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Classification of the Molecular Defects Associated with Pathogenic Variants of the SLC6A8 Creatine Transporter
Biochemistry ( IF 2.9 ) Pub Date : 2020-03-30 , DOI: 10.1021/acs.biochem.9b00956
Martin D. Salazar 1 , Nathan B. Zelt 1 , Robert Saldivar 1 , Charles P. Kuntz 1 , Sheng Chen 1 , Wesley D. Penn 1 , Richard Bonneau 2, 3, 4, 5 , Julia Koehler Leman 2 , Jonathan P. Schlebach 1
Affiliation  

More than 80 loss-of-function (LOF) mutations in the SLC6A8 creatine transporter (hCRT1) are responsible for cerebral creatine deficiency syndrome (CCDS), which gives rise to a spectrum of neurological defects, including intellectual disability, epilepsy, and autism spectrum disorder. To gain insight into the nature of the molecular defects caused by these mutations, we quantitatively profiled the cellular processing, trafficking, expression, and function of eight pathogenic CCDS variants in relation to the wild type (WT) and one neutral isoform. All eight CCDS variants exhibit measurable proteostatic deficiencies that likely contribute to the observed LOF. However, the magnitudes of their specific effects on the expression and trafficking of hCRT1 vary considerably, and we find that the LOF associated with two of these variants primarily arises from the disruption of the substrate-binding pocket. In conjunction with an analysis of structural models of the transporter, we use these data to suggest mechanistic classifications for these variants. To evaluate potential avenues for therapeutic intervention, we assessed the sensitivity of these variants to temperature and measured their response to the proteostasis regulator 4-phenylbutyrate (4-PBA). Only one of the tested variants (G132V) is sensitive to temperature, though its response to 4-PBA is negligible. Nevertheless, 4-PBA significantly enhances the activity of WT hCRT1 in HEK293T cells, which suggests it may be worth evaluating as a therapeutic for female intellectual disability patients carrying a single CCDS mutation. Together, these findings reveal that pathogenic SLC6A8 mutations cause a spectrum of molecular defects that should be taken into consideration in future efforts to develop CCDS therapeutics.

中文翻译:

SLC6A8肌酸转运蛋白的致病变异相关的分子缺陷的分类

SLC6A8中的80多个功能丧失(LOF)突变肌酸转运蛋白(hCRT1)引起脑肌酸缺乏综合征(CCDS),引起一系列神经系统缺陷,包括智力障碍,癫痫和自闭症谱系障碍。为了深入了解由这些突变引起的分子缺陷的性质,我们定量分析了与野生型(WT)和一种中性同工型有关的8种致病CCDS变体的细胞加工,运输,表达和功能。所有八个CCDS变体均表现出可测量的蛋白稳定缺陷,可能导致观察到的LOF升高。但是,它们对hCRT1的表达和运输的特定影响的幅度差异很大,并且我们发现与这些变体中的两个相关的LOF主要来自底物结合口袋的破坏。结合转运蛋白的结构模型分析,我们使用这些数据来建议这些变体的机械分类。为了评估治疗干预的潜在途径,我们评估了这些变体对温度的敏感性,并测量了它们对蛋白稳定调节剂4-苯基丁酸酯(4-PBA)的反应。尽管只有一个测试的变体(G132V)对温度敏感,但对4-PBA的响应可以忽略不计。然而,4-PBA显着增强了HEK293T细胞中WT hCRT1的活性,这表明它值得对携带单个CCDS突变的女性智力障碍患者进行治疗。在一起,这些发现揭示出致病性 我们使用这些数据来建议这些变体的机械分类。为了评估治疗干预的潜在途径,我们评估了这些变体对温度的敏感性,并测量了它们对蛋白稳定调节剂4-苯基丁酸酯(4-PBA)的反应。尽管只有一个测试的变体(G132V)对温度敏感,但对4-PBA的响应可以忽略不计。然而,4-PBA显着增强了HEK293T细胞中WT hCRT1的活性,这表明它值得对携带单个CCDS突变的女性智力障碍患者进行治疗。在一起,这些发现揭示出致病性 我们使用这些数据来建议这些变体的机械分类。为了评估治疗干预的潜在途径,我们评估了这些变体对温度的敏感性,并测量了它们对蛋白稳定调节剂4-苯基丁酸酯(4-PBA)的反应。尽管只有一个测试的变体(G132V)对温度敏感,但对4-PBA的响应可以忽略不计。然而,4-PBA显着增强了HEK293T细胞中WT hCRT1的活性,这表明它值得对携带单个CCDS突变的女性智力障碍患者进行治疗。在一起,这些发现揭示出致病性 我们评估了这些变体对温度的敏感性,并测量了它们对蛋白稳定调节剂4-苯基丁酸酯(4-PBA)的响应。尽管只有一个测试的变体(G132V)对温度敏感,但对4-PBA的响应可以忽略不计。然而,4-PBA显着增强了HEK293T细胞中WT hCRT1的活性,这表明它值得对携带单个CCDS突变的女性智力障碍患者进行治疗。在一起,这些发现揭示出致病性 我们评估了这些变体对温度的敏感性,并测量了它们对蛋白质稳定调节剂4-苯基丁酸酯(4-PBA)的响应。尽管只有一个测试的变体(G132V)对温度敏感,但对4-PBA的响应可以忽略不计。然而,4-PBA显着增强了HEK293T细胞中WT hCRT1的活性,这表明它值得对携带单个CCDS突变的女性智力障碍患者进行治疗。在一起,这些发现揭示出致病性 这表明对于携带单一CCDS突变的女性智力残疾患者的治疗方法可能值得评估。在一起,这些发现揭示出致病性 这表明对于携带单一CCDS突变的女性智力残疾患者的治疗方法可能值得评估。在一起,这些发现揭示出致病性SLC6A8突变会引起一系列分子缺陷,在开发CCDS治疗剂的未来工作中应考虑这些缺陷。
更新日期:2020-03-30
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