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12 Cell-Penetrating Peptides: Processes and Applications
FIGURE 1.5 (Color Figure 1.5 follows p. 14.) Tat-CPP mediated intracellular delivery of a
p53 peptide. Panel A: 10 µM of the tandem peptide was incubated on U2OS cells for 30 min
at 37°C. p53 cellular entry was assessed by indirect immunofluorescence using an anti-p53
antibody (DO-1). Nucleolar and cytoplasmic detection of the conjugate can be visualized.
Panel B: U2OS cells were incubated with 50 µM of p53. Only the background level could
be detected. This background corresponded to the endogeneous p53 as assessed by treating
cells with the anti-p53 antibody alone (Panel C). Panel D: control corresponding to the
incubation of cells with the fluorescein-labeled secondary antibody.
infancy and are poorly efficient compared to retrovirus- or adenovirus-based viral
vectors. Trapping in the endocytic compartments and poor translocation from the
cytoplasm to the nuclei are generally recognized as limiting steps of synthetic DNA
delivery systems. In keeping with these limitations, endosome-disrupting agents (for
instance, inactivated adenovirus particles) greatly increase the efficiency of nonviral
plasmid DNA delivery, 38 as stated in the introduction. Both limitations could, in
theory, be alleviated by cell-penetrating peptides such as Tat or Antennapedia. In a
recent publication, Eguchi and colleagues 39 fused the protein transduction domain
of Tat (amino acids 43–60) to the N-terminal end of bacteriophage lambda D-head
protein displayed in multiple copies (420 copies) at the surface of the phage particle.
These engineered phage particles allowed the transfection in mammalian cells of a
reporter luciferase gene with an efficiency superior to the widely used cationic lipids.