Kinome profiling for uncovering the molecular mode of pharmacon action

Defining the molecular effects of compounds with clinically useful properties remains exceedingly challenging if no a priori assumptions can be made as to the biochemical details of the biological effect observed. We set out to identify the molecular target of violacein, a purple-coloured pigment produced by the Amazon River Chromobacterium violaceum, which is used by indigenous Indians in the Amazon forest to treat a variety of inflammatory conditions and attracts substantial interest as a consequence of its anti-leukaemic properties. To this end, we compared lysates of violacein-treated cells and vehicle-treated cells for in vitro phosphorylation of peptide arrays containing 1152 different kinase consensus substrates. The results provide a wealth of data on violacein-dependent biochemical effects. From this kinome profiling effort, the p42/p44 MAP kinase pathway emerged as a major target for violacein. Subsequent studies revealed that activation of the p42/p44 MAP kinase pathway is essential for violacein-dependent effects, triggering differentiation of the leukaemia cells.