AMPK γ-Subunit Isoform Switching Governs Temozolomide Resistance and Survival in Glioblastoma

Temozolomide (TMZ) resistance remains a fundamental obstacle in the treatment of glioblastoma (GBM). While the metabolic sensor AMPK is known to influence cancer cell survival, the specific role of its regulatory γ-subunit isoforms in orchestrating chemoresistance is poorly understood. This study investigates how the dynamic remodeling of the AMPK heterotrimer contributes to TMZ evasion in GBM. We observed significantly low expression of AMPKγ2 in glioma patient samples, but the treatment of GBM cell lines with TMZ led to a robust increase in AMPKγ2 expression with a concomitant decrease in AMPKγ1 expression. We identified a significant "isoform switch" in TMZ-treated cells, characterized by a marked downregulation of the γ1 subunit and a reciprocal upregulation of γ2. The structural remodeling of the AMPK complex was validated using co-immunoprecipitation (Co-IP). Co-IP analysis confirmed that the AMPK α catalytic subunit shifts its primary association from γ1 to γ2 during the TMZ treatment. Functionally, γ2-dominant complexes exhibited reduced sensitivity to ATP-mediated inhibition, allowing resistant cells to maintain better ATP homeostasis and sustained AMPK activation under TMZ-induced stress. Furthermore, the knockdown of the γ2 subunit abolished this metabolic advantage, resulting in the resensitization of GBM cell lines to TMZ-induced cell death. Our findings reveal that AMPK γ-subunit isoform switching is a previously unrecognized metabolic adaptation that drives TMZ resistance in GBM. Targeting the γ2-specific complex or preventing this isoform transition represents a promising therapeutic strategy to overcome chemoresistance in malignant gliomas.