The EphB2 tumor suppressor induces autophagic cell death via concomitant activation of the ERK1/2 and PI3K pathways
The EphB2 tumor suppressor induces autophagic cell death via concomitant activation of the ERK1/2 and PI3K pathways
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DOI：
10.4161/cc.9.2.10505
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发表时间：
2010-01-15
期刊：
影响因子：
4.3
通讯作者：
Batist, Gerald
中科院分区：
文献类型：
--
作者：
Kandouz, Mustapha;Haidara, Khadidja;Batist, Gerald
EphB 2是一种酪氨酸激酶受体，已被证明是多种癌症的肿瘤抑制基因。然而，这种功能的机制尚不清楚。我们报告说，EphB 2诱导细胞死亡的形式，不涉及形成凋亡小体或核碎片，而是伴随着广泛的空泡化。透射电子显微镜显示EphB 2过表达细胞中的细胞质空泡类似于自噬体。使用EYFP-LC 3融合蛋白和免疫印迹，我们在EphB 2转染的细胞中检测到LC 3聚集和从I型转化为II型，这两个标志都是自噬。使用shRNA沉默自噬调节基因ATG 5或ATG 7，强烈阻止EphB 2诱导的细胞死亡，进一步证实了其自噬性质。EphB 2表达导致线粒体去极化和细胞色素c从线粒体易位到胞质溶胶。信号通路的映射揭示了EphB 2作用机制的新信息。我们证明了MAPK通路在EphB 2的促死亡作用中是重要的，通过ERK 1/2磷酸化和使用PD 98059对抗EphB 2驱动的细胞死亡来抑制该通路。此外，我们发现，使用自噬抑制剂3 MA抑制III类PI 3 K途径，而不是使用LY 294002抑制I类PI 3 K，也有效地阻断EphB 2诱导的细胞死亡。最后，EphB 2表达使Akt失活，Akt是已知的自噬抑制剂。总之，EphB 2受体诱导通过ERK 1/2和PI 3 K/Akt途径介导的自噬性细胞死亡。
EphB2 is a tyrosine kinase receptor that has been shown to be a tumor suppressor gene in various cancers. However the mechanisms of this function are unknown. We report that EphB2 induces a form of cell death that does not involve the formation of apoptotic bodies or nuclear fragmentation and is instead accompanied by extensive vacuolization. Transmission electron microscopy demonstrates cytoplasmic vacuoles in EphB2-overexpressing cells that resembled autophagosomes. Using an EYFP-LC3 fusion protein and immunoblotting, we detected LC3 aggregation and conversion from form I to form II, both hallmarks of autophagy, in EphB2-transfected cells. Silencing of the autophagy regulating genes ATG5 or ATG7 using shRNAs, strongly prevented EphB2-induced cell death, further confirming its autophagic nature. EphB2 expression results in mitochondrial depolarization and translocation of cytochrome c from the mitochondria to the cytosol. Mapping of signaling pathways revealed novel information about the mechanisms of action of EphB2. We demonstrated that the MAPK pathway is important in the pro-death action of EphB2, through ERK1/2 phosphorylation and inhibition of this pathway using PD98059 counters EphB2-driven cell death. In addition, we found that inhibition of class III PI3K pathway, using the autophagy inhibitor 3MA, but not class I PI3K inhibition using LY294002, also effectively blocks EphB2-induced cell death. Finally, EphB2 expression inactivates Akt, which is a known inhibitor of autophagy. In conclusion, the EphB2 receptor induces an autophagic cell death that is mediated through the ERK1/2 and PI3K/Akt pathways.