α‐Chimaerin exists in a functional complex with the Cdk5 kinase in brain

Abstract
Cyclin‐dependent kinase 5 (Cdk5) in association with its neuronal activators p35 and p39 shows a complex involvement in the control of neurocytoskeletal dynamics. Here we show that α‐chimaerin, a GTPase‐activating protein specific for Rac and Cdc42, is a p35‐binding protein. The interaction domains of p35 and α‐chimaerin were delineated. In transfected HeLa cells, p35 and α‐chimaerin displayed an overlapping distribution pattern and they could be co‐immunoprecipitated from the cell lysate. As α‐chimaerin has a regulatory function in actin repolymerization, these results suggested that the regulation of neurocytoskeleton dynamics by Cdk5 is mediated at least in part via α‐chimaerin.