Department of Rheumatology and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250021, Shandong, China.
Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Cheeloo College of Medicine, Qilu Hospital, Shandong University, West Wenhua Street No.107, Jinan, 250012, Shandong, China.
J Transl Med. 2024 May 13;22(1):449. doi: 10.1186/s12967-024-05275-8.
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.
胸腺嘧啶磷酸化酶（TYMP）遗传性缺陷导致一种罕见疾病，其特征是存在多种线粒体 DNA（mtDNA）异常，即线粒体神经胃肠脑肌病（MNGIE）。然而，TP 缺乏对溶酶体的影响仍不清楚，而溶酶体对于线粒体质量控制和核酸代谢非常重要。收集 MNGIE 患者、m.3243A>G 线粒体脑肌病、乳酸酸中毒和卒中样发作（MELAS）患者和健康对照（HC）的肌肉活检组织和皮肤成纤维细胞，进行线粒体和溶酶体功能分析。与对照组相比，MNGIE 患者的肌肉组织除了 mtDNA 异常外，还明显检测到 LAMP1 表达降低和线粒体含量增加。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、酶活性降低和蛋白降解能力受损。TYMP 敲除或 TP 抑制在细胞中也可诱导类似的溶酶体功能障碍。通过溶酶体免疫沉淀（Lyso-IP），在 TP 缺乏的溶酶体中检测到增加的线粒体蛋白、减少的囊泡蛋白和 V-ATPase 酶，以及各种核苷的积累。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，这些结果提供了证据表明，TP 缺乏导致核苷在溶酶体中的积累和溶酶体功能障碍，揭示了 MNGIE 潜在的广泛的细胞器破坏。
