title: Protection of cells from complement-mediated attack: CD59 receptor clustering for the entry of macromolecules into hematopoietic cells.
abstract: CD59 is a glycosylphosphatidylinositol anchored protein (GPI-protein) that is expressed on surface membranes to protect host cells from complement-mediated attack. CD59 may also serve as a receptor for the endocytosis of macromolecules into nucleated cells. Here we investigate the effects of primary clustering of CD59 with anti-CD59 monoclonal antibody and the secondary clustering of biotinylated anti-CD59 with avidin on red blood cells and erythroleukemic K562 cells. On red blood cells, CD59-targeted antibodies remained evenly distributed on the external membranes. In contrast, clustering, capping and endocytosis of the CD59-targeted complexes was detected on K562 cells. Secondary clustering appeared more efficient and resulted in endosomal localization of the fluorescently labeled complexes within 2 hours. The endocytosis of CD59-bound complexes did not affect K562 cell viability or growth and the surface level of CD59 was constant during the process. These result suggest clustering and subsequent endocytosis of CD59 may enable the entry of macromolecules to the endosomal compartments of hematopoietic cells.
authors.affiliation: Laboratory of Chemical Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: U
authors.initials: U
authors.lastname: Wojda
authors.forename: J
authors.initials: J
authors.lastname: Njoroge
authors.forename: J
authors.initials: J
authors.lastname: Miller
mesh_terms: D018957:CD59 Antigens / Q000378:metabolism*; D002455:Cell Division; D002470:Cell Survival; D003165:Complement System Proteins / Q000276:immunology*; D004705:Endocytosis / Q000502:physiology*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D046911:Macromolecular Substances; D011940:Receptor Aggregation; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D018957:CD59 Antigens; D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D003165:Complement System Proteins