Project P2

P2 – Interplay between Yersinia enterocolitica and the autophagosomal/lysosomal system in epithelial host cells and organoids

Project Summary

Project Ruckdeschel Group: Yersinia enterocolitica engages a cell-invasive strategy to colonize the host intestinal tissue. The intracellular, invasive phenotype depends on the Yersinia outer membrane protein invasin which binds and activates eukaryotic beta-1-integrin receptors to promote uptake of the bacteria into infected host cells. Our previous studies have shown that internalization of Yersinia by epithelial cells results in the formation of two distinct populations of intravacuolar bacteria. One part of the ingested bacteria is subjected to the endosomal / phagolysosomal pathway in which the Yersinia-containing vacuoles (YCVs) fuse with lysosomes and the enclosed bacteria are eliminated. The second half of the bacteria ends up in vacuoles with autophagy-related characteristics, displaying recruitment of autophagosomes, phagophore formation, and xenophagy. Importantly, fusion of these autophagic vacuoles with lysosomes is actively prevented by Yersinia which results in intracellular survival and proliferation of Yersinia in the non-acidified, autophagic compartments. This indicates that Y. enterocolitica takes advantage of the macroautophagy pathway to gain access to an intracellular niche that enables bacterial replication in a protected compartment. Eventually, this leads to bacterial egress from the infected cells. The molecular mechanisms that direct Yersinia to autophagosomes and prevent fusion with lysosomes are, however, presently unclear.

Our project consequently aims to explore the intracellular lifestyle of Yersinia in order to uncover novel principles in bacterial pathogenesis and in the regulation of vesicle function and trafficking pathways in infected epithelial host cells. The autophagosomal and lysosomal pathways to which Yersinia is sorted are differentially characterized by proteomic and co-localization studies. Furthermore, the Yersinia factors that manipulate the physiological endocytic-lysosomal pathway are investigated by evaluating a transposon-based Yersinia mutation library. Functional approaches in molecularly modified host cells will then specify the roles of the identified pathways for Yersinia survival, replication and release from infected cells. We expect the results of this work to be of general importance for cell and human infection biology.

References

Valencia Lopez MJ, Schimmeck H, Gropengießer J, Middendorf L, Quitmann M, Schneider C, Holstermann B, Wacker R, Heussler V, Reimer R, Aepfelbacher M, Ruckdeschel K (2019) Activation of the macroautophagy pathway by Yersinia enterocolitica promotes intracellular multiplication and egress of yersiniae from epithelial cells. Cell Microbiol 21:e13046. Abstract

Deuretzbacher A, Czymmeck N, Reimer R, Trülzsch K, Gaus K, Hohenberg H, Heesemann J, Aepfelbacher M, Ruckdeschel K (2009) Beta1 integrin-dependent engulfment of Yersinia enterocolitica by macrophages is coupled to the activation of autophagy and suppressed by type III protein secretion. J Immunol 183:5847-60. Abstract