Elongation factor 1A1 and the regulation of protein synthesis and cytoskeleton dynamics during lipid-induced stress

延伸因子（EEF） 1A1在肝脏、胰腺和脑中表达，通过促进aa- trna -核糖体结合参与蛋白质合成。EEF1A1还在肌动蛋白细胞骨架调节和应激反应中的凋亡/anoikis中具有兼职功能。EEF1A1的规范和非规范功能是否参与细胞对代谢应激的反应尚不清楚。该计划的目标是阐明蛋白质合成，肌动蛋白细胞骨架调节和脂质过载诱导的细胞应激反应之间的联系。脂毒性是指非脂肪细胞中异位脂质沉积导致细胞功能障碍、细胞死亡和最终组织功能障碍的过程。由于许多脂质代谢过程发生在内质网，分泌细胞类型中的脂毒性条件伴随着内质网应激和未折叠蛋白反应（UPR）的快速诱导。UPR通过停止蛋白质合成来恢复体内平衡，同时促进蛋白质折叠和降解。然而，严重或长时间的应激会引发内质网应激反应（ERSR），从而导致细胞死亡。ERSR涉及蛋白质合成的重新启动，以产生促炎和促凋亡因子，这是一种有害的合成代谢反应。EEF1A1介导内质网应激，是脂毒性细胞死亡的关键介质。我们最近发现，用一种特定的抑制剂dideminb阻断EEF1A1的蛋白质合成活性，可以降低肝细胞中的脂毒性细胞死亡。此外，用dideminin B进行急性干预可以改善严重脂肪肝小鼠的肝内质网应激和相关炎症。但EEF1A1参与细胞应激反应和促进肝细胞脂毒性的确切机制尚不清楚。也不清楚EEF1A1是否参与其他富含er的细胞类型的脂肪毒性，特别是胰腺β细胞。因此，该项目的短期目标是确定EEF1A1在(1)培养的肝细胞和胰腺β细胞以及(2)饮食诱导的组织脂质积累小鼠的肝脏和胰腺中对过量脂质积累的细胞反应中的比较功能。该项目的长期目标是了解EEF1A1在整个身体代谢组织（包括肝脏、胰腺、心肌和骨骼肌）对过量脂肪的细胞应激反应中的作用的整体机制，部分通过使用独特的转基因EEF1A1 - egfp小鼠模型来测试EEF1A1在高脂肪饮食诱导的代谢应激反应中的表达模式。总体而言，该项目将确定EEF1A1的规范和非规范功能如何参与内质网应激反应和细胞过度脂质积累诱导的细胞死亡过程，从而进一步了解脂肪毒性和EEF1A1的多种功能。

Elongation factor (EEF) 1A1 is expressed in liver, pancreas, and brain, and participates in protein synthesis by promoting aa-tRNA-ribosome binding. EEF1A1 also has moonlighting' functions in actin cytoskeleton regulation, and in apoptosis/anoikis in response to stress. Whether both the canonical and non-canonical functions of EEF1A1 are involved in cellular responses to metabolic stress is unclear. The goal of this program is to elucidate the links between protein synthesis, regulation of the actin cytoskeleton, and cellular stress responses induced by lipid overload. Lipotoxicity is the process whereby ectopic lipid deposition in non-adipose cells leads to cellular dysfunction, cell death, and eventual tissue dysfunction. Since many lipid metabolic processes occur at the ER, lipotoxic conditions in secretory cell types are accompanied by rapid induction of ER stress and the unfolded protein response (UPR). The UPR restores homeostasis by halting protein synthesis, while promoting protein folding and degradation. However, severe or prolonged stress initiates an ER stress response (ERSR) which can lead to cell death. The ERSR involves re-initiation of protein synthesis to generate pro-inflammatory and pro-apoptotic factors a deleterious anabolic response. EEF1A1 is induced in upon ER stress, and is known to be a key mediator of lipotoxic cell death. We recently found that blocking the protein synthetic activity of EEF1A1 with a specific inhibitor, didemnin B, decreased lipotoxic cell death in hepatocytes. Moreover, acute intervention with didemnin B improved hepatic ER stress and associated inflammation in mice with severe fatty liver. But the precise mechanisms through which EEF1A1 participates in cellular stress responses and promotes hepatocyte lipotoxicity are unclear. It is also not known whether EEF1A1 participates in lipotoxicity in other ER-rich cell types, particularly pancreatic beta-cells. Thus the short term objectives of this program are to determine the comparative functions of EEF1A1 in cellular responses to excess lipid accumulation (1) in cultured hepatocytes and pancreatic beta-cells, and (2) in liver and pancreas of mice with diet-induced tissue lipid accumulation. The long term program goal is to understand the global mechanism(s) of action of EEF1A1 in cellular stress responses to excess lipid in metabolic tissues throughout the body, including liver, pancreas, myocardium, and skeletal muscle, in part by using a unique transgenic Eef1a1-EGFP mouse model to test whole body Eef1a1 expression patterns in response to metabolic stress induced by high fat diet. Overall, this program will determine how the canonical and non-canonical functions of EEF1A1 are involved in ER stress response and cell death processes induced by excessive cellular lipid accumulation, thereby furthering our understanding of lipotoxicity and the diverse functions of EEF1A1.