Example 48
Enzymatic activity was determined using a commercial HotSpot kinase assay. Recombinant human p70S6K kinase was purchased from ThermoFisher Scientific (cat #PV3815). The substrate S6K/RSK2 peptide 2 was synthesized at Genscript [Piscataway, NJ]. In brief, the substrate was prepared in the reaction buffer [20 mM Hepes (pH 7.5), 10 mM MgCl2, 1 mM EGTA, 0.02% Brij35, 0.02 mg/mL BSA, 0.1 mM Na3VO4, 2 mM DTT, 1% DMSO]. Testing compounds were dissolved in 100% DMSO and a serial dilution was conducted in DMSO. The kinase at final concentration of 3 nM was added into the substrate solution and gently mixed. Test compounds were delivered at the appropriate concentrations into the kinase reaction mixture by Echo550, and incubated for 20 minutes at room temperature. 33P-ATP (Specific activity 10 μCi/μL) was added into the reaction mixture to initiate the reaction. Assay plates were incubated for 2 hours at room temperature. The radioactivity was detected by filter-binding method. Kinase activity data is expressed as the percent remaining kinase activity in test samples compared to vehicle (DMSO) reactions. IC50 curves were plotted and IC50 values were calculated using the GraphPad Prism 4 program based on a sigmoidal dose-response equation.
