Dedicated bacterial esterases reverse lipopolysaccharide ubiquitylation to block immune sensing.

Pathogenic bacteria have evolved diverse mechanisms to counteract cell-autonomous immunity, which otherwise guards both immune and non-immune cells from the onset of an infection1,2. The versatile immunity protein Ring finger protein 213 (RNF213)3-6 mediates the non-canonical ester-linked ubiquitylation of lipopolysaccharide (LPS), marking bacteria that sporadically enter the cytosol for destruction by antibacterial autophagy4. However, whether cytosol-adapted pathogens are ubiquitylated on their LPS and whether they escape RNF213-mediated immunity, remains unknown. Here we show that Burkholderia deubiquitylase (DUB), TssM7-9, is a potent esterase that directly reverses the ubiquitylation of LPS. Without TssM, cytosolic Burkholderia became coated in polyubiquitin and autophagy receptors in an RNF213-dependent fashion. Whereas the expression of TssM was sufficient to enable the replication of the non-cytosol adapted pathogen Salmonella, we demonstrate that Burkholderia has evolved a multi-layered defence system to proliferate in the host cell cytosol, including a block in antibacterial autophagy10-12. Structural analysis provided insight into the molecular basis of TssM esterase activity, allowing it to be uncoupled from isopeptidase function. TssM homologs conserved in another Gram-negative pathogen also reversed non-canonical LPS ubiquitylation, establishing esterase activity as a bacterial virulence mechanism to subvert host cell-autonomous immunity.