Zhang Yan, Williams Dwight A, Zaidi Saheem A, Yuan Yunyun, Braithwaite Amanda, Bilsky Edward J, Dewey William L, Akbarali Hamid I, Streicher John M, Selley Dana E
Department of Medicinal Chemistry, Virginia Commonwealth University , 800 East Leigh Street, Richmond, Virginia 23298, United States.
Department of Pharmacology and Toxicology, Virginia Commonwealth University , 410 North 12th Street, Richmond, Virginia 23298, United States.
ACS Chem Neurosci. 2016 Mar 16;7(3):297-304. doi: 10.1021/acschemneuro.5b00245. Epub 2016 Jan 8.
Mounting evidence has suggested that G protein-coupled receptors can be stabilized in multiple conformations in response to distinct ligands, which exert discrete functions through selective activation of various downstream signaling events. In accordance with this concept, we report biased signaling of one C6-heterocyclic substituted naltrexamine derivative, namely, 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-(4'-pyridylcarboxamido)morphinan (NAP) at the mu opioid receptor (MOR). NAP acted as a low efficacy MOR partial agonist in the G protein-mediated [(35)S]GTPγS binding assay, whereas it did not significantly induce calcium flux or β-arrestin2 recruitment. In contrast, it potently blocked MOR full agonist-induced β-arrestin2 recruitment and translocation. Additionally, NAP dose-dependently antagonized MOR full agonist-induced intracellular calcium flux and β-arrestin2 recruitment. Further results in an isolated organ bath preparation confirmed that NAP reversed the morphine-induced reduction in colon motility. Ligand docking and dynamics simulation studies of NAP at the MOR provided more supporting evidence for biased signaling of NAP at an atomic level. Due to the fact that NAP is MOR selective and preferentially distributed peripherally upon systemic administration while β-arrestin2 is reportedly required for impairment of intestinal motility by morphine, biased antagonism of β-arrestin2 recruitment by NAP further supports its utility as a treatment for opioid-induced constipation.
越来越多的证据表明，G蛋白偶联受体可响应不同配体而稳定于多种构象，这些构象通过选择性激活各种下游信号事件发挥离散功能。根据这一概念，我们报道了一种C6-杂环取代的纳曲胺衍生物，即17-环丙基甲基-3,14β-二羟基-4,5α-环氧-6β-(4'-吡啶甲酰胺基)吗啡喃（NAP）在μ阿片受体（MOR）上的偏向性信号传导。在G蛋白介导的[(35)S]GTPγS结合试验中，NAP作为一种低效的MOR部分激动剂，而它并未显著诱导钙流或β-抑制蛋白2募集。相反，它能有效阻断MOR完全激动剂诱导的β-抑制蛋白2募集和转位。此外，NAP剂量依赖性地拮抗MOR完全激动剂诱导的细胞内钙流和β-抑制蛋白2募集。在离体器官浴制备中的进一步结果证实，NAP可逆转吗啡诱导的结肠运动性降低。NAP在MOR上的配体对接和动力学模拟研究为NAP在原子水平上的偏向性信号传导提供了更多支持证据。由于NAP具有MOR选择性，且全身给药后优先分布于外周，而据报道β-抑制蛋白2是吗啡损害肠道运动所必需的，因此NAP对β-抑制蛋白2募集的偏向性拮抗作用进一步支持了其作为阿片类药物所致便秘治疗药物的效用。
