Insulin-like Growth Factor 1 Regulates the Expression of ATP-Binding Cassette Transporter A1 in Pancreatic Beta Cells
Insulin-like Growth Factor 1 Regulates the Expression of ATP-Binding Cassette Transporter A1 in Pancreatic Beta Cells
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胰岛素样生长因子 1 调节胰腺 β 细胞中 ATP 结合盒转运蛋白 A1 的表达
DOI：
10.1055/s-0035-1569272
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发表时间：
2016-05-01
影响因子：
2.2
通讯作者：
Murao, K.
中科院分区：
文献类型：
--
作者：
Lyu, J.;Imachi, H.;Murao, K.
摘要胰腺β细胞的ATP结合盒转运体A1（ABCA 1）影响胰岛素分泌和胆固醇稳态。本研究调查是否胰岛素样生长因子1（IGF-1），介导的ABCA 1基因表达的刺激，也可以干扰磷脂酰肌醇3-激酶（PI 3-K）级联。ABCA 1的表达进行了研究，通过实时聚合酶链反应（PCR），蛋白质印迹分析，并在大鼠胰岛素分泌INS-1细胞与IGF-1孵育的报告基因测定。通过染色质免疫沉淀（ChIP）试验评估叉头盒O 1（FoxO 1）蛋白与ABCA 1启动子的结合。ABCA 1蛋白水平增加，以响应IGF-1浓度的上升。实时定量PCR分析显示ABCA 1 mRNA表达显著增加。然而，在沉默IGF-1受体后，这两种作用都受到抑制。与其对内源性ABCA 1 mRNA水平的影响平行，IGF-1诱导含有ABCA 1启动子的报告构建体的活性，而它被PI 3-K的特异性抑制剂LY 294002废除。组成型活性Akt刺激ABCA 1启动子的活性，并且Akt的显性负突变体或ABCA 1启动子中的FoxO 1响应元件的诱变废除了IGF-1刺激启动子活性的能力。ChIP分析表明，FoxO 1通过直接结合ABCA 1启动子区域介导其转录活性。FoxO 1的敲低破坏了IGF-1对ABCA 1表达的影响。此外，IGF-1促进胆固醇流出并降低胰腺脂毒性。这些结果表明，PI 3-K/Akt/FoxO 1通路有助于响应IGF-1刺激调节ABCA 1表达。
Abstract ATP-binding cassette transporter A1 (ABCA1) in pancreatic beta cells influences insulin secretion and cholesterol homeostasis. The present study investigates whether insulin-like growth factor 1 (IGF-1), which mediates stimulation of ABCA1 gene expression, could also interfere with the phosphatidylinositol 3-kinase (PI3-K) cascade. ABCA1 expression was examined by real-time polymerase chain reaction (PCR), Western blot analysis, and a reporter gene assay in rat insulin-secreting INS-1 cells incubated with IGF-1. The binding of forkhead box O1 (FoxO1) protein to the ABCA1 promoter was assessed by a chromatin immunoprecipitation (ChIP) assay. ABCA1 protein levels increased in response to rising concentrations of IGF-1. Real-time PCR analysis showed a significant increase in ABCA1 mRNA expression. However, both effects were suppressed after silencing the IGF-1 receptor. In parallel with its effect on endogenous ABCA1 mRNA levels, IGF-1 induced the activity of a reporter construct containing the ABCA1 promoter, while it was abrogated by LY294002, a specific inhibitor of PI3-K. Constitutively active Akt stimulated activity of the ABCA1 promoter, and a dominant-negative mutant of Akt or mutagenesis of the FoxO1 response element in the ABCA1 promoter abolished the ability of IGF-1 to stimulate promoter activity. A ChIP assay showed that FoxO1 mediated its transcriptional activity by directly binding to the ABCA1 promoter region. The knockdown of FoxO1 disrupted the effect of IGF-1 on ABCA1 expression. Furthermore, IGF-1 promoted cholesterol efflux and reduced the pancreatic lipotoxicity. These results demonstrate that the PI3-K/Akt/FoxO1 pathway contributes to the regulation of ABCA1 expression in response to IGF-1 stimulation.