Hypoxia reduces ER-to-Golgi protein trafficking and increases cell death by inhibiting the adaptive unfolded protein response in mouse beta cells
Hypoxia reduces ER-to-Golgi protein trafficking and increases cell death by inhibiting the adaptive unfolded protein response in mouse beta cells
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DOI：
10.1007/s00125-016-3947-y
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发表时间：
2016-07-01
期刊：
影响因子：
8.2
通讯作者：
Laybutt, D. Ross
中科院分区：
文献类型：
--
作者：
Bensellam, Mohammed;Maxwell, Emma L.;Laybutt, D. Ross
目的/假设 缺氧可能导致 2 型糖尿病和胰岛移植中的 β 细胞衰竭。适应性未折叠蛋白反应（UPR）是内质网（ER）稳态所必需的。在这里，我们研究了缺氧是否调节β细胞中的UPR以及适应性UPR在缺氧应激期间所起的作用。方法将小鼠胰岛和MIN6细胞暴露于各种氧(O-2)张力。使用小干扰 (si)RNA 敲低 DNA 损伤诱导转录因子 3 (DDIT3)、缺氧诱导转录因子 (HIF)1 α 和 HSPA5； Hspa5 也过度表达。使用db/db小鼠。结果在糖尿病小鼠的胰岛中，缺氧反应基因在体内上调，但在糖尿病前期的db/db小鼠中没有上调。在分离的小鼠胰岛和 MIN6 细胞中，O-2 剥夺（1-5% vs 20%；4-24 小时）显着降低了适应性 UPR 基因的表达，包括 Hspa5、Hsp90b1、Fkbp11 和剪接 Xbp1。辅酶蛋白复合体基因（Copa、Cope、Copg [也称为 Copg1]、Copz1 和 Copz2）和 ER 至高尔基体的蛋白质运输也减少，而凋亡基因（Ddit3、Atf3 和 Trb3 [也称为 Trib3]）、c-Jun N 末端激酶 (JNK) 磷酸化和细胞死亡增加。抑制 JNK（而非 HIF1 α）可恢复适应性 UPR 基因表达和 ER 至高尔基体蛋白运输，同时防止缺氧后的凋亡基因和细胞死亡。 DDIT3 敲除延迟了适应性 UPR 的丧失，并部分防止缺氧诱导的细胞死亡。后一种反应因 HSPA5 敲除而被阻止。最后，Hspa5 过表达可显着防止缺氧诱导的细胞死亡。结论/解释缺氧通过 JNK 和 DDIT3 激活抑制 β 细胞中的适应性 UPR，但与 HIF1 α 无关。适应性 UPR 的下调有助于减少内质网到高尔基体的蛋白质运输，并增加缺氧应激期间 β 细胞的死亡。
Aims/hypothesis Hypoxia may contribute to beta cell failure in type 2 diabetes and islet transplantation. The adaptive unfolded protein response (UPR) is required for endoplasmic reticulum (ER) homeostasis. Here we investigated whether or not hypoxia regulates the UPR in beta cells and the role the adaptive UPR plays during hypoxic stress.Methods Mouse islets and MIN6 cells were exposed to various oxygen (O-2) tensions. DNA-damage inducible transcript 3 (DDIT3), hypoxia-inducible transcription factor (HIF)1 alpha and HSPA5 were knocked down using small interfering (si)RNA; Hspa5 was also overexpressed. db/db mice were used.Results Hypoxia-response genes were upregulated in vivo in the islets of diabetic, but not prediabetic, db/db mice. In isolated mouse islets and MIN6 cells, O-2 deprivation (1-5% vs 20%; 4-24 h) markedly reduced the expression of adaptive UPR genes, including Hspa5, Hsp90b1, Fkbp11 and spliced Xbp1. Coatomer protein complex genes (Copa, Cope, Copg [also known as Copg1], Copz1 and Copz2) and ER-to-Golgi protein trafficking were also reduced, whereas apoptotic genes (Ddit3, Atf3 and Trb3 [also known as Trib3]), c-Jun N-terminal kinase (JNK) phosphorylation and cell death were increased. Inhibition of JNK, but not HIF1 alpha, restored adaptive UPR gene expression and ER-to-Golgi protein trafficking while protecting against apoptotic genes and cell death following hypoxia. DDIT3 knockdown delayed the loss of the adaptive UPR and partially protected against hypoxia-induced cell death. The latter response was prevented by HSPA5 knockdown. Finally, Hspa5 overexpression significantly protected against hypoxia-induced cell death.Conclusions/interpretation Hypoxia inhibits the adaptive UPR in beta cells via JNK and DDIT3 activation, but independently of HIF1 alpha. Downregulation of the adaptive UPR contributes to reduced ER-to-Golgi protein trafficking and increased beta cell death during hypoxic stress.