The recent emphasis on circadian rhythmicity in critical skin cell functions related to homeostasis, regeneration and aging has shed light on the importance of the PER2 circadian clock gene as a vital antitumor gene. Furthermore, delta-opioid receptors (DOPrs) have been identified as playing a crucial role in skin differentiation, proliferation and migration, which are not only essential for wound healing but also contribute to cancer development. In this study, we propose a significant association between cutaneous opioid receptor (OPr) activity and circadian rhythmicity. To investigate this link, we conducted a 48 h circadian rhythm experiment, during which RNA samples were collected every 5 h. We discovered that the activation of DOPr by its endogenous agonist Met-Enkephalin in N/TERT-1 keratinocytes, synchronized by dexamethasone, resulted in a statistically significant 5.6 h delay in the expression of the core clock gene PER2. Confocal microscopy further confirmed the simultaneous nuclear localization of the DOPr-β-arrestin-1 complex. Additionally, DOPr activation not only enhanced but also induced a phase shift in the rhythmic binding of β-arrestin-1 to the PER2 promoter. Furthermore, we observed that β-arrestin-1 regulates the transcription of its target genes, including PER2, by facilitating histone-4 acetylation. Through the ChIP assay, we determined that Met-Enkephalin enhances β-arrestin-1 binding to acetylated H4 in the PER2 promoter. In summary, our findings suggest that DOPr activation leads to a phase shift in PER2 expression via β-arrestin-1-facilitated chromatin remodeling. Consequently, these results indicate that DOPr, much like its role in wound healing, may also play a part in cancer development by influencing PER2.
In insects, antennal ionotropic receptors (IRs) and odorant receptors (ORs) are among the main sensors of olfactory cues. To functionally characterize the subunits from these receptors, the use of ab3A neurons from transgenic Drosophila melanogaster represented one of the most powerful tools, allowing the identification of ligands (deorphanization) and decrypting their pharmacological properties. However, further investigation is needed to shed light on possible metabotropic functionalities behind insect olfactory receptors and test potentials from the up-to-now-used empty neuronal systems to express subunits belonging to variegate receptor classes. In this project, we adopted the most updated system of Drosophila ab3A empty neurons to test various olfactory receptors, ranging from human ORs working as metabotropic G-protein coupled receptors to insect ionotropic IRs and ORs. Testing transgenic Drosophila expressing human ORs into ab3A neurons by single sensillum recording did not result in an OR response to ligands, but it rather re-established neuronal spiking from the empty neurons. When transgenic D. melanogaster expressed ionotropic IRs and ORs, both heterologous and cis-expressed IRs were non-functional, but the Drosophila suzukii OR19A1 subunit responded to a wide asset of ligands, distinguishing phasic or tonic compound-dependent effects. Despite the use of Drosophila ab3A neurons to test the activation of some metabotropic and ionotropic receptor subunits resulted non-functional, this study deorphanized a key OR of D. suzukii demonstrating its binding to alcohols, ketones, terpenes, and esters.
Johannes Larsch, an assistant Professor at the CIG, and Martina Legris, a postdoctoral fellow in Christian Fankhauser group, both got an SNSF starting grant. Martina will join the University of Neuchâtel, and Johannes will use this grant on his project at the CIG.