Changes in actin dynamics regulated by villin and gesolin are determinants of cell fate and may be key to gastrointestinal inflammatory disease

调节信使核糖核酸的翻译是细胞对任何形式的压力最直接的反应之一。它被启动了 通过压力感应蛋白，所有这些蛋白都能使真核细胞翻译起始因子的α亚基磷酸化。 2(EIF2A)。这导致全球蛋白质合成受到抑制，但伴随着选择性地翻译 对细胞存活和从压力中恢复至关重要的蛋白质。恢复细胞内稳态和逆转EIF2A 信号转导，EIF2A的去磷酸化受蛋白磷酸酶1(PP1)调控，PP1与其一个 调节亚基和球状肌动蛋白(G-肌动蛋白)。因此，G-肌动蛋白限制了PP1的活性，尽管细胞肌动蛋白 动力学是否被修饰来调节PP1的活性尚不清楚。EIF2A信号增加激活的翻译 转录因子4(ATF4)促进自噬等应激修复相关基因的表达 基因。相反，如果压力没有解决，ATF4调节促进细胞死亡的基因的转录 以消除受损细胞。调节细胞应激反应的控制开关，在存活和 死亡是大多数炎症性疾病的始作俑者。与此相一致的是，EIF2A信号的慢性激活 与克罗恩病(CD)患者的粘膜炎症有关。尽管如此，分子基础 肠上皮细胞(IECS)中的EIF2A信号转导机制尚不清楚。我们做了一个新奇的观察 IEC肌动蛋白细胞骨架具有作为细胞健康生物传感器的一般功能，并调节EIF2A信号转导。 以确定受压力的细胞是会存活还是会死亡。我们发现，通过调节细胞肌动蛋白动力学，有两个 同源肌动蛋白切断蛋白绒毛蛋白1和明胶蛋白将压力信号通路与细胞命运结合在一起 小路。利用绒毛蛋白1/明胶蛋白双基因敲除小鼠，我们发现当IEC之间的串扰 肌动蛋白细胞骨架和EIF2A信号不能正常工作，慢性炎症随之而来。结果, DKO小鼠发生自发性回肠炎，在功能、组织学和临床上与人类CD相似。 此外，我们对CD和CD患者样本的小鼠模型的研究表明，串扰中的缺陷 在IEC肌动蛋白细胞骨架和EIF2A之间的信号转导可能是CD的普遍特征。我们建议 研究这些通路在IECS中如何正常运行以及它们是如何出错的，可以提供对 推动CD发病机制的事件，但也可以确定CD的新治疗策略。我们向您介绍一个 创新的机械方法，使用最先进的技术，结合使用IEC线，转基因 以及经过验证的小鼠疾病模型和患者样本。这项研究的目标是：(1)表征 肌动蛋白细胞骨架和胁迫信号之间的串扰决定的分子机制(S) IEC命运；(2)确定肌动蛋白细胞骨架和应激信号之间的串扰中的缺陷是如何起作用的 CD发病机制的研究；(3)CD及CD患者模型小鼠肠道组织的体内外检测 样本，靶向这些缺陷的治疗益处。我们的研究将推动科学发现和 可能导致将基础科学转化为新的治疗方法，以促进CD患者的护理。

Regulation of mRNA translation is one of the most immediate cell response to any form of stress. It is initiated by stress sensing kinases, all of which phosphorylate the alpha subunit of eukaryotic translation initiation factor 2 (EIF2A). This results in repression of global protein synthesis but is accompanied by selective translation of proteins vital for cell survival and recovery from stress. To restore cellular homeostasis and to reverse EIF2A signaling, de-phosphorylation of EIF2A is regulated by protein phosphatase 1 (PP1) in complex with one of its regulatory subunits and globular actin (G-actin). G-actin therefore, limits PP1 activity although how cellular actin dynamics are modified to regulate PP1 activity is not known. EIF2A signaling increases translation of activating transcription factor 4 (ATF4) to promote expression of genes involved in stress remediation such as autophagy genes. Conversely, if the stress is unresolved ATF4 regulates the transcription of genes that promote cell death to eliminate damaged cells. The control switch that modulates the cells stress response between survival and death governs the initiation of most inflammatory diseases. In line with that, chronic activation of EIF2A signaling is associated with mucosal inflammation in patients with Crohn’s disease (CD). Despite this, the molecular basis of EIF2A signaling in intestinal epithelial cells (IECs) remains unidentified. We made the novel observation that the IEC actin cytoskeleton fulfils a general function as a biosensor of cell health and regulates EIF2A signaling to establish if the stressed cell will survive or die. We show that by regulating cellular actin dynamics, two homologous actin-severing proteins villin1 and gelsolin integrate stress signaling pathways with cell fate pathways. Using the villin1/gelsolin double knockout mice we show that when the crosstalk between the IEC actin cytoskeleton and EIF2A signaling does not function properly, chronic inflammation ensues. As a result, DKO mice develop spontaneous ileitis that resembles functionally, histologically and clinically human CD. Moreover, our studies with mouse models of CD and CD patient samples indicate that defects in the crosstalk between IEC actin cytoskeleton and EIF2A signaling could be a universal feature of CD. We propose that studying how these pathways normally function in the IECs and how they go awry can provide basic insight into events that drive CD pathogenesis but can also identify novel treatment strategies for CD. We present an innovative mechanistic approach using state-of-the-art techniques that combine the use of IEC lines, transgenic and validated mouse models of disease, and patient samples. The goal of the study is: (1) to characterize the molecular mechanism(s) by which the crosstalk between the actin cytoskeleton and stress signaling determines IEC fate; (2) to determine how defects in the crosstalk between actin cytoskeleton and stress signaling contribute to CD pathogenesis; (3) and to test in vivo and ex vivo in enteroids from mouse models of CD and CD patient samples, the therapeutic benefits of targeting these defects. Our study will advance scientific discovery and could lead to translation of the basic science to model novel therapies to advance CD patient care.