Functional independence of endogenous μ- and δ-opioid receptors co-expressed in cholinergic interneurons.
Functional independence of endogenous μ- and δ-opioid receptors co-expressed in cholinergic interneurons.
复制标题
内源性μ-和δ-阿片受体在胆碱能中间神经元共表达的功能独立性。
DOI：
10.7554/elife.69740
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发表时间：
2021-09-03
期刊：
影响因子：
7.7
通讯作者：
Farrens D
中科院分区：
文献类型：
--
作者：
Arttamangkul S;Platt EJ;Carroll J;Farrens D
A类G蛋白偶联受体（GPCR）通常作为单体发挥作用，尽管来自异源表达系统的证据表明它们有时可能形成同源二聚体和/或异源二聚体。本研究旨在评估小鼠神经元中内源性μ-和δ-阿片受体（MORs和DORs）可能的功能相互作用。然而，检测天然组织中的GPCR二聚体一直具有挑战性。先前，已报道在转染细胞中共表达的MORs和DORs形成异二聚体，并且已在表达融合至荧光蛋白的基因工程受体的敲入小鼠中研究了它们在神经元中可能的共定位。在这里，我们发现，在小鼠纹状体单个胆碱能神经元内源性表达MORs和DORs。用配体定向标记试剂NAI-A594荧光标记来自活脑切片的神经元上的受体。用DAMGO（μ-激动剂）和deltorphin（δ-激动剂）选择性激活MORs和DORs抑制所有检查的细胞中的自发放电。在持续存在激动剂的情况下，作为应用deltorphin的受体脱敏的结果，放电率返回到基线，但应用DAMGO时观察到的放电率较低。此外，检测到激动剂诱导的DORs而非MORs的内化。当MORs和DORs同时被[Met 5]-脑啡肽激活时，MORs的脱敏被促进，但内化没有增加。总之，这些结果表明，虽然MORs和DORs在单个纹状体胆碱能中间神经元中表达，但这两种受体独立发挥作用。
Class A G-protein-coupled receptors (GPCRs) normally function as monomers, although evidence from heterologous expression systems suggests that they may sometimes form homodimers and/or heterodimers. This study aims to evaluate possible functional interplay of endogenous µ- and δ-opioid receptors (MORs and DORs) in mouse neurons. Detecting GPCR dimers in native tissues, however, has been challenging. Previously, MORs and DORs co-expressed in transfected cells have been reported to form heterodimers, and their possible co-localization in neurons has been studied in knock-in mice expressing genetically engineered receptors fused to fluorescent proteins. Here, we find that single cholinergic neurons in the mouse striatum endogenously express both MORs and DORs. The receptors on neurons from live brain slices were fluorescently labeled with a ligand-directed labeling reagent, NAI-A594. The selective activation of MORs and DORs, with DAMGO (µ-agonist) and deltorphin (δ-agonist) inhibited spontaneous firing in all cells examined. In the continued presence of agonist, the firing rate returned to baseline as the result of receptor desensitization with the application of deltorphin but was less observed with the application of DAMGO. In addition, agonist-induced internalization of DORs but not MORs was detected. When MORs and DORs were activated simultaneously with [Met5]-enkephalin, desensitization of MORs was facilitated but internalization was not increased. Together, these results indicate that while MORs and DORs are expressed in single striatal cholinergic interneurons, the two receptors function independently.