Characterization of a Chemical Affinity Probe Targeting Akt Kinases

Protein kinases are key regulators
of cellular processes, and aberrant
function is often associated with human disease. Consequently, kinases
represent an important class of therapeutic targets and about 20 kinase
inhibitors (KIs) are in clinical use today. Detailed knowledge about
the selectivity of KIs is important for the correct interpretation
of their pharmacological and systems biological effects. Chemical
proteomic approaches for systematic kinase inhibitor selectivity profiling
have emerged as important molecular tools in this regard, but the
coverage of the human kinome is still incomplete. Here, we describe
a new affinity probe targeting Akt and many other members of the AGC
kinase family that considerably extends the scope of KI profiling
by chemical proteomics. In combination with the previously published
kinobeads, the synthesized probe was applied to selectivity profiling
of the Akt inhibitors GSK690693 and GSK2141795 in human cancer cells.
The results confirmed the inhibition of all Akt isoforms and of a
number of known as well as CDC42BPB as a novel putative target for
GSK690693. This work also established, for the first time, the kinase
selectivity profile of the clinical phase I drug GSK2141795 and identified
PRKG1 as a low nanomolar kinase target as well as the ATP-dependent
5′-3′ DNA helicase ERCC2 as a potential new non-kinase
off-target.