Role of internalization in AT(1A) receptor function in proximal tubule epithelium.
Role of internalization in AT(1A) receptor function in proximal tubule epithelium.
复制标题
内化在近曲小管上皮 AT(1A) 受体功能中的作用。
DOI：
10.1152/ajprenal.00118.2001
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Linas,StuartL
中科院分区：
文献类型：
--
作者：
Thekkumkara,Thomas;Linas,StuartL
血管紧张素 II (ANG II) 通过近曲小管上皮细胞顶面和基底外侧表面的血管紧张素 I 型 (AT1) 受体发挥作用，增加近曲小管的钠重吸收。顶端和基底外侧受体在暴露于 ANG II 后内化，但内化在受体信号传导和运输中的作用尚不清楚。为了确定受体内化在 ANG II 介导的受体信号传导和钠转运中的作用，我们在负鼠肾细胞中稳定表达全长和截短的 AT1A 受体。 ANG II 刺激后，顶端和基底外侧表面的野生型受体迅速内化，抑制腺苷酸环化酶，并增加跨细胞钠转运。 AT1A 受体 (TL314) 胞质尾部的截断导致受体在顶端和基底外侧表面表达，但不会内化、抑制腺苷酸环化酶或增加钠转运。由于细胞质尾部含有假定的 G 蛋白偶联位点，因此设计了保留 G 蛋白相互作用位点完整的突变受体。表达截短（TK333）或缺失（Del 315-329）的细胞也未能内化。当 ANG II 添加到 TK333 或 Del 315-329 的基底外侧表面时，腺苷酸环化酶活性受到抑制，钠转运增加。相比之下，顶端添加 ANG II 与腺苷酸环化酶的减少或钠转运的增加无关。总之，内化途径对于极化近端小管上皮细胞中 AT1A 受体功能很重要。顶端 AT1A 受体在与 G 蛋白相互作用并发出 cAMP 信号之前内化。相反，基底外侧 AT1A 受体与 G 蛋白相互作用并发出 cAMP 信号但不内化。
Angiotensin II (ANG II), acting through angiotensin type I (AT1) receptors on apical and basolateral surfaces of proximal tubule epithelial cells, increases sodium reabsorption in proximal tubules. Apical and basolateral receptors internalize after exposure to ANG II, but the role of internalization in receptor signaling and transport is not well defined. To determine the role of receptor internalization in ANG II-mediated receptor signaling and sodium transport, we stably expressed full-length and truncated AT1Areceptors in opossum kidney cells. After stimulation with ANG II, wild-type receptors on apical and basolateral surfaces rapidly internalized, inhibited adenylate cyclase, and increased transcellular sodium transport. Truncation of the cytoplasmic tail of the AT1Areceptor (TL314) resulted in receptors that were expressed on apical and basolateral surfaces but did not internalize, inhibit adenylate cyclase, or increase sodium transport. Because the cytoplasmic tail contains putative G protein coupling sites, mutant receptors that leave G protein interaction sites intact were designed. Cells expressing the truncation (TK333) or deletion (Del 315–329) also failed to internalize. When ANG II was added to basolateral surfaces of TK333 or Del 315–329, adenylate cyclase activity was inhibited and sodium transport was increased. In contrast, apical addition of ANG II was not associated with decreases in adenylate cyclase or increases in sodium transport. In conclusion, internalization pathways are important for AT1Areceptor function in polarized proximal tubule epithelial cells. Apical AT1Areceptors internalize before they interact with G proteins and signal cAMP. In contrast, basolateral AT1Areceptors interact with G proteins and signal cAMP without internalizing.