EGR1 mediates neuronal damage via suppressing HIF1A-induced mitophagy following traumatic brain injury

Traumatic brain injury (TBI) remains a leading cause of neurological morbidity and mortality, characterized by complex pathophysiological cascades. Here, we investigate the role of the transcription factor EGR1 (early growth response 1) in modulating mitochondrial homeostasis via the HIF1A (hypoxia inducible factor 1, alpha subunit)-BNIP3 (BCL2/adenovirus E1B interacting protein 3) axis following TBI. Using integrated transcriptomic and epigenomic analyses, we identified EGR1 as a critical regulator of TBI pathology, with its expression acutely upregulated in neurons post-injury. Genetic ablation of Egr1 in mice significantly reduced neuronal apoptosis, preserved dendritic integrity, and ameliorated cognitive and sensorimotor deficits. Mechanistically, chromatin immunoprecipitation and luciferase assays revealed that EGR1 directly binds to the Hif1a promoter, repressing its transcription. Loss of EGR1 enhanced HIF1A-BNIP3-mediated mitophagy, reducing mitochondrial dysfunction and oxidative stress both in vitro and in vivo. Conversely, silencing HIF1A or BNIP3 abrogated the neuroprotective effects of EGR1 deficiency. These findings establish a novel EGR1-HIF1A-mitophagy signaling axis as a key determinant of TBI outcomes, highlighting EGR1 as a potential therapeutic target. Abbreviations: AAV: adeno-associated virus; ACTB/β-actin: actin, beta; AIF1/IBA1: allograft inflammatory factor 1; BAF: bafilomycin A1; BNIP3: BCL2/adenovirus E1B interacting protein 3; CCI: controlled cortical impact; COX8: cytochrome c oxidase subunit 8; CUT&Tag: cleavage under targets and tagmentation; DAPI: 4,’6-diamidino-2-phenylindole; DEGs: differentially expressed genes; eGFP: enhanced green fluorescent protein; EGR1: early growth response 1; GFAP: glial fibrillary acidic protein; GO: gene ontology; GSEA: gene set enrichment analysis; HCQ: hydroxychloroquine; HIF1A/HIF-1α: hypoxia inducible factor 1, alpha subunit; IGV: integrative genomics viewer; KEGG: Kyoto encyclopedia of genes and genomes; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; Lv: lentivirus; MAP2: microtubule-associated protein 2; mCherry: monomeric cherry fluorescent protein; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; MUT: mutant; MWM: Morris water maze; NAB1: Ngfi-A binding protein 1; NAB2: Ngfi-A binding protein 2; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; OGD: oxygen-glucose deprivation; OLIG2: oligodendrocyte transcription factor 2; PBS: phosphate-buffered saline; PECAM1/CD31: platelet/endothelial cell adhesion molecule 1; PFA: paraformaldehyde; PPI: protein-protein interaction; Puro: puromycin; ROI: region of interest; ROS: reactive oxygen species; SEM: standard error of the mean; SQSTM1/p62: sequestosome 1; TBI: traumatic brain injury; TOMM20: translocase of outer mitochondrial membrane 20; TSA: tyramide signal amplification; TUNEL: terminal deoxynucleotidyl transferase dUTP nick end labeling; VDAC1: voltage-dependent anion channel 1; WT: wild-type.