Zinc Dyshomeostasis Is Linked with the Loss of Mucolipidosis IV-associated TRPML1 Ion Channel
Zinc Dyshomeostasis Is Linked with the Loss of Mucolipidosis IV-associated TRPML1 Ion Channel
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DOI：
10.1074/jbc.c110.165480
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发表时间：
2010-11-05
影响因子：
4.8
通讯作者：
Cuajungco, Math P.
中科院分区：
文献类型：
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作者：
Eichelsdoerfer, Jonathan L.;Evans, Jeffrey A.;Cuajungco, Math P.
可螯合锌在脑功能中是重要的，并且维持其体内平衡以防止细胞毒性过载。然而，某些病理事件导致溶酶体和线粒体中的细胞内锌积累。异常的溶酶体和线粒体是称为粘脂沉积症IV（MLIV）的人类溶酶体贮积症的常见特征。MLIV是由TRPML 1离子通道功能丧失引起的。MLIV细胞出现大的超酸性溶酶体、膜空泡、线粒体碎片和自噬功能障碍。在这里，我们观察到，RNA干扰的mucolipin-1基因（TRPML 1）在HEK-293细胞模仿MLIV细胞表型组成的大溶酶体和膜空泡，积累螯合锌。为了显示异常的可螯合锌水平确实与MLIV病理学相关，我们使用N-（6-甲氧基-8-喹啉基）-对甲苯磺酰胺荧光染料用分光荧光计定量其在培养的MLIV患者成纤维细胞和对照细胞中的浓度。我们发现MLIV细胞中可螯合锌水平显著增加，但对照细胞中没有。此外，我们使用电感耦合等离子体质谱法定量了TRPML 1（-/-）敲除小鼠和野生型同窝小鼠全脑组织中的各种金属同位素，并观察到与对照组相比，TRPML 1（-/-）小鼠脑中的锌-66同位素显著升高。总之，我们首次表明TRPML 1功能的丧失导致细胞内可螯合锌稳态异常。我们认为，螯合锌积累在大的溶酶体和膜空泡可能有助于疾病的发病机制和MLIV患者进行性细胞变性。
Chelatable zinc is important in brain function, and its homeostasis is maintained to prevent cytotoxic overload. However, certain pathologic events result in intracellular zinc accumulation in lysosomes and mitochondria. Abnormal lysosomes and mitochondria are common features of the human lysosomal storage disorder known as mucolipidosis IV (MLIV). MLIV is caused by the loss of TRPML1 ion channel function. MLIV cells develop large hyperacidic lysosomes, membranous vacuoles, mitochondrial fragmentation, and autophagic dysfunction. Here, we observed that RNA interference of mucolipin-1 gene (TRPML1) in HEK-293 cells mimics the MLIV cell phenotype consisting of large lysosomes and membranous vacuoles that accumulate chelatable zinc. To show that abnormal chelatable zinc levels are indeed correlated with MLIV pathology, we quantified its concentration in cultured MLIV patient fibroblast and control cells with a spectrofluorometer using N-(6-methoxy-8-quinolyl)-p-toluene sulfonamide fluorochrome. We found a significant increase of chelatable zinc levels in MLIV cells but not in control cells. Furthermore, we quantified various metal isotopes in whole brain tissue of TRPML1(-/-) null mice and wild-type littermates using inductively coupled plasma mass spectrometry and observed that the zinc-66 isotope is markedly elevated in the brain of TRPML1(-/-) mice when compared with controls. In conclusion, we show for the first time that the loss of TRPML1 function results in intracellular chelatable zinc dyshomeostasis. We propose that chelatable zinc accumulation in large lysosomes and membranous vacuoles may contribute to the pathogenesis of the disease and progressive cell degeneration in MLIV patients.