# Legionella effectors reveal novel signaling function for the ribosome quality control (RQC) pathway

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2024 · $419,309

## Abstract

Abstract/Project Summary
 Protein synthesis is a key metabolic step in cells that is subjected to perturbations from internal stimuli
or external agents that may sometimes lead to the pausing of translating ribosomes on messenger RNAs, a
phenomenon defined as ribosome stalling. Interestingly, the gram-negative bacterium Legionella pneumophila
(L.p.) manipulates several critical host processes such as protein synthesis and membrane transport to
establish its replicative niche in an endoplasmic reticulum (ER)-like vacuole. L.p. achieves this by injecting
effector proteins via its type IV secretion system, Dot/Icm. Understanding how bacteria sabotage host
processes and manipulate them to their own advantage provides invaluable insights into disease and
mammalian cell biology. Recent studies have highlighted that L.p secretes toxins into infected cells that can
inhibit protein synthesis and induce ribosome stalling. Cells have evolved a conserved mechanism called
ribosome-associated quality control (RQC) that aids in the sensing and resolution of stalled ribosomes and the
maintenance of protein homeostasis. The consequences of ribosome stalling stress to cells however remain
poorly understood. By challenging the cellular translation apparatus with infections of L.p. or sub-optimal doses
of translation elongation inhibitors, we have determined that the sensing of stalled ribosomes in cells activates
a transcriptional and translational program that leads to the upregulation of the activating transcription factor 3
(ATF3). We have determined that this reactionary program is independent from other canonical stress
response pathways such as the unfolded protein response (UPR) or the integrated stress response (ISR).
Strikingly, ATF3 is regulated by L.p. derived proteins SidI and SusF, a toxin-antitoxin couple. The targets of
SidI and SusF in cells are undefined. Furthermore, the upregulation of ATF3 was dependent on multiple
components of the RQC pathway. Moreover, our observations indicate that ATF3 messengers are selectively
translated even under conditions where nascent protein synthesis is suppressed. Concomitant to the activation
of the ribosome stall induced response, L.p. also recruits a pool of translationally active ribosomes to its
replicative niche within cells.
This proposal aims to utilize the molecular tools derived from L.p. to understand the mechanisms that link RQC
to the activation of ATF3 in the nucleus. We expect that the results from the proposed set of experiments will
shed light onto fundamental mechanisms that maintain the homeostasis of protein synthesis in cells and
generate new tools to study and dissect the RQC pathway. We have assembled an exceptionally strong team
of experts and compelling preliminary data that highlight our ability to accomplish our goals.

## Key facts

- **NIH application ID:** 10869928
- **Project number:** 5R01GM140440-09
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Shaeri Mukherjee
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $419,309
- **Award type:** 5
- **Project period:** 2016-06-15 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10869928

## Citation

> US National Institutes of Health, RePORTER application 10869928, Legionella effectors reveal novel signaling function for the ribosome quality control (RQC) pathway (5R01GM140440-09). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10869928. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*