Large Molecules Transported into Living Cells

Our cell interior is protected from unwanted visitors by a cell membrane for a good reason. However, from a pharmacological point of view, this protection is a troublesome obstacle, as large proteins or antibodies find it difficult, if not impossible, to enter the so-called cytoplasm. Most drugs circumvent this barrier by targeting the cell surface. Meanwhile, making active ingredients cell-permeable remains one of the most pressing questions for biomedical research and the pharmaceutical industry.

Research into cell-penetrating peptides has been going on for more than two decades. This involves linking a protein or an antibody, for example, with a chemical or biochemical “tag” intended to facilitate its entry into the cell. But despite worldwide efforts, many of these approaches fail when it comes to transporting such large biomolecules.

The research team from Darmstadt and Berlin has taken a decisive step toward transporting even large molecules into the cell interior. The key finding: the researchers link the molecules not only to the cell-penetrating peptides but also the cell surface. As experiments on living cells showed, this significantly improves the intracellular uptake of functional proteins and antibodies. The results have just been published in the journal Nature Chemistry.

“This publication is the latest result of a joint funding proposal in DFG Priority Programme 1623 (Chemoselective Reactions for the Synthesis and Application of Functional Proteins) with the aim of developing novel functionalisation approaches of proteins and antibodies to make them cell-permeable, says Professor Dr. M. Cristina Cardoso from the Cell biology and epigenetics research group at the Department of Biology at TU Darmstadt. ”This is not only highly relevant for biological research, but also opens the doors for therapeutic targeting of intracellular components, which has been largely limited to small molecules with self-permeable properties. Our research group has contributed to the concept and biological applications, as well as to the analysis of cell permeation and viability."

A decisive factor in this success is that the new method requires only about one-tenth of the substance concentrations as before. This simplifies the method significantly, making it more robust and versatile.

The potential applications of cellular molecular transport are broad. Active cell-permeable proteins or antibodies can be used, for example, to influence signaling pathways in a cancer cell deliberately or to switch off cancer-driving gene mutations. Likewise conceivable is the replacement of a missing enzyme in the case of a hereditary disease, for example, or the use of gene editing—that is, the genetic manipulation of cells using ready-made proteins equipped with additional properties.

Leibniz-FMP/cst