Figure 22.

Overview of pathways utilized by cyclic CPPs to enter the cell. Left, some hydrophobic cyclic peptides have demonstrated ability to cross the plasma membrane by passive diffusion. Middle, other peptides can directly cross the plasma membrane by yet poorly defined mechanisms. A number of putative mechanisms including pore formation, carpet model, and inverted micelle have been put forward in the literature. Right, cyclic peptides are brough into the early endosome by various endocytic and pinocytic mechanisms and some of them efficiently escape the endosomal/lysosomal pathway into the cytosol.