title: Overexpression of proline oxidase induces proline-dependent and mitochondria-mediated apoptosis.
abstract: Proline oxidase (POX), a mitochondrial inner-membrane protein, catalyzes the rate-limiting oxidation of proline to pyrroline- 5-carboxylate (P5C). Previously we showed that overexpression of POX is associated with generation of reactive oxygen species (ROS) and apoptosis in POX-inducible colorectal cancer cells, DLD-1.POX. We also showed expression of mitochondrial MnSOD partially blunts POX-induced ROS generation and apoptosis. To further investigate the molecular basis of POX-induced apoptosis, we utilized the DLD-1.POX cells to show that cells overproducing POX exhibit an L-proline-dependent apoptotic response. The apoptotic effect is specific for L-proline, detectable at 0.2 mM, maximal at 1 mM, and occurs during 48-72 h following the addition of L-proline to cells with maximally induced POX. The apoptotic response is mitochondria-mediated with release of cytochrome c, activation of caspase-9, chromatin condensation/DNA fragmentation, and cell shrinkage. We conclude that in the presence of proline, high POX activity is sufficient to induce mitochondria-mediated apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine, Albuquerque, NM, USA.
authors.forename: Chien-an A
authors.initials: CA
authors.lastname: Hu
authors.forename: Steven P
authors.initials: SP
authors.lastname: Donald
authors.forename: Jian
authors.initials: J
authors.lastname: Yu
authors.forename: Wei-Wen
authors.initials: WW
authors.lastname: Lin
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Liu
authors.forename: Gary
authors.initials: G
authors.lastname: Steel
authors.forename: Cassandra
authors.initials: C
authors.lastname: Obie
authors.forename: David
authors.initials: D
authors.lastname: Valle
authors.forename: James M
authors.initials: JM
authors.lastname: Phang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology*; D008954:Models, Biological; D011392:Proline / Q000494:pharmacology*; D011394:Proline Oxidase / Q000096:biosynthesis / Q000235:genetics*; D013997:Time Factors
chemical_list: D045304:Cytochromes c; D011392:Proline; D011394:Proline Oxidase; D053453:Caspase 9