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. 2012 Dec;8(12):1856-8.
doi: 10.4161/auto.22024. Epub 2012 Sep 10.

Protective autophagy induced by RBX1/ROC1 knockdown or CRL inactivation via modulating the DEPTOR-MTOR axis (VSports注册入口)

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"V体育2025版" Protective autophagy induced by RBX1/ROC1 knockdown or CRL inactivation via modulating the DEPTOR-MTOR axis

Dongqin Yang et al. Autophagy. 2012 Dec.

V体育ios版 - Abstract

RBX1/ROC1 is an essential subunit of the largest multiunit Cullin-RING E3 ligase (CRL), which controls the degradation of diverse substrates, thereby regulating numerous cellular processes VSports手机版. Recently, we reported that RBX1 is overexpressed in hepatocellular carcinomas (HCC) and its expression is negatively correlated with patient survival. Moreover, siRNA silencing of RBX1 inhibits the proliferation of liver cancer cells both in vitro and in vivo by inducing CDKN1A/p21-dependent cell senescence. Interestingly, independent of senescence, RBX1 knockdown also triggers an autophagy response, due, at least in part, to the accumulation of the MTOR-inhibitory protein DEPTOR, a recently identified CRL substrate. Biologically, blockage of autophagy significantly enhances the growth-suppressive effect of RBX1 knockdown by triggering massive apoptosis, indicating that the autophagy response upon RBX1 knockdown serves as a survival signal in liver cells. Similar observations were also made in many types of human cancer cells upon inhibition of CRL by MLN4924. These findings suggest that RBX1-CRL is a promising anti-cancer drug target and provide proof-of-concept evidence for a novel drug combination of RBX1-CRL inhibitor and autophagy inhibitor for effective treatment of human cancer. .

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Figure 1. Inactivation of RBX1-CRL E3 ligase triggers protective autophagy. RBX1 is an essential subunit of CRL, which binds to CUL and substrate receptors to assemble functional CRLs. As an appealing anticancer target, RBX1 knockdown induces CDKN1A/p21-dependent senescence to suppress the growth of liver cancer cells. Interestingly, RBX1 knockdown also triggers an autophagy response by inducing the accumulation of the MTOR-inhibitory protein DEPTOR, resulting in the inactivation of MTOR. Similarly, CRL inhibitor MLN4924 also triggers autophagy by blockage of MTOR signals via DEPTOR as well as the HIF1A-DDIT4/REDD1-TSC1/2 axis. The autophagy response serves as a prosurvival signal since blockage of the autophagy pathway via siRNA silencing of essential autophagy genes (ATG5 or BECN1) or treatment with autophagy inhibitors significantly enhances the growth-suppressive effect of RBX1-CRL inactivation by triggering massive apoptosis in cancer cells. SR, substrate receptor, 3MA, 3-methyladenine, N8, NEDD8.

Comment on

  • Yang D, Li L, Liu H, Wu L, Luo Z, Li H, et al. Induction of autophagy and senescence by knockdown of ROC1 E3 ubiquitin ligase to suppress the growth of liver cancer cells. Cell Death Differ. 2012 doi: 10.1038/cdd.2012.113.
  • Zhao Y, Xiong X, Jia L, Sun Y. Targeting Cullin-RING ligases by MLN4924 induces autophagy via modulating the HIF1-REDD1-TSC1-mTORC1-DEPTOR axis. Cell Death Dis. 2012;3:e386. doi: 10.1038/cddis.2012.125.

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