Phosphorylation of Canine Distemper Virus P Protein by Protein Kinase C-ζ and Casein Kinase II

AbstractTranscription by nonsegmented negative-strand RNA viruses is mediated by the viral RNA-dependent RNA polymerase and transcriptional cofactor P. The P protein is activated by phosphorylation, an event initiated by cellular kinases. The kinase used differs among this group of RNA viruses; vesicular stomatitis virus and respiratory syncytial virus utilize casein kinase II (CKII), whereas human parainfluenza virus type 3 utilizes PKC isoform zeta (PKC-ζ) for activation of its P protein. To identify the cellular kinase(s) involved in the phosphorylation of the canine distemper virus (CDV) P protein, we used recombinant CDV P in phosphorylation assays with native kinase activities present in CV1 cell extracts or purified CKII and PKC isoforms. Here, we demonstrate that the CDV P protein is phosphorylated by two cellular kinases, where PKC-ζ has the major and CKII the minor activities. In contrast, the P protein of another member of the morbillivirus genus, measles virus, is phosphorylated predominantly by CKII, whereas PKC-ζ has only minor activity. Selective inhibition of PKC-ζ activity within CV1 cells eliminated permissiveness to CDV replication, indicating anin vivorole for PKC-ζ in the virus replication cycle. The broad tissue expression of PKC-ζ parallels the pantropic nature of CDV infections, suggesting that PKC-ζ activity is a determinant of cellular permissiveness to CDV replication