Akt mediates mitochondrial protection in cardiomyocytes through phosphorylation of mitochondrial hexokinase-II
Akt mediates mitochondrial protection in cardiomyocytes through phosphorylation of mitochondrial hexokinase-II
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DOI：
10.1038/sj.cdd.4402285
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发表时间：
2008-03-01
影响因子：
12.4
通讯作者：
Brown, J. H.
中科院分区：
文献类型：
--
作者：
Miyamoto, S.;Murphy, A. N.;Brown, J. H.
AKT激活支持心肌细胞抗缺血/再灌流的存活，缺血/再灌流通过开放线粒体通透性转换孔(PT-Pore)诱导细胞死亡。用白血病抑制因子(LIF)激活Akt可阻止H_2O_2处理心肌细胞引起的线粒体去极化。这种保护作用即使在LIF处理的心肌细胞被通透性和通过升高钙离子而引起线粒体去极化的情况下也能观察到。细胞分级研究表明，LIF处理增加了线粒体部分的总Akt和磷酸化Akt。此外，LIF还增加了Akt与HK-II的结合。HK-II包含Akt磷酸化的共同序列，LIF处理诱导PI3K和Akt依赖的HK-II磷酸化。在分离的成年小鼠心肌线粒体中加入重组激酶活性Akt，可刺激HK-II的磷酸化，同时抑制钙离子诱导细胞色素c释放的能力。当HK-II通过与葡萄糖6-磷酸或HK-II解离肽孵育而从线粒体解离时，这种保护被阻止。最后，LIF增加HK-II与线粒体的结合，从线粒体解离HK-II可减弱LIF对H_2O_2诱导的心肌细胞线粒体去极化的保护作用。我们认为Akt在线粒体水平上具有直接作用，这种作用是通过HK-II的磷酸化而实现的，从而保护线粒体免受氧化剂或钙离子刺激的PT-孔洞的开放。
Akt activation supports survival of cardiomyocytes against ischemia/reperfusion, which induces cell death through opening of the mitochondrial permeability transition pore (PT-pore). Mitochondrial depolarization induced by treatment of cardiomyocytes with H2O2 is prevented by activation of Akt with leukemia inhibitory factor (LIF). This protective effect is observed even when cardiomyocytes treated with LIF are permeabilized and mitochondrial depolarization is elicited by elevating Ca2+. Cell fractionation studies demonstrate that LIF treatment increases both total and phosphorylated Akt in the mitochondrial fraction. Furthermore, the association of Akt with HK-II is increased by LIF. HK-II contains consensus sequences for phosphorylation by Akt and LIF treatment induces PI3K- and Akt-dependent HK-II phosphorylation. Addition of recombinant kinase-active Akt to isolated adult mouse heart mitochondria stimulates phosphorylation of HK-II and concomitantly inhibits the ability of Ca2+ to induce cytochrome c release. This protection is prevented when HK-II is dissociated from mitochondria by incubation with glucose 6-phosphate or HK-II-dissociating peptide. Finally LIF increases HK-II association with mitochondria and dissociation of HK-II from mitochondria attenuates the protective effect of LIF on H2O2-induced mitochondrial depolarization in cardiomyocytes. We conclude that Akt has a direct effect at the level of the mitochondrion, which is mediated via phosphorylation of HK-II and results in protection of mitochondria against oxidant or Ca2+-stimulated PT-pore opening.