Glucose represses connexin36 in insulin-secreting cells
Glucose represses connexin36 in insulin-secreting cells
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DOI：
10.1242/jcs.02600
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发表时间：
2005-11-15
影响因子：
4
通讯作者：
Haefliger, JA
中科院分区：
文献类型：
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作者：
Allagnat, F;Martin, D;Haefliger, JA
缝隙连接蛋白36(Cx36)参与控制胰岛素产生细胞的功能。在这项研究中，我们研究了在胰岛素产生细胞中Cx36的表达是否受葡萄糖的调节。葡萄糖导致胰岛素分泌细胞系和新分离的大鼠胰岛中Cx36的表达显著减少。这种下降以剂量和时间依赖的方式出现在信使核糖核酸和蛋白质水平。2-脱氧葡萄糖部分复制了葡萄糖的作用，而氨基葡萄糖、3-O-甲基-D-葡萄糖和亮氨酸则无效。此外，KCl诱导的β细胞去极化对Cx36的表达没有影响，这表明葡萄糖代谢和ATP的产生不是葡萄糖诱导的Cx36下调所必需的。Forsklin模拟葡萄糖对Cx36的抑制作用。L类钙通道阻滞剂硝苯地平不能抑制葡萄糖或Forsklin对Cx36表达的影响，但cAMP依赖的蛋白激酶抑制剂H89可完全钝化它们对Cx36表达的影响。对人Cx36启动子的4kb片段进行了鉴定和测序。由多种Cx36启动子片段驱动的报告基因活性表明，Cx36的抑制需要高度保守的cAMP反应元件(Cre)的存在。凝胶迁移率改变分析表明，在高糖存在时，抑制物Cre调节剂1(CREM-1)的结合活性增强。综上所述，这些数据为葡萄糖通过cAMP-PKA途径抑制Cx36的表达提供了证据，cAMP-PKA途径激活了Cre结合蛋白家族的一个成员。
The gap-junction protein connexin36 (Cx36) contributes to control the functions of insulin-producing cells. In this study, we investigated whether the expression of Cx36 is regulated by glucose in insulin-producing cells. Glucose caused a significant reduction of Cx36 in insulin-secreting cell lines and freshly isolated pancreatic rat islets. This decrease appeared at the mRNA and the protein levels in a dose- and time-dependent manner. 2-Deoxyglucose partially reproduced the effect of glucose, whereas glucosamine, 3-O-methyl-D-glucose and leucine were ineffective. Moreover, KCl-induced depolarization of beta-cells had no effect on Cx36 expression, indicating that glucose metabolism and ATP production are not mandatory for glucose-induced Cx36 downregulation. Forskolin mimicked the repression of Cx36 by glucose. Glucose or forskolin effects on Cx36 expression were not suppressed by the L-type Ca2+-channel blocker nifedipine but were fully blunted by the cAMP-dependent protein kinase (PKA) inhibitor H89. A 4 kb fragment of the human Cx36 promoter was identified and sequenced. Reportergene activity driven by various Cx36 promoter fragments indicated that Cx36 repression requires the presence of a highly conserved cAMP responsive element (CRE). Electrophoretic-mobility-shift assays revealed that, in the presence of a high glucose concentration, the binding activity of the repressor CRE-modulator 1 (CREM-1) is enhanced. Taken together, these data provide evidence that glucose represses the expression or Cx36 through the cAMP-PKA pathway, which activates a member of the CRE binding protein family.