Functional inactivation of endogenous MDM2 and CHIP by HSP90 causes aberrant stabilization of mutant p53 in human cancer cells.
Functional inactivation of endogenous MDM2 and CHIP by HSP90 causes aberrant stabilization of mutant p53 in human cancer cells.
复制标题
DOI：
10.1158/1541-7786.mcr-10-0534
复制
发表时间：
2011-05
期刊：
影响因子：
--
通讯作者：
Moll UM
中科院分区：
文献类型：
--
作者：
Li D;Marchenko ND;Schulz R;Fischer V;Velasco-Hernandez T;Talos F;Moll UM
在正常细胞中主要由MDM2对野生型（wt）p53的严格控制在携带突变型p53（mutp53）的肿瘤中永久丧失，其表现出远远超过wtp53肿瘤的显著组成性p53超稳定性。重要的是，mutp53的超稳定性对于mutp53在体内的致癌功能获得至关重要。目前对这种失调机制的了解是零碎的，主要来自异位构建的细胞系统。重要的是，mutp53基因敲入小鼠证实，正常mutp53组织在MDM 2和其他E3连接酶中具有足够的酶储备，以维持对mutp53的完全控制。我们发现，在人类癌细胞中，内源性突变p53，尽管其与MDM2相互作用的能力，从一个深刻的缺乏泛素化作为其降解缺陷的根源。与wtp53相反，许多构象异常的mutp53蛋白与HSP 90分子伴侣机制形成复合物，以防止其聚集。与wtp53癌细胞相反，我们表明在mutp53癌细胞中，这种HSP 90相互作用阻断了内源性MDM 2和CHIP E3连接酶活性。通过针对HSF 1（HSP90途径的转录调节因子）的RNAi或通过直接敲低HSP90蛋白或通过用17 AAG药理学抑制HSP90活性来干扰HSP90破坏复合物，释放mutp53并重新激活内源性MDM 2和CHIP以降解mutp53。值得注意的是，17AAG在mutp53中比在wtp53癌细胞中诱导更强的活力丧失。我们的数据支持这样的理论，即在已建立的癌症中抑制体内mutp53水平可能会达到临床显著效果。
The tight control of wild-type (wt) p53 by mainly MDM2 in normal cells is permanently lost in tumors harboring mutant p53 (mutp53), which exhibit dramatic constitutive p53 hyperstabilization that far exceeds that of wtp53 tumors. Importantly, mutp53 hyperstabilization is critical for mutp53′s oncogenic gain-of function in vivo. Current insight into the mechanism of this dysregulation is fragmentary and largely derived from ectopically constructed cell systems. Importantly, mutp53 knockin mice established that normal mutp53 tissues have sufficient enzymatic reserves in MDM2 and other E3 ligases to maintain full control of mutp53. We find that in human cancer cells endogenous mutant p53, despite its ability to interact with MDM2, suffers from a profound lack of ubiquitination as the root of its degradation defect. In contrast to wtp53, the many mutp53 proteins which are conformationally aberrant are engaged in complexes with the HSP90 chaperone machinery to prevent its aggregation. In contrast to wtp53 cancer cells, we show that in mutp53 cancer cells this HSP90 interaction blocks the endogenous MDM2 and CHIP E3 ligase activity. Interference with HSP90 either by RNAi against HSF1, the transcriptional regulator of the HSP90 pathway, or by direct knockdown of Hsp90 protein or by pharmacological inhibition of Hsp90 activity with 17AAG destroys the complex, liberates mutp53 and reactivates endogenous MDM2 and CHIP to degrade mutp53. Of note, 17AAG induces a stronger viability loss in mutp53 than in wtp53 cancer cells. Our data supports the rationale that suppression of mutp53 levels in vivo in established cancers might achieve clinically significant effects.