Fructose-2,6-bisphosphate restores TDP-43 pathology-driven genome repair deficiency in motor neuron diseases.

TDP-43 proteinopathy is central to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). TDP-43 plays a key role in DNA double-strand break repair (DSBR), though the underlying mechanisms remain unclear. Here, we demonstrate that ALS patients' brains exhibit persistent DNA damage within transcribed genes. Mechanistically, activity of polynucleotide kinase 3'-phosphatase (PNKP), an essential DNA end-processing enzyme required for DSBR in transcribed genes, is impaired in ALS brains and TDP-43-depleted cells. Such defect stems from reduced levels of PNKP-interacting enzyme phosphofructo-2- kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) and its metabolic product fructose-2,6- bisphosphate (F2,6BP), an essential cofactor of PNKP. F2,6BP supplementation reduces cytosolic aggregation of phosphorylated and polyubiquitinated TDP-43 in patient-derived induced neurons, rescues PNKP activity in ALS/FTD brain extracts, and improves motor deficits in Drosophila TDP-43 model. Together, these findings reveal a critical link between metabolic dysregulation and genomic instability in TDP-43 pathology-associated motor neuron diseases, and underscore therapeutic potential of F2,6BP.