Exosomal Interferon-Induced Transmembrane Protein 2 Transmitted to Dendritic Cells Inhibits Interferon Alpha Pathway Activation and Blocks Anti-Hepatitis B Virus Efficacy of Exogenous Interferon Alpha
Exosomal Interferon-Induced Transmembrane Protein 2 Transmitted to Dendritic Cells Inhibits Interferon Alpha Pathway Activation and Blocks Anti-Hepatitis B Virus Efficacy of Exogenous Interferon Alpha
复制标题
外泌体干扰素诱导的跨膜蛋白2传递至树突状细胞抑制干扰素α通路激活并阻断外源干扰素α的抗乙型肝炎病毒功效
作者：
Shi Ying;Du Lingyao;Lv Duoduo;Li Hong;Shang Jin;Lu Jiajie;Zhou Lingyun;Bai Lang;Tang Hong
干扰素（IFN）信号通路中的负调节因子抑制肝内免疫应答，导致慢性B型肝炎（CH B）患者对IFNα治疗的疗效欠佳。找出关键的负性因素，阐明其调控机制，是提高IFNα抗HBV（hepatitis B virus）疗效的关键。从基因表达综合数据库（GEO）中，我们下载并分析了对IFNα（GSE 54747）有不同反应的CHB患者的基因表达谱，发现先天免疫状态与CHB患者中基于IFNα的治疗反应相关。通过PCR阵列，我们发现IFN诱导的跨膜蛋白2（IFITM 2）mRNA的基线水平较高，IFNα治疗效果不佳的CHB患者外周血单个核细胞（PBMC）中IFNα mRNA的基线水平较低。IFNα无应答患者血清中IFITM 2蛋白水平也明显升高。通过进一步的实验，我们发现在Huh 7细胞中过表达IFITM 2通过抑制细胞外信号调节激酶（ERK）、TANK结合激酶1（TBK 1）和干扰素调节因子3（IRF 3）的磷酸化来抑制内源性IFNα合成;敲除IFITM 2增强了内源性IFNα合成途径的激活，表现出对HBV复制的更好抑制。我们还发现IFITM 2蛋白通过外泌体穿梭于树突状细胞（DCs），树突状细胞是内源性IFNα的主要来源。外泌体介导的IFITM 2转运抑制了DC中内源性IFNα的合成，而当IFITM 2被敲除时，抑制作用被消除。此外，我们证明了棕榈酰化抑制剂和IFITM 2蛋白70/71位点上的突变都会影响其掺入外泌体。结论：外泌体介导的IFITM 2转运至DC可抑制IFNα通路的激活，阻断外源性IFNα的抗HBV作用。这些发现为CHB患者对IFNα治疗的次优反应提供了解释。
The negative regulators in the interferon (IFN) signaling pathway inhibit intrahepatic immune response, resulting in suboptimal therapeutic response to IFNα treatment in chronic hepatitis B (CHB) patients. Identifying the key negative factors and elucidating the regulating mechanism are essential for improving anti‐HBV (hepatitis B virus) efficacy of IFNα. From the Gene Expression Omnibus (GEO) database, we downloaded and analyzed gene expression profiles of CHB patients with different responses to IFNα (GSE54747), and found that innate immune status was associated with the IFNα‐based therapeutic response in CHB patients. Through PCR array, we found higher baseline level of IFN‐induced transmembrane protein 2 (IFITM2) mRNA and lower baseline level of IFNα mRNA in peripheral blood mononuclear cells (PBMCs) of CHB patients with suboptimal response to IFNα treatment. Increased IFITM2 protein was also found in the serum of IFNα nonresponsive patients. With further experiments, we found that overexpressing IFITM2 in Huh7 cells suppressed endogenous IFNα synthesis by inhibiting phosphorylation of extracellular signal–regulated kinase (ERK), TANK‐binding kinase 1 (TBK1), and interferon regulatory factor 3 (IRF3); knocking out IFITM2 enhanced activation of the endogenous IFNα synthesis pathway, exhibiting better inhibition on HBV replication. We also found that IFITM2 protein was shuttled by exosomes to dendritic cells (DCs), the main source of endogenous IFNα. Exosome‐mediated transport of IFITM2 inhibited synthesis of endogenous IFNα in DCs whereas the inhibitory effect was abolished when IFITM2 was knocked out. Furthermore, we demonstrated that both palmitoylation inhibitor and mutation on 70/71 sites of IFITM2 protein influenced its incorporation into exosomes. Mutated IFITM2 protein increased the effect of IFNα against HBV.Conclusion:Exosome‐mediated transport of IFITM2 to DCs inhibits IFNα pathway activation and blocks anti‐HBV efficacy of exogenous IFNα. The findings provide an explanation to the suboptimal response of CHB patients to IFNα treatment.