Stoichiometric tapasin interactions in the catalysis of major histocompatibility complex class I molecule assembly
Stoichiometric tapasin interactions in the catalysis of major histocompatibility complex class I molecule assembly
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DOI：
10.1111/j.1365-2567.2005.02103.x
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发表时间：
2005-03-01
期刊：
影响因子：
6.4
通讯作者：
Cresswell, P
中科院分区：
文献类型：
--
作者：
Bangia, N;Cresswell, P
主要组织相容性复合物 (MHC) I 类分子及其肽配体在内质网 (ER) 中的组装需要许多蛋白质的帮助，这些蛋白质形成称为“肽装载复合物”的多分子组合体。 Tapasin 是该复合物的中心稳定剂，该复合物还包括与抗原加工 (TAP) 相关的转运蛋白、MHC I 类分子、ER 伴侣、钙网蛋白和硫醇氧化还原酶 ERp57。在本报告中，我们研究了这些相互作用对 tapasin 蛋白稳定性和 MHC I 类从肽负载复合物解离的要求。我们确定，在没有 TAP 或 MHC I 类相互作用的情况下，tapasin 是稳定的。在没有 TAP 的情况下，tapasin 与 MHC I 类分子的相互作用是长期存在的，并导致现有 tapasin 分子的隔离。相反，在 TAP 充足的细胞中，tapasin 被重新利用来与许多 MHC I 类分子相互作用并促进其顺序组装。此外，化学交联已被用来表征该复合物内的相互作用。我们证明了 tapasin 和 MHC I 类分子以 1:1 复合体存在，没有证据表明存在更高阶的 tapasin 多聚体。这些研究共同揭示了 tapasin 蛋白的生命周期以及它如何在 MHC I 类组装中与肽呈递给 CD8(+) T 细胞的功能。
The assembly of major histocompatibility complex (MHC) class I molecules with their peptide ligands in the endoplasmic reticulum (ER) requires the assistance of many proteins that form a multimolecular assemblage termed the 'peptide-loading complex'. Tapasin is the central stabilizer of this complex, which also includes the transporter associated with antigen processing (TAP), MHC class I molecules, the ER chaperone, calreticulin, and the thiol-oxidoreductase ERp57. In the present report, we investigated the requirements of these interactions for tapasin protein stability and MHC class I dissociation from the peptide-loading complex. We established that tapasin is stable in the absence of either TAP or MHC class I interaction. In the absence of TAP, tapasin interaction with MHC class I molecules is long-lived and results in the sequestration of existing tapasin molecules. In contrast, in TAP-sufficient cells, tapasin is re-utilized to interact with and facilitate the assembly of many MHC class I molecules sequentially. Furthermore, chemical cross-linking has been utilized to characterize the interactions within this complex. We demonstrate that tapasin and MHC class I molecules exist in a 1 : 1 complex without evidence of higher-order tapasin multimers. Together these studies shed light on the tapasin protein life cycle and how it functions in MHC class I assembly with peptide for presentation to CD8(+) T cells.