NDUFB9 ameliorates CUMS-induced depression-like behavior by promoting mitophagy.

Major depressive disorder (MDD) is characterized by persistent low mood and anhedonia. Mitochondrial dysfunction is linked to MDD, but the mechanisms are unclear. In this study, transcriptomic analysis of MDD patients' peripheral blood found three key genes: TFAM, SURF1, and NDUFB9. Single-cell transcriptomic analysis of the prefrontal cortex (PFC) in MDD patients identified seven cell types. Analysis showed strong interactions between excitatory and inhibitory neurons in the PFC, with the three genes mainly in inhibitory neurons and NDUFB9 having the highest expression. We then established a chronic unpredictable mild stress (CUMS) mouse model. CUMS exposure induced depressive-like behaviors in mice, as evidenced by decreased sucrose preference, increased immobility time in the forced swim, and reduced activity and frequency of entries into the central area in the open field. Moreover, CUMS-exposed mice exhibited mitochondrial dysfunction in the prefrontal cortex (PFC). Notably, the expressions of TFAM, SURF1, and NDUFB9 were decreased in the PFC of CUMS mice, with the most significant decrease observed in NDUFB9. Subsequently, the overexpression of NDUFB9 in CUMS-treated mice significantly alleviated depressive-like behaviors, restored mitochondrial function and reduced the death of inhibitory neurons. It also enhanced mitophagy by PINK1/Parkin pathway. Inhibiting autophagy and mitophagy confirmed mitophagy's pivotal role in NDUFB9-mediated restoration. Co-IP and protein half-life assays revealed that NDUFB9 stabilizes PINK1, thereby promoting mitophagy. In conclusion, our findings reveal a novel role of NDUFB9 on alleviating depression-like behavior by enhancing mitophagy, suggesting that targeting NDUFB9 could offer a promising therapeutic strategy for MDD.