title: Plasminogen-dependent internalization of soluble melanotransferrin involves the low-density lipoprotein receptor-related protein and annexin II.
abstract: We investigated the effect of plasminogen (Plg) on the internalization of recombinant soluble melanotransferrin (sMTf) using U87 human glioblastoma cells and murine embryonic fibroblasts (MEF) deficient in the low-density lipoprotein receptor-related protein (LRP). Using biospecific interaction analysis, both Glu- and Lys-Plg were shown to interact with immobilized sMTf. The binding of sMTf at the cell surface increased in the presence of both forms of Plg in control and in LRP-deficient MEF cells, whereas the uptake was strongly stimulated only by Lys-Plg in control MEF and U87 cells. In addition, in the presence of Lys-Plg, the internalization of sMTf was a saturable process, sensitive to temperature and dependent on the integrity of lysine residues. The addition of the receptor-associated protein, lactoferrin and aprotinin, as well as a monoclonal antibody (mAb) directed against LRP, inhibited the Lys-Plg-dependent uptake of sMTf. These results suggest an important role for LRP in this process. In addition, using binding and uptake assays in the presence of anti-annexin II mAb, we showed that annexin II might be responsible for the initial binding of sMTf in the presence of Plg. Our results suggest a Plg-mediated internalization mechanism for the clearance of sMTf via annexin II and LRP.
authors.affiliation: Laboratoire de Médecine Moléculaire, Service d'Hémato-Oncologie, Hôpital Ste-Justine, Université du Québec à Montréal, Montréal, Québec, Canada.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Michaud-Levesque
authors.forename: Michel
authors.initials: M
authors.lastname: Demeule
authors.forename: Richard
authors.initials: R
authors.lastname: Béliveau
mesh_terms: D000818:Animals; D017306:Annexin A2 / Q000378:metabolism*; D000951:Antigens, Neoplasm; D002460:Cell Line; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008239:Lysine / Q000378:metabolism; D058950:Melanoma-Specific Antigens; D051379:Mice; D018345:Mice, Knockout; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012995:Solubility
chemical_list: D017306:Annexin A2; D000951:Antigens, Neoplasm; D026502:LDL-Receptor Related Proteins; D008024:Ligands; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D011994:Recombinant Proteins; D010958:Plasminogen; D008239:Lysine