Section on Developmental Genetics, Program on Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892–1830, USA.
Mol Genet Metab. 2011 Nov;104(3):338-45. doi: 10.1016/j.ymgme.2011.05.021. Epub 2011 Jun 13.
Infantile neuronal ceroid lipofuscinosis (INCL), a lethal hereditary neurodegenerative lysosomal storage disorder, affects mostly children. It is caused by inactivating mutations in the palmitoyl-protein thioesterase-1(PPT1) gene. Nonsense mutations in a gene generate premature termination codons producing truncated,nonfunctional or deleterious proteins. PPT1 nonsense-mutations account for approximately 31% of INCL patients in the US. Currently, there is no effective treatment for this disease. While aminoglycosides such asgentamycin suppress nonsense mutations, inherent toxicity of aminoglycosides prohibits chronic use inpatients. PTC124 is a non-toxic compound that induces ribosomal read-through of premature termination codons. We sought to determine whether PTC124-treatment of cultured cells from INCL patients carrying nonsense mutations in the PPT1 gene would correct PPT1 enzyme-deficiency with beneficial effects. Our results showed that PTC124-treatment of cultured cells from INCL patients carrying PPT1 nonsense-mutations induced PPT1 enzymatic activity in a dose- and time-dependent manner. This low level of PPT1 enzyme activity induced by PTC124 is virtually identical to that induced by gentamycin-treatment. Even though only a modest increase in PPT1 activity was achieved by PTC124-treatment of INCL cells, this treatment reduced the levels of thioester (constituent of ceroid) load. Our results suggest that PTC124-treatment induces PPT1 enzymatic activity in cultured cells from INCL patients carrying PPT1 nonsense-mutations, and this modest enzymatic activity has demonstrable beneficial effects on these cells. The clinical relevance of these effects may be tested in animal models of INCL carrying nonsense mutations in the PPT1 gene.
婴儿神经元蜡样脂褐质沉积症（INCL）是一种致命的遗传性神经退行性溶酶体贮积病，主要影响儿童。它是由棕榈酰蛋白硫酯酶-1（PPT1）基因失活突变引起的。基因中的无义突变会产生过早终止密码子，从而产生截短的、无功能或有害的蛋白质。PPT1 无义突变约占美国 INCL 患者的 31%。目前，这种疾病没有有效的治疗方法。虽然氨基糖苷类药物如庆大霉素能抑制无义突变，但氨基糖苷类药物的固有毒性禁止在患者中长期使用。PTC124 是一种无毒化合物，可诱导核糖体通读过早终止密码子。我们试图确定 PTC124 是否能纠正 INCL 患者培养细胞中 PPT1 基因的无义突变导致的 PPT1 酶缺乏症，并带来有益的影响。我们的结果表明，PTC124 以剂量和时间依赖的方式处理 INCL 患者携带 PPT1 无义突变的培养细胞，诱导 PPT1 酶活性。PTC124 诱导的 PPT1 酶活性水平很低，与庆大霉素处理诱导的水平几乎相同。尽管 PTC124 处理 INCL 细胞仅能适度增加 PPT1 活性，但这种治疗可降低硫酯（蜡样质的组成部分）负荷水平。我们的结果表明，PTC124 处理可诱导 INCL 患者携带 PPT1 无义突变的培养细胞中的 PPT1 酶活性，这种适度的酶活性对这些细胞具有明显的有益影响。这些影响的临床相关性可能在携带 PPT1 基因无义突变的 INCL 动物模型中进行测试。
