Injury to the central nervous system (CNS) results in irreversible loss of function,partly due to a lack of robust regeneration by CNS axons following severing or other damage.Regeneration failure results both from neuron-intrinsic limitations on regeneration and from inhibitory factors in the injury environment.Unfortunately,effective treatments to improve CNS regeneration are still lacking.Such treatments will likely require small molecules that can target more than one source of regeneration failure.Axon growth is regulated by protein kinases (PKs) and phosphatases.Although there are more than 300 PKs,only 50-60 have been investigated for their roles in axon growth signaling.A comprehensive picture of PK signaling in axon growth is being developed using kinase inhibitor (Kl) compounds as tools.A large number (about 1 500) of KIs are being screened for their ability to promote or inhibit axon growth,using phenotypic assays with primary neurons.Chemotyping (chemical structure/activity analysis) and informatic analysis,especially integration with kinase inhibitor profiling data,will allow us to identify the PKs and their networks targeted by the active KIs.Model network predictions are being tested using gain- and loss-of-function phenotypic analyses in primary neurons.Preliminary data from this project correctly identifies a number of classic PKs,such as ROCK,previously implicated in axon growth,but also suggests that ROCK inhibitors have off-target effects that contribute to their efficacy in growth stimulation.Our data also implicate PKs not previously understood to be important in axon growth pathways.