DEVELOPMENTAL-CHANGES OF CYCLIN-DEPENDENT KINASE-5 SUBCELLULAR-LOCALIZATION IN THE RAT CEREBELLUM

CYCLIN dependent kinase 5 (Cdk5) phosphorylates tau protein, a microtu ble-associated protein, at pathological sites in vitro as well as in A lzheimer's disease brain. The enzyme is therefore regarded as an impor tant candidate responsible for the progression of Alzheimer's disease. We and others have suggested that the enzyme has physiological roles in brain development and maturation. In this study, we investigated th e exact distribution and developmental changes of the enzyme in cerebe llum by immunohistochemistry and non-radioactive in situ hybridization . Immunohistochemistry demonstrated that Cdk5 was consistently express ed in the cerebellum at all developing stages. However, the subcellula r localization of Cdk5 dramatically changed during maturation of the c erebellum. In the early neonatal stage, Cdk5 was strongly expressed in the cell bodies of neurones. With neuronal maturation Cdk5 immunoreac tivity changed its subcellular localization from the cell body to axon . In terminally differentiated neurons, the immunoreactivity was only detected in the axon. These results suggest that subcellular localizat ion of Cdk5 is strictly regulated and may play an important role in ne uronal maturation.