Signal transduction mediated by growth hormone receptor and its chimeric molecules with the granulocyte colony-stimulating factor receptor.

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Abstract
The granulocyte colony-stimulating factor receptor (G-CSF-R) and growth hormone receptor (GH-R) belong to the cytokine receptor family and have some similarity in the cytokine receptor-homologous (CRH) domain of the extracellular region. Among members of this family, the G-CSF-R and GH-R seem to function as homodimers. Previously, we showed that mouse myeloid precursor FDC-P1 cells expressing the G-CSF-R can respond to G-CSF for growth. Here we show that the GH-R can also transduce the growth signal in FDC-P1 cells in the range 10 pM-100 nM GH. At a higher concentration of GH, GH did not promote the growth of the transformant cells. A series of chimeric receptor cDNAs between the G-CSF-R and GH-R cDNAs was constructed by exon swapping and was expressed in FDC-P1 cells. A ligand-binding assay with transformants expressing chimeric receptors indicated that the entire CRH domain is necessary for specific binding of the ligand. Although the transmembrane and cytoplasmic regions of the G-CSF-R and GH-R have no apparent similarity, these regions were interchangeable, resulting in growth-signal transduction in FDC-P1 cells.