# ER-phagy in the functional conversion of the Brucella-containing vacuole

> **NIH NIH R21** · WASHINGTON STATE UNIVERSITY · 2022 · $229,500

## Abstract

Project Summary
Intracellular microbes with a vacuolar lifestyle share an ability to remodel host cell compartments and
functions to support specific stages of their infectious cycle. The cellular and molecular details of how
microbial vacuoles functionally evolve during a pathogen’s intracellular cycle to promote their virulence are
not well understood. Here we aim to define cellular processes driving the functional evolution of the
intracellular vacuole of the zoonotic bacterium Brucella abortus, which transitions from a replicative niche
to an egress organelle. B. abortus primarily infects phagocytes and remodels its original phagosome into
the replicative Brucella-containing vacuole (rBCV), an organelle derived from the host endoplasmic
reticulum (ER) that supports intracellular proliferation. rBCVs subsequently convert into autophagosome-
like vacuoles (aBCVs) that mediate post-replication bacterial egress. Autophagy is a conserved eukaryotic
process of selective or non-selective capture of cellular content within membrane-bound autophagosomes
for lysosomal degradation, including the selective degradation of organelles such as the ER via dedicated
autophagy receptors. We have shown that aBCV biogenesis from rBCVs requires a subset of conventional
autophagic machineries and an active bacterial VirB Type IV secretion system, but the process, selectivity
and regulation of this vacuolar conversion remain enigmatic. Brucella infection triggers the Unfolded
Protein Response (UPR) during the rBCV stage via the innate immune sensor STING, provoking an ER-
centered stress response that promotes bacterial replication within rBCVs. Whether the UPR also
contributes to aBCV biogenesis is unknown. STING-dependent UPR induces ER-phagy, whose selectivity
could mechanistically drive the capture of ER-derived rBCVs by autophagosomes to form aBCVs. Based
on preliminary evidence that i) Brucella infection influences ER-phagy; ii) rBCVs recruit distinct ER-phagy
receptors and iii) STING is required for aBCV biogenesis, here we will test the overall hypothesis that
aBCV biogenesis is mediated by selective ER-phagy of rBCVs via a STING-dependent process. Aim1 will
determine i) whether Brucella modulates ER-phagy, ii) whether specific ER-phagy receptors are required
for aBCV biogenesis and iii) the autophagic cascade engaged during aBCV biogenesis. Aim 2 will
determine whether the role of STING in aBCV biogenesis is via induction of the UPR or its activity as an
ER-phagy receptor. The successful completion of these aims will establish new concepts of functional
evolution of bacterial vacuoles, a common feature of the infectious cycle of many microbial pathogens that
is poorly understood.

## Key facts

- **NIH application ID:** 10508228
- **Project number:** 1R21AI171258-01
- **Recipient organization:** WASHINGTON STATE UNIVERSITY
- **Principal Investigator:** JEAN A CELLI
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $229,500
- **Award type:** 1
- **Project period:** 2022-05-20 → 2023-01-15

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10508228

## Citation

> US National Institutes of Health, RePORTER application 10508228, ER-phagy in the functional conversion of the Brucella-containing vacuole (1R21AI171258-01). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10508228. Licensed CC0.

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