Akt激活通过刺激mTOR保护胰岛β细胞免受AMPK介导的死亡。

Akt activation protects pancreatic beta cells from AMPK-mediated death through stimulation of mTOR.

作者信息

Cai Ying, Wang Qidi, Ling Zhidong, Pipeleers Daniel, McDermott Paul, Pende Mario, Heimberg Harry, Van de Casteele Mark

机构信息

Diabetes Research Center, Brussels Free University, VUB, Partner of the Juvenile Diabetes Research Center for Beta Cell Therapy in Europe, Laarbeeklaan 103, B-1090 Brussels, Belgium.

出版信息

Biochem Pharmacol. 2008 May 15;75(10):1981-93. doi: 10.1016/j.bcp.2008.02.019. Epub 2008 Feb 26.

Abstract

Sustained activation of AMP-activated protein kinase (AMPK) induces apoptosis in several cell types. In pancreatic beta cells this occurs under glucose limitation, or in the presence of the pharmacological AMPK activator 5-aminoimidazole-4-carboxamide-riboside (AICAR). It is unknown whether Akt activation can counteract AMPK-mediated apoptosis, nor whether mTOR activation downstream of Akt mediates any survival signal in these conditions. We report that expression of a constitutively active form of Akt increases mTOR activity and prevents apoptosis upon AMPK activation. Akt-mediated survival was inhibited by rapamycin. Expression of a constitutively active form of the mTOR target ribosomal protein S6 kinase (S6K) or of translation factor eIF4E reduced apoptosis by glucose limitation, and co-expression of S6K and eIF4E protected beta cells to the same extent as active Akt. The protective effects of active Akt and S6K were associated with increased cellular protein synthesis activity. It is concluded that Akt stimulation of mTOR and subsequent activation of the targets by which mTOR affects protein translation are required and sufficient mechanisms for Akt-mediated survival of beta cells undergoing sustained AMPK activation.

摘要

AMP激活的蛋白激酶(AMPK)的持续激活在多种细胞类型中诱导细胞凋亡。在胰腺β细胞中,这种情况发生在葡萄糖受限的情况下,或存在药理学上的AMPK激活剂5-氨基咪唑-4-甲酰胺核苷(AICAR)时。尚不清楚Akt激活是否能抵消AMPK介导的细胞凋亡,也不清楚Akt下游的mTOR激活在这些条件下是否介导任何存活信号。我们报告,组成型活性形式的Akt的表达增加了mTOR活性,并在AMPK激活时防止细胞凋亡。雷帕霉素抑制了Akt介导的存活。组成型活性形式的mTOR靶标核糖体蛋白S6激酶(S6K)或翻译因子eIF4E的表达通过葡萄糖限制减少了细胞凋亡,并且S6K和eIF4E的共表达对β细胞的保护程度与活性Akt相同。活性Akt和S6K的保护作用与细胞蛋白质合成活性的增加有关。得出的结论是,Akt对mTOR的刺激以及随后mTOR影响蛋白质翻译的靶标的激活是Akt介导的经历持续AMPK激活的β细胞存活所必需且充分的机制。

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