The novel antibacterial compound walrycin A induces human PXR transcriptional activity.
The human pregnane X receptor (PXR) is a ligand-regulated transcription factor belonging to the nuclear receptor superfamily. PXR is activated by a large, structurally diverse, set of endogenous and xenobiotic compounds and coordinates the expression of genes central to metabolism and excretion of potentially harmful chemicals and therapeutic drugs in humans. Walrycin A is a novel antibacterial compound targeting the WalK/WalR two-component signal transduction system of Gram (+) bacteria. Here, we report that, in hepatoma cells, walrycin A potently activates a gene set known to be regulated by the xenobiotic sensor PXR. Walrycin A was as efficient as the reference PXR agonist rifampicin to activate PXR in a transactivation assay at noncytotoxic concentrations. Using a limited proteolysis assay, we show that walrycin A induces conformational changes at a concentration which correlates with walrycin A ability to enhance the expression of prototypic target genes, suggesting that walrycin A interacts with PXR. The activation of the canonical human PXR target gene CYP3A4 by walrycin A is dose and PXR dependent. Finally, in silico docking experiments suggest that the walrycin A oxidation product Russig's blue is the actual ligand for PXR. Taken together, these results identify walrycin A as a novel human PXR activator.
Univ Lille Nord de France, F-59000 Lille, France.
Alexandre
A
Berthier
Frédérik
F
Oger
Céline
C
Gheeraert
Abdel
A
Boulahtouf
Rémy
R
Le Guével
Patrick
P
Balaguer
Bart
B
Staels
Gilles
G
Salbert
Philippe
P
Lefebvre
D000900:Anti-Bacterial Agents / Q000633:toxicity*; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D019295:Computational Biology; D003198:Computer Simulation; D051544:Cytochrome P-450 CYP3A / Q000096:biosynthesis* / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D009284:Naphthols / Q000633:toxicity*; D020411:Oligonucleotide Array Sequence Analysis; D000077297:Pregnane X Receptor; D011485:Protein Binding; D021281:Quantitative Structure-Activity Relationship; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011987:Receptors, Steroid / Q000187:drug effects* / Q000235:genetics; D012293:Rifampin / Q000494:pharmacology; D014162:Transfection
D000900:Anti-Bacterial Agents; D009284:Naphthols; D000077297:Pregnane X Receptor; D034741:RNA, Small Interfering; D011987:Receptors, Steroid; C574123:walrycin A; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D012293:Rifampin