title: Protein kinase CK2 is an inhibitor of the neuronal Cdk5 kinase.
abstract: The complex of Cdk5 and its neuronal activator p35 is a proline-directed Ser/Thr kinase that plays an important role in various neuronal functions. Deregulation of the Cdk5 enzymatic activity was found to associate with a number of neurodegenerative diseases. To search for regulatory factors of Cdk5-p35 in the brain, we developed biochemical affinity isolation using a recombinant protein comprising the N-terminal 149 amino acids of p35. The catalytic alpha-subunit of protein kinase CK2 (formerly known as casein kinase 2) was identified by mass spectrometry from the isolation. The association of CK2 with p35 and Cdk5 was demonstrated, and the CK2-binding sites were delineated in p35. Furthermore, CK2 displayed strong inhibition toward the Cdk5 activation by p35. The Cdk5 inhibition is dissociated from the kinase function of CK2 because the kinase-dead mutant of CK2 displayed the similar Cdk5 inhibitory activity as the wild-type enzyme. Further characterization showed that CK2 blocks the complex formation of Cdk5 and p35. Together, these findings suggest that CK2 acts as an inhibitor of Cdk5 in the brain.
authors.affiliation: Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609.
authors.forename: Anthony C B
authors.initials: AC
authors.lastname: Lim
authors.forename: Zhibo
authors.initials: Z
authors.lastname: Hou
authors.forename: Choon-Peng
authors.initials: CP
authors.lastname: Goh
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Qi
mesh_terms: D000818:Animals; D001665:Binding Sites; D047390:Casein Kinase II / Q000502:physiology*; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D002845:Chromatography; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D019636:Neurodegenerative Diseases / Q000473:pathology; D009474:Neurons / Q000201:enzymology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D014162:Transfection
chemical_list: D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C089495:neuronal Cdk5 activator (p25-p35); D011392:Proline; D005982:Glutathione Transferase; D047390:Casein Kinase II