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von Hippel-Lindau 肿瘤抑制蛋白促进 c-Cbl 非依赖性的 EGFR 激活体多泛素化和降解。

The von Hippel-Lindau tumor suppressor protein promotes c-Cbl-independent poly-ubiquitylation and degradation of the activated EGFR.

机构信息

Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America.

出版信息

PLoS One. 2011;6(9):e23936. doi: 10.1371/journal.pone.0023936. Epub 2011 Sep 16.

Abstract

Somatic mutations or reduced expression of the von Hippel-Lindau (VHL) tumor suppressor occurs in the majority of the clear cell renal cell carcinoma (ccRCC) and is a causal factor for the pathogenesis of ccRCC. pVHL was reported to suppress the oncogenic activity of Epidermal Growth Factor Receptor (EGFR) by reducing the expression of the EGFR agonist TGF-α and by reducing the translation efficiency of EGFR itself. Furthermore, it was reported that pVHL down-regulates activated EGFR by promoting efficient lysosomal degradation of the receptor. These modes of negative regulation of EGFR by pVHL were dependent on Hypoxia Inducible Factor (HIF). In this study, we report that HIF was not the only factor stabilizing the activated EGFR in VHL-deficient ccRCC cells. Down-regulation of endogenous HIF in these cells had little effect on the turnover rates of the activated EGFR. Furthermore, neither pretreatment with lysosomal inhibitors pretreatment nor down-regulation of c-Cbl, a major E3 ubiquitin ligase that targets the activated EGFR for lysosomal degradation, significantly increased the stabilities of EGFR in VHL-expressing ccRCC cells. In contrast, pretreatment with proteasomal inhibitors extended EGFR lifetime and led to similar EGFR half-lives in VHL-expressing and VHL-deficient ccRCC cells. Down-regulation of c-Cbl in VHL-deficient ccRCC cells revealed that the c-Cbl and pVHL collaborated to down-regulate the activated EGFR. Finally, we found that pVHL promoted the poly-ubiquitylation of the activated EGFR, and this function was c-Cbl-independent. Thus these results indicate that pVHL limits EGFR signaling by promoting c-Cbl-independent poly-ubiquitylation of the activated receptor, which likely results in its degradation by proteasome.

摘要

抑瘤基因 VHL 的体细胞突变或表达缺失存在于多数肾透明细胞癌(ccRCC)中,是 ccRCC 发病的原因之一。有研究报道称 pVHL 通过降低表皮生长因子受体(EGFR)激动剂 TGF-α的表达和降低 EGFR 自身的翻译效率来抑制 EGFR 的致癌活性。此外,有研究报道称 pVHL 通过促进受体的溶酶体有效降解来下调激活的 EGFR。pVHL 对 EGFR 的这些负调控模式依赖于低氧诱导因子(HIF)。在本研究中,我们报告称 HIF 并非唯一能稳定 VHL 缺陷型 ccRCC 细胞中激活的 EGFR 的因素。这些细胞中内源性 HIF 的下调对激活的 EGFR 的周转率几乎没有影响。此外,溶酶体抑制剂预处理或下调主要针对激活的 EGFR 进行溶酶体降解的 E3 泛素连接酶 c-Cbl 都不会显著增加 VHL 表达型 ccRCC 细胞中 EGFR 的稳定性。相比之下,蛋白酶体抑制剂的预处理延长了 EGFR 的寿命,并导致 VHL 表达型和 VHL 缺陷型 ccRCC 细胞中 EGFR 的半衰期相似。VHL 缺陷型 ccRCC 细胞中 c-Cbl 的下调表明 c-Cbl 和 pVHL 协同下调激活的 EGFR。最后,我们发现 pVHL 促进了激活的 EGFR 的多泛素化,且这一功能不依赖于 c-Cbl。因此,这些结果表明 pVHL 通过促进 c-Cbl 非依赖性的激活受体多泛素化来限制 EGFR 信号通路,这可能导致其通过蛋白酶体降解。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/2dcf/3174936/98b3b302454c/pone.0023936.g001.jpg

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