Xiao Yuanyuan, Han Junfeng, Wang Qianqian, Mao Yueqin, Wei Meilin, Jia Weiping, Wei Li
Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, Shanghai Key Clinical Center for Metabolic Disease, Shanghai 200233, China.
J Cell Biochem. 2017 Nov;118(11):3616-3626. doi: 10.1002/jcb.26207. Epub 2017 Aug 2.
Glucagon-like peptide 1 (GLP-1) exerts multiple effects on metabolism through its receptor, GLP-1R, in the liver. Activation and transduction of GLP-1R require complex interactions of largely unknown accessory proteins, and these processes are crucial to the response to endoplasmic reticulum (ER) stress. Using the membrane-based split ubiquitin yeast two-hybrid system (MYTH) and a human liver cDNA library, we obtained the human GLP-1R interactome and identified SERP1 as a potential interacting protein based on its ability to stabilize membrane proteins and facilitate N-linked glycosylation. GLP-1R and SERP1 were co-expressed in HEK-293 cells, and their interaction was confirmed by co-immunoprecipitation. We then found that overexpression of SERP1 could rescue GLP-1R glycosylation after application of tunicamycin to block N-linked glycosylation. SERP1 overexpression also attenuated exendin-4-stimulated cAMP accumulation and AMPK activation. However, the glycosylation and function of mutant GLP-1R, in which all three sites for N-linked glycosylation were mutated, were not increased with overexpression of SERP1. Moreover, as a GLP-1R interactor, SERP1 could also partly reverse the accumulation of tunicamycin-induced ER stress. Taken together, our findings identify a group of proteins that interact with GLP-1R and show that one specific interacting protein, SERP1, has an important role in facilitating the glycosylation of GLP-1R and rescuing its activities after ER stress induced by tunicamycin. J. Cell. Biochem. 118: 3616-3626, 2017. © 2017 Wiley Periodicals, Inc.
胰高血糖素样肽1（GLP-1）通过其在肝脏中的受体GLP-1R对代谢产生多种影响。GLP-1R的激活和信号转导需要大量未知辅助蛋白的复杂相互作用，而这些过程对于内质网（ER）应激反应至关重要。利用基于膜的分裂泛素酵母双杂交系统（MYTH）和人肝脏cDNA文库，我们获得了人GLP-1R相互作用组，并基于其稳定膜蛋白和促进N-连接糖基化的能力，将SERP1鉴定为一种潜在的相互作用蛋白。GLP-1R和SERP1在HEK-293细胞中共表达，其相互作用通过免疫共沉淀得到证实。然后我们发现，在应用衣霉素阻断N-连接糖基化后，SERP1的过表达可以挽救GLP-1R的糖基化。SERP1的过表达还减弱了艾塞那肽-4刺激的cAMP积累和AMPK激活。然而，N-连接糖基化的所有三个位点均发生突变的突变型GLP-1R的糖基化和功能并未因SERP1的过表达而增加。此外，作为GLP-1R相互作用蛋白，SERP1还可以部分逆转衣霉素诱导的ER应激的积累。综上所述，我们的研究结果鉴定了一组与GLP-1R相互作用的蛋白，并表明一种特定的相互作用蛋白SERP1在促进GLP-1R糖基化以及挽救衣霉素诱导的ER应激后的活性方面具有重要作用。《细胞生物化学杂志》118: 3616 - 3626, 2017。© 2017威利期刊公司
