Enzyme-linked immunosorbent assay for the measurement of JNK activity in cell extracts

A colorimetric enzyme-linked immunosorbent assay (ELISA) for the measuremen t of kinase activity of c-Jun N-terminal kinases (JNKs) in cell extracts is described, The assay involves passive immobilisation of the substrate GST- cJun on the surface of a microtiter plate, selection of JNK protein kinases directly in substrate-coated wells, kinase reaction, and detection of subs trate phosphorylation by a phosphoepitope-specific antibody, The ability of this assay to selectively measure JNK activity relies on the high-affinity interaction between JNKs and c-Jun, Accordingly, we found that JNKs could be captured on the microtiter plate surface through binding to the immobili sed GST-cJun. Moreover, JNKs retained the specificity of their interaction with and phosphorylation of c-Jun with respect to the dependence on both in tact docking domain and the dimerisation state of c-Jun. This novel procedu re represents a marked improvement on conventional radioactive assays in te rms of sensitivity, accuracy of evaluation, low time consumption, high thro ughput and amenability to automation. It is expected to be useful for the a cceleration and facilitation of JNK activity measurement in cell extracts, in particular for large-scale screening of clinical samples.