title: Membrane destabilization by ricin.
abstract: Ricin is a promising candidate for the treatment of cancer because it can be selectively targeted to tumor cells via linkage to monoclonal antibodies. Biochemical evidence suggests that escape of ricin or its ribosome-inactivating subunit from an intracellular compartment is mediated by retrograde transport to the endoplasmic reticulum and subsequent direction into the ER-associated degradation pathway. Alternatively, lipase activity of ricin may facilitate leakage from endocytic vesicles. We have observed ricin-mediated release of macromolecular dyes from lipid vesicles that mimic the composition of endosomal membranes. Release of small molecules occurs to the same extent, suggesting an all-or-none mechanism due to bilayer destabilization. The level of accompanying membrane fusion depends on vesicle composition. Since it takes 24 h of incubation before the first traces of lysolipids are detectable by matrix-assisted laser desorption/ionization mass spectrometry, membrane destabilization is not due to the lipase activity of ricin.
authors.affiliation: Campus Berlin Buch, Forschungsinstitut für Molekulare Pharmakologie, Robert Roessle Str. 10, 13125 Berlin, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Sun
authors.forename: Elena E
authors.initials: EE
authors.lastname: Pohl
authors.forename: Oxana O
authors.initials: OO
authors.lastname: Krylova
authors.forename: Eberhard
authors.initials: E
authors.lastname: Krause
authors.forename: Igor I
authors.initials: II
authors.lastname: Agapov
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Tonevitsky
authors.forename: Peter
authors.initials: P
authors.lastname: Pohl
mesh_terms: D004058:Diffusion; D011992:Endosomes / Q000737:chemistry*; D005677:G(M1) Ganglioside / Q000737:chemistry*; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D010713:Phosphatidylcholines / Q000737:chemistry*; D016062:Porosity; D012276:Ricin / Q000737:chemistry*; D012996:Solutions
chemical_list: D008081:Liposomes; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D012996:Solutions; C021016:1,2-diphytanoylphosphatidylcholine; D005677:G(M1) Ganglioside; D012276:Ricin