Structural Dissection of Epsin‐1 N‐Terminal Helical Peptide: The Role of Hydrophobic Residues in Modulating Membrane Curvature

Abstract

Spatiotemporal structural alterations in cellular membranes are the hallmark of many vital processes. In these cellular events, the induction of local changes in membrane curvature often plays a pivotal role. Many amphiphilic peptides are able to modulate membrane curvature, but there is little information on specific structural factors that direct the curvature change. Epsin‐1 is a representative protein thought to initiate invagination of the plasma membrane upon clathrin‐coated vesicles formation. Its N‐terminal helical segment (EpN18) plays a key role in inducing positive membrane curvature. This study aimed to elucidate the essential structural features of EpN18 in order to better understand general curvature‐inducing mechanisms, and to design effective tools for rationally controlling membrane curvature. Structural dissection of peptides derived from EpN18 revealed the decisive contribution of hydrophobic residues to (i) enhancing membrane interactions, (ii) helix structuring, (iii) inducing positive membrane curvature, and (iv) loosening lipid packing. The strongest effect was obtained by substitution with leucine residues, as this EpN18 analog showed a marked ability to promote the influx of octa‐arginine cell‐penetrating peptides into living cells.

Hydrophobicity: The door to drug delivery

“…The critical role played by hydrophobic residues in improving membrane interactions and conformational structuring, in inducing positive membrane curvature, and in loosening lipid packing has been demonstrated in numerous examples of structural analysis of peptide sequences that have been reported in the literature. 38 These examples are crucial to understanding the impact of the peptide on the membrane and their potential exploitation. 38 Clearly, when we talk about drug delivery, we are looking for peptides that are not toxic to cells and should not damage the membrane; in fact, when membrane interactions become too strong, a membrane-interacting peptide can transform into a harmful membranolytic one.…”

“…38 These examples are crucial to understanding the impact of the peptide on the membrane and their potential exploitation. 38 Clearly, when we talk about drug delivery, we are looking for peptides that are not toxic to cells and should not damage the membrane; in fact, when membrane interactions become too strong, a membrane-interacting peptide can transform into a harmful membranolytic one. Several interactions must be considered to insert into the membrane.…”

“…98 The right balance of positive charges and hydrophobicity is necessary for an efficient and safe translocation, whereas too much hydrophobicity or positive charges can cause membrane lysis. 36,38…”

“…The ability of peptides to cause positive membrane curvature and perturb the packing of membrane lipids is clearly correlated not only to hydrophobicity but also to the secondary structure. The critical role played by hydrophobic residues in improving membrane interactions and conformational structuring, in inducing positive membrane curvature, and in loosening lipid packing has been demonstrated in numerous examples of structural analysis of peptide sequences that have been reported in the literature 38 . These examples are crucial to understanding the impact of the peptide on the membrane and their potential exploitation 38 .…”