Functional role of the GPCR network in hypothalamic appetite regulation

超重和肥胖是全球最具挑战性的健康问题之一。详细了解能量代谢的机制是抗击这种疾病的前提。在这里，特别是涉及中央调节能源平衡的机制是至关重要的。在药物干预方面，G蛋白偶联受体(GPCR)是很好的靶点。已知一些GPCRs在下丘脑体重调节中起重要作用，如黑素皮质素4受体(MC4R)、黑素皮质素3受体(MC3R)或生长激素促分泌素受体(GHSR)。要将这些GPCR作为药物靶点，广泛了解这些受体的所有功能是前提。然而，到目前为止，对于药物设计来说，二聚或齐聚很少被考虑。在目前的资助期间，我们可以确定MC4R的一个参与二聚化的受体区域。与二聚体状态相比，二聚体形成的干扰导致了信号特性的改变。这一信息对药物开发具有潜在的意义。除了同源二聚作用外，我们还可以证明参与重量调节的GPCRs能够异寡聚。在这个星座中，任何一个受体的功能特征都可以被修改，就像MC3R/GHSR异源二聚体所证明的那样。我们推测，除了gpr-gpr相互作用外，还可能与其他蛋白质发生额外的相互作用。为了揭示MC3R和MC4R的相互作用网络，我们建立了一个基于双分子蛋白质互补分析的文库筛选方法，该文库适合于寻找新的MC3R和MC4R相互作用伙伴。最有趣的候选是确定葡萄糖转运蛋白1(Glut1)作为MC3R的相互作用伙伴。我们可以证明Glut1是MC3R功能的负调制子。事实是，GPCR和转运蛋白的相互作用被发现，这是功能相关的，表明可能的相互作用的光谱比先前假设的要大。因此，申请资助期的总体目标是对迄今为止确定的所有MC3R和MC4R在体外和体内的相互作用伙伴进行系统和详细的检查。为了这项任务，将拓宽用于确定信号特性和蛋白质-蛋白质相互作用的方法，并将建立新的方法，允许确定新发现的MC3R和MC4R相互作用伙伴的功能作用。从申请资助期获得的数据将提供关于涉及能源动态平衡的GPCRs相互作用网络的有价值的新信息，这比迄今所设想的要复杂得多。

Overweight and obesity are one of the most challenging health problems worldwide. Detailed understanding of mechanisms involved in energy metabolism is the prerequisite to combat this disease. Here, especially mechanisms involved in central regulation of energy balance are of utmost importance. For pharmacological intervention G protein coupled receptors (GPCR) represent excellent targets. In hypothalamic weight regulation some GPCRs are known to play an important role like melanocortin 4 receptor (MC4R), melanocortin 3 receptor (MC3R) or ghrelin receptor (growth hormone secretagogue receptor, GHSR). For using these GPCR as drug targets extensive understanding of all features of these receptors is the prerequisite. However, so far for drug design di- or oligomerization is only rarely considered. During the current funding period we could identify a receptor region of the MC4R that is involved in dimerization. Disturbance of dimer formation resulted in modified signalling properties compared to the dimeric state. This information is potentially of interest for drug development. Besides homodimerization we could demonstrate that GPCRs involved in weight regulation are able to heteroligomerize. In this constellation functional features of either receptor could be modified as demonstrated for the MC3R/GHSR heterodimer. We speculate that beside GPCR-GPCR interaction additional interactions with other proteins might be possible. For unravelling the network of MC3R and MC4R interaction we establish a library screen based on bimolecular protein complementation assay which was suitable to identify new interaction partners for MC3R and MC4R. The most interesting candidate was the identification of glucose transporter 1 (Glut1) as interaction partner of MC3R. We could demonstrate that Glut1 is a negative modulator of MC3R function. The fact that interaction of a GPCR and a transporter was found which is of functional relevance indicates that the spectrum of possible interaction is larger than previously assumed. Therefore the overall goal of the applied funding period is the systematic and detailed examination of all so far identified interaction partners of MC3R and MC4R in vitro and in vivo. For this task methods used for determination of signalling properties and protein-protein interactions will be widen and new methods will be establish that allow the determination of the functional role of newly identified MC3R and MC4R interaction partners. Obtained data from the applied funding period will provide valuable new information on the interacting network of GPCRs involved in energy homeostasis which is much more complex than so far supposed.