Production of soluble granulocyte colony-stimulating factor receptors from myelomonocytic cells.
It has been speculated that a soluble form of G-CSFR might be physiologically present in humans, since G-CSFR mRNA that lacks a transmembrane domain has been identified from a human myelomonocytic cell line. Here, we demonstrate human soluble G-CSFR (sG-CSFR) of two different molecular sizes (80 and 85 kDa) on an immunoblot analysis using Abs generated against the amino-terminal, extracellular domain of the full-length G-CSFR. Both isoforms of sG-CSFR were able to bind recombinant human G-CSF (rhG-CSF). RT-PCR analysis with primers targeted outside of the transmenbrane region revealed that membrane-anchored G-CSFR is expressed at all maturation stages of purified myeloid cells, including CD34+CD13+ cells (blasts), CD11b-CD15+ cells (promyelocytes or myelocytes), CD11b+CD15+ cells (metamyelocytes and mature neutrophils), and CD14+ cells (monocytes). On the other hand, sG-CSFR mRNA was detectable in CD11b-CD15+, CD11b+CD15+, and CD14+ cells, but not in the CD34+CD13+ blast population. The serum concentration of both isoforms of sG-CSFR appeared to be correlated with the numbers of neutrophils/monocytes before and after rhG-CSF treatment in normal individuals. Thus, two isoforms of sG-CSFR are physiologically secreted from relatively mature myeloid cells and might play an important role in myelopoiesis through their binding to serum G-CSF.
Iwasaki
H
H
First Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Shimoda
K
K
Okamura
S
S
Otsuka
T
T
Nagafuji
K
K
Harada
N
N
Ohno
Y
Y
Miyamoto
T
T
Akashi
K
K
Harada
M
M
Niho
Y
Y
D000595:Amino Acid Sequence; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D006801:Humans; D007958:Leukocyte Count; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000096:biosynthesis / Q000097:blood / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012995:Solubility
D020033:Protein Isoforms; D012333:RNA, Messenger; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D011994:Recombinant Proteins