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Development of peptides targeting TDP-43 and CK-1δ as potential amyotrophic lateral sclerosis and frontotemporal lobar degeneration therapies

University of British Columbia

The sick and dying neurons in several different neurodegenerative disorders, including Amyotrophic Lateral Sclerosis (ALS), Frontotemporal dementia (FTLD) and Perry's Syndrome, are filled with insoluble cytoplasmic aggregates of phosphorylated TAR DNA binding protein 43 (TDP-43). While the mechanisms underlying these TDP-43 proteinopathies have not been elucidated, it has been suggested that the phosphorylation of TDP-43 is an important part of the neurodegenerative cascade. In this thesis, I found that overexpression of Casein Kinase 1δ (CK-1 δ) in cells caused phosphorylation and reduced solubility of TDP-43. Proteomic studies showed that this phosphorylated TDP-43 had a different set of protein partners than did wild type TDP-43. Phosphorylated TDP-43 mainly locates in the cell's nucleus in this model, and I found that disruption of TDP-43 nuclear-cytoplasmic transport can facilitate formation of TDP-43 aggregates. While inhibiting CK-1δ may be a viable strategy for preventing the aggregates from forming this would also prevent CK-1δ from phosphorylating its many other substrates besides TDP-43. Instead, I tried a more selective strategy. I designed interference peptides derived from CK-1δ binding domains or from TDP-43 phosphorylation sites to try to selectively block the interaction of TDP-43 and CK-1δ. The peptide candidates efficiently blocked TDP-43 phosphorylation induced by CK-1δ overexpression. I further assessed the peptide mixture using both in vitro and in vivo models of cell stress and cell death. In the in vitro studies, the peptide mixture reduced Ethacrynic acid-induced TDP-43 phosphorylation and aggregation as well as cell death in both SH-SY5Y cells and in primary cultured neurons. In a mouse in vivo axotomy model, characterized by a reliable time-specific pattern of TDP-43 phosphorylation and aggregate formation, treatment with the blocking peptide mixture efficiently promoted recovery of wild type TDP-43 and phosphorylated TDP-43 solubility in ventral horn motor neurons of the lumbar spinal cord. The peptide mixture also reduced stress granule formation but did not affect HSP70 nuclear translocation. Taken together, these results suggest that blocking TDP-43 phosphorylation may be a useful therapeutic strategy for targeting aggregates that form in several neurodegenerative diseases.

Text

2022-03-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/76118

Neuroscience

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/