Flagship 2: Programming peptides for bioavailability and localisation

Our Flagship 2 is striving toward the grand challenge of ensuring any peptide or protein can reach its intended biological target. In particular, our efforts are focussed on targeted peptide delivery strategies for optimal bioavailability.

Currently, it is not always clear why some peptides can enter cells while others cannot. A key goal for this Flagship is to understand the link between peptide structure and cell permeability. To this end, our researchers are developing enabling-technologies of labels and probes to aid in studying the cell membrane and the way it interacts with important biomolecules. Researchers within this Flagship work within our Decode and Develop themes.

Our researchers are using sophisticated techniques including live cell microscopy combined with fluorescent imaging to visualise peptides crossing the cell membrane. Additionally, peptide inhibitors, CRISPR knockouts and computer modelling techniques are being used to help determine specific features that are important for cell penetration and targeting. Our researchers are developing new Nuclear Magnetic Resonance (NMR) imaging methods and isotope labelling techniques to study specific peptide and protein interactions. There is an additional focus on features which allow peptides to escape from endosomal degradation to reach cytosolic targets, which are inspired by cell-penetrating cyclotides.

Researchers in this Flagship are using a lipidomics approach to decode the complexities of the phospholipid membrane. We are using mass spectrometry to study the lipid composition of the cell membrane, organelle membranes and extracellular vesicles. In addition to the lipid composition, biophysical properties of the cell membrane are being investigated including the overall charge (zeta potential) as well as lateral and transversal asymmetry of the membrane. These studies will help to determine how the lipid membrane composition and properties modulate peptide-cell membrane binding affinity, cell targeting of peptides and membrane permeability.

Once a peptide has entered a cell it is vital that we have a sophisticated toolkit of labels and sensors to visualise its behaviour and interactions. We are developing novel fluorescent tags for specific organelles which will enable observation of peptides in subcellular compartments and allow sensing of the local redox state and anion concentration. These sensing capabilities can give an indication of peptide function and organelle health. Affinity reagents are being developed to allow fluorescent tagging of molecules which bind specific post-translational modifications found on peptides and proteins to provide another level of detection of these biomolecules under physiological conditions. Additionally, bio- orthogonal fluorescent labelling strategies are being employed to visualise peptide or protein aggregates post-assembly.