Tapasin-mediated retention and optimization of peptide ligands during the assembly of class I molecules
Tapasin-mediated retention and optimization of peptide ligands during the assembly of class I molecules
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DOI：
10.4049/jimmunol.165.1.322
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发表时间：
2000-07-01
影响因子：
4.4
通讯作者：
McCluskey, J
中科院分区：
文献类型：
--
作者：
Barnden, MJ;Purcell, AW;McCluskey, J
鼠 I 类 H-2K(b) 分子在 Tapasin 缺陷的 721.220 人类细胞中实现高水平表面表达。与野生型细胞中的行为相比，721.220细胞上表达的K-b分子更容易接受外源肽，经历更快的表面衰减，并且无法形成大分子肽负载复合物，因此它们被快速转运到细胞表面，反映了在没有负载复合物形成的情况下内质网保留机制的失败。尽管 K-b 分子未能共定位到 TAP 并快速流出到表面，但 K-b 仍然能够在没有塔帕辛的情况下呈递 TAP 依赖性肽。此外，从这些分子洗脱的肽的池测序揭示了其典型的 H-2K(b) 结合蛾的严格保守性。与从塔帕辛缺陷细胞表面纯化的 K-b 分子相关的肽的总回收率有所减少。在存在和不存在塔帕辛的情况下与 K-b 结合的肽的比较揭示了肽库的相当大的重叠。这些结果表明，在不存在与塔帕辛相互作用的情况下，K-b 分子无法与钙网蛋白和 TAP 组装，但它们仍然能够获得多种肽阵列。然而，这些肽中的很大一部分似乎不是最理想的，导致 K-b 复合物的细胞表面稳定性降低。总而言之，这些研究结果表明，tapasin 在 I 类负载复合物的形成中发挥着重要作用，该复合物在内质网中保留 I 类异二聚体，直到完成最佳配体选择。
The murine class I H-2K(b) molecule achieves high level surface expression in tapasin-deficient 721.220 human cells. Compared with their behavior in wild-type cells, K-b molecules expressed on 721.220 cells are more receptive to exogenous peptide, undergo more rapid surface decay, and fail to form macromolecular peptide loading complexes, As a result, they are rapidly transported to the cell surface, reflecting a failure of endoplasmic reticulum retention mechanisms in the absence of loading complex formation. Despite the failure of K-b molecules to colocalize to the TAP and their rapid egress to the fell surface, K-b is still capable of presenting TAP-dependent peptides in the absence of tapasin. Furthermore, pool sequencing of peptides eluted from these molecules revealed strict conservation of their canonical H-2K(b)-binding moth, There was a reduction in the total recovery of peptides associated with K-b molecules purified from the surface of tapasin-deficient cells. Comparison of the peptides bound to K-b in the presence and absence of tapasin revealed considerable overlap in peptide repertoire, These results indicate that in the absence of an interaction with tapasin, K-b molecules fail to assemble with calreticulin and TAP, yet they are still capable of acquiring a diverse array of peptides, However, a significant proportion of these peptides appear to be suboptimal, resulting in reduced cell surface stability of K-b complexes. Taken together, the findings indicate that tapasin plays an essential role in the formation of the class I loading complex, which retains class I heterodimers in the endoplasmic reticulum until optimal ligand selection is completed.