title: An Mdm2 antagonist, Nutlin-3a, induces p53-dependent and proteasome-mediated poly(ADP-ribose) polymerase1 degradation in mouse fibroblasts.
abstract: Nutlin-3a (Nutlin) is an Mdm2 inhibitor and is potent to stabilize p53, which is a tumor-suppressor involved in various biological processes such as cell cycle regulation, DNA repair, and apoptosis. Here we demonstrate that Nutlin treatment in mouse fibroblast cell lines reduces the protein levels of poly(ADP-ribose) polymerase1 (Parp1). Parp1 functions in DNA repair, replication, and transcription and has been regarded as a target molecule for anti-cancer therapy and protection from ischemia/reperfusion injury. In this study, first we found that Nutlin, but not DNA damaging agents such as camptothecin (Cpt), induced a decrease in the Parp1 protein levels. This reduction was not associated with cell death and not observed in p53 deficient cells. Next, because Nutlin treatment did not alter Parp1 mRNA levels, we expected that a protein degradation pathway might contribute to this phenomenon. Predictably, a proteasome inhibitor, MG132, inhibited the Nutlin-induced decrease in the levels of Parp1 protein. These results show that Nutlin induces the proteasomal degradation of Parp1 in a p53-dependent manner. Thus, this study demonstrates characterization of a novel regulatory mechanism of Parp1 protein. This novel regulatory mechanism of Parp1 protein level could contribute to development of inhibitors of the Parp1 signaling pathway.
authors.affiliation: Department of Molecular Pathology and Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Yamazaki 2641, Noda, Chiba 278-0022, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsushima
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Okita
authors.forename: Misako
authors.initials: M
authors.lastname: Oku
authors.forename: Wataru
authors.initials: W
authors.lastname: Nagai
authors.forename: Masaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Higami
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology*; D007093:Imidazoles / Q000494:pharmacology*; D051379:Mice; D010879:Piperazines / Q000494:pharmacology*; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects* / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D010879:Piperazines; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D046988:Proteasome Endopeptidase Complex