Cell type-specific effects ofYersinia pseudotuberculosisvirulence effectors

Abstract

SummaryOne important feature of Yersinia pseudotuberculosis that enables resistance against the host immune defence is delivery of the antiphagocytic effectors YopH and YopE into phagocytic cells. The tyrosine phosphatase YopH influences integrin signalling, and YopE impairs cytoskeletal dynamics by inactivating Rho GTPases. Here, we report the impact of these effectors on internalization by dendritic cells (DCs), which internalize antigens to orchestrate host immune responses. We found that this pathogen resists internalization by DCs via YopE. YopH that is important for blocking phagocytosis by macrophages and neutrophils and which is also present inside the DCs does not contribute to the resistance. However, the YopH targets Fyb and p130Cas show higher expression levels in macrophages than in DCs. Furthermore, live cell microscopy revealed that the cells internalize Y. pseudotuberculosis in different ways: the macrophages utilize a locally restricted receptormediated zipper mechanism, whereas DCs utilize macropinocytosis involving constitutive ruffling that randomly catches bacteria into membrane folds. We conclude that YopH impacts early phagocytic signalling from the integrin receptor to which the bacterium binds and that this tight receptormediated stimulation is absent in DC macropinocytosis. Inactivation of cytoskeletal dynamics by YopE affects ruffling activity and hence also internalization. The different modes of internalization can be coupled to the major functions of these respective cell types: elimination by phagocytosis and antigen sampling.

Yersinia pseudotuberculosis Blocks Neutrophil Degranulation

“…It is therefore likely that the virulence effectors translocated by the wild-type strain act on immediate early signals emanating from receptors that have bound bacteria at the neutrophil surface. This is a situation analogous to that shown previously for the YopH-mediated blockade of macrophage and neutrophil internalization (28,29,35,44). Both YopH and YopE are major effectors responsible for blocking phagocytic uptake (28,45,46).…”

“…Bacterial suspensions of Y. pseudotuberculosis strains were washed and resuspended to 2 ϫ 10 7 bacteria/ml in KRG and then incubated with neutrophils at an MOI of 30 and different incubation times at RT. Internalization of bacteria was inhibited by pretreatment of neutrophils with 1 M cytochalasin D for 15 min at RT prior to infection (35). Nonadherent bacteria were removed by PBS washes, and then cells were fixed in 4% paraformaldehyde in PBS for 10 min at RT.…”

Yersinia pseudotuberculosis Efficiently Escapes Polymorphonuclear Neutrophils during Early Infection

“…YopH interrupts early signaling events from the phagocytic receptor, while YopE blocks actin dynamics. In contrast, blocking internalization by DCs requires only YopE, a phenomenon that can be explained by the fact that these cells do not use strictly receptor mediated mechanisms for the internalization of antigens (21). Antiphagocytosis is likely an essential virulence mechanism of Yersinia, and virulence studies in mice further support this hypothesis, since yopH and yopE single mutants are cleared at early stages of infection (25).…”

Different Bacterial Pathogens, Different Strategies, Yet the Aim Is the Same: Evasion of Intestinal Dendritic Cell Recognition

“…Of note, other members of the Yersinia genus also appear to have developed special strategies to interact with DCs. For example, Y. pestis, the infamous causative agent of the plague, has been shown to infect DCs (62), whereas Y. pseudotuberculosis uses YopE to circumvent phagocytosis by DCs (63). Thus, direct inhibition of the ability of DCs to present Ag represents another interesting evasion strategy used by intestinal bacterial pathogens (Fig.…”