STAT3在抗病毒反應中所扮演的角色的研究

The Role of STAT3 in Antiviral Response

王偉蓓(Wei-Bei Wang)

指導教授 ： 李建國

國立臺灣大學/醫學院/免疫學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01607

摘要

在對抗病毒和細菌感染的先天性免疫反應(innate immunity)中，第一型干擾素(type I interferons; type I IFNs)是非常重要的細胞素(cytokine)之一。目前，己經有文獻報告指出IFN-a/b會活化STAT 蛋白質(signal transducer and activator transcription protein)家族中的STAT1，STAT2和STAT3。在基因剔除鼠的研究中證實，STAT1和STAT2對IFN-a/b所引起的抗病毒反應非常重要，但是目前對於STAT3在抗病毒機轉上扮演的角色並不清楚。本研究利用缺乏STAT3的巨噬細胞(macrophage)來探討STAT3在IFN-a/b引起的抗病毒反應中所扮演的角色。和對照組的BMM (bone marrow-derived macrophage)比較起來，在STAT3KO BMM中一些抗病毒相關的基因，例如IRF1(interferon regulatory factor 1)、IRF7 (interferon regulatory factor 7)和OAS (oligoadenylated synthetase)，其表現量經由IFN-a/b所誘導的效果比較差。同樣地，以類似病毒基因結構的poly (I:C)去刺激BMM，也發現IFN-a和PKR基因在STAT3KO的BMM中較對照組的BMM低。最後，本研究也利用Encephalomyocarditis virus (EMCV)這株病毒去感染巨噬細胞，以了解在缺乏STAT3的狀況下，IFN-a在細胞產生抗病毒的能力是否會受到影響。我們發現在低濃度血清的培養環境下，STAT3KO的BMM在受到EMCV感染後,即使在沒有IFN-a的前置處理下，細胞的存活率明顯的上升。然而，受EMCV感染的對照組和STAT3KO的BMM所產生的病毒效價(viral titer)卻是差不多的。相反的，在高濃度血清的培養環境下，受EMCV感染後的STAT3KO的PM，無論有沒有IFN-a 的前置處理，其cytopathic effect (CPE)比對照組細胞都來得嚴重，這些結果暗示著STAT3在IFN-a對於巨噬細胞所引起的抗病毒反應中可能扮演著重要角色。

關鍵字

干擾素 ； 巨噬細胞

並列摘要

Type I interferons (IFNs) are critical cytokines for innate immunity to combat viral and bacterial infections. It has been well documented that signal transducer and activator of transcription (STAT) proteins, such as STAT1, STAT2, and STAT3, are activated upon IFN-a/b stimulation. While essential roles of STAT1 and STAT2 in IFN-a/b-mediated antiviral responses are demonstrated in gene targeting mice, the role of STAT3 remains unclear. Using macrophages derived from STAT3-deficient mice, the role of STAT3 in IFN-a/b-mediated antiviral responses is investigated. An impaired induction of antivirus-associated genes, such as interferon regulatory factor 1 (IRF1), interferon regulatory factor 7 (IRF7), and oligoadenylate synthetase (OAS) was observed in bone marrow-derived macrophage (BMM) and peritoneal macrophage (PM) of STAT3KO mice compared to those of control mice in response to IFN-a/b. Likewise, induction of IFN-a and PKR genes was also reduced in STAT3KO BMM in response to poly (I:C), a chemical reagent mimicking viral infection. The effect of impaired IFN-a response of STAT3KO macrophage on antiviral response was further tested by infecting macrophage with encephalomyocarditis virus (EMCV). Under suboptimal infection conditions (reduced-serum conditions), STAT3KO BMM displayed an enhanced survival rate after EMCV infection without pretreatment of IFN-a. However, the viral titer of EMCV-infection control or STAT3KO macrophage was comparable. Under optimal infection conditions (high-serum conditions), an enhanced cytopathic effect (CPE) and viral titer were observed in PM of STAT3KO mice with or without pretreatment of different doses of IFN-a. Taken together, these results suggest an important and yet previously uncharacterized role of STAT3 in IFN-a-mediated antiviral responses in macrophage.

並列關鍵字

Macrophage ； Interferon ； STAT3

參考文獻

Akaishi,H., Takeda,K., Kaisho,T., Shineha,R., Satomi,S., Takeda,J., and Akira,S. (1998). Defective IL-2-mediated IL-2 receptor alpha chain expression in Stat3-deficient T lymphocytes. Int. Immunol. 10, 1747-1751.

Cooperation of Stat2 and p300/CBP in signalling induced by interferon-alpha. Nature 383, 344-347.

Bluyssen,H.A.R. and Levy,D.E. (1997). Stat2 is a transcriptional activator that requires sequence-specific contacts provided by Stat1 and p48 for stable interaction with DNA. J. Biol. Chem. 272, 4600-4605.

Clemens,M.J. (1997). PKR-A protein kinase regulated by double-stranded RNA. Int. J. Biochem. Cell Biol. 29, 945-949.

Clemens,M.J. and Elia,A. (1997). The double-stranded RNA-dependent protein kinase PKR: Structure and function. J. Interferon Cytokine Res. 17, 503-524.