APEX1 attenuates ERS-induced paraptosis by inhibiting the P53 pathway in LECs

Age-related cortical cataract (ARCC) is a prominent subtype of cataract, characterized by the presence of vacuoles and spoke-like opacity. Previous studies have suggested that paraptosis is involved in the onset of early ARCC vacuolar degeneration. In this experiment, hydrogen peroxide (H₂O₂)-induced SRA01/04 cells were used to establish a paraptosis-like cell model, and the function and underlying mechanism of APEX1 in this cell model were explored. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blot analyses were conducted to assess the expression of pertinent genes in SRA01/04. Confocal fluorescence microscopy, using ER-tracker kits, was applied to clarify the relationship between the endoplasmic reticulum and intracellular vacuoles. The co-IP assay was used to verify the interaction between APEX1 and P53. The GTRD database was employed to predict the putative target genes combined with P53, and CUT&RUN assay was employed to confirm the enrichment of the P53 and ATF6 promoters following APEX1 overexpression. Firstly, the pathological sections of the vacuolar degeneration zone in the lens cortex of ARCC patients exhibited fiber disarray and vacuole development. Meanwhile, the protein expression of Alix, a specific paraptosis inhibitor, was decreased in low-concentration H₂O₂-treated SRA01/04 cells. Secondly, we discovered that 4-PBA suppressed the expression of ATF6 and PERK. Moreover, overexpression of APEX1 in SRA01/04 cells improved endoplasmic reticulum morphology, inhibited the interaction between P53 and ATF6, and attenuated paraptosis in SRA01/04. APEX1 regulated P53 and then mediated ATF6 to affect the endoplasmic reticulum stress and paraptosis in H₂O₂-induced SRA01/04 cells.