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抗原提呈通路仅展示来自细胞的 自己的蛋白质。相比之下，树突状细胞(DC)和巨噬细胞(M？S)能够获得并随后 通过一种称为交叉呈现(XPT)的过程展示来自外部抗原的多肽。XPT是关键 这种机制允许免疫系统识别并动员CD8 T细胞对癌症的反应， 许多病毒感染和细胞内病原体。因此，这条途径对免疫很重要。 这是一个有吸引力的目标，使疫苗能够诱导CD8 T细胞免疫，这是一种 目前的亚单位疫苗未能做到这一点。这笔赠款的总体目标是阐明允许区议会 以执行这一关键职能。在主要的XPT途径中，外源蛋白首先内化到 吞噬小体，然后转移到胞浆，在那里它们被蛋白酶体切割成寡肽。 最近的数据表明，用于XPT的蛋白酶体产生的多肽随后被输入回 与MHC I分子结合的吞噬小体(这里称为“吞噬小体XPT”)。然而，为什么会这样呢 多肽不会像大多数胞质产生的多肽那样简单地传递到内质网中的MHC I分子， 是一个谜，也是我们的首要目标是要解开的。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在物理上与吞噬小体的胞液表面相联系，并通过 它们的PA28封端复合体与多肽负载复合体(TAP+Tapasin)的胞液结构域结合。 这种排列因此将局部多肽的产生(通过吞噬小体结合的蛋白酶体)与局部多肽联系起来。 运输(通过吞噬体吸水)。这些假设的重要性在于，它们有可能填补关键 吞噬体XPT途径中缺失的环节，并确定PA28复合体的重要功能，它 到目前为止一直被认为是相对不重要的。我们的第二个目标是试图阐明允许 MHC I类分子在吞噬小体的“不友好”环境中结合多肽，并解决这个问题 为什么当外源抗原是与细胞相关的时，抗原的XPT会令人惊讶地更有效，因为 与任何其他形式的相同抗原相比。这一目标将检验以下假设：？2微球蛋白(？2m) 从摄入的外源细胞中促进吞噬体内多肽-MHC I复合体的形成。在这 机制，游离？2M(来自摄取的细胞)+游离MHC I重链传递到和/或产生于 吞噬小体(来自在液泡中变性的复合体)+多肽(来自PA28-蛋白酶体-产物 通过TAP导入到吞噬体内)结合形成吞噬体内的MHC I-肽复合体。这个 这一假设的重要性在于，它将为一个生物学上重要的过程提供洞察力。此外，这一点 这种机制可能能够被操纵，以增强疫苗/免疫疗法的XPT。