Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay: The activities were measured using a time-resolved fluorescence resonance energy...

ID: ALA3889294

Type: Binding

Description: Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay: The activities were measured using a time-resolved fluorescence resonance energy transfer (TR-FRET) assay. TR-FRET monitored the formation of 3,4,5-inositol triphosphate molecule that competed with fluorescently labeled PIP3 for binding to the GRP-1 pleckstrin homology domain protein. An increase in phosphatidylinositide 3-phosphate product resulted in a decrease in TR-FRET signal as the labeled fluorophore was displaced from the GRP-1 protein binding site. Class I PI3K isoforms were expressed and purified as heterodimeric recombinant proteins. All assay reagents and buffers for the TR-FRET assay were purchased from Millipore. PI3K isoforms were assayed under initial rate conditions in the presence of 25 mM Hepes (pH 7.4), and 2xKm ATP (75-500 uM), 2 uM PIP2, 5% glycerol, 5 mM MgCl2, 50 mM NaCl, 0.05% (v/v) Chaps, 1 mM dithiothreitol, and 1% (v/v) DMSO at the following concentrations for each isoform: PI3Kα, PI3Kβ, and PI3Kδ between 25 and 50 uM, and PI3Kγ at 2 nM. The compounds of Table 1 and Compound X ((S)-2,4-diamino-6-((1-(5-chloro-4-oxo-3-(pyridin-3-yl)-3,4-dihydroquinazolin-2-yl)ethyl)amino)pyrimidine-5-carbonitrile) and Compound Y ((S)-2,4-diamino-6-((1-(5-chloro-4-oxo-3-(pyridin-3-yl)-3,4-dihydroquinazolin-2-yl)ethyl)amino)pyrimidine-5-carbonitrile) were added to the assay solution and incubated for 30 minutes at 25° C. The reactions were terminated with a final concentration of 10 mM EDTA, 10 nM labeled-PIP3, and 35 nM Europium labeled GRP-1 detector protein before reading TR-FRET on an Envision plate reader (Ex: 340 nm; Em: 615/665 nm; 100 us delay and 500 us read window). The results were normalized based on positive (1 uM wortmanin) and negative (DMSO) controls, and the IC50 values for PI3K α, β, δ and γ were calculated from the fit of the dose-response curves to a four-parameter equation.

Format: BAO_0000357

Organism: Homo sapiens

Target:  PI3-kinase p110-delta subunit(ALA3130)

Document:  ALA3887021

BindingDB Source:  8523