SFXN2 contributes mitochondrial dysfunction-induced apoptosis as a substrate of Parkin.

INTRODUCTION: Mitochondria, situated at the center of intricate signaling networks, play crucial roles in maintaining health and driving disease progression. SFXN2, a recently identified member of the mitochondrial transporter family, is localized to the outer mitochondrial membrane and regulates several critical mitochondrial functions, including iron metabolism, heme biosynthesis, bioenergetics, and redox homeostasis. New evidence also suggests a connection between SFXN2 and mitochondrial dysfunction related human diseases such as Parkinson's disease (PD). Despite growing insights into SFXN2's roles across various mitochondrial functions, its regulation under mitochondrial dysfunction and the resulting biological consequences remains unclear. METHODS: The expression levels of SFXN2 protein were analyzed by Western blotting WB. The interaction between SFXN2 and Parkin was examined using co-immunoprecipitation and immunofluorescence assays. Furthermore, the effect of Parkin on SFXN2 ubiquitination was assessed via ubiquitination assay. Finally, RNA sequencing and flow cytometry were employed to investigate that SFXN2 regulates the apoptotic pathway. RESULTS: In this study, we identify SFXN2 as a key regulator of mitochondrial homeostasis, demonstrating that its level is tightly regulated via Parkin-mediated ubiquitination and proteasomal degradation. Under conditions of mitochondrial damage, Parkin enhances the degradation of SFXN2, and the reduction of SFXN2 contributes to apoptotic cell death. Functional studies across multiple cell lines, including HEK293, SH-SY5Y, and N2a cells, reveal that the reduction of SFXN2 exacerbates mitochondrial damage-induced apoptosis, whereas overexpression of SFXN2 exhibits an anti apoptotic effect. DISCUSSION: Our findings offer new insights into the regulation of SFXN2 in mitochondrial dysfunction through Parkin mediated ubiquitin proteasome system activity, underscoring SFXN2's potential implications in nerodegenerative diseases, particularly PD.