Bcl-xL regulates radiation-induced ferroptosis through chaperone-mediated autophagy of GPX4 in tumor cells

Objective

To investigate the role and the molecular mechanisms of apoptotic signaling in ferroptosis to regulate tumor radiosensitivity.

Methods

Reactive oxygen species (ROS) and lipid peroxide levels were detected in Mouse embryonic fibroblasts(MEFs) with Bcl-xL or Mcl-1 deficiency induced by erastin. Colony formation, ROS, lipid peroxidation and the transcription/translation levels of PTGS2 were measured in Bcl-xL knockdown tumor cells induced by 5 ​Gy γ-rays or co-treated with ferrostatin-1 (Ferr-1). The protein levels of LPCAT3, ACSL4 and PEBP1 in Bcl-xL knockout MEF cells were evaluated in Bcl-xL knockout MEF cells post-radiation. Moreover, the interaction of heat shock protein 90 (HSP90) with Bcl-xL, GPX4, or LAMP2A was detected by protein mass spectrometry and immunoprecipitation assays.

Results

Manipulating Bcl-xL levels facilitated radiation-induced ferroptosis by augmenting the enzymatic oxidation of polyunsaturated fatty acids (PUFAs) and enhancing chaperone-mediated autophagy (CMA) of glutathione peroxidase 4 (GPX4) (MEF cell line: t=4.540, P＜0.01; A549 ​cell line: t=56.16, P＜0.0001; t=4.885, P＜0.01; HCT116 ​cell line: t=14.75, P＜0.01; t=7.363, P＜0.05). Downregulating Bcl-xL expression promoted the activity of acyl-CoA synthetase long-chain family member 4 (ACSL4), thus increasing the enzymatic oxidation of PUFAs (t=4.258, P＜0.01). Moreover, depletion of Bcl-xL expedited the CMA process targeting GPX4 by facilitating the association of GPX4 with heat shock protein 90 (HSP90) and LAMP2A following radiation exposure. Subsequent degradation of GPX4 led to the accumulation of lipid peroxides, ultimately triggering ferroptosis.

Conclusions

Our study provides initial insights into the regulatory role of Bcl-xL in ferroptosis and underscores the potential of targeting Bcl-xL as a promising therapeutic strategy for cancer by modulating both apoptotic and ferroptotic pathways.