RNA editing induces variation in desensitization and trafficking of 5-hydroxytryptamine 2c receptor isoforms
RNA editing induces variation in desensitization and trafficking of 5-hydroxytryptamine 2c receptor isoforms
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DOI：
10.1074/jbc.m308742200
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发表时间：
2004-01-23
影响因子：
4.8
通讯作者：
Caron, MG
中科院分区：
文献类型：
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作者：
Marion, S;Weiner, DM;Caron, MG
5-羟色胺2c受体（5-HT 2cR）在第二个细胞内环中进行RNA编辑，在人脑中产生14种不同的亚型。这种转录后事件通过降低其与G蛋白偶联的能力而显著改变受体的信号传导特性。尽管受体的非编辑形式基本上是完全组成型活性的，但编辑形式显示出较低程度的组成型活性。我们已经使用了两种广泛编辑的受体亚型，VGV和VSV，以及非编辑的INI亚型来研究组成型受体活性的变化如何影响这些亚型与HEK 293细胞中脱敏机制的组分的相互作用和运输。我们发现，细胞表面表达的5-HT 2cR减少平行的异构体的组成性活动增加。各种亚型的亚细胞分布依赖于它们与β抑制蛋白2相互作用的能力，β抑制蛋白2与每种亚型的组成性活性水平相关。我们观察到，激动剂独立的相互作用betaarrestin 2与组成型活性5-HT 2cR亚型逆转的反向激动剂治疗促进受体重新分布到细胞表面。即使在反向激动剂存在的情况下，G蛋白偶联受体激酶（GRK 2）的过表达也能够稳定β抑制素2与组成型活性5-HT 2cR亚型的相互作用。两者合计，我们的观察表明，组成型活性5-HT 2cR亚型自发内化的激动剂独立的方式。该内吞过程由GRK/β抑制蛋白依赖性机制介导，并且与RNA编辑的受体变体的组成性活性状态直接相关。因此，组成型活性受体的最终生理输出可能不仅取决于其激动剂非依赖性活性，而且还取决于其与GRKs和β抑制蛋白的相互作用。
The 5-hydroxytryptamine2c receptor (5-HT2cR) is subjected to RNA editing, in the second intracellular loop, generating 14 different isoforms in human brain. This post-transcriptional event markedly alters the signaling properties of the receptor by reducing its ability to couple to G-proteins. Although the non-edited form of the receptor is essentially fully constitutively active, edited forms show lesser degrees of constitutive activity. We have used two extensively edited receptor isoforms, VGV and VSV, and the non-edited INI isoform to investigate how variations in constitutive receptor activity affect the trafficking and the interaction of these isoforms with components of the desensitization machinery in HEK 293 cells. We found that cell surface expression of the 5-HT2cR decreased in parallel with increased constitutive activity of the isoforms. The subcellular distribution of the various isoforms was dependent of their ability to interact with betaarrestin2, which correlated with the constitutive activity level of each isoform. We observed that the agonist-independent interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms was reversed by inverse agonist treatments promoting receptor redistribution to the cell surface. Overexpression of a G-protein-coupled receptor kinase (GRK2) was able to stabilize the interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms even in the presence of inverse agonists. Taken together, our observations indicate that the constitutively active 5-HT2cR isoforms are spontaneously internalized in an agonist-independent manner. This endocytosis process is mediated by a GRK/betaarrestin-dependent mechanism and is directly correlated with the constitutive activity status of the RNA edited receptor variants. Thus the ultimate physiological output of constitutively active receptors may be determined not only by their agonist-independent activity but also by their interactions with GRKs and betaarrestin.