Redistribution of cell surface transferrin receptors prior to their concentration in coated pits as revealed by immunoferritin labels

• Published in: Cell and tissue research 1986-01, Vol.244 (3), p.613-619
• Main Author: Cheng, T P
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal; Biological and medical sciences; Cell Line; Cell receptors; Cell structures and functions; Coated Pits, Cell-Membrane - metabolism; Coated Pits, Cell-Membrane - ultrastructure; Endosomes - metabolism; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Humans; Leukemia; Leukemia, Erythroblastic, Acute; Microscopy, Electron; Molecular and cellular biology; Receptors, Cell Surface - metabolism; Receptors, Transferrin; T-Lymphocytes - metabolism; T-Lymphocytes - ultrastructure; Transferrin - metabolism
• ISSN: 0302-766X; 1432-0878
• DOI: 10.1007/BF00212541

Immunocytochemistry has been used to study distribution of cell surface transferrin receptors in erythroid, leukemic (K562) cells. The cells were fixed and labelled with monoclonal (OKT-9) anti-transferrin receptor antibodies; the antibody-labelled receptors were then detected by either immunofluorescein- or immunoferritin-antimouse-antibody conjugates. Typically, the immunoferritin labels were distributed diffusely at the non-coated regions of the cell surface as well as concentrated in the clathrin-coated pits. To examine further this pattern of distribution, cells were labelled at 0 degrees C and then warmed to 37 degrees C for zero to 30 min prior to fixation. The majority of the immunoferritin labels were initially dispersed in small groups at the non-coated regions of the cell surface (mean = 6 immunoferritin labels/cluster), but larger groups were common subsequent to incubation at 37 degrees C (mean = 13 immunoferritin labels/cluster). However, the size of immunoferritin labels in the coated pits was unchanged (mean = 12 immunoferritin labels/pit). Immunoferritin labels were typical in coated and uncoated vesicles 1 min after warming to 37 degrees C, but common in endosomes, multivesicular bodies and lysosomes by 30 min. It appears that single cell-surface receptors form large aggregates prior to their concentration in coated pits. Coated vesicles, uncoated vesicles, and endosomal vacuoles may together form the non-lysosomal compartment where the internalized receptors might be dissociated from the ligands (antibodies).