Activating point mutations in the common beta subunit of the human GM-CSF, IL-3 and IL-5 receptors suggest the involvement of beta subunit dimerization and cell type-specific molecules in signalling.
We have combined retroviral expression cloning with random mutagenesis to identify two activating point mutations in the common signal-transducing subunit (h beta c) of the receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3 and IL-5 by virtue of their ability to confer factor independence on the haemopoietic cell line, FDC-P1. One mutation (V449E) is located within the transmembrane domain and, by analogy with a similar mutation in the neu oncogene, may act by inducing dimerization of h beta c. The other mutation (I374N) lies in the extracellular, membrane-proximal portion of h beta c. Neither of these mutants, nor a previously described mutant of h beta c (FI delta, which has a small duplication in the extracellular region), was capable of inducing factor independence in CTLL-2 cells, while only V449E could induce factor independence in BAF-B03 cells. These results imply that the extracellular and transmembrane mutations act by different mechanisms. Furthermore, they imply that the mutants, and hence also wild-type h beta c, interact with cell type-specific signalling molecules. Models are presented which illustrate how these mutations may act and predict some of the characteristics of the putative receptor-associated signalling molecules.
Jenkins
B J
BJ
Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Frome Road, Adelaide, SA, Australia.
D'Andrea
R
R
Gonda
T J
TJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D017931:DNA Primers; D005786:Gene Expression Regulation; D006412:Hematopoietic Stem Cells; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000235:genetics*; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000235:genetics*; D016185:Receptors, Interleukin-3 / Q000096:biosynthesis / Q000235:genetics*; D053649:Receptors, Interleukin-5; D011994:Recombinant Proteins / Q000096:biosynthesis; D015398:Signal Transduction; D014162:Transfection
D017931:DNA Primers; D046911:Macromolecular Substances; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D018123:Receptors, Interleukin; D016185:Receptors, Interleukin-3; D053649:Receptors, Interleukin-5; D011994:Recombinant Proteins