Type III secretion translocation pores of Yersinia enterocolitica trigger maturation and release of pro-inflammatory IL-1beta.

Bacteria from the genus Yersinia deliver a number of effectors into host cells via type III secretion (T3S). Injected Yop effectors interfere and prevent pro-inflammatory warning signals by hijacking the host's intracellular machinery. While macrophages infected by wild-type Yersinia enterocolitica did not release mature IL-1beta, macrophages infected by Y. enterocolitica deprived of all effectors released mature IL-1beta. Surprisingly, macrophages infected by Y. enterocolitica deficient for secretion of all T3S proteins, including effectors and translocators, did not release mature IL-1beta. Using different genetic constructs, we show that insertion of T3S translocation pores trigger activation of caspase-1, maturation of proIL-1beta and release of mature IL-1beta, which occurs independently of cell osmotic lysis. These data show that T3S translocation is intrinsically a pro-inflammatory phenomenon. However, in the case of Yersinia, this effect is neutralized by the action of effectors.