title: The endocytic uptake pathways of targeted toxins are influenced by synergistically acting Gypsophila saponins.
abstract: The expression of the epidermal growth factor (EGF) receptor is upregulated in many human tumors. We developed the targeted toxin SE, consisting of the plant toxin saporin-3 and human EGF. The cytotoxic effect of SE drastically increases in a synergistic manner by a combined treatment with Saponinum album (Spn), a saponin composite from Gypsophila paniculata L. Here we analyzed which endocytic pathways are involved in the uptake of SE and which are mandatory for the Spn-mediated enhancement. We treated HER14 cells (NIH-3T3 cells transfected with human EGF receptor) with either chlorpromazine, dynasore, latrunculin A, chloroquine, bafilomycin A1 or filipin and analyzed the effect on the cytotoxicity of SE alone or in combination with Spn. We demonstrated that SE in combination with Spn enters cells via clathrin- and actin-dependent pathways and the acidification of the endosomes after endocytosis is relevant for the cytotoxicity of SE. Notably, our data suggest that SE without Spn follows a different endocytic uptake pathway. SE cytotoxicity is independent of blocking of clathrin or actin, and the decrease in endosomal pH is irrelevant for SE cytotoxicity. Furthermore, Spn has no influence on the retrograde transport. This work is important for the better understanding of the underlying mechanism of Spn-enhanced cytotoxicity and helps to describe the role of Spn better.
authors: Institut für Laboratoriumsmedizin, Klinische Chemie und Pathobiochemie, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany.
authors: Diana
authors: D
authors: Bachran
authors: Stefanie
authors: S
authors: Schneider
authors: Christopher
authors: C
authors: Bachran
authors: Alexander
authors: A
authors: Weng
authors: Matthias F
authors: MF
authors: Melzig
authors: Hendrik
authors: H
authors: Fuchs
mesh_terms: D015153:Blotting, Western; D029748:Caryophyllaceae / Q000737:chemistry*; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004705:Endocytosis / Q000187:drug effects*; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D000922:Immunotoxins / Q000378:metabolism*; D008954:Models, Biological; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000922:Immunotoxins; D012503:Saponins