Spinophilin regulates Ca2+ signalling by binding the N-terminal domain of RGS2 and the third intracellular loop of G-protein-coupled receptors
Spinophilin regulates Ca2+ signalling by binding the N-terminal domain of RGS2 and the third intracellular loop of G-protein-coupled receptors
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DOI：
10.1038/ncb1237
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发表时间：
2005-04-01
影响因子：
21.3
通讯作者：
Muallem, S
中科院分区：
文献类型：
--
作者：
Wang, XH;Zeng, WZ;Muallem, S
G蛋白的信号传导受G蛋白信号传导调节因子（RGS）蛋白的控制，RGS蛋白可加速G α亚基的GTT活性，并以G蛋白偶联受体（GPCR）特异性方式发挥作用（1-4）。保守的RGS结构域加速Ga亚基GTdR活性（5），而可变氨基末端结构域参与GPCR识别（6）。受体识别是如何实现的尚不清楚。在这里，我们显示了结合几种GPCR（8-10）的第三个细胞内环（3 iL）的支架蛋白spinophilin（SPL）（7）结合RGS 2的N-末端结构域。SPL还结合RGS 1、RGS 4、RGS 16和GAIP。当在非洲爪蟾卵母细胞中表达时，SPL显著增加RGS 2对α-肾上腺素能受体（α AR）Ca 2+信号的抑制。值得注意的是，组成型活性突变体α AR（A293 E）（突变在3 iL中）不结合SPL，并且对RGS 2的抑制具有相对抗性。使用β AR-α AR嵌合体鉴定了（288）REKKAA（293）序列对于SPL结合和RGS 2抑制Ca 2+信号传导至关重要。此外，α AR诱发的Ca 2+信号传导对rgs 2（-/-）细胞中SPL的抑制不太敏感，对spl（-/-）细胞中RGS 2的抑制不太敏感。这些发现提供了RGS蛋白识别GPCR以赋予信号特异性的一般机制。
Signalling by G proteins is controlled by the regulator of G-protein signalling (RGS) proteins that accelerate the GTPase activity of G alpha subunits and act in a G-protein-coupled receptor (GPCR)-specific manner(1-4). The conserved RGS domain accelerates the Ga subunit GTPase activity(5), whereas the variable amino-terminal domain participates in GPCR recognition(6). How receptor recognition is achieved is not known. Here, we show that the scaffold protein spinophilin (SPL)(7), which binds the third intracellualar loop (3iL) of several GPCRs(8-10), binds the N-terminal domain of RGS2. SPL also binds RGS1, RGS4, RGS16 and GAIP. When expressed in Xenopus laevis oocytes, SPL markedly increased inhibition of alpha-adrenergic receptor (alpha AR) Ca2+ signalling by RGS2. Notably, the constitutively active mutant alpha AR(A293E) (the mutation being in the 3iL) did not bind SPL and was relatively resistant to inhibition by RGS2. Use of beta AR-alpha AR chimaeras identified the (288)REKKAA(293) sequence as essential for the binding of SPL and inhibition of Ca2+ signalling by RGS2. Furthermore, alpha AR-evoked Ca2+ signalling is less sensitive to inhibition by SPL in rgs2(-/-) cells and less sensitive to inhibition by RGS2 in spl(-/-) cells. These findings provide a general mechanism by which RGS proteins recognize GPCRs to confer signalling specificity.