title: Ricin-binding proteins along the endocytic pathway: the major endosomal ricin-binding protein is endosome-specific.
abstract: Ricin is internalized after binding at the cell surface via lectin activity of the B-chain recognizing terminal galactose residues. Ricin-A chain is then translocated to the cytosol from various endocytic structures. Cell death is the result of catalytic inactivation of protein synthesis. Using (125)I-ricin overlays, we examined the distribution of ricin binding-proteins within highly purified preparations of plasma membrane vesicles, endosomes and lysosomes from lymphocytes. All compartments of the endocytic pathway had distinct profiles; some ricin-binding proteins were present throughout the pathway; others were restricted to the plasma membrane and endosomes. The major endosomal protein recognized by (125)I-ricin, a 166 kDa glycoprotein, was endosome-specific. When endosomal proteins were solubilized before chromatography onto ricin-agarose this protein was also by far the major specifically-bound glycoprotein. This 166 kDa glycoprotein might be involved in ricin translocation from this compartment.
authors.affiliation: UMR 5539 CNRS, Département Biologie-Santé, Université Montpellier II, France.
authors.forename: M
authors.initials: M
authors.lastname: Alami
authors.forename: M P
authors.initials: MP
authors.lastname: Taupiac
authors.forename: B
authors.initials: B
authors.lastname: Beaumelle
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D011869:Radioligand Assay; D012276:Ricin / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D007457:Iodine Radioisotopes; D012276:Ricin