MODY3相关蛋白HNF1α第249位丝氨酸突变导致小鼠葡萄糖代谢异常

The Mutation of the MODY3-related Protein HNF1α at Ser249 Leads to Abnormal Glucose Metabolism in Mice

肝细胞核因子1α(HNF1α)不仅是调节葡萄糖代谢的重要转录因子,还参与肝、胰等多个器官中蛋白质合成、物质代谢、增殖分化相关基因的表达调控。HNF1α突变或表达异常引发包括青少年糖尿病3型(maturity onset diabetes of young 3,MODY3)在内的多种代谢疾病。Ser249是HNF1α重要的功能位点,该位点受ATM蛋白激酶直接磷酸化修饰,并可能是ATM蛋白激酶影响葡萄糖代谢的效应靶点,也可能是共济失调毛细血管扩张症(ataxia telangiectasia,AT)患者糖代谢异常的致病靶点。为进一步研究Ser249磷酸化在体内的功能,本文构建人源野生型HNF1α转基因小鼠(WT小鼠)和HNF1αS249A转基因小鼠(S249A小鼠),对其基础代谢水平和葡萄糖代谢能力进行检测。相较于对照小鼠,S249A小鼠的多项基础代谢指标异常,WT小鼠未显示差异;但当小鼠接受刺激后,无论是注射葡萄糖,还是丙酮酸或胰岛素,相较于各自的对照小鼠,WT小鼠都表现出更强的反应性,而S249A小鼠的糖异生反应和胰岛素敏感性均未显示出差异。实时定量PCR结果表明,WT小鼠肝的多个糖代谢基因表达上调,但S249A小鼠肝中糖代谢基因上调幅度明显小于WT小鼠。本研究提示,HNF1αSer249突变导致小鼠糖代谢异常,可能与磷酸化修饰失调进而影响其转录活性有关。

Hepatocyte nuclear factor 1α（HNF1α） is one of the most important transcription factors in the liver and pancreas,and it is involved in metabolism,protein synthesis,proliferation,and differentiation through gene expression regulation.In humans,HNF1α mutations or abnormal expressions cause a variety of metabolic diseases,including maturity onset diabetes of young 3（MODY3）.Ser249 is an important functional site of HNF1α,which is directly phosphorylated by the protein kinase,ataxia telangiectasia mutated（ATM）.ATM-dependent phosphorylation of Ser249 may be involved in glucose metabolism and abnormal glucose metabolism in ataxia telangiectasia（AT） patients.To furtherinvestigate the function of Ser249 phosphorylation in vivo,we constructed wild-type human HNF1αtransgenic mice（WT mice） and HNF1αS249A transgenic mice（S249 A mice）,and the basal metabolic level and glucose metabolism were assessed.Compared with the control mice,WT mice did not show a difference in a number of basal metabolic markers whereas S249 A mice showed abnormalities.When mice were stimulated with either glucose,pyruvate or insulin,WT mice showed more reactivity compared to control,while S249 A mice had no difference in gluconeogenesis and insulin sensitivity.Real-time PCR results showed that the expression of various glucose metabolism genes in the liver of WT mice were upregulated,while the increase in S249 A mice was significantly smaller than WT.This study suggests that mutation in HNF1α Ser249 or phosphorylation abnormality may lead to aberrant glucose metabolism in mice.