Disease-causing Mutation in PKR2 Receptor Reveals a Critical Role of Positive Charges in the Second Intracellular Loop for G-protein Coupling and Receptor Trafficking
Disease-causing Mutation in PKR2 Receptor Reveals a Critical Role of Positive Charges in the Second Intracellular Loop for G-protein Coupling and Receptor Trafficking
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PKR2 受体的致病突变揭示了第二个细胞内环中的正电荷对于 G 蛋白偶联和受体运输的关键作用
DOI：
10.1074/jbc.m111.223784
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发表时间：
2011-05-13
影响因子：
4.8
通讯作者：
Li, Jia-Da
中科院分区：
文献类型：
--
作者：
Peng, Zhen;Tang, Yong;Li, Jia-Da
促动力素是一对信号因子，通过与两种密切相关的G蛋白偶联受体PKR1和PKR2结合，参与多种生理过程。最近发现，促动力素2（PK2）和PKR2的突变与卡尔曼综合征和/或特发性低促性腺激素性性腺功能减退症相关，这些疾病的特征为青春期延迟和不育。然而，对于PKRs如何与G蛋白相互作用并激活G蛋白以引发信号转导，人们知之甚少。在本研究中，我们利用位于PKR2第二个细胞内环（IL2）中的一个疾病相关突变（R164Q），来研究IL2环在细胞信号传导、G蛋白结合和受体转运中的作用。R164Q突变型PKR2显示出正常的细胞表面表达和配体结合能力。然而，R164Q突变使PKR2信号传导消失。我们证明，R164Q突变破坏了IL2环与Gα(q)、Gα(i)和Gα(16)蛋白的相互作用。该位置的带正电荷氨基酸是正常功能所必需的，且信号传导的效力和效能取决于正电荷的净数量。我们还证明，精氨酸 - 164的相互作用伙伴可能定位于Gα(q)蛋白C末端的五个残基中。一系列突变分析表明，IL2环C末端的碱性氨基酸可能在G蛋白偶联受体（GPCRs）中协同发挥作用。此外，R164Q突变还导致PKR2在配体诱导下的内吞作用降至最低。由于许多GPCRs在IL2环C末端具有结构同源性，我们的研究结果可能在理解GPCRs的结构和功能方面具有普遍适用性。
Prokineticins are a pair of signal factors involved in many physiological processes by binding to two closely related G-protein-coupled receptors, PKR1 and PKR2. Recently, mutations in prokineticin 2 (PK2) and PKR2 are found to be associated with Kallmann syndrome and/or idiopathic hypogonadotropic hypogonadism, disorders characterized by delayed puberty and infertility. However, little is known how PKRs interact and activate G-proteins to elicit signal transduction. In the present study, we took advantage of one disease-associated mutation (R164Q) located in the second intracellular (IL2) loop of PKR2, to investigate the role of IL2 loop in the cell signaling, G-protein binding and receptor trafficking. R164Q mutant PKR2 showed normal cell surface expression and ligand binding capacity. However, the PKR2 signaling was abolished by R164Q mutation. We demonstrated that R164Q mutation disrupted the interaction of IL2 loop to the G alpha(q), G alpha(i), and G alpha(16)-proteins. A positive-charged amino acid at this position is required for proper function, and the signaling efficacy and potency depend on the net amount of positive charges. We also demonstrated that the interactive partner of Arg-164 may localize in the C-terminal five residues of G alpha(q)-protein. Aseries of mutation analysis indicated that the basic amino acids at the C terminus of IL2 loop may function cooperatively in GPCRs. Furthermore, R164Q mutation also results in minimal ligand-induced endocytosis of PKR2. As many GPCRs share structural homology in the C terminus of IL2 loop, our findings may have general application in understanding structure and function of GPCRs.