在内分泌网膜应激过程中实时的氧化还原测量显示了相互关联的蛋白质折叠功能
Philip I Merksamer1, Ala Trusina, Feroz R Papa
1Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
Cell
|November 26, 2008
概括
研究人员开发了新的方法来测量内质网膜 (ER) 氧化还原状态,揭示了氧化还原变化伴随着ER压力和蛋白质折叠中断. 这项工作揭示了关于细胞对压力的反应的新见解.
科学领域:
- 细胞生物学 细胞生物学
- 生物化学 生物化学
- 分子生物学分子生物学
背景情况:
- 细胞内膜网膜 (ER) 应激发生在未折叠的蛋白质积累时.
- 展开的蛋白质反应 (UPR) 被激活以减少展开的蛋白质.
- 在体内直接测量未折叠的蛋白质是具有挑战性的,这导致了通用的"ER压力"定义.
研究的目的:
- 调查可测量的氧化还原变化是否伴随着ER中未折叠的蛋白质积累.
- 开发用于单细胞中动态测量ER氧化还原状态和UPR活性的工具.
- 了解ER氧化还原潜力,蛋白质折叠和UPR激活之间的关系.
主要方法:
- 使用光蛋白报告器实时监测ER氧化还原状态.
- 测量了单个细胞中的UPR活性,同时与氧化还原状态.
- 采用基因分析来研究细胞对各种压力因素的反应.
- 在同源细胞群体内研究了氧化还原异质性.
主要成果:
- 一些不同的实验和生理压力因素会在UPR的恒常性控制丧失时损害ER蛋白的氧化.
- 证实了氧化还原变化与ER蛋白折叠的破坏有关.
- 发现了ER蛋白折叠,修饰和质量控制系统之间的功能性相互联系.
- 在同源细胞群中确定了氧化还原异质性.
结论:
- ER氧化还原状态作为未折叠蛋白质积累的可测量指标.
- 该研究提供了一种新的方法来评估ER压力,超出了通用的UPR激活.
- 这些发现突显了ER中氧化还原平衡和蛋白质平衡之间的复杂联系.
相关概念视频
Protein Modifications in the RER
Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Regulation of the Unfolded Protein Response
Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
The Unfolded Protein Response
The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
Protein Folding Quality Check in the RER
ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
Export of Misfolded Proteins out of the ER
After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
Protein Dynamics in Living Cells
Different fluorescence-based techniques are used to study the protein dynamics in living cells. These techniques include FRAP, FRET, and PET.
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...


