Transcriptional induction of the heat shock protein B8 mediates the clearance of misfolded proteins responsible for motor neuron diseases

Abstract

. We identified two compounds, colchicine and doxorubicin, that robustly up-regulated HSPB8 expression. Both colchicine and doxorubicin increased the expression of the master regulator of autophagy TFEB, the autophagy linker p62/SQSTM1 and the autophagosome component LC3. In line, both drugs counteracted the accumulation of TDP-43 and TDP-25 misfolded species responsible for motoneuronal death in sALS. Thus, analogs of colchicine and doxorubicin able to induce HSPB8 and with better safety and tolerability may result beneficial in NDs models.Different human diseases have been associated with an insufficient or an excessive intracellular response to proteotoxic stress. Proteins that lose the capability to acquire and/or to maintain the proper folding, after genetic mutations or damages in their structures (e.g.: specific amino acids modifications due to free radical exposure, etc.), become aberrantly folded or misfolded and can trigger a proteotoxic stress 1,2 . Misfolded proteins may oligomerize into aggregates that accumulate in cells. Misfolded proteins are potentially toxic by affecting several fundamental intracellular functions, either/both in their monomeric or/and in their aggregated forms, particularly in post-mitotic cells like neurons 3,4 . For these reasons, misfolded proteins are physiologically cleared from the cells by the protein quality control (PQC) system. The PQC system is composed of two main arms: the molecular chaperone, mainly represented by the heat shock proteins (HSPs) 5-7 and the degradative pathways, including the proteasome, the autophagic response and the unfolded protein response (UPR) 8,9 . A specific degradative pathway for a given misfolded protein is selected by defined class of chaperones, with the assistance of co-chaperones 5 .

HSPB8 and BAG3 cooperate to promote spatial sequestration of ubiquitinated proteins and coordinate the cellular adaptive response to proteasome insufficiency

“…Under those conditions, BAG3 and HSPB8 levels were significantly increased (siCtl+MG132, 16 h, Fig. 1A), in agreement with previous findings (23,25,53).…”

Decreased Levels of Foldase and Chaperone Proteins Are Associated with an Early-Onset Amyotrophic Lateral Sclerosis

“…A Phase II clinical trial in ALS patients has shown that the drug is safe and well tolerated (Cudkowicz et al, 2008) and is now under investigation in a PhaseII/III clinical trial in SOD1 positive familial ALS patients (ClinicalTrials.gov identifier: NCT00706147). Colchicine, a FDA-approved drug that was identified by a high-throughput screening as enhancer of the expression of HSPB8, a key player of the protein quality control system, has demonstrated to facilitate the removal of TDP-43 aggregates by autophagy (Crippa et al, 2016).…”

Small molecule modulation of a redox-sensitive stress granule protein dissolves stress granules with beneficial outcomes for familial amyotrophic lateral sclerosis models

“…As lipoamide and lipoic acid had a large effect on FUS aggregation in vitro we used a filter-trap retention assay (in which aggregated protein from cell lysate tends to be retained on a membrane) 52 to test whether lipoamide had a beneficial effect on spontaneous aggregation of wild-type or P525L FUS GFP in iPSCs ( Figure S4). Both cell lines had evidence for some FUS aggregation, which was reduced following treatment with lipoamide ( Figure S4B).…”

“…Western blots were performed using standard methods and the following antibodies: Mouse anti-FUS (AMAB90549 Sigma Aldrich, 1:500 dilution), rabbit anti-GFP (sc-8334 Santa Cruz, 1:400) or rabbit anti-GAPDH (2118S NEB, 1:5000) primary antibody with horseradish peroxidase-conjugated anti-mouse or anti-rabbit (Dianova 1:10,000) secondary antibodies. The filter retardation assay for intracellular FUS aggregates was performed as previously described 52 . Briefly, protein extracts were loaded on 0.2 μm cellulose acetate membrane then subject to microfiltration, leaving aggregated protein on the membrane.…”