Differential regulation of tyrosine hydroxylase expression in neuroblastoma cells by distinct CB1 cannabinoid receptor agonist
(2006) 16th annual symposium on the cannabinoids — Location: Tihany, Hungary (2.June.2006)
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- Abstract
- 9-THC-mediated alteration of motor and emotional behaviours frequently correlates with modification of catecholamine transmission systems. Beside acute alteration of neurotransmitter release, modulations of complex intracellular signalling pathways by cannabinoid also lead to long-term adaptation of cell functions. In this respect, we previously reported CB1-mediated opposite regulation of tyrosine hydroxylase (TH) gene expression when comparing the responses to the unrelated agonists HU 210 and CP 55,940. Given their crucial regulatory role within the TH promoter, we now further investigated the influence of these agonists on CRE and AP-1 cis-enhancer elements using reporter gene assays. Consistent with CB1-mediated reduction of cAMP accumulation, both ligands decreased CRE-driven luciferase activity. In contrast, in cell engineered to examine AP-1 activity, HU 210 caused a concentration-dependent reduction of luciferase activity whereas CP 55,940 failed to regulated AP-1. We next investigate the role of these response elements in cannabinoid-mediated regulation of TH expression. Site directed mutagenesis of CRE consensus within the TH promoter strongly reduced efficacies of both agonists. Besides, mutation of the AP-1 site totally impaired both HU 210 and CP 55,940-mediated regulation of TH transcription. These data suggest that CRE activity is required to control the efficacy of cannabinoid responses while AP-1 element is crucial for determining the agonist-selective responses. In addition, responses observed both on AP-1 or on TH promoter-driven constructs were sensitive to pertussis toxin, suggesting that agonist-selective responses are mediated through Gi/o-dependent mechanism. Finally, different kinase inhibitors were used to discriminate between signalling pathways involved in cannabinoid-mediated gene transcription. HU 210 and CP 55,940 were found to differentially modulate TH promoter activity through activation of different subsets of intracellular signalling cascades. Surprisingly, PKC inhibitors efficiently inhibited HU 210 effects on both AP-1 and TH promoter, suggesting an agonist-selective regulation of PKC-dependent responses. Taken together, our results demonstrate that commonly used cannabinoid agonists with similar pharmacodynamic properties display differential effects regarding AP-1 cis-enhancer element. This could explain the complex regulations of TH gene expression, leading to totally distinct delayed responses. Our data suggest that complexity may arise from the activation of distinct subsets of Gi/o proteins and their related effectors, supporting the concept of functional selectivity.
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Bosier, B., & et al. (2006). Differential regulation of tyrosine hydroxylase expression in neuroblastoma cells by distinct CB1 cannabinoid receptor agonist. 16th annual symposium on the cannabinoids, Tihany, Hungary. https://hdl.handle.net/2078.5/87903