Deubiquitinase USP19 in TDP-43 pathogenesis. - The RNA-binding nuclear protein TDP-43 mislocalizes to the cytoplasm and aggregates in Frontotemporal lobar degeneration (FTLD-TDP variant), Amyotrophic Lateral Sclerosis (ALS), and >50% of late-onset Alzheimer’s disease (AD). Abnormal TDP-43 mislocalization and accumulation is associated with endoplasmic reticulum (ER) stress, synaptic dysfunction, and cognitive and motor impairments. While TDP-43 undergoes different post-translational modifications including phosphorylation, poly ADP-ribosylation, oxidation, acetylation, sumoylation, and ubiquitination, ubiquitination is a final key modification required for the turnover of TDP-43 via the ubiquitin-proteasome system and autophagy-lysosome pathways. TDP-43 is ubiquitinated by E3 ligases Parkin, PJA1, and Znf179. However, the role of deubiquitinases (DUBs) in the regulation of TDP-43 function, turnover, proteinopathy, and toxicity is poorly understood. The human genome encodes ~90 DUBs. Ubiquitin specific peptidases (USPs) are the largest family of DUBs comprising ~50 members in humans. Of these, 27 are expressed in the CNS. Our results from an unbiased screen of CNS-expressed DUBs identified USP19 as a major TDP-43 DUB, a positive regulator of TDP-43 stability, and a promising candidate for further study. Specifically, preliminary studies indicate that USP19, a DUB elevated during aging and in brains of FTLD-TDP patients, acts to increase TDP-43 stability/aggregation and participates in TDP-43-induced ER stress. By taking advantage of mouse models and human postmortem tissues together with molecular, cell biological, imaging, biochemical, proteomics, electrophysiological, behavioral, viral, histochemical, and recombinant protein toolsets, this proposal will 1. validate the role of USP19 in TDP-43 pathogenesis and associated phenotypes vivo, and 2. determine the mechanistic basis of USP19 in TDP-43 deubiquitination, stability, aggregation, and toxicity in genetically modified neurons and in vitro systems. Successful conclusion of these studies will determine the significant contribution of USP19 and its DUB activity to TDP-43 pathogenesis in humans and mice. Moreover, these results will provide novel mechanistic insights to USP19 DUB activity in concert with TDP-43 in ER stress and neurotoxicity. Together, these studies will enable the pursuit of a potential therapeutic direction of targeting USP19-mediated mechanisms to mitigate TDP-43 pathology and toxicity.
