Data from: TAPBPR alters MHC class I peptide presentation by functioning as a peptide exchange catalyst

Our understanding of the antigen presentation pathway has recently been enhanced with the identification that the tapasin-related protein TAPBPR is a second MHC I-specific chaperone. We sought to determine whether, like tapasin, TAPBPR can also influence MHC I peptide selection by functioning as a peptide exchange catalyst. We show that TAPBPR can catalyse the dissociation of peptides from peptide-MHC I complexes, enhance the loading of peptide-receptive MHC I molecules, and discriminate between peptides based on affinity in vitro. In cells, the depletion of TAPBPR increased the diversity of peptides presented on MHC I molecules, suggesting that TAPBPR is involved in restricting peptide presentation. Our results suggest TAPBPR binds to MHC I in a peptide-receptive state and, like tapasin, works to enhance peptide optimisation. It is now clear there are two MHC class I specific peptide editors, tapasin and TAPBPR, intimately involved in controlling peptide presentation to the immune system.近期，随着研究确认与塔帕辛（tapasin）相关的蛋白TAPBPR是第二种主要组织相容性复合体I类（Major Histocompatibility Complex class I，MHC I）特异性分子伴侣，我们对抗原呈递通路的认知得到了进一步深化。本研究旨在探究TAPBPR是否可如塔帕辛一般，通过充当肽段交换催化剂来调控MHC I的肽段选择过程。实验结果显示，TAPBPR能够催化肽段从肽段-MHC I复合物上解离，提升肽段接纳型MHC I分子的肽段装载效率，并可在体外依据亲和力区分不同肽段。在细胞环境中，TAPBPR的蛋白耗竭会使MHC I分子呈递的肽段多样性显著增加，提示TAPBPR参与了对肽段呈递的限制过程。本研究结果提示，TAPBPR以肽段接纳状态结合MHC I分子，且与塔帕辛类似，可发挥增强肽段优化的作用。如今已有明确研究证据表明，存在两类MHC I特异性肽段编辑因子——塔帕辛与TAPBPR，二者深度参与调控向免疫系统的肽段呈递过程。