Functional dissection of ARIH1 E3 ubiquitin ligase in cellular antimicrobial immunity
Biochemistry
Cell Biology
Final Report Abstract
The ubiquitin system is an important part of the host cellular defense program during bacterial infection. This is in particular evident for a number of bacteria including Salmonella Typhimurium which - inventively as part of their invasion strategy or accidentally upon rapture of seized host endomembranes – dwell in the host cytosol. Ubiquitination is involved in the detection and clearance of these bacteria as well as in the activation of innate immune and inflammatory signaling. Remarkably, all these defense responses seem to emanate from a dense layer of ubiquitin which coat the invading pathogens. We recently identified the ubiquitin E3 ligase ARIH1 as a novel component of the host cell ubiquitination machinery targeting cytosolic Salmonella. While Ub moieties contributed by ARIH1 seems to have anti-bacterial functions beyond their role as xenophagic eat-me signal, mechanistic insights these processes remained sparse. Therefore, we sought to combine the highly complementary expertise in ARIH1 biochemistry and host-pathogen proteomics of the Alpi and Behrends lab with a range of microbiology tools and cell biology approaches. Together, we aimed at mechanistically dissecting the bacterial recruitment of ARIH1, its activation and the functional consequences of ARIH1 mediated bacterial ubiquitination. Our collaborative approach unveiled that the regulatory Ariadne domain of ARIH1 plays a major role in recruiting ARIH1 to Salmonella-containing vesicles (SCV) which seem to restrict Salmonella hyper proliferation. However, during SCV rapture and xenophagic capturing of cytosolic bacteria, ARIH1 colocalizes with Salmonella. Furthermore, we identified the endosomal cargo adaptor and phosphatidylinositol 4,5-biphosphate binding protein CLINT1 as a new Salmonella infection-dependent interaction protein of ARIH1. Future work remains to show whether CLINT1 binds to ARIH1’s Ariadne domain and act as a recruitment factor for Salmonella. Our findings provide the basis to develop novel molecular approaches to manipulate the activity of ARIH1 towards Salmonella and possibly other cytosol dwelling bacterial pathogens, thereby providing an opportunity to drive research on hostpathogen interactions into new directions.
Publications
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The ubiquitin ligation machinery in the defense against bacterial pathogens. EMBO reports, 22(11).
Tripathi‐Giesgen, Ishita; Behrends, Christian & Alpi, Arno F.
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Catalysis of non-canonical protein ubiquitylation by the ARIH1 ubiquitin ligase. Biochemical Journal, 480(22), 1817-1831.
Purser, Nicholas; Tripathi-Giesgen, Ishita; Li, Jerry; Scott, Daniel C.; Horn-Ghetko, Daniel; Baek, Kheewoong; Schulman, Brenda A.; Alpi, Arno F. & Kleiger, Gary
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In situ snapshots along a mammalian selective autophagy pathway. Proceedings of the National Academy of Sciences, 120(12).
Li, Meijing; Tripathi-Giesgen, Ishita; Schulman, Brenda A.; Baumeister, Wolfgang & Wilfling, Florian
