Glucose regulates islet amyloid polypeptide gene transcription in a PDX1-and calcium-dependent manner
Glucose regulates islet amyloid polypeptide gene transcription in a PDX1-and calcium-dependent manner
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DOI：
10.1074/jbc.m908045199
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发表时间：
2000-05-19
影响因子：
4.8
通讯作者：
Docherty, K
中科院分区：
文献类型：
--
作者：
Macfarlane, WM;Campbell, SC;Docherty, K
胰岛淀粉样多肽（IAPP）和胰岛素在胰岛β细胞中表达，它们响应于葡萄糖浓度的变化而共同分泌，并且它们的mRNA水平也受葡萄糖调节。这两个基因的启动子共享相似的顺式作用序列元件，并且都结合同源域转录因子PDX 1，其在葡萄糖调节胰岛素启动子和胰岛素mRNA水平中起重要作用。在这里，我们研究PDX 1在葡萄糖调节人IAPP启动子中的作用。缺乏PDX 1的人β细胞系（NES 2 Y）的可用性促进了实验，NES 2 Y细胞也缺乏可操作的K-ATP通道，导致钙信号传导失去控制。我们以前使用这些细胞来证明胰岛素基因的葡萄糖调节依赖于PDX 1，而不是钙。在小鼠β-细胞系Mine中，葡萄糖（16 mM）刺激-222至+450 IAPP启动子构建体的活性与在0.5 mM葡萄糖中观察到的值相比增加3.5-4倍。在NES 2 Y细胞中，葡萄糖不能刺激IAPP启动子的转录激活。在NES 2 Y细胞中PDX 1的过表达未能恢复IAPP启动子的葡萄糖响应性控制，仅在PDX 1存在下，当通过两个K-ATP通道亚基SUR 1和Kir6.2的过表达恢复正常钙信号传导时，观察到葡萄糖对IAPP启动子的影响。钙的重要性进一步强调了葡萄糖刺激的LAPP启动子活性被钙通道阻滞剂维拉帕米（50 μ M）抑制的实验。维拉帕米进一步显示抑制葡萄糖对IAPP mRNA水平的刺激作用。这些结果表明，与胰岛素启动子一样，IAPP启动子的葡萄糖调节依赖于PDX 1的活性，但与胰岛素启动子不同，它还需要另一种尚未表征的因子的活性，其活性是钙依赖性的。
Islet amyloid polypeptide (IAPP) and insulin are expressed in the p-cells of the islets of Langerhans, They are co-secreted in response to changes in glucose concentration, and their mRNA levels are also regulated by glucose. The promoters of both genes share similar cis-acting sequence elements, and both bind the homeodomain transcription factor PDX1, which plays an important role in the regulation of the insulin promoter and insulin mRNA levels by glucose. Here we examine the role of PDX1 in the regulation of the human IAPP promoter by glucose. The experiments were facilitated by the availability of a human p-cell line (NES2Y) that lacks PDX1, NES2Y cells also lack operational K-ATP channels, resulting in a loss of control of calcium signaling. We have previously used these cells to show that glucose regulation of the insulin gene is dependent on PDX1, but not calcium. In the mouse p-cell line Mine, glucose (16 mM) Stimulated a 3.5-4-fold increase in the activity of a -222 to +450 IAPP promoter construct compared with values observed in 0.5 mM glucose. In NES2Y cells, glucose failed to stimulate transcriptional activation of the IAPP promoter. Overexpression of PDX1 in NES2Y cells failed to reinstate glucose-responsive control of the IAPP promoter, Glucose effects on the IAPP promoter were observed only in the presence of PDX1 when normal calcium signaling was restored by overexpression of the two K-ATP channel subunits SUR1 and Kir6.2. The importance of calcium was further emphasized by an experiment in which glucose-stimulated LAPP promoter activity was inhibited by the calcium channel blocker verapamil (50 mu M). Verapamil was further shown to inhibit the stimulatory effect of glucose on IAPP mRNA levels, These results demonstrate that like the insulin promoter, glucose regulation of the IAPP promoter is dependent on the activity of PDX1, but unlike the insulin promoter, it additionally requires the activity of another, as yet uncharacterized factor(s), the activity of which is calcium-dependent.