贝赫切特病相关 HLA-B*51:01 的肽组包括两个由内质网氨肽酶 1 差异形成的亚肽组。
The Peptidome of Behçet's Disease-Associated HLA-B*51:01 Includes Two Subpeptidomes Differentially Shaped by Endoplasmic Reticulum Aminopeptidase 1.
机构信息
CSIC, Centro de Biología Molecular Severo Ochoa, Madrid, Spain.
CSIC, Madrid, Spain.
出版信息
Arthritis Rheumatol. 2016 Feb;68(2):505-15. doi: 10.1002/art.39430.
OBJECTIVE
To characterize the peptidome of the Behçet's disease-associated HLA-B*51:01 allotype as well as the differential features of major peptide subsets and their distinct endoplasmic reticulum aminopeptidase 1 (ERAP-1)-mediated processing.
METHODS
The endogenous B51:01-bound peptidome was characterized from 721.221 transfectant cells, after affinity chromatography and acid extraction, by tandem mass spectrometry. Recombinant ERAP-1 variants were used to digest synthetic B51:01 ligands. HLA and transporter associated with antigen processing (TAP) binding affinities of peptide ligands were calculated with well-established algorithms. ERAP-1 and ERAP-2 from 721.221 cells were characterized by genomic sequencing and Western blotting.
RESULTS
The B51:01 peptidome consisted of 29.5% octamers, 61.7% nonamers, 4.8% decamers, and 4.0% longer peptides. The major peptide motif consisted of Pro and Ala at position 2, aliphatic/aromatic position 3 residues, and Val and Ile at the C-terminal position. The ligands with Pro or Ala at position 2 constituted 2 distinct subpeptidomes. Peptides with Pro at position 2 showed higher affinity for B51:01 and lower affinity for TAP than those with Ala at position 2. Most important, both peptide subsets differed drastically in the susceptibility of their position 1 residues to ERAP-1, revealing a distinct influence of this enzyme on both subpeptidomes, which may alter their balance, affecting the global affinity of B*51:01-peptide complexes.
CONCLUSION
ERAP-1 has a significant influence on the B51:01 peptidome and its affinity. This influence is based on very distinct effects on the 2 subpeptidomes, whereby only peptides in the subpeptidome with Ala at position 2 are extensively destroyed, except when their position 1 residues are ERAP-1 resistant. This pattern provides a mechanism for the epistatic association of ERAP-1 and B51:01 in Behçet's disease.
目的
描述与 Behcet 病相关的 HLA-B*51:01 同种异型的肽组特征，以及主要肽亚组的差异特征及其独特的内质网氨肽酶 1（ERAP-1）介导的加工。
方法
通过串联质谱法，从经过亲和层析和酸提取的 721.221 转染细胞中，对内源性 B51:01 结合肽组进行了特征描述。使用重组 ERAP-1 变体消化合成的 B51:01 配体。使用成熟的算法计算 HLA 和抗原加工相关转运体（TAP）结合亲和力肽配体。通过基因组测序和 Western 印迹对 721.221 细胞中的 ERAP-1 和 ERAP-2 进行了特征描述。
结果
B51:01 肽组由 29.5%的八聚体、61.7%的九聚体、4.8%的十聚体和 4.0%的更长肽组成。主要肽基序由位置 2 的 Pro 和 Ala、位置 3 的亲脂/芳族残基以及位置 3 的 Val 和 Ile 组成。位置 2 为 Pro 或 Ala 的配体构成了 2 个不同的亚肽组。位置 2 为 Pro 的肽与 B51:01 具有更高的亲和力，与 TAP 的亲和力低于位置 2 为 Ala 的肽。最重要的是，这两个肽亚组在其位置 1 残基对 ERAP-1 的易感性上差异很大，这表明该酶对这两个亚肽组都有明显的影响，这可能会改变它们的平衡，从而影响 B*51:01-肽复合物的整体亲和力。
结论
ERAP-1 对 B51:01 肽组及其亲和力有重大影响。这种影响基于对 2 个亚肽组的非常不同的影响，只有位置 2 为 Ala 的亚肽组中的肽被广泛破坏，除非它们的位置 1 残基对 ERAP-1 具有抗性。这种模式为 ERAP-1 和 Behcet 病中的 B51:01 之间的上位关联提供了一种机制。
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