There are accumulating demands to efficiently deliver bioactive proteins into live cells. Development of methodologies to achieve this will benefit chemical biology studies analyzing and modulating cell functions. This may also have a therapeutic impact.
In this study, we designed a peptide to efficiently deliver bioactive proteins into cytosol by disrupting endosomal membrane. Amphipathic helical structure is widely shared among antimicrobial peptides and hemolytic peptides, which disrupt plasma membranes. By modifying sequences of natural hemolytic peptides, we have succeeded in creating a peptide (L17E), which has low cytotoxicity but has an enough ability of endosome disruption, yielding a marked cytosolic spread of endocytosed protein [1].
Endocyotosis plays a role in cellular uptake of biomacromolecules and pH reduction accompanies endosomal maturation. Numerous pH-sensitive peptides, polymers and liposomes have thus been designed that bring about perturbation of endosomal membranes at acidic pH. However, no apparent pH-sensitivity was observed for L17E. Alternatively, the preferential interaction of L17E with negatively charged membrane was suggested as a possible mechanism of the endosome disruption.
L17E showed significant stimulation of cytosolic release of endocytosed molecules, including polydextran (10 kDa), Cre recombinase (39 kDa) and IgGs (150-160 kDa). Moreover, an exogenous antibody, thus delivered with the help of this peptide, recognized its intracellular target. These results show the promise of L17E as a tool for intracellular delivery of bioactive proteins to exert their functions in cells.