Src tyrosine kinase activity down-regulates Rho-dependent responses during Shigella entry into epithelial cells and stress fibre formation

• Published in: Journal of cell science Vol. 113 ( Pt 1); no. 1; pp. 71 - 80
• Main Authors: Duménil, G, Sansonetti, P, Tran Van Nhieu, G
• Format: Journal Article
• Language: English
• Published: England 01-01-2000
• Subjects: Actins - metabolism; ADP Ribose Transferases - administration & dosage; ADP Ribose Transferases - metabolism; Biopolymers; Botulinum Toxins; cdc42 GTP-Binding Protein - metabolism; Cytoskeletal Proteins; Cytoskeleton - drug effects; Cytoskeleton - metabolism; Down-Regulation; Enzyme Activation; Epithelial Cells - cytology; Epithelial Cells - drug effects; Epithelial Cells - enzymology; Epithelial Cells - microbiology; GTPase-Activating Proteins; Guanine Nucleotide Exchange Factors; HeLa Cells; Humans; Lysophospholipids - pharmacology; Nuclear Proteins - metabolism; Phosphoproteins - metabolism; Phosphorylation; Protein Binding; rac GTP-Binding Proteins - metabolism; Repressor Proteins; rho GTP-Binding Proteins - administration & dosage; rho GTP-Binding Proteins - antagonists & inhibitors; rho GTP-Binding Proteins - metabolism; Shigella flexneri - physiology; Signal Transduction; src-Family Kinases - genetics; src-Family Kinases - metabolism; Transfection
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.113.1.71

Invasion of epithelial cells by Shigella, the causative agent of bacillary dysentery, is dependent upon the formation of characteristic membrane ruffles that engulf the bacteria in a macropinocytic-like process. We show here that Cdc42 and Rac GTPases, but not Rho;, are critical for actin polymerisation, whereas Rho; is necessary for the recruitment of ezrin and Src at the site of entry. Remarkably, cells expressing constitutively active Src did not show ezrin recruitment at Shigella entry foci. In these cells, formation of stress fibres induced by LPA stimulation, or microinjection of activated Rho; (V14Rho), was inhibited. Src-mediated tyrosyl-phosphorylation of p190RhoGAP correlated with changes in the ability of p190RhoGAP to interact with Rho;, suggesting that Src regulates Rho; function via p190RhoGAP. We propose that Rho; activation is required for proper organisation of Shigella entry foci and for Src recruitment, and that Src tyrosine kinase activity, in turn, down-regulates the function of Rho; at the site of Shigella entry. The significance of this negative regulatory loop on Rho;-dependent responses is discussed.