Characterization and molecular features of the cell surface receptor for human granulocyte-macrophage colony-stimulating factor.
The receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF) on the surfaces of normal and leukemic myeloid cells were characterized using 125I-labeled bacterially synthesized GM-CSF. The binding was rapid, specific, time dependent, and saturable. Scatchard analysis of the 125I-GM-CSF binding to peripheral blood neutrophils indicated the presence of a single class of binding site (Kd = 99 +/- 21 pM; 2,304 +/- 953 sites/cell). However, for peripheral blood monocytes and two GM-CSF-responsive myeloid cell lines (U-937 and TF-1), the Scatchard plots were biphasic curvilinear, which were best fit by curves derived from two binding site model: one with high affinity (Kd1 = 10-40 pM) and the other with low affinity (Kd2 = 0.9-2.0 nM). For U-937 cells, the number of high-affinity receptors was 1,058 +/- 402 sites/cell and that of low-affinity receptors was estimated to be 10,834 +/- 2,396 sites/cell. Cross-linking studies yielded three major bands with molecular masses of 150 kDa, 115 kDa, and 95 kDa, which were displaced by an excess amount of unlabeled GM-CSF, suggesting 135-kDa, 100-kDa, and 80-kDa species for the individual components of the human GM-CSF receptor. These bands comigrated for different cell types including peripheral blood neutrophils, U-937 cells and TF-1 cells. In experiments using U-937 cells, only the latter two bands appeared to be labeled in a dose-dependent manner in a low-affinity state. These results suggest that the human GM-CSF receptor possibly forms a multichain complex.
Chiba
S
S
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Tojo
A
A
Kitamura
T
T
Urabe
A
A
Miyazono
K
K
Takaku
F
F
D001667:Binding, Competitive; D003115:Colony-Stimulating Factors / Q000378:metabolism*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D009504:Neutrophils / Q000032:analysis; D011956:Receptors, Cell Surface / Q000032:analysis*; D016184:Receptors, Colony-Stimulating Factor; D013696:Temperature; D014407:Tumor Cells, Cultured
D003115:Colony-Stimulating Factors; D006133:Growth Substances; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D016184:Receptors, Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor