Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
Department of Biomedical Engineering, College of Engineering, Virginia Commonwealth University, Richmond, VA 23220, USA.
Sci Signal. 2020 Oct 20;13(654):eaaw3122. doi: 10.1126/scisignal.aaw3122.
Membrane trafficking processes regulate G protein-coupled receptor (GPCR) activity. Although class A GPCRs are capable of activating G proteins in a monomeric form, they can also potentially assemble into functional GPCR heteromers. Here, we showed that the class A serotonin 5-HT receptors (5-HTRs) affected the localization and trafficking of class C metabotropic glutamate receptor 2 (mGluR2) through a mechanism that required their assembly as heteromers in mammalian cells. In the absence of agonists, 5-HTR was primarily localized within intracellular compartments, and coexpression of 5-HTR with mGluR2 increased the intracellular distribution of the otherwise plasma membrane-localized mGluR2. Agonists for either 5-HTR or mGluR2 differentially affected trafficking through Rab5-positive endosomes in cells expressing each component of the 5-HTR-mGluR2 heterocomplex alone, or together. In addition, overnight pharmacological 5-HTR blockade with clozapine, but not with M100907, decreased mGluR2 density through a mechanism that involved heteromerization between 5-HTR and mGluR2. Using TAT-tagged peptides and chimeric constructs that are unable to form the interclass 5-HTR-mGluR2 complex, we demonstrated that heteromerization was necessary for the 5-HTR-dependent effects on mGluR2 subcellular distribution. The expression of 5-HTR also augmented intracellular localization of mGluR2 in mouse frontal cortex pyramidal neurons. Together, our data suggest that GPCR heteromerization may itself represent a mechanism of receptor trafficking and sorting.
膜转运过程调节 G 蛋白偶联受体（GPCR）的活性。虽然 A 类 GPCR 能够以单体形式激活 G 蛋白，但它们也可能潜在地组装成功能性 GPCR 异源二聚体。在这里，我们表明 A 类血清素 5-HT 受体（5-HTR）通过一种需要它们在哺乳动物细胞中组装为异源二聚体的机制，影响了 C 类代谢型谷氨酸受体 2（mGluR2）的定位和转运。在没有激动剂的情况下，5-HTR 主要定位于细胞内区室中，并且 5-HTR 与 mGluR2 的共表达增加了 otherwise 位于质膜上的 mGluR2 的细胞内分布。单独表达 5-HTR-mGluR2 异源二聚体的每个组成部分的细胞中，5-HTR 或 mGluR2 的激动剂通过 Rab5 阳性内体以不同的方式影响转运，或者一起。此外，用氯氮平而不是 M100907 进行过夜药理学 5-HTR 阻断通过涉及 5-HTR 和 mGluR2 之间异源二聚体形成的机制降低了 mGluR2 的密度。使用 TAT 标记的肽和不能形成 interclass 5-HTR-mGluR2 复合物的嵌合构建体，我们证明了异源二聚体化对于 5-HTR 依赖的 mGluR2 亚细胞分布的影响是必需的。5-HTR 的表达也增加了 mGluR2 在小鼠前额皮质锥体神经元中的细胞内定位。总之，我们的数据表明，GPCR 异源二聚体化本身可能代表一种受体转运和分拣的机制。
