Fig 2: The mitochondrial PHB2/OMA1/DELE1 pathway cooperates with endoplasmic reticulum stress to induce ovarian cancer cell death. Destruction of the prohibitin 2 (PHB2)/stomatin-like protein 2 (STOML2) complex releases OMA1 protease activity. Activated OMA1 cleaves optic atrophy 1 (OPA1) and DELE1, resulting in mitochondrial cristae remodeling and DELE1’s cytoplasmic interaction with EIF2AK1. Activated EIF2AK1 cooperates with EIF2AK3 to induce EIF2S1 phosphorylation, promoting the transfer of ATF4 into the nucleus and the upregulation of DDIT3 and ATF5. Then, pro-apoptotic proteins, BBC3, BCL2L11 and PMAIP1, are upregulated and anti-apoptotic protein MCL1 is downregulated, triggering accumulation of BAX and BAK1 on the mitochondrial outer membrane (MOM) and the rupture of the MOM. Under the coordination of mitochondrial inner and outer membranes, cytochrome c is released, and the cell dies. Green arrows indicate positive regulation; red arrow indicates negative regulation.

Fig 3: Effects of FCCP and cisplatin treatments in a mouse subcutaneous tumor model. ID8 cells were subcutaneously implanted into C57BL/6 mice. Mice were treated with 1 mg/kg FCCP and/or 2 mg/kg cisplatin for 12 days (each group, n = 6). Body weight and tumor volume were measured daily (a,b). The wet weight of tumors was measured at autopsy (c). Images of excised tumors (d). Representative images of TUNEL assay from subcutaneous tumors (scale bar, 30 µm) (e). Red fluorescence indicates TUNEL-positive cells. Subcutaneous tumors were lysed in RIPA and the expression of OPA1, OMA1 (f), p-EIF2S1, EIF2S1, p-EIF2AK3, EIF2AK3, ATF4, ATF5, DDIT3 (g), ATF4, ATF5, DDIT3 in the nucleus (h), BAX, MCL1, cleaved caspase-3, and cleaved caspase-9 (k) was measured. Relative mRNA expression of Atf4, Atf5, and Ddit3 (i), and Bcl2, Mcl1, Bcl2l11, Bbc3, and Pmaip1 (j) was measured. Data are presented as mean ± SD, n = 3. * p < 0.05 vs. con, ** p < 0.01 vs. con, # p < 0.05 vs. cisplatin and vs. FCCP. Localization of STOML2 and PHB2 in tumor specimens was measured by immunofluorescence staining (scale bar, 10 µm) (l).

Fig 4: PERK-ATF4-CHOP and IRE1-TRAF2 signaling pathways during autophagy in SH-SY5Y cells. (A) Representative western blotting images. (B-J) Protein expression quantification. Data are expressed as the mean ± standard deviation. N=4/group. ?P<0.05, ??P<0.01 vs. C; #P<0.05, ##P<0.01 vs. H; *P<0.05, **P<0.01 vs. HB. PERK, protein kinase R-like endoplasmic reticulum kinase; ATF4, activating transcription factor 4; CHOP, C/EBP-homologous protein; IRE1, inositol-requiring enzyme 1; TRAF2, tumor necrosis factor receptor associated factor 2; RAPA, rapamycin; p, phosphorylated; C, control group; H, high glucose group; HB, high glucose + bupivacaine group; HRB, high glucose + RAPA + bupivacaine group; HMB, high glucose + 3-MA + bupivacaine group.

Fig 5: Inhibiting PERK suppresses light-related autophagy. (A) 661W cells were infected with lentivirus-expressed PERK shRNA (sh-PERK) or negative control shRNA (NC). The level of PERK in the whole cell lysate was determined with western blotting, and ß-actin was referenced as an internal control. (B) 661W cells with stable PERK knockdown/ARPE-19 cells treated with GSK (5 µM) or vehicle were cultured under light/dark conditions for 3 days. The target proteins in the whole cell lysate were determined with western blotting, and ß-actin was referenced as an internal control. Three independent experiments are conducted two weeks apart. The results are presented as the mean± SEM. n (per group) =3, NS: no significance, *P < 0.05, **P < 0.01.