posted on 2016-11-28, 00:00authored bySamuel Schmidt, Merel J. W. Adjobo-Hermans, Robin Kohze, Thilo Enderle, Roland Brock, Francesca Milletti
Cell-penetrating
peptides (CPPs) enhance the cellular uptake of
membrane-impermeable molecules. Most CPPs are highly cationic, potentially
increasing the risk of toxic side effects and leading to accumulation
in organs such as the liver. As a consequence, there is an unmet need
for less cationic CPPs. However, design principles for effective CPPs
are still missing. Here, we demonstrate a design principle based on
a classification of peptides according to accumulated side-chain polarity
and hydrophobicity. We show that in comparison to randomly selected
peptides, CPPs cover a distinct parameter space. We designed peptides
of only six to nine amino acids with a maximum of three positive charges
covering this property space. All peptides were tested for cellular
uptake and subcellular distribution. Following an initial round of
screening we enriched the collection with short and hydrophobic peptides
and introduced d-amino acid substitutions and lactam bridges
which increased cell uptake, in particular for long-term incubation.
Using a GFP complementation assay, for the most active peptides we
demonstrate cytosolic delivery of a biologically active cargo peptide.