AMP-activated protein kinase-independent inhibition of hepatic mitochondrial oxidative phosphorylation by AICA riboside
AMP-activated protein kinase-independent inhibition of hepatic mitochondrial oxidative phosphorylation by AICA riboside
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DOI：
10.1042/bj20070105
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发表时间：
2007-06-15
影响因子：
4.1
通讯作者：
Hue, Louis
中科院分区：
文献类型：
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作者：
Guigas, Bruno;Taleux, Nellie;Hue, Louis
AICA核苷(5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside)在细胞中被广泛用于激活AMPK(AMP激活的蛋白激酶)，AMPK是一种参与细胞能量平衡的代谢传感器。在本研究中，我们研究了AICA核苷对线粒体氧化-磷酸化的影响。AICA核苷呈剂量依赖性抑制大鼠肝细胞对寡霉素敏感的JO(2)(耗氧率)。AICA核苷浓度为0.1 mM时，P-I(无机磷)、ATP、AMP和总腺嘌呤核苷含量也呈下降趋势。有趣的是，在缺乏α1和α2 AMPK催化亚基的小鼠肝细胞中，与野生型小鼠相比，基础JO(2)和几种线粒体蛋白的表达显著减少，这表明线粒体的生物发生受到干扰。然而，AICA核苷对JO(2)的抑制在突变小鼠中仍然存在，因此显然不是由AMPK介导的。在通透性肝细胞中，这种抑制作用不再明显，这表明这可能是由于Z核苷在细胞内积累和/或腺嘌呤核苷酸和P-I的丢失。ZMP确实通过直接作用于呼吸链复合体I而抑制大鼠线粒体的呼吸。此外，在与果糖孵育的细胞中，AICA核苷对JO(2)的抑制作用也被增强，以耗竭腺嘌呤核苷酸和P-I。我们得出结论，AICA核苷通过AMPK非依赖性机制抑制细胞呼吸，这种机制可能是细胞内P-I耗竭和ZMP积聚共同作用的结果。我们的数据还表明，AICA核苷的细胞效应不一定是由AMPK激活引起的，对它们的解释应该谨慎对待。
AICA riboside (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside) has been extensively used in cells to activate the AMPK (AMP-activated protein kinase), a metabolic sensor involved in cell energy homoeostasis. In the present study, we investigated the effects of AICA riboside on mitochondrial oxidative; phosphorylation. AICA riboside was found to dose-dependently inhibit the oligomycin-sensitive JO(2) (oxygen consumption rate) of isolated rat hepatocytes. A decrease in P-i (inorganic phosphate), ATP, AMP and total adenine nuclectide contents was also observed with AICA riboside concentrations > 0.1 mM. Interestingly, in hepatocytes from mice lacking both alpha 1 and alpha 2 AMPK catalytic subunits, basal JO(2) and expression of several mitochondrial proteins were significantly reduced compared with wild-type mice, suggesting that mitochondrial biogenesis was perturbed. However, inhibition of JO(2) by AICA riboside was still present in the mutant mice and thus was clearly not mediated by AMPK. In permeabilized hepatocytes, this inhibition was no longer evident, suggesting that it could be due to intracellular accumulation of Z nuclectides and/or loss of adenine nucleotides and P-i. ZMP did indeed inhibit respiration in isolated rat mitochondria through a direct effect on the respiratory-chain complex I. In addition, inhibition of JO(2) by AICA riboside was also potentiated in cells incubated with fructose to deplete adenine nucleotides and P-i. We conclude that AICA riboside inhibits cellular respiration by an AMPK-independent mechanism that likely results from the combined intracellular P-i depletion and ZMP accumulation. Our data also demonstrate that the cellular effects of AICA riboside are not necessarily caused by AMPK activation and that their interpretation should be taken with caution.