Protein-acrylamide copolymer hydrogels for array-based detection of tyrosine kinase activity from cell lysates

We describe the development of an array-based assay for the molecular level detection of tyrosine kinase activity directly from cellular extracts. Glutathione S-transferase-Crk1 (GST-Crk1) fusion proteins are covalently immobilized into polyacrylamide gel pads via copolymerization of acrylic monomer and acrylic-functionalized GST-Crk1 protein constructs on a polyacrylamide surface. The resulting hydrogels resist nonspecific protein adsorption, permitting quantitative and reproducible determination of Abl tyrosine kinase activity and inhibition, even in the presence of a complex cell lysate mixture. Half-maximal inhibition (IC50) values for imatinib mesylate inhibition of GST-Crk1 (SH3) phosphorylation by v-Abl in a purified system and Bcr-Abl within a K562 cell lysate were determined to be 1.5 and 20 mu M, respectively. Additionally, the protein-acrylamide copolymer arrays detected CML cell levels as low as 15% in a background of Bcr-Abl- leukemic cells and provided the framework for the parallel evaluation of six tyrosine kinase inhibitors. Such a system may have direct application to the detection and treatment of cancers resulting from upregulated tyrosine kinase activity, such as chronic myeloid leukemia (CML). These findings also establish a basis for screening tyrosine kinase inhibitors and provide a framework on which protein-protein interactions in other complex systems can be studied.