Cytotoxic activity of designed peptides based on the human erythropoietin sequence

grantor: University of TorontoIn this study, we set out to develop a general method for designing antagonists of helical cytokines. Our method involved grafting short amphipathic segments of a helical cytokine, which contained biologically important residues, onto a helical scaffold to produce a 3-helix bundle with molten globule structure. Erythropoietin (EPO) was used as a model cytokine. Six potential antagonist peptides were designed, synthesized and found to possess the expected helical and molten globular characteristics. However, they lacked specific antagonist activity and did not bind the soluble EPO receptor (EPOR). The designed peptides showed an unexpected cytotoxicity which appeared to be acting through necrosis. Surprisingly, the regions of EPO grafted onto the scaffold, which confer cytotoxicity, correspond to the EPOR-binding sites of EPO. Therefore, it appears that the sequence encoding the receptor-binding sites of EPO also encodes cytotoxic activity when isolated and presented in a helical conformation.M.Sc