Phenotypic assays identify azoramide as a small-molecule modulator of the unfolded protein response with antidiabetic activity

New assays that measure endoplasmic reticulum (ER) function and protein folding identify a small molecule, azoramide, that exerts antidiabetic effects. Speed, specificity, and versatility Selecting versatile targets is one way to speed therapeutic research and development (R&D). Here, Fu et al. design two high-throughput assays that test divergent endoplasmic reticulum (ER) functions. The authors then screen for small molecules that boost ER activity and pinpoint a candidate compound that exhibits antidiabetic activity in mouse models of obesity. Disruption in ER function and chronic ER stress are associated with pathologies that range from diabetes and neurodegenerative diseases to cancer and inflammation. In fact, drugs that target the ER have shown therapeutic promise in preclinical models of obesity and other pathologies but limitations of pharmacological properties have blocked effective clinical translation. The authors developed two screening systems, one that specifically measures free chaperone content and another that assesses ER protein-folding capacity. With their assay systems, they identified and characterized a small molecule, azoramide, that improved ER protein folding and elevated ER chaperone capacity, which together protected cells against ER stress. Azoramide displayed anti-diabetic efficacy in two mouse models of obesity by improving insulin sensitivity and pancreatic beta cell function. Although these screening platforms are speedy and specific, they can’t transform therapeutic R&D into a process swift enough to ready you for swimsuit season. But azoramide does offer proof-of-principle for the hypothesis that ER modulators may be identified with phenotypic screens and serve as drug candidates for diseases that display aberrant ER function. The endoplasmic reticulum (ER) plays a critical role in protein, lipid, and glucose metabolism as well as cellular calcium signaling and homeostasis. Perturbation of ER function and chronic ER stress are associated with many pathologies ranging from diabetes and neurodegenerative diseases to cancer and inflammation. Although ER targeting shows therapeutic promise in preclinical models of obesity and other pathologies, the available chemical entities generally lack the specificity and other pharmacological properties required for effective clinical translation. To overcome these challenges and identify new potential therapeutic candidates, we first designed and chemically and genetically validated two high-throughput functional screening systems that independently measure the free chaperone content and protein-folding capacity of the ER. With these quantitative platforms, we characterized a small-molecule compound, azoramide, that improves ER protein-folding ability and activates ER chaperone capacity to protect cells against ER stress in multiple systems. This compound also exhibited potent antidiabetic efficacy in two independent mouse models of obesity by improving insulin sensitivity and pancreatic β cell function. Together, these results demonstrate the utility of this functional, phenotypic assay platform for ER-targeted drug discovery and provide proof of principle for the notion that specific ER modulators can be potential drug candidates for type 2 diabetes.