Cdk5 phosphorylation of FAK regulates centrosome-associated miocrotubules and neuronal migration.

Cdk5 is a member of the cyclin-dependent kinase (Cdk) family. Unlike other Cdks that promote cell cycle, Cdk5 is activated in postmitotic neurons and critically regulates neuronal migration by phosphorylating its substrates during brain development. Recently, we found that Cdk5 phosphorylates focal adhesion kinase (FAK) at Serine 732 in vitro and is responsible for this phosphorylation in the developing brain. Our experiments using a phospho-specific antibody and an S732-unphosphorylatable mutant FAK suggest that S732 phosphorylation may regulate a centrosome-associated microtubule structure to promote nuclear translocation, a critical step in neuronal migration. S732 phosphorylation does not directly impact on the kinase activity of FAK, but appears to prevent the accumulation of FAK at the centrosome. Our study reveals a similarity between Cdk5 and Cdk1 in the regulation of neuronal migration and cell division, respectively. In addition, our study implicates FAK in a signaling pathway that directly regulates microtubules.