Proteasome activation by hepatitis C core protein is reversed by ethanol-induced oxidative stress
Proteasome activation by hepatitis C core protein is reversed by ethanol-induced oxidative stress
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DOI：
10.1053/j.gastro.2008.02.063
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发表时间：
2008-06-01
期刊：
影响因子：
29.4
通讯作者：
Donohue, Terrence M., Jr.
中科院分区：
文献类型：
--
作者：
Osna, Natalia A.;White, Ronda L.;Donohue, Terrence M., Jr.
背景与目的：蛋白酶体是一种主要的细胞蛋白水解酶。它的活性受细胞氧化剂的调节。丙型肝炎核心蛋白和酒精暴露都会导致氧化剂生成增加。其目的是调查核心蛋白是否通过其产生氧化剂的能力改变蛋白酶体的活性，以及这些改变是否进一步受到酒精暴露的影响。方法：在表达可诱导的丙型肝炎病毒核心蛋白和/或细胞色素P450 2E1的Huh-7细胞系中检测这些相互作用，并在无细胞体系中作为纯化组分。用荧光法测定胰凝乳酶样蛋白酶体活性。结果：在核心蛋白表达阳性的191-20细胞中，蛋白酶体活性比核心蛋白阴性的细胞高20%，而在表达细胞色素P450的L14细胞中，蛋白酶体活性增加了3倍。核心阳性细胞暴露于谷胱甘肽乙酯、过氧化氢酶或CYP2E1抑制剂二烯丙基硫化物，部分逆转了核心阳性细胞中蛋白酶体活性的升高，而乙醇暴露抑制了蛋白酶体活性。结果表明，蛋白酶体活性在低水平的核心诱导的氧化应激下被上调，而在高水平的乙醇诱导的应激下被下调。这些发现在无细胞系统中得到了部分模仿。添加核心蛋白可提高含有蛋白酶体激活剂PA28的纯化的20S蛋白酶体的多肽酶活性，加入肝脏线粒体和/或微生物体部分可进一步增强其活性。然而，当从乙醇喂养的动物中获得组分时，蛋白酶体的激活显著减弱。结论：丙型肝炎病毒核心蛋白与PA28、线粒体和内质网蛋白相互作用，导致低水平的氧化应激和蛋白酶体激活，当氧化剂生成量较高时，这种作用在乙醇代谢过程中受到抑制。
Background & Aims: The proteasome is a major cellular proteinase. Its activity is modulated by cellular oxidants. Hepatitis C core protein and ethanol exposure both cause enhanced oxidant generation. The aim was to investigate whether core protein, by its ability to generate oxidants, alters proteasome activity and whether these alterations are further affected by ethanol exposure. Methods: These interactions were examined in Huh-7 cell lines that expressed inducible HCV core protein and/or constitutive cytochrome P450 2E1 (CYP2E1) and as purified components in a cell-free system. Chymotrypsin-like proteasome activity was measured fluorometrically. Results: Proteasome activity in core-positive 191-20 cells was 20% higher than that in core-negative cells and was enhanced 3-fold in CYP2E1-expressing L14 cells. Exposure of core-positive cells to glutathione ethyl ester, catalase, or the CYP2E1 inhibitor diallyl sulfide partially reversed the elevation of proteasome activity in core-positive cells, whereas ethanol exposure suppressed proteasome activity. The results indicate that proteasome activity was up-regulated by low levels of core-induced oxidative stress but down-regulated by high levels of ethanol-elicited stress. These findings were partially mimicked in a cell-free system. Addition of core protein enhanced the peptidase activity of purified 20S proteasome containing the proteasome activator PA28 and was further potentiated by addition of liver mitochondrial and/or microsome fractions. However, proteasome activation was significantly attenuated when fractions were obtained from ethanol-fed animals. Conclusions: HCV core protein interacts with PA28, mitochondrial, and endoplasmic reticulum proteins to cause low levels of oxidant stress and proteasome activation, which is dampened during ethanol metabolism when oxidant generation is higher.