Identification and characterization of a novel cell-penetrating peptide of 30Kc19 protein derived from Bombyx mori

•The first cell-penetrating peptide derived from 30Kc19 protein in hemolymph of B. mori.•This “Pep-c19” efficiently delivered cell-impermeable cargo proteins, such as GFP into cells.•Pep-c19 successfully delivered cargo proteins into various organ tissues with high efficiency.•No toxicity was seen for Pep-c19.•Pep-c19 has a great potential for use as a therapeutic tool to efficiently deliver cargos.

Cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) have attracted increasing attention due to their high potential to deliver various, otherwise impermeable, bioactive agents, such as drugs and proteins across cell membranes. A number of CPPs have been discovered since then. Recently, 30Kc19 protein has attracted attention because it was the first cell-penetrating protein that has been found in insect hemolymph. Here, we report a cell-penetrating peptide derived from 30Kc19 protein, VVNKLIRNNKMNC, which efficiently penetrates cells when supplemented to medium for mammalian cell culture. Moreover, like other CPPs, this “Pep-c19” also efficiently delivered cell-impermeable cargo proteins, such as green fluorescent protein (GFP) into cells. In addition to the in vitro system, Pep-c19 exhibited the cell-penetrating property in vivo. When Pep-c19 was intraperitoneally injected into mice, Pep-c19 successfully delivered cargo proteins into various organ tissues with higher efficiency than the 30Kc19 protein itself, and without toxicity. Our data demonstrates that Pep-c19 has a great potential as a cell-penetrating peptide that can be used as a therapeutic tool to efficiently deliver different cell-impermeable cargo molecules into the tissues of various organs.