Intracellular APOL1 Risk Variants Cause Cytotoxicity Accompanied by Energy Depletion
Intracellular APOL1 Risk Variants Cause Cytotoxicity Accompanied by Energy Depletion
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DOI：
10.1681/asn.2016111220
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发表时间：
2017-11-01
影响因子：
13.6
通讯作者：
Weide, Thomas
中科院分区：
文献类型：
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作者：
Granado, Daniel;Mueller, Daria;Weide, Thomas
群体遗传学方法已经揭示了肾脏疾病与APOL 1基因的两个序列变体（称为APOL 1风险变体G1和变体G2）与非风险GO等位基因之间的强相关性。然而，这些变体导致疾病表现的机制，特别是这是否涉及APOL 1的细胞内或细胞外池仍不清楚。在此，我们显示了APOL 1 GO和肾风险变体的主要细胞内定位，其定位于足细胞系中的内质网膜。这种定位不依赖于介导APOL 1分泌到循环中的N-末端信号肽。此外，这些蛋白质的一部分定位于线粒体周围的结构。在体外过表达G1或G2缺乏信号肽抑制细胞活力，触发磷酸化的应激诱导的激酶，增加磷酸化的AMP激活的蛋白激酶，降低细胞内钾水平，并降低线粒体呼吸速率。这些发现表明，细胞内膜的功能，特别是内质网和线粒体的功能，是APOL 1肾风险变异介导的细胞损伤的关键因素。
Population genetic approaches have uncovered a strong association between kidney diseases and two sequence variants of the APOL1 gene, called APOL1 risk variant G1 and variant G2, compared with the nonrisk GO allele. However, the mechanism whereby these variants lead to disease manifestation and, in particular, whether this involves an intracellular or extracellular pool of APOL1 remains unclear. Herein, we show a predominantly intracellular localization of APOL1 GO and the renal risk variants, which localized to membranes of the endoplasmic reticulum in podocyte cell lines. This localization did not depend on the N-terminal signal peptide that mediates APOL1 secretion into the circulation. Additionally, a fraction of these proteins localized to structures surrounding mitochondria. In vitro overexpression of G1 or G2 lacking the signal peptide inhibited cell viability, triggered phosphorylation of stress-induced kinases, increased the phosphorylation of AMP activated protein kinase, reduced intracellular potassium levels, and reduced mitochondrial respiration rates. These findings indicate that functions at intracellular membranes, specifically those of the endoplasmic reticulum and mitochondria, are crucial factors in APOL1 renal risk variant-mediated cell injury.