Cell-surface proteoglycans as molecular portals for cationic peptide and polymer entry into cells

Abstract

Polycationic macromolecules and cationic peptides acting as PTDs (protein transduction domains) and CPPs (cell-penetrating peptides) represent important classes of agents used for the import and delivery of a wide range of molecular cargoes into cells. Their entry into cells is typically initiated through interaction with cell-surface HS (heparan sulfate) molecules via electrostatic interactions, followed by endocytosis of the resulting complexes. However, the endocytic mechanism employed (clathrin-mediated endocytosis, caveolar uptake or macropinocytosis), defining the migration of these peptides into cells, depends on parameters such as the nature of the cationic agent itself and complex formation with cargo, as well as the nature and distribution of proteoglycans expressed on the cell surface. Moreover, a survey of the literature suggests that endocytic pathways should not be considered as mutually exclusive, as more than one entry mechanism may be operational for a given cationic complex in a particular cell type. Specifically, the observed import may best be explained by the distribution and uptake of cell-surface HSPGs (heparan sulfate proteoglycans), such as syndecans and glypicans, which have been shown to mediate the uptake of many ligands besides cationic polymers. A brief overview of the roles of HSPGs in ligand internalization is presented, as well as mechanistic hypotheses based on the known properties of these cell-surface markers. The identification and investigation of interactions made by glycosaminoglycans and core proteins of HSPGs with PTDs and cationic polymers will be crucial in defining their uptake by cells.

Exogenous and Cell Surface Glycosaminoglycans Alter DNA Delivery Efficiency of Arginine and Lysine Homopeptides in Distinctly Different Ways

“…The release of DNA from the polyplexes on anionic challenge also corroborates this, as K 16 is more easily destabilized in the presence of anionic agents. 4 It has also been shown in the literature that arginine polypeptide binds with higher affinity to different glycosaminoglycans like heparan sulfate and chondroitin sulfate than lysine, as the guanidino group of arginine can form electrostatic interaction as well as hydrogen bonds with the sulfate groups in GAGs when compared with the ammonium cation of lysine (25,35). For a similar reason, arginine polypeptide also binds with higher affinity to a negatively charged polymer like DNA.…”

“…The transfection efficiency of R 16 in both the cell lines is higher than that of K 16 (which has been rationalized by us in an earlier study. 4 The control data in CHO-K1 in some of the experiments are adapted from Mann et al 4 The transfection efficiency changes only marginally for both the peptides in the two cell lines as shown in Fig. 1A.…”

Transport of Arylsulfatase A across the Blood-Brain Barrier in Vitro

“…nylated neomycin or the protein transduction domain of the trans-activator of transcription (TAT) protein of the human immunodeficiency virus (21,37).…”

Evaluation of Cell-Penetrating Peptide/Adenovirus Particles for Transduction of CAR-Negative Cells

“…Studies have also shown that the initial electrostatic interaction of CPPs with anionic cell membrane surfaces is an important factor for the uptake of all cationic CPP-cargo complexes (Deshayes, Morris et al 2005;Poon and Gariepy 2007). The presence of competing anionic material can limit the interaction…”