Department of Medical Biology, Pomeranian Medical University, Szczecin, Poland.
Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital - Ikerbasque, CIBERehd, San Sebastian, Spain.
Sci Rep. 2021 Nov 4;11(1):21649. doi: 10.1038/s41598-021-01060-5.
The E2 component of the mitochondrial pyruvate dehydrogenase complex (PDC) is the key autoantigen in primary biliary cholangitis (PBC) and STAT3 is an inflammatory modulator that participates in the pathogenesis of many liver diseases. This study investigated whether PDC-E2 interacts with STAT3 in human cholangiocytes (NHC) and hepatocytes (Hep-G2) under cholestatic conditions induced by glyco-chenodeoxycholic acid (GCDC). GCDC induced PDC-E2 expression in the cytoplasmic and nuclear fraction of NHC, whereas in Hep-G2 cells PDC-E2 expression was induced only in the cytoplasmic fraction. GCDC-treatment stimulated phosphorylation of STAT3 in the cytoplasmic fraction of NHC. siRNA-mediated gene silencing of PDC-E2 reduced the expression of pY-STAT3 in NHC but not in HepG2 cells. Immunoprecipitation and a proximity ligation assay clearly demonstrated that GCDC enhanced pY-STAT3 binding to PDC-E2 in the nuclear and cytoplasmic fraction of NHC cells. Staining with Mitotracker revealed mitochondrial co-localization of PDC-E2/pS-STAT3 complexes in NHC and Hep-G2 cells. In cirrhotic PBC livers the higher expression of both PDC-E2 and pY-STAT3 was observed. The immunoblot analysis demonstrated the occurrence of double bands of PDC-E2 protein in control livers, which was associated with a lower expression of pY-STAT3. Our data indicate the interaction between PDC-E2 and phosphorylated STAT3 under cholestatic conditions, which may play a role in the development of PBC.
线粒体丙酮酸脱氢酶复合物（PDC）的 E2 亚基是原发性胆汁性胆管炎（PBC）的关键自身抗原，STAT3 是一种炎症调节剂，参与许多肝脏疾病的发病机制。本研究探讨了在甘氨胆酸（GCDC）诱导的胆汁淤积条件下，PDC-E2 是否与人胆管细胞（NHC）和肝细胞（Hep-G2）中的 STAT3 相互作用。GCDC 诱导 NHC 细胞质和核部分的 PDC-E2 表达，而 Hep-G2 细胞中 PDC-E2 仅在细胞质部分诱导表达。GCDC 处理刺激 NHC 细胞质部分 STAT3 的磷酸化。PDC-E2 的 siRNA 介导的基因沉默减少了 NHC 中的 pY-STAT3 表达，但在 HepG2 细胞中没有。免疫沉淀和接近连接测定清楚地表明，GCDC 增强了 NHC 细胞核和细胞质部分 pY-STAT3 与 PDC-E2 的结合。Mitotracker 染色显示 PDC-E2/pS-STAT3 复合物在 NHC 和 Hep-G2 细胞中的线粒体共定位。在 PBC 肝硬化患者的肝脏中观察到 PDC-E2 和 pY-STAT3 的表达均升高。免疫印迹分析表明在对照肝脏中观察到 PDC-E2 蛋白的双带出现，这与 pY-STAT3 的表达较低有关。我们的数据表明在胆汁淤积条件下 PDC-E2 和磷酸化 STAT3 之间发生相互作用，这可能在 PBC 的发展中起作用。
