Differential subcellular localization of RIC-3 Isoforms and their role in determining 5-HT3 receptor composition
Differential subcellular localization of RIC-3 Isoforms and their role in determining 5-HT3 receptor composition
复制标题
DOI：
10.1074/jbc.m703899200
复制
发表时间：
2007-09-07
影响因子：
4.8
通讯作者：
Connolly, Christopher N.
中科院分区：
文献类型：
--
作者：
Cheng, Aixin;Bollan, Karen A.;Connolly, Christopher N.
RIC-3已被鉴定为参与促进哺乳动物细胞中烟碱乙酰胆碱和5-HT 3受体的功能性表达的伴侣分子。在这项研究中，我们研究了RIC-3a（同种型a）和截断同种型（同种型d）对RIC-3定位，移动性和聚集的影响，以及其对哺乳动物细胞中5-HT 3受体组成的影响。人RIC-3a具有将其靶向内质网的氨基末端信号序列，在内质网中其分布在网状网络内，通常形成大的弥漫性“光滑”和明亮的“晕”结构。RIC-3a在这些隔室内和隔室之间具有高度移动的性。尽管RIC-3a有聚集的倾向，但其表达增强了表面5-HT 3A（同源）受体的水平。相反，RIC-3 a对异聚体5-HT 3A/B受体的表面表达发挥抑制作用。RIC-3d表现出改变的亚细胞分布，定位于内质网，大的弥漫性浮油，管泡状结构，和高尔基体。内质网和高尔基体之间的双向运输表明，RIC-3d组成性地在这两个隔室之间循环。支持RIC-3a的大卷曲螺旋结构域负责蛋白质聚集，缺少该胞质结构域的RIC-3d不聚集或诱导明亮聚集体的形成。不管这些差异如何，同种型d仍然能够增强同聚体5-HT 3受体表达，并抑制异聚体5-HT 3受体表达。因此，RIC-3的两种亚型在决定5-HT 3受体组成中起作用。
RIC-3 has been identified as a chaperone molecule involved in promoting the functional expression of nicotinic acetylcholine and 5-HT3 receptors in mammalian cells. In this study, we examined the effects of RIC-3a ( isoform a) and a truncated isoform ( isoform d) on RIC-3 localization, mobility, and aggregation and its effect on 5-HT3 receptor composition in mammalian cells. Human RIC-3a possesses an amino-terminal signal sequence that targets it to the endoplasmic reticulum where it is distributed within the reticular network, often forming large diffuse "slicks" and bright "halo" structures. RIC-3a is highly mobile within and between these compartments. Despite the propensity for RIC-3a to aggregate, its expression enhances the level of surface 5-HT3A (homomeric) receptors. In contrast, RIC-3a exerts an inhibitory action on the surface expression of heteromeric 5-HT3A/B receptors. RIC-3d exhibits an altered subcellular distribution, being localized to the endoplasmic reticulum, large diffuse slicks, tubulo-vesicular structures, and the Golgi. Bidirectional trafficking between the endoplasmic reticulum and Golgi suggests that RIC-3d constitutively cycles between these two compartments. In support of the large coiled-coil domain of RIC-3a being responsible for protein aggregation, RIC-3d, lacking this cytoplasmic domain, does not aggregate or induce the formation of bright aggregates. Regardless of these differences, isoform d is still capable of enhancing homomeric, and inhibiting heteromeric, 5-HT3 receptor expression. Thus, both isoforms of RIC-3 play a role in determining 5-HT3 receptor composition.