title: Interaction of the Salmonella Typhimurium effector protein SopB with host cell Cdc42 is involved in intracellular replication.
abstract: The phosphoinositide phosphatase SopB/SigD is a type III secretion system effector that plays multiple roles in Salmonella internalization and intracellular survival. We previously reported that SopB complexed with and inhibited the small GTPase Cdc42 when expressed in a yeast model system, independently of its phosphatase activity. Here we show that human Cdc42, but not Rac1, interacts with catalytically inactive SopB when coexpressed in Saccharomyces cerevisiae. This interaction occurs with both constitutively active and non-activatable Cdc42, suggesting that SopB binds Cdc42 independently of its activation state. By mutational analysis we have narrowed the Cdc42-interacting region of SopB to the first 142 amino acids, and isolated a collection of point mutations in this region, mainly affecting leucine residues conserved in the related Shigella IpgD protein. Such mutations yielded SopB unable to interact with Cdc42 but maintained phosphatase activity. SopB mutant proteins defective for binding Cdc42 were ubiquitinated upon translocation in mammalian cells, but their localization to the Salmonella-containing vacuole was reduced compared with wild-type SopB. Whereas invasion of mammalian cells by Salmonella bearing these sopB mutations was not affected, intracellular replication was less efficient, suggesting that SopB-Cdc42 interaction contributes to the adaptation of Salmonella to the intracellular environment.
authors: Departamento de Microbiología II, Universidad Complutense de Madrid, and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Plaza de Ramón y Cajal s/n, 28040-Madrid, Spain.
authors: Isabel
authors: I
authors: Rodríguez-Escudero
authors: Nadia L
authors: NL
authors: Ferrer
authors: Rafael
authors: R
authors: Rotger
authors: Víctor J
authors: VJ
authors: Cid
authors: María
authors: M
authors: Molina
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004261:DNA Replication; D054884:Host-Pathogen Interactions; D006801:Humans; D011485:Protein Binding; D012480:Salmonella Infections / Q000201:enzymology* / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C489224:SopB protein, Salmonella; D020764:cdc42 GTP-Binding Protein