Pharmacological Characterization of a Highly Selective and Potent Partial Agonist of the MT₂ Melatonin Receptor

Abstract

Background/Aims: The MT₂ melatonin receptor is a potential target for treating circadian rhythm sleep disorders. This study aims to characterize the recently identified MT₂ melatonin receptor agonist. Methods: The pharmacological properties of the MT₂ melatonin receptor-selective agonist as exemplified by compound 1 [N-(2-[7-benzyl-1,6-dihydro-2H-indeno(5,4-b)furan-8-yl]ethyl)acetamide] were evaluated by use of cell-free binding and cell-based functional assays. Results: Competition binding assays using 2-[¹²⁵I]iodomelatonin revealed rapid, reversible, and high-affinity binding of compound 1 to human, mouse, and rat MT₂ melatonin receptors. cAMP, ERK1/2, and PathHunter β-arrestin recruitment assays revealed partial agonist activities. However, compound 1 induced a more intense internalization of human MT₂ melatonin receptor than melatonin. Based on studies using structurally related analogs of compound 1, we further demonstrated that the extent of internalization is independent of the intrinsic efficacy of agonists. Conclusion: These findings provide novel insights into the relationship between intrinsic agonist efficacy and agonist-induced internalization and demonstrate that compound 1 could serve as a pharmacological tool for future studies to elucidate the detailed molecular mechanism of MT₂ receptor internalization.

Type 2 diabetes–associated variants of the MT 2 melatonin receptor affect distinct modes of signaling

“…Although the recruitment of arrestin2 to MT 2 in transfected cells has been reported (56,57), the physiological importance of this phenomenon and its robustness in a cellular context expressing en dogenous MT 2 receptors remain unclear. MT 2 has indeed a poor capacity for MLTinduced arrestin recruitment, an observation that was confirmed here.…”

Melatonin Relieves Paclitaxel-Induced Neuropathic Pain by Regulating pNEK2-Dependent Epigenetic Pathways in DRG Neurons

“…The temporary or reversible effects of MLT observed in behavioral tests and pathway analysis can be attributed to various factors, including MLT metabolism, receptor dynamics, and the body’s homeostatic mechanisms . MLT is metabolized primarily in the liver and rapidly cleared from the bloodstream .…”

“…MLT is metabolized primarily in the liver and rapidly cleared from the bloodstream . MLT primarily acts through its receptors MT1 and MT2, both of which exhibit complex dynamics, including recycling, trafficking, internalization, and desensitization . MLT is closely linked to the circadian system, and its effects can vary with the body’s natural circadian rhythms.…”

“…In addition, our model provides a platform available for further investigating the synergistic effect of MLT and PTX on reducing neuropathy. The temporary or reversible effects of MLT observed in behavioral tests and pathway analysis can be attributed to various factors, including MLT metabolism, 31 receptor dynamics, 32 and the body's homeostatic mechanisms. 33 MLT is metabolized primarily in the liver and rapidly cleared from the bloodstream.…”

New MT2 Melatonin Receptor-Selective Ligands: Agonists and Partial Agonists

“…The β-Arrestin recruitment was monitored using PathHunter CHO-K 1 -MT1 2 R β-arrestin cell line from DiscoveRx ® (Birmingham, UK), essentially as described by Sakurai et al [ 55 ] and recently partly assessed by Gdahou et al [ 56 ]. Cells were cultured at 37 °C, 5% CO 2 in F12-GlutaMAX medium (Thermo Fisher Scientific, Waltham, MA, USA) supplemented with 10% heat inactivated fetal bovine serum.…”