The role of beta cell ATF6 in type 1 diabetes

项目总结/摘要 1型糖尿病（T1 D）是由自身免疫介导的胰腺β细胞破坏引起的。尽管 自身免疫病因学，新的数据表明，内在的β细胞应激和缺陷的适应性应激反应， 可能在T1 D中功能性β细胞群的丧失中起重要作用。然而， 在T1 D中，应激反应调节β细胞死亡/存活的机制仍然是难以捉摸的，这主要是由于缺乏对β细胞死亡/存活的调控。 体内临床前遗传模型，阻碍了新型、有效和替代治疗策略的开发 针对T1 D。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ER应激时，未折叠蛋白反应（UPR），一种由ER介导的信号级联反应， 膜定位传感器ATF 6、IRE 1 α和PERK被触发以重建细胞内稳态。虽然这些 在急性应激下，UPR蛋白诱导适应性反应，在长期应激下，UPR启动细胞凋亡。的 在适应性和适应不良反应之间切换的决策机制，以及特定的适应性或 每种UPR传感器在不同细胞类型和疾病背景中的适应不良功能，还有待研究。 发现了 为此， 我们最近删除了一个临床前T1 D的β细胞中的Atf 6（Atf 6 β-/-）， 模型，非肥胖糖尿病（NOD）小鼠，在胰岛炎症开始之前。值得注意的是，Atf 6 β-/-小鼠 糖尿病发病率显著降低。NOD Atf 6 β-/-小鼠的分选β细胞的转录组分析 揭示了p53/p21信号通路作为最高富集通路，并揭示了以前未被识别的 T1 D进展期间β细胞中的促生存适应程序，其最终提供保护， T1D Atf 6 β-/-小鼠还显示胰岛炎减少，β- 细胞，表明Atf 6对免疫系统功能丧失的非细胞自主作用。因此在 根据这些数据，我们假设β细胞中Atf 6缺失后，由p21调控的新的适应性程序 信号传导占优势，其以非细胞自主方式改变β细胞-免疫细胞通信。此外，委员会认为， 我们假设，在急性与轻度和长期应激条件下，ATF 6触发不同的转录， 在人类β细胞中调节细胞稳态的程序。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，我们提出（i）鉴定 机制，b细胞中Atf 6的损失影响，b细胞-免疫细胞串扰（ii）定义p21的机制 在Atf 6 β-/-小鼠中上调和减少病理学，和（iii）确定ATF 6介导的应激适应 暴露于急性和长期ER应激的人类胰岛中的机制。成功完成这些 这些研究将填补我们关于Atf 6在β细胞中功能的知识库中的现有空白， β-细胞-免疫细胞串扰的机制，并显着提高我们对β-细胞-免疫细胞串扰机制的理解。 T1 D的细胞衰竭它还将为未来的研究提供机制见解，并支持替代翻译 针对B细胞UPR的T1 D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.