Disease-associated extracellular loop mutations in the adhesion G protein-coupled receptor G1 (ADGRG1; GPR56) differentially regulate downstream signaling
Disease-associated extracellular loop mutations in the adhesion G protein-coupled receptor G1 (ADGRG1; GPR56) differentially regulate downstream signaling
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DOI：
10.1074/jbc.m117.780551
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发表时间：
2017-06-09
影响因子：
4.8
通讯作者：
Hall, Randy A.
中科院分区：
文献类型：
--
作者：
Kishore, Ayush;Hall, Randy A.
粘附G蛋白偶联受体ADGRG 1（G1;也称为GPR 56）的突变是神经系统疾病双侧额顶叶多微脑回症的基础。迄今为止研究的G1中的疾病相关突变被认为通过破坏受体运输或信号传导活性而诱导受体功能的完全丧失。鉴于G1和其他粘附G蛋白偶联受体的N端截短已被证明显着增加受体的组成性信号传导，我们研究了两种不同的双边额顶叶多微回诱导细胞外环突变（R565 W和L 640 R）的情况下，全长和N端截短（Delta NT）G1。有趣的是，我们发现这些突变减少了HEK-293细胞中全长G1的表面表达，但没有G1-Delta NT。此外，突变消除了受体介导的血清应答因子荧光素酶的激活，这是G α（12/13）介导的信号传导的经典测量，但对G1介导的活化T细胞核因子（NFAT）荧光素酶的信号传导没有影响。鉴于这些差异信号传导结果，我们试图进一步阐明G1可以激活NFAT荧光素酶的途径。我们没有发现证据表明NFAT的Delta NT激活依赖于G α（q/11）介导的或β-抑制蛋白介导的信号传导，而是涉及G β γ亚基的释放和钙通道的激活。这些研究结果表明，疾病相关的突变G1细胞外环差异改变受体贩运，这取决于N末端的存在，并差异改变不同的下游途径的信号。
Mutations to the adhesion G protein-coupled receptor ADGRG1 (G1; also known as GPR56) underlie the neurological disorder bilateral frontoparietal polymicrogyria. Disease-associated mutations in G1 studied to date are believed to induce complete loss of receptor function through disruption of either receptor trafficking or signaling activity. Given that N-terminal truncation of G1 and other adhesion G protein-coupled receptors has been shown to significantly increase the receptors' constitutive signaling, we examined two different bilateral frontoparietal polymicrogyria-inducing extracellular loop mutations (R565W and L640R) in the context of both full-length and N-terminally truncated (Delta NT) G1. Interestingly, we found that these mutations reduced surface expression of full-length G1 but not G1-Delta NT in HEK-293 cells. Moreover, the mutations ablated receptor-mediated activation of serum response factor luciferase, a classic measure of G alpha(12/13)-mediated signaling, but had no effect on G1-mediated signaling to nuclear factor of activated T cells (NFAT) luciferase. Given these differential signaling results, we sought to further elucidate the pathway by which G1 can activate NFAT luciferase. We found no evidence that Delta NT activation of NFAT is dependent on G alpha(q/11)-mediated or beta-arrestin-mediated signaling but rather involves liberation of G beta gamma subunits and activation of calcium channels. These findings reveal that disease-associated mutations to the extracellular loops of G1 differentially alter receptor trafficking, depending on the presence of the N terminus, and differentially alter signaling to distinct downstream pathways.