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Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that results from many diverse genetic causes. Although therapeutics specifically targeting known causal mutations may rescue individual types of ALS, these approaches cannot treat most cases since they have unknown genetic etiology. Thus, there is a pressing need for therapeutic strategies that rescue multiple forms of ALS. Here, we show that pharmacological inhibition of PIKFYVE kinase activates an unconventional protein clearance mechanism involving exocytosis of aggregation-prone proteins. Reducing PIKFYVE activity ameliorates ALS pathology and extends survival of animal models and patient-derived motor neurons representing diverse forms of ALS including C9ORF72, TARDBP, FUS, and sporadic. These findings highlight a potential approach for mitigating ALS pathogenesis that does not require stimulating macroautophagy or the ubiquitin-proteosome system., Competing Interests: Declaration of interests J.K.I. and S.-T.A. are co-founders of AcuraStem, Inc. S.-T.A., W.-H.C., S.M., and S.H. are employees of AcuraStem, Inc. J.K.I. is a co-founder of Modulo Bio, serves on the scientific advisory boards of AcuraStem, Spinogenix, Synapticure, and Vesalius Therapeutics, and is employed at BioMarin Pharmaceutical. B.V.Z. is a co-founder of ZZ Biotech and chairman of its scientific advisory board. J.A.P. is a co-founder of Modelis. F.-B.G. receives research funding from Stealth BioTherapeutics., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Disruption in copper homeostasis causes a number of cognitive and motor deficits. Wilson's disease and Menkes disease are neurodevelopmental disorders resulting from mutations in the copper transporters ATP7A and ATP7B, with ATP7A mutations also causing occipital horn syndrome, and distal motor neuropathy. A 65 year old male presenting with brachial amyotrophic diplegia and diagnosed with amyotrophic lateral sclerosis (ALS) was found to harbor a p.Met1311Val (M1311V) substitution variant in ATP7A. ALS is a fatal neurodegenerative disease associated with progressive muscle weakness, synaptic deficits and degeneration of upper and lower motor neurons. To investigate the potential contribution of the ATP7A M1311V variant to neurodegeneration, we obtained and characterized both patient-derived fibroblasts and patient-derived induced pluripotent stem cells differentiated into motor neurons (iPSC-MNs), and compared them to control cell lines. We found reduced localization of ATP7A M1311V to the trans-Golgi network (TGN) at basal copper levels in patient-derived fibroblasts and iPSC-MNs. In addition, redistribution of ATP7A M1311V out of the TGN in response to increased extracellular copper was defective in patient fibroblasts. This manifested in enhanced intracellular copper accumulation and reduced survival of ATP7A M1311V fibroblasts. iPSC-MNs harboring the ATP7A M1311V variant showed decreased dendritic complexity, aberrant spontaneous firing, and decreased survival. Finally, expression of the ATP7A M1311V variant in Drosophila motor neurons resulted in motor deficits. Apilimod, a drug that targets vesicular transport and recently shown to enhance survival of C9orf72-ALS/FTD iPSC-MNs, also increased survival of ATP7A M1311V iPSC-MNs and reduced motor deficits in Drosophila expressing ATP7A M1311V . Taken together, these observations suggest that ATP7A M1311V negatively impacts its role as a copper transporter and impairs several aspects of motor neuron function and morphology., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)