The Chemical Chaperone Phenylbutyrate Rescues MCT8 Mutations Associated With Milder Phenotypes in Patients With Allan-Herndon-Dudley Syndrome
The Chemical Chaperone Phenylbutyrate Rescues MCT8 Mutations Associated With Milder Phenotypes in Patients With Allan-Herndon-Dudley Syndrome
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DOI：
10.1210/en.2016-1530
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发表时间：
2017-03-01
期刊：
影响因子：
4.8
通讯作者：
Schweizer, Ulrich
中科院分区：
文献类型：
--
作者：
Braun, Doreen;Schweizer, Ulrich
甲状腺激素转运蛋白单羧酸转运蛋白8（MCT 8）的突变阻止甲状腺激素在发育过程中适当进入脑细胞，并导致受影响患者的严重精神发育迟滞。目前的治疗选择是拟甲状腺化合物，其独立于MCT 8进入大脑。一些MCT 8缺陷患者（例如，携带MCT 8（delF 501）的人）不会像大多数其他人那样受到严重影响。我们已经表明，MCT 8（delF 501）蛋白具有降低的蛋白质稳定性，但是一旦其到达质膜，具有重要的残余功能。我们能够在Madin-Darby犬肾细胞模型中通过应用化学伴侣苯丁酸钠（NaPB）（一种已用于治疗囊性纤维化和尿素循环缺陷患者较长时间的药物）挽救MCT 8delF 501的蛋白表达和功能。在本研究中，我们扩展了我们以前的研究，并报告了一系列与较温和的患者表型相关的其他致病性MCT 8突变体的NaPB依赖性拯救。我们发现，NaPB可以在功能上拯救MCT 8中的Ser 194 Phe，Ser 290 Phe，Leu 434 Trp，Arg 445 Cys，Leu 492 Pro和Leu 568 Pro突变的表达和活性，并呈剂量依赖性。大豆异黄酮，一种膳食补充剂，这是有效的MCT 8（delF 501），也有效地增加这些MCT 8突变体的表达和运输，但是，突变体之间的效果大小不同。动力学分析表明，突变体对主要底物3，3 '，5-三碘甲腺原氨酸的米氏常数与野生型值没有太大差异，表明这些突变体与底物的相互作用没有受损，而是由于突变而不稳定并降解。
Mutations in the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) prevent appropriate entry of thyroid hormones into brain cells during development and cause severe mental retardation in affected patients. The current treatment options are thyromimetic compounds that enter the brain independently of MCT8. Some MCT8-deficient patients (e.g., those carrying MCT8(delF501)) will not be as severely affected as most others. We have shown that the MCT8(delF501) protein has decreased protein stability but important residual function once it reaches the plasma membrane. We were able to rescue protein expression and the function of MCT8delF501 in a Madin-Darby canine kidney cell model by application of the chemical chaperone sodium phenylbutyrate (NaPB), a drug that has been used to treat patients with cystic fibrosis and urea cycle defects for extended periods of time. In the present study, we have extended our previous study and report on the NaPB-dependent rescue of a series of other pathogenic MCT8 mutants associated with milder patient phenotypes. We show that NaPB can functionally rescue the expression and activities of Ser194Phe, Ser290Phe, Leu434Trp, Arg445Cys, Leu492Pro, and Leu568Pro mutations in MCT8 in a dose-dependent manner. The soy isoflavone genistein, a dietary supplement, which was effective in MCT8(delF501), was also effective in increasing the expression and transport of these MCT8 mutants; however, the effect size differed among mutants. Kinetic analyses revealed that the Michaelis constants of the mutants toward the primary substrate 3,3',5-triiodothyronine were not much different from the wild-type value, suggesting that these mutants are not impaired in their interaction with substrate but rather destabilized by the mutation and degraded.