食管鳞癌中牙龈卟啉单胞菌通过14-3-3σ调控程序性死亡-配体1蛋白降解

Porphyromonas gingivalis Modulates the Degradation of PD-L1 via 14-3-3σin Esophageal Squamous Cell Carcinoma

牙龈卟啉单胞菌(Porphyromonas gingivalis)是口腔疾病的重要致病菌之一,与人食管鳞癌(ESCC)进展密切相关。然而P.gingivalis促进ESCC发生发展的分子机制尚不十分清楚。该研究探讨了ESCC中P.gingivalis通过诱导程序性死亡-配体1(PD-L1)蛋白表达上调的分子机制。Western印迹和RT-PCR结果显示,KYSE140和KYSE150细胞中14-3-3σ与PD-L1的蛋白质表达呈负相关,但二者的mRNA表达无相关性。免疫共沉淀结果表明,14-3-3σ蛋白通过与PD-L1蛋白结合,促进PD-L1的泛素化降解,P.gingivalis感染干预了14-3-3σ与PD-L1蛋白质复合体形成;KYSE140和KYSE150细胞中14-3-3σ沉默,降低了PD-L1泛素化介导的蛋白质酶体降解,14-3-3σ过表达明显抑制P.gingivalis诱导的PD-L1蛋白表达上调。免疫组化结果进一步证实,在ESCC组织中P.gingivalis丰度与14-3-3σ蛋白表达呈负相关,与PD-L1蛋白表达呈正相关,14-3-3σ与PD-L1的蛋白质表达呈负相关。综上所述,ESCC中P.gingivalis通过下调14-3-3σ蛋白表达,降低14-3-3σ介导的PD-L1蛋白的泛素-蛋白质酶体降解途径,进而抑制抗肿瘤免疫,促进ESCC恶性演进。

Porphyromonas gingivalis(P.gingivalis),an important pathogen of oral cavity inflammation,is closely related to the malignant evolution of human esophageal squamous cell carcinoma(ESCC).However,the molecular underlying mechanism is needed to be further explored.This study explores the molecular mechanism of P.gingivalis-induced upregulation of programmed cell death ligand 1(PD-L1)in ESCC.The 14-3-3σprotein levels were negatively correlated with the PD-L1 protein levels in KYSE140 and KYSE150 cells whereas there were no correlations between 14-3-3σand PD-L1 mRNA levels.Co-immunoprecipitation results show that 14-3-3σpromoted ubiquitination-mediated degradation of PD-L1 by binding to PD-L1 and P.gingivalis blocked the complex formation between 14-3-3σand PD-L1.The knock-down of 14-3-3σin KYSE140 and KYSE150 cells reduced PD-L1 ubiquitination and 14-3-3σoverexpression significantly inhibited the up-regulation of PD-L1 induced by P.gingivalis.Immunohistochemical results further confirmed that the amounts of P.gingivalis were negatively correlated with 14-3-3σprotein levels but positively correlated with PD-L1,whereas there was a significant correlation between 14-3-3σand PD-L1 in ESCC tissues.In conclusion,our results suggest that P.gingivalis reduces the 14-3-3σ-mediated ubiquitin-proteasome degradation pathway of PD-L1 by down-regulation of the 14-3-3σprotein in ESCC and thus enhances the malignant progression of ESCC through inhibition the anti-tumor immunity.