Transmembrane Targeting of DNA with Membrane Active Peptides

Abstract

Within recent years, the delivery of therapeutically active genes for the treatment of different diseases, such as cancer, and hereditary diseases, has become a major issue in the development of new therapies. In this case, DNA acts as a kind of pro-drug; it is completely inactive until it is translated into the therapeutically active protein within target cells by the cellular transcription/translation machinery. When applying such therapeutic genes into an organism, a manifold of hurdles has to be circumvented until the transgene reaches its final goal, the cells nucleus. The transgene has to bind to the cell’s surface, cross the plasma membrane, or become internalized into intracellular vesicles by endocytic mechanisms. In the latter case, release from intracellular compartments into the cytoplasm is an important step in order to prevent degradation of the transgene within lysosomes. In the case of mitotically active cells, reaching the cytoplasm is close to the final station in such a journey. During the next round of mitosis the nuclear membrane will be dismantled and thereafter the transgene incorporated into the nucleus during the next steps of the cell cycle. A further hurdle is awaiting the gene to be delivered in non- or only slowly dividing cells, since access to the nucleus is tightly controlled by the complex machinery of the nuclear pore complex. Viruses have developed clever mechanisms during their evolution to overcome these barriers and to deliver their own nucleic acid. Binding can occur via specific cell surface receptors, depending on host- and tissue type and trigger subsequent internalization or membrane fusion. Internalized virus particles can disrupt endosomal membranes (i.e. after certain viral proteins are activated by a change in the microenvironment within the intracellular vesicles). After reaching the cytoplasm, the utilization of other intracellular mechanism helps the virus to reach the nucleus (i.e. by carrying specific nuclear localization sequences).