title: Fate and action of ricin in rat liver in vivo: translocation of endocytosed ricin into cytosol and induction of intrinsic apoptosis by ricin B-chain.
abstract: Cytotoxicity of many plant and bacterial toxins requires their endocytosis and retrograde transport from endosomes to the endoplasmic reticulum. Using cell fractionation and immunoblotting procedures, we have assessed the fate and action of the plant toxin ricin in rat liver in vivo, focusing on endosome-associated events and induction of apoptosis. Injected ricin rapidly accumulated in endosomes as an intact A/B heterodimer (5-90 min) and was later (15-90 min) partially translocated to cytosol as A- and B-chains. Unlike cholera and diphtheria toxins, which also undergo endocytosis in liver, neither in cell-free endosomes loaded by ricin in vivo nor upon incubation with endosomal lysates did ricin undergo degradation in vitro. A time-dependent translocation of ricin across the endosomal membrane occurred in cell-free endosomes. Endosome-located thioredoxin reductase-1 was required for translocation as shown by its physical association with ricin chains and effects of its removal and inhibition. Ricin induced in vivo intrinsic apoptosis as judged by increased cytochrome c content, activation of caspase-9 and caspase-3, and enrichment of DNA fragments in cytosol. Furthermore, reduced ricin and ricin B-chain caused cytochrome c release from mitochondria in vivo and in vitro, suggesting that the interaction of ricin B-chain with mitochondria is involved in ricin-induced apoptosis.
authors.affiliation: Service information scientifique et technique (IST) de l'Inserm, Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Authier
authors.affiliation: Inserm U1218, Université de Bordeaux, Institut Bergonié, Bordeaux, France.
authors.forename: Mojgan
authors.initials: M
authors.lastname: Djavaheri-Mergny
authors.affiliation: Inserm UMR-S-1193, Université Paris-Saclay, 92296, Châtenay-Malabry, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Lorin
authors.affiliation: CNRS UMR 8601, Centre Universitaire des Saints-Pères, Université Paris-Descartes, Paris, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Frénoy
authors.affiliation: Inserm U 1016 and CNRS UMR 8104, Université Paris-Descartes, Institut Cochin, Paris, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Desbuquois
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D002458:Cell Fractionation; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D053938:DNA Fragmentation; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D011992:Endosomes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D015870:Gene Expression; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D055503:Protein Multimerization; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D012276:Ricin / Q000138:chemical synthesis / Q000493:pharmacokinetics* / Q000633:toxicity*; D054481:Thioredoxin Reductase 1 / Q000235:genetics / Q000378:metabolism
chemical_list: D045304:Cytochromes c; D012276:Ricin; D054481:Thioredoxin Reductase 1; C516126:Txnrd1 protein, rat; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9