PDF(Pubmed)
Abstract：
Inherited deficiency of thymidine phosphorylase (TP), encoded by TYMP, leads to a rare disease with multiple mitochondrial DNA (mtDNA) abnormalities, mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). However, the impact of TP deficiency on lysosomes remains unclear, which are important for mitochondrial quality control and nucleic acid metabolism. Muscle biopsy tissue and skin fibroblasts from MNGIE patients, patients with m.3243 A > G mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and healthy controls (HC) were collected to perform mitochondrial and lysosomal functional analyses. In addition to mtDNA abnormalities, compared to controls distinctively reduced expression of LAMP1 and increased mitochondrial content were detected in the muscle tissue of MNGIE patients. Skin fibroblasts from MNGIE patients showed decreased expression of LAMP2, lowered lysosomal acidity, reduced enzyme activity and impaired protein degradation ability. TYMP knockout or TP inhibition in cells can also induce the similar lysosomal dysfunction. Using lysosome immunoprecipitation (Lyso- IP), increased mitochondrial proteins, decreased vesicular proteins and V-ATPase enzymes, and accumulation of various nucleosides were detected in lysosomes with TP deficiency. Treatment of cells with high concentrations of dThd and dUrd also triggers lysosomal dysfunction and disruption of mitochondrial homeostasis. Therefore, the results provided evidence that TP deficiency leads to nucleoside accumulation in lysosomes and lysosomal dysfunction, revealing the widespread disruption of organelles underlying MNGIE.
摘要：
遗传性胸苷磷酸化酶（TP）缺乏症，由TYMP编码，导致多种线粒体DNA（mtDNA）异常的罕见疾病，线粒体神经胃肠脑肌病（MNGIE）。然而,TP缺乏对溶酶体的影响尚不清楚，这对线粒体质量控制和核酸代谢很重要。MNGIE患者的肌肉活检组织和皮肤成纤维细胞，m.3243A>G线粒体脑病患者，收集乳酸性酸中毒和卒中样发作(MELAS)和健康对照(HC)进行线粒体和溶酶体功能分析.除了mtDNA异常,与对照组相比，MNGIE患者肌肉组织中LAMP1的表达明显减少，线粒体含量增加。MNGIE患者的皮肤成纤维细胞显示LAMP2表达降低，溶酶体酸度降低，酶活性降低，蛋白质降解能力受损。细胞中的TYMP敲除或TP抑制也可以诱导类似的溶酶体功能障碍。使用溶酶体免疫沉淀（溶酶体-IP），增加线粒体蛋白，减少的囊泡蛋白和V-ATP酶，在TP缺乏的溶酶体中检测到各种核苷的积累。用高浓度的dThd和dUrd处理细胞也会引发溶酶体功能障碍和线粒体稳态的破坏。因此,结果提供了证据，表明TP缺乏导致核苷在溶酶体中积累和溶酶体功能障碍，揭示了MNGIE背后细胞器的广泛破坏。
