Neuroprotection through Excitability and mTOR Required in ALS Motoneurons to Delay Disease and Extend Survival

Delaying clinical disease onset would greatly reduce neurodegenerative disease burden, but the mechanisms influencing early preclinical progression are poorly understood. Here, we show that in mouse models of familial motoneuron (MN) disease, SOD1 mutants specifically render vulnerable MNs dependent on endogenous neuroprotection signaling involving excitability and mammalian target of rapamycin (mTOR). The most vulnerable low-excitability FF MNs already exhibited evidence of pathology and endogenous neuroprotection recruitment early postnatally. Enhancing MN excitability promoted MN neuroprotection and reversed misfolded SOD1 (misfSOD1) accumulation and MN pathology, whereas reducing MN excitability augmented misfSOD1 accumulation and accelerated disease. Inhibiting metabotropic cholinergic signaling onto MNs reduced ER stress, but enhanced misfSOD1 accumulation and prevented mTOR activation in alpha-MNs. Modulating excitability and/or alpha-MN mTOR activity had comparable effects on the progression rates of motor dysfunction, denervation, and death. Therefore, excitability and mTOR are key endogenous neuroprotection mechanisms in motoneurons to counteract clinically important disease progression in ALS. •A growing excitability signaling deficit in motoneurons drives disease in ALS mice•Enhancing motoneuron excitability provides neuroprotection to FALS motoneurons•Metabotropic cholinergic signaling provides neuroprotection through mTOR•Enhancing mTOR activation while reducing ER stress delays disease progression Saxena et al. show that in mouse models of familial motoneuron (MN) disease, disease-associated superoxide dismutase 1 (SOD1) mutants render vulnerable motoneurons dependent on endogenous neuroprotection involving excitability and mammalian target of Rapamycin (mTOR). Enhancing excitability signaling in motoneurons counteracts clinically important disease progression.