A functional screen for ubiquitin regulation identifies an E3 ligase secreted by .

Ubiquitin signaling controls many aspects of eukaryotic biology, including targeted protein degradation and immune defense. Remarkably, invading bacterial pathogens have adapted secreted effector proteins that hijack host ubiquitination to gain control over host responses. These ubiquitin-targeted effectors can exhibit, for example, E3 ligase or deubiquitinase activities, often without any sequence or structural homology to eukaryotic ubiquitin regulators.

Interplay between septins and ubiquitin-mediated xenophagy during entrapment.

Septins are cytoskeletal proteins implicated in numerous cellular processes including cytokinesis and morphogenesis. In the case of infection by , septins assemble into cage-like structures that entrap cytosolic bacteria targeted by autophagy. The interplay between septin cage entrapment and bacterial autophagy is poorly understood.

Septins and K63 ubiquitin chains are present in separate bacterial microdomains during autophagy of entrapped Shigella.

During host cell invasion, Shigella escapes to the cytosol and polymerizes actin for cell-to-cell spread. To restrict cell-to-cell spread, host cells employ cell-autonomous immune responses including antibacterial autophagy and septin cage entrapment. How septins interact with the autophagy process to target Shigella for destruction is poorly understood.