Abstract
Shigella, the causative agent of bacillary dysentery, invades epithelial cells by locally reorganizing the actin cytoskeleton. Shigella invasion requires actin polymerization dependent on the Src tyrosine kinase and a functional bacterial type III secretion (T3S) apparatus. Using dynamic as well as immunofluorescence microscopy, we show that the T3S translocon component IpaC allows the recruitment of the Src kinase required for actin polymerization at bacterial entry sites during the initial stages of Shigella entry. Src recruitment occurred at bacterial-cell contact sites independent of actin polymerization at the onset of the invasive process and was still observed in Shigella strains mutated for translocated T3S effectors of invasion. A Shigella strain with a polar mutation that expressed low levels of the translocator components IpaB and IpaC was fully proficient for Src recruitment and bacterial invasion. In contrast, a Shigella strain mutated in the IpaC carboxyterminal effector domain that was proficient for T3S effector translocation did not induce Src recruitment. Consistent with a direct role for IpaC in Src activation, cell incubation with the IpaC last 72 carboxyterminal residues fused to the Iota toxin Ia (IaC) component that translocates into the cell cytosol upon binding to the Ib component led to Src-dependent ruffle formation. Strikingly, IaC also induced actin structures resembling bacterial entry foci that were enriched in activated Src and were inhibited by the Src inhibitor PP2. These results indicate that the IpaC effector domain determines Src-dependent actin polymerization and ruffle formation during bacterial invasion.
Highlights
Shigella, the causative agent of bacillary dysentery, uses a T3S apparatus to invade epithelial cells [1,2]
Src is recruited early during Shigella invasion To gain insights into the relationship between Src and bacterial induced actin-polymerization, we analyzed the kinetics of Src recruitment during the early phases of bacterial invasion
Src was found recruited at the intimate bacterial contact site inside host cells without detectable pY416 staining (Figure 1C, arrows), suggesting that Src activation occurs transiently at the levels of bacterial-induced entry foci
Summary
The causative agent of bacillary dysentery, uses a T3S apparatus to invade epithelial cells [1,2]. Bacterial T3S systems, allow the targeting of bacterial pathogenic effectors into the cell cytosol that may potentially bypass membrane signaling [2,11]. These secretion devices share similar structural and functional features and are widespread among gram-negative pathogens. Pathogen-mediated reorganization of the host cell cytoskeleton may occur through translocated effectors that target RhoGTPases, as observed for Salmonella or Yersinia, or by inducing tyrosine kinase signaling at the membrane in the case EPEC or viruses such as vaccinia [10,11,14,15].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
