LAMP2A-dependent chaperone-mediated autophagy enhances oxidative stress resistance in gastric cancer cells through selective degradation of accumulated oxidized DJ-1

Abstract

Reactive oxygen species (ROS) function as potent activators of chaperone-mediated autophagy (CMA). While previous investigations have demonstrated that CMA facilitates cancer cell survival through selective degradation of oxidatively damaged proteins, the precise molecular mechanisms remain poorly defined. Hence, it is important to investigate the correlation between CMA and the antioxidative stress within tumor cells and elucidate its specific mechanism. LAMP2A expression profiles in gastric carcinoma cell lines and clinical specimens were quantified via qPCR, WB and immunohistochemical analysis. An in vitro oxidative stress model was established through 24-hour hydrogen peroxide (H2O2) exposure. Gastric cancer cell models with knockdown and overexpression of LAMP2A were established. Apoptotic indices and proliferative capacity were assessed through high-throughput flow cytometry and CCK-8 viability assays. The interaction between LAMP2A and DJ-1 was investigated via co-immunoprecipitation and confocal microscopy. This study demonstrates that LAMP2A is upregulated in gastric cancer and further induced by oxidative stress. Down-regulated LAMP2A impaired CMA functionality, sensitizing gastric cancer cells to oxidative cytotoxicity and significantly augmenting apoptosis rates. Elevated DJ-1 levels in gastric cancer cells are further amplified by oxidative stress, with severe stress enhancing LAMP2A-DJ-1 colocalization. Mechanistically, CMA inhibition precipitated accumulation of hyperoxidized DJ-1 isoforms, concomitant with pro-apoptotic BAX upregulation and anti-apoptotic BCL-2 downregulation. We found hyperoxidized DJ-1 as a novel CMA substrate. The LAMP2A-DJ-1 regulatory axis represents a critical adaptive mechanism whereby CMA activation maintains redox homeostasis in gastric malignancies. Specifically, CMA-mediated clearance of oxidized DJ-1 prevents pro-apoptotic protein cascade activation, thereby conferring oxidative stress resistance and promoting tumor cell survival.