scholarly journals A NanoBRET-based binding assay for Smoothened allows real time analysis of small-molecule ligand binding and distinction of two separate ligand binding sites for BODIPY-cyclopamine

2019 ◽  
Author(s):  
Paweł Kozielewicz ◽  
Carl-Fredrik Bowin ◽  
Gunnar Schulte
Keyword(s):  
Energy Transfer ◽  
Ligand Binding ◽  
Real Time ◽  
Binding Sites ◽  
Binding Assay ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Ligand Binding Assay ◽  
Binding Assays ◽  
Class F

AbstractBackground and PurposeSmoothened (SMO) is a GPCR that mediates hedgehog signaling. Hedgehog binds the Patched, which in turn regulates SMO activation. Overactive SMO signaling is oncogenic and is therefore a clinically established drug target. Here, we establish a nanoluciferase bioluminescence resonance energy transfer (NanoBRET)-based ligand binding assay for SMO providing a sensitive and high throughput-compatible addition to the toolbox of GPCR pharmacologists.Experimental ApproachIn the NanoBRET-based binding assay, SMO is N terminally tagged with nanoluciferase (Nluc) and binding of BODIPY-cyclopamine is assessed by quantifying resonance energy transfer between receptor and ligand. The assay allows kinetic analysis of ligand-receptor binding in living HEK293 cells and competition binding experiments using commercially available SMO ligands (SANT-1, cyclopamine-KAAD, SAG1.3 and purmorphamine).Key ResultsThe NanoBRET binding assay for SMO is sensitive and superior to purely fluorescence-based binding assays. BODIPY-cyclopamine showed complex binding parameters suggesting separate binding sites.Conclusions and ImplicationsThe NanoBRET ligand binding assay for SMO provides a fast, sensitive and reliable alternative to assess SMO ligand binding. Furthermore, this assay is sufficiently sensitive to dissect a SANT-1-sensitive and a SANT-1-insensitive cyclopamine binding site in the 7TM core, and will be important to further dissect and understand the molecular pharmacology of Class F receptors.What is already knownCyclopamine targets SMO as antagonist and fluorescently-labelled cyclopamine has been used for fluorescence-based binding assays for SMO. Structural analysis has suggested two binding sites on SMO, one in the receptor core and one the CRD.What this study addsWe established a NanoBRET-based binding assay for SMO with superior sensitivity compared to fluorescence-based assays. This assay allows distinction of two separate binding sites for BODIPY-cyclopamine on SMO in live cells in real time.What is the clinical significanceThe assay is a valuable complement for drug discovery efforts and will support a better understanding of Class F GPCR pharmacology.

Quantum Dot Bioconjugates as Energy Donors in Fluorescence Resonance Energy Transfer Assays

2003 ◽  
Vol 773 ◽  
Author(s):  
Aaron R. Clapp ◽  
Igor L. Medintz ◽  
J. Matthew Mauro ◽  
Hedi Mattoussi
Keyword(s):  
Energy Transfer ◽  
Quantum Dot ◽  
Organic Dyes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Genetically Engineered ◽  
Molar Ratio ◽  
Binding Assays ◽  
Specific Sequence ◽  
Donor Acceptor

AbstractLuminescent CdSe-ZnS core-shell quantum dot (QD) bioconjugates were used as energy donors in fluorescent resonance energy transfer (FRET) binding assays. The QDs were coated with saturating amounts of genetically engineered maltose binding protein (MBP) using a noncovalent immobilization process, and Cy3 organic dyes covalently attached at a specific sequence to MBP were used as energy acceptor molecules. Energy transfer efficiency was measured as a function of the MBP-Cy3/QD molar ratio for two different donor fluorescence emissions (different QD core sizes). Apparent donor-acceptor distances were determined from these FRET studies, and the measured distances are consistent with QD-protein conjugate dimensions previously determined from structural studies.

scholarly journals AIE-Driven Fluorescent Polysaccharide Polymersome as Enzyme-responsive FRET Nanoprobe to Study the Real-time Delivery Aspects in Live-Cells

2021 ◽  
Author(s):  
Nilesh Umakant Deshpande ◽  
Mishika Virmani ◽  
Manickam Jayakannan
Keyword(s):  
Energy Transfer ◽  
Confocal Microscopy ◽  
Real Time ◽  
Fluorescence Resonance Energy Transfer ◽  
Imaging Techniques ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Live Cells ◽  
Intracellular Enzyme ◽  
Bio Imaging

We report aggregation induced emission (AIE) driven polysaccharide polymersome as fluorescence resonance energy transfer (FRET) nanoprobes to study their intracellular enzyme-responsive delivery by real-time live-cell confocal microscopy bio-imaging techniques. AIE...

scholarly journals Designing and Development of FRET-Based Nanosensor for Real Time Analysis of N-Acetyl-5-Neuraminic Acid in Living Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Ruphi Naz ◽  
Mohammad K. Okla ◽  
Urooj Fatima ◽  
Mohd. Mohsin ◽  
Walid H. Soufan ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Metabolic Engineering ◽  
Sialic Acid ◽  
Real Time ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Neuraminic Acid ◽  
Yeast Cells ◽  
Metabolite Level ◽  
Health Maintenance

N-acetyl-5-neuraminic acid (NeuAc) plays crucial role in improving the growth, brain development, brain health maintenance, and immunity enhancement of infants. Commercially, it is used in the production of antiviral drugs, infant milk formulas, cosmetics, dietary supplements, and pharmaceutical products. Because of the rapidly increasing demand, metabolic engineering approach has attracted increasing attention for NeuAc biosynthesis. However, knowledge of metabolite flux in biosynthetic pathways is one of the major challenges in the practice of metabolic engineering. So, an understanding of the flux of NeuAc is needed to determine its cellular level at real time. The analysis of the flux can only be performed using a tool that has the capacity to measure metabolite level in cells without affecting other metabolic processes. A Fluorescence Resonance Energy Transfer (FRET)-based genetically-encoded nanosensor has been generated in this study to monitor the level of NeuAc in prokaryotic and eukaryotic cells. Sialic acid periplasmic binding protein (SiaP) from Haemophilus influenzae was exploited as a sensory element for the generation of nanosensor. The enhanced cyan fluorescent protein (ECFP) and Venus were used as Fluroscence Resonance Energy Transfer (FRET) pair. The nanosensor, which was termed fluorescent indicator protein for sialic acid (FLIP-SA), was successfully transformed into, and expressed in Escherichia coli BL21 (DE3) cells. The expressed protein of the nanosensor was isolated and purified. The purified nanosensor protein was characterized to assess the affinity, specificity, and stability in the pH range. The developed nanosensor exhibited FRET change after addition to NeuAc. The developed nanosensor was highly specific, exhibited pH stability, and detected NeuAc levels in the nanomolar to milimolar range. FLIP-SA was successfully introduced in bacterial and yeast cells and reported the real-time intracellular levels of NeuAc non-invasively. The FLIP-SA is an excellent tool for the metabolic flux analysis of the NeuAc biosynthetic pathway and, thus, may help unravel the regulatory mechanism of the metabolic pathway of NeuAc. Furthermore, FLIP-SA can be used for the high-throughput screening of E. coli mutant libraries for varied NeuAc production levels.

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