Identification and characterization of tissue-specific protein transduction domains using peptide phage display.

Protein transduction domains (PTD) or cell-penetrating peptides (CPPs) are small peptides that are able to carry proteins, nucleic acid, and particles across the cellular membranes into cells. PTDs can be classified into three types: (1) positively charged, cationic peptides, comprised of homopolymers of arginine, ornithine, or lysine; (2) hydrophobic peptides, derived from leader sequences of secreted proteins, and cell-type specific peptides; (3) tissue-specific, mainly amphipathic peptides identified by screening of peptide displaying phage libraries. The cationic and hydrophobic PTDs can efficiently transduce a variety of cell types in culture and in vivo, but in a nonspecific manner. In contrast, the tissue-specific transduction domains have more restricted transduction properties and presumably transduce cells through a different mechanism. In this chapter, we described methods for screening peptide phage display libraries for cell and tissue-specific transduction peptides both in cell culture and in vivo and for functional analysis of transduction.