EAAT1 sustains redox homeostasis and temozolomide resistance through glutamate-dependent regulation of the Keap1/Nrf2 axis in glioblastoma.

Glioblastoma (GBM) exhibits profound metabolic and redox adaptation that supports tumor progression and therapeutic resistance. Here, we identify the glutamate transporter EAAT1 (SLC1A3) as a critical regulator of glutamate-dependent redox homeostasis in GBM. Analysis of TCGA, GTEx, and CGGA datasets showed that EAAT1 expression is elevated in GBM and that higher EAAT1 expression is associated with poor patient survival. Using CRISPR/Cas9-mediated EAAT1 knockout together with biochemical, imaging, transcriptomic, and in vivo approaches, we found that loss of EAAT1 altered extracellular and intracellular glutamate homeostasis, reduced intracellular glutamate, glutamine, and glutathione levels, and increased reactive oxygen species (ROS) accumulation. EAAT1 deficiency also suppressed oxidative phosphorylation and ROS-related programs and attenuated the Keap1/Nrf2/HO-1 antioxidant axis, accompanied by reduced GPX4 expression and increased lipid peroxidation. Furthermore, EAAT1 ablation downregulated glutamine synthetase and glutaminase, suggesting impaired glutamine-dependent anaplerotic metabolism. Glutamate supplementation partially restored Keap1/Nrf2/HO-1 pathway protein expression in EAAT1-knockout cells. Functionally, EAAT1 loss inhibited GBM cell proliferation and migration, enhanced sensitivity to oxidative stress and temozolomide (TMZ), and reduced tumor growth in xenograft models. Collectively, our findings establish EAAT1 as a key metabolic regulator linking glutamate transport to antioxidant defense and therapeutic response in GBM. Targeting EAAT1 may therefore represent a metabolic vulnerability for overcoming metabolic and redox adaptation and improving TMZ responsiveness in GBM.