Hsp90 regulates a von Hippel Lindau-independent hypoxia-inducible factor-1α-degradative pathway
Hsp90 regulates a von Hippel Lindau-independent hypoxia-inducible factor-1α-degradative pathway
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DOI：
10.1074/jbc.m204733200
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发表时间：
2002-08-16
影响因子：
4.8
通讯作者：
Neckers, LM
中科院分区：
文献类型：
--
作者：
Isaacs, JS;Jung, YJ;Neckers, LM
HIF-1 α是一种在缺氧条件下稳定和激活的促血管生成转录因子。虽然von Hippel Lindau（VHL）基因产物（负责调节HIF-1 α蛋白水平的泛素连接酶）在常氧条件下有效靶向HIF-1 α进行快速蛋白酶体依赖性降解，但HIF-1 α在缺氧条件下对VHL的不稳定作用具有抗性。HIF-1 α还与分子伴侣Hsp 90结合。为了检测Hsp 90在HIF-1 α功能中的作用，我们使用了在常氧条件下缺乏功能性VHL并表达稳定HIF-1 α蛋白的肾癌细胞系。Geldanamycin（GA）是一种Hsp 90拮抗剂，在常氧和缺氧条件下均可促进肾癌细胞中HIF-1 α的泛素化和蛋白酶体介导的降解。此外，阻断VHL结合的HIF-1 α点突变并不能保护HIF-1 α免受GA诱导的不稳定性。Hsp 90拮抗剂还抑制HIF-1 α转录活性，并显着降低缺氧诱导的VEGF mRNA积累和缺氧依赖性血管生成活性。这些发现表明，Hsp 90功能的破坏1）促进HIF-1 α通过一种新的，不依赖氧的E3泛素连接酶降解，2）降低HIF-1 α的转录活性。Hsp 90依赖性途径消除HIF-1 α的存在预示着Hsp 90拮抗剂可能是缺氧细胞增敏剂并具有体内抗血管生成活性，从而扩展了这些药物作为治疗性抗癌剂的效用。
HIF-1alpha is a normally labile proangiogenic transcription factor that is stabilized and activated in hypoxia. Although the von Hippel Lindau (VHL) gene product, the ubiquitin ligase responsible for regulating HIF-1alpha protein levels, efficiently targets HIF-1alpha for rapid proteasome-dependent degradation under normoxia, HIF-1alpha is resistant to the destabilizing effects of VHL under hypoxia. HIF-1alpha also associates with the molecular chaperone Hsp90. To examine the role of Hsp90 in HIF-1alpha function, we used renal carcinoma cell (RCC) lines that lack functional VHL and express stable HIF-1alpha protein under normoxia. Geldanamycin (GA), an Hsp90 antagonist, promoted efficient ubiquitination and proteasome-mediated degradation of HIF-1alpha in RCC in both normoxia and hypoxia. Furthermore, HIF-1alpha point mutations that block VHL association did not protect HIF-1alpha from GA-induced destabilization. Hsp90 antagonists also inhibited HIF-1alpha transcriptional activity and dramatically reduced both hypoxia-induced accumulation of VEGF mRNA and hypoxia-dependent angiogenic activity. These findings demonstrate that disruption of Hsp90 function 1) promotes HIF-1alpha degradation via a novel, oxygen-independent E3 ubiquitin ligase and 2) diminishes HIF-1alpha transcriptional activity. Existence of an Hsp90-dependent pathway for elimination of HIF-1alpha predicts that Hsp90 antagonists may be hypoxic cell sensitizers and possess antiangiogenic activity in vivo, thus extending the utility of these drugs as therapeutic anticancer agents.