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

Abstract

Endoplasmic reticulum (ER) plays a critical role in protein, lipid and glucose metabolism, as well as cellular calcium homeostasis and signaling. Perturbation of ER function and chronic ER stress is associated with many pathologies ranging from diabetes to neurodegenerative diseases, cancer and inflammation. While targeting the ER offers 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 the protein folding capacity of ER. With these quantitative platforms, we characterized a small molecule compound, azoromide, that improves ER protein folding ability and activates ER chaperone capacity to protect cells against ER stress in multiple systems. Remarkably, this compound also exhibits potent anti-diabetic efficacy in two independent mouse models of obesity by improving insulin sensitivity and beta cell function. Taken together, these results demonstrate the utility of this functional, phenotypic assay platform for ER-targeted drug discovery, and provide proof-of-principle that specific ER modulators can be potential drug candidates against type 2 diabetes.

Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions

“…The use of these drugs in combination with other therapies such as incretins may exert beneficial effects on the β-cell phenotype (Busch & Kane 2017, Kaneto et al 2017). The potential combination with antioxidants such as GPX mimetics and/or chemical chaperones such as the recently identified small-molecule azoramide (Fu et al 2015) merits further experimental and clinical testing.…”

A Reevaluation of the Role of the Unfolded Protein Response in Islet Dysfunction: Maladaptation or a Failure to Adapt?

“…Conversely a reduction in BiP expression as a result of C/EBPb-mediated downregulation of ATF6 is associated with diabetes (43). Moreover, administration of pharmacological chaperones such as tauroursodeoxycholic acid, 4-phenylbutyrate (PBA), and the more recently discovered azoramide can restore rodent islet function both in vitro and in vivo (32,36,40,(44)(45)(46). In humans, PBA has also been shown to partially alleviate lipid-induced b-cell dysfunction (47).…”

“…Another important question is whether it is possible to intervene therapeutically to promote further adaptation. Clearly, increasing ER folding capacity through the administration of pharmacological chaperones in rodent models of diabetes has beneficial effects (32,36,40,(44)(45)(46)78), and there is some evidence that it is also beneficial in humans (47). Thus, the identification and an evaluation of the efficacy of drugs that increase ER folding capacity and/or reduce oxidation stress is an important avenue of pharmacological exploration.…”

Spoxazomicin D and Oxachelin C, Potent Neuroprotective Carboxamides from the Appalachian Coal Fire-Associated Isolate Streptomyces sp. RM-14-6

“…30 Evaluation of the cumulative set of metabolites isolated from Streptomyces sp. RM-14-6 in this assay revealed the polyether antibiotics lenoremycin ( 9 ; also known as Ro 21-6150 49 ) and lenoremycin sodium salt ( 10 ) as potent modulators of protein folding capacity (EC 50 = 38 and 109 nM, respectively) (Figures S1 and S2 and Table S1).…”