Kinase assays

PDK1 was assayed in a direct kinase assay and a coupled assay format measuring PDK1- and PtdIns-3,4-P2-mediated activation of AKT2. For the coupled assay, the final assay mixture (60 μL) contained: 15 mM MOPS, pH 7.2, 1 mg/mL bovine serum albumin, 18 mM β-glycerol phosphate, 0.7 mM dithiothreitol, 3 mM EGTA, 10 mM MgOAc, 7.5 μM ATP, 0.2 μCi of [γ-33P]ATP, 7.5 μM biotinylated peptide substrate (biotin-ARRRDGGGAQPFRPRAATF), 0.5 μL of PtdIns-3,4-P2-containing phospholipid vesicles, 60 pg of purified recombinant human PDK1, and 172 ng of purified recombinant human AKT2. After incubation for 2 hrs at room temperature, the biotin-labeled peptide was captured from 10 μL of the assay mixture on streptavidin-coated SPA beads, and product formation was measured by scintillation proximity in a Wallac MicroBeta counter. The product formed was proportional to the time of incubation and to the amount of PDK1 and inactive AKT2 added. PDK1 was added at suboptimal levels so that the assay could sensitively detect inhibitors of AKT2 activation as well as direct inhibitors of PDK1 or AKT2. To measure PDK1 activity directly, the final assay mixture (60 μL) contained 50 mM Tris-HCl, pH 7.5, 0.1 mM EGTA, 0.1 mM EDTA, 0.1% β-mercaptoethanol, 1 mg/mL bovine serum albumin, 10 mM MgOAc, 10 μM ATP, 0.2 μCi of [γ-33P]ATP, 7.5 μM substrate peptide (H2N-ARRRGVTTKTFCGT), and 60 ng of purified recombinant human PDK1. After 4 hrs at room temperature, we added 25 mM EDTA and spotted a portion of the reaction mixture on Whatman P81 phosphocellulose paper. The filter paper was washed three times with 0.75% phosphoric acid and once with acetone. After drying, the filter-bound labeled peptide was quantified using a Fuji phosphorimager.

Cell lines

MDA-468, HCT-116 and MiaPaca cells

Preparation method

The solubility of this compound in DMSO is >10 mM. General tips for obtaining a higher concentration: Please warm the tube at 37 ℃ for 10 minutes and/or shake it in the ultrasonic bath for a while. Stock solution can be stored below -20 ℃ for several months.

Reaction Conditions

~10 μM; 72 hrs

Applications

BX795 potently inhibited tumor cell growth, with the IC50 values of 1.6, 1.4 and 1.9 μM for MDA-468, HCT-116 and MiaPaca cells, respectively.

BX795, a small molecule with an aminopyrimidine backbone in its chemical structure, is a potent and ATP-competitive inhibitor of 3-phosphoinositide-dependent kinase 1 (PDK1) that binds to the ATP binding pocket of PDK1 and hence potently inhibits the enzymatic activity of PDK1 in a direct kinase assay format with a value of 50% concentration inhibition IC₅₀of 11 nM. BX795 is also a potent and selectively inhibitor of TANK-binding kinase 1 (TBK1) and IκB kinase ε (IKKε), with values of IC₅₀of 0.006 μM and 0.041 μM respectively, that blocks the phosphorylation, nuclear translocation and transcriptional activity of interferon regulatory factor 3 as well as the production of interferon-β in macrophages stimulated with poly(I:C) or lipopolysaccharide (LPS).

Reference

Feldman RI, Wu JM, Polokoff MA, Kochanny MJ, Dinter H, Zhu D, Biroc SL, Alicke B, Bryant J, Yuan S, Buckman BO, Lentz D, Ferrer M, Whitlow M, Adler M, Finster S, Chang Z, Arnaiz DO. Novel small molecule inhibitors of 3-phosphoinositide-dependent kinase-1. J Biol Chem. 2005 May 20;280(20):19867-74.

Clark K, Plater L, Peggie M, Cohen P. Use of the pharmacological inhibitor BX795 to study the regulation and physiological roles of TBK1 and IkappaB kinase epsilon: a distinct upstream kinase mediates Ser-172 phosphorylation and activation. J Biol Chem. 2009 May 22;284(21):14136-46.