Subversion of GBP-mediated host defense by E3 ligases acquired during Yersinia pestis evolution.

Plague has caused three worldwide pandemics in history, including the Black Death in medieval ages. Yersinia pestis, the etiological agent of plague, has evolved a powerful arsenal to disrupt host immune defenses during evolution from enteropathogenic Y. pseudotuberculosis. Here, we find that two functionally redundant E3 ligase of Y. pestis, YspE1 and YspE2, can be delivered via type III secretion injectisome into host cytosol where they ubiquitinate multiple guanylate-binding proteins (GBPs) for proteasomal degradation. However, Y. pseudotuberculosis has no such capability due to lacking functional YspE1/2 homologs. YspE1/2-mediated GBP degradations significantly promote the survival of Y. pestis in macrophages and strongly inhibit inflammasome activation. By contrast, Gbpchr3-/-, chr5-/- macrophages exhibit much lowered inflammasome activation independent of YspE1/2, accompanied with an enhanced replication of Y. pestis. Accordingly, Gbpchr3-/-, chr5-/- mice are more susceptible to Y. pestis. We demonstrate that Y. pestis utilizes E3 ligases to subvert GBP-mediated host defense, which appears to be newly acquired by Y. pestis during evolution.