mTORC2 Regulates Non-homologous End Joining Through Modulating the Temporal Dynamics of 53BP1

Area of Science:

• Molecular Biology
• Cellular Biology
• Cancer Research

Background:

• Genomic integrity is maintained by DNA damage repair (DDR) pathways.
• Dysregulation of DDR is linked to cancer development.
• The role of mammalian target of rapamycin complex 2 (mTORC2) in DDR is not fully understood.

Purpose of the Study:

• To investigate the function of mTORC2 in the DNA damage response.
• To elucidate the impact of mTORC2 deficiency on protein phosphorylation dynamics following DNA double-strand breaks (DSBs).
• To explore the therapeutic implications of targeting mTORC2 in renal cancer.

Main Methods:

• Quantitative phosphoproteomics was employed to analyze protein phosphorylation changes in Rictor-knockdown (mTORC2 deficient) renal cancer cells after ionizing radiation (IR) exposure.
• Mechanistic studies investigated the spatiotemporal dynamics of p53 binding protein 1 (53BP1) and the involvement of protein kinase B (PKB/Akt) and cyclin-dependent kinase 1 (CDK1).
• Non-homologous end joining (NHEJ) pathway efficiency and 53BP1 foci maintenance were assessed.

Main Results:

• Rictor knockdown significantly altered protein phosphorylation dynamics in response to IR.
• mTORC2 deficiency impacted the phosphorylation of key signaling molecules in the NHEJ pathway.
• Rictor knockdown affected 53BP1 spatiotemporal dynamics, reduced NHEJ efficiency, and prolonged 53BP1 nuclear foci maintenance.
• mTORC2 modulated DSB repair via PKB/Akt and CDK1 pathways.
• Rictor knockdown led to hypersensitivity to IR and chemotherapeutic agents in renal cancer cells.

Conclusions:

• mTORC2 plays a crucial role in regulating DNA double-strand break repair dynamics, particularly through its influence on 53BP1.
• Targeting mTORC2 in combination with genotoxic therapies may represent a promising strategy for renal cancer treatment.