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The influence of net charge and charge distribution on cellular uptake and cytosolic localization of arginine-rich peptides

Properties of different arginine-rich peptides, including net charge and charge distribution, were evaluated for their influence on surface binding, internalization, and intracellular localization. The peptides were radiolabeled and subsequently tested for surface binding and internalization in CHO-K1 cells. Subcellular fractionation assays were performed to separate the amount of peptides associated within vesicles from those inside the cytosol. Net neutral charged peptides, YGR6E6 and YG(RE)6, showed large decreases in both surface binding and cell uptake compared to their net positive charged counterparts, YGR6G6 and YG(RG)6. The peptides with clustered arginine residues, YGR6G6 and YGR6E6, exhibited significantly higher binding and uptake than those with alternating arginine and glycine/glutamate residues, YG(RG)6 and YG(RE)6. The intracellular distribution analysis for all of the peptides tested showed that, regardless of the net uptake, the arginine-rich peptides were preferentially localized in the cytosolic compartment of the cells. Both net positive charge and a clustered arginine sequence enhance the surface binding and internalization of peptides; however, the cytosolic versus vesicular intracellular distribution does not change. The results presented in this report provide important information regarding the specificity of binding and internalization of arginine-rich peptides, which is necessary for the future design of targeted drug delivery systems.