Biomembrane Lab, Department of Biochemistry, School of Life Sciences, Bharathidasan University, Tiruchirappalli, 620 024, Tamilnadu, India.
Department of Lipid Science, CSIR-Central Food Technological Research Institute (CSIR-CFTRI), Mysore, 570020, India.
Sci Rep. 2019 Oct 9;9(1):14485. doi: 10.1038/s41598-019-51054-7.
The endoplasmic reticulum (ER) is a multi functional organelle and plays a crucial role in protein folding and lipid biosynthesis. The SEC59 gene encodes dolichol kinase, required for protein glycosylation in the ER. The mutation of sec59-1 caused a protein N-glycosylation defect mediated ER stress resulting in increased levels of phospholipid, neutral lipid and sterol, whereas growth was reduced. In the sec59-1∆ cell, the N-glycosylation of vacuolar carboxy peptidase-Y (CPY) was significantly reduced; whereas the ER stress marker Kar2p and unfolded protein response (UPR) were significantly increased. Increased levels of Triacylglycerol (TAG), sterol ester (SE), and lipid droplets (LD) could be attributed to up-regulation of DPP1, LRO1, and ARE2 in the sec 59-1∆ cell. Also, the diacylglycerol (DAG), sterol (STE), and free fatty acids (FFA) levels were significantly increased, whereas the genes involved in peroxisome biogenesis and Pex3-EGFP levels were reduced when compared to the wild-type. The microarray data also revealed increased expression of genes involved in phospholipid, TAG, fatty acid, sterol synthesis, and phospholipid transport resulting in dysregulation of lipid homeostasis in the sec59-1∆ cell. We conclude that SEC59 dependent N-glycosylation is required for lipid homeostasis, peroxisome biogenesis, and ER protein quality control.
内质网（ER）是一种多功能细胞器，在蛋白质折叠和脂质生物合成中起着关键作用。SEC59 基因编码的是多萜醇激酶，该酶是内质网中蛋白质糖基化所必需的。sec59-1 的突变导致蛋白 N-糖基化缺陷，引发内质网应激，导致磷脂、中性脂质和固醇水平升高，而生长受到抑制。在 sec59-1∆细胞中，液泡羧肽酶-Y（CPY）的 N-糖基化显著减少；而 ER 应激标志物 Kar2p 和未折叠蛋白反应（UPR）显著增加。三酰基甘油（TAG）、固醇酯（SE）和脂滴（LD）水平的增加可归因于 sec59-1∆细胞中 DPP1、LRO1 和 ARE2 的上调。此外，与野生型相比，二酰基甘油（DAG）、固醇（STE）和游离脂肪酸（FFA）水平显著升高，而参与过氧化物酶体生物发生的基因和 Pex3-EGFP 水平降低。微阵列数据还显示，与磷脂、TAG、脂肪酸、固醇合成和磷脂转运相关的基因表达增加，导致 sec59-1∆细胞中脂质稳态失调。我们得出结论，SEC59 依赖性 N-糖基化是脂质稳态、过氧化物酶体生物发生和 ER 蛋白质量控制所必需的。
