Antigen processing in the secretory pathway

描述(由申请者提供)：我们研究的长期目标是了解和操纵免疫监视途径。抗原处理机制在细胞表面产生数以千计的多肽/MHC I类复合体(PMHC I)，作为CD8T细胞的潜在配体。与教科书模型通常描述的最终抗原肽是在细胞质本身产生的相反，最近的发现表明，抗原处理在内质网(ER)中继续进行。在内质网中修剪抗原前体的蛋白酶被称为ERAAP(或ERAP1)，即与抗原处理相关的内质网氨基肽酶。在ERAAP缺陷小鼠中，内质网中缺乏肽修剪会扰乱经典(MHC Ia)和令人惊讶的非经典(MHC Ib)提供的正常肽库：许多pMHC I缺失，伴随而来的是许多新的、高免疫原性的pMHC I出现在ERAAP缺陷细胞的表面。在野生型和ERAAP缺陷小鼠中，独特的多肽的丢失和获得导致了强烈的互惠免疫反应。在这里，我们建议检验一种假设，即在ERAAP缺陷细胞中出现的新肽在结构上是不同的，因为它们代表了正常修剪的多肽或那些被ERAAP破坏的多肽的未经编辑的版本。我们将通过质谱学和基于T细胞的分析来确定独特的免疫原肽的结构和来源。此外，由于ERAP1的多态与自身免疫性疾病(强直性脊柱炎和牛皮癣)有关，我们将检验这一假设，即多肽的组成不仅受MHC分子本身的多态影响，还受ERAAP的多态影响。我们期待这一提议的结果，以提供对抗原处理途径的更深层次的了解，以及如何操纵该途径来调节免疫原性。

DESCRIPTION (provided by applicant): The long term goal of our research is to understand and manipulate immune surveillance pathways. The antigen processing mechanisms yields thousands of peptide/MHC class I complexes (pMHC I) on the cell surface as potential ligands for CD8 T cells. Contrary to text book models which often depict the final antigenic peptide being generated in the cytoplasm itself, recent findings have shown that antigen processing continues in the endoplasmic reticulum (ER). The protease that trims antigenic precursors in the ER is called ERAAP (or ERAP1), for the ER aminopeptidase associated with antigen processing. In ERAAP-deficient mice, lack of peptide trimming in the ER disrupts the normal peptide repertoire presented by the classical (MHC Ia) and surprisingly, non-classical (MHC Ib) as well: many pMHC I go missing and concomitantly many novel, highly immunogenic pMHC I emerge on the surface of ERAAP-deficient cells. The loss and gain of unique peptides results in vigorous reciprocal immune responses in wild-type versus ERAAP-deficient mice. Here we propose to test the hypothesis that the novel peptides presented in ERAAP-deficient cells are structurally distinct because they represent unedited versions of normally trimmed peptides or those that were destroyed by ERAAP. We will determine the structure and origin of the unique immunogenic peptides by mass spectrometry and T-cell based assays. In addition, because polymorphisms in ERAP1 have been associated with autoimmune diseases (ankylosing spondylitis and psoriasis) we will test the hypothesis that the composition of the peptide repertoire is influenced not only by polymorphic MHC molecules themselves, but also by polymorphisms in ERAAP. We anticipate the results of this proposal to provide a deeper understanding of the antigen processing pathway and how the pathway can be manipulated to regulate immunogenicity.