title: Effect of the anti-receptor ligand-blocking 225 monoclonal antibody on EGF receptor endocytosis and sorting.
abstract: The anti-receptor antibody, 225 mAb, is known to block binding of ligand to the epidermal growth factor receptor (EGFR). However, the effect of this neutralizing antibody on EGFR endocytosis, trafficking and degradation remains unclear. Here, we demonstrate that endocytosis of (125)I-225 mAb occurs, albeit with a slower rate than that of EGF. Using pulse chase assays, we show that internalized (125)I-225 mAb is recycled to the surface much more efficiently than internalized (125)I-EGF. Also, we found that internalization of (125)I-225 mAb, in contrast to that of EGF, is independent of receptor tyrosine kinase activity, as evidenced by its insensitivity to AG1478, a specific EGFR tyrosine kinase inhibitor. Analysis of the levels of cell surface and total EGFR showed that treatment with 225 mAb results in a 30-40% decrease in surface EGFR and a relatively slow downregulation of total EGFR. Taken together, these data indicate that 225 mAb induces internalization and downregulation of EGFR via a mechanism distinct from that underlying EGF-induced EGFR internalization and downregulation.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, Quebec, Canada H4P 2R2. maria.jaramillo@nrc.ca
authors.forename: Maria L
authors.initials: ML
authors.lastname: Jaramillo
authors.forename: Zully
authors.initials: Z
authors.lastname: Leon
authors.forename: Suzanne
authors.initials: S
authors.lastname: Grothe
authors.forename: Beatrice
authors.initials: B
authors.lastname: Paul-Roc
authors.forename: Abedelnasser
authors.initials: A
authors.lastname: Abulrob
authors.forename: Maureen
authors.initials: M
authors.lastname: O'Connor McCourt
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism* / Q000494:pharmacology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004705:Endocytosis; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007700:Kinetics; D008024:Ligands; D008168:Lung / Q000166:cytology / Q000378:metabolism; D008954:Models, Biological; D011485:Protein Binding; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D008024:Ligands; D066246:ErbB Receptors