Decrypting MHC class I trafficking in cross-presentation

树突状细胞（DC）内化的抗原的交叉呈递对于引发针对病原体和肿瘤的CD 8 + T细胞应答以及免疫耐受至关重要。尽管有许多已发表的研究，但MHC-I分子交叉呈递的运输途径和装载区室仍不清楚。初步证据表明，交叉呈递可能采用不同的MHC-I来源和运输途径，包括通过常规和非常规分泌和/或高尔基体至内体途径的新合成的MHC-I分子，以及不同亚型内体中的MHC-I储存和再循环MHC-I分子，这取决于抗原进入途径和研究的细胞类型。该项目将汇集两个在研究MHC-I分子贩运方面具有丰富专业知识的团队。这些团队将利用他们互补的专业知识以及一系列交叉呈递分析来破译MHC-I分子的起源、装载区室和前往细胞表面的过程，MHC-I分子装载有来自两种抗原（卵清蛋白和胰岛素）的交叉呈递肽，这些肽通过不同的机制（吞噬作用、甘露糖受体内吞作用、Fc受体内吞作用、胞饮作用）内化。使用RUSH（使用选择性钩的保留）和SpyTag/SpyCatcher系统的新型检测方法的开发将使团队能够研究同步的细胞内运输以及共价标记的细胞表面MHC-I分子的内化。如果可能，将在体内抗肿瘤疫苗接种的背景下使用条件性缺失模型评估关键运输途径的影响。最终，所获得的结果可能有助于交叉呈递的药理学操作，其目的是上调抗肿瘤免疫应答或靶向抗原进入特异性加工途径，但也下调自身抗原的交叉呈递，并因此下调自身免疫性炎症。

Cross-presentation of antigens internalized by dendritic cells (DCs) is critical for priming of CD8+ T cell responses to pathogens and tumors, and for immune tolerance. Despite many published studies, the trafficking pathways and loading compartments for cross-presentation by MHC-I molecules remain unclear. Preliminary evidence suggests that cross-presentation may employ diverse MHC-I sources and trafficking pathways, including newly synthesized MHC-I molecules routed through conventional and non-conventional secretory and/or Golgi-to-endosome pathways, but also MHC-I stores in different subtypes of endosomes, and recycling MHC-I molecules, depending on the antigen entry route and the cell type investigated. This project will bring together two teams with documented strong expertise in studying trafficking of MHC-I molecules. The teams will employ their complementary expertise together with an array of cross-presentation assays to decipher the origin, loading compartments, and travel to the cell surface of MHC-I molecules loaded with cross-presented peptides derived from two antigens (ovalbumin and insulin) internalized by distinct mechanisms (phagocytoseis, mannose receptor endocytosis, Fc receptor endocytosis, pinocytosis). The development of novel assays using the RUSH (retention using selective hooks) and SpyTag/SpyCatcher systems will enable the teams to study synchronized intracellular trafficking as well as internalization of covalently labeled cell surface MHC-I molecules. If possible, the impact of key trafficking pathways will be assessed using conditional deletion models in the context of antitumor vaccination in vivo. Ultimately, the results obtained might be instrumental for pharmacological manipulation of cross-presentation with the objective to up-regulate antitumor immune responses or target antigens into specific processing pathways but also to down-regulate cross-presentation of self- antigens and consequently autoimmune inflammation.