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The granulocyte colony‐stimulating factor (G‐CSF) receptor has a composite structure consisting of an immunoglobulin(Ig)‐like domain, a cytokine receptor‐homologous (CRH) domain and three fibronectin type III (FNIII) domains in the extracellular region. Introduction of G‐CSF receptor cDNA into IL‐3‐dependent murine myeloid cell line FDC‐P1 and pro‐B cell line BAF‐B03, which normally do not respond to G‐CSF, enabled them to proliferate in response to G‐CSF. On the other hand, expression of the G‐CSF receptor cDNA in the IL‐2‐dependent T cell line CTLL‐2 did not enable it to grow in response to G‐CSF, although G‐CSF could transiently stimulate DNA synthesis. Mutational analyses of the G‐CSF receptor in FDC‐P1 cells indicated that the N‐terminal half of the CRH domain was essential for the recognition of G‐CSF, but the Ig‐like, FNIII and cytoplasmic domains were not. The CRH domain and a portion of the cytoplasmic domain of about 100 amino acids in length were indispensable for transduction of the G‐CSF‐triggered growth signal.

Three cDNAs for the human granulocyte colony-stimulating factor (G-CSF) receptor were isolated from the cDNA libraries of human U937 leukemia cells and placenta by using a murine G-CSF receptor cDNA as the probe. The human G-CSF receptor containing 813 amino acids had a marked homology (62.5%) with its murine counterpart and consisted of extracellular, transmembrane, and cytoplasmic domains. The WSXWS motif found in members of the newly identified growth factor receptor family was also present in the extracellular domain of the human G-CSF receptor.

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