Salmonella enteritidis Rck‐mediated invasion requires activation of Rac1, which is dependent on the class I PI 3‐kinases‐Akt signaling pathway

• Published in: The FASEB journal 2012-04, Vol.26 (4), p.1569-1581
• Main Authors: Mijouin, Lily, Rosselin, Manon, Bottreau, Elisabeth, Pizarro‐Cerda, Javier, Cossart, Pascale, Velge, Philippe, Wiedemann, Agnès
• Format: Article
• Language: English
• Subjects: Animals; bacterial internalization; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Bacteriology; Cell Line; Cells, Cultured; Escherichia coli - genetics; Escherichia coli - metabolism; Humans; Life Sciences; Mice; Microbiology and Parasitology; Phosphatidylinositol 3-Kinases - genetics; Phosphatidylinositol 3-Kinases - metabolism; phosphoinositides; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; rac1 GTP-Binding Protein - genetics; rac1 GTP-Binding Protein - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Salmonella enteritidis; Salmonella enteritidis - cytology; Salmonella enteritidis - metabolism; Salmonella enteritidis - pathogenicity; Signal Transduction - physiology
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.11-189647

The Salmonella outer membrane protein Rck mediates a Zipper‐like entry mechanism controlled by Rac, the Arp2/3 complex, and actin polymerization. However, little is known about the early steps leading to Rac activation and Rck‐mediated internalization. The use of pharmacological inhibitors or PI 3‐kinase dominant‐negative mutant induced more than 80% less invasion without affecting attachment. Moreover, Rck‐mediated internalization caused an increase in the association of p85 with at least one tyrosine‐phosphorylated protein, indicating that class I PI 3‐kinase activity was stimulated. We also report that this PI 3‐kinase activity is essential for Rac1 activation. However, Rac recruitment at the Rck‐mediated entry site was independent of its activation. Using a pharmacological approach or Akt‐knockout cells, we also demonstrated that Akt was phosphorylated in response to Rck‐mediated internalization as demonstrated by immunoblotting analysis and that all three Akt isoforms were required during this process. Overall, our results describe a signaling pathway involving tyrosine phosphorylation, class I PI 3‐kinase, Akt activation, and Rac activation, leading to Rck‐dependent Zipper entry. The specificity of this signaling pathway with regard to that of the type 3 secretion system, which is the other invasion process of Salmonella, is discussed.—Mijouin, L., Rosselin, M., Bottreau, E., Pizarro‐Cerda, J., Cossart, P., Velge, P., Wiedemann, A. Salmonella enteritidis Rck‐mediated invasion requires activation of Rac1, which is dependent on the class I PI 3‐kinasesAkt signaling pathway. FASEB J. 26, 1569‐1581 (2012). www.fasebj.org