Notes: The researchers demonstrate use of the NanoBRET™ Target Engagement Intracellular Kinase Assays to report on kinase target engagement in real time for quantitative inhibitor profiling of 178 kinases, including over 40 integral membrane receptors. (4936)

Notes: The authors used bioluminescence resonance energy transfer (BRET) to test the ability of a bromodomain 9 ligand to disrupt binding to histone. HEK 293 cells were cotransfected with a histone H3.3-HaloTag® fusion vector and either NanoLuc®-BRD9 bromodomain or NanoLuc®-full-length BRD4 fusion vector. After 24 hours, the transfected cells were trypsinized, diluted in phenol red-free DMEM with or without 10nM of HaloTag® NanoBRET™ 618 Ligand and dispensed into a 96-well plate. One of two potential BRD-disrupting compounds, 7d or 11, was adding to a final concentration of 0.005–33μM, cells were incubated for 18 hours and NanoBRET™ Nano-Glo® Substrate (final concentration 10µM) was added. Fluorescence was measured and a corrected BRET ratio calculated. Cytotoxicity was assessed after the NanoBRET™ assay by incubating the cells with the CellTiter-Glo® Reagent for 30 minutes and measuring luminescence. To examine histone H3.3 localization, HEK 293 cells were transfected with the histone H3.3-HaloTag® fusion vector using FuGENE® HD Transfection Reagent. After 24 hours, cells were labeled with 5μM HaloTag® TMR ligand for 15 minutes before washing with complete medium, incubated for 30 minutes and imaged with a confocal microscope. (4568)

Notes: These authors studied the interactions between G-protein coupled receptors (GPCRs)  and 13 different G-proteins using a NanoBRET assay. NanoBRET assays were performed using protein partners labeled with NanoLuc luciferase or Venus yellow fluorescent protein. The improvement in signal-to-noise ratio achieved using the NanoBRET method enabled resolution of signals from previously intractable G-proteins and GPCRs. The authors demonstrated that GPCRs engage multiple G-proteins with distinct patterns of activity or “fingerprints”. This differential engagement of multiple target G-proteins was revealed by quantitative analysis of G-protein activation kinetics.  (4588)

Notes: To characterize the effectiveness of LP99, a potential bromodomain inhibitor, BRD7 and BRD9 were fused with NanoLuc® luciferase and histones H3.3 and H4 were fused with HaloTag® protein for use in BRET. The two proteins were expressed in HEK 293 cells, and the histone-HaloTag® fusions were fluorescently labeled with the HaloTag® NanoBRET™ 618 Ligand. Once the NanoBRET™ Nano-Glo® Substrate was added, NanoBRET™ ratios were assessed in the presence of varying concentrations of LP99. (4567)

Notes: To investigate whether protein conformation of Rabin8 plays a role in autoinhibition, the authors created a Rabin8 fusion construct with NanoLuc® luciferase at the N terminus and HaloTag® protein at the C terminus so that they can use BRET as an indication of protein conformation. A t-SRARE protein, syntaxin-4 (STX4), which is known to have a closed conformation, was constructed with the same NanoLuc® luciferase-STX4-HaloTag® protein configuration for use as a positive control. Both the control STX4 protein and Rabin8 were expressed in E. coli, the NanoBRET™ Nano-Glo® Substrate added and fluorescence measured. As a negative control, TEV protease was used to cleave the HaloTag® sequence from the protein fusions, eliminating the NanoBRET™ signal. NanoBRET™ signals were determined from experiments comparing Rabin8 with a gain-of-function Rabin8 mutant, exposing Rabin8 to constitutively active ERK2 or a kinase-dead ERK2 and assessing wildtype Rabin8 versus Rabin8-4D, where the aspartates acted as phosphorylation mimics. (4566)