# Identification of small molecule probes for dissecting the roles of sorting platform components within the type III secretion system

> **NIH NIH R21** · UNIVERSITY OF KANSAS LAWRENCE · 2020 · $189,375

## Abstract

SUMMARY
 Our laboratory studies the bacterial type III secretion system (T3SS) which is a sophisticated nanomachine
that permits communication with eukaryotic cells to subvert normal cellular functions. T3SSs are essential
virulence factors for a number of biomedically important human pathogens including Yersinia pestis (plague),
Shigella spp. (dysentery), Salmonella spp. (diarrhea/enteric fever), Bordetella pertussis (whooping cough), and
Pseudomonas aeruginosa (opportunistic/nosocomial infections). While these systems are diverse with regard to
the effector proteins they deliver, the T3SS apparatus (T3SA) is well-conserved with respect to overall structure
and architecture. The T3SA is comprised of: 1) a cytoplasmic sorting platform that recognizes secretion
substrates and powers secretion; 2) a rigid basal body spanning the entire cell envelope; and 3) an exposed
needle with tip complex that delivers cargo into host cells. The protein components of the sorting platform have
been identified, but little was known about how they assemble until we published the first description of the in
situ Shigella T3SA sorting platform. Since then, we have determined the structural details and dynamics of this
platform, including the essential protein-protein contacts. Based on this background information, we
hypothesize that key interfaces within the sorting platform can be targeted to block type III secretion in
Shigella. Furthermore, we can extrapolate our findings to identify inhibitors of homologous interactions
within distantly related T3SA sorting platforms such as that form P. aeruginosa. Here, we will target the
interaction between inner membrane-imbedded MxiG (via its cytoplasmic domain, MxiGc) and its newly identified
binding partner, MxiK, in Shigella. The homologous pair from P. aeruginosa (PscDc and PscK, respectively) will
also be targeted. The specific aims of this pilot project application are to: 1) Complete high-throughput screens
of extended chemical libraries to identify small molecules that interfere with the interaction of MxiGc (PscDc) with
MxiK (PscK); and 2) Validate hits for inhibitors of the MxiG-MxiK and PscD-PscK interactions by performing
ligand binding experiments and determining their effects on Shigella and Pseudomonas T3SS-related virulence
functions. This high-risk, high-payoff potential of this exploratory project will employ specialized core laboratories
in high-throughput screening, computational chemical biology and protein structure determination at the
University of Kansas to generate a synergy that will allow an unprecedented level of understanding of the
mechanism by which the T3SA sorting platform operates.

## Key facts

- **NIH application ID:** 9932334
- **Project number:** 5R21AI146517-02
- **Recipient organization:** UNIVERSITY OF KANSAS LAWRENCE
- **Principal Investigator:** WILLIAM D. PICKING
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $189,375
- **Award type:** 5
- **Project period:** 2019-06-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9932334

## Citation

> US National Institutes of Health, RePORTER application 9932334, Identification of small molecule probes for dissecting the roles of sorting platform components within the type III secretion system (5R21AI146517-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9932334. Licensed CC0.

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