RACK1调控NF-κB信号通路在幽门螺杆菌感染致病中的作用及机制

RACK1 (Receptor for activated C kinase 1) interacts with many kinases and receptors (e.g., integrins) on the cell membrane, plays crucial roles in multiple cell signaling pathways and correlates to the development and progression of various diseases. In our previous studies, we found that the expression level of RACK1 in gastric mucosa of H.pylori infected chronic gastritis is significantly lower than that in H.pylori negative samples. During the H.pylori infection in stomach epithelial cell line, we also observed that knocking-down RACK1 by siRNAs promoted NF-κB activation, while siRNA knockdown of certain integrin members led to up- or down-regulation of NF-κB signal pathway. However, the detailed mechanisms are not yet clear. This project aims to systematically investigate the functions and mechanisms which RACK1 may play in the NF-κB signal pathway induced by H.pylori infection in cell lines, animal model and human gastric mucosa tissue samples, to elucidate the distinct roles RACK1 plays in different phases of H.pylori infection related gastric mucosal lesion, and to reveal how RACK1 regulates NF-κB activation by H.pylori infection through integrins. The implementation of this project will help us better understand the pathogenic mechanisms of H.pylori infection，and pave the way for the discovery of novel targets against H.pylori infection associated diseases.

RACK1与多种激酶及膜受体(如整合素)相互作用，在细胞应答过程中发挥重要作用，与多种疾病的发生密切相关。我们前期研究发现，RACK1在H.pylori感染阳性慢性胃炎中表达较未感染的慢性胃炎下降，阻断胃上皮细胞中RACK1表达可上调由H.pylori感染引起的NF-κB信号通路激活；而阻断不同的整合素成员表达将下调或促进H.pylori感染引起的NF-κB信号通路激活，但其具体的机制尚未明确。本研究拟通过细胞实验、动物模型及人胃粘膜组织标本系统地研究RACK1在H.pylori感染诱导的NF-κB信号通路激活中的作用及其机制，阐明RACK1在H.pylori感染相关胃黏膜病变发生发展不同阶段的作用；探讨RACK1如何通过与整合素作用以调控H.pylori感染诱导的NF-κB信号通路。本研究的实施将进一步阐明H.pylori感染致病机制，为H.pylori感染相关疾病的防治寻找有效靶点。

活化蛋白激酶C受体-1（RACK1）在胃癌中表达下调并参与调控NF-κB信号通路的活性。然后，RACK1的调控机制尚不明确。因此，本项研究旨在探讨幽门螺杆菌（Hp）感染、RACK1表达及NF-κB信号通路激活的关系及阐明其中的机制。我们利用TCGA数据库、生物芯片及胃黏膜标本检测RACK1在胃癌及癌旁的表达并进一步分析RACK1表达与胃癌患者预后之间的关系。构建Hp感染体外细胞模型及Hp感染蒙古沙鼠模型。通过免疫印迹及免疫组化方法检测RACK1及NF-κB信号通路关键分子的表达水平，实时荧光定量PCR方法检测NF-κB信号通路靶基因的表达，荧光素酶报告基因检测NF-κB信号通路的活性。结果显示RACK1在胃癌中的表达低于癌旁，且低表达RACK1的胃癌患者预后较差。Hp感染可在体内外下调RACK1的表达并激活NF-κB信号通路。过表达RACK1后可抑制NF-κB信号通路的激活及下游炎症因子的释放。此外，下调RACK1后整合素β-1的表达增加，而下调整合素β-1可抑制NF-κB信号通路的激活。Hp感染可在癌前病变阶段（肠上皮化生、异型增生）下调RACK1及上调整合素β-1的表达。我们的研究提出Hp感染、RACK1、整合素β-1及NF-κB信号通路激活之间存在机制上的联系，即Hp感染可下调RACK1的表达，从而上调整合素β-1的表达及随后的NF-κB信号通路的激活，导致炎症因子的释放，而这一过程在Hp致癌中扮演着重要的角色。此项研究将为Hp胃癌的治疗提供一个新靶点。