Pseudomonas aeruginosa Expresses a Functional Human Natriuretic Peptide Receptor Ortholog: Involvement in Biofilm Formation
Authors: Rosay Thibaut , Bazire Alexis , Diaz Suraya , Clamens Thomas , Blier Anne-Sophie , Mijouin Lily , Hoffmann Brice , Sergent Jacques-Aurélien , Bouffartigues Emeline , Boireau Wilfrid , Vieillard Julien , Hulen Christian , Dufour Alain , Harmer Nicholas J. , Feuilloley Marc G. J. , Lesouhaitier Olivier 
Published: August 2015

Considerable evidence exists that bacteria detect eukaryotic communication molecules and modify their virulence accordingly. In previous studies, it has been demonstrated that the increasingly antibiotic-resistant pathogen
Pseudomonas aeruginosa
can detect the human hormones brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) at micromolar concentrations. In response, the bacterium modifies its behavior to adapt to the host physiology, increasing its overall virulence. The possibility of identifying the bacterial sensor for these hormones and interfering with this sensing mechanism offers an exciting opportunity to directly affect the infection process. Here, we show that BNP and CNP strongly decrease
P. aeruginosa
biofilm formation. Isatin, an antagonist of human natriuretic peptide receptors (NPR), prevents this effect. Furthermore, the human NPR-C receptor agonist cANF
4-23
mimics the effects of natriuretic peptides on
P. aeruginosa
, while sANP, the NPR-A receptor agonist, appears to be weakly active. We show
in silico
that NPR-C, a preferential CNP receptor, and the
P. aeruginosa
protein AmiC have similar three-dimensional (3D) structures and that both CNP and isatin bind to AmiC. We demonstrate that CNP acts as an AmiC agonist, enhancing the expression of the
ami
operon in
P. aeruginosa
. Binding of CNP and NPR-C agonists to AmiC was confirmed by microscale thermophoresis. Finally, using an
amiC
mutant strain, we demonstrated that AmiC is essential for CNP effects on biofilm formation. In conclusion, the AmiC bacterial sensor possesses structural and pharmacological profiles similar to those of the human NPR-C receptor and appears to be a bacterial receptor for human hormones that enables
P. aeruginosa
to modulate biofilm expression.

IMPORTANCE
The bacterium
Pseudomonas aeruginosa
is a highly dangerous opportunist pathogen for immunocompromised hosts, especially cystic fibrosis patients. The sites of
P. aeruginosa
infection are varied, with predominance in the human lung, in which bacteria are in contact with host molecular messengers such as hormones. The C-type natriuretic peptide (CNP), a hormone produced by lung cells, has been described as a bacterial virulence enhancer. In this study, we showed that the CNP hormone counteracts
P. aeruginosa
biofilm formation and we identified the bacterial protein AmiC as the sensor involved in the CNP effects. We showed that AmiC could bind specifically CNP. These results show for the first time that a human hormone could be sensed by bacteria through a specific protein, which is an ortholog of the human receptor NPR-C. The bacterium would be able to modify its lifestyle by favoring virulence factor production while reducing biofilm formation.