Cells communicate and modulate their response to the environment via the specific recognition of signalling molecules by receptors. This happens across all kingdoms of life and, intriguingly, there is increasing evidence that bacteria recognise and respond to host signals, and vice versa. However, in most cases the mode of action and signal transduction pathways involved are unknown. In this talk I will describe our recent work using chemical proteomics to unravel a host-pathogen signalling event. Previous research has shown that under conditions of host stress, levels of the human opioid dynorphin are elevated, triggering virulence in the opportunistic pathogenic bacterium Pseudomonas aeruginosa via an unknown mechanism. To search for the putative bacterial dynorphin receptor, we developed a library of dynorphin-mimetic chemical probes equipped with a photoreactive warhead to trap interactors and a click tag for downstream analysis. We used our probes to search for potential protein binding partners of dynorphin in live cells using quantitative proteomics. We identified a little-characterised membrane sensor, ParS, as a hit. Genetic knockdown of parS and in-depth global proteome analyses confirmed the functional relevance of this interaction. This work reveals a novel mechanism by which P. aeruginosa may detect and defend itself against the potentially hostile host environment. Current work in my lab aims to investigate other human signalling molecules that may trigger bacterial defence against antimicrobials and adaptation to the host, and to expand our approach to consider host cell detection of bacterial molecules. We are also further developing our tools, for example to pinpoint the precise sites where molecules bind to their receptors in living systems.

Chemical proteomic tools to identify the targets of peptide signals at the host-microbe interface

2019 Fall National Meeting

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