# Interferon-inducible cell-autonomous immunity to cytosolic bacterial pathogens

> **NIH NIH R01** · DUKE UNIVERSITY · 2024 · $540,532

## Abstract

Human cells including epithelial cells are equipped with cell-autonomous host defense programs providing
protection against intracellular pathogens. These host protective programs are controlled in a temporal and
spatial manner and respond to extracellular cues including pro-inflammatory cytokines released by professional
immune cells. Arguably, the most potent inducer of antibacterial cell-autonomous host defense is lymphocyte-
derived interferon-gamma (IFN). IFN-receptor signaling in human epithelial cells induces the expression of
hundreds of IFN-stimulated genes (ISGs) encoding antimicrobial proteins. While a few ISGs have been studied
in much detail, our understanding of most ISGs and their functions in host defense is limited. We recently
discovered a critical role for IFN-inducible guanylate binding proteins (GBPs) in cell-autonomous immunity to
Gram-negative bacterial pathogens invading the host cell cytosol. Human GBP1 is a cytosolically localized
member this GBP family and able to directly detect a central building block of the Gram-negative bacterial outer
membrane, i.e. lipopolysaccharide (LPS). Our previous work showed that GBP1, through these LPS interactions,
forms a multimeric microcapsule or coatomer surrounding Gram-negatives invading the host cell cytosol.
However, GBP1 binding to the bacterial surface on its own is neither bactericidal nor bacteriostatic, implicating
other GBP1-dependent co-factors required for sterilizing cell-autonomous immunity. Aim1 of our proposal will
explore a novel GBP1-dependent pathway that results in bacterial ubiquitylation, a well-established ‘eat-me’
signal that marks cytosolic microbial invaders for destruction. Our studies are multidisciplinary and include
biochemical approaches levering a novel in vitro GBP1-bacteria binding assay that we established. Using this
assay, we will directly assess how GBP1 promotes the recruitment of IFN-inducible host ubiquitin E3 ligases to
the surface of the Gram-negative cytosol-invading bacterial pathogen Shigella flexneri. S. flexneri is a human-
adapted enteric pathogen that causes dysentery and diarrheal deaths, especially in children in low- and middle-
income countries. Our preliminary data demonstrate that wildtype S. flexneri is resistant to GBP1-dependent and
-independent host-driven bacterial ubiquitylation. Therefore, in our second aim we will identify and characterize
a network of virulence factors used by S. flexneri to escape IFN-induced ubiquitylation and associated host
defenses. To define the physiological relevance of these antagonistic relationships between antibacterial ISGs
and counter-acting bacterial virulence mechanisms employed by S. flexneri, we will exploit a novel mouse model
of intestinal S. flexneri infections. Using ISG-deficient mouse lines established in our lab and, reciprocally,
infecting with S. flexneri mutants defective for virulence effectors targeting the same ISGs, we will determine the
physiological importance of G...

## Key facts

- **NIH application ID:** 10871750
- **Project number:** 2R01AI139425-05A1
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** Joern Coers
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $540,532
- **Award type:** 2
- **Project period:** 2019-09-01 → 2028-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10871750

## Citation

> US National Institutes of Health, RePORTER application 10871750, Interferon-inducible cell-autonomous immunity to cytosolic bacterial pathogens (2R01AI139425-05A1). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10871750. Licensed CC0.

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