title: Regulation of IL-6 signaling by p53: STAT3- and STAT5-masking in p53-Val135-containing human hepatoma Hep3B cell lines.
abstract: The influence of p53 on cytokine-triggered Janus kinase-STAT signaling was investigated in human hepatoma Hep3B cell lines engineered to constitutively express the temperature-sensitive Val135 mutant of p53. In comparison to the parental p53-free Hep3B cells, these p53-Val135-containing Hep3B cell lines displayed a reduced response to IL-6 at the wild-type-like p53 temperature (32.5 degrees C). In these cells, IL-6 induced a marked reduction in the immunologic accessibility of cytoplasmic and nuclear STAT3 and STAT5 within 20 to 30 min that lasted 2 to 4 h (STAT-masking) provided that the cells had been previously cultured at 32.5 degrees C for at least 18 to 20 h. The onset of IL-6-induced STAT-masking required protein tyrosine kinase, protein tyrosine phosphatase, proteasomal, phospholipase C, and mitogen-activated protein kinase kinase 1 activities. The maintenance of IL-6-induced STAT-masking was dependent on continued signaling through the phosphatidylinositol-dependent phospholipase C pathway. Despite a reduction in IL-6-induced STAT3 DNA binding activity in the nuclear compartment during STAT-masking, there was increased and prolonged accumulation of tyrosine-phosphorylated STAT3 in both the cytoplasmic and nuclear compartments, indicating that the capacity of tyrosine-phosphorylated STAT3 to bind DNA was reduced during STAT-masking. Thus, IL-6-induced STAT-masking, as dramatically evident on immunomicroscopy, is a visible consequence of a novel cellular process by which a p53-Val135-induced gene product(s) regulates the association of masking protein(s) with and the DNA-binding capacity of STAT3.
authors.affiliation: Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Rayanade
authors.forename: M I
authors.initials: MI
authors.lastname: Ndubuisi
authors.forename: J D
authors.initials: JD
authors.lastname: Etlinger
authors.forename: P B
authors.initials: PB
authors.lastname: Sehgal
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004306:Dose-Response Relationship, Immunologic; D004815:Epidermal Growth Factor / Q000502:physiology; D006801:Humans; D007371:Interferon-gamma / Q000502:physiology; D015850:Interleukin-6 / Q000502:physiology*; D008894:Milk Proteins; D009154:Mutation / Q000276:immunology; D010641:Phenotype; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010766:Phosphorylation; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D013696:Temperature; D013997:Time Factors; D015534:Trans-Activators / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D014633:Valine / Q000235:genetics*
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D008894:Milk Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D014443:Tyrosine; D004815:Epidermal Growth Factor; D007371:Interferon-gamma; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D014633:Valine