title: A novel function for hydroxyproline oxidase in apoptosis through generation of reactive oxygen species.
abstract: Proline and hydroxyproline are metabolized by distinct pathways. Proline is important for protein synthesis, as a source of glutamate, arginine, and tricarboxylic acid cycle intermediates, and for participating in a metabolic cycle that shuttles redox equivalents between mitochondria and cytosol. Hydroxyproline, in contrast, is not reutilized for protein synthesis. The first steps in the degradation of proline and hydroxyproline are catalyzed by proline oxidase (POX) and hydroxyproline oxidase (OH-POX), respectively. Because it is well documented that POX is induced by p53 and plays a role in apoptosis, we considered whether OH-POX also participates in the response to cytotoxic stress. In LoVo and RKO cells, which respond to adriamycin with a p53-mediated induction of POX and generation of reactive oxygen species, we found that adriamycin also induced OH-POX gene expression and markedly increased OH-POX catalytic activity, and this increase in activity was not observed in the cell lines HT29 and HCT15, which do not have a functional p53. We also observed an increase in reactive oxygen species generation and activation of caspase-9 with adriamycin in a hydroxyproline-dependent manner. Therefore, we hypothesize that OH-POX plays a role analogous to POX in growth regulation, ROS generation, and activation of the apoptotic cascade.
authors.affiliation: Basic Research Program, SAIC-Frederick, Inc., NCI Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Cooper
authors.forename: Jui
authors.initials: J
authors.lastname: Pandhare
authors.forename: Steven P
authors.initials: SP
authors.lastname: Donald
authors.forename: James M
authors.initials: JM
authors.lastname: Phang
mesh_terms: D017209:Apoptosis; D053453:Caspase 9 / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D008954:Models, Biological; D008956:Models, Chemical; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry* / Q000502:physiology*; D011394:Proline Oxidase / Q000378:metabolism*; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; D000587:Oxidoreductases Acting on CH-NH Group Donors; D011394:Proline Oxidase; C034575:hydroxyproline oxidase; D053453:Caspase 9