A decrease in cellular energy status stimulates PERK-dependent eIF2α phosphorylation and regulates protein synthesis in pancreatic β-cells
A decrease in cellular energy status stimulates PERK-dependent eIF2α phosphorylation and regulates protein synthesis in pancreatic β-cells
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DOI：
10.1042/bj20071367
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发表时间：
2008-03-15
影响因子：
4.1
通讯作者：
Herbert, Terence P.
中科院分区：
文献类型：
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作者：
Gomez, Edith;Powell, Mike L.;Herbert, Terence P.
在本研究中，我们证明，在胰腺细胞中，eIF2 α（真核起始因子2 α）的磷酸化反应，在葡萄糖浓度的降低，主要是由激活PERK [PKR（蛋白激酶RNA激活）样内质网激酶]介导的。我们提供的证据表明，这种PERK活性的增加是通过一种潜在的新机制引起的细胞能量状态的降低，该机制独立于IRE1（肌醇需要酶1）的激活和内质网内未折叠新生蛋白的积累。通过显性负性PERK或GADD 34的N端截短突变体（生长停滞和DNA损伤诱导蛋白34）的过表达抑制葡萄糖剥夺细胞中的eIF2a磷酸化导致总蛋白合成速率增加53%。多核糖体分析显示，这与幅度的增加而不是每个mRNA的核糖体数量的增加相一致，表明eIF2 α去磷酸化将迄今未翻译的mRNA动员到多核糖体上。总之，我们表明PERK在低葡萄糖浓度下响应于能量状态的降低而被激活，并且这在胰腺β细胞中葡萄糖调节的蛋白质合成中起重要作用。
In the present study, we demonstrate that, in pancreatic cells, eIF2 alpha (eukaryotic initiation factor 2 alpha) phosphorylation in response to a decrease in glucose concentration is primarily mediated by the activation of PERK [PKR (protein kinase RNA activated)-like endoplasmic reticulum kinase]. We provide evidence that this increase in PERK activity is evoked by a decrease in the energy status of the cell via a potentially novel mechanism that is independent of IRE1 (inositol requiring enzyme 1) activation and the accumulation of unfolded nascent proteins within the endoplasmic reticulum. The inhibition of eIF2a phosphorylation in glucose-deprived cells by the overexpression of dominant-negative PERK or an N-terminal truncation mutant of GADD34 (growth-arrest and DNA-damage-inducible protein 34) leads to a 53 % increase in the rate of total protein synthesis. Polysome analysis revealed that this coincides with an increase in the amplitude but not the number of ribosomes per mRNA, indicating that eIF2 alpha dephosphorylation mobilizes hitherto untranslated mRNAs on to polysomes. In summary, we show that PERK is activated at low glucose concentrations in response to a decrease in energy status and that this plays an important role in glucose-regulated protein synthesis in pancreatic beta-cells.