Abstract
The endoplasmic reticulum (ER) is responsible for folding secretory and membrane proteins, but disturbed ER proteostasis may lead to protein aggregation and subsequent cellular and clinical pathologies. Chemical chaperones have recently emerged as a potential therapeutic approach for ER stress-related diseases. Here, we identified 2-phenylimidazo[2,1-b]benzothiazole derivatives (IBTs) as chemical chaperones in a cell-based high-throughput screen. Biochemical and chemical biology approaches revealed that IBT21 directly binds to unfolded or misfolded proteins and inhibits protein aggregation. Finally, IBT21 prevented cell death caused by chemically induced ER stress and by a proteotoxin, an aggression-prone prion protein. Taken together, our data show the promise of IBTs as potent chemical chaperones that can ameliorate diseases resulting from protein aggregation under ER stress.
Highlights
Proteins are responsible for many tasks in cellular life, and having a correct three-dimensional protein structure is essential for their function
Activation of each branch of the UPR can be reported by transcriptional reporters containing endoplasmic reticulum (ER) stress response element-2 (ERSE2) (Kokame et al, 2001), unfolded protein response element (UPRE) (Yoshida et al, 2001) and amino acid response element (AARE) (Bruhat et al, 2000), which are ATF6, XBP1 and ATF4 binding sequences, respectively
To directly address whether IBT21 exerted its effects though chemical chaperone activity, we investigated the effects of IBT21 on reducing protein aggregation during ER stress
Summary
Proteins are responsible for many tasks in cellular life, and having a correct three-dimensional protein structure is essential for their function. Molecular chaperones are proteins that assist the covalent folding or unfolding of proteins and the assembly or disassembly of protein complexes. One major function of chaperones is to prevent both newly synthesized polypeptide chains and assembled subunits from aggregating into non-functional structures. The accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) is called ER stress. The cell has an adaptive system against ER stress called the unfolded protein response (UPR), which is the coordinated transcriptional upregulation of ER chaperones and folding enzymes that prevents the aggregation of unfolded and incompletely folded proteins (Mori, 2000; Walter and Ron, 2011; Han and Kaufman, 2017). Disturbance of the UPR has important pathological consequences, including diabetes, neurodegenerative disease and cancer (Hotamisligil, 2010; Martınez et al, 2018; Clarke et al, 2014)
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