Development of an inducible platform for intercellular protein delivery

A challenge to protein based therapies is the ability to produce biologically active proteins and their ensured delivery. Various approaches have been utilised including fusion of protein transduction domains with a protein or biomolecule of interest. A compounding issue is lack of specificity, efficiency and indeed whether the protein fusions are actually translocated into the cell and not merely an artefact of the fixation process. Here we present a novel platform, allowing the inducible export and uptake of a protein of interest. The system utilises a combination of the Tetracyline repressor system, combined with a fusion protein containing the N-terminal signal peptide from human chorionic gonadotropin beta-subunit, and a C-terminal poly-arginine domain for efficient uptake by target cells. This novel platform was validated using enhanced green fluorescent protein as the gene of interest. Doxycycline efficiently induced expression of the fusion protein. The human chorionic gonadotropin beta-subunit facilitated the export of the fusion protein into the cell culture media. Finally, the fusion protein was able to efficiently enter into neighbouring cells (target cells), mediated by the poly-arginine cell penetrating peptide. Importantly we have addressed the issue of whether the observed uptake is an artefact of the fixation process or indeed genuine translocation. In addition this platform provides a number of potential applications in diverse areas such as stem cell biology, immune therapy and cancer targeting therapies.