Identification of potent and selective small molecule TALK-1 inhibitors that promote β-cell function.

The two-pore domain K+ (K2P) channel TALK-1 is a key regulator of β-cell electrical excitability, Ca2+ handling, and glucose-stimulated insulin secretion. KCNK16, the gene encoding TALK-1, is the most abundant β-cell K+ channel transcript and the most islet-restricted ion channel. Genetic evidence also links KCNK16 to diabetic phenotypes, including a gain-of-function polymorphism (rs1535500) that predisposes individuals to type 2 diabetes and a gain-of-function mutation (p.L114P) that causes maturity-onset diabetes of the young. Moreover, ablation of β-cell TALK-1 improves glucose homeostasis in the context of diet-induced obesity. However, it remains unclear if TALK-1 can be pharmacologically targeted to enhance β-cell function and reduce hyperglycemia in type 2 diabetes patients. Here, we identify, to our knowledge, the first selective inhibitors of TALK-1. This was accomplished with a high-throughput fluorescence-based thallium (Tl+) flux assay, which identified 286 TALK-1 inhibitors. Of these, 81 compounds selectively inhibited TALK-1 without affecting other K+ channels (ie, TALK-2, TASK-3, KATP, and hERG). One compound, VU0544194 (K2P16-i7), was selected for further evaluation based on its potency and TALK-1 selectivity. K2P16-i7 inhibited β-cell K2P currents, increased islet Ca2+ influx, enhanced endoplasmic reticulum Ca2+ storage, and augmented glucose-stimulated insulin secretion. We then identified scaffold domains of K2P16-i7 that, with specific modifications, improved potency while retaining the ability to augment endoplasmic reticulum Ca2+ stores. Together, these findings identify, to the best of our knowledge, the first selective small molecule inhibitors of TALK-1 and determine that they improve β-cell function, which could enable an islet-selective therapeutic modality for treating diabetes. SIGNIFICANCE STATEMENT: TALK-1 channels are involved in regulating glucose homeostasis and weight, making them a promising endocrine-specific target for diabetes and obesity. Here, this study identifies, to our knowledge, the first selective TALK-1 inhibitors that show efficacious regulation of islet Ca2+ handling and insulin secretion; these molecules will enable future investigation of human endocrine TALK-1 function as well as drug design.