Nitric oxide-dependent proteasomal degradation of cytochrome P4502B proteins
Nitric oxide-dependent proteasomal degradation of cytochrome P4502B proteins
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DOI：
10.1074/jbc.m708821200
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发表时间：
2008-01-11
影响因子：
4.8
通讯作者：
Morgan, Edward T.
中科院分区：
文献类型：
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作者：
Lee, Choon-Myung;Kim, Bong-Yoon;Morgan, Edward T.
在肝脏和原代培养的肝细胞中，暴露于炎性物质或细胞因子会导致细胞色素P450(CYP)酶活性和表达的抑制。我们先前的研究表明，在原代培养的大鼠肝细胞中，苯巴比妥诱导的CYP2B蛋白在暴露于细菌内毒素(脂多糖)后以一氧化氮(NO)依赖的方式下调。在本研究中，我们发现在原代培养的大鼠肝细胞中，白介素1β(IL-1)处理6h后，细胞色素P450 2B蛋白的表达被抑制了60%。NO供体(Z)-1-[2-(2-氨乙基)-N-(2-氨乙基)氨基二氮-1-1，2-二甘醇(NOC-18)，S-亚硝基-谷胱甘肽和S-亚硝基-N-乙酰青霉胺]处理的细胞也抑制了细胞色素P450-2B的蛋白表达。然而，IL-1的下调对cGMP依赖的蛋白激酶的抑制不敏感。用不影响NO产生的蛋白酶体抑制剂MG132和lactacystin处理后，IL-1或NO供体的下调作用被取消。钙蛋白酶抑制剂E64-d或溶酶体蛋白水解酶抑制剂NH4Cl和氯喹不能减弱IL-1对细胞色素P450 2 B的下调作用。用NOC-18处理表达c-Myc标记的CYP2B1的HeLa细胞，下调其表达并增强其泛素化。在体外泛素化实验中，S-亚硝基谷胱甘肽处理大鼠肝微粒体可引起细胞色素P450 2B蛋白的S亚硝化，并增强其泛素化模式。这些数据与NO依赖的CYP2B泛素化和蛋白酶体降解依赖于活性氮物种的蛋白质修饰的假设是一致的。
Exposure to inflammatory agents or cytokines causes the suppression of cytochrome P450 (CYP) enzyme activities and expression in liver and primary hepatocyte cultures. We showed previously that phenobarbital-induced CYP2B protein is down-regulated in primary cultures of rat hepatocytes after exposure to bacterial endotoxin ( lipopolysaccharide) in a nitric oxide (NO)-dependent manner. In this study, we found that CYP2B proteins in primary rat hepatocyte cultures were suppressed > 60% after 6 h of treatment with interleukin-1 beta (IL-1). This effect was NO-dependent, and treatment of cells with the NO donors (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) aminodiazen-1-ium-1,2-diolate (NOC-18), S-nitrosoglutathione, and S-nitroso-N-acetylpenicillamine also suppressed CYP2B proteins. However, the down-regulation by IL-1 was insensitive to inhibition of cGMP-dependent protein kinases. The down-regulation by IL-1 or NO donors was abolished by treatments with the proteasome inhibitors MG132 and lactacystin that did not affect NO production. The calpain inhibitor E64-d or the lysosomal protease inhibitors NH4Cl and chloroquine did not attenuate the down-regulation of CYP2B by IL-1. Treatment of HeLa cells expressing c-Myc-tagged CYP2B1 with NOC-18 down-regulated its expression and enhanced its ubiquitination. Treatment of rat liver microsomes with S-nitrosoglutathione caused S-nitrosylation of CYP2B protein and enhanced the ubiquitination pattern of CYP2B compared with unmodified CYP2B in an in vitro ubiquitination assay. These data are consistent with the hypothesis that NO-dependent CYP2B ubiquitination and proteasomal degradation are dependent on protein modification by reactive nitrogen species.