Peptide-independent stabilization of MHC class I molecules breaches cellular quality control
Peptide-independent stabilization of MHC class I molecules breaches cellular quality control
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DOI：
10.1242/jcs.145334
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发表时间：
2014-07-01
影响因子：
4
通讯作者：
Boulanger, Denise
中科院分区：
文献类型：
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作者：
Hein, Zeynep;Uchtenhagen, Hannes;Boulanger, Denise
主要组织相容性复合体I类(MHC-I)蛋白的细胞内转运受三种质控机制的控制，这三种质控机制检测其结构完整性，这与高亲和力抗原肽配体的结合有关。为了研究这些质量控制机制检测到的MHC-I的哪些分子特征，我们遵循了这样的假设，即次优负载的MHC-I分子的特征是它们在肽结合位点的F口袋区域的构象迁移率。我们已经创造了一种新的MHC-I蛋白变体K-b-Y84C，其中该区域的两个α螺旋通过二硫键连接起来，模拟结合的高亲和力多肽的构象和动态效应。K-b-Y84C与其轻链-β-2微球蛋白(β(2)m)的结合亲和力显著增加，并绕过了所有三个细胞质量控制步骤。我们的数据表明：(1)多肽和β(2)m与MHC-I重链结合是由构象动力学介导的；(2)由β(2)m支持的MHC-I的折叠构象在通过内质网到细胞表面运输质量控制中起决定性作用；(3)β(2)m结合也受到导致MHC-I内吞的细胞表面质量控制的检验。
The intracellular trafficking of major histocompatibility complex class I (MHC-I) proteins is directed by three quality control mechanisms that test for their structural integrity, which is correlated to the binding of high-affinity antigenic peptide ligands. To investigate which molecular features of MHC-I these quality control mechanisms detect, we have followed the hypothesis that suboptimally loaded MHC-I molecules are characterized by their conformational mobility in the F-pocket region of the peptide-binding site. We have created a novel variant of an MHC-I protein, K-b-Y84C, in which two alpha-helices in this region are linked by a disulfide bond that mimics the conformational and dynamic effects of bound high-affinity peptide. K-b-Y84C shows a remarkable increase in the binding affinity to its light chain, beta-2 microglobulin (beta(2)m), and bypasses all three cellular quality control steps. Our data demonstrate (1) that coupling between peptide and beta(2)m binding to the MHC-I heavy chain is mediated by conformational dynamics; (2) that the folded conformation of MHC-I, supported by beta(2)m, plays a decisive role in passing the ER-to-cell-surface transport quality controls; and (3) that beta(2)m association is also tested by the cell surface quality control that leads to MHC-I endocytosis.