CHCHD2, Rather than FBXO7, Plays an Essential Role in Modulating the MPP⁺-Induced mtUPR

Parkinson's disease (PD) is characterized by mitochondrial dysfunction and impaired protein homeostasis, with the mitochondrial unfolded protein response (mtUPR) emerging as a key regulatory pathway in mitigating mitochondrial stress. This study aimed to explore the impact of shRNAs targeting CHCHD2 or FBXO7 on the mitochondrial unfolded protein response (mtUPR) in a Parkinson's disease (PD) cell model, clarify the mitochondrial-nuclear signaling pathways involving CHCHD2 and FBXO7, elucidate the mechanisms underlying mitochondrial dysfunction induced by these genes, and identify new therapeutic targets for early stage PD. An in vitro PD model was established by treating SH-SY5Y cells with MPP⁺; mitochondrial morphology was evaluated using transmission electron microscopy, and qRT-PCR and Western blot were employed to determine the expression levels of mRNAs and proteins associated with mtUPR, autophagy, CHCHD2, and FBXO7 under oxidative stress. In the MPP⁺-induced PD cell model, we knocked down CHCHD2 and FBXO7 via shRNA and treated the cells with JNK and AKT agonists to observe their effects on mtUPR protein expression. The results showed that mtUPR was activated in MPP⁺-exposed SH-SY5Y cells, and the expression of CHCHD2 and FBXO7 genes was significantly upregulated after MPP⁺ intervention; knockdown of CHCHD2 via shRNA resulted in a marked decrease in the expression of mtUPR-related proteins such as HSPA9, HSPD1, YME1L1, and CLPP, while shRNA targeting FBXO7 exerted only a minimal effect on these mtUPR proteins. Furthermore, the administration of JNK or AKT agonists significantly enhanced the expression of MPP⁺-induced mtUPR proteins, including HSPA9, HSPD1, YME1L1, and CLPP. Collectively, these findings indicate that CHCHD2, rather than FBXO7, plays an essential role in modulating the MPP⁺-induced mtUPR and suggest that CHCHD2 may regulate mitochondrial protein homeostasis by activating the mtUPR through the JNK/c-Jun and AKT/ERα pathways.