Multiple prolactin (PRL) receptor cytoplasmic residues and Stat1 mediate PRL signaling to the interferon regulatory factor-1 promoter.
The Nb2 PRL receptor (PRL-R) is known to mediate PRL signaling to the interferon (IFN) regulatory factor-1 (IRF-1) gene via the family of signal transducers and activators of transcription or Stats. To analyze the components of the PRL-R/Stat/IRF-1 signaling pathway, various PRL-R, Stat, and IRF-1-CAT reporter constructs were transiently cotransfected into COS cells. First, mutations in the IFNgamma-activated sequence (GAS), either multimerized or in the context of the 1.7-kb IRF-1 promoter, failed to mediate a PRL response, showing that the IRF-1 GAS is a target of PRL signaling. Next, pairwise alanine substitutions into conserved residues in the proline-rich motif or Box 1 region and two tyrosine mutations, Y308F and Y382F, in the PRL-R intracellular domain all impaired PRL signaling to multimerized GAS or to the 1.7-kb IRF-1 promoter. Furthermore, these PRL-R mutants mediated reduced Stat1 binding to the IRF-1 GAS. Transfection of Stat1 further enhanced PRL signaling to the IRF-1 promoter, suggesting that Stat1 is a positive mediator of PRL action. These studies show that both membrane proximal and distal residues of the PRL-R are involved in signaling to the IRF-1 gene. Further, Stat1 and the GAS element are important for PRL activation of the IRF-1 gene.
Wang
Y
Y
Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
O'Neal
K D
KD
Yu-Lee
L
L
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011981:Receptors, Prolactin / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D010750:Phosphoproteins; D011981:Receptors, Prolactin; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; D015534:Trans-Activators; D014443:Tyrosine; D007371:Interferon-gamma; D011388:Prolactin