TAP-Dependent and -Independent Peptide Import into Dendritic Cell Phagosomes
TAP-Dependent and -Independent Peptide Import into Dendritic Cell Phagosomes
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DOI：
10.4049/jimmunol.1501925
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发表时间：
2016-11-01
影响因子：
4.4
通讯作者：
van Endert, Peter
中科院分区：
文献类型：
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作者：
Lawand, Myriam;Abramova, Anastasia;van Endert, Peter
被吞噬的Ag通过MHC I类（MHC-I）分子的交叉呈递被认为涉及由从内质网募集的TAP转运蛋白介导的胞质肽转运到树突状细胞吞噬体中。然而，由于难以获得纯的和紧密密封的吞噬体，肽转运到吞噬体中的直接证据仍然有限。此外，参数确定肽的吸收，并在吞噬体中的生存仍然很少的特点。在这项研究中，我们使用两种类型的荧光报告肽，其中一种直接结合到intraphagosomal珠通过流式细胞术监测肽进口到吞噬体。我们观察到具有高TAP亲和力的肽以TAP和ATP依赖性的方式输入吞噬体，如预期的那样。然而，令人惊讶的是，OVA肽SIINFEKL（一种经常用于研究交叉呈递的CD 8（+）T细胞表位）的输入是ATP依赖性的，但基本上是TAP非依赖性的。两种报告肽的半衰期通过TLR信号传导触发的增强的吞噬体成熟而缩短。相反，与MHC-I分子形成复合物增强了吞噬体中的肽积累。总的来说，这些结果证实了TAP可以将肽输入到吞噬体中，但它们表明一些肽，包括流行的SIINFEKL，也可以通过第二种未知的能量依赖性机制进入吞噬体。因此，经常报道的吞噬的OVA的交叉呈递的TAP依赖性可能主要反映了对再循环MHC-I分子的需要，而不是SIINFEKL通过TAP输入到吞噬体中。免疫学杂志，2016，197：3454-3463。
Cross-presentation of phagocytosed Ags by MHC class I (MHC-I) molecules is thought to involve transport of cytosolic peptides into dendritic cell phagosomes, mediated by TAP transporters recruited from the endoplasmic reticulum. However, because pure and tightly sealed phagosomes are difficult to obtain, direct evidence for peptide transport into phagosomes has remained limited. Moreover, the parameters determining peptide uptake by, and survival in, phagosomes remain little characterized. In this study, we monitored peptide import into phagosomes by flow cytometry using two types of fluorescent reporter peptides, one of which directly bound to intraphagosomal beads. We observed that a peptide with high TAP affinity is imported into phagosomes in a TAP- and ATP-dependent manner, as expected. However, surprisingly, import of the OVA peptide SIINFEKL, a CD8(+) T cell epitope frequently used to study cross-presentation, is ATP-dependent but substantially TAP-independent. The half-life of both reporter peptides is shortened by enhanced phagosome maturation triggered by TLR signaling. Conversely, formation of complexes with MHC-I molecules enhances peptide accumulation in phagosomes. Collectively, these results confirm that TAP can import peptides into phagosomes, but they suggest that some peptides, including the popular SIINFEKL, can enter phagosomes also via a second unknown energy-dependent mechanism. Therefore, the frequently reported TAP dependence of cross-presentation of phagocytosed OVA may principally reflect a requirement for recycling MHC-I molecules rather than SIINFEKL import into phagosomes via TAP. The Journal of Immunology, 2016, 197: 3454-3463.