ABSTRACT
Cell penetrating peptides (CPPs) offer great potential to deliver therapeutic molecules to previously inaccessible intracellular targets. However, many CPPs are inefficient and often leave their attached cargo stranded in the cell's endosome. We report a versatile platform for the isolation of peptides delivering a wide range of cargos into the cytoplasm of cells. We used this screening platform to identify multiple "Phylomer" CPPs, derived from bacterial and viral genomes. These peptides are amenable to conventional sequence optimization and engineering approaches for cell targeting and half-life extension. We demonstrate potent, functional delivery of protein, peptide, and nucleic acid analog cargos into cells using Phylomer CPPs. We validate in vivo activity in the cytoplasm, through successful transport of an oligonucleotide therapeutic fused to a Phylomer CPP in a disease model for Duchenne's muscular dystrophy. This report thus establishes a discovery platform for identifying novel, functional CPPs to expand the delivery landscape of druggable intracellular targets for biological therapeutics.
Subject(s)
Cell-Penetrating Peptides/pharmacology , Drug Delivery Systems/methods , Drug Evaluation, Preclinical/methods , Animals , Bacteriophage T7 , Biotinylation , CHO Cells , Carbon-Nitrogen Ligases/genetics , Carbon-Nitrogen Ligases/metabolism , Cell-Penetrating Peptides/genetics , Cell-Penetrating Peptides/toxicity , Circular Dichroism , Cricetulus , Disease Models, Animal , Escherichia coli Proteins/genetics , Escherichia coli Proteins/metabolism , HEK293 Cells , Humans , Male , Mice, Inbred C57BL , Microscopy, Fluorescence , Muscular Dystrophy, Duchenne/drug therapy , Peptide Library , Repressor Proteins/genetics , Repressor Proteins/metabolismABSTRACT
The ability of cell penetrating peptides (CPPs) to deliver biologically relevant cargos into cells is becoming more important as targets in the intracellular space continue to be explored. We have developed two assays based on CPP-dependent, intracellular delivery of TEM-1 ß-lactamase enzyme, a functional biological molecule comparable in size to many protein therapeutics. The first assay focuses on the delivery of full-length ß-lactamase to evaluate the internalization potential of a CPP sequence. The second assay uses a split-protein system where one component of ß-lactamase is constitutively expressed in the cytoplasm of a stable cell line and the other component is delivered by a CPP. The delivery of a split ß-lactamase component evaluates the cytosolic delivery capacity of a CPP. We demonstrate that these assays are rapid, flexible and have potential for use with any cell type and CPP sequence. Both assays are validated using canonical and novel CPPs, with limits of detection from <500 nM to 1 µM. Together, the ß-lactamase assays provide compatible tools for functional characterization of CPP activity and the delivery of biological cargos into cells.
