Mitochondrial complex I subunit NDUFS4 overexpression drives glioma progression by regulating mitochondrial function and COX5B

The current study explores the expression, functional significance, and underlying mechanisms of the mitochondrial protein NDUFS4 (NADH:ubiquinone oxidoreductase subunit S4) in glioma cells. TCGA shows that elevated NDUFS4 expression is consistently observed in glioma tissues, correlating with advanced tumor grade and diminished patient survival. Single-cell RNA sequencing further localizes this elevated expression primarily to glioma cells, where NDUFS4 co-expressed genes are integral to cellular respiration and mitochondrial ATP synthesis. These findings were corroborated in patient tissues and various primary and established glioma cell types, confirming consistent NDUFS4 overexpression. Genetic silencing (via shRNA) or CRISPR/Cas9-mediated knockout of NDUFS4 impaired mitochondrial function, evidenced by reduced oxygen consumption rate, inhibited mitochondrial complex I activity and ATP production and increased oxidative stress. NDUFS4 depletion also suppressed glioma cell proliferation, migration, and invasion, while promoting apoptosis. This inhibitory effect is specific to malignant cells, sparing non-cancerous astrocytes. Conversely, NDUFS4 overexpression enhanced mitochondrial activity and promoted aggressive malignant phenotypes in primary and immortalized glioma cells. Further multi-omics integration and experimental investigation established COX5B (cytochrome c oxidase subunit 5B) as an important downstream effector of NDUFS4. shRNA-induced silencing of COX5B replicated the outcomes of NDUFS4 depletion in primary glioma cells, and crucially, restoring COX5B in NDUFS4-silenced glioma cells abrogated the anti-glioma effects. In vivo studies demonstrated that NDUFS4 silencing effectively impeded intracranial growth of patient-derived glioma xenografts by compromising mitochondrial function, downregulating COX5B, inhibiting proliferation and inducing apoptosis. Collectively, these comprehensive data underscore NDUFS4's essential role in glioma progression and position it as a promising therapeutic target for this aggressive malignancy.