Rayanade R J, Ndubuisi M I, Etlinger J D, Sehgal P B
Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595, USA.
J Immunol. 1998 Jul 1;161(1):325-34.
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.
在经基因工程改造以组成性表达温度敏感型p53 Val135突变体的人肝癌Hep3B细胞系中，研究了p53对细胞因子触发的Janus激酶-信号转导和转录激活因子（JAK-STAT）信号传导的影响。与不含p53的亲本Hep3B细胞相比，这些含有p53-Val135的Hep3B细胞系在野生型样p53温度（32.5℃）下对白细胞介素-6（IL-6）的反应减弱。在这些细胞中，如果细胞先前在32.5℃下培养至少18至20小时，IL-6在20至30分钟内可诱导细胞质和细胞核中的信号转导和转录激活因子3（STAT3）及信号转导和转录激活因子5（STAT5）的免疫可及性显著降低，持续2至4小时（STAT屏蔽）。IL-6诱导的STAT屏蔽的起始需要蛋白酪氨酸激酶、蛋白酪氨酸磷酸酶、蛋白酶体、磷脂酶C和丝裂原活化蛋白激酶激酶1的活性。IL-6诱导的STAT屏蔽的维持依赖于通过磷脂酰肌醇依赖性磷脂酶C途径的持续信号传导。尽管在STAT屏蔽期间核区室中IL-6诱导的STAT3 DNA结合活性降低，但在细胞质和核区室中酪氨酸磷酸化的STAT3的积累增加且延长，这表明在STAT屏蔽期间酪氨酸磷酸化的STAT3结合DNA的能力降低。因此，如免疫显微镜下显著可见的，IL-6诱导的STAT屏蔽是一种新的细胞过程的明显结果，通过该过程p53-Val135诱导的基因产物调节屏蔽蛋白与STAT3的结合以及STAT3的DNA结合能力。
