Missense UROS mutations causing congenital erythropoietic porphyria reduce UROS homeostasis that can be rescued by proteasome inhibition
Missense UROS mutations causing congenital erythropoietic porphyria reduce UROS homeostasis that can be rescued by proteasome inhibition
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DOI：
10.1093/hmg/ddx067
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发表时间：
2017-04-15
影响因子：
3.5
通讯作者：
Richard, Emmanuel
中科院分区：
文献类型：
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作者：
Blouin, Jean-Marc;Bernardo-Seisdedos, Ganeko;Richard, Emmanuel
先天性红细胞生成性卟啉症(CEP)是一种先天的血红素生物合成错误，其特征是尿卟啉原III合成酶(Uros)缺乏，导致有害的卟啉聚集在血细胞中，导致溶血性贫血和皮肤光敏。我们在这里分析了CEP患者中实际描述的29个Uros错义突变与Uros损伤相关的分子基础。使用计算和生物物理联合方法，我们预测大多数致病突变将影响Uros折叠和稳定性。通过对增强型绿色荧光蛋白标记的Uros酶的分析，我们通过实验证实了这些数据，并表明热力学不稳定和蛋白质过早降解是导致人类细胞中20个Uros突变相关的酶缺陷的主要机制。由于细胞内蛋白质动态平衡的丧失与体外的失稳有很好的一致性，我们使用分子动力学模拟来依赖Uros失能的结构3D修饰。我们发现，根据致病Uros酶内侧链重排或接触改变，不稳定突变可以聚集在三种机制中，其严重程度与细胞蛋白质不稳定性相关。此外，使用临床上可用的药物Bortezomib抑制蛋白酶体显著增强了每个不稳定的Uros突变体的蛋白稳定性。最后，我们的证据表明，蛋白质稳态异常是导致Uros缺乏症的普遍机制，当CEP患者的基因包含错义变体时，Uros蛋白分解的调节剂，如蛋白酶体抑制剂或化学伴侣，可能代表着一种有吸引力的治疗选择，以减少卟啉蓄积和防止皮肤光敏。
Congenital erythropoietic porphyria (CEP) is an inborn error of heme biosynthesis characterized by uroporphyrinogen III synthase (UROS) deficiency resulting in deleterious porphyrin accumulation in blood cells responsible for hemolytic anemia and cutaneous photosensitivity. We analyzed here the molecular basis of UROS impairment associated with twenty nine UROS missense mutations actually described in CEP patients. Using a computational and biophysical joint approach we predicted that most disease-causing mutations would affect UROS folding and stability. Through the analysis of enhanced green fluorescent protein-tagged versions of UROS enzyme we experimentally confirmed these data and showed that thermodynamic instability and premature protein degradation is a major mechanism accounting for the enzymatic deficiency associated with twenty UROS mutants in human cells. Since the intracellular loss in protein homeostasis is in excellent agreement with the in vitro destabilization, we used molecular dynamic simulation to rely structural 3D modification with UROS disability. We found that destabilizing mutations could be clustered within three types of mechanism according to side chain rearrangements or contact alterations within the pathogenic UROS enzyme so that the severity degree correlated with cellular protein instability. Furthermore, proteasome inhibition using bortezomib, a clinically available drug, significantly enhanced proteostasis of each unstable UROS mutant. Finally, we show evidence that abnormal protein homeostasis is a prevalent mechanism responsible for UROS deficiency and that modulators of UROS proteolysis such as proteasome inhibitors or chemical chaperones may represent an attractive therapeutic option to reduce porphyrin accumulation and prevent skin photosensitivity in CEP patients when the genotype includes a missense variant.