# Molecular mechanisms supporting bacterial survival within immune cells

> **NIH NIH P20** · UNIVERSITY OF DELAWARE · 2020 · $236,600

## Abstract

PROJECT SUMMARY
Gram-negative bacteria are increasingly challenging to combat because existing antibiotics struggle to reach
their intracellular targets and face elimination by efflux pumps. This issue is particularly pressing for bacteria
that establish a replication-permissive vacuole derived from the host's plasma membrane. Shielded by multiple
layers of membranes, intracellular pathogens become inaccessible to traditional antibiotics. A fundamental gap
persists in the current understanding of how bacterial pathogens subvert host membrane transport processes
and continued existence of this gap impedes our understanding of mechanisms that bacterial pathogens use to
coordinate virulence strategies. Our long-term goal is to address this gap by systematically unveiling the host
pathways critical for infection of human lung macrophages by the bacterial pathogen Legionella pneumophila,
the causative agent of a severe pneumonia known as Legionnaires' disease. Legionella infects lung
macrophages and resists degradation by establishing and residing within a membrane-bound compartment
known as the Legionella-containing vacuole. Initially derived from the host cell's plasma membrane, this
vacuolar membrane is dramatically remodeled during infection. To do so, the bacterium immediately begins
translocating a large number of (effector) proteins directly into the host cytosol. The host membrane trafficking
network is a major target of L. pneumophila effector proteins. In particular, vesicles traveling between the
endoplasmic reticulum and the Golgi are sequestered by the Legionella-containing vacuole early during
infection, whereas fusion with degradative lysosomes is prevented. These observations support the working
model that the pathogen orchestrates its molecular interactions with the host to stimulate or inhibit fusion of
host vesicles with its vacuole. Delineating the spatiotemporal distribution of secreted effectors is a critical step
to understanding how L. pneumophila interacts with the host cell to ensure its own survival. The overall
objective is to examine the spatiotemporal localization of L. pneumophila effector proteins in the context of
human macrophage infection and to determine how L. pneumophila effectors interact with host
phosphoinositide lipids to target membrane compartments. We propose: (1) to use a dual pronged approach
based on chemical biology to directly track localization of L. pneumophila effectors in infected human
macrophages, and (2) to characterize the protein-lipid interface between L. pneumophila effectors identified in
our preliminary screen using X-ray crystallography. The proposed research is significant because it is
positioned to advance our understanding of how bacterial pathogens manipulate host membrane transport
pathways to promote intracellular survival of bacteria. A significant collateral outcome is that these studies
could suggest new molecular targets for intervention in L. pneumophila infections and related...

## Key facts

- **NIH application ID:** 10026273
- **Project number:** 2P20GM104316-06A1
- **Recipient organization:** UNIVERSITY OF DELAWARE
- **Principal Investigator:** Maria Ramona Neunuebel
- **Activity code:** P20 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $236,600
- **Award type:** 2
- **Project period:** 2014-09-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10026273

## Citation

> US National Institutes of Health, RePORTER application 10026273, Molecular mechanisms supporting bacterial survival within immune cells (2P20GM104316-06A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10026273. Licensed CC0.

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