Abstract：
The μ-opioid receptor-biased agonist theory holds that Gio protein signaling mediates the analgesic effect of opioids and the related side effects via the β-arrestin2 signaling pathway. A series of μ-opioid-biased agonists have been developed in accordance with this theory, and the FDA has approved TRV130 (as a representative of biased agonists) for marketing. However, several reports have raised the issue of opioid side effects associated with the use of agonists. In this study, five permeable peptides were designed to emulate 11 S/T phosphorylation sites at the μ-opioid receptor (MOR) carboxyl-terminal. In vitro experiments were performed to detect the activation level of G proteins from the cAMP inhibition assay and the β-arrestin2 recruitment by the BRET assay. Designed peptides might effectively interfere with the activation of the Gio and β-arrestin2 pathways when combined with morphine. The resulting morphine-induced tolerance, respiratory inhibition, and constipation in mice showed that the β-arrestin2 pathway was responsible for morphine tolerance while the Gio signaling pathway was involved with respiratory depression and constipation and that these side effects were significantly related to phosphorylation sites S363 and T370. This study may provide new directions for the development of safer and more effective opioid analgesics, and the designed peptides may be an effective tool for exploring the mechanism by which μ-opioid receptors function, with the potential of reducing the side effects that are associated with clinical opioid treatment.
摘要：
μ阿片受体偏向激动剂理论认为，Gio蛋白信号通过β-arrestin2信号通路介导阿片类药物的镇痛作用及相关副作用。根据这一理论，已经开发了一系列μ-阿片样物质偏向的激动剂，FDA已批准TRV130（作为偏倚激动剂的代表）用于营销。然而,一些报告提出了与使用激动剂相关的阿片类药物副作用的问题.在这项研究中,设计了五种渗透性肽来模仿μ阿片受体（MOR）羧基末端的11个S/T磷酸化位点。进行体外实验以检测来自cAMP抑制测定的G蛋白的活化水平和通过BRET测定的β-arrestin2募集。当与吗啡组合时，设计的肽可能会有效地干扰Gio和β-arrestin2途径的激活。由此产生的吗啡诱导的耐受性，呼吸抑制,和小鼠便秘表明，β-arrestin2途径负责吗啡耐受，而Gio信号通路与呼吸抑制和便秘有关，并且这些副作用与磷酸化位点S363和T370显着相关。本研究可能为开发更安全、更有效的阿片类镇痛药提供新的方向,设计的肽可能是探索μ阿片受体功能机制的有效工具，有可能减少与临床阿片类药物治疗相关的副作用。
