Abstract
Ubiquitination is a commonly used post-translational modification (PTM) in eukaryotic cells, which regulates a wide variety of cellular processes, such as differentiation, apoptosis, cell cycle, and immunity. Because of its essential role in immunity, the ubiquitin network is a common target of infectious agents, which have evolved various effective strategies to hijack and co-opt ubiquitin signaling for their benefit. The intracellular pathogen Legionella pneumophila represents one such example; it utilizes a large cohort of virulence factors called effectors to modulate diverse cellular processes, resulting in the formation a compartment called the Legionella-containing vacuole (LCV) that supports its replication. Many of these effectors function to re-orchestrate ubiquitin signaling with distinct biochemical activities. In this review, we highlight recent progress in the mechanism of action of L. pneumophila effectors involved in ubiquitination and discuss their roles in bacterial virulence and host cell biology.
Highlights
Ubiquitin (Ub) is a small, 76-amino acid protein that highly conserved in all eukaryotes (Liu et al, 2013; Shaid et al, 2013)
Whereas the biochemical basis of this catalysis is similar to classical mono-ADP-ribosyltransferase activity (mART) often found in bacterial toxins (Mikolcevic et al, 2021), ADPR-Ub produced by this reaction is utilized by a phosphodiesterase (PDE) activity embedded in each of SidE family member, which cleaves the phosphoanhydride bond between the two phosphate atoms, resulting in the transfer of phosphoribosyl Ub (PR-Ub) to serine residues on substrate proteins and the release of AMP (Bhogaraju et al, 2016; Kotewicz et al, 2017; Figure 2A)
The Dub activity of SidEs function to reduce the association of ubiquitinated proteins on the Legionella-containing vacuole (LCV), which may antagonize the recruitment of host autophagy machinery to the phagosome
Summary
Ubiquitin (Ub) is a small, 76-amino acid protein that highly conserved in all eukaryotes (Liu et al, 2013; Shaid et al, 2013). Ubiquitination and recruitment of Rab10 to the LCV by SidC and SdcA are regulated by a third OUT-like Dub Lem27 (Lpg2529) ( known as LotC) coded for by L. pneumophila (Schubert et al, 2020; Shin et al, 2020a).
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