HeLa cell entry by guanidinium-rich beta-peptides: importance of specific cation-cell surface interactions

Short cationic oligomers, including arginine-rich peptides and analogous beta-amino acid oligomers ("beta-peptides"), can enter the cytoplasm and nucleus of a living cell from the extracellular medium. It seems increasingly clear that multiple entry pathways are possible, depending upon the structure of the guanidinium-rich molecule, the type of cell, and other factors. We have previously shown that conformational stability and spatial clustering of guanidinium groups increase the HeLa cell entry efficiency of short helical beta-peptides bearing six guanidinium groups, results that suggest that these beta-peptides could be useful tools for studying the entry process. Here we describe studies intended to identify the point in the entry process at which helix stability and spatial arrangement of guanidinium groups exert their effect. Our results suggest that key distinctions involve the mode of interaction between different guanidinium-rich beta-peptides and the HeLa cell surface. A specific guanidinium display appears to be required for proper engagement of cell-surface heparan sulfate proteoglycans and concomitant induction of endocytic uptake.