Sec61 blockade by mycolactone inhibits antigen cross-presentation independently of endosome-to-cytosol export
Sec61 blockade by mycolactone inhibits antigen cross-presentation independently of endosome-to-cytosol export
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DOI：
10.1073/pnas.1705242114
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发表时间：
2017-07-18
影响因子：
11.1
通讯作者：
Demangel, Caroline
中科院分区：
文献类型：
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作者：
Grotzke, Jeff E.;Kozik, Patrycja;Demangel, Caroline
尽管树突状细胞（DC）中的抗原交叉呈递对于大多数细胞毒性免疫应答的启动至关重要，但所涉及的细胞内机制和运输途径仍不清楚。在这个过程中最关键的步骤之一，出口的内化抗原的胞质溶胶，已被认为是由Sec61介导的。Sec61是将携带信号肽的新生多肽转运到内质网（ER）中的通道，并且还被提出在ER相关降解（称为ERAD的过程）期间介导蛋白质逆向转运。在这里，我们使用了一种新发现的Sec61阻滞剂，mycolactone，分析Sec61的贡献，抗原交叉呈递，ERAD，和运输的内化抗原进入胞质溶胶。如之前在其他细胞类型中所示，菌内酯阻止蛋白质输入DC的ER。Mycolactone介导的Sec61阻断也有效抑制抗原交叉呈递和合成肽直接呈递给CD8（+）T细胞。相反，它不影响蛋白质出口从内质网腔或从内体到胞质溶胶，这表明抑制交叉呈递是不相关的这些运输途径。菌内酯暴露的DC的蛋白质组学分析表明，抗原呈递介质的表达，包括MHC I类和β 2微球蛋白，对菌内酯处理高度敏感，表明Sec61阻断间接影响抗原交叉呈递。总之，我们的数据表明，有缺陷的易位和随后的降解Sec61基板是改变的抗原交叉呈递Sec61阻断的DC的原因。
Although antigen cross-presentation in dendritic cells (DCs) is critical to the initiation of most cytotoxic immune responses, the intracellular mechanisms and traffic pathways involved are still unclear. One of the most critical steps in this process, the export of internalized antigen to the cytosol, has been suggested to be mediated by Sec61. Sec61 is the channel that translocates signal peptide-bearing nascent polypeptides into the endoplasmic reticulum (ER), and it was also proposed to mediate protein retrotranslocation during ER-associated degradation (a process called ERAD). Here, we used a newly identified Sec61 blocker, mycolactone, to analyze Sec61's contribution to antigen cross-presentation, ERAD, and transport of internalized antigens into the cytosol. As shown previously in other cell types, mycolactone prevented protein import into the ER of DCs. Mycolactone-mediated Sec61 blockade also potently suppressed both antigen cross-presentation and direct presentation of synthetic peptides to CD8(+) T cells. In contrast, it did not affect protein export from the ER lumen or from endosomes into the cytosol, suggesting that the inhibition of cross-presentation was not related to either of these trafficking pathways. Proteomic profiling of mycolactone-exposed DCs showed that expression of mediators of antigen presentation, including MHC class I and beta 2 microglobulin, were highly susceptible to mycolactone treatment, indicating that Sec61 blockade affects antigen cross-presentation indirectly. Together, our data suggest that the defective translocation and subsequent degradation of Sec61 substrates is the cause of altered antigen cross-presentation in Sec61-blocked DCs.