Pharmacologic ATF6 activating compounds are metabolically activated to selectively modify endoplasmic reticulum proteins.

Abstract

Pharmacologic arm-selective unfolded protein response (UPR) signaling pathway activation is emerging as a promising strategy to ameliorate imbalances in endoplasmic reticulum (ER) proteostasis implicated in diverse diseases. The small molecule <i>N-</i>(2-hydroxy-5-methylphenyl)-3-phenylpropanamide (<b>147</b>) was previously identified (<xref ref-type="bibr" rid="bib35">Plate et al., 2016</xref>) to preferentially activate the ATF6 arm of the UPR, promoting protective remodeling of the ER proteostasis network. Here we show that <b>147</b>-dependent ATF6 activation requires metabolic oxidation to form an electrophile that preferentially reacts with ER proteins. Proteins covalently modified by <b>147</b> include protein disulfide isomerases (PDIs), known to regulate ATF6 activation. Genetic depletion of PDIs perturbs <b>147</b>-dependent induction of the ATF6-target gene, <i>BiP</i>, implicating covalent modifications of PDIs in the preferential activation of ATF6 afforded by treatment with <b>147</b>. Thus, <b>147</b> is a pro-drug that preferentially activates ATF6 signaling through a mechanism involving localized metabolic activation and selective covalent modification of ER resident proteins that regulate ATF6 activity.