Islet GPCR regulation by GRKs and RGS proteins

GRK 和 RGS 蛋白对胰岛 GPCR 的调节

• 批准号: 2605189
• 金额: --
• 依托单位: King's College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2605189
• 关键词: Islet; GPCR; regulation; GRKs; RGS

Over 400 million people worldwide currently have type 2 diabetes (T2D), in which peripheral cells show reduced sensitivity toinsulin and islet beta-cells do not secrete sufficient insulin to maintain low blood glucose levels. Declining beta-cell number isthe fundamental problem in T2D but current pharmacotherapies do not effectively increase functional beta-cell mass. Gprotein-coupled receptors (GPCRs) are the targets for many clinically used therapeutics, and our "GPCRome" mapping has indicated thathuman islets express nearly 300 GPCRs, at least some of which could be harnessed therapeutically to treat T2D(1-3).It is now clear that GPCR regulation extends beyond agonist binding, activation of associated G proteins and modifications in effector-mediated downstream signalling. Thus,GPCRs are phosphorylated by GPCR kinases (GRKs)after their activation by agonists andrecruited arrestin proteins then bind to phosphorylated GPCRs to inhibit their interactions with proteins which, in turn, reduces downstream signallingof active GPCRs(reviewed in 4). To date seven human GRKs have been cloned and characterised, and two non-visual arrestins have been identified(4). In addition the desensitising effects of GRKs and arrestins, regulator of protein signalling (RGS) proteins provide another level of GPCR regulation in which conserved amino acids within the RGS domainbind toconserved amino acids in the switch regionswithin subunitstoincrease GTP hydrolysis and terminate signalling(5). While progress has been made in our understanding of the roles of b-arrestins in b-cell function (6) very little is known about GRK and RGS expression and function in islets,and this will be examined in this PhD project to better understand the potential of targeting islet GPCRs to treat T2D. In addition, if data generated during this project demonstrate that inhibition of GRKs and/or RGS proteins improves insulin secretion and protects beta-cells from apoptosis this will be of importance in optimising islet functional mass prior to transplantation in T1D. The necessary techniques are in current use in the supervisors' labs (1,2, 7-11)and full training will be providedto Jessica.Aim of the investigation-This PhD project has 4 main objectives:1.Quantify mRNAs encoding GRKs and RGS proteins in human islets from low and high BMI donors and determine changes that occur under conditions of obesity.2.Identify cellular localisation of GRKs and RGS proteins in pancreas samples from lean and obese humans and mice.3.Determine the effects of selective GRK and RGS inhibitors on GPCR agonist-regulated islet function.4.Determine functional effects of deleting key GRKs and RGS proteinsin beta-cells.

目前全球有超过4亿人患有2型糖尿病（T2 D），其中外周细胞对胰岛素的敏感性降低，胰岛β细胞不能分泌足够的胰岛素来维持低血糖水平。β细胞数量下降是T2 D的根本问题，但目前的药物治疗不能有效增加功能性β细胞质量。G蛋白偶联受体（GPCR）是许多临床上使用的治疗剂的靶点，并且我们的“GPCR Rome”作图已经表明人类胰岛表达近300种GPCR，其中至少一些可以在治疗上用于治疗T2 D（1-3）APCR调节延伸到激动剂结合、相关G蛋白的激活和效应物介导的下游信号传导的修饰之外。因此，GPCR在被激动剂激活后被GPCR激酶（GRKs）磷酸化，然后募集的抑制蛋白结合磷酸化的GPCR以抑制它们与蛋白质的相互作用，这反过来又减少了活性GPCR的下游信号传导（综述见4）。到目前为止，已经克隆并鉴定了7种人类GRKs，并鉴定了2种非视觉抑制蛋白（4）。除了GRKs和抑制蛋白的脱敏作用外，蛋白质信号传导调节因子（RGS）蛋白还提供了另一种水平的GPCR调节，其中RGS结构域中的保守氨基酸与亚基内开关区域中的保守氨基酸结合，以增加GTP水解并终止信号传导（5）。虽然我们对b-抑制蛋白在b细胞功能中的作用的理解已经取得了进展（6），但对胰岛中GRK和RGS的表达和功能知之甚少，这将在本博士项目中进行研究，以更好地了解靶向胰岛GPCR治疗T2 D的潜力。此外，如果在该项目期间产生的数据表明GRKs和/或RGS蛋白的抑制改善胰岛素分泌并保护β细胞免于凋亡，则这对于在T1 D中移植之前优化胰岛功能质量将是重要的。必要的技术目前在监督员的实验室中使用（1，2，7-11）和全面的培训将提供给杰西卡。调查的目的-这个博士项目有4个主要目标：1.定量低和高BMI供体的人类胰岛中编码GRK和RGS蛋白的mRNA，并确定肥胖条件下发生的变化。2.确定瘦和肥胖人类和小鼠胰腺样本中GRK和RGS蛋白的细胞定位。3.确定选择性GRK和RGS抑制剂对GPCR激动剂的影响-4.确定删除β细胞中关键GRKs和RGS蛋白的功能效应。