Resumen de Mechanistic studies on Protein Kinase B regulation and insights for the discovery of potential allosteric kinase inhibitors
Signal transduction into the cell occurs through cell surface receptors, which specifically recognize extracellular messengers and then further transmit the signal to intracellular molecules. In the complex system of communication pathways that governs the behaviour of the cell, growth factor and cell adhesion signalling tightly and cooperatively cross talk to provide crucial stimuli for the regulation of important cellular functions, such as cell proliferation, survival and migration. Signalling proteins need to be strictly controlled to prevent the rise of pathologies, like cancer and metabolic diseases. In our studies we focused on two kinases that belong to different family: Protein Kinase B (PKB) and Focal Adhesion Kinase (FAK). They are both key signalling molecules, PKB is activated downstream of growth factor-induced PI3K signalling, and FAK downstream of integrin cell- matrix adhesion receptors; both have been reported as attractive drug targets. Based on a detailed biochemical analysis, we propose a model of how the different PKB domains modulate the signalling output. Our results suggest that PKB can follow two distinct activation pathways depending on the nature of the upstream signal. Furthermore, we propose that PKB targets specific substrates depending on the activation pathway. Such new insights on PKB regulation and substrate specificity could allow the interpretation of the effects of different classes of PKB inhibitors and enable the design of inhibitors with improved specificity. Moreover, we performed a screening of fragments-like compounds (<300 Da), interacting with allosteric pockets on the FERM domain of FAK. Crystal structures of FERM in complex with these fragments have been solved and structural data for two positive fragment hits have been obtained. The collected structural information will guide the strategy and design of extended compounds that potentially can be developed into allosteric inhibitors.
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