Activation of FANCC attenuates mitochondrial ROS-driven necroptosis by targeting TBK1-dependent mitophagy in astrocytes after spinal cord injury.

Rationale: Necroptosis in astrocytes induced by mitochondrial dysfunction following spinal cord injury (SCI) significantly contributes to neuronal functional deficits. Mitophagy plays a crucial role in clearing damaged mitochondria and inhibiting necroptosis. Fanconi anemia complementation group C (FANCC), a member of the Fanconi anemia gene family, exerts a protective role by facilitating mitophagy in immune processes. However, the role of FANCC in SCI-induced astrocytic necroptosis and the underlying mechanisms remain unexplored.

Methods

Astrocyte-specific FANCC conditional knockout (Fanccfl/fl-GFAP-Cre) mice, obtained by mating Fanccfl/fl mice with GFAP-Cre mice, served as a model of moderate thoracic spinal cord contusion injuries. Using bulk and single-nucleus RNA sequencing, we investigated the protective role of FANCC in astrocytes after SCI. We assessed necroptosis and mitophagy in astrocytes through quantitative PCR, western blotting, flow cytometry, immunofluorescence, and transmission electron microscopy. Molecular mechanisms were explored via co-immunoprecipitation, proteomics, molecular docking, and confocal imaging. Computer virtual screening identified poliumoside as a FANCC activator. Histopathological staining and functional assessments (gait analysis, Basso Mouse Scale, and hindlimb reflex score) were conducted to evaluate the therapeutic effects of poliumoside on SCI.

Results

Astrocytic FANCC deficiency exacerbated necroptosis and mitochondrial damage, leading to severe neurological deficits. Conversely, FANCC overexpression increased PTEN-induced kinase 1-Parkin expression, thereby activating mitophagy and reducing necroptosis. Proteomics revealed FANCC's interaction with a specific peptide of TANK-binding kinase 1 (TBK1), which further promoted mitophagy. Treatment with the FANCC activator poliumoside improved neural pathology and motor function recovery in SCI mice.

Conclusion

The current study indicated that FANCC interacts with TBK1 and consequently mediates Parkin translocation, activates mitophagy, and inhibits astrocyte necroptosis. Our findings demonstrate the neuroprotective role and therapeutic potential of FANCC for SCI amelioration.