A transient protein folding response targets aggregation in the early phase of TDP-43-mediated neurodegeneration

Abstract

Understanding the mechanisms that drive TDP-43 pathology is integral to combating amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD) and other neurodegenerative diseases. Here we generated a longitudinal quantitative proteomic map of the cortex from the cytoplasmic TDP-43 rNLS8 mouse model of ALS and FTLD, and developed a complementary open-access webtool, TDP-map (https://shiny.rcc.uq.edu.au/TDP-map/). We identified distinct protein subsets enriched for diverse biological pathways with temporal alterations in protein abundance, including increases in protein folding factors prior to disease onset. This included increased levels of DnaJ homolog subfamily B member 5, DNAJB5, which also co-localized with TDP-43 pathology in diseased human motor cortex. DNAJB5 over-expression decreased TDP-43 aggregation in cell and cortical neuron cultures, and knockout of Dnajb5 exacerbated motor impairments caused by AAV-mediated cytoplasmic TDP-43 expression in mice. Together, these findings reveal molecular mechanisms at distinct stages of ALS and FTLD progression and suggest that protein folding factors could be protective in neurodegenerative diseases.

Proteomic analysis of the TDP-43-associated insoluble fraction from NEFH-TDP-43 mouse brain suggests sustained stress granule formation, CLUH granule recruitment and impaired mitochondrial metabolism

“…Formaldehyde crosslinking and homogenization of brain tissue was adapted from previous protocols (Liu-Yesucevitz et al, 2010; San Gil et al, 2024; Sap et al, 2021). 500 µl of 0.5% formaldehyde in PBS was added to 30 mg of frozen mouse brain tissue, previously crushed under N 2 and placed on a rotating wheel for 10 mins at room temperature.…”

“…These studies identified multiple disease-related changes in biological pathways. However, these analyses were performed using soluble protein fractions (Lee et al, 2023; San Gil et al, 2024) without TDP-43 immunoprecipitation, and would therefore not accurately capture the TDP-43-associated SG proteome.…”

“…Attempts to determine the presence of TDP-43 in SG fractions isolated from tissues is limited and may lack specificity due to TDP-43 immunoprecipitation from soluble and not insoluble fractions (Montalbano et al, 2020). Proteomics analysis has been performed to observe changes in postmortem frozen motor cortex samples form ALS donors compared with healthy control samples (Lee et al, 2023) as well as longitudinal analysis in cortex samples from NEFH-TDP-43 mice (San Gil et al, 2024). These studies identified multiple disease-related changes in biological pathways.…”