Regulation of IL-6 Signaling by p53: STAT3- and STAT5-Masking in p53-Val135-Containing Human Hepatoma Hep3B Cell Lines

• Published in: The Journal of immunology (1950) Vol. 161; no. 1; pp. 325 - 334
• Main Authors: Rayanade, Ravi J, Ndubuisi, MacKevin I, Etlinger, Joseph D, Sehgal, Pravin B
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.07.1998
• Subjects: Amino Acid Substitution - genetics; Amino Acid Substitution - immunology; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - immunology; Cytokines - metabolism; Cytokines - physiology; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; Dose-Response Relationship, Immunologic; Epidermal Growth Factor - physiology; Humans; Interferon-gamma - physiology; Interleukin-6 - physiology; Milk Proteins; Mutation - immunology; Phenotype; Phosphatidylinositol Diacylglycerol-Lyase; Phosphorylation; Signal Transduction - drug effects; Signal Transduction - genetics; Signal Transduction - immunology; STAT3 Transcription Factor; STAT5 Transcription Factor; Temperature; Time Factors; Trans-Activators - physiology; Tumor Cells, Cultured; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - physiology; Type C Phospholipases - physiology; Tyrosine - metabolism; Valine - genetics
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.161.1.325

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.