Misfolding, degradation, and aggregation of variant proteins - The molecular pathogenesis of short chain acyl-CoA dehydrogenase (SCAD) deficiency
Misfolding, degradation, and aggregation of variant proteins - The molecular pathogenesis of short chain acyl-CoA dehydrogenase (SCAD) deficiency
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DOI：
10.1074/jbc.m309514200
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发表时间：
2003-11-28
影响因子：
4.8
通讯作者：
Gregersen, N
中科院分区：
文献类型：
--
作者：
Pedersen, CB;Bross, P;Gregersen, N
短链酰基辅酶A脱氢酶（SCAD）缺乏症是一种由SCAD基因的罕见变异和常见易感性变异引起的线粒体脂肪酸代谢的先天性缺陷。早期的研究表明，一种常见的变体SCAD蛋白（R147W）在折叠中受损，初步实验表明，该变体蛋白与伴侣蛋白的结合时间延长，活性酶的形成延迟。因此，SCAD缺陷的分子发病机制可能依赖于线粒体内蛋白质质量控制机制，包括变异SCAD蛋白的降解和聚集。在这项研究中，我们研究了一组致病变异SCAD蛋白（R22W，G68C，W153R，R359C和Q341H）和两种常见的变异蛋白（R147W和G185S）的加工，导致SCAD活性降低。所有的SCAD蛋白，包括野生型，与线粒体HSP 60伴侣蛋白，然而，变体SCAD蛋白仍然与HSP 60的时间延长。在两个温度下的生物发生实验表明，一些变异蛋白（R22 W，G68 C，W153 R和R359 C）造成严重的错误折叠，而其他（R147 W，G185 S和Q341 H）表现出不太严重的温度敏感性折叠缺陷。基于体外缺陷的大小，这些SCAD蛋白分别被表征为折叠缺陷变体和轻度折叠变体。脉冲追踪实验表明，变体SCAD蛋白要么触发线粒体蛋白酶的蛋白水解降解，要么，特别是在升高的温度下，非天然构象异构体的聚集。后一项发现可能表明聚集的SCAD蛋白的积累可能在SCAD缺乏症的发病机制中起作用。
Short chain acyl-CoA dehydrogenase (SCAD) deficiency is an inborn error of the mitochondrial fatty acid metabolism caused by rare variations as well as common susceptibility variations in the SCAD gene. Earlier studies have shown that a common variant SCAD protein (R147W) was impaired in folding, and preliminary experiments suggested that the variant protein displayed prolonged association with chaperonins and delayed formation of active enzyme. Accordingly, the molecular pathogenesis of SCAD deficiency may rely on intramitochondrial protein quality control mechanisms, including degradation and aggregation of variant SCAD proteins. In this study we investigated the processing of a set of disease-causing variant SCAD proteins (R22W, G68C, W153R, R359C, and Q341H) and two common variant proteins (R147W and G185S) that lead to reduced SCAD activity. All SCAD proteins, including the wild type, associate with mitochondrial hsp60 chaperonins; however, the variant SCAD proteins remained associated with hsp60 for prolonged periods of time. Biogenesis experiments at two temperatures revealed that some of the variant proteins (R22W, G68C, W153R, and R359C) caused severe misfolding, whereas others (R147W, G185S, and Q341H) exhibited a less severe temperature-sensitive folding defect. Based on the magnitude of in vitro defects, these SCAD proteins are characterized as folding-defective variants and mild folding variants, respectively. Pulse-chase experiments demonstrated that the variant SCAD proteins either triggered proteolytic degradation by mitochondrial proteases or, especially at elevated temperature, aggregation of non-native conformers. The latter finding may indicate that accumulation of aggregated SCAD proteins may play a role in the pathogenesis of SCAD deficiency.