Preferential uptake of L- versus D-amino acid cell-penetrating peptides in a cell type-dependent manner

The use of protease-resistant D-peptides is a prominent strategy for overcoming proteolytic sensitivity in the use of cell-penetrating peptides (CPPs) as delivery vectors. So far, no major differences have been reported for the uptake of L- and D-peptides. Here we report that cationic L-CPPs are taken up more efficiently than their D-counterparts in MC57 fibrosarcoma and HeLa cells but not in Jurkat T leukemia cells. Reduced uptake of D-peptides co-occurred with persistent binding to heparan sulfates (HS) at the plasma membrane. In vitro binding studies of L- and D-peptides with HS indicated similar binding affinities. Our results identify two key events in the uptake of CPPs: binding to HS chains and the initiation of internalization. Only the second event depends on the chirality of the CPP. This knowledge may be exploited for a stereochemistry-dependent preferential targeting of cells.