TDP-43-driven alternative splicing of UQCRC2 modulates mitochondrial bioenergetics.

TAR DNA-binding protein 43 (TDP-43) is a nuclear RNA-binding protein. It has emerged as a key regulator of RNA processing, such as alternative splicing events, which are essential for cellular homeostasis. The mislocalization and aggregation of TDP-43 are closely associated with mitochondrial dysfunction. However, the mechanisms by which the formation TDP-43 contributes to mitochondrial impairment remain poorly understood. In this study, we confirmed that the TDP-43 loss leads to dramatic alterations in mitochondrial morphology and a significant reduction in respiratory capacity. Further analysis of oxidative phosphorylation (OXPHOS) complex assembly revealed a selective disruption of complex III activity. Notably, the core complex III subunit UQCRC2 was significantly decreased as long as TDP-43 was knocked down. The transcript analysis showed that the loss of TDP-43 results in aberrant alternative splicing of the nuclear-encoded UQCRC2 transcript. In parallel, this mis-splicing event was consistently observed in both dividing cells, including HEK293T, and in the neuroblastoma cell line SH-SY5Y, suggesting that TDP-43-mediated regulation of UQCRC2 splicing can be potentially conserved across a wide range of cell types. These findings indicate a novel role for TDP-43 in maintaining mitochondrial integrity via regulation of UQCRC2 expression and splicing, providing mechanistic insight into how dysregulated RNA processing contributes to mitochondrial bioenergetic deficits.