Morelle Willy, Potelle Sven, Witters Peter, Wong Sunnie, Climer Leslie, Lupashin Vladimir, Matthijs Gert, Gadomski Therese, Jaeken Jaak, Cassiman David, Morava Eva, Foulquier François
Université Lille, Centre National de la Recherche Française, UMR 8576-Unité de Glycobiologie Structurale et Fonctionnelle-Unité de Glycobiologie Structurale et Fonctionnelle, F-59000 Lille, France.
Metabolic Center, Department of Pediatrics, University Hospitals Leuven, Leuven B-3000, Belgium.
J Clin Endocrinol Metab. 2017 Apr 1;102(4):1375-1386. doi: 10.1210/jc.2016-3443.
TMEM165 deficiency is a severe multisystem disease that manifests with metabolic, endocrine, and skeletal involvement. It leads to one type of congenital disorders of glycosylation (CDG), a rapidly growing group of inherited diseases in which the glycosylation process is altered. Patients have decreased galactosylation by serum glycan analysis. There are >100 CDGs, but only specific types are treatable.
Galactose has been shown to be beneficial in other CDG types with abnormal galactosylation. The aim of this study was to characterize the effects of galactose supplementation on Golgi glycosylation in TMEM165-depleted HEK293 cells, as well as in 2 patients with TMEM165-CDG and in their cultured skin fibroblast cells.
Glycosylation was assessed by mass spectrometry, western blot analysis, and transferrin isoelectrofocusing.
Both unrelated patients with TMEM165-CDG with the same deep intronic homozygous mutation (c.792+182G>A) were allocated to receive d-galactose in a daily dose of 1 g/kg.
We analyzed N-linked glycans and glycolipids in knockout TMEM165 HEK293 cells, revealing severe hypogalactosylation and GalNAc transfer defects. Although these defects were completely corrected by the addition of Mn2+, we demonstrated that the observed N-glycosylation defect could also be overcome by galactose supplementation. We then demonstrated that oral galactose supplementation in patients with TMEM165-deficient CDG improved biochemical and clinical parameters, including a substantial increase in the negatively charged transferrin isoforms, and a decrease in hypogalactosylated total N-glycan structures, endocrine function, and coagulation parameters.
To our knowledge, this is the first description of abnormal glycosylation of lipids in the TMEM165 defect and the first report of successful dietary treatment in TMEM165 deficiency. We recommend the use of oral d-galactose therapy in TMEM165-CDG.
跨膜蛋白165（TMEM165）缺陷是一种严重的多系统疾病，表现为代谢、内分泌和骨骼受累。它导致一种糖基化先天性疾病（CDG），这是一组快速增长的遗传性疾病，其中糖基化过程发生改变。通过血清聚糖分析发现患者的半乳糖基化减少。有超过100种CDG，但只有特定类型是可治疗的。
已证明半乳糖对其他半乳糖基化异常的CDG类型有益。本研究的目的是表征补充半乳糖对TMEM165缺失的HEK293细胞以及2例TMEM165 - CDG患者及其培养的皮肤成纤维细胞中高尔基体糖基化的影响。
通过质谱、蛋白质印迹分析和转铁蛋白等电聚焦评估糖基化。
两名患有相同深度内含子纯合突变（c.792 + 182G>A）的TMEM165 - CDG无关患者被分配接受每日剂量为1 g/kg的d - 半乳糖。
我们分析了敲除TMEM165的HEK293细胞中的N - 连接聚糖和糖脂，发现严重的半乳糖基化不足和N - 乙酰半乳糖胺转移缺陷。尽管通过添加Mn2 +可完全纠正这些缺陷，但我们证明补充半乳糖也可克服观察到的N - 糖基化缺陷。然后我们证明，对TMEM165缺陷型CDG患者进行口服半乳糖补充可改善生化和临床参数，包括带负电荷的转铁蛋白异构体大幅增加，以及半乳糖基化不足的总N - 聚糖结构、内分泌功能和凝血参数降低。
据我们所知，这是首次描述TMEM165缺陷中脂质糖基化异常，也是TMEM165缺陷中成功饮食治疗的首次报告。我们建议在TMEM165 - CDG中使用口服d - 半乳糖疗法。
