ATP-Citrate Lyase Reduction Mediates Palmitate-induced Apoptosis in Pancreatic Beta Cells
ATP-Citrate Lyase Reduction Mediates Palmitate-induced Apoptosis in Pancreatic Beta Cells
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DOI：
10.1074/jbc.m110.157172
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发表时间：
2010-10-15
影响因子：
4.8
通讯作者：
Johnson, James D.
中科院分区：
文献类型：
--
作者：
Chu, Kwan Yi;Lin, Yalin;Johnson, James D.
细胞外脂质升高，例如游离脂肪酸棕榈酸酯，可诱导胰腺β细胞内质网（ER）应激和细胞凋亡，从而促进2型糖尿病的发生和进展。 ATP-柠檬酸裂解酶 (ACLY) 是细胞脂质生产中的关键酶，在蛋白质组筛选中被确定为棕榈酸酯靶标。我们研究了棕榈酸酯对 ACLY 活性和磷酸化的影响及其在 β 细胞 ER 应激和细胞凋亡中的作用。我们证明，用棕榈酸酯处理 MIN6 细胞、小鼠胰岛和人类胰岛可降低 ACLY 蛋白水平。我们的发现验证了这些体外结果，即来自高脂肪喂养的小鼠的胰岛的 ACLY 显着下降，类似于之前在 2 型糖尿病人胰岛中观察到的情况。棕榈酸降低细胞内乙酰辅酶A水平的程度与 ACLY 抑制剂 SB-204990 相似，表明 ACLY 活性降低。单独的 ACLY 抑制剂足以诱导 CCAAT/增强子结合蛋白同源蛋白 (CHOP) 依赖性 ER 应激和 caspase-3 依赖性细胞凋亡。同样，即使是 shRNA 介导的 ACLY 适度敲低也会导致 β 细胞凋亡和 ER 应激显着增加。化学 ACLY 抑制和棕榈酸酯的作用是非相加的，因此可能由共同机制介导。事实上，ACLY 的过度表达可以防止棕榈酸诱导的 β 细胞死亡。这些观察结果提供了新的证据，表明 ACLY 表达和活性可以被外源脂质抑制，并证明 ACLY 在胰腺 β 细胞存活中发挥关键作用。这些发现为β细胞代谢与程序性细胞死亡之间的联系提供了新的证据。
Elevated extracellular lipids, such as the free fatty acid palmitate, can induce pancreatic beta cell endoplasmic reticulum (ER) stress and apoptosis, thereby contributing to the initiation and progression of type 2 diabetes. ATP-citrate lyase (ACLY), a key enzyme in cellular lipid production, was identified as a palmitate target in a proteomic screen. We investigated the effects of palmitate on ACLY activity and phosphorylation and its role in beta cell ER stress and apoptosis. We demonstrated that treatment of MIN6 cells, mouse islets and human islets with palmitate reduced ACLY protein levels. These in vitro results were validated by our finding that islets from high fat-fed mice had a significant decrease in ACLY, similar to that previously observed in type 2 diabetic human islets. Palmitate decreased intracellular acetyl-CoA levels to a similar degree as the ACLY inhibitor, SB-204990, suggesting a reduction in ACLY activity. ACLY inhibitors alone were sufficient to induce CCAAT/enhancer- binding protein homologues protein (CHOP)-dependent ER stress and caspase-3-dependent apoptosis. Similarly, even modest shRNA-mediated knockdown of ACLY caused a significant increase in beta cell apoptosis and ER stress. The effects of chemical ACLY inhibition and palmitate were nonadditive and therefore potentially mediated by a common mechanism. Indeed, overexpression of ACLY prevented palmitate-induced beta cell death. These observations provide new evidence that ACLY expression and activity can be suppressed by exogenous lipids and demonstrate a critical role for ACLY in pancreatic beta cell survival. These findings add to the emerging body of evidence linking beta cell metabolism with programmed cell death.