# The interface between L. pneumophila manipulation of host endoplasmic reticulum and innate immune subterfuge

> **NIH NIH R01** · TUFTS UNIVERSITY BOSTON · 2020 · $677,650

## Abstract

Many pathogens grow within host cells by building membrane-bound replication compartments essential for
growth. The compartments provide important protection from host innate immune cytoplasmic surveillance
systems and interfere with trafficking organisms into degradative compartments. Growth in the compartment
is driven by microbial proteins which promote compartment construction, protection against innate immune
surveillance and provide regulatory control over the host cell. How these different arms of the pathogen are
coordinated is poorly understood. A bacterium that uses this strategy is Legionella pneumophila, which
grows in a vacuole within macrophages during pneumonic disease. A group of over 300 Legionella proteins
are translocated into host cells, controlling all aspects of the intracellular lifestyle, including formation of the
replication compartment, blocking host cell translation, and preventing cytosolic recognition of the
replication compartment. The organism hijacks host tubular endoplasmic reticulum (ER) as one of the
earliest steps in replication compartment formation, an event promote by the bacterial Sde proteins.
The proposed studies will test two models for Sde function. First, it will test the model that the Sde proteins
controls ER tubule formation, replication compartment formation, and immune avoidance by promoting a
three-step pathway. Secondly, it will test the model that manipulation of host translation initiation plays a
role in coordinating replication vacuole construction and immune avoidance. The first model proposes that
the Sde deubiquitinase activity liberates free ubiquitin (Ub) from the polyUb on the replication compartment.
This would serve as a pool for ADPribosyltransferase and phosphodiesterase domains to promote Ub
modification of the tubular ER protein Rtn4 and host translation initiation factors (eIFs). In the final step, the
protein family masks the replication compartment with a phosphoribose to prevent recognition by the host
autophagy pathway. The model will be tested by manipulating polyUb pools in the cell, performing electron
microscopy on mutants deranged in this pathway, and reconstructing tubular ER rearrangements in a cell-
free system. To determine the role that targeting of eIF proteins plays in these processes, the targets will be
verified using purified components and the regulated initiation step will be identified. In addition, it will be
determined if eIF proteins are inactivated to remove ribosomes from rough ER and allow close docking of
ER sheets to the replication compartment, and if eIF manipulation skews the host translational response to
favor bacterial replication. Extensive preliminary studies support the proposed experiments, providing a
solid underpinning for this work. Throughout these studies, the objective is to identify a weak link in the
microbial strategy of manipulating ER tubules to promote intracellular growth, with an eye toward
developing antimicrobials that tar...

## Key facts

- **NIH application ID:** 9971956
- **Project number:** 1R01AI146245-01A1
- **Recipient organization:** TUFTS UNIVERSITY BOSTON
- **Principal Investigator:** Ralph R. Isberg
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $677,650
- **Award type:** 1
- **Project period:** 2020-02-20 → 2025-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9971956

## Citation

> US National Institutes of Health, RePORTER application 9971956, The interface between L. pneumophila manipulation of host endoplasmic reticulum and innate immune subterfuge (1R01AI146245-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9971956. Licensed CC0.

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