Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.
Sci Rep. 2017 Jul 17;7(1):5574. doi: 10.1038/s41598-017-05768-1.
The TRIB1 locus has been linked to both cardiovascular disease and hepatic steatosis. Recent efforts have revealed TRIB1 to be a major regulator of liver function, largely, but not exclusively, via CEBPA degradation. We recently uncovered a functional interaction between TRIB1 and HNF4A, another key regulator of hepatic function, whose molecular underpinnings remained to be clarified. Here we have extended these findings. In hepatoma models, HNF4A levels were found to depend on TRIB1, independently of its impact on CEBPA. Using a reporter assay model, MTTP reporter activity, which depends on HNF4A, positively correlated with TRIB1 levels. Confocal microscopy demonstrated partial colocalization of TRIB1 and HNF4A. Using overexpressed proteins we demonstrate that TRIB1 and HNF4A can form complexes in vivo. Mapping of the interaction interfaces identified two distinct regions within TRIB1 which associated with the N-terminal region of HNF4A. Lastly, the TRIB1-HNF4A interaction resisted competition with a CEPBA-derived peptide, suggesting different binding modalities. Together these findings establish that TRIB1 is required for HNF4A function. This regulatory axis represents a novel CEBPA-independent aspect of TRIB1 function predicted to play an important role in liver physiology.
TRIB1 基因座与心血管疾病和肝脂肪变性均有关联。最近的研究揭示 TRIB1 主要通过 CEBPA 降解来调节肝脏功能,尽管不是唯一的调节方式。我们最近发现 TRIB1 与 HNF4A 之间存在功能相互作用,HNF4A 是另一种肝脏功能的关键调节因子,其分子基础仍需阐明。在这里,我们扩展了这些发现。在肝癌模型中,发现 HNF4A 水平依赖于 TRIB1,而与 CEBPA 无关。使用报告基因检测模型,依赖于 HNF4A 的 MTTP 报告基因活性与 TRIB1 水平呈正相关。共聚焦显微镜显示 TRIB1 和 HNF4A 部分共定位。使用过表达蛋白,我们证明 TRIB1 和 HNF4A 可以在体内形成复合物。相互作用界面的作图确定了 TRIB1 内与 HNF4A 的 N 端区域结合的两个不同区域。最后,TRIB1-HNF4A 相互作用抵抗 CEPBA 衍生肽的竞争,表明存在不同的结合模式。这些发现共同证明了 TRIB1 是 HNF4A 功能所必需的。该调节轴代表了 TRIB1 功能的一种新型 CEBPA 非依赖性方面,预计在肝脏生理学中发挥重要作用。