Department of Biological Sciences, The Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA 15213.
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213.
Mol Biol Cell. 2019 Mar 1;30(5):680-690. doi: 10.1091/mbc.E18-05-0292. Epub 2019 Jan 2.
The delta opioid receptor (DOR), a physiologically relevant prototype for G protein-coupled receptors, is retained in intracellular compartments in neuronal cells. This retention is mediated by a nerve growth factor (NGF)-regulated checkpoint that delays the export of DOR from the trans-Golgi network. How DOR is selectively retained in the Golgi, in the midst of dynamic membrane transport and cargo export, is a fundamental unanswered question. Here we address this by investigating sequence elements on DOR that regulate DOR surface delivery, focusing on the C-terminal tail of DOR that is sufficient for NGF-mediated regulation. By systematic mutational analysis, we define conserved dual bi-arginine (RXR) motifs that are required for NGF- and phosphoinositide-regulated DOR export from intracellular compartments in neuroendocrine cells. These motifs were required to bind the coatomer protein I (COPI) complex, a vesicle coat complex that mediates primarily retrograde cargo traffic in the Golgi. Our results suggest that interactions of DOR with COPI, via atypical COPI motifs on the C-terminal tail, retain DOR in the Golgi. These interactions could provide a point of regulation of DOR export and delivery by extracellular signaling pathways.
δ 阿片受体（DOR）是一种与生理相关的 G 蛋白偶联受体原型，存在于神经元细胞的细胞内隔室中。这种保留是由神经生长因子（NGF）调节的检查点介导的，该检查点延迟了 DOR 从反式高尔基体网络中的输出。DOR 如何在高尔基体中被选择性保留，而高尔基体中存在着动态的膜运输和货物输出，这是一个基本的未解决的问题。在这里，我们通过研究调节 DOR 表面递呈的 DOR 上的序列元件来解决这个问题，重点是 DOR 的 C 末端尾部，它足以进行 NGF 介导的调节。通过系统的突变分析，我们确定了保守的双精氨酸（RXR）基序，这些基序对于 NGF 和磷酸肌醇调节的神经内分泌细胞中细胞内隔室中 DOR 的输出是必需的。这些基序需要与衣被蛋白 I（COPI）复合物结合，COPI 复合物是一种囊泡衣被复合物，主要介导高尔基体中的逆行货物运输。我们的结果表明，DOR 与 COPI 的相互作用，通过 C 末端尾部的非典型 COPI 基序，将 DOR 保留在高尔基体中。这些相互作用可以为细胞外信号通路对 DOR 输出和递呈的调节提供一个作用点。
