Notes: This review delves into the drug discovery pipeline, focusing on both phenotypic drug discovery (PDD) and target-based drug discovery (TDD) and the importance of experiments which determine the mechanism of action (MOA) of drugs. NanoBRET is highlighted as a highly specific assay for the measurement of target interaction. Specifically, the precise tagging of a target greatly minimizes assay cross-talk. (5122)

Notes: Determining target engagement of potential therapeutics and their target protein is commonly assessed through Thermal Shift Assays (TSA). Cell-based TSA (CETSA) now provide a more physiologically relevant information on target engagement however, these assays require use of antibodies which selectively identify the target protein and commonly have problems with reproducibility. The NanoLuc^® luciferase thermal shift assay (NaLTSA) uses NanoLuc^® luciferase activity to measure the remaining soluble fraction of the target protein making it a simplified procedure with higher reproducibility. (5055)

Notes: Cyclin G associated kinase (GAK) is a central regulator of viral and bacterial host cell entry. The synthesis and characterization of selective and potent GAK inhibitors is described. Inhibitors were assessed for ability to compete for GAK binding using the NanoBRET Target Engagement system. Briefly, a BRET signal was observed with the NanoLuc-GAK fusion in the presence of a red-shifted dye specific to the GAK ATP binding site. Upon treatment with GAK inhibitors, the dye was competed away, and a loss of BRET signal was observed. (5130)

Notes: This review mentions, under kinome-wide techniques, the NanoBRET™ assay for measuring the cellular target engagement across 178 members of a kinome using a technique involving competition between a compound of interest and a reversible cell-permeable energy transfer probe for binding to NanoLuc-tagged kinase in live cells. The authors note that, with the assay's fluorescent readout, it is amenable to higher throughput than mass spec-based techniques. (4964)

Notes: The authors use Promega HiBiT and NanoBRET™ technologies to monitor PROTAC-mediated degradation. (5081)

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 p300/CBP-associate factor (PCAF) interacts with histone H3.3 through the Brd domain and is dysregulated in multiple disease states. Here, the co-crystal structure and biochemical analysis of a novel PCAF inhibitor, L-45, is presented. The disruption of the histone H3.3-PCAF interaction is monitored using the NanoBRET Target Engagement assay. Additionally, L45 has low cytotoxicity and good cell-permeability. (5123)

Notes: Synthesized library of stable peptides designed to inhibit interaction of P53 and MDM2, peptides that often have issues with cellular permeability. Used NanoBRET™ protein:protein interaction technology to assay effectiveness to disrupt the interaction in a live-cell assay. (4926)

Notes: Activation of Notch isoforms via histone deacetylase inhibitors (HDACi) has been shown to suppress neuroendocrine (NE) cancers. Here, a novel HDACi called thailandepsin A (TDP-A) was characterized and shown to induce cell cycle arrest and apoptosis. The NanoBRET Target Engagement system was used to determine TDP-A binding to HDAC1. TT cells expressing an HDAC1-NanoLuc fusion were treated with TDP-A and competed HDAC tracer compound to determine in vivo binding affinity.  (5131)

Notes: The presence of methyl-cytosine binding domain (MBD) containing proteins and ability to remodel methylated chromatin was investigate in sponges. Specifically, the sponge MBD2 and GATAD2A protein interaction was monitored in cells using the NanoBRET™ Protein-Protein Interaction System. Multiple coiled-coil fusion constructs were tested to determine optimal signal intensity. Interestingly, while DNA methylation was observed in sponges, this interaction was much lower affinity than in vertebrate organisms. (5057)

Notes: Modified antisense oligonucleotides (ASOs) show increased delivery and stability in cells, however these modifications have off-target effects. Localization of ASOs to cytoplasmic ribonucleoprotein (RNP) granules is observed to be mediated by RNA binding proteins, FUS and PSF. These interactions are further investigated using the NanoBRET™ Protein-Protein Interaction System. NanoLuc^® tagged protein is produced using an in vitro transcription and translation system, purified, and bound to an acceptor oligonucleotide (AlexaFluor594-ASO). Various backbone and 2′ ASO modifications were screened for interaction with FUS truncations to determine the interaction domain. (5061)

Notes: PRDM14 is dysregulated in a variety of cancers, including breast and pancreatic cancer, and overexpression leads to stem-cell-like phenotypes associated with aggressive tumors. Here, PRDM14 interacting proteins are identified using the HaloTag^® Mammalian Pull-down System. The interactions of PRDM14 and glucoseregulated protein 78 (GRP78) and heat shock protein 90-a (HSP90a) were validated in vivo with the NanoBRET™ assay. (5053)

Notes: Vascular endothelial growth factor (VEGF) receptor interactions are observed using the NanoBRET™ Protein-Protein Interaction System. A novel method of labeling VEGF at a single N-terminal cysteine (TMR) to maintain full activity is presented. NanoLuc^®-VEGFR2 and VEGF-TMR are used in conjunction to monitor an interaction and internalization into intracellular endosomes. The effect of receptor tyrosine kinase inhibitors such as Cediranib and vandetanib on internalization in living cells is assessed. (5060)

Notes: Adenomatous polyposis coli protein (APC) is shown to directly interact with HIV-1 Gag protein to stimulate Gag multimerization and spread of viral particles. Direct measurements of the Gag-Gag protein interaction were measured using the NanoBRET™ system. HeLa cells were co-transfected with Gag-HaloTag^® and Gag-NanoLuc^® expression vectors and BRET signal was monitored after 24 hours. ADC knockdown displayed a substantial decrease in viral production and Gag-Gag interaction. Together, the authors show ADC regulates Gag localization to the PM and viral packaging. (5058)

Notes: G protein coupled receptor (GPCR) oligomerization and protein interaction has been commonly investigated using bioluminescence resonance energy transfer (BRET). The need for exogenous expression of fusion proteins has been a short coming of the BRET assay. Here CRISPR/Cas9 mediated homology directed repair was used to generate protein-NanoLuc^® fusions under endogenous expression. The GPCR- β-arrestin2 interaction serves as a model of this system, where interaction and internalization are monitored under conditions where the donor luciferase endogenously expressed. (5059)

Notes: Oligomerization of the glucose transporter (GLUT1) within this plasma membrane was assessed using the NanoBRET™ system. When expressed at high levels, GLUT1 has been shown to form tetrameric complexes with higher transport efficiency. Theoretical NanoBRET™ efficiency was determined for a variety of fluorescent protein acceptors and experiments were performed with mCherry as the NanoBRET™ acceptor. GLUT1 was shown to form a range of higher order complexes in live cells. Flow cytometry and immunoblotting were used in parallel to estimate GLUT1 density in cells. (5054)

Notes: Agonist antibodies targeting T cells and other immune cells to simulate immune activation have shown to be promising for cancer therapeutics. Here, the NanoBRET™ Protein-Protein Interaction Assay was used to measure hexamerization of anti-OX40 antibodies on the cell surface. Specific anti-OX40 antibody mutations were analyzed for increased antibody multimerization and engagement. Mutations promoting IgG hexamerization showed enhanced agonistic activity. (5056)

Notes: Researchers set out to identify CBP/EP300 bromodomain inhibitors potent to both in vitro targets and targets in cellular target engagement assays. They developed a series of selective probes of CBP/EP300 bromodomains identified first by fragment screening. They next substituted and modified parts of the fragments to improve potency and selectivity.

To determine whether improvements in CBP bromodomain inhibition that were observed in their biochemical assay would translate to a cellular context, they used a bioluminescence resonance energy transfer assay, NanoBRET, where a small CBP/EP300 bromodomain inhibitor disrupted the interaction between a HaloTag-labeled histone and bromodomain conjugated to NanoLuc® Luciferase.

NanoBRET™ CBP/Histone H3.3 Interaction Assay (Cat.# N1850) and FuGENE® HD Transfection Reagent (Cat.# E2311) were used in the cell-based assay. (4717)

Notes: The bromodomain and extraterminal (BET) family of proteins contain two bromodomains. A probe compound, biBET, capable of binding both bromodomains of BET proteins in cis is characterized. BDR4-NanoLuc and Halo-tagged histone H3 fusions are used to monitor biBET binding with the NanoBRET Target Engagement system. Interestingly, bivalent binding lead to slower displacement of inhibitor from BDR4 and increased potency. (5078)

Notes: The BRD9 subunit of the SWI-SNF chromatin-remodeling complex is investigated in the context of aberrant cell proliferation in acute myeloid leukemia. Specifically, the NanoBRET system was used to measure the interactions of BRD9 and Histone H3.3. A small molecule inhibitor of the BRB9 bromodomain function, BI-7273, was further assessed in HEK293T cells. Disruption of BRB9 interaction with Histone H3.3 was confirmed at sub-micromolar concentrations of BI-7273. Cell viability in the presence of inhibitor was determined using the CellTiter-Glo System. (5079)

Notes: HaloTag® Pull-Down Assay
HEK293T (12 × 10⁶ cells) were plated and grown to 70–80% confluence (approximately 18 hours). The cells were then transfected (using FuGENE® HD Transfection Reagent [Cat.# E2311]) with either 30µg of HaloTag(HT)-HIF1A or HT-alone control vector (vectors available by custom order from Promega Custom Assay Services). Clarified lysates from both HT-HIF1A and HT-alone control cells were prepared and incubated with HaloLink™ Resin (HaloTag® Mammalian Pull-Down System [Cat.# G6500, G6504]). Proteins were digested with trypsin, and digestion was quenched with formic acid. Digested peptides were analyzed by mass spectrometry.

NanoBRET™ Assay
HCT116 and HEK293 cells (8 ×10⁵) were plated in each well of a 6-well plate and co-transfected with one of three acceptors: HT-Pontin, HT-Reptin or HT-TIP60, in combination with the HIF1A-NanoLuc(NL) donor. The following NanoBRET pairs used are available by custom order from Promega Custom Assay Services: HIF1α-NLuc + HT-TIP60, HIF1α-NLuc + HT-Pontin or HIF1α-NLuc + HT-Reptin. (4718)

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: The authors describe a new method for real-time analysis of ligand-mediated receptor endocytosis in living cells. They used a BRET-based assay to detect the interactions of ligands with various GPCRs fused to NanoLuc® luciferase. (4693)

Notes: These authors describe a new method for monitoring ligand binding to GPCRs on the surface of living cells. They used NanoLuc luciferase in a BRET-based assay to detect the interactions of ligands with the receptors with an N-terminal NanoLuc fusion. (4589)

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)