RNF213-dependent lytic destruction of Chlamydia-containing vacuoles activates host cell death pathways.

The cytokine gamma-interferon promotes antimicrobial cell-autonomous immunity by inducing hundreds of interferon-stimulated genes (ISGs). Among these ISGs is the ubiquitin E3 ligase RNF213 which protects host cells from a wide range of intracellular pathogens including the obligate intracellular bacterium Chlamydia. The human pathogen Chlamydia trachomatis normally employs its secreted virulence effector GarD to evade RNF213-mediated killing. However, in the absence of GarD, RNF213 is recruited to the vacuolar compartment in which C. trachomatis replicates, called the inclusion. Once localized to inclusions, RNF213 ubiquitylates unknown substrates associated with the inclusion membrane and eliminates C. trachomatis through mechanisms that are not yet defined. Ubiquitylation of pathogen-containing vacuoles often results in xenophagy, an autophagy-related defense program. Here, we show that although inclusions can be degraded via xenophagy, this pathway is dispensable for RNF213-dependent inhibition of C. trachomatis replication. In addition to xenophagy, we find that RNF213 targeting can lead to antimicrobial inclusion lysis, thereby releasing bacteria into the host cell cytosol and triggering host cell death. Two cell death pathways occur downstream from RNF213-dependent inclusion rupture: a rapid cell death that despite its apoptosis-like morphology occurs independent of the apoptosis effectors caspase-3 and caspase-7 and instead requires the secreted C. trachomatis protease CPAF, and a slow cell death that is independent of CPAF and instead requires the cytosolic proinflammatory pattern-recognition receptors RIG-I or STING. Thus, RNF213-driven lysis of pathogen-containing vacuoles represents a previously unrecognized mechanism by which RNF213 mediates host defense and triggers a host-pathogen battle over cytosolic immune activation.