Fluorescent Biosensor of CDK5 Kinase Activity in Glioblastoma Cell Extracts and Living Cells

International audienceCDK5 plays a major role in neuronal functions, and is hyperactivated inneurodegenerative pathologies as well as in glioblastoma and neuroblastoma.Although this kinase constitutes an established biomarker andpharmacological target, there are few means of probing its activity in cellextracts or in living cells. To this aim a fluorescent peptide reporter of CDK5kinase activity, derived from a library of CDK5-specific substrates, isengineered and its ability to respond to recombinant CDK5/p25 is establishedand CDK5 activity in glioblastoma cell extracts is reported on throughsensitive changes in fluorescence intensity. A cell-penetrating variant of thisbiosensor which can be implemented to image CDK5 activation dynamics inspace and in time is further implemented. This original biosensor constitutesa potent tool for quantifying differences in CDK5 activity following treatmentwith selective inhibitors and for monitoring CDK5 activation, followinginhibition or stimulation, in a physiologically relevant environment. As such itoffers attractive opportunities to develop a diagnostic assay for neuronalpathologies associated with hyperactivated CDK5, as well as a companionassay to evaluate response to new therapies targeting this kinase