Molecular Basis of T Cell Recognition of Metal Ions

 描述（由申请方提供）：我们将在结构水平上研究人类T细胞对铍（Be 2+）和镍（Ni 2+）金属离子超敏反应的机制，并在人类受试者中证实这些机制。虽然有证据表明这些金属离子通过与自身肽预复合的MHC分子呈递给病理性T细胞，但对金属离子如何结合MHC、金属/MHC复合物如何被T细胞识别以及这些过程如何在人类中调节知之甚少。慢性铍病（CBD）是一种使人衰弱的肺部疾病，主要由工作场所暴露于空气中的Be 2+引起。该疾病与MHCII等位基因高度相关，特别是HLA-DP 2（DP 2），其在β链螺旋中的氨基酸69处具有Glu。我们的合作者发现，在人类肺部， 对Be 2+的应答主要由那些带有V β 5.1和各种T细胞受体（TCR）α链的受体所控制，所有受体都识别相同的DP 2/肽/Be 2+复合物。使用AV 22 TCR，我们发现非常小的Be 2+阳离子深埋在柔性P5-P7口袋中，并通过DP 2-肽表面构象的局部变化间接影响TCR结合。为了确定这种机制是否可推广到其他TCR-MHC相互作用，我们将测试Be 2+的这种灵活呈递是否适用于AV 22对具有其他自身肽的Be 2 +/DP 2的识别，以及与AV 22无关的TCR。Ni 2+是接触性皮炎的最常见原因，影响10-15%的人口，并且还涉及对金属植入物的反应，例如膝关节和髋关节置换。在这里，特定的TCR V基序也与有限的MHC阵列相互作用。在皮肤中，我们已经表明V β 17 T细胞如Ani2.3 T细胞克隆识别与HLA-DR 52 c（DR 52 c）-自身肽复合物结合的Ni 2+。我们的数据强烈表明，大的Ni 2+阳离子是表面暴露在这个复杂的，形成了一个主要的接触面积的TCR。Ni 2+似乎与被Be 2+接合的MHCII的相同区域结合，即在结合的肽和MHCII β链之间的空间中。我们将通过对与MHCII/肽/Ni 2+结合的各种Ni 2+特异性TCR的结构研究来测试这一想法，并确认在由于镍致敏而导致金属植入物失效的患者的血液中发现的Ni 2+反应性TCR的存在。目的1为了阐明HLA-DP 2/Be 2+呈递给T细胞的机制，我们将确定Be 2+是否会间接地通过DP 2-自身肽表面的构象变化影响V β 5.1 TCR，AV 22的接合，并确定DP 2/肽/Be 2+如何被结构上与AV 22无关的TCR，即携带V β 3.1的TCR，RP 11。目的2为了阐明MHCII/Ni 2+呈递给T细胞的机制，我们将定义和表征V β 17 TCR ANi2.3的Ni 2+依赖性肽，确定Ni 2+是否以与DR 52 c相同的方式结合DR 1，以及DR 1/肽/Ni 2 +/SE 9（另一种V β 17 TCR）相互作用类似于DR 52 c/肽/Ni 2 +/ANi2.3的相互作用，并分析由于镍致敏而导致关节植入物失效的患者血液中的Ni 2+特异性T细胞。了解金属离子在这些相互作用中的作用将揭示金属诱导的免疫疾病的机制，并可能有助于开发可以调节这种相互作用的化合物。

 DESCRIPTION (provided by applicant): We will study the mechanisms of human T cell hypersensitivity to beryllium (Be2+) and nickel (Ni2+) metal ions at the structural level, and confirm these mechanisms in human subjects. While evidence suggests that these metal ions are presented to pathologic T cells by an MHC molecule pre-complexed with a self-peptide, little is known about how the metal ions bind MHC, how the metal/MHC complexes are recognized by T cells, and how these processes are modulated in humans. Chronic beryllium disease (CBD) is a debilitating lung disease principally caused by workplace exposure to airborne Be2+. The disease is highly associated with MHCII alleles, particularly HLA-DP2 (DP2), that have a Glu at amino acid 69 in the ß chain helix. Our collaborators found that in human lungs, the T cell response to Be2+ is dominated by those bearing Vß5.1 with various T cell receptor (TCR) a chains, all recognizing an identical DP2/peptide/ Be2+ complex. Working with the AV22 TCR, we found that the very small Be2+ cation is buried deep in a flexible P5-P7 pocket, and influences TCR binding indirectly via local changes in the DP2-peptide surface conformation. With the goal of determining whether this mechanism is generalizable to other TCR-MHC interactions, we will test whether this flexible presentation of Be2+ applies to recognition by AV22 of Be2+/DP2 with other self- peptides, and to TCRs unrelated to AV22. Ni2+ is the most common cause of contact dermatitis, affecting 10-15% of the human population, and is also involved in reactions to metal implants such as knee and hip replacements. Here, too, specific TCR Vß motifs interact with a limited array of MHCs. In the skin, we have shown that Vß17 T cells such as the Ani2.3 T cell clone recognize Ni2+ bound to an HLA-DR52c (DR52c)-self peptide complex. Our data strongly suggest that the large Ni2+ cation is surface exposed in this complex, forming a major contact area for the TCR. Ni2+ appears to be bound to the same area of MHCII that is engaged by Be2+, i.e. in the space between the bound peptide and the MHCII ß chain. We will test this idea with structural studies on various Ni2+ specific TCRs bound to MHCII/peptide/Ni2+,and confirm the presence of Ni2+ reactive TCRs found in the blood of patients with failing metal implants due to nickel sensitization. We will pursue the following aims Aim 1 To elucidate the mechanism of presentation of HLA-DP2/ Be2+ to T cells, we will determine if Be2+ will influence engagement of the Vß5.1 TCR, AV22, indirectly via conformational changes in the DP2- self peptide surface, and determine how DP2/peptide/Be2+ is recognized by a TCR that is structurally not related to AV22, the Vß3.1 bearing TCR, RP11. Aim 2 To elucidate the mechanisms of presentation of MHCII/Ni2+ to T cells, we will define and characterize Ni2+ dependent peptides for the Vß17 TCR ANi2.3, determine whether Ni2+ is bound to DR1 in the same way as to DR52c, and whether the DR1/peptide/Ni2+/ SE9 (another Vß17 TCR) interaction is similar to that of DR52c/peptide/Ni2+/ANi2.3, and analyze the Ni2+ specific T cells in the blood of patients with joint implant failure due to nickel sensitization. Understanding the role of metal ions in these interactions will shed light on the mechanisms of metal induced immune diseases, and may help in the development of compounds that can modulate such interactions.