Proline oxidase, a proapoptotic gene, is induced by troglitazone -: Evidence for both peroxisome proliferator-activated receptor γ-dependent and -independent mechanisms
Proline oxidase, a proapoptotic gene, is induced by troglitazone -: Evidence for both peroxisome proliferator-activated receptor γ-dependent and -independent mechanisms
复制标题
DOI：
10.1074/jbc.m507867200
复制
发表时间：
2006-01-27
影响因子：
4.8
通讯作者：
Phang, JM
中科院分区：
文献类型：
--
作者：
Pandhare, J;Cooper, SK;Phang, JM
脯氨酸氧化酶（Proline oxidase， POX）是一种定位于线粒体内膜的氧化还原酶。我们和其他人已经证明，痘是一个p53诱导的基因，可以通过产生活性氧（ROS）介导细胞凋亡。发现过氧化物酶体增殖体激活受体γ (PPAR γ)配体曲格列酮可激活结肠癌细胞中的痘启动子。PPAR γ配体已被报道在多种癌细胞中诱导凋亡。在表达野生型PPAR γ的HCT116细胞中，曲格列酮增强了PPAR γ与痘启动子中PPAR应答元件的结合，增加了内源性痘的表达。通过拮抗剂GW9662阻断PPAR γ激活或删除痘启动子中PPAR应答元件仅能部分降低痘启动子对曲格列酮的激活，这也表明PPAR γ无关机制的参与。此外，曲格列酮还诱导了HCT116细胞中p53蛋白的表达，这可能是PPAR γ不依赖于POX激活的可能机制，因为POX已被证明是p53诱导的细胞凋亡的下游介质。在突变型p53和突变型PPAR γ的HCT15细胞中，曲格列酮对POX激活没有影响，而在突变型p53和野生型PPAR γ的HT29细胞中，通过配体刺激观察到激活增加，这表明PPAR γ依赖性和γ非依赖性机制都参与了曲格列酮诱导的POX表达。在用曲格列酮处理的HCT116细胞中，获得了痘催化活性的时间和剂量依赖性增加，同时增加了细胞内ROS的产生。我们的研究结果表明，曲格列酮诱导细胞凋亡可能（至少部分）通过靶向POX基因表达，通过PPAR γ依赖性和γ非依赖性机制介导POX产生ROS。
Proline oxidase ( POX) is a redox enzyme localized in the mitochondrial inner membrane. We and others have shown that POX is a p53-induced gene that can mediate apoptosis through generation of reactive oxygen species (ROS). The peroxisome proliferator-activated receptor gamma(PPAR gamma) ligand troglitazone was found to activate the POX promoter in colon cancer cells. PPAR gamma ligands have been reported to induce apoptosis in a variety of cancer cells. In HCT116 cells expressing a wild-type PPAR gamma, troglitazone enhanced the binding of PPAR gamma to PPAR-responsive element in the POX promoter and increased endogenous POX expression. Blocking of PPAR gamma activation either by antagonist GW9662 or deletion of PPAR-responsive element in the POX promoter only partially decreased the POX promoter activation in response to troglitazone, indicating also the involvement of PPAR gamma-independent mechanisms. Further, troglitazone also induced p53 protein expression in HCT116 cells, which may be the possible mechanism for PPAR gamma-independent POX activation, since POX has been shown to be a downstream mediator in p53-induced apoptosis. In HCT15 cells, with both mutant p53 and mutant PPAR gamma, there was no effect of troglitazone on POX activation, whereas in HT29 cells, with a mutant p53 and wild type PPAR gamma, increased activation was observed by ligand stimulation, indicating that both PPAR gamma-dependent and gamma-independent mechanisms are involved in the troglitazone-induced POX expression. A time- and dose-dependent increase in POX catalytic activity was obtained in HCT116 cells treated with troglitazone with a concomitant increase in the production of intracellular ROS. Our results suggest that the induction of apoptosis by troglitazone may, at least in part, be mediated by targeting POX gene expression for generation of ROS by POX both by PPAR gamma-dependent and gamma-independent mechanisms.