Cell penetrating peptide POD mediates delivery of recombinant proteins to retina, cornea and skin

Recently we described a novel cell penetrating peptide, peptide for ocular delivery (POD) that could deliver small molecules including fluorescent dyes into retinal cells. The objective of the current study was to examine whether biologically relevant macromolecules such as proteins, genetically fused with POD could also be delivered into retinal tissues in vivo. We generated a POD–GFP fusion protein and examined its cell and tissue penetrating properties. We found that endogenously expressed POD–GFP fusion protein localized to the nucleus, suggesting that POD acts as a nuclear localization signal. Adenovirus (Ad) vectors expressing POD–GFP fusion protein were constructed and the recombinant protein was purified from Ad-infected human embryonic retinoblasts (HER). Exogenously supplied POD–GFP fusion protein rapidly transduced A549 and HER cells and colocalized in part with markers of late endosomes, from which it could escape. Following subretinal delivery, POD–GFP localized to the retinal pigment epithelium and the photoreceptor cell bodies. When injected into the vitreous, POD–GFP localized to the ganglion cells and the inner nuclear layer of the retina as well as the lens capsule. Topical application of POD–GFP to ocular surfaces resulted in uptake by the corneal epithelium. POD–GFP also transduced non-ocular tissues, including the epidermis of the skin following topical application.