Catalase inhibition induces pexophagy through ROS accumulation

Peroxisomes are dynamic and multifunctional organelles involved in various cellular metabolic processes, and their numbers are tightly regulated by pexophagy, a selective degradation of peroxisomes through autophagy to maintain peroxisome homeostasis in cells. Catalase, a major peroxisome protein, plays a critical role in removing peroxisome-generated reactive oxygen species (ROS) produced by peroxisome enzymes, but the contribution of catalase to pexophagy has not been reported. Here, we investigated the role of catalase in peroxisome degradation during nutrient deprivation. Both short interfering RNA-mediated silencing of catalase and pharmacological inhibition by 3-aminotriazole (3AT) decreased the number of peroxisomes and resulted in the downregulation of peroxisomal proteins, such as PMP70 and PEX14 under serum starvation. In addition, treatment with 3AT induced NBR1-dependent autophagy and PEX5 ubiquitination in the absence of serum, which was accompanied by accumulation of ROS. Co-treatment with antioxidant agent N-acetyl-L-cysteine (NAC) prevented ROS accumulation and pexophagy by modulating peroxisome protein levels and the association of NBR1, a pexophagy receptor with peroxisomes. Taken together, these findings demonstrate that catalase plays an important role in pexophagy during nutrient deprivation.