GRP75 Chaperone-driven Mitochondria–ER Membrane Coupling Promotes Ca2+-Dependent ROS Accumulation and Ferroptosis During Hypoxic Stress

Abstract Ferroptosis is a recently identified form of regulated cell death triggered by the accumulation of iron-dependent lipid peroxides. Nevertheless, the exact function and mechanism of ferroptosis in oxidative stress injury caused by environmental challenges, especially in hypoxic stress, remains unknown. Here, we demonstrate that hypoxic stress induces an aberrant increase in mitochondria-associated ER membrane (MAM) formation both in vitro and in vivo in largemouth bass. Transcriptome analysis reveals significant upregulation of the ferroptosis pathway. Combining transcriptomics, western blot, and immunostaining results, we identify GRP75 as a key regulator of MAM formation under hypoxic conditions. Further studies demonstrate that silencing GRP75 protects hepatocytes from hypoxia-induced cellular damage hallmarked by ferroptosis. Mechanistically, the excessive formation of MAM caused by GRP75 accelerating Ca²⁺ transfer, mediating mitochondrial and ER dysfunction, leading to ROS accumulation. Based on these findings, MAMs are considered an essential component in the execution of ferroptosis.