A Molecular Basis for the Presentation of Phosphorylated Peptides by HLA-B Antigens
A Molecular Basis for the Presentation of Phosphorylated Peptides by HLA-B Antigens
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DOI：
10.1074/mcp.m116.063800
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发表时间：
2017-02-01
影响因子：
7
通讯作者：
Marcilla, Miguel
中科院分区：
文献类型：
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作者：
Alpizar, Adab;Marino, Fabio;Marcilla, Miguel
由于异常蛋白磷酸化是肿瘤细胞的标志，因此人类白细胞抗原 (HLA) I 类分子展示肿瘤特异性磷酸肽可用于通过基于 T 细胞的免疫疗法治疗癌症。然而，HLA-I 磷酸配体的表征和预测具有挑战性，因为此类翻译后修饰肽的呈现的分子决定因素尚未完全了解。在这里，我们采用肽组学工作流程来鉴定与 HLA-B* 40、-B*27、-B*39 或 -B*07 相关的 256 个独特磷酸化配体。值得注意的是，这些磷酸肽表现出相似的分子特征。除了每个同种异型的结合槽所施加的特定锚定基序之外，肽位置 4 (P4) 处的磷酸化优势变得非常明显，P1 处碱性残基的富集也是如此。为了确定这一观察结果的结构基础，我们进行了一系列肽结合测定，并解析了 HLA-B* 40 与磷酸化配体或其非磷酸化对应物复合物的晶体结构。总体而言，我们的数据为与不同 HLA-B 分子相关的磷酸肽组中发现的共同基序提供了清晰的解释。 P4 磷酸化的高发生率是由重链中保守残基 Arg62 的存在决定的，这是大多数 HLA-B 等位基因共有的结构特征。相反，对 P1 处碱性残基的偏好是同种异型依赖性的，并且可能与 A 口袋的结构有关。这种对 HLA-B 分子呈现磷酸肽的分子理解为改进磷酸化新抗原的预测和鉴定奠定了基础，可能用于癌症免疫治疗。
As aberrant protein phosphorylation is a hallmark of tumor cells, the display of tumor-specific phosphopeptides by Human Leukocyte Antigen (HLA) class I molecules can be exploited in the treatment of cancer by T-cell-based immunotherapy. Yet, the characterization and prediction of HLA-I phospholigands is challenging as the molecular determinants of the presentation of such post-translationally modified peptides are not fully understood. Here, we employed a peptidomic workflow to identify 256 unique phosphorylated ligands associated with HLA-B* 40, -B*27, -B*39, or -B*07. Remarkably, these phosphopeptides showed similar molecular features. Besides the specific anchor motifs imposed by the binding groove of each allotype, the predominance of phosphorylation at peptide position 4 (P4) became strikingly evident, as was the enrichment of basic residues at P1. To determine the structural basis of this observation, we carried out a series of peptide binding assays and solved the crystal structures of HLA-B* 40 in complex with a phosphorylated ligand or its nonphosphorylated counterpart. Overall, our data provide a clear explanation to the common motif found in the phosphopeptidomes associated to different HLA-B molecules. The high prevalence of phosphorylation at P4 is dictated by the presence of the conserved residue Arg62 in the heavy chain, a structural feature shared by most HLA-B alleles. In contrast, the preference for basic residues at P1 is allotype-dependent and might be linked to the structure of the A pocket. This molecular understanding of the presentation of phosphopeptides by HLA-B molecules provides a base for the improved prediction and identification of phosphorylated neo-antigens, as potentially used for cancer immunotherapy.