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

• 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
• 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

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.

摘要 在大多数细胞中，MHC I抗原呈递途径专门展示源自细胞的多肽。 自己的蛋白质。相比之下，树突状细胞（DC）和巨噬细胞（MCs）能够获得，然后 通过称为交叉呈递（XPT）的过程展示来自外部抗原的肽。XPT是关键 允许免疫系统识别并动员CD 8 T细胞对癌症的反应的机制， 许多病毒感染和细胞内病原体。因此，该途径对于免疫调节是重要的。 它是一个有吸引力的靶点，使疫苗能够引发CD 8 T细胞免疫，这是一个重要的因素。 目前的亚单位疫苗不能做到这一点。这项赠款的总体目标是阐明关键机制，使发展中国家 来执行这一关键功能。在主要的XPT途径中，外源蛋白首先被内化到 吞噬体，然后转移到细胞质中，在那里它们被蛋白酶体切割成寡肽。 最近的数据表明，蛋白酶体产生的XPT肽随后被输入回 吞噬体XPT用于结合MHC I分子（在此称为“吞噬体XPT”）。但是，为什么这样 肽不会像大多数胞质产生的肽那样简单地递送到ER中的MHCI分子， 这是一个谜，也是我们的首要目标。我们的基本假设得到了初步数据的支持， 是蛋白酶体的一个子集与吞噬体的胞质表面物理结合， 它们的PA 28加帽复合物与肽负载复合物（TAP+Tapasin）的胞质结构域结合。 因此，这种排列将局部肽的产生（通过吞噬体结合的蛋白酶体）与局部肽的产生（通过吞噬体结合的蛋白酶体）联系起来。 运输（通过吞噬体TAP）。这些假设的重要性在于它们有潜力填补关键 吞噬体XPT途径中缺失的环节，并确定PA 28复合物的重要功能， 到目前为止，他们认为这是相对不重要的。我们的第二个目标是阐明机制， MHC I分子在吞噬体的“不友好”环境中结合肽， 为什么当外源性抗原是细胞相关的时，抗原的XPT令人惊讶地更有效， 与任何其他形式的相同抗原相比。这一目的将检验β 2微球蛋白（β 2 M） 从摄入的外源细胞中的肽促进吞噬体中肽-MHC I复合物的形成。在这 机制，游离β 2 M（来自摄入的细胞）+游离MHC I重链递送至和/或产生于 吞噬体（来自在液泡中变性的复合物）+肽（来自 通过TAP输入到吞噬体中）结合形成吞噬体内MHC I-肽复合物。的 这一假说的重要性在于它将提供对生物学重要过程的深入了解。而且这 可以操纵这种机制以增强用于疫苗/免疫疗法的XPT。