Signal Transducers and Activators of Transcription 3 Augments the Transcriptional Activity of CCAAT/Enhancer-binding Protein α in Granulocyte Colony-stimulating Factor Signaling Pathway

• Published in: The Journal of biological chemistry 2005-04, Vol.280 (13), p.12621-12629
• Main Authors: Numata, Akihiko, Shimoda, Kazuya, Kamezaki, Kenjiro, Haro, Takashi, Kakumitsu, Haruko, Shide, Koutarou, Kato, Kouji, Miyamoto, Toshihiro, Yamashita, Yoshihiro, Oshima, Yasuo, Nakajima, Hideaki, Iwama, Atsushi, Aoki, Kenichi, Takase, Ken, Gondo, Hisashi, Mano, Hiroyuki, Harada, Mine
• Format: Article
• Language: English
• Subjects: Acute-Phase Proteins - metabolism; Animals; Blotting, Western; CCAAT-Enhancer-Binding Protein-alpha - metabolism; Cell Differentiation; Cell Line; Cell Proliferation; Cytokines - metabolism; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; Flow Cytometry; Gene Expression Regulation; Genes, Dominant; Granulocyte Colony-Stimulating Factor - metabolism; Granulocytes - cytology; Granulocytes - metabolism; Humans; Immunoblotting; Immunoprecipitation; Interferon-alpha - metabolism; Interleukin-3 - metabolism; Lipocalin-2; Lipocalins; Mice; Muramidase - chemistry; Muramidase - metabolism; Myeloid Cells - metabolism; Neutrophils - metabolism; Oligonucleotide Array Sequence Analysis; Oncogene Proteins - metabolism; Promoter Regions, Genetic; Proto-Oncogene Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - metabolism; Signal Transduction; STAT3 Transcription Factor; Time Factors; Trans-Activators - metabolism; Trans-Activators - physiology; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M408442200

The Janus kinase (Jak)-Stat pathway plays an essential role in cytokine signaling. Granulocyte colony-stimulating factor (G-CSF) promotes granulopoiesis and granulocytic differentiation, and Stat3 is the principle Stat protein activated by G-CSF. Upon treatment with G-CSF, the interleukin-3-dependent cell line 32D clone 3(32Dcl3) differentiates into neutrophils, and 32Dcl3 cells expressing dominant-negative Stat3 (32Dcl3/DNStat3) proliferate in G-CSF without differentiation. Gene expression profile and quantitative PCR analysis of G-CSF-stimulated cell lines revealed that the expression of C/EBPα was up-regulated by the activation of Stat3. In addition, activated Stat3 bound to CCAAT/enhancer-binding protein (C/EBP)α, leading to the enhancement of the transcription activity of C/EBPα. Conditional expression of C/EBPα in 32Dcl3/DNStat3 cells after G-CSF stimulation abolishes the G-CSF-dependent cell proliferation and induces granulocytic differentiation. Although granulocyte-specific genes, such as the G-CSF receptor, lysozyme M, and neutrophil gelatinase-associated lipocalin precursor (NGAL) are regulated by Stat3, only NGAL was induced by the restoration of C/EBPα after stimulation with G-CSF in 32Dcl3/DNStat3 cells. These results show that one of the major roles of Stat3 in the G-CSF signaling pathway is to augment the function of C/EBPα, which is essential for myeloid differentiation. Additionally, cooperation of C/EBPα with other Stat3-activated proteins are required for the induction of some G-CSF responsive genes including lysozyme M and the G-CSF receptor.