Tuning the size and solvent-exposed hydrophobicity of a pore-forming peptide eliminates its cytotoxicity using a natural product

Pore-forming toxins (PFTs) are a diverse group of peptides and proteins that interact with the cell membrane to form transmembrane pores which lead to to ion dyshomeostasis and cell death. Our previous work showed that claramine, an aminosterol derivative of cholesterol, protects brain and kidney cells from prototypical PFTs. This effect was not induced by a change in protein structure, but instead by incorporating into and changing the physico-chemical properties of the plasma membrane to prevent the binding of these toxins. In the search for compounds that can target the structures of PFTs directly to eliminate their toxicity, we found that the polyphenol epigallocatechin gallate (EGCG) directly interacts with the monomeric PFT melittin, the active component of honeybee venom, resulting in the elimination of its binding to the cell membrane and neutralization of its cytotoxicity. EGCG achieved this effect by lowering the solvent-exposed hydrophobicity of melittin and promoting its oligomerization into larger aggregates. These biophysical properties have also shown to play an important role in the membrane binding and associated cytotoxicity of misfolded protein oligomers implicit in neurodegenerative diseases. Our results show that this relationship translates to the attenuation of melittin cytotoxicity by EGCG. These findings emphasize the importance of the physico-chemical properties of PFTs in controlling their binding to cell membranes and suggest a potential mechanism for therapeutic development against PFTs.