Glucose deprivation stimulates O-GlcNAc modification of proteins through up-regulation of O-linked N-acetylglucosaminyltransferase
Glucose deprivation stimulates O-GlcNAc modification of proteins through up-regulation of O-linked N-acetylglucosaminyltransferase
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DOI：
10.1074/jbc.m707328200
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发表时间：
2008-03-07
影响因子：
4.8
通讯作者：
McClain, Donald A.
中科院分区：
文献类型：
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作者：
Taylor, Rodrick P.;Parker, Glendon J.;McClain, Donald A.
O-连接的 N-乙酰氨基葡萄糖 (O-GlcNAc) 是蛋白质的翻译后修饰，具有营养传感机制的作用。在这里，我们报告了在广泛的葡萄糖浓度范围内 O-GlcNAcylation 的调节。我们发现在葡萄糖剥夺条件下，有限数量的蛋白质会显着诱导 O-GlcNAc 修饰。治疗后 12 小时开始，与正常葡萄糖（5 mM；p = 0.008）中培养的细胞相比，葡萄糖剥夺的人肝细胞癌细胞 (HepG2) 总 O-GlcNAc 修饰增加了 7.8 倍。葡萄糖剥夺诱导的 O-GlcNAcNA 酰化的一些靶标与响应高葡萄糖 (20 mM) 或葡萄糖胺 (10 mM) 治疗而修饰的靶标不同，表明葡萄糖剥夺和葡萄糖过量的靶向作用不同。糖原合酶的 O-GlcNAc 酰化随着葡萄糖剥夺而显着增加，这种 O-GlcNAc 的增加导致糖原合酶活性降低 60% (p = 0.004)。 O-GlcNAc 修饰的增加不是由 UDP-GlcNAc（O-GlcNAc 酰化的限速底物）增加介导的。相反，核细胞质 O 连接 N-乙酰氨基葡萄糖转移酶 (OGT) 的 mRNA 在葡萄糖剥夺后 6 小时内增加了 3.4 倍 (p = 0.006)。 12 小时内，OGT 蛋白与正常葡萄糖处理的细胞相比增加了 1.7 倍（p = 0.01）。此外，12 小时葡萄糖剥夺会导致 O-GlcNAcase 蛋白水平下降 49% (p = 0.03)。我们得出的结论是，葡萄糖剥夺刺激的 O-GlcNAc 修饰增加是由于 OGT 增加和 O-GlcNAcase 水平降低所致，并且这些变化影响细胞代谢，从而使糖原合酶失活。
O-Linked N-acetylglucosamine (O-GlcNAc) is a post-translational modification of proteins that functions as a nutrient sensing mechanism. Here we report on regulation of O-GlcNAcylation over a broad range of glucose concentrations. We have discovered a significant induction of O-GlcNAc modification of a limited number of proteins under conditions of glucose deprivation. Beginning 12 h after treatment, glucose-deprived human hepatocellular carcinoma (HepG2) cells demonstrate a 7.8-fold increase in total O-GlcNAc modification compared with cells cultured in normal glucose (5 mM; p = 0.008). Some of the targets of glucose deprivation-induced O-GlcNAcylation are distinct from those modified in response to high glucose (20 mM) or glucosamine (10 mM) treatment, suggesting differential targeting with glucose deprivation and glucose excess. O-GlcNAcylation of glycogen synthase is significantly increased with glucose deprivation, and this O-GlcNAc increase contributes to a 60% decrease (p = 0.004) in glycogen synthase activity. Increased O-GlcNAc modification is not mediated by increased UDP-GlcNAc, the rate-limiting substrate for O-GlcNAcylation. Rather, the mRNA for nucleocytoplasmic O-linked N-acetylglucosaminyltransferase (OGT) increases 3.4-fold within 6 h of glucose deprivation (p = 0.006). Within 12 h, OGT protein increases 1.7-fold (p = 0.01) compared with normal glucose-treated cells. In addition, 12-h glucose deprivation leads to a 49% decrease in O-GlcNAcase protein levels (p = 0.03). We conclude that increased O-GlcNAc modification stimulated by glucose deprivation results from increased OGT and decreased O-GlcNAcase levels and that these changes affect cell metabolism, thus inactivating glycogen synthase.