EXPRESSION AND ACTIVITY OF CYCLIN-DEPENDENT KINASE 5 P35 IN ADULT-RATPERIPHERAL NERVOUS-SYSTEM/

In spite of the clarification in the temporal and spatial expression p attern of a cyclin-dependent kinase (Cdk)5 and its neuron-specific act ivator, p35, in the CNS, it remains to be elucidated in the PNS. In ad dition, it is not known whether Cdk5 activity exists in the PNS. There fore, we have examined their expression and activity in the PNS by imm unoblot analysis, immunohistochemistry, and in vitro kinase assay. Imm unoblot analysis indicated the expression of Cdk5 and p35 proteins in dorsal root ganglion (DRG) and sciatic nerve alike in the CNS. By immu nohistochemistry, both proteins were shown to be present in the cell b ody and axon (sciatic nerve) of both DRG neurons and anterior horn cel ls. A co-immunoprecipitation study indicated the in vivo association b etween Cdk5 and p35 in both DRG and sciatic nerve. However, Cdk5 kinas e activity was found only in DRG, but not in sciatic nerve. These resu lts suggest that Cdk5 kinase activity exists and functions physiologic ally in the PNS and may be regulated by unknown mechanisms other than the availability of p35 as reported in developing brains.