Structural Mapping and Functional Characterization of Zebrafish Class B G-Protein Coupled Receptor (GPCR) with Dual Ligand Selectivity towards GLP-1 and Glucagon.
Structural Mapping and Functional Characterization of Zebrafish Class B G-Protein Coupled Receptor (GPCR) with Dual Ligand Selectivity towards GLP-1 and Glucagon.
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DOI：
10.1371/journal.pone.0167718
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Mojsov S
中科院分区：
文献类型：
--
作者：
Oren DA;Wei Y;Skrabanek L;Chow BK;Mommsen T;Mojsov S
GLP-1和胰高血糖素通过与属于B类G蛋白偶联受体（GPCR）的特异性受体结合后启动的代谢途径网络调节葡萄糖代谢。目前正在评估胰高血糖素的治疗潜力，而GLP-1已经用于治疗2型糖尿病和肥胖症。开发第二代基于GLP-1的治疗药物取决于对GLP-1受体（GLP-1 R）及其配体GLP-1之间相互作用的分子和结构理解。GLP-1和胰高血糖素之间以及hGLP-1 R和人胰高血糖素受体（hGCGR）之间存在相当大的序列保守性，但每种受体仅识别其自身的特异性配体。鱼和青蛙中的胰高血糖素受体也仅对胰高血糖素而非GLP-1表现出配体选择性。基于竞争性结合实验和细胞内cAMP增加的测定，我们在这里证明，在斑马鱼（Danio rerio）的GPCR表现出对GLP-1和胰高血糖素的双配体选择性，在哺乳动物中没有发现的特征。此外，在hGLP-1 R和hGCGR中发现的许多结构特征也在该斑马鱼GPCR（zfGPCR）中发现。我们通过基于其部分和互补晶体结构将其序列和结构特征映射到hGLP-1 R和hGCGR上来证明这一点。因此，我们认为zfGPCR代表了双重GLP-1 R/GCGR。这三种受体之间的主要差异在于连接其N端胞外结构域（NECD）与其跨膜结构域的茎区，以及zfGLP-1 R/GCGR中NECD中不存在环3。这些观察结果表明，GLP-1和胰高血糖素与环3和茎区之间的相互作用可能在配体结合和活化后诱导hGLP-1 R和hGCGR的不同构象变化，从而导致其天然配体的选择性识别。
GLP-1 and glucagon regulate glucose metabolism through a network of metabolic pathways initiated upon binding to their specific receptors that belong to class B G-protein coupled receptors (GPCRs). The therapeutic potential of glucagon is currently being evaluated, while GLP-1 is already used in the treatment of type 2 diabetes and obesity. Development of a second generation of GLP-1 based therapeutics depends on a molecular and structural understanding of the interactions between the GLP-1 receptor (GLP-1R) and its ligand GLP-1. There is considerable sequence conservation between GLP-1 and glucagon and between the hGLP-1R and human glucagon receptor (hGCGR), yet each receptor recognizes only its own specific ligand. Glucagon receptors in fish and frogs also exhibit ligand selectivity only towards glucagon and not GLP-1. Based on competitive binding experiments and assays of increase in intracellular cAMP, we demonstrate here that a GPCR in zebrafish (Danio rerio) exhibits dual ligand selectivity towards GLP-1 and glucagon, a characteristic not found in mammals. Further, many structural features found in hGLP-1R and hGCGR are also found in this zebrafish GPCR (zfGPCR). We show this by mapping of its sequence and structural features onto the hGLP-1R and hGCGR based on their partial and complementary crystal structures. Thus, we propose that zfGPCR represents a dual GLP-1R/GCGR. The main differences between the three receptors are in their stalk regions that connect their N-terminal extracellular domains (NECDs) with their transmembrane domains and the absence of loop 3 in the NECD in zfGLP-1R/GCGR. These observations suggest that the interactions between GLP-1 and glucagon with loop 3 and the stalk regions may induce different conformational changes in hGLP-1R and hGCGR upon ligand binding and activation that lead to selective recognition of their native ligands.
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