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Abstract：
Cystinosis is a rare, autosomal recessive, lysosomal storage disease caused by mutations in the gene CTNS, leading to cystine accumulation in the lysosomes. While cysteamine lowers the cystine levels, it does not cure the disease, suggesting that CTNS exerts additional functions besides cystine transport. This study investigated the impact of infantile and juvenile CTNS mutations with discrepant genotype/phenotype correlations on CTNS expression, and subcellular localisation and function in clinically relevant cystinosis cell models to better understand the link between genotype and CTNS function. Using CTNS-depleted proximal tubule epithelial cells and patient-derived fibroblasts, we expressed a selection of CTNSmutants under various promoters. EF1a-driven expression led to substantial overexpression, resulting in CTNS protein levels that localised to the lysosomal compartment. All CTNSmutants tested also reversed cystine accumulation, indicating that CTNSmutants still exert transport activity, possibly due to the overexpression conditions. Surprisingly, even CTNSmutants expression driven by the less potent CTNS and EFS promoters reversed the cystine accumulation, contrary to the CTNSG339R missense mutant. Taken together, our findings shed new light on CTNS mutations, highlighting the need for robust assessment methodologies in clinically relevant cellular models and thus paving the way for better stratification of cystinosis patients, and advocating for the development of more personalized therapy.
摘要：
胱抑素是一种罕见的，常染色体隐性遗传,由CTNS基因突变引起的溶酶体贮积病，导致胱氨酸在溶酶体中积累。半胱胺降低胱氨酸水平，它不能治愈疾病，表明CTNS发挥除胱氨酸转运外的其他功能。本研究调查了不同基因型/表型相关性的婴儿和青少年CTNS突变对CTNS表达的影响，在临床相关的胱氨酸病细胞模型中的亚细胞定位和功能，以更好地了解基因型和CTNS功能之间的联系。使用CTNS耗尽的近端小管上皮细胞和患者来源的成纤维细胞，我们在各种启动子下表达了CTNS突变体的选择。EF1a驱动的表达导致大量过度表达，导致定位于溶酶体区室的CTNS蛋白水平。所有测试的CTNS突变体也逆转了胱氨酸的积累，表明CTNS突变体仍然发挥运输活性，可能是由于过表达条件。令人惊讶的是,甚至由效力较低的CTNS和EFS启动子驱动的CTNS突变体表达也逆转了胱氨酸的积累，与CTNSG339R错义突变体相反。一起来看,我们的发现为CTNS突变提供了新的线索，强调在临床相关的细胞模型中需要稳健的评估方法，从而为更好地对膀胱炎患者进行分层铺平了道路，并倡导开发更个性化的治疗方法。
