The Ku80-p53-SIRT1 axis in DNA damage response contributes to sporadic and familial ALS and FTD.

Although TDP-43 pathology is found in most sporadic and familial ALS and FTD cases, other shared pathogenic mechanisms remain largely unknown. Here we show that SIRT1 levels are decreased and acetylated p53 levels are increased in iPSC-derived neurons from sALS patients and with the FTD3-causing CHMP2B mutation. Ectopic expression of SIRT1 in these patient neurons rescues neurodegeneration and reduces acetylated p53 levels. DNA damage is elevated in both sALS and FTD3 neurons, leading to increased phosphorylation of p53 at Serine 15 and elevated levels of Ku80. Knockdown of either p53 or Ku80 rescues neurodegeneration and increases SIRT1 levels in these neurons. Moreover, ectopic expression of SIRT1 or genetic knockdown of either p53 or Ku80 suppresses retinal neurodegeneration caused by FTD3-associated mutant CHMP2B protein in an in vivo Drosophila model. These findings identify a dysregulated SIRT1-p53 feedback loop as a common pathogenic mechanism and promising therapeutic target in both sporadic and familial ALS/FTD.