title: Polyubiquitination of apurinic/apyrimidinic endonuclease 1 by Parkin.
abstract: Apurinic/apyrimidinic endonuclease 1 (APE1) is an essential protein crucial for repair of oxidized DNA damage not only in genomic DNA but also in mitochondrial DNA. Parkin, a tumor suppressor and Parkinson's disease (PD) associated gene, is an E3 ubiquitin ligase crucial for mitophagy. Although DNA damage is known to induce mitochondrial stress, Parkin's role in regulating DNA repair proteins has not been elucidated. In this study, we examined the possibility of Parkin-dependent ubiquitination of APE1. Ectopically expressed APE1 was degraded by Parkin and PINK1 via polyubiquitination in mouse embryonic fibroblast cells. PD-causing mutations in Parkin and PINK1 abrogated APE1 ubiquitination. Interaction of APE1 with Parkin was observed by co-immunoprecipitation, proximity ligation assay, and co-localization in the cytoplasm. N-terminal deletion of 41 amino acid residues in APE1 significantly reduced the Parkin-dependent APE1 degradation. These results suggested that Parkin directly ubiquitinated N-terminal Lys residues in APE1 in the cytoplasm. Modulation of Parkin and PINK1 activities under mitochondrial or oxidative stress caused moderate but statistically significant decrease of endogenous APE1 in human cell lines including SH-SY5Y, HEK293, and A549 cells. Analyses of glioblastoma tissues showed an inverse relation between the expression levels of APE1 and Parkin. These results suggest that degradation of endogenous APE1 by Parkin occur when cells are stressed to activate Parkin, and imply a role of Parkin in maintaining the quality of APE1, and loss of Parkin may contribute to elevated APE1 levels in glioblastoma. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Scott
authors.affiliation: Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Christina A
authors.initials: CA
authors.lastname: Wicker
authors.affiliation: Radiation Oncology, Houston Methodist Research Institute, Houston, Texas.
authors.forename: Rangaswamy
authors.initials: R
authors.lastname: Suganya
authors.affiliation: Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Bithika
authors.initials: B
authors.lastname: Dhar
authors.affiliation: Department of Neurosurgery, University of Kentucky, Lexington, Kentucky.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pittman
authors.affiliation: Departments of Pathology and Neurosurgery, Northwestern University, Chicago, Illinois.
authors.forename: Craig
authors.initials: C
authors.lastname: Horbinski
authors.affiliation: Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Tadahide
authors.initials: T
authors.lastname: Izumi
mesh_terms: D000072283:A549 Cells; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000032:analysis / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D060066:Protein Interaction Maps; D011494:Protein Kinases / Q000032:analysis / Q000378:metabolism; D059748:Proteolysis; D044767:Ubiquitin-Protein Ligases / Q000032:analysis / Q000378:metabolism*; D054875:Ubiquitination; D000099202:PTEN-Induced Putative Kinase
chemical_list: D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D011494:Protein Kinases; D044767:Ubiquitin-Protein Ligases; D000099202:PTEN-Induced Putative Kinase; C111567:parkin protein; C085108:APEX1 protein, human
keywords: APE1; DNA repair; Parkin; glioblastoma; ubiquitination