Characterization of a class of cationic peptides able to facilitate efficient protein transduction in vitro and in vivo

Protein transduction domains (PTDs), such as the third helix of the Drosoph ila Antennapedia homeobox gene (Antp) and the HIV TAT PTD, posses a charact eristic positive charge on the basis of their enrichment for arginine and l ysine residues. To determine whether cationic peptides are able to function as protein transduction domains, 12-mer peptide sequences from an M13 phag e library were selected for synthesis on the basis of their varying cationi c charge content. In addition, polylysine and polyarginine peptides were sy nthesized in order to assess the effect of charge contribution in protein t ransduction. Coupling of the biotinylated peptides to avidin-beta -galactos idase facilitated transduction in a wide variety of cell lines and primary cells, including islet beta -cells, synovial cells, polarized airway epithe lial cells, dendritic cells, myoblasts, and tumor cells. Two of the peptide s, PTD-4 and PTD-5, mediated transduction nearly 600-fold more efficiently than a random control peptide, but with an efficiency similar to the TAT PT D and the 12 mers of polylysine and polyarginine. Furthermore, confocal ana lysis of biotinylated peptide-streptavidin-Cy3 conjugates demonstrated that the internalized PTDs are found in both the nuclei and the cytoplasm of tr eated cells. When tested in vivo, the PTDs were able to facilitate efficien t and rapid protein delivery into rabbit synovium and mouse solid tumors fo llowing intraarticular and intratumoral administration, respectively. These novel PTDs can be used to transfer therapeutic proteins and DNA for the tr eatment of a wide variety of diseases, including arthritis and cancer.