Translocation of penetratin-like peptides involving calcium-dependent interactions between glycosaminoglycans and phosphocholine headgroups of the membrane lipid bilayer

Abstract

Cell-penetrating peptides (CPPs) can internalize ubiquitously in cells. To explore the specific targeting issue of CPPs, we studied glycosaminoglycan (GAG)-binding peptides previously identified in Otx2 and En2 homeoproteins (HPs), that preferentially recognize highly sulfated chondroitin (CS) and heparan (HS) GAGs, respectively. HPs internalize in specific cells thanks to their GAG-targeting sequence. We quantified the capacity of chimeric peptides between these two GAG-targeting peptides and a penetratin-like sequence, to enter into various cell lines known to express different levels and types of HS and CS GAGs. We also analyzed the binary and ternary interactions between heparin (HI), (4S, 6S)-CS (CS-E), zwitterionic phosphocholine (PC) model membranes and those chimeric peptides. Altogether, our results demonstrate the existence of Ca2+-dependent interactions between CS-E or HI and PC lipid bilayers, the major phospholipid headgroup found in animal cell plasma membrane. In addition, the interaction of CS-E (but not HI), with PC permits the binding of the chimeric CS-E-recognition motif-penetratin-like peptide and its subsequent crossing of the lipid membrane to access directly to the cytosol of cells. Altogether, this study brings further understanding of translocation mechanism of CPPs, which requires specific GAGs at the cell-surface. It also shed light on the role of GAGs in the cell transfer specificity and paracrine activity of HPs.