Open AccessPlasma membrane and intracellular pools of transferrin receptors decline during in vitro cultivation of U937 cells
Author(s) -
Salcedo T. W.,
Fleit H. B.
Publication year - 1991
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1991.tb01167.x
Subject(s) - transferrin receptor , transferrin , receptor , u937 cell , biology , biochemistry , intracellular , microbiology and biotechnology , cell surface receptor , monoclonal antibody , cell culture , in vitro , antibody , immunology , genetics
. Transferrin receptor expression in the monocyte‐like cell line U937 was investigated during in vitro cultivation. U937 cells expressed a single class of high affinity surface transferrin receptors (K d ≅ 4nm), with apparent subunit M, of 90–95 000 Da as determined by SDS‐reducing PAGE. [ 125 I]‐transferrin binding studies on detergent‐solubilized cells revealed that half to two‐thirds of the total functional binding sites were located intracellularly. Radioligand binding, immuno‐fluorescence and flow cytometry studies were performed on intact, detergent‐solubilized, or saponin‐permeabilized cells, using either transferrin or the anti‐transferrin receptor monoclonal antibody OKT9 IgG. These studies demonstrated that functional and antigenic transferrin receptor levels were maximal on cells 24 h after subculture at low density and declined during the culture period. Scatchard analysis of radioligand binding data suggested that the decline in functional transferrin binding sites resulted from a decline in the number of available receptors. These results demonstrate that in U937 cells there is a density‐dependent regulation of transferrin receptor expression, resulting in a loss of functional and antigenic receptors from both plasma membrane and intracellular locations.