circEIF3I促进SMAD3的招募到早期内体，从而促进了TGF-β信号通路介导的胰腺癌细胞中MMPs的活化。
circEIF3I facilitates the recruitment of SMAD3 to early endosomes to promote TGF-β signalling pathway-mediated activation of MMPs in pancreatic cancer.
发表日期：2023 Sep 09
作者：
Zhongjie Zhao, Wenbo Yang, Rui Kong, Yangyang Zhang, Le Li, Zengfu Song, Hongze Chen, Yan Luo, Tao Zhang, Chundong Cheng, Guanqun Li, Danxi Liu, Xinglong Geng, Hua Chen, Yongwei Wang, Shangha Pan, Jisheng Hu, Bei Sun
来源：
Molecular Cancer
摘要：
在消化道肿瘤中，胰管腺癌（PDAC）表现出最高的死亡率趋势。此外，尽管PDAC的转移仍然是癌症相关死亡的主要原因，但其生物学机制尚不清楚。最近的证据表明，环形RNA（circRNA）在PDAC进展中起重要作用。通过生物信息学分析筛选了正常和PDAC组织中表达差异的circRNA。进行Sanger测序、RNase R和actinomycin D实验以确认circEIF3I的环状结构。进行体外和体内功能实验评估circEIF3I在PDAC中的作用。通过MS2标记的RNA亲和纯化、质谱分析、RNA免疫沉淀、RNA下拉实验、荧光原位杂交、免疫荧光和RNA-蛋白交互作用模拟和分析等方法，鉴定circEIF3I的相互作用蛋白。通过共免疫沉淀和Western blotting测定circEIF3I对SMAD3与TGFβRI或AP2A1之间相互作用的影响。微阵列数据分析显示circEIF3I在PDAC细胞中高表达，并与TNM分期和不良预后相关。体内外功能实验证实circEIF3I通过增加MMPs表达和活性促进PDAC细胞的迁移、侵袭和转移。机制研究表明，circEIF3I结合到SMAD3的MH2结构域，并通过增强SMAD3与早期内体中的TGFβRI之间的相互作用增加SMAD3的磷酸化。此外，AP2A1直接与circEIF3I结合，并促进circEIF3I结合的SMAD3招募到早期内体中的TGFβRI。最后，我们发现circEif3i在小鼠中的生物学功能与在PDAC人体中的circEIF3I相似。我们的研究揭示了circEIF3I促进胰腺癌的进展。circEIF3I是一个与SMAD3和AP2A1相互作用形成三元复合物的分子支架，促进SMAD3招募到早期内体并激活TGF-β信号转导通路。因此，circEIF3I是PDAC的潜在预后生物标志物和治疗靶点。© 2023. BioMed Central Ltd., part of Springer Nature.
Among digestive tract tumours, pancreatic ductal adenocarcinoma (PDAC) shows the highest mortality trend. Moreover, although PDAC metastasis remains a leading cause of cancer-related deaths, the biological mechanism is poorly understood. Recent evidence demonstrates that circular RNAs (circRNAs) play important roles in PDAC progression.Differentially expressed circRNAs in normal and PDAC tissues were screened via bioinformatics analysis. Sanger sequencing, RNase R and actinomycin D assays were performed to confirm the loop structure of circEIF3I. In vitro and in vivo functional experiments were conducted to assess the role of circEIF3I in PDAC. MS2-tagged RNA affinity purification, mass spectrometry, RNA immunoprecipitation, RNA pull-down assay, fluorescence in situ hybridization, immunofluorescence and RNA-protein interaction simulation and analysis were performed to identify circEIF3I-interacting proteins. The effects of circEIF3I on the interactions of SMAD3 with TGFβRI or AP2A1 were measured through co-immunoprecipitation and western blotting.A microarray data analysis showed that circEIF3I was highly expressed in PDAC cells and correlated with TNM stage and poor prognosis. Functional experiments in vitro and in vivo revealed that circEIF3I accelerated PDAC cells migration, invasion and metastasis by increasing MMPs expression and activity. Mechanistic research indicated that circEIF3I binds to the MH2 domain of SMAD3 and increases SMAD3 phosphorylation by strengthening the interactions between SMAD3 and TGFβRI on early endosomes. Moreover, AP2A1 binds with circEIF3I directly and promotes circEIF3I-bound SMAD3 recruitment to TGFβRI on early endosomes. Finally, we found that circEif3i exerts biological functions in mice similar to those of circEIF3I in humans PDAC.Our study reveals that circEIF3I promotes pancreatic cancer progression. circEIF3I is a molecular scaffold that interacts with SMAD3 and AP2A1 to form a ternary complex, that facilitates the recruitment of SMAD3 to early endosomes and then activates the TGF-β signalling pathway. Hence, circEIF3I is a potential prognostic biomarker and therapeutic target in PDAC.© 2023. BioMed Central Ltd., part of Springer Nature.