Tu'ifua Travis K, Chow Clement Y
Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, United States of America.
PLoS Genet. 2025 Aug 7;21(8):e1011823. doi: 10.1371/journal.pgen.1011823. eCollection 2025 Aug.
N-glycanase 1 (NGLY1) deficiency is an ultra-rare disease caused by autosomal recessive loss-of-function mutations in the NGLY1 gene. NGLY1 removes N-linked glycans from glycoproteins in the cytoplasm and is thought to help clear misfolded proteins from the endoplasmic reticulum (ER) through the ER associated degradation (ERAD) pathway. Despite this, the physiological significance of NGLY1 in ERAD is not understood. The best characterized substrate of NGLY1 is NRF1, a transcription factor that upregulates proteasome expression and the proteasome bounce-back response. We previously performed a genetic modifier screen using a Drosophila model of NGLY1 deficiency and identified potential modifiers that alter the lethality of the model. We identified two protein-coding variants in Hrd3/SEL1L: S780P and Δ806-809. Both variants are localized to the SEL1L cytoplasmic tail, an uncharacterized domain. SEL1L is a component of the ERAD complex that retrotranslocates misfolded proteins from the ER to the cytoplasm for degradation. We used CRISPR to generate fly lines carrying these SEL1L variants in a common genetic background and tested them with our model of NGLY1 deficiency. Validating our previous screen, the SEL1LS780P and SEL1LΔ806-809 variants increased the survival of the NGLY1 deficiency model, compared to the SEL1LS780 variant. To determine how these SEL1L variants were modifying lethality in NGLY1 deficiency, we interrogated the ERAD and NRF1 signaling pathways. We found that the SEL1LS780P and SEL1LΔ806-809 variants improve resistance to ER stress, with enhanced ERAD function as a likely contributing mechanism. This effect depends on NGLY1 activity, further implicating NGLY1 in general ERAD function. We also found that, in heterozygous NGLY1 null flies, these variants protect against some defects like increased lethality caused by proteasome inhibition. These results provide new insights into the role of SEL1L in the disease pathogenesis of NGLY1 deficiency. SEL1L is a strong candidate modifier gene in patients, where variability in presentation is common.
N-聚糖酶1（NGLY1）缺乏症是一种由NGLY1基因的常染色体隐性功能丧失突变引起的超罕见疾病。NGLY1可从细胞质中的糖蛋白上移除N-连接聚糖，并且被认为有助于通过内质网相关降解（ERAD）途径清除内质网（ER）中错误折叠的蛋白质。尽管如此，NGLY1在ERAD中的生理意义仍不明确。NGLY1最具特征的底物是NRF1，一种上调蛋白酶体表达和蛋白酶体反弹反应的转录因子。我们之前使用NGLY1缺乏症的果蝇模型进行了遗传修饰筛选，并鉴定出了改变该模型致死率的潜在修饰因子。我们在Hrd3/SEL1L中鉴定出两个蛋白质编码变体：S780P和Δ806 - 809。这两个变体都定位于SEL1L细胞质尾部，这是一个未被表征的结构域。SEL1L是ERAD复合物的一个组成部分，它将错误折叠的蛋白质从内质网逆向转运到细胞质中进行降解。我们使用CRISPR技术在一个常见的遗传背景下生成携带这些SEL1L变体的果蝇品系，并将它们与我们的NGLY1缺乏症模型进行测试。与SEL1LS780变体相比，SEL1LS780P和SEL1LΔ806 - 809变体提高了NGLY1缺乏症模型的存活率，从而验证了我们之前的筛选结果。为了确定这些SEL1L变体如何改变NGLY1缺乏症中的致死率，我们研究了ERAD和NRF1信号通路。我们发现SEL1LS780P和SEL1LΔ806 - 809变体提高了对内质网应激的抗性，增强的ERAD功能可能是一个促成机制。这种效应取决于NGLY1的活性，进一步表明NGLY1在一般ERAD功能中的作用。我们还发现，在杂合NGLY1无效果蝇中，这些变体可防止一些缺陷，如蛋白酶体抑制导致的致死率增加。这些结果为SEL1L在NGLY1缺乏症疾病发病机制中的作用提供了新的见解。在临床表现存在差异很常见的患者中，SEL1L是一个强有力的候选修饰基因。
