.initials: A
authors.lastname: Takade
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yoshida
authors.forename: Emiko
authors.initials: E
authors.lastname: Isogai
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D049069:ATP-Dependent Proteases / Q000235:genetics / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000502:physiology*; D004790:Enzyme Induction; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000166:cytology / Q000378:metabolism* / Q000472:pathogenicity; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D012808:Sigma Factor; C066766:pagC protein, Salmonella typhimurium; D049069:ATP-Dependent Proteases
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