Mechanisms of cross-presenting antigens in phagosomes on MHC I molecules to stimulate CD8 T lymphocyte responses

MHC I分子上的吞噬体中交叉呈递抗原刺激CD8 T淋巴细胞反应的机制

基本信息

批准号：
9797712
负责人：
KENNETH L ROCK
金额：
$ 41.88万
依托单位：
UNIV OF MASSACHUSETTS MED SCH WORCESTER
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-05-24 至 2024-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9797712
关键词：
AGFG1 gene Abbreviations Address Antigen Presentation Antigen Presentation Pathway Antigen-Presenting Cells Antigens Back Binding Biological CD8-Positive T-Lymphocytes Cells Cleaved cell Complex Cross Presentation Cytosol Data Dendritic Cells Development Disease Doxycycline Environment Face Generations Genetic Goals Grant Health Hybrids I-antigen Immune response Immune system Immunity Immunologic Monitoring Immunologic Surveillance Immunotherapy Ingestion Knock-out Lead Link Major Histocompatibility Complex Malignant Neoplasms Modeling Monitor Nucleoproteins Oligopeptides Ovalbumin PA700 proteasome activator Pathologic Processes Pathway interactions Patients Peptide Transport Peptides Phagosomes Physiological Polyubiquitin Process Proteasome Binding Proteins Proteomics Role Subunit Vaccines T cell response Tertiary Protein Structure Testing Tissues Ubiquitin Vaccines Vacuole Viral Virus Virus Diseases base beta-2 Microglobulin in vivo insight macrophage multicatalytic endopeptidase complex pathogen peptide I prevent response vaccine development vaccine immunotherapy

项目摘要

Abstract In most cells the MHC I antigen presentation pathway exclusively displays peptides that are derived from a cell's own proteins. In contrast, dendritic cells (DCs) and macrophages (MØs) are capable of acquiring and then displaying peptides from external antigens through a process called cross presentation (XPT). XPT is the key mechanism that allows the immune system to recognize and then mobilize a CD8 T cell response to cancers, many viral infections and intracellular pathogens. Consequently, this pathway is important for immune surveillance and is an attractive target to enable vaccines to elicit CD8 T cell immunity, which is something current subunit vaccines fail to do. The overall goal of this grant is to elucidate key mechanisms that allow DCs to carry out this critical function. In the major XPT pathway, exogenous proteins are first internalized into phagosomes and then transferred into the cytosol, where they are cleaved into oligopeptides by proteasomes. Recent data suggests that the proteasome-generated peptides for XPT are subsequently imported back into phagosomes for binding to MHC I molecules (referred to here as “phagosomal XPT”). However, why such peptides would not simply be delivered to MHC I molecules in the ER, as most cytosolic generated peptides are, is a mystery and one that our first aim seeks to solve. Our underlying hypothesis, supported by preliminary data, is that a subset of proteasomes physically associates with the cytosolic face of phagosomes and does so by via their PA28 capping complex binding to the cytosolic domains of the peptide-loading complex (TAP+Tapasin). This arrangement thereby links local peptide generation (by the phagosome-bound proteasomes) to local peptide transport (by phagosomal TAP). The importance of these hypotheses is that they have the potential to fill in key missing links in the phagosomal XPT pathway and to identify an important function for PA28 complexes, which up until now have thought to be relatively unimportant. Our second aim seeks to elucidate mechanisms that allow MHC I molecules to bind peptides in the “unfriendly” environment of the phagosome and to address the question of why XPT of antigens is surprisingly much more efficient when the exogenous antigen is cell-associated, as compared to the same antigen in any other form. This aim will test the hypothesis that ß2 microblobulin (ß2M) from ingested exogenous cells promotes the formation of peptide-MHC I complexes in phagosomes. In this mechanism, free ß2M (from ingested cells) + free MHC I heavy chains delivered to and/or generated in phagosomes (from complexes denatured in the vacuole) + peptides (from PA28-proteasome-products that are imported into phagosomes by TAP) associate to form intraphagosomal MHC I-peptide complexes. The importance of this hypothesis is that it would provide insight into a biologically important process. Moreover, this mechanism may be able to be manipulated to enhance XPT for vaccines/immunotherapies.

抽象的在大多数细胞中，MHC I 抗原呈递途径显示的肽完全源自细胞的相反，树突状细胞 (DC) 和巨噬细胞 (MØs) 能够获取并随后获得自身的蛋白质。通过称为交叉呈递 (XPT) 的过程展示来自外部抗原的肽。允许免疫系统识别并调动 CD8 T 细胞对癌症做出反应的机制，经过许多病毒感染和细胞内病原体测试，该途径对于免疫很重要。监视，并且是使疫苗能够引发 CD8 T 细胞免疫的一个有吸引力的目标，这是目前的亚单位疫苗无法做到这一点这笔拨款的总体目标是阐明允许 DC 的关键机制。为了执行这一关键功能，在主要的 XPT 途径中，外源蛋白首先被内化。吞噬体，然后转移到胞质溶胶中，在那里它们被蛋白酶体裂解成寡肽。最近的数据表明，用于 XPT 的蛋白酶体生成的肽随后被导入回吞噬体与 MHC I 分子结合（此处称为“吞噬体 XPT”）。肽不会像大多数胞质生成的肽那样简单地传递到 ER 中的 MHC I 分子，这是一个谜团，也是我们的首要目标寻求解决的一个谜团，我们的基本假设得到了初步数据的支持，蛋白酶体的一个子集与吞噬体的胞质面发生物理联系，并通过以下途径实现这一点：它们的 PA28 封端复合物与肽负载复合物 (TAP+Tapasin) 的胞质结构域结合。这种排列从而将局部肽生成（通过吞噬体结合的蛋白酶体）与局部肽联系起来这些假设的重要性在于它们有可能填补关键问题。吞噬体 XPT 通路中缺失的环节并确定 PA28 复合物的重要功能，到目前为止，我们的第二个目标是阐明允许的机制。 MHC I 分子在吞噬体的“不友好”环境中结合肽并解决这个问题当外源抗原与细胞相关时，为什么抗原的 XPT 令人惊讶地更有效，如与任何其他形式的相同抗原进行比较该目的将检验 ß2 微球蛋白 (ß2M) 的假设。来自摄入的外源细胞的肽促进吞噬体中肽-MHC I 复合物的形成。机制，游离 ß2M（来自摄入的细胞）+ 游离 MHC I 重链传递至和/或产生于吞噬体（来自真空变性的复合物）+肽（来自 PA28 蛋白酶体产物，通过 TAP 导入吞噬体）结合形成吞噬体内 MHC I-肽复合物。该假设的重要性在于，它将提供对生物学上重要过程的深入了解。可以操纵该机制来增强疫苗/免疫疗法的 XPT。