Heterodimerization of μ- and δ-opioid receptors occurs at the cell surface only and requires receptor-G protein interactions
Heterodimerization of μ- and δ-opioid receptors occurs at the cell surface only and requires receptor-G protein interactions
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DOI：
10.1074/jbc.m500171200
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发表时间：
2005-03-25
影响因子：
4.8
通讯作者：
Loh, HH
中科院分区：
文献类型：
--
作者：
Law, PY;Erickson-Herbrandson, LJ;Loh, HH
先前报道过阿片受体的同二聚和异二聚及其功能后果。然而，这些假定的二聚体的确切性质尚未确定。在目前的研究中，通过在 EcR293 细胞中组成型表达的 mu-阿片受体 (MOR) 和松甾酮 A 诱导的 δ-阿片受体 (DOR) 表达之间形成 1:1 异二聚体的表型来研究异二聚体的性质。通过检查位于细胞表面的 MOR 和 DOR 的运输，我们确定这两种受体独立地内吞。使用MOR和DOR的细胞表面表达缺陷突变体，我们观察到这些受体的相应野生型不能挽救突变体的细胞表面表达，而拮抗剂纳洛酮可以。此外，对组成型或激动剂诱导的受体内化的研究也表明，MOR和DOR独立地内吞，并且不能“拖入”相应的野生型或内吞作用缺陷的突变体。此外，异二聚体表型可以通过用百日咳毒素预处理EcR293细胞来消除，并且可以通过删除第三个细胞内环中参与受体-G蛋白相互作用和激活的RRITR序列来调节。这些数据表明，MOR 和 DOR 异二聚体仅在细胞表面形成，阿片受体寡聚物和异三聚体 G 蛋白是观察到的 MOR-DOR 异二聚体表型的基础。
Homo- and heterodimerization of the opioid receptors with functional consequences were reported previously. However, the exact nature of these putative dimers has not been identified. In current studies, the nature of the heterodimers was investigated by producing the phenotypes of the 1: 1 heterodimers formed between the constitutively expressed mu- opioid receptor ( MOR) and the ponasterone A- induced expression of delta- opioid receptor ( DOR) in EcR293 cells. By examining the trafficking of the cell surface- located MOR and DOR, we determined that these two receptors endocytosed independently. Using cell surface expression- deficient mutants of MOR and DOR, we observed that the corresponding wild types of these receptors could not rescue the cell surface expression of the mutants, whereas the antagonist naloxone could. Furthermore, studies with constitutive or agonist- induced receptor internalization also indicated that MOR and DOR endocytosed independently and could not "drag in" the corresponding wild types or endocytosis- deficient mutants. Additionally, the heterodimer phenotypes could be eliminated by the pretreatment of the EcR293 cells with pertussis toxin and could be modulated by the deletion of the RRITR sequence in the third intracellular loop that is involved in the receptor- G protein interaction and activation. These data suggest that MOR and DOR heterodimerize only at the cell surface and that the oligomers of opioid receptors and heterotrimeric G protein are the bases for the observed MOR- DOR heterodimer phenotypes.