Dataset Information

Legionella pneumophila regulates the activity of UBE2N by deamidase-mediated deubiquitination.

ABSTRACT: The Legionella pneumophila effector MavC induces ubiquitination of the E2 ubiquitin-conjugating enzyme UBE2N by transglutamination, thereby abolishing its function in the synthesis of K₆₃ -type polyubiquitin chains. The inhibition of UBE2N activity creates a conundrum because this E2 enzyme is important in multiple signaling pathways, including some that are important for intracellular L. pneumophila replication. Here, we show that prolonged inhibition of UBE2N activity by MavC restricts intracellular bacterial replication and that the activity of UBE2N is restored by MvcA, an ortholog of MavC (50% identity) with ubiquitin deamidase activity. MvcA functions to deubiquitinate UBE2N-Ub using the same catalytic triad required for its deamidase activity. Structural analysis of the MvcA-UBE2N-Ub complex reveals a crucial role of the insertion domain in MvcA in substrate recognition. Our study establishes a deubiquitination mechanism catalyzed by a deamidase, which, together with MavC, imposes temporal regulation of the activity of UBE2N during L. pneumophila infection.

SUBMITTER: Gan N

PROVIDER: S-EPMC7024838 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Legionella pneumophila regulates the activity of UBE2N by deamidase-mediated deubiquitination.

Gan Ninghai N Guan Hongxin H Huang Yini Y Yu Ting T Fu Jiaqi J Nakayasu Ernesto S ES Puvar Kedar K Das Chittaranjan C Wang Dongmei D Ouyang Songying S Luo Zhao-Qing ZQ

The EMBO journal 20191211 4

The Legionella pneumophila effector MavC induces ubiquitination of the E2 ubiquitin-conjugating enzyme UBE2N by transglutamination, thereby abolishing its function in the synthesis of K<sub>63</sub> -type polyubiquitin chains. The inhibition of UBE2N activity creates a conundrum because this E2 enzyme is important in multiple signaling pathways, including some that are important for intracellular L. pneumophila replication. Here, we show that prolonged inhibition of UBE2N activity by MavC restri ...[more]

PMID: 31825121

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Project description:Legionella pneumophila is an important opportunistic pathogen for which environmental reservoirs are crucial for the infection of humans. In the environment, free-living amoebae represent key hosts providing nutrients and shelter for highly efficient intracellular proliferation of L. pneumophila, which eventually leads to lysis of the protist. However, the significance of other bacterial players for L. pneumophila ecology is poorly understood. In this study, we used a ubiquitous amoeba and bacterial endosymbiont to investigate the impact of this common association on L. pneumophila infection. We demonstrate that L. pneumophila proliferation was severely suppressed in Acanthamoeba castellanii harboring the chlamydial symbiont Protochlamydia amoebophila The amoebae survived the infection and were able to resume growth. Different environmental amoeba isolates containing the symbiont were equally well protected as different L. pneumophila isolates were diminished, suggesting ecological relevance of this symbiont-mediated defense. Furthermore, protection was not mediated by impaired L. pneumophila uptake. Instead, we observed reduced virulence of L. pneumophila released from symbiont-containing amoebae. Pronounced gene expression changes in the presence of the symbiont indicate that interference with the transition to the transmissive phase impedes the L. pneumophila infection. Finally, our data show that the defensive response of amoebae harboring P. amoebophila leaves the amoebae with superior fitness reminiscent of immunological memory. Given that mutualistic associations between bacteria and amoebae are widely distributed, P. amoebophila and potentially other amoeba endosymbionts could be key in shaping environmental survival, abundance, and virulence of this important pathogen, thereby affecting the frequency of human infection.IMPORTANCE Bacterial pathogens are generally investigated in the context of disease. To prevent outbreaks, it is essential to understand their lifestyle and interactions with other microbes in their natural environment. Legionella pneumophila is an important human respiratory pathogen that survives and multiplies in biofilms or intracellularly within protists, such as amoebae. Importantly, transmission to humans occurs from these environmental sources. Legionella infection generally leads to rapid host cell lysis. It was therefore surprising to observe that amoebae, including fresh environmental isolates, were well protected during Legionella infection when the bacterial symbiont Protochlamydia amoebophila was also present. Legionella was not prevented from invading amoebae but was impeded in its ability to develop fully virulent progeny and were ultimately cleared in the presence of the symbiont. This study highlights how ecology and virulence of an important human pathogen is affected by a defensive amoeba symbiont, with possibly major consequences for public health.

Project description:Vacuolar bacterial pathogens are sheltered within unique membrane-bound organelles that expand over time to support bacterial replication. These compartments sequester bacterial molecules away from host cytosolic immunosurveillance pathways that induce antimicrobial responses. The mechanisms by which the human pulmonary pathogen Legionella pneumophila maintains niche homeostasis are poorly understood. We uncovered that the Legionella-containing vacuole (LCV) required a sustained supply of host lipids during expansion. Lipids shortage resulted in LCV rupture and initiation of a host cell death response, whereas excess of host lipids increased LCVs size and housing capacity. We found that lipids uptake from serum and de novo lipogenesis are distinct redundant supply mechanisms for membrane biogenesis in Legionella-infected macrophages. During infection, the metabolic checkpoint kinase Mechanistic Target of Rapamycin (MTOR) controlled lipogenesis through the Serum Response Element Binding Protein 1 and 2 (SREBP1/2) transcription factors. In Legionella-infected macrophages a host-driven response that required the Toll-like receptors (TLRs) adaptor protein Myeloid differentiation primary response gene 88 (Myd88) dampened MTOR signaling which in turn destabilized LCVs under serum starvation. Inactivation of the host MTOR-suppression pathway revealed that L. pneumophila sustained MTOR signaling throughout its intracellular infection cycle by a process that required the upstream regulator Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) and one or more Dot/Icm effector proteins. Legionella-sustained MTOR signaling facilitated LCV expansion and inhibition of the PI3K-MTOR-SREPB1/2 axis through pharmacological or genetic interference or by activation of the host MTOR-suppression response destabilized expanding LCVs, which in turn triggered cell death of infected macrophages. Our work identified a host metabolic requirement for LCV homeostasis and demonstrated that L. pneumophila has evolved to manipulate MTOR-dependent lipogenesis for optimal intracellular replication.

Dataset Information

Legionella pneumophila regulates the activity of UBE2N by deamidase-mediated deubiquitination.

Publications

Legionella pneumophila regulates the activity of UBE2N by deamidase-mediated deubiquitination.

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