Development of antibacterial agents and materials

Division Of Basic Sciences - Nci

Investigators

Linked publications & trials

Abstract

We designed a new class of CPPs whose ability to perturb cellular membranes is coupled to an enzyme-mediated shift in the folding potential of the peptide into its bioactive conformation. Cancer cells rich in negatively-charged surface components that also highly express alkaline phosphatase (ALP) are susceptible to the action of these peptides. Our peptide, DVD-1P, contains an N-terminal region with an (AB)n repeat of hydrophilic and hydrophobic residues followed by a central -DPP- motif that reverses the direction of the main chain Importantly, the C-terminal region of DVD-1P contains a negatively-charged phosphorylated Tyr that disrupts an otherwise ideal second (AB)n repeat. This disruption in amphiphilicity keeps the peptide unfolded and inactive until it is presented to dephosphorylating enzymes. Removal of the phosphate restores amphiphilicity and shifts the conformational bias of the peptide towards hairpin folding, which is ultimately achieved when it binds to negatively-charged components displayed from the surface of cells. We showed that DVD-1P preferentially lyses cells with efficacies that match the cellular expression levels of ALP. The mechanistic fate of the peptide can be further tuned by peptide concentration to affect cell-penetrating properties. When cells are treated with sub-lytic concentrations of DOX-funtionalized DVD-1P, the peptide delivers the drug into cells with efficacies dependent on ALP expression levels. Overall, this work shows that it is possible to affect selective MLPs action by directing their folding with spatial resolution. We also investigated whether cancer cells could gain resistance to linear MLPs. Although resistance toward small-molecule drugs has been well studied, the potential of tumor cells to gain resistance to lytic peptides remained largely unexplored. Our work is the first to show that eukaryotic cells can indeed develop resistance to MLPs. Using fission yeast, we identified three different loss-of-function gene mutations that conferred resistance to SVS-1, and found similar mechanisms operating in mammalian cancer cells. Interestingly, both organisms developed resistance by altering their cell-surface glycans to reduce the electrostatic charge at the cell surface. This reduced peptide accumulation and folding at the cell surface, conferring resistance.