Chang Ya-Jen, Holtzman Michael J, Chen Ching-Chow
Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Mol Pharmacol. 2004 Mar;65(3):589-98. doi: 10.1124/mol.65.3.589.
The signaling pathway for IFN-gamma-mediated induction of ICAM-1 expression was further studied in human NCI-H292 epithelial cells. The Tyr701 phosphorylation of signal transducer and activator of transcription 1 (STAT1) induced by interferon-gamma (IFN-gamma) and 12-O-tetradecanoylphorbol 13-acetate (TPA) was inhibited by the protein kinase C (PKC) inhibitor staurosporine, the tyrosine kinase inhibitor herbimycin, or the Src kinase inhibitor PP2. An association between c-Src and STAT1 was increased by IFN-gamma and TPA, indicating the direct phosphorylation of STAT1 by PKC-dependent c-Src activation. Tyrosine phosphorylation of Janus kinases (JAK) 1/2 was induced by IFN-gamma but not by TPA. In addition, ICAM-1 promoter activity induced by IFN-gamma, but not that induced by TPA, was inhibited by the dominant-negative JAK1 and JAK2 mutants. IFN-gamma-induced tyrosine phosphorylation of phospholipase C (PLC)-gamma was inhibited by AG 490 (a JAK inhibitor), and the association between JAK1/2 and PLC-gamma was increased after IFN-gamma treatment, indicating the activation of PLC-gamma via JAK1/2 phosphorylation. ICAM-1 promoter activities induced by the overexpression of wild-type JAK1- and PLC-gamma2 were blocked by the PLCgamma2 mutant or the dominant-negative PKCalpha (Lys-->Arg), c-Src (Lys-->Met), or STAT1 (Y701M) mutants, but not by dominant-negative STAT3 (DN) mutants. These results confirmed that IFN-gamma activated PLC-gamma via JAK1/2 phosphorylation to induce PKC, c-Src, STAT1 activation, and ICAM-1 expression. The association between JAK1/2 and STAT1 was increased by IFN-gamma but not by TPA. It was inhibited by AG 490 but not by U73122, indicating the possible involvement of the JAK1/2-STAT1 pathway. All the results show that IFN-gamma induces ICAM-1 expression by two different pathways in NCI-H292 epithelial cells. One is the JAK1/2-dependent PLC-gamma pathway inducing the activations of PKCalpha, c-Src, and STAT1, and the other is the direct activation of STAT1 by JAK1/2.
在人NCI-H292上皮细胞中进一步研究了IFN-γ介导的ICAM-1表达诱导的信号通路。蛋白激酶C（PKC）抑制剂星形孢菌素、酪氨酸激酶抑制剂赫曲霉素或Src激酶抑制剂PP2可抑制干扰素-γ（IFN-γ）和12-O-十四酰佛波醇-13-乙酸酯（TPA）诱导的信号转导和转录激活因子1（STAT1）的Tyr701磷酸化。IFN-γ和TPA可增强c-Src与STAT1之间的关联，表明PKC依赖性c-Src激活可直接使STAT1磷酸化。IFN-γ可诱导Janus激酶（JAK）1/2的酪氨酸磷酸化，但TPA不能。此外，显性负性JAK1和JAK2突变体可抑制IFN-γ诱导的ICAM-1启动子活性，但不能抑制TPA诱导的活性。AG 490（一种JAK抑制剂）可抑制IFN-γ诱导的磷脂酶C（PLC）-γ的酪氨酸磷酸化，IFN-γ处理后JAK1/2与PLC-γ之间的关联增强，表明通过JAK1/2磷酸化激活PLC-γ。野生型JAK1和PLC-γ2过表达诱导的ICAM-1启动子活性被PLCγ2突变体或显性负性PKCalpha（Lys→Arg）、c-Src（Lys→Met）或STAT1（Y701M）突变体阻断，但不被显性负性STAT3（DN）突变体阻断。这些结果证实，IFN-γ通过JAK1/2磷酸化激活PLC-γ，从而诱导PKC、c-Src、STAT1激活和ICAM-1表达。IFN-γ可增强JAK1/2与STAT1之间的关联，但TPA不能。AG 490可抑制这种关联，但U73122不能，表明JAK1/2-STAT1途径可能参与其中。所有结果表明，IFN-γ在NCI-H292上皮细胞中通过两种不同途径诱导ICAM-1表达。一种是JAK1/2依赖性PLC-γ途径，诱导PKCalpha、c-Src和STAT1激活，另一种是JAK1/2直接激活STAT1。
