Development of small-molecule Kir4.2 modulators for treatment of type 2 diabetes

Type 2 Diabetes Mellitus (T2DM) imposes a substantial burden on society through increased healthcare costs, loss of productivity, and reduced quality of life. The number of diagnosed T2DM patients is projected to increase dramatically in the coming decades. Therefore, developing improved treatment strategies will be essential to lessen the economic and societal impact of T2DM. KCNJ15, which encodes the inward rectifier potassium (Kir) channel Kir4.2, was recently identified as a T2DM susceptibility gene. Kir4.2 is expressed in glucose-responsive, insulin-secreting beta-cells of the pancreas, where recent studies suggest that its up-regulation in T2DM leads to diminished glucose-induced insulin secretion. Importantly, siRNA-mediated knock-down of Kir4.2 expression in vivo increases insulin secretion and lowers blood glucose in diabetic mice. Taken together, these studies raise important questions regarding the physiology of Kir4.2 in beta cells and suggest the intriguing possibility that Kir4.2 represents a novel drug target for T2DM. There are currently no specific pharmacological modulators of Kir4.2. Therefore, the goal of this proposal is to develop, validate, and implement a high-throughput screening (HTS) assay to enable the discovery of the first small-molecule probes of Kir4.2 function. In Aim 1, the investigators will develop a thallium flux-based fluorescence assay to monitor Kir4.2 activity in a 384-well plate format. The robustness of the assay will be determined by meeting a series of performance benchmarks and running a pilot screen of 3,655 compounds in the Vanderbilt HTS center. In Aim 2, the investigators will perform a 30,000 compound screen (15,000 compounds each in funding years 1 and 2) of the Vanderbilt Institute of Chemical Biology Library. The potency and selectivity of Kir4.2 modulators will be characterized in Aim 3 using a panel of established high-throughput thallium flux assays for 9 different Kir channels. These assays dramatically shorten the time from hit discovery in a primary screen to lead compound identification and optimization. The successful outcome of the proposed work will be the development of pre-clinical tool compounds for exploring the physiology of Kir4.2 in beta cells and its therapeutic potential in T2DM.