Histidine-367 of the human common beta chain of the receptor is critical for high-affinity binding of human granulocyte-macrophage colony-stimulating factor.
High-affinity receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 3, and interleukin 5 consist of ligand-specific alpha chains (low-affinity subunits) and a common beta chain (beta c) that converts each complex to a high-affinity form. Although beta c alone has no detectable cytokine-binding activity, amino acid substitutions for Glu-21 of human GM-CSF significantly reduce high-affinity but not low-affinity binding, implying that beta c interacts directly with GM-CSF during formation of the high-affinity receptor but only in the presence of the alpha chain. A potential GM-CSF-binding determinant was identified in the second hemopoietin domain of beta c, and the role of individual residues within this region was investigated by determining the ability of mutated beta c chains to confer high-affinity binding when coexpressed with the alpha subunit of the GM-CSF receptor in COS cells. Substitutions involving Met-363, Arg-364, Tyr-365, and Glu-366 did not affect high-affinity binding. However, substitution of His-367 by lysine or glutamine abolished high-affinity binding, suggesting that this residue may form an important part of the high-affinity GM-CSF-binding determinant. Consistent with the loss of high-affinity binding, higher concentrations of human GM-CSF were required to stimulate proliferation of CTLL-2 cell lines transfected with cDNAs for GM-CSF receptor alpha chain and His-367 beta c mutant than those expressing GM-CSF receptor alpha subunit and beta c wild type.
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Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
Metcalf
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Nicola
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D000595:Amino Acid Sequence; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000737:chemistry* / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D006639:Histidine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor