Collaborative Research: Structure and Function of Direct Delivery Peptides

Non-technical description Every living cell is surrounded by a very thin membrane barrier that keeps most large and water-soluble molecules out of the cell. The membrane protects the cell, but it also makes it hard to deliver useful cargo molecules, such as drugs, into cells. Short molecules called cell penetrating peptides can sometimes carry cargo across this barrier, but most known examples work inefficiently and tend to trap their cargo inside internal compartments where the cargo cannot do its job. Recently, researchers discovered a new class of peptides that behave differently. These peptides can move directly across the cell membrane and deliver cargo molecules with much higher efficiency and without entrapment. The goal of this project is to understand how these unusual direct delivery peptides cross cell membranes and why they work better than earlier examples. The team studies how the peptides interact with the lipids that make up cell membranes and how the chemical complexity of real cell membranes affects the interactions. The team develops laboratory membrane systems that closely mimic natural cell membranes to study the interactions in detail. By uncovering the rules that allow peptides to cross membranes directly, this work helps scientists design new molecules to deliver useful cargos into cells. The project also supports the training of undergraduate and graduate students in interdisciplinary research and shares results through publications and outreach activities that introduce students to the science of cell membranes and biomaterials. Technical description The plasma membrane of a cell prevents most hydrophilic macromolecules from entering the cytosol. Classical cell penetrating peptides such as tat and penetratin can deliver these cargos, but they rely on endocytosis. This pathway is inefficient and often traps the cargo inside intracellular vesicles where they are degraded. Recently discovered direct delivery peptides perform much better and use a different mechanism. These peptides can deliver many kinds of cargo to the cytosol at low concentrations and with high efficiency. Current evidence suggests that they cross the plasma membrane by direct translocation, but the molecular basis of this process is still unclear. The goal of this project is to identify the peptide structural features and peptide–lipid interactions that allow efficient direct plasma membrane translocation. The central hypothesis of this work is that these peptides adopt flexible conformations that promote strong interactions between arginine side chains and lipid headgroups at the membrane surface, along with cooperative interactions involving aromatic residues. To test this idea, the team carries out systematic structure–activity and mechanistic studies that compare classical cell penetrating peptides with direct delivery peptides under the same experimental conditions. Plasma membrane lipids are isolated from plasma membrane–derived vesicles and used to build customizable lipid mixtures that reproduce the chemical complexity of biological membranes. The team measures peptide binding, translocation efficiency, structural dynamics, and peptide–lipid interactions in these systems and relate those properties to delivery activity. These studies define the molecular principles that allow efficient membrane translocation and guide the design of new peptide-based delivery materials that can transport a wide range of cargos into living cells. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2534517 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Myriam Cotten | Institution: Oregon State University, CORVALLIS, OR | Award Amount: $200,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2534517 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2534517.html