Enhanced gene delivery to PC12 cells by a cationic polypeptide

Targeted gene delivery to diseased subtypes of neurons will be beneficial to the success of gene therapy of neurological disorders. We designed a recombinant cationic polypeptide to facilitate gene delivery to neuronal-like PC12 cells that express the nerve growth factor (NGF) receptors. The recombinant polypeptide was composed of a targeting moiety derived from loop 4-containing hairpin motif of NGF and a DNA-binding moiety of 10-lysine sequence and expressed in Escherichia coli. It activated NGF receptor, TrkA and its downstream signaling pathways in PC12 and promoted the survival of neuronally differentiated PC12 cells deprived of serum. The polypeptide could also bind plasmid DNA and enhance polycation-mediated gene delivery in NGF receptor-expressing PC12 cells, but not in COS7 cells lacking NGF receptors. The enhancement of gene transfer in PC12 was inhibited by pretreatment of free, unbound polypeptides, suggesting a NGF-receptor-specific effect of the polypeptide. These observations demonstrated the concept of using receptor-mediated mechanism for targeted gene delivery to neurons.