The activity of the C4-dicarboxylic acid chemoreceptor of Pseudomonas aeruginosa is controlled by chemoattractants and antagonists

Abstract

Chemotaxis toward organic acids has been associated with colonization fitness and virulence and the opportunistic pathogen Pseudomonas aeruginosa exhibits taxis toward several tricarboxylic acid intermediates. In this study, we used high-throughput ligand screening and isothermal titration calorimetry to demonstrate that the ligand binding domain (LBD) of the chemoreceptor PA2652 directly recognizes five C4-dicarboxylic acids with KD values ranging from 23 µM to 1.24 mM. In vivo experimentation showed that three of the identified ligands act as chemoattractants whereas two of them behave as antagonists by inhibiting the downstream chemotaxis signalling cascade. In vitro and in vivo competition assays showed that antagonists compete with chemoattractants for binding to PA2652-LBD, thereby decreasing the affinity for chemoattractants and the subsequent chemotactic response. Two chemosensory pathways encoded in the genome of P. aeruginosa, che and che2, have been associated to chemotaxis but we found that only the che pathway is involved in PA2652-mediated taxis. The receptor PA2652 is predicted to contain a sCACHE LBD and analytical ultracentrifugation analyses showed that PA2652-LBD is dimeric in the presence and the absence of ligands. Our results indicate the feasibility of using antagonists to interfere specifically with chemotaxis, which may be an alternative strategy to fight bacterial pathogens.

High-Affinity Chemotaxis to Histamine Mediated by the TlpQ Chemoreceptor of the Human Pathogen Pseudomonas aeruginosa

“…The interference with motility and chemotaxis is an alternative strategy to block bacterial pathogens ( 48 ). Previous work has shown that some chemoreceptors recognize chemoattractants and antagonists ( 27 , 49 , 50 ), and the identification of antagonists that specifically interfere with histamine chemotaxis may thus be an alternative approach to modulate the virulence properties of P. aeruginosa . Remarkably, the identification of these antagonists may be facilitated by the resolution of the three-dimensional structure of TlpQ-LBD in complex with histamine ( Fig.…”

“…In contrast, PAO1 chemotaxis to proteinogenic amino acids and GABA is mediated by three paralogous receptors, namely, PctA, PctB, and PctC ( 23 , 24 ). Additionally, this strain has two receptors for inorganic phosphate ( 25 , 26 ) as well as receptors for malate ( 27 , 28 ), α-ketoglutarate ( 29 ), and chloroethylenes ( 30 ). P. aeruginosa is also attracted to the plant hormone ethylene, and it was shown that the deletion of the gene encoding the TlpQ chemoreceptor abolished ethylene chemotaxis ( 31 ).…”

The ligand‐binding domain of a chemoreceptor from Comamonas testosteroni has a previously unknown homotrimeric structure

“…Similar to Tar, some other helical LBDs also alter the oligomeric state upon ligand binding, such as 4HB domains of PcaY_PP (Fernandez et al , ) and CtpH (Rico‐Jimenez et al , ), HBM domains of McpS (Lacal et al , ) and McpQ (Martin‐Mora et al , ), and PilJ domain of McpN (Martin‐Mora et al , ). On the contrary, the oligomerization of some dCACHE and sCACHE LBDs is not altered by ligand binding and their ligand binding sites are not located at the dimeric interface (Rico‐Jimenez et al , ; Martin‐Mora et al , ; Gavira et al , ). For example, the dCACHE of the P. aeruginosa PctA chemoreceptor was found as a monomer in both ligand‐free and ligand‐bound states (Rico‐Jimenez et al , ), and the sCACHE domain of P. aeruginosa PA2652 chemoreceptor exists as dimer in both states (Martin‐Mora et al , ).…”

“…On the contrary, the oligomerization of some dCACHE and sCACHE LBDs is not altered by ligand binding and their ligand binding sites are not located at the dimeric interface (Rico‐Jimenez et al , ; Martin‐Mora et al , ; Gavira et al , ). For example, the dCACHE of the P. aeruginosa PctA chemoreceptor was found as a monomer in both ligand‐free and ligand‐bound states (Rico‐Jimenez et al , ), and the sCACHE domain of P. aeruginosa PA2652 chemoreceptor exists as dimer in both states (Martin‐Mora et al , ).…”

Ethanolamine regulates CqsR quorum-sensing signaling inVibrio cholerae

“…Although ethanolamine binds to CqsR-LBD with sub-micromolar affinity (k d ∼0.5 µM), millimolar level of ethanolamine is needed to fully induce the HCD QS response in V. cholerae . This apparent difference is not uncommon for signaling pathways dependent on CACHE receptor proteins (e.g.,(50, 53)). This is in stark contrast to the typical effective concentration for canonical autoinducers, such as CAI-1 and AI-2, which are in micromolar levels (16–19, 24, 25).…”