Elevated nucleocytoplasmic glycosylation by O-GlcNAc results in insulin resistance associated with defects in Akt activation in 3T3-L1 adipocytes
Elevated nucleocytoplasmic glycosylation by O-GlcNAc results in insulin resistance associated with defects in Akt activation in 3T3-L1 adipocytes
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DOI：
10.1073/pnas.072072399
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发表时间：
2002-04-16
影响因子：
11.1
通讯作者：
Hart, GW
中科院分区：
文献类型：
--
作者：
Vosseller, K;Wells, L;Hart, GW
通过己糖胺生物合成途径（HSP）的葡萄糖流量增加被认为介导糖尿病中高血糖诱导的胰岛素抗性。HSP的终产物UDP-β-N-乙酰葡糖胺（GlcNAc）是分泌途径中复杂糖基化和O-连接GlcNAc（O-GlcNAc）添加到核胞质蛋白的供体糖核苷酸。通过药理学抑制O-GlcNAc酶（催化O-GlcNAc从蛋白质中去除的酶）和O-（2-乙酰氨基-2-脱氧-D-吡喃葡萄糖基亚基）氨基-N-苯基-氨基甲酸酯（PUGNAc）阻断O-GlcNAc翻译后修饰的循环。PUGNAc处理增加了3 T3-L1脂肪细胞中O-GlcNAc的水平并引起胰岛素抵抗。葡萄糖胺和长期胰岛素治疗通过HSP诱导的胰岛素抵抗与核质蛋白上O-GlcNAc水平增加相关。而胰岛素受体自身磷酸化和胰岛素受体底物2酪氨酸磷酸化不受PUGNAc抑制O-GlcNAcase的影响，Akt在Thr-308和糖原合成酶激酶3 β在Ser-9的下游磷酸化受到抑制。PUGNAc诱导的胰岛素抵抗与几种蛋白质的O-GlcNAc修饰增加有关，包括胰岛素受体底物1和β-连环蛋白，这是胰岛素信号传导的两种重要效应物。这些结果表明，O-GlcNAc水平的升高减弱胰岛素信号传导，并有助于增加通过HSP的通量导致脂肪细胞中胰岛素抵抗的机制。
increased flux of glucose through the hexosamine biosynthetic pathway (HSP) is believed to mediate hyperglycemia-induced insulin resistance in diabetes. The end product of the HSP, UDP-beta-N-acetylglucosamine (GlcNAc), is a donor sugar nucleotide for complex glycosylation in the secretory pathway and for O-linked GlcNAc (O-GlcNAc) addition to nucleocytoplasmic proteins. Cycling of the O-GlcNAc posttranslational modification was blocked by pharmacological inhibition of O-GlcNAcase, the enzyme that catalyzes O-GlcNAc removal from proteins, with O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenyl-carbamate (PUGNAc). PUGNAc treatment increased levels of O-GlcNAc and caused insulin resistance in 3T3-L1 adipocytes. Insulin resistance induced through the HSP by glucosamine and chronic insulin treatment correlated with increased O-GlcNAc levels on nucleocytoplasmic proteins. Whereas insulin receptor autophosphorylation and insulin receptor substrate 2 tyrosine phosphorylation were not affected by PUGNAc inhibition of O-GlcNAcase, downstream phosphorylation of Akt at Thr-308 and glycogen synthase kinase 3beta at Ser-9 was inhibited. PUGNAc-induced insulin resistance was associated with increased O-GlcNAc modification of several proteins including insulin receptor substrate 1 and beta-catenin, two important effectors of insulin signaling. These results suggest that elevation of O-GlcNAc levels attenuate insulin signaling and contribute to the mechanism by which increased flux through the HSP leads to insulin resistance in adipocytes.