Dimerization of granulocyte-colony stimulating factor receptor: the Ig plus CRH construct of granulocyte-colony stimulating factor receptor forms a 2:2 complex with a ligand.
We have previously shown that the extracellular domain of granulocyte-colony stimulating factor receptor (soluble G-CSFR), prepared from CHO cell conditioned media, dimerizes upon binding its ligand, G-CSF. The most stable ligand-receptor complex occurs at a 2:2 stoichiometry, unlike the growth hormone and erythropoietin systems. In the latter cases, each ligand uses two sites to bring two receptors together. In this study, we have generated a truncated G-CSF receptor, known to be sufficient for high affinity ligand binding, which consists of an Ig-like domain and a cytokine receptor homology module. With an affinity purified receptor, sedimentation equilibrium experiments clearly demonstrated that this truncated form of the receptor behaves very similarly to the entire extracellular domain. The sedimentation equilibrium data are consistent with the model that the truncated receptor has a weak tendency to self-associate into a dimer in the absence of a ligand, this receptor-receptor interaction is enhanced by ligand binding, and the most stable complex occurs at a 2:2 stoichiometry. These results are very different from those described by others for various murine G-CSF receptor constructs from either Escherichia coli or insect expression systems.
Horan
T P
TP
Amgen Inc., Thousand Oaks, CA 91320, USA.
Martin
F
F
Simonet
L
L
Arakawa
T
T
Philo
J S
JS
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002850:Chromatography, Gel; D006224:Cricetinae; D019281:Dimerization; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008970:Molecular Weight; D011485:Protein Binding; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000737:chemistry* / Q000378:metabolism; D012995:Solubility
D007136:Immunoglobulins; D008024:Ligands; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D016179:Granulocyte Colony-Stimulating Factor