Multiple regions within the cytoplasmic domains of the leukemia inhibitory factor receptor and gp130 cooperate in signal transduction in hepatic and neuronal cells.
The receptor for leukemia inhibitory factor (LIFR), in combination with the signal-transducing subunit for interleukin-6-type cytokine receptors, gp130, and LIF, activates transcription of acute-phase plasma protein genes in human and rat hepatoma cells and the vasoactive intestinal peptide gene in a human neuroblastoma cell line. To identify the regions within the cytoplasmic domain of LIFR that initiate signal transduction independently of gp130, we constructed a chimeric receptor by linking the extracellular domain of the granulocyte colony-stimulating factor receptor (G-CSFR) to the transmembrane and cytoplasmic domain of human LIFR. The function of the chimeric receptor protein in transcriptional activation was assessed by G-CSF-mediated stimulation of cotransfected cytokine-responsive reporter gene constructs in hepatoma and neuroblastoma cells. By using the full-length cytoplasmic domain and mutants with progressive carboxy-terminal deletions, internal deletions, or point mutations, we identified the first 150 amino acid residues of LIFR as the minimal region necessary for signaling. The signaling reaction appears to involve a cooperativity between the first 70-amino-acid region containing the two sequence motifs conserved among hematopoietin receptors (box 1 and box 2) and a critical sequence between residues 141 and 150 (box 3). Analogous analyses of the cytoplasmic domains of G-CSFR and gp130 indicated similar arrangements of functional domains in these receptor subunits and the requirement of a box 3-related motif for signaling.
Baumann
H
H
Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263.
Symes
A J
AJ
Comeau
M R
MR
Morella
K K
KK
Wang
Y
Y
Friend
D
D
Ziegler
S F
SF
Fink
J S
JS
Gearing
D P
DP
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001483:Base Sequence; D002460:Cell Line; D050822:Cytokine Receptor gp130; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000235:genetics; D006131:Growth Inhibitors; D006801:Humans; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; D008099:Liver / Q000378:metabolism; D008222:Lymphokines; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009474:Neurons / Q000378:metabolism; D051381:Rats; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism*; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000235:genetics; D053606:Receptors, OSM-LIF; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation
D015703:Antigens, CD; D006131:Growth Inhibitors; C494199:IL6ST protein, human; C494201:Il6st protein, rat; D015850:Interleukin-6; C507837:LIF protein, human; C507840:LIFR protein, human; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; C507842:Lifr protein, rat; D008222:Lymphokines; D008562:Membrane Glycoproteins; D018121:Receptors, Cytokine; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D053606:Receptors, OSM-LIF; D011993:Recombinant Fusion Proteins; D050822:Cytokine Receptor gp130; D004247:DNA