Identification and characterization of receptors for granulocyte colony-stimulating factor on human placenta and trophoblastic cells.
Since radioiodination of human granulocyte colony-stimulating factor (G-CSF) is difficult, we synthesized a mutein of human G-CSF that retains full biological activity and receptor-binding capacity for at least 2 weeks after radioiodination. Receptors for human G-CSF were characterized in the plasma membrane fraction from the human term placenta (human placental membranes) and trophoblastic cells by using the 125I-labeled mutein of human G-CSF (KW-2228). The specific binding of 125I-labeled KW-2228 to placental membranes was pH-dependent, with maximal specific binding at pH 7.8; it increased linearly with protein to 3.7 mg of protein per ml and was both time- and temperature-dependent, with maximal binding at 4 degrees C after a 24-hr incubation. When we examined the ability of hematopoietic growth factors to inhibit 125I-labeled KW-2228 binding, we found that KW-2228 and intact human G-CSF inhibited 125I-labeled KW-2228 binding, whereas erythropoietin or granulocyte-macrophage colony-stimulating factor did not. Scatchard analysis revealed a single receptor type with a Bmax of 210 fmol/mg of protein and a Kd of 480 pM. The human G-CSF receptors on human placental membranes were shown to consist of two molecular species of 150 kDa and 120 kDa that could be specifically cross-linked to 125I-labeled KW-2228. Human trophoblastic cells, T3M-3, also possessed a single receptor for G-CSF with a Bmax of 533 receptors per cell and a Kd of 390 pM. Thus we have identified the receptor for human G-CSF on human placental membranes and trophoblastic cells, and the presence of this receptor in these membranes suggests that human G-CSF plays some role in the feto-placental unit during human development.
Uzumaki
H
H
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Okabe
T
T
Sasaki
N
N
Hagiwara
K
K
Takaku
F
F
Tobita
M
M
Yasukawa
K
K
Ito
S
S
Umezawa
Y
Y
D001667:Binding, Competitive; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003115:Colony-Stimulating Factors / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D005260:Female; D016179:Granulocyte Colony-Stimulating Factor; D006801:Humans; D007700:Kinetics; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D014327:Trophoblasts / Q000378:metabolism*
D003115:Colony-Stimulating Factors; D011956:Receptors, Cell Surface; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D016179:Granulocyte Colony-Stimulating Factor; D004247:DNA