| Assay Method Information | |
| | VHL HEK-293 BRET Assay |
| Description: | The VHL NanoBRET Target Engagement Assay analyzes the apparent affinity of test compounds for VHL in cells by competitive displacement of a VHL NanoBRET tracer reversibly bound to a NanoLuc VHL fusion protein stably expressed in the cells.Test compounds were transferred to the assay plate (384 Well White Non-Binding Corning Assay Plates (Corning-3574)) using an Echo 555 Liquid Handler (Labcyte) in 2.5 nL increments and, as appropriate, intermediate stock concentrations of compounds, in order to prepare a titration series. 50 nL of control compound (10 mM; parental unlabeled VHL antagonist; see structure below) and 50 nL of DMSO (negative control) were dispensed into the appropriate control wells. DMSO was backfilled to a final volume of 50 nL as required. 50 nl per well of 1 mM VHL NanoBRET Tracer in DMSO (NanoBRET Tracer-PEG2-590 (see structure below)) was transferred into each well using an Echo 555 (ultimately yielding a final concentration of 1 uM). HEK 293 RT VHL-NanoLuc stable cells were cultured in DMEM High Glucose with Pyruvate, 10% fetal bovine serum, 2 mg/mL of Geneticin Selective Antibiotic (50 mg/ml) and 2 mM HEPES (1 M). Cells were seeded in Opti-MEM (Life Technologies-11058-021), 1.7×105 cells/mL, 40 μl per well into the assay plate, centrifuged at 500 rpm for 30 seconds and incubated for 2 hours. Max Signal control wells consisted of DMSO only treated wells. Minimum Signal control wells contained of 10 uM parental unlabeled VHL antagonist (control compound see structure below). 3× Complete Substrate plus Inhibitor Solution was prepared in Opti-MEM (consists of a 1:166 dilution of NanoBRET Nano-Glo Substrate plus a 1:500 dilution of Extracellular NanoLuc Inhibitor in Opti-MEM), and 20 ul was dispensed into each well of the 384-well plate and centrifuged at 1000 rpm for 1 minute, then incubated for 2 minutes at room temperature. Background Signal control wells were prepared without tracer for background correction steps.Plates were read using a PerkinElmer Envision Reader (model 2104-0020) equipped with Luminescence option (Mirror: BRET2 Enh (PE Barcode 659), Emission Filter: Omega 610LP (Barcode 504), 2nd Emission Filter: Umbelliferone 460 (Barcode 207), Measurement height: 6.5 mm, Measurement time: 1 s). The raw BRET ratio values were calculated by dividing the acceptor emission value (610 nm) by the donor emission value (460 nm) for each sample. To correct for background, the BRET ratio in the absence of tracer (average of no-tracer control samples) was subtracted from the BRET ratio of each sample. Raw BRET units were converted to milliBRET units (mBU) by multiplying each raw BRET value by 1,000. The normalized NanoBRET signal was calculated relative to the Max Signal control wells (DMSO treated control wells) and the Minimum Signal control wells. Percentage inhibition was calculated relative to the Minimum Signal control and Maximum Signal control wells. IC50 values were derived by four parameter curve fitting using the Robust method. |
| Affinity data for this assay | |
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