Connor Kip M, Subbaram Sita, Regan Kevin J, Nelson Kristin K, Mazurkiewicz Joseph E, Bartholomew Peter J, Aplin Andrew E, Tai Yu-Tzu, Aguirre-Ghiso Julio, Flores Sonia C, Melendez J Andres
Centers for Immunology and Microbial Disease, Neuropharmacology and Neuroscience, and Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208, USA.
J Biol Chem. 2005 Apr 29;280(17):16916-24. doi: 10.1074/jbc.M410690200. Epub 2005 Feb 8.
Recent studies have demonstrated that the tumor suppressor PTEN (phosphatase and tensin homolog deleted from chromosome 10), the antagonist of the phosphosphoinositol-3-kinase (PI3K) signaling cascade, is susceptible to H2O2-dependent oxidative inactivation. This study describes the use of redox-engineered cell lines to identify PTEN as sensitive to oxidative inactivation by mitochondrial H2O2. Increases in the steady state production of mitochondrial derived H2O2, as a result of manganese superoxide dismutase (Sod2) overexpression, led to PTEN oxidation that was reversed by the coexpression of the H2O2-detoxifying enzyme catalase. The accumulation of an oxidized inactive fraction of PTEN favored the formation of phosphatidylinositol 3,4,5-triphosphate at the plasma membrane, resulting in increased activation of Akt and modulation of its downstream targets. PTEN oxidation in response to mitochondrial H2O2 enhanced PI3K signaling, leading to increased expression of the key regulator of angiogenesis, vascular endothelial growth factor. Overexpression of PTEN prevented the H2O2-dependent increase in vascular endothelial growth factor promoter activity and immunoreactive protein, whereas a mutant PTEN (G129R), lacking phosphatase activity, did not. Furthermore, mitochondrial generation of H2O2 by Sod2 promoted endothelial cell sprouting in a three-dimensional in vitro angiogenesis assay that was attenuated by catalase coexpression or the PI3K inhibitor LY2949002. Moreover, Sod2 overexpression resulted in increased in vivo blood vessel formation that was H2O2-dependent as assessed by the chicken chorioallantoic membrane assay. Our findings provide the first evidence for the involvement of mitochondrial H2O2 in regulating PTEN function and the angiogenic switch, indicating that Sod2 can serve as an alternative physiological source of the potent signaling molecule, H2O2.
近期研究表明，肿瘤抑制因子PTEN（第10号染色体缺失的磷酸酶及张力蛋白同源物）作为磷酸肌醇-3-激酶（PI3K）信号级联反应的拮抗剂，易受H2O2依赖性氧化失活作用的影响。本研究描述了利用氧化还原工程改造的细胞系来确定PTEN对线粒体H2O2介导的氧化失活敏感。由于锰超氧化物歧化酶（Sod2）过表达导致线粒体衍生的H2O2稳态生成增加，进而引起PTEN氧化，而过表达H2O2解毒酶过氧化氢酶可逆转这种氧化。PTEN氧化失活部分的积累有利于质膜上磷脂酰肌醇3,4,5-三磷酸的形成，导致Akt激活增加及其下游靶点的调节。响应线粒体H2O2的PTEN氧化增强了PI3K信号传导，导致血管生成关键调节因子血管内皮生长因子的表达增加。PTEN过表达可阻止H2O2依赖性的血管内皮生长因子启动子活性和免疫反应性蛋白增加，而缺乏磷酸酶活性的突变型PTEN（G129R）则不能。此外，在三维体外血管生成试验中，Sod2介导的线粒体H2O2生成促进内皮细胞发芽，而过表达过氧化氢酶或PI3K抑制剂LY2949002可减弱这种促进作用。此外，通过鸡胚绒毛尿囊膜试验评估，Sod2过表达导致体内血管生成增加，且这种增加依赖于H2O2。我们的研究结果首次证明线粒体H2O2参与调节PTEN功能和血管生成开关，表明Sod2可作为强效信号分子H2O2的另一种生理来源。
