Toll-like Receptor Control of MHC Class I Endocytosis

提案摘要 交叉呈递是主要组织相容性复合体I类（MHC-I）分子被免疫组织化学标记的过程。 装载有来源于包括内化的可溶性蛋白质的蛋白质的细胞外来源的肽， 微生物和垂死的细胞。交叉呈递是树突状细胞（DCs）的一种特性， 但即使在DC中，这种特异性也可以是天然的，或者必须在激活后获得。 被称为cDC 1的常规DC是有效的交叉呈递者，并且可以组成性地这样做，而炎性DC可以是非结构性的。 在炎症组织中发现的单核细胞来源的DC和另一个常规DC亚群cDC 2也可以交叉- 在感染和炎症的情况下存在。与DCs中已确立的异质性平行， 组织在稳态和炎症时，DC亚群在稳态或炎症过程中具有不同的功能状态。 炎症这种功能差异主要是由先天信号受体的参与协调的， 例如Toll样受体（TLR），其介导多种细胞程序，包括 炎性基因和介质，以及亚细胞囊泡交通的快速重组， 翻译后事件，如磷酸化。我们必须全面调查DC 当先天受体参与时，DC在炎症下起作用，并且不限于DC分类， 具有刚性不灵活功能的子集。确定炎性先天受体和信号的性质， 使DC能够增强其交叉呈递能力或重新获得这种能力，将为疫苗设计提供信息， 感染性疾病和癌症，其中细胞毒性CD 8 T细胞对于生物体存活是绝对必要的。一 对交叉呈现规律的机制性剖析对于小说的鉴别具有重要意义 治疗靶点，可用于利用CD 8 T细胞免疫，并提供长期保护， 未来的感染或癌症复发。抗原的内化、加工和呈递在很大程度上依赖于 亚细胞小泡运输为研究鼠常规DC而开发的体外工具已用作 是交叉呈递机制及其调节的开创性发现的主力， 已经转化为人类DC亚群，并影响了疫苗设计和细胞疗法。这些工具已 使我们发现了对交叉呈递至关重要的MHC-I的内体再循环隔室储存， 在被免疫逃避病毒感染后耗尽，这一发现已在人DC中复制。我们有 现在发现了内吞抗原的交叉呈递和一种特殊的先天受体之间的新联系 据报道由培养的DC、炎性DC和cDC 2亚群表达。我们假设这个受体 使MHC-I运输与内吞抗原相交以在感染期间许可交叉呈递。使用培养的和 从小鼠淋巴器官分离的离体DC，我们将定义不同的先天免疫信号传导 调节MHC-I内吞作用的组分。我们将确定MHC-I的特征，使其能够调节 内吞作用我们的研究将为急需的T细胞疫苗提供信息，以对抗传染病和癌症。

PROPOSAL SUMMARY Cross-presentation is the process whereby major histocompatibility complex class I (MHC-I) molecules are loaded with peptides derived from an extracellular source of proteins including internalized soluble proteins, microorganisms and dying cells. Cross-presentation is a specialty of dendritic cells (DCs), cell types responsible for priming naïve T cells, but even in DCs, this specialty can come naturally or must be acquired upon activation. Conventional DCs known as cDC1 are potent cross-presenters and can do so constitutively, while inflammatory monocyte-derived DCs found in inflamed tissues and another subset of conventional DCs, cDC2, can also cross- present under conditions of infection and inflammation. Parallel to the well-established heterogeneity of DCs in tissues at steady state and inflammation, DC subsets have different functional states during homeostasis or inflammation. This functional difference is primarily orchestrated by the engagement of innate signaling receptors, such as Toll-like receptors (TLRs), that mediate diverse cellular programs including the transcription of inflammatory genes and mediators, as well as the rapid reorganization of subcellular vesicular traffic through post-translational events such as phosphorylation. It is imperative that we investigate the full spectrum of DC functions under inflammation when innate receptors are engaged, and to not be limited to DC classifications as subsets with rigid inflexible functions. Defining the nature of the inflammatory innate receptors and signals that enable DCs to augment their cross-presentation capacity or to acquire it anew, will inform vaccine design for infectious diseases and cancer where cytotoxic CD8 T cells are absolutely essential for organismal survival. A mechanistic dissection of the regulation of cross-presentation is important for the identification of novel therapeutic targets that can be exploited to harness CD8 T cell immunity and confer long term protection against future infection or cancer resurgence. Antigen internalization, processing, and presentation rely heavily on subcellular vesicular traffic. In vitro tools developed for studying murine conventional DCs have served as the workhorse responsible for seminal discoveries of the mechanisms of cross-presentation and its regulation, which have translated to human DC subsets and have impacted vaccine design and cellular therapies. Such tools have enabled our discovery of endosomal recycling compartment stores of MHC-I critical for cross-presentation and depleted upon infection by immunoevasive viruses, findings that have been replicated in human DCs. We have now discovered a new link between cross-presentation of endocytosed antigen and a particular innate receptor reported to be expressed by cultured DCs, inflammatory DCs and a cDC2 subset. We hypothesize this receptor intersects MHC-I traffic with endocytic antigen to license cross-presentation during infection. Using cultured and ex-vivo DCs isolated from the lymphoid organs of mice, we will define the distinct innate immune signaling components that regulate MHC-I endocytosis. We will determine the features of MHC-I that enable its regulated endocytosis. Our studies will inform urgently needed T cell vaccines against infectious diseases and cancer.