# In vivo Reporters of Mycobacterium tuberculosis ESX-5 Secretion

> **NIH NIH R21** · UNIVERSITY OF MINNESOTA · 2021 · $232,500

## Abstract

PROJECT SUMMARY/ABSTRACT
Mycobacterium tuberculosis (Mtb) requires the specialized Type VII protein secretion system ESX-5 for growth
in vitro, but little is known about the expression or activity of ESX-5 during infection. A recent report suggested
ESX-5 genes are transcriptionally induced at the acute stage of infection in mice. However, the regulatory
networks and host signals that stimulate ESX-5 expression as well as the stage(s) of infection at which ESX-5
is induced remain to be comprehensively identified. The overall objective of this proposal is to characterize
how Mtb regulates ESX-5 secretion during infection. The proposed research will test the central hypothesis
that ESX-5 is activated in response to specific nutritional cues or environmental stressors to counteract growth
restriction in host interstitial macrophages. Prior studies implicated phosphate limitation as one signal that
induces ESX-5 activity in vitro, but disrupting phosphate-dependent ESX-5 regulation did not impact Mtb
growth or persistence in mice, suggesting that other uncharacterized regulators control ESX-5 in the host.
Preliminary data show that over-expression of two different transcriptional regulators can induce ESX-5
secretion in vitro. Specific Aim 1 will test the hypothesis that specific transcription factors activate ESX-5 in
response to nutritional cues and stress conditions that Mtb encounters in host macrophages. In Specific Aim 2,
fluorescent ESX-5 transcriptional reporters will be developed and tested in macrophage and mouse infection
models using flow cytometry to determine when and in what cell types ESX-5 expression is induced during
infection. Fluorescent reporters of ESX-5 substrate export will also be developed for analysis of ESX-5 activity
during macrophage infection. The innovative fluorescent reporters developed will enable future screens for
small molecules that disrupt ESX-5 expression and/or activity. The proposed research is significant because it
will fill important gaps in knowledge of ESX-5 function by identifying the host cues and regulatory factors that
control ESX-5 expression and establishing the stage(s) of infection when Mtb will be most vulnerable to drugs
targeting ESX-5 or its regulation.

## Key facts

- **NIH application ID:** 10372365
- **Project number:** 1R21AI159460-01A1
- **Recipient organization:** UNIVERSITY OF MINNESOTA
- **Principal Investigator:** Anna DeGraff Tischler
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $232,500
- **Award type:** 1
- **Project period:** 2021-09-22 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10372365

## Citation

> US National Institutes of Health, RePORTER application 10372365, In vivo Reporters of Mycobacterium tuberculosis ESX-5 Secretion (1R21AI159460-01A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10372365. Licensed CC0.

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