Structure-Activity Relationships, Pharmacokinetics, and Pharmacodynamics of the Kir6.2/SUR1-Specific Channel Opener VU0071063

Abstract

Glucose-stimulated insulin secretion from pancreatic b-cells is controlled by ATP-regulated potassium (K ATP) channels composed of Kir6.2 and sulfonylurea receptor 1 (SUR1) subunits. The K ATP channel-opener diazoxide is FDA-approved for treating hyperinsulinism and hypoglycemia but suffers from off-target effects on vascular K ATP channels and other ion channels. The development of more specific openers would provide critically needed tool compounds for probing the therapeutic potential of Kir6.2/SUR1 activation. Here, we characterize a novel scaffold activator of Kir6.2/SUR1 that our group recently discovered in a high-throughput screen. Optimization efforts with medicinal chemistry identified key structural elements that are essential for VU0071063-dependent opening of Kir6.2/SUR1. VU0071063 has no effects on heterologously expressed Kir6.1/SUR2B channels or ductus arteriole tone, indicating it does not open vascular K ATP channels. VU0071063 induces hyperpolarization of b-cell membrane potential and inhibits insulin secretion more potently than diazoxide. VU0071063 exhibits metabolic and pharmacokinetic properties that are favorable for an in vivo probe and is brain penetrant. Administration of VU0071063 inhibits glucose-stimulated insulin secretion and glucose-lowering in mice. Taken together, these studies indicate that VU0071063 is a more potent and specific opener of Kir6.2/SUR1 than diazoxide and should be useful as an in vitro and in vivo tool compound for investigating the therapeutic potential of Kir6.2/SUR1 expressed in the pancreas and brain.

The LRRC8 volume‐regulated anion channel inhibitor, DCPIB, inhibits mitochondrial respiration independently of the channel

“…Channel activity was measured using a thallium flux assay that reports the inwardly directed movement of thallium into T‐REx‐HEK‐293 cells heterologously expressing Kir6.2/SUR1 (Kharade, Nichols, & Denton, ). As shown in Figure , treatment of T‐REx‐HEK‐293‐Kir6.2/SUR1 cells with the SUR1‐specific activator, VU0071063 (Kharade et al, ; Raphemot et al, ) (positive control), or DCPIB, led to an increase in thallium flux in HEK‐293‐Kir6.2/SUR1 cells. Taken together, these data indicate that DCPIB suppresses mitochondrial respiration and ATP synthesis in HAP‐1 and HEK‐293 cells independently of LRRC8A‐dependent VRAC.…”

“…After 8‐min incubation period, 10 μl/well thallium stimulus buffer (125 mM NaHCO 3 , 1.8 mM CaSO 4 , 1 mM MgSO 4 , 5 mM glucose, 1.8 mM Tl 2 SO 4 , and 10 mM HEPES, pH 7.4) was added and data was collected for another 4 min. VU0071063 (Kharade et al, ; Raphemot et al, ) (positive control) and DCPIB were serially diluted threefold in DMSO and then dissolved in assay buffer to obtain 11‐point CRCs. The data acquisition and analysis were performed using Waveguide (WaveFront Biosciences) and Microsoft excel.…”

Adaptive short‐term associative conditioning in the pancreatic β‐cell

“…When carbachol was applied together with glucose and diazoxide, TPS was not induced. Since diazoxide does not prevent glucose intake or metabolization (Aizawa et al, 1994;Gembal, Gilon, & Henquin, 1992;Kharade et al, 2019), these data reveal the need for the requirement of membrane depolarization and calcium entry to induce TPS. Tolbutamide, an antidiabetic drug, acts in a manner opposite to diazoxide, blocking ATP-K channels, depolarizing cells, and inducing the opening of calcium channels and insulin secretion even in the absence of glucose.…”

Screening Technologies for Inward Rectifier Potassium Channels: Discovery of New Blockers and Activators

“…This same group of investigators identified VU0071063 (IC 50 = 7 µM) as an activator of Kir/SUR1 channels. 86 Importantly, VU0071063 was more potent than the KCO diazoxide in activating the Kir6.2/SUR1 channel and inhibited glucose-dependent insulin release when tested in mouse pancreatic islet cells at a concentration of 10 µM.…”

“…Opening of Kir channels allows Tl + to enter into the cell and bind to a Tl + -sensitive fluorescent dye, causing a fluorescent signal. In Rb + flux experiments (not shown), Rb + is loaded into the cells and the efflux of Rb + into the supernatant is measured with AAS or a scintillation counter ( 86 Rb + ). ( C ) Electrophysiological methods include the traditional whole-cell patch clamp technique (left panel) and newer APC systems (right panel).…”