# Screening of FDA-Approved Small Molecules to Discover Inhibitors of the Pseudomonas aeruginosa Quorum-Sensing Enzyme, PqsE

## TL;DR

Researchers screened FDA-approved drugs to find molecules that inhibit a key enzyme in Pseudomonas aeruginosa, a dangerous hospital-acquired infection pathogen.

## Contribution

A fluorescence polarization screen identified three FDA-approved molecules that inhibit PqsE, a key enzyme in Pseudomonas aeruginosa quorum sensing.

## Key findings

- Three FDA-approved molecules were identified as PqsE inhibitors, with two showing competitive inhibition.
- Apomorphine exhibited a distinct inhibitory profile, suggesting allosteric inhibition of PqsE.
- Vorinostat inhibited intracellular PqsE and is being explored for synthetic derivatization to block the PqsE-RhlR interaction.

## Abstract

Pseudomonas aeruginosa is a notorious
pathogen
that is a leading cause of hospital-acquired infections, for which
there are few treatment options. The quorum sensing (QS) pathway governs
many pathogenic behaviors that allow for P. aeruginosa to stage infections. Within the QS pathway, there
is a key protein–protein interaction between an enzyme, PqsE,
and one of the master QS regulators, RhlR. Although its catalytic
function is dispensable for its interaction with RhlR, previous mutagenic
work characterizing the active site of PqsE identified active site
mutations that induce a conformational change in PqsE, preventing
it from forming a complex with RhlR. These active site mutations,
when introduced stably into the genome of P. aeruginosa, also lead to a significant decrease in production
of a key toxin, pyocyanin, and prevent colonization in the lungs of
a murine host. Here, we performed a fluorescence polarization screen
of an FDA-approved drug library to identify molecules that bind in
the active site of PqsE. Three molecules were identified, two of which
showed inhibitory activity consistent with a competitive mode of
inhibition. One hit molecule, Apomorphine, had a distinctly different
inhibitory profile and is potentially binding outside of the active
site to allosterically inhibit enzyme activity of PqsE. All three
hit molecules were tested in a cellular enzyme assay, and one of the
competitive inhibitors, Vorinostat, was found to inhibit intracellular
PqsE. Vorinostat is now being explored as a candidate for synthetic
derivatization to inhibit the PqsE-RhlR protein–protein interaction
via binding in the PqsE active site.