Disruption of the Keap1-mTORC2 axis by cancer-derived Keap1/mLST8 mutations leads to oncogenic mTORC2-AKT activation

• Published in: Redox biology 2023-11, Vol.67, p.102872, Article 102872
• Main Authors: Chen, Yingji, Jiao, Dongyue, He, Huiying, Sun, Huiru, Liu, Yajuan, Shi, Qing, Zhang, Pingzhao, Li, Yao, Mo, Ren, Gao, Kun, Wang, Chenji
• Format: Article
• Language: English
• Subjects: AKT; Keap1; Lung cancer; mTORC2; Research Paper; ROS; Ubiquitination
• ISSN: 2213-2317; 2213-2317
• DOI: 10.1016/j.redox.2023.102872

The mechanistic target of the rapamycin (mTOR) pathway, which participates in the regulation of cellular growth and metabolism, is aberrantly regulated in various cancer types. The mTOR complex 2 (mTORC2), which consists of the core components mTOR, Rictor, mSin1, and mLST8, primarily responds to growth signals. However, the coordination between mTORC2 assembly and activity remains poorly understood. Keap1, a major sensor of oxidative stress in cells, functions as a substrate adaptor for Cullin 3-RING E3 ubiquitin ligase (CRL3) to promote proteasomal degradation of NF-E2-related factor 2 (NRF2), which is a transcription factor that protects cells against oxidative and electrophilic stress. In the present study, we demonstrate that Keap1 binds to mLST8 via a conserved ETGE motif. The CRL3Keap1 ubiquitin ligase complex promotes non-degradative ubiquitination of mLST8, thus reducing mTORC2 complex integrity and mTORC2-AKT activation. However, this effect can be prevented by oxidative/electrophilic stresses and growth factor signaling-induced reactive oxygen species (ROS) burst. Cancer-derived Keap1 or mLST8 mutations disrupt the Keap1-mLST8 interaction and allow mLST8 to evade Keap1-mediated ubiquitination, thereby enhancing mTORC2-AKT activation and promoting cell malignancy and remodeling cell metabolism. Our findings provide new insights into the molecular mechanisms of Keap1/mLST8 mutation-driven tumorigenesis by promoting mTORC2-AKT activation, which is independent of the canonical NRF2 pathway. [Display omitted] •Keap1, a substrate adaptor for Cullin 3-RING E3 ubiquitin ligase (CRL3), is a novel mLST8-interacting protein.•CRL3Keap1 complex promotes non-degradative ubiquitination of mLST8, leading to reduced mTORC2 complex integrity and mTORC2-AKT activation.•Both H2O2 exposure and EGF stimulation decrease mLST8 ubiquitination, which correlate with increased mTORC2 activity.•Cancer-derived Keap1 or mLST8 mutations disrupt the Keap1-mLST8 interaction and allow mLST8 to evade Keap1-mediated ubiquitination.•Cancer-derived mLST8 mutations activate the mTORC2-AKT pathway, promoting cell malignancy and remodeling cell metabolism.