CHFR negatively regulates SIRT1 activity upon oxidative stress

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• SIRT1 (NAD+-dependent protein deacetylase) regulates cell cycle and apoptosis by suppressing the p53 tumor suppressor.
• SIRT1 is known to be phosphorylated by JNK1 under oxidative stress, leading to its downregulation, but the precise mechanisms controlling its stability and activity remain unclear.

Purpose of the Study:

• To elucidate the role of CHFR in controlling SIRT1 stability and activity, particularly under oxidative stress conditions.
• To investigate the mechanism by which CHFR influences SIRT1-mediated regulation of p53.

Main Methods:

• Co-immunoprecipitation assays to detect protein-protein interactions between CHFR and SIRT1.
• Ubiquitylation assays to assess CHFR's E3 ligase activity towards SIRT1.
• Western blotting to analyze protein levels of SIRT1, p53, and acetylated p53.
• Cell viability assays to evaluate apoptosis in response to oxidative stress and CHFR/SIRT1 modulation.

Main Results:

• CHFR functions as an E3 ubiquitin ligase for SIRT1, mediating its ubiquitylation and subsequent proteasomal degradation under oxidative stress.
• CHFR-induced destabilization of SIRT1 results in increased acetylation of p53 and enhanced transcription of p53 target genes.
• CHFR facilitates SIRT1 destabilization following JNK1-mediated phosphorylation, leading to significant apoptotic cell death.
• Inhibition of JNK1 prevents SIRT1 phosphorylation and preserves SIRT1 protein levels, even under hydrogen peroxide (H2O2) exposure.

Conclusions:

• CHFR plays a critical role in the cellular stress response pathway by regulating SIRT1 stability and function.
• The CHFR-SIRT1 axis is a key determinant of cellular fate, influencing apoptosis under oxidative stress.
• Targeting the CHFR-mediated regulation of SIRT1 may offer therapeutic strategies for stress-related diseases and cancer.