The manganese superoxide dismutase Ala16Val dimorphism modulates both mitochondrial import and mRNA stability
The manganese superoxide dismutase Ala16Val dimorphism modulates both mitochondrial import and mRNA stability
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DOI：
10.1097/01213011-200505000-00006
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发表时间：
2005-05-01
影响因子：
2.6
通讯作者：
Degoul, F
中科院分区：
文献类型：
--
作者：
Sutton, A;Imbert, A;Degoul, F
遗传二态性在锰超氧化物歧化酶（MnSOD）的线粒体靶向序列（MTS）中包含丙氨酸（Ala）或缬氨酸（Val）。将AlaMTS导入离体线粒体后，其MnSOD活性比ValMTS高40%。本研究旨在描述整个细胞的功能后果。用编码与myc - his -标签融合的人Ala-或Val-MnSOD变异体的载体转染HuH7人肝癌细胞。ala变异导致成熟外源蛋白水平和MnSOD活性比val变异高4倍。对蛋白酶体抑制剂的研究表明，前体蛋白要么被输入线粒体，要么被蛋白酶体降解。尽管转染后8小时的mRNA水平相同，但在36小时，ala编码mRNA的mRNA水平比Val-mRNA高两倍。线粒体膜电位的降低降低了MnSOD的线粒体进口量及其mRNA水平。人类Val-和Ala-MnSOD变体的活性在全细胞中比在体外进行的重要实验中观察到更大的差异。首先，缓慢导入的Val-MnSOD在细胞内被蛋白酶体降解。其次，val变异的线粒体输入较慢可能与mRNA稳定性下降有关，这可能是由于共翻译输入受损所致。(c) 2005年Lippincott Williams & Wilkins。
A genetic dimorphism incorporates either alanine (Ala) or valine (Val) in the mitochondrial targeting sequence (MTS) of manganese superoxide dismutase (MnSOD). The AlaMTS confers a 40% higher MnSOD activity than the ValMTS after import into isolated mitochondria in vitro. The present study aimed to characterize functional consequences in whole cells. HuH7 human hepatoma cells were transfected with vectors encoding for the human Ala- or Val-MnSOD variants fused to a Myc-His-tag. The Ala-variant resulted in four-fold higher levels of the mature exogenous protein and MnSOD activity than the Val-variant. Studies with a proteasome inhibitor indicated that precursor proteins are either imported into the mitochondria or degraded by the proteasome. Despite identical levels 8 h after transfection, mRNA levels at 36 h were two-fold higher for the Ala-encoding mRNA than the Val-mRNA. Decreasing the mitochondrial membrane potential decreased both MnSOD mitochondrial import and its mRNA levels. Much larger differences in the activity of the human Val- and Ala-MnSOD variants are observed in whole cells rather than after import experiments per-formed in vitro. First, the slowly imported Val-MnSOD is degraded by the proteasome in cells. Second, the slower mitochondrial import of the Val-variant may be associated with decreased mRNA stability, possibly due to impaired cotranslational import. (c) 2005 Lippincott Williams & Wilkins.