The internalization of the M2 and M4 muscarinic acetylcholine receptors involves distinct subsets of small G-proteins.
The internalization of the M2 and M4 muscarinic acetylcholine receptors involves distinct subsets of small G-proteins.
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M2 和 M4 毒蕈碱乙酰胆碱受体的内化涉及小 G 蛋白的不同子集。
DOI：
10.1016/j.lfs.2008.01.013
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发表时间：
2008
期刊：
影响因子：
6.1
通讯作者：
Nathanson,NeilM
中科院分区：
文献类型：
--
作者：
Reiner,Cindy;Nathanson,NeilM
细胞表面受体的内吞作用存在多种机制。虽然M1、M3和M4亚型的毒蕈碱乙酰胆碱受体通过网格蛋白包被囊泡的充分表征的机制内化，但M2内吞作用的机制尚未明确。由于M2和M4受体通过相同的第二信使传递信号，但通过不同的途径内化，我们测试了几种小G蛋白对激动剂诱导的JEG-3人绒毛膜癌细胞中M2和M4内吞的调节能力。显性阴性Rab 5以及野生型和显性阴性Rab 11抑制M4的内吞作用，但不抑制M2的内吞作用。与此相反，显性阴性Arf 6以及野生型Rab 22增加M2，但不M4的内吞作用。我们用免疫细胞化学显示，在未受刺激的细胞中，M2和M4受体共定位于细胞表面，而在刺激后，M2和M4在不同的囊泡隔室。在这项研究中，我们证明，激动剂诱导的M2受体的内化利用Arf 6，Rab 22依赖性途径，而M4受体经历激动剂诱导的内化通过Rab 5，Rab 11依赖性途径。此外，我们发现Rab 15和RhoA不参与JEG-3细胞中的任何一种途径。
Multiple mechanisms exist for the endocytosis of receptors from the cell surface. While the M1, M3, and M4subtypes of muscarinic acetylcholine receptors internalize through the well-characterized mechanism of clathrin coated vesicles, the mechanism of M2endocytosis is not well defined. Because the M2and M4receptors transduce their signals through the same second messengers but internalize though different pathways, we tested the ability of several small G-proteins to regulate the agonist-induced endocytosis of M2and M4in JEG-3 human choriocarcinoma cells. Dominant-negative Rab5 as well as both wild-type and dominant-negative Rab11 inhibited M4but not M2endocytosis. In contrast, a dominant-negative Arf6 as well as wild-type Rab22 increased M2but not M4endocytosis. We used immunocytochemistry to show that in unstimulated cells, the M2and M4receptors co-localize on the cell surface, whereas after stimulation M2and M4are in distinct vesicular compartments. In this study, we demonstrate that agonist-induced internalization of the M2receptor utilizes an Arf6, Rab22 dependent pathway, while the M4receptor undergoes agonist-induced internalization through a Rab5, Rab11 dependent pathway. Additionally, we show that Rab15 and RhoA are not involved in either pathway in JEG-3 cells.