title: Enhancing cellular uptake of GFP via unfolded supercharged protein tags.
abstract: One of the barriers to the development of protein therapeutics is effective delivery to mammalian cells. The proteins must maintain a careful balance of polar moieties to enable administration and distribution and hydrophobic character to minimize cell toxicity. Numerous strategies have been applied to this end, from appending additional cationic peptides to supercharging the protein itself, sometimes with limited success. Here we present a strategy that combines these methods, by equipping a protein with supercharged elastin-like polypeptide (ELP) tags. We monitored cellular uptake and cell viability for GFP reporter proteins outfitted with a range of ELP tags and demonstrated enhanced uptake that correlates with the number of positive charges, while maintaining remarkably low cytotoxicity and resistance to degradation in the cell. GFP uptake proceeded mainly through caveolae-mediated endocytosis and we observed GFP emission inside the cells over extended time (up to 48 h). Low toxicity combined with high molecular weights of the tag opens the way to simultaneously optimize cell uptake and pharmacokinetic parameters. Thus, cationic supercharged ELP tags show great potential to improve the therapeutic profile of protein drugs leading to more efficient and safer biotherapeutics.
authors.affiliation: Department of Polymer Chemistry, Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.
authors.forename: Diego
authors.initials: D
authors.lastname: Pesce
authors.forename: Yuzhou
authors.initials: Y
authors.lastname: Wu
authors.forename: Anke
authors.initials: A
authors.lastname: Kolbe
authors.forename: Tanja
authors.initials: T
authors.lastname: Weil
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
mesh_terms: D000595:Amino Acid Sequence; D016923:Cell Death; D045744:Cell Line, Tumor; D004549:Elastin / Q000737:chemistry / Q000378:metabolism; D004705:Endocytosis; D049452:Green Fluorescent Proteins / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D058767:Protein Unfolding; D011993:Recombinant Fusion Proteins / Q000378:metabolism*
chemical_list: D010455:Peptides; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D004549:Elastin