Characterization of the novel human serotonin receptor subunits 5-HT3C, 5-HT3D, and 5-HT3E
Characterization of the novel human serotonin receptor subunits 5-HT3C, 5-HT3D, and 5-HT3E
复制标题
DOI：
10.1124/mol.106.032144
复制
发表时间：
2007-07-01
影响因子：
3.6
通讯作者：
Bruess, Michael
中科院分区：
文献类型：
--
作者：
Niesler, Beate;Walstab, Jutta;Bruess, Michael
在5-羟色胺受体家族中，5-羟色胺-3(5-HT3)受体是唯一的配体门控离子通道。它由5个亚基组成，其中5-HT3A和5-HT3B亚基的特性最好。然而，一些研究报道了天然5-HT3受体的功能多样性，这不能完全基于5-HT3A和5-HT3B亚基来解释。在进一步发现5-HT3 5-羟色胺受体编码基因HTR3C、HTR3D和HTR3E后，我们研究了这些新的候选基因及其亚型5-HT3Ea是否能够形成功能性的5-HT3受体复合体。利用免疫荧光和免疫沉淀研究异源表达的蛋白，我们发现每个候选蛋白都与5-HT3A共组装。为了研究新的亚基是否调节5-HT3受体的功能，我们在人胚胎肾脏293细胞中进行了放射配基结合分析和钙内流研究。我们的实验表明，单独的5-HT3C、5-HT3D、5-HT3E和5-HT3Ea亚基不能形成功能性受体。然而，与5-HT3A共表达会导致具有不同5-羟色胺活性的功能异构体复合体的形成。两种激动剂和拮抗剂对同构体5-HT3A和异构体复合体的效价几乎相同。然而，5-羟色胺对5-HT3A/D和5-HT3A/E受体的作用增强，这与5-HT3A受体的表面表达增加是一致的。相反，5-HT3A/C和5-HT3A/EA受体降低了5-羟色胺的药效。这些数据首次表明，新的5-HT3亚基能够形成异构体5-HT3受体，与同构体5-HT3A受体相比，它们表现出不同的功能特性。
Within the family of serotonin receptors, the 5-hydroxytryptamine-3 (5-HT3) receptor is the only ligand-gated ion channel. It is composed of five subunits, of which the 5-HT3A and 5-HT3B subunits are best characterized. Several studies, however, have reported on the functional diversity of native 5-HT3 receptors, which cannot solely be explained on the basis of the 5-HT3A and 5-HT3B subunits. After our discovery of further putative 5-HT3 serotonin receptor-encoding genes, HTR3C, HTR3D, and HTR3E, we investigated whether these novel candidates and the isoform 5-HT3Ea are able to form functional 5-HT3 receptor complexes. Using immunofluorescence and immunoprecipitation studies of heterologously expressed proteins, we found that each of the respective candidates coassembles with 5-HT3A. To investigate whether the novel subunits modulate 5-HT3 receptor function, we performed radioligand-binding assays and calcium-influx studies in human embryonic kidney 293 cells. Our experiments revealed that the 5-HT3C, 5-HT3D, 5-HT3E, and 5-HT3Ea subunits alone cannot form functional receptors. Coexpression with 5-HT3A, however, results in the formation of functional heteromeric complexes with different serotonin efficacies. Potencies of two agonists and antagonists were nearly identical with respect to homomeric 5-HT3A and heteromeric complexes. However, 5-HT showed increased efficacy with respect to 5-HT3A/D and 5-HT3A/E receptors, which is consistent with the increased surface expression compared with 5-HT3 Areceptors. In contrast, 5-HT3A/C and 5-HT3A/Ea receptors exhibited decreased 5-HT efficacy. These data show for the first time that the novel 5-HT3 subunits are able to form heteromeric 5-HT3 receptors, which exhibit quantitatively different functional properties compared with homomeric 5-HT3A receptors.