Inhibition of human recombinant N-terminal His6-tagged IGF-1R using fluorescence substrate after 80 mins by caliper off-chip incubation mobility shift assay
Inhibition of IGF-1R (unknown origin) assessed as remaining activity at 100 uM by radioactive filter binding assay in presence of [33P]-ATP relative to control
Inhibition of Tel-fused IGF1R (unknown origin) expressed in mouse BA/F3 cells after 48 hrs by luciferase reporter gene assay in absence of recombinant mouse IL3
DELFIA assay: The kinase activity is measured by DELFIA assay (dissociation-enhanced lanthanide fluorescence immunoassay, Perkin Elmer). The cytoplasmic kinase domain of human IGF-1R (amino acids 964-1370) is expressed as a fusion protein with a glutathione-S-transferase tag (IGF-1R-GST) in High Five Cells (Invitrogen). Enzyme activity is measured in the presence of substances and a control substance. Poly-glutamate-tyrosine peptide (pEY, Sigma Aldrich) and biotinylated pEY (bio-pEY) are used as reaction substrates. 10 uL of substance in 25% DMSO are mixed with 30 uL of IGF-1R-GST solution (67 mM HEPES pH 7.4, 15 ug/mL pEY, 1.7 ug/mL bio-pEY, 13.3 mM MgCl2, 3.3 mM dithiothreitol, 0.0033% Brij 35, 2 ng IGF-1R-GST) in 96-well plates. The reactions are started with 10 uL of a 750 uM ATP solution. After 40 min at RT the reactions are stopped with 50 uL of stop solution (250 mM EDTA, 20 mM HEPES pH 7.4).
Biochemical Assay: The inhibitory activity of putative kinase inhibitors and the potency of selected compounds were determined using a trans-phosphorylation assay.A specific substrate was incubated with the kinase in appropriate buffer conditions in the presence of ATP traced with .sup.33P-.gamma.-ATP (gamma phosphate-labeled, Redivue.TM. Code Number AH9968, 1000-3000 Ci/mmole, Amersham Biosciences Piscataway, N.J., USA), optimal cofactors and test compound.At the end of the phosphorylation reaction, more than 98% cold and radioactive ATP were captured by an excess of Dowex ion exchange resin. The resin was allowed to settle to the bottom of reaction wells by gravity. Supernatant, containing substrate peptide, was subsequently withdrawn and transferred into a counting plate, and radioactivity (corresponding to phosphate incorporated into peptide) was evaluated by .beta.-counting. Assay Conditions:The kinase assay was run with a final enzyme concentration of 6 nM, in the presence of 6 microM ATP, 1 nM .
In Vitro Kinase Activity Assay: Compounds to be tested were dissolved in 100% DMSO in a range of concentrations from 10-8 to 10-3 M including negative control (DMSO), then diluted with Kinase Buffer (50 mM HEPES, pH 7.5, 1 mM EGTA, 10 mM MgCl2, 0.01% Tween-20, and 2 mM DTT, added fresh) to 4x the final concentration. The final curve included 11 concentrations (10-11 to 10-5 M) plus negative control DMSO tested in triplicate.Kinase and ATP concentrations necessary for optimal activity were determined in separate experiments. (Table 2). Briefly, increasing concentrations of kinase were incubated in a fixed concentration of ATP (200 uM) in Kinase Buffer to determine maximal activity at various time points (30-120 min). The concentration of kinase that resulted in maximal activity with the shortest incubation time was then incubated in Kinase Buffer with increasing concentrations of ATP.