GM1-gangliosidosis, a lysosomal storage disorder, is associated with ~ 161 missense variants in the GLB1 gene. Affected patients present with β-galactosidase (β-Gal) deficiency in lysosomes. Loss of function in ER-retained misfolded enzymes with missense variants is often due to subcellular mislocalization. Deoxygalactonojirimycin (DGJ) and its derivatives are pharmaceutical chaperones that directly bind to mutated β-Gal in the ER promoting its folding and trafficking to lysosomes and thus enhancing its activity. An Emirati child has been diagnosed with infantile GM1-gangliosidosis carrying the reported p.D151Y variant. We show that p.D151Y β-Gal in patient's fibroblasts retained < 1% residual activity due to impaired processing and trafficking. The amino acid substitution significantly affected the enzyme conformation; however, p.D151Y β-Gal was amenable for partial rescue in the presence of glycerol or at reduced temperature where activity was enhanced with ~ 2.3 and 7 folds, respectively. The butyl (NB-DGJ) and nonyl (NN-DGJ) derivatives of DGJ chaperoning function were evaluated by measuring their IC50s and ability to stabilize the wild-type β-Gal against thermal degradation. Although NN-DGJ showed higher affinity to β-Gal, it did not show a significant enhancement in p.D151Y β-Gal activity. However, NB-DGJ promoted p.D151Y β-Gal maturation and enhanced its activity up to ~ 4.5% of control activity within 24 h which was significantly increased to ~ 10% within 6 days. NB-DGJ enhancement effect was sustained over 3 days after washing it out from culture media. We therefore conclude that NB-DGJ might be a promising therapeutic chemical chaperone in infantile GM1 amenable variants and therefore warrants further analysis for its clinical applications.

中文翻译：

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药理伴侣蛋白Nn-丁基-脱氧半乳糖苷嘧啶能增强婴儿GM1神经节病患者成纤维细胞中β-半乳糖苷酶的加工和活性。

GM1神经节苷脂病是一种溶酶体贮积病，与GLB1基因的〜161个错义变体有关。受影响的患者存在溶酶体中的β-半乳糖苷酶（β-Gal）缺乏症。具有错义变体的ER保留错折叠酶的功能丧失通常是由于亚细胞错位引起的。脱氧半乳糖苷霉素（DGJ）及其衍生物是药物分子伴侣，可直接与ER中的突变β-Gal结合，从而促进其折叠和运输至溶酶体，从而增强其活性。阿联酋的一名儿童被诊断患有携带报告的p.D151Y变异的婴儿GM1神经节病。我们显示患者成纤维细胞中的p.D151Yβ-Gal由于加工和运输受损而保留了<1％的残留活性。氨基酸取代显着影响酶构象。但是，第 D151Yβ-Gal适用于在甘油存在下或在降低的温度（活性分别提高约2.3倍和7倍）的情况下进行部分拯救。通过测量它们的IC50和稳定野生型β-Gal抵抗热降解的能力，评估了DGJ伴侣功能的丁基（NB-DGJ）和壬基（NN-DGJ）衍生物。尽管NN-DGJ对β-Gal具有更高的亲和力，但在p.D151Yβ-Gal活性方面并未表现出明显的增强。但是，NB-DGJ促进p.D151Yβ-Gal成熟，并在24小时内将其活性提高至对照活性的〜4.5％，而在6天内显着增加至〜10％。从培养基中洗去后，NB-DGJ的增强作用持续了3天。