Differential modulation of AP-1- and CRE-driven transcription by cannabinoid agonists emphasizes functional selectivity at the CB1 receptor.
OBJECTIVE
Long-term adaptations to pharmacological stimuli frequently originate from modulation of complex intracellular signalling pathways. We previously reported that HU210 and CP55940, two CB1 cannabinoid receptor agonists, induced opposite effects on TH expression. Herein, we characterized their influence on cAMP response element (CRE) and activator protein 1 (AP-1)-mediated regulation of gene transcription.


METHODS
The activity of the agonists was examined on transfected N1E-115 cells in which expression of the luciferase reporter gene was controlled by transcription promoters consisting of repeats of either CRE or AP-1 elements. In addition, the implication of classical signalling pathways was investigated using a variety of kinase inhibitors.


RESULTS
Consistent with the CB1-mediated reduction of cAMP accumulation, both ligands decreased CRE-driven luciferase expression with similar potencies. HU210 also exhibited a concentration-dependent reduction of luciferase activity in cells engineered to examine AP-1-controlled transcription, whereas such response was not obtained with CP55940. Responses were all inhibited by SR141716A and were modified in Pertussis toxin-treated cells, suggesting agonist-selective regulations of distinct Gi/o-dependent mechanisms through CB1 receptor activation. Finally, PKC inhibitors efficiently inhibited the paradoxical effect of HU210 on AP-1-mediated transcription, indicating selective regulation of PKC-dependent responses.


CONCLUSIONS
Together, our results demonstrate that two cannabinoid ligands, commonly used as reference agonists acting on the same receptor with similar affinities, differentially modulate gene transcription through distinct controls of AP-1. This could reflect activation of distinct subsets of Gi/o-proteins, supporting the concept of functional selectivity at CB1 receptors.
Bosier
B
B
Unité de Chimie Pharmaceutique et de Radiopharmacie (UCL 7340), Université catholique de Louvain, Brussels, Belgium.
Hermans
E
E
Lambert
Dm
D
D000818:Animals; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism*; D003511:Cyclohexanols / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004742:Enhancer Elements, Genetic / Q000187:drug effects*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D017930:Genes, Reporter; D049410:Luciferases, Renilla / Q000096:biosynthesis; D051379:Mice; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D018808:Transcription Factor AP-1 / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
D003511:Cyclohexanols; D047428:Protein Kinase Inhibitors; D043884:Receptor, Cannabinoid, CB1; D018808:Transcription Factor AP-1; D013759:Dronabinol; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D000242:Cyclic AMP; D049410:Luciferases, Renilla; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C062018:HU 211