DYRK1B通过AKT/p300信号通路调控肝脏糖代谢的机制研究

Hepatic glucose metabolism is essential for maintaining glucose homeostasis, in which histone modifications play a key role. Previous studies indicated that DYRK1B participated in the regulation of cell proliferation and differentiation, while a recent genetic research showed that DYRK1B p.R102C mutation directly lead to metabolic syndrome in three pedigrees and increased mRNA levels of hepatic gluconeogenesis in HepG2 cell line. However, the mechanism that DYRK1B involving in hepatic glucose metabolism remained unclear. In our preliminary research, we found that the expression of hepatic glycogen synthesis and glycolysis related genes decreased significantly in shRNA-DYRK1B LO2 cell line. In addition, immunofluorescence (IF) displayed a co-localization of DYRK1B and AKT in nucleus. Moreover, AKT phosphorylation level and histone H3K27 acetylation level decreased significantly after knocking down DYRK1B in LO2 cell line, indicating that DYRK1B may regulate epigenetic modification through AKT signaling pathway. Therefore, our project plans to explore how DYRK1B regulates histone acetylation and affects AKT signaling pathway in the liver, so as to maintain blood glucose homeostasis and regulate insulin sensitivity based on Dyrk1b knockout mice and epigenetic research tools.

肝脏葡萄糖代谢对维持血糖稳态至关重要，而组蛋白修饰此过程中发挥重要作用。本项目聚焦于在肝脏表达的核蛋白双特异性酪氨酸激酶1B(DYRK1B)，其主要参与调控细胞增殖分化。一项基于大型家系的遗传研究表明，该基因p.R102C突变是导致代谢综合征的致病突变，后者在HepG2细胞系中可增加肝糖异生关键基因的表达。但是该基因参与肝脏葡萄糖代谢的机制尚不清楚。本项目前期在LO2细胞系中敲减DYRK1B基因发现，肝脏糖原合成及糖酵解相关基因均显著下调，免疫荧光实验表明，DYRK1B在核内与AKT共定位，敲减DYRK1B后，AKT磷酸化水平及组蛋白H3K27乙酰化水平显著降低，提示DYRK1B可能通过AKT信号通路调控表观遗传修饰。故本项目拟基于Dyrk1b敲除小鼠，结合表观遗传研究手段，解析DYRK1B在肝细胞内如何影响AKT信号通路和调控组蛋白乙酰化，从而维持血糖稳态和胰岛素敏感性。

人类基因组研究表明，双特异性酪氨酸磷酸化调节激酶1B（DYRK1B）的突变与代谢综合征有关。然而，其分子机制仍不明确。这里我们证明，DYRK1B的表达水平被禁食和糖尿病小鼠所诱导。通过体内和体外研究，我们发现DYRK1B促进了肝脏的糖异生过程和葡萄糖不耐受，而肝脏特异性的DYRK1B基因敲除小鼠则免受饮食引起的高血糖影响。从机制上讲，DYRK1B与FoxO1相互作用并使其磷酸化，主要是在T467S468处，以促进其细胞核的定位。此外，DYRK1B抑制AKT介导的FoxO1在T24和S256的磷酸化，并增强核保留。这导致了糖异生关键酶的表达增加。最后，DYRK1B的激酶特异性抑制剂被证明能显著降低糖尿病小鼠的血糖水平。总之，这些结果使人们对DYRK1B在糖代谢中的作用有了新的认识，这可能为治疗糖尿病提供一个新的治疗目标。