Molecular Basis of T Cell Recognition of Metal Ions

 描述(申请人提供)：我们将在结构水平上研究人类T细胞对铍(Be2+)和镍(Ni2+)金属离子的超敏机制，并在人类受试者中证实这些机制。虽然有证据表明，这些金属离子是通过与自体多肽预先络合的MHC分子呈现给病理性T细胞的，但人们对金属离子如何与MHC结合，金属/MHC复合体如何被T细胞识别，以及这些过程在人类中是如何调节的知之甚少。慢性铍病(CBD)是一种衰弱的肺部疾病，主要由工作场所暴露于空气中的Be2+引起。该病与MHCII等位基因高度相关，尤其是人类白细胞抗原-DP2(DP2)等位基因，该等位基因在B链螺旋上有一个69位氨基酸的谷氨酸。我们的合作者发现，在人类的肺部，T细胞 对Be~(2+)的反应主要由含有不同T细胞受体(TCR)a链的V？5.1决定，它们都识别相同的DP2/肽/Be2+复合体。与AV22 TCR合作，我们发现非常小的Be2+阳离子深埋在一个灵活的P5-P7口袋中，并通过DP2-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适用于其他TCR-MHC相互作用，我们将测试这种灵活的Be2+呈现是否适用于AV22对Be2+/DP2与其他自体肽的识别，以及是否适用于与AV22无关的TCR。Ni2+是接触性皮炎最常见的原因，影响人类人口的10%-15%，也与膝关节和髋关节置换等金属植入物的反应有关。同样，在这里，特定的TCR V？基序与有限的MHC阵列相互作用。在皮肤上，我们已经证明了Vü17 T细胞，如Ani2.3 T细胞克隆，可以识别与人类白细胞抗原-DR52c(DR52c)-自体多肽复合体结合的Ni2+。我们的数据有力地表明，大量的Ni2+阳离子在这个络合物中暴露在表面，形成了TCR的主要接触区。Ni2+似乎结合到MHCII上与Be2+结合的同一区域，即在结合肽和MHCII？链之间的空间。我们将通过结合MHCII/肽/Ni2+的各种Ni2+特异性TCRs的结构研究来验证这一想法，并确认在因镍敏化而失败的金属种植体患者的血液中存在Ni2+反应性TCRs。我们将追求以下目标目标1为了阐明人类白细胞抗原-DP2/Be2+呈递给T细胞的机制，我们将确定Be2+是否会通过DP2-自身多肽表面的构象变化间接影响V？5.1 TCR，AV22的结合，并确定DP2/肽/Be2+如何被结构上与AV22无关的TCR识别，V？3.1承载TCR，RP11。目的2为了阐明MHCII/Ni2+呈递给T细胞的机制，我们将定义和鉴定17TCR ANi2.3的Ni2+依赖性多肽，确定Ni2+是否以与DR52c相同的方式与DR1结合，以及DR1/多肽/Ni2+/SE9(另一个V？17TCR)的相互作用是否类似于DR52c/多肽/Ni2+/ANi2.3的相互作用，并分析由于镍敏化而导致关节植入失败的患者血液中Ni2+特异性T细胞。了解金属离子在这些相互作用中的作用将有助于阐明金属诱导的免疫疾病的机制，并可能有助于开发能够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.