Identification of protein kinase C inhibitory activity associated with a polypeptide isolated from a phage display system with homology to PCM-1, the pericentriolar material-1 protein.

We had previously identified a protein kinase C (PKC) inhibitor in murine neuroblastoma cells (Chakravarthy et al. [1]). Similar PKC inhibitory activity was also found in adult rat brain. Using polyclonal antibodies raised against the partially purified PKC inhibitor from rat brain as bait, we isolated a putative brain PKC inhibitor using a T-7 phage display system expressing human brain cDNA library. After enriching the phage population expressing the putative PKC inhibitor with four rounds of biopanning using ELISA and in vitro PKC binding assays, we identified a phage clone that expressed a product with significant PKC inhibitory activity. We have cloned and expressed this cDNA in a bacterial system and purified the recombinant protein. This polypeptide (174 amino acids) is highly homologous to a region of the 228-kDa PCM-1, the human pericentriolar material 1 protein. We have mapped this polypeptide's PKC-inhibitory domain and shown its PKC inhibitory activity in vitro. However, it will need to be determined whether the full-length PCM-1 protein possesses PKC inhibitory activity in vivo, and if so, how this might contribute to PCM-1's recently demonstrated roles in ciliogenesis and neurogenesis.