Glycometabolic Biochemistry Laboratory, Cluster for Pioneering Research, RIKEN, Saitama 351-0198, Japan; Division of Glycobiologics, Intractable Disease Research Center, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan.
Glycometabolic Biochemistry Laboratory, Cluster for Pioneering Research, RIKEN, Saitama 351-0198, Japan.
Biochim Biophys Acta Mol Basis Dis. 2020 Mar 1;1866(3):165588. doi: 10.1016/j.bbadis.2019.165588. Epub 2019 Nov 13.
The cytoplasmic peptide:N-glycanase (Ngly1) is a de-N-glycosylating enzyme that cleaves N-glycans from misfolded glycoproteins and is involved in endoplasmic reticulum-associated degradation. The recent discovery of NGLY1-deficiency, which causes severe systemic symptoms, drew attention to the physiological function of Ngly1 in mammals. While several studies have been carried out to reveal the physiological necessity of Ngly1, the semi-lethal nature of Ngly1-deficient animals made it difficult to analyze its function in adults. In this study, we focus on the physiological function of Ngly1 in liver (hepatocyte)-specific Ngly1-deficient mice generated using the cre-loxP system. We found that hepatocyte-specific Ngly1-deficient mice showed abnormal hepatocyte nuclear size/morphology with aging but did not show other notable defects in unstressed conditions. This nuclear phenotype did not appear to be related to the function of the only gene currently reported to rescue Ngly1-deficient murine lethality so far, endo-β-N-acetylglucosaminidase. We also found that under a high fructose diet induced stress, the hepatocyte-specific Ngly1-deletion resulted in liver transaminases elevation and increased lipid droplet accumulation. We showed that the processing and localization of the transcription factor, nuclear factor erythroid 2-like 1 (Nfe2l1), was impaired in the Ngly1-deficient hepatocytes. Therefore, Nfe2l1, at least partially, contributes to the phenotypes observed in hepatocyte-specific Ngly1-deficient mice. Our results indicate that Ngly1 plays important roles in the adult liver impacting nuclear morphology and lipid metabolism. Hepatocyte-specific Ngly1-deficient mice could thus serve as a valuable animal model for assessing in vivo efficacy of drugs and/or treatment for NGLY1-deficiency.
N-糖基化酶（Ngly1）是一种去糖基化酶，可从错误折叠的糖蛋白中切割 N-聚糖，并参与内质网相关降解。最近发现的 NGLY1 缺乏症会导致严重的全身症状，这引起了人们对 Ngly1 在哺乳动物中生理功能的关注。虽然已经进行了几项研究来揭示 Ngly1 的生理必要性，但 Ngly1 缺陷型动物的半致死性质使得难以在成年动物中分析其功能。在这项研究中，我们专注于使用 cre-loxP 系统生成的肝细胞特异性 Ngly1 缺陷型小鼠中 Ngly1 的生理功能。我们发现，肝细胞特异性 Ngly1 缺陷型小鼠随着年龄的增长表现出异常的肝细胞核大小/形态，但在未受应激的情况下没有表现出其他明显缺陷。这种核表型似乎与迄今为止唯一被报道能挽救 Ngly1 缺陷型小鼠致死性的基因的功能无关，即内-β-N-乙酰氨基葡萄糖苷酶。我们还发现，在高果糖饮食诱导的应激下，肝细胞特异性 Ngly1 缺失导致肝转氨酶升高和脂质滴积累增加。我们表明，转录因子核因子红细胞 2 样 1（Nfe2l1）的加工和定位在 Ngly1 缺陷型肝细胞中受损。因此，Nfe2l1 至少部分地导致了肝细胞特异性 Ngly1 缺陷型小鼠中观察到的表型。我们的结果表明，Ngly1 在成年肝脏中发挥重要作用，影响核形态和脂质代谢。因此，肝细胞特异性 Ngly1 缺陷型小鼠可以作为评估体内药物疗效和/或治疗 NGLY1 缺乏症的有价值的动物模型。
