Endoplasmic Reticulum Stress-Induced Activation of Activating Transcription Factor 6 Decreases cAMP-Stimulated Hepatic Gluconeogenesis via Inhibition of CREB
Endoplasmic Reticulum Stress-Induced Activation of Activating Transcription Factor 6 Decreases cAMP-Stimulated Hepatic Gluconeogenesis via Inhibition of CREB
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DOI：
10.1210/en.2009-0641
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发表时间：
2010-02-01
期刊：
影响因子：
4.8
通讯作者：
Lee, In-Kyu
中科院分区：
文献类型：
--
作者：
Seo, Hye-Young;Kim, Mi-Kyung;Lee, In-Kyu
编码关键肝糖异生酶（包括磷酸烯醇丙酮酸羧激酶（PEPCK）和葡萄糖-6-磷酸酶（G6Pase））的基因表达在转录水平上受到转录因子和辅助因子网络（包括 cAMP 反应元件结合蛋白（CREB））的调节。有人认为，肝脏内质网（ER）应激的增加会损害肝脏葡萄糖代谢。然而，ER应激对肝糖异生的直接影响仍不清楚。在这里，我们研究了 ER 应激是否影响肝脏糖异生，以及该过程是否是通过抑制 cAMP 介导的 CREB 激活来激活转录因子 6 (ATF6) 介导的。 cAMP 刺激剂毛喉素和 8-溴腺苷-cAMP 增加 H4IIE 大鼠肝癌细胞中 PEPCK 和 G6Pase mRNA 的表达，而衣霉素或毒胡萝卜素诱导的 ER 应激降低了毛喉素或 8-溴腺苷-cAMP 处理的细胞中这些基因的表达。在瞬时转染研究中，ATF6 抑制 PEPCK 和 G6Pase 启动子。此外，H4IIE 细胞中腺病毒介导的 ATF6 过度表达降低了毛喉素刺激的 PEPCK 和 G6Pase 基因表达。此外，小干扰RNA对内源性ATF6表达的抑制恢复了ER应激诱导的PEPCK和G6Pase基因表达的抑制。 ATF6 的瞬时转染抑制了 PEPCK 和 G6Pase 启动子上 CREB 的反式激活，凝胶迁移测定表明 Ad-ATF6 抑制毛喉素刺激的 CREB DNA 结合活性。最后，我们发现 ATF6 的表达降低了小鼠禁食诱导的 PEPCK、G6Pase mRNA 表达和血糖水平。总而言之，这些数据扩展了我们对 ER 应激和 ATF6 对肝脏糖异生调节的理解。 （内分泌学 151：561-568，2010）
The expression of genes encoding key hepatic gluconeogenic enzymes, including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), is regulated at the transcriptional level by a network of transcription factors and cofactors, including cAMP response element-binding protein (CREB). It has been suggested that increased endoplasmic reticulum (ER) stress in the liver impairs hepatic glucose metabolism. However, the direct effect of ER stress on hepatic gluconeogenesis is still not clear. Here, we investigated whether ER stress influences hepatic gluconeogenesis and whether this process is mediated by activating transcription factor 6 (ATF6) through the inhibition of cAMP-mediated activation of CREB. A cAMP stimulant, forskolin, and 8-bromoadenosine-cAMP increased PEPCK and G6Pase mRNA expression in H4IIE rat hepatoma cells, and ER stress induced by tunicamycin or thapsigargin decreased the expression of these genes in forskolin or 8-bromoadenosine-cAMP-treated cells. In a transient transfection study, ATF6 inhibited the PEPCK and G6Pase promoters. Also, adenovirus-mediated overexpression of ATF6 in H4IIE cells decreased forskolin-stimulated PEPCK and G6Pase gene expression. Moreover, the inhibition of endogenous ATF6 expression by small interfering RNAs restored the ER stress-induced suppression of PEPCK and G6Pase gene expression. Transient transfection of ATF6 inhibited transactivation by CREB on the PEPCK and G6Pase promoters, and a gel shift assay showed that Ad-ATF6 inhibits forskolin-stimulated CREB DNA-binding activity. Finally, we found that expression of ATF6 decreased fasting-induced PEPCK, G6Pase mRNA expression, and blood glucose levels in mice. Taken together, these data extend our understanding of ER stress and the regulation of liver gluconeogenesis by ATF6. (Endocrinology 151: 561-568, 2010)