Lambert Stacie L, Martinez Olivia M
Program in Immunology and Department of Surgery, Division of Transplantation, Stanford University, Stanford, CA 94305, USA.
J Immunol. 2007 Dec 15;179(12):8225-34. doi: 10.4049/jimmunol.179.12.8225.
EBV is a B lymphotrophic gamma-herpesvirus that is associated with multiple human malignancies, including posttransplant lymphoproliferative disorder. The EBV-encoded protein, latent membrane protein 1 (LMP1), is required for oncogenic transformation of human B cells by EBV. An important consequence of LMP1 expression in EBV-infected B cells is the induction of cellular IL-10, which acts as an autocrine growth factor for B cell lymphomas. However, the mechanisms by which LMP1 induces IL-10 are incompletely understood. We previously showed that rapamycin, a clinically relevant immunosuppressant and mammalian target of rapamycin inhibitor, could suppress IL-10 production by EBV-infected B cell lines. To test the hypothesis that PI3K, which acts upstream of mammalian target of rapamycin, might also be involved in LMP1-dependent IL-10 production, we generated B cell lines expressing signaling-inducible chimeric LMP1. Our results show that induced LMP1 signaling elicits both p38- and PI3K-dependent IL-10 production in EBV- B cells. Moreover, distinct regions of the LMP1 signaling tail are associated with p38- vs PI3K-dependent IL-10 induction. We also demonstrate that the LMP1-dependent p38 and PI3K activation regulates IL-10 induction through discrete mechanisms. Whereas p38 activation is critical for the phosphorylation of the transcription factor CREB, PI3K activation is required for the inactivation of glycogen synthase kinase 3beta (GSK3beta), an inhibitory kinase that can regulate CREB function. We find that GSK3beta regulates LMP1-dependent IL-10 induction, with GSK3beta inhibition by pharmacologic or small interfering RNA strategies enhancing LMP1-induced IL-10 induction. These findings demonstrate that LMP1 uses both p38 and PI3K activation for maximal up-regulation of IL-10.
EBV是一种嗜B淋巴细胞的γ疱疹病毒，与多种人类恶性肿瘤相关，包括移植后淋巴细胞增殖性疾病。EBV编码的蛋白潜伏膜蛋白1（LMP1）是EBV致人类B细胞发生致癌转化所必需的。LMP1在EBV感染的B细胞中表达的一个重要结果是诱导细胞产生白细胞介素10（IL-10），其作为B细胞淋巴瘤的自分泌生长因子。然而，LMP1诱导IL-10的机制尚未完全阐明。我们之前表明，雷帕霉素，一种临床相关的免疫抑制剂及雷帕霉素靶蛋白抑制剂，可抑制EBV感染的B细胞系产生IL-10。为了验证雷帕霉素靶蛋白上游的磷脂酰肌醇-3-激酶（PI3K）可能也参与LMP1依赖的IL-10产生这一假说，我们构建了表达信号诱导嵌合LMP1的B细胞系。我们的结果表明，诱导的LMP1信号在EBV阴性B细胞中引发p38和PI3K依赖的IL-10产生。此外，LMP1信号尾的不同区域与p38和PI3K依赖的IL-10诱导相关。我们还证明，LMP1依赖的p38和PI3K激活通过不同机制调节IL-10诱导。虽然p38激活对于转录因子CREB的磷酸化至关重要，但PI3K激活是糖原合酶激酶3β（GSK3β）失活所必需的，GSK3β是一种可调节CREB功能的抑制性激酶。我们发现GSK3β调节LMP1依赖的IL-10诱导，通过药理学或小干扰RNA策略抑制GSK3β可增强LMP1诱导的IL-10诱导。这些发现表明，LMP1利用p38和PI3K激活来最大程度地上调IL-10。
