Department of Gastroenterology and Metabology, Graduate School of Medicine, Ehime University, Shitsukawa, Toon, Ehime, 791-0295, Japan.
Division of Molecular Pathology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Sci Rep. 2024 Nov 13;14(1):27768. doi: 10.1038/s41598-024-75142-5.
RNA-dependent protein kinase (PKR) may have a positive regulatory role in controlling tumor growth and progression in hepatocellular carcinoma (HCC). However, the downstream substrates and the molecular mechanism of PKR in the growth and progression of HCC have not been clarified. In this study, mass spectrometry analysis was performed with immunoprecipitated samples, and 4.1R was identified as a protein that binds to PKR. In transfected COS7 cells, an immunoprecipitation experiment showed that 4.1R binds to wild-type PKR, but not to a kinase-deficient mutant PKR, suggesting that PKR binds to 4.1R in a kinase activity-dependent manner. In HCC cell lines, HuH7 and HepG2, the expression level of 4.1R protein was shown to be regulated by protein expression and activation of PKR. Interestingly, high expression of 4.1R, as well as PKR, is associated with a worse prognosis in HCC. PKR increased HCC cell growth in both anchorage-dependent and anchorage-independent manners, whereas 4.1R was involved in HCC cell growth only in an anchorage-independent manner, not in an anchorage-dependent manner. The rescue experiment indicated that increased anchorage-independent growth of HCC cells by PKR might be caused by 4.1R. In conclusion, PKR associates with 4.1R and promotes anchorage-independent growth of HCC. The PKR-4.1R axis might be a new therapeutic target in HCC.
RNA 依赖性蛋白激酶（PKR）可能在控制肝癌（HCC）的肿瘤生长和进展方面具有正向调节作用。然而，PKR 在 HCC 生长和进展中的下游底物和分子机制尚未阐明。在这项研究中，通过免疫沉淀样品进行了质谱分析，鉴定出 4.1R 是与 PKR 结合的蛋白。在转染的 COS7 细胞中，免疫沉淀实验表明 4.1R 与野生型 PKR 结合，但不与激酶缺陷型突变 PKR 结合，提示 PKR 以激酶活性依赖的方式与 4.1R 结合。在 HCC 细胞系 HuH7 和 HepG2 中，PKR 的蛋白表达和激活调节 4.1R 蛋白的表达水平。有趣的是，4.1R 和 PKR 的高表达与 HCC 的预后不良相关。PKR 以依赖锚定和不依赖锚定的方式增加 HCC 细胞的生长，而 4.1R 仅在不依赖锚定的方式，而不是依赖锚定的方式参与 HCC 细胞的生长。挽救实验表明，PKR 可能通过 4.1R 引起 HCC 细胞不依赖锚定的生长增加。总之，PKR 与 4.1R 相关，并促进 HCC 的不依赖锚定的生长。PKR-4.1R 轴可能是 HCC 的一个新的治疗靶点。
