Analysis of the mechanisms of Salmonella-induced actin assembly during invasion of host cells and intracellular replication.
Salmonella enterica serovar Typhimurium (S. typhimurium) induces actin assembly both during invasion of host cells and during the course of intracellular bacterial replication. In this study, we investigated the involvement in these processes of host cell signalling pathways that are frequently utilized by bacterial pathogens to manipulate the eukaryotic actin cytoskeleton. We confirmed that Cdc42, Rac, and Arp3 are involved in S. typhimurium invasion of HeLa cells, and found that N-WASP and Scar/WAVE also play a role in this process. However, we found no evidence for the involvement of these proteins in actin assembly during intracellular replication. Cortactin was recruited by Salmonella during both invasion and intracellular replication. However, RNA interference directed against cortactin did not inhibit either invasion or intracellular actin assembly, although it resulted in increased cell spreading and a greater number of lamellipodia. We also found no role for either the GTPase dynamin or the formin family member mDia1 in actin assembly by intracellular bacteria. Collectively, these data provide evidence that signalling pathways leading to Arp2/3-dependent actin nucleation play an important role in S. typhimurium invasion, but are not involved in intracellular Salmonella-induced actin assembly, and suggest that actin assembly by intracellular S. typhimurium may proceed by a novel mechanism.
Centre for Molecular Microbiology and Infection, Department of Infectious Diseases, Imperial College London, Armstrong Road, London SW7 2AZ, UK.
Kate E
KE
Unsworth
Michael
M
Way
Mark
M
McNiven
Laura
L
Machesky
David W
DW
Holden
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012486:Salmonella typhimurium / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology*; D051300:Wiskott-Aldrich Syndrome Protein Family; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal
C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; C440638:SPI-2 protein, Salmonella; C114864:WASF1 protein, human; C495771:WASL protein, human; D051300:Wiskott-Aldrich Syndrome Protein Family; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D019204:GTP-Binding Proteins