The role of beta cell ATF6 in type 1 diabetes

项目摘要/摘要 1型糖尿病(T1D)是由自身免疫介导的胰腺β细胞破坏所致。尽管它的 自身免疫病因学，新出现的数据表明固有的β细胞应激和缺陷的适应性应激反应 在T1D时功能性β细胞团的丢失中起重要作用。然而，分子机制是通过 应激反应调控β-T1D细胞死亡/存活的机制仍不清楚，这主要是由于缺乏In 体内临床前遗传模型，阻碍开发新的、有效的和替代的治疗策略 抗T1D。内质网(ER)应激是由蛋白质错误折叠、慢性炎症和 环境因素。在内质网应激时，未折叠蛋白反应(UPR)是由内质网介导的一系列信号级联反应 膜定位传感器ATF6、IRE1、α和PERK被触发以重新建立细胞内稳态。而这些 蛋白质在急性应激下诱导适应性反应，在长时间应激下UPR启动细胞凋亡。这个 用于在适应性和非适应性反应之间切换的决策机制，以及特定的适应性或 每个UPR传感器在不同的细胞类型和疾病背景下的不适应功能尚未得到证实 没有遮盖物。 为此， 我们最近在一个成熟的临床前T1D的β细胞(ATF6β-/-)中删除了ATF6 模型组，非肥胖型糖尿病(NOD)小鼠，在胰岛炎症开始前。值得注意的是，ATF6β-/-小鼠 表现出显著降低糖尿病发病率。NOD ATF6β-/-小鼠分选β细胞的转录组分析 揭示了p53/p21信号通路是最重要的富含途径，并发现了一个以前未被认识到的 在T1D进展期间β细胞中的亲生存适应性程序，最终提供保护 T1D。ATF6β-/-小鼠的胰岛素炎症减轻，免疫抑制标记物在β- 细胞，提示ATF6功能丧失对免疫系统的非细胞自主作用。因此，在 根据这些数据，我们假设在β细胞中ATF6缺失时，由p21控制的一种新的适应性程序 信号占上风，它以一种非细胞自主的方式改变了β-细胞-免疫细胞的通讯。此外， 我们假设，在急性、轻度和长期应激条件下，ATF6触发了不同的转录 调节人类β细胞内的细胞动态平衡的程序。在这里，通过利用小鼠模型和人类胰岛 结合技术和新试剂的综合工具箱，我们建议：(I)确定 B细胞中atf6的缺失影响b细胞免疫细胞串扰的机制(Ii)定义了p21的机制。 血管紧张素转换酶6β-/-小鼠的上调和病理改变，以及(Iii)确定血管紧张素转换酶6介导的应激适应 人胰岛暴露于急性和长期内质网应激的机制。这些项目的顺利完成 研究将填补我们关于ATF6在β细胞中的功能的知识库中的现有空白，确定一种新的 β-细胞-免疫细胞串扰的机制，并极大地提高了我们对β- T1D中的信元故障。它还将为未来的研究提供机械性的见解，并支持替代翻译 针对b-cell UPR的T1D策略。

PROJECT SUMMARY/ABSTRACT Type 1 diabetes (T1D) results from autoimmune-mediated destruction of pancreatic β-cells. Despite its autoimmune etiology, emerging data suggest that intrinsic β-cell stress and defective adaptive stress responses can play an important role in the loss of functional β-cell mass in T1D. However, the molecular mechanisms by which the stress responses regulate β-cell death/survival in T1D have remained elusive, due primarily to a lack of in vivo preclinical genetic models, hindering the development of novel, effective, and alternative therapeutic strategies against T1D. Endoplasmic reticulum (ER) stress is caused by protein misfolding, chronic inflammation, and environmental factors. Upon ER stress, the unfolded protein response (UPR), a signaling cascade mediated by ER membrane-localized sensors ATF6, IRE1α and PERK, is triggered to re-establish cellular homeostasis. While these proteins induce adaptive responses under acute stress, under prolonged stress the UPR initiates apoptosis. The decision mechanisms for switching between adaptive and maladaptive responses, and the specific adaptive or maladaptive functions of each UPR sensors in distinct cell types and disease contexts, are yet to be uncovered. To this end, we have recently deleted Atf6 in β-cells (Atf6β-/-) of a well-established preclinical T1D model, non-obese diabetes (NOD) mice, before the initiation of islet inflammation. Remarkably, Atf6β-/- mice exhibited significantly reduced diabetes incidence . Transcriptome analysis of sorted β-cells of NOD Atf6β-/- mice revealed p53/p21 signaling pathway as the top enriched pathway and uncovered a previously not recognized pro-survival adaptative program in β-cells during T1D progression, which ultimately confers protection from T1D. Atf6β-/- mice also showed reduced insulitis and increased expression of immune inhibitory markers in β- cells, suggesting a non-cell autonomous effect of loss of function of Atf6 on the immune system. Therefore, in light of these data we hypothesize that upon loss of Atf6 in β-cells, a novel adaptive program governed by p21 signaling prevails, which in a non-cell autonomous manner alters β-cells-immune cell communication. Moreover, we hypothesize that under acute versus mild and prolonged stress conditions ATF6 triggers distinct transcriptional programs to regulate cellular homeostasis in human β-cells. Here, by utilizing a mouse model and human islets combined with a comprehensive toolbox of techniques and novel reagents we propose to (i) identify the mechanisms, by which loss of Atf6 in b-cells impact, b-cell-immune cell crosstalk (ii) define the mechanisms of p21 upregulation and reduced pathology in Atf6β-/- mice, and (iii) determine the ATF6-mediated stress adaptation mechanisms in human islets exposed to acute and prolonged ER stress. The successful completion of these studies will fill an existing gap in our knowledge base regarding the function of Atf6 in β-cells, identify a novel mechanism for β-cell-immune cell crosstalk, and significantly improve our understanding of mechanisms of β- cell failure in T1D. It will also provide mechanistic insight for future studies and support alternative translational strategies for T1D that target the b-cell UPR.