Investigating the impact of p97 mutation in Amyotrophic Lateral Sclerosis

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Protein homeostasis decline is a significant contributor to the development of Amyotrophic Lateral Sclerosis (ALS) and other neurodegenerative disorders. With an ever-expanding aging population and no reliable therapies, these devastating diseases will place a significant burden on health care in the coming decades. The p97 AAA-ATPase is a ubiquitin-selective unfoldase that has critical roles in protein quality control. Dedicated adaptor proteins target p97 to ubiquitylated substrates and thereby impart specificity to this abundant enzyme. Mutations in p97 cause familial ALS and are reported to impede p97 association with certain adaptors and impair ER and mitochondria associated quality control suggesting inadequate targeting to these organelles. However, the impact of p97 mutation on its interactome and ubiquitylated substrates has not been studied systematically in cell types impacted in disease, namely motor neurons and skeletal muscle. Here, we will establish an induced pluripotent stem cell (iPSC)-based model of motor neuron disease caused by distinct p97 mutations. We will use this system to: (1) Investigate how mutant p97 remodels the motor neuron and skeletal muscle proteome and physiology. Ubiquitylated substrates of p97 will be identified using quantitative proteomics in each cell type. (2) Examine the impact of p97 mutation on known protein quality control pathways in motor neurons skeletal muscle cells. Our studies will provide the first model of ALS caused by p97 mutation and will provide mechanistic insight into how p97 mutation causes motor neuron and/or skeletal muscle demise. We anticipate our cell-based model may be used in the future for small molecule screens to identify lead molecules for therapy development. Given the prevalence of p97 mutation, we anticipate these studies will have broad relevance to other in neurodegenerative diseases.