| 1. |
- Husler, Dario, et al.
(författare)
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Dictyostelium lacking the single atlastin homolog Sey1 shows aberrant ER architecture, proteolytic processes and expansion of the Legionella-containing vacuole
- 2021
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Ingår i: Cellular Microbiology. - : WILEY. - 1462-5814 .- 1462-5822. ; 23:5
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Tidskriftsartikel (refereegranskat)abstract
- Dictyostelium discoideum Sey1 is the single ortholog of mammalian atlastin 1-3 (ATL1-3), which are large homodimeric GTPases mediating homotypic fusion of endoplasmic reticulum (ER) tubules. In this study, we generated a D. discoideum mutant strain lacking the sey1 gene and found that amoebae deleted for sey1 are enlarged, but grow and develop similarly to the parental strain. The increment sey1 mutant amoebae showed an altered ER architecture, and the tubular ER network was partially disrupted without any major consequences for other organelles or the architecture of the secretory and endocytic pathways. Macropinocytic and phagocytic functions were preserved; however, the mutant amoebae exhibited cumulative defects in lysosomal enzymes exocytosis, intracellular proteolysis, and cell motility, resulting in impaired growth on bacterial lawns. Moreover, increment sey1 mutant cells showed a constitutive activation of the unfolded protein response pathway (UPR), but they still readily adapted to moderate levels of ER stress, while unable to cope with prolonged stress. In D. discoideum increment sey1 the formation of the ER-associated compartment harbouring the bacterial pathogen Legionella pneumophila was also impaired. In the mutant amoebae, the ER was less efficiently recruited to the "Legionella-containing vacuole" (LCV), the expansion of the pathogen vacuole was inhibited at early stages of infection and intracellular bacterial growth was reduced. In summary, our study establishes a role of D. discoideum Sey1 in ER architecture, proteolysis, cell motility and intracellular replication of L. pneumophila.
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| 2. |
- Striednig, Bianca, et al.
(författare)
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Quorum sensing governs a transmissive Legionella subpopulation at the pathogen vacuole periphery
- 2021
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Ingår i: EMBO Reports. - : Wiley-Blackwell. - 1469-221X .- 1469-3178. ; 22:9
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Tidskriftsartikel (refereegranskat)abstract
- The Gram-negative bacterium Legionella pneumophila is the causative agent of Legionnaires disease and replicates in amoebae and macrophages within a distinct compartment, the Legionella-containing vacuole (LCV). The facultative intracellular pathogen switches between a replicative, non-virulent and a non-replicating, virulent/transmissive phase. Here, we show on a single-cell level that at late stages of infection, individual motile (P-flaA-GFP-positive) and virulent (P-ralF- and P-sidC-GFP-positive) L. pneumophila emerge in the cluster of non-growing bacteria within an LCV. Comparative proteomics of P-flaA-GFP-positive and P-flaA-GFP-negative L. pneumophila subpopulations reveals distinct proteomes with flagellar proteins or cell division proteins being preferentially produced by the former or the latter, respectively. Toward the end of an infection cycle (similar to 48 h), the P-flaA-GFP-positive L. pneumophila subpopulation emerges at the cluster periphery, predominantly escapes the LCV, and spreads from the bursting host cell. These processes are mediated by the Legionella quorum sensing (Lqs) system. Thus, quorum sensing regulates the emergence of a subpopulation of transmissive L. pneumophila at the LCV periphery, and phenotypic heterogeneity underlies the intravacuolar bi-phasic life cycle of L. pneumophila.
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