Role of the ER acetyl CoA transporter in alcoholic pancreatitis

摘要 慢性胰腺炎(CP)是一种疼痛的、衰弱的胰腺外分泌疾病，缺乏治疗和治疗 预防疾病进展的策略。酗酒和吸烟是CP的常见原因，但 它们对胰腺的毒性作用的潜在机制尚不清楚。最近，自适应机制 在胰腺腺泡细胞中发现了酒精等应激源预防胰腺炎。这些自适应 机制涉及内质网(ER)、未折叠蛋白反应(UPR)和UPR 转录因子X-box结合蛋白1(XBP1s)上调ER伴侣、ER转运蛋白和 维持ER功能的质量控制机器。我们之前的工作表明，酒精摄入 诱导氧化应激，但也上调XBP1和保护性UPR，以防止病理，而 吸烟抑制酒精诱导的XBP1s的形成，并上调由以下途径介导的病理UPR信号 C/EBP同源蛋白(CHOP)导致内质网功能障碍和胰腺炎。这个项目调查了 与酗酒、吸烟和ER蛋白紊乱相关的胰腺炎的分子决定因素 折叠和贩卖。可逆N-ε-赖氨酸乙酰化调节ER蛋白向高尔基体转运的效率 以及分泌途径。适当折叠的蛋白质的乙酰化使内质网到高尔基体退出，而非 乙酰化的、错误折叠的蛋白质转移到蛋白质降解系统。因此，ER蛋白乙酰化的中断 扰乱内质网功能和蛋白质运输。乙酰辅酶A转运体AT-1介导乙酰辅酶A进入内质网 从细胞质中提取辅酶A，为乙酰化提供底物。在人类中，AT-1-S113R突变体降低AT-1 运输能力，这种突变的个体表现出神经退行性疾病。我们发现XBP1 调节腺泡细胞中的AT-1水平。此外，AT-1S113r/+或腺泡特异性AT-1缺陷小鼠发生轻度/ 中度慢性应激和慢性内质网应激并伴有XBP1s升高。令人惊讶的是，这些小鼠的AP诱发率降低 XBP1s水平升高，并显著加剧CP进展。我们的结果表明AT-1和XBP1是 在对酒精的反应中相互依赖和重要的胰腺适应，但当被 环境应激源这些适应性系统失灵会导致病理。我们最重要的假设是 慢性腺泡细胞应激和通过饮酒/吸烟减少的XBP1s保护计划减弱 AT-1表达，扰乱ER乙酰化和ER功能，诱发重度CP。vbl.使用 酒精+吸烟CP的实验模型，我们将追求3个目标。目标一号将测试酒精是否 在腺泡特异性AT-1 KO小鼠中，吸烟/吸烟可将轻度/中度CP转化为严重疾病。目标2 将评估增强的XBP1表达或CHOP基因缺失是否部分缓解了CP的严重程度 AT-1KO小鼠。目的3研究ER乙酰化途径对ER蛋白折叠和转运的调节作用 以及内质网蛋白的降解。我们希望这个项目能为推动CP的途径提供见解 发展，并为阻止CP进展的策略确定分子靶点。

ABSTRACT Chronic pancreatitis (CP), a painful, debilitating disorder of the exocrine pancreas, lacks treatments and strategies to prevent disease progression. Alcohol abuse and smoking are common causes of CP but the mechanisms underlying their toxic effects on the pancreas are unclear. Recently, adaptive mechanisms that prevent pancreatitis with stressors such as alcohol were identified in the pancreatic acinar cell. These adaptive mechanisms involve the endoplasmic reticulum (ER) Unfolded Protein Response (UPR) and the UPR transcription factor, X-box binding protein 1 (XBP1s) that upregulates ER chaperones, ER transporters, and quality control machinery to maintain ER function. Our previous work showed that alcohol administration induces oxidative stress but also upregulates XBP1s and a protective UPR that prevents pathology, while smoking inhibits alcohol induced XBP1s formation, and upregulates a pathologic UPR signal mediated by C/EBP homologous protein (CHOP) resulting in ER dysfunction and pancreatitis. This project investigates molecular determinants of pancreatitis associated with alcohol abuse, smoking and perturbed ER protein folding and trafficking. Reversible Nε-lysine acetylation regulates the efficiency of ER protein transit to Golgi and the secretory pathway. Acetylation of properly folded proteins enables ER-to-Golgi exit, while non- acetylated, misfolded proteins divert to protein degradation systems. Thus, disruption of ER protein acetylation perturbs ER function and protein trafficking. The acetyl CoA transporter, AT-1 mediates ER entry of acetyl CoA from cytoplasm to provide substrate for acetylation. In humans, the AT-1-S113R mutant reduces AT-1 transport capacity, and individuals with this mutant exhibit neurodegenerative disorders. We found that XBP1s regulates AT-1 levels in acinar cells. Moreover, AT-1S113r/+ or acinar-specific AT-1 deficient mice develop mild/ moderate CP and chronic ER stress with elevated XBP1s. Strikingly, AP induction in these mice decreases XBP1s levels and markedly exacerbates CP progression. Our results indicate AT-1 and XBP1s are interdependent and important for pancreas adaption in response to alcohol but when overwhelmed by environmental stressors these adaptive systems fail leading to pathology. Our overarching hypothesis is that chronic acinar cell stress and reduced XBP1s protective programs by drinking/smoking attenuate AT-1 expression, disrupting ER acetylation and ER function, and inducing severe CP. Using experimental models of alcoholic + smoking CP, we will pursue 3 aims. Aim 1 will test whether alcohol consumption/smoking converts mild/moderate CP into severe disease in acinar-specific AT-1 KO mice. Aim 2 will evaluate whether enhanced XBP1s expression or CHOP genetic deletion partially mitigates CP severity in AT-1 KO mice. Aim 3 will investigate ER acetylation pathway regulation of ER protein folding and trafficking as well as ER protein degradation. We expect this project to provide insights into the pathways driving CP development, and pinpoint molecular targets for strategies to halt CP progression.