Ubiquitinated-protein aggregates form in pancreatic β-cells during diabetes-induced oxidative stress and are regulated by autophagy
Ubiquitinated-protein aggregates form in pancreatic β-cells during diabetes-induced oxidative stress and are regulated by autophagy
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DOI：
10.2337/db06-1160
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发表时间：
2007-04-01
期刊：
影响因子：
7.7
通讯作者：
Brumell, John H.
中科院分区：
文献类型：
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作者：
Kaniuk, Natalia A.;Kiraly, Michael;Brumell, John H.
糖尿病诱导的氧化应激可通过泛素-蛋白酶体系统导致蛋白质错误折叠和降解。本研究检测了Zucker糖尿病脂肪大鼠胰腺切片的蛋白泛素化。我们在胰岛素表达的β细胞和周围的腺泡细胞中观察到大量泛素化蛋白（ub蛋白）聚集。在暴露于高葡萄糖（30 mmol/l） 8-72小时后，在INS1 832/13 β细胞中也观察到这些聚集体的形成，使我们能够进一步表征这种表型。氨三唑（ATZ）诱导的氧化应激足以刺激ub蛋白聚集体的形成。此外，添加抗氧化剂n -乙酰半胱氨酸（NAC）和牛磺酸可显著减少高糖环境下ub蛋白聚集体的形成。purromycin诱导缺陷核糖体产物（DRiP）形成，足以诱导INK 832/13细胞中ub蛋白聚集。然而，在高葡萄糖水平下，环己亚胺（阻断翻译）并没有损害ub蛋白聚集的形成，这表明长寿蛋白是针对这些结构的。在正常培养基（11 mmol/l葡萄糖）中恢复时观察到ub蛋白聚集体的清除。尽管20S蛋白酶体定位于ub蛋白聚集体，但环氧霉素处理不影响清除率，表明蛋白酶体不降解定位于这些结构的蛋白质。自噬抑制剂3MA阻断了恢复过程中聚集体的清除，足以诱导其在正常培养基中形成。总之，这些发现表明，糖尿病诱导的氧化应激诱导泛素化和蛋白质储存到细胞质聚集体，不与胰岛素共定位。自噬，而不是蛋白酶体，在调节它们的形成和降解中起关键作用。据我们所知，这是首次证明自噬可以防御糖尿病期间发生的细胞损伤。
Diabetes-induced oxidative stress can lead to protein misfolding and degradation by the ubiquitin-proteasome system. This study examined protein ubiquitination in pancreatic sections from Zucker diabetic fatty rats. We observed large aggregates of ubiquitinated proteins (Ub-proteins) in insulin-expressing beta-cells and surrounding acinar cells. The formation of these aggregates was also observed in INS1 832/13 beta-cells after exposure to high glucose (30 mmol/l) for 8-72 h, allowing us to further characterize this phenotype. Oxidative stress induced by aminotriazole (ATZ) was sufficient to stimulate Ub-protein aggregate formation. Furthermore, the addition of the antioxidants N-acetyl cysteine (NAC) and taurine resulted in a significant decrease in formation of Ub-protein aggregates in high glucose. Puromycin, which induces defective ribosomal product (DRiP) formation was sufficient to induce Ub-protein aggregates in INK 832/13 cells. However, cycloheximide (which blocks translation) did not impair Ub-protein aggregate formation at high glucose levels, suggesting that long-lived proteins are targeted to these structures. Clearance of Ub-protein aggregates was observed during recovery in normal medium (11 mmol/l glucose). Despite the fact that 20S proteasome was localized to Ub-protein aggregates, epoxomicin treatment did not affect clearance, indicating that the proteasome does not degrade proteins localized to these structures. The autophagy inhibitor 3MA blocked aggregate clearance during recovery and was sufficient to induce their formation in normal medium. Together, these findings demonstrate that diabetes-induced oxidative stress induces ubiquitination and storage of proteins into cytoplasmic aggregates that do not colocalize with insulin. Autophagy, not the proteasome, plays a key role in regulating their formation and degradation. To our knowledge, this is the first demonstration that autophagy acts as a defense to cellular damage incurred during diabetes.