Cyclin-dependent kinase 5 in axon growth and regeneration.

Injury to the central nervous system often leads to irreversible deficits because of the failure of damaged axons to regrow and restore the functional neural circuitry. Coordinated orchestration of multiple cellular processes including cytoskeletal dynamics and gene expression are essential for both developmental and regenerative axon growth. Recently, mounting evidence suggests that cyclin-dependent kinase 5 (Cdk5), a neuronal kinase implicated in almost all aspects of brain development and function, regulates multiple players required for axon formation and regeneration. Indeed, Cdk5 functions as a "plastic" kinase that maintains the axon growth ability by enabling efficient cytoskeletal reorganization, enhancing protein translation, reducing protein degradation, and promoting injury-induced gene transcription. Here, we summarize the up-to-date information on the mechanisms underlying the axon growth and regeneration after injury.