title: Parkin suppresses the expression of monoamine oxidases.
abstract: Mutations of parkin are linked to early onset Parkinson disease. Here we show that stable transfection of parkin in the human dopaminergic neuroblastoma cell line SH-SY5Y markedly reduced the activities of both monoamine oxidase (MAO) A and B. The amount of 3,4-dihydroxyphenylacetic acid, which is produced during dopamine oxidation by MAO, was greatly reduced by parkin overexpression. Radioligand binding assays showed that MAO binding sites were decreased accordingly. Consistent with these, MAO-B protein level was much lower, whereas the amount of MAO-A protein was not determined due to the lack of a suitable antibody. Co-transfection of either MAO with parkin in HEK293 cells did not significantly alter ubiquitination and degradation of each MAO. When we measured MAO expression by real-time quantitative reverse transcription-PCR, marked reductions were seen in SH-SY5Y cells stably expressing parkin compared with the parental cells or a control line stably transfected with luciferase. In addition, parkin mutants defective in E3 ligase activity exhibited different effects on MAO expression. We found that parkin also significantly decreased mRNA levels of both MAOs in the mouse fibroblast cell line NIH3T3. Furthermore, MAO expression was significantly increased in human B lymphocyte cell lines derived from Parkinson disease patients with homozygous but not heterozygous deletion of exon 4 of parkin. Together these results suggest that parkin suppresses MAO expression. This function may limit the production of reactive oxygen species generated by MAO in dopamine oxidation and would, thus, be beneficial to the survival of dopaminergic neurons.
authors.affiliation: Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA.
authors.forename: Houbo
authors.initials: H
authors.lastname: Jiang
authors.forename: Qian
authors.initials: Q
authors.lastname: Jiang
authors.forename: Wenhua
authors.initials: W
authors.lastname: Liu
authors.forename: Jian
authors.initials: J
authors.lastname: Feng
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D001665:Binding Sites; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002472:Cell Transformation, Viral; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006719:Homovanillic Acid / Q000032:analysis / Q000378:metabolism; D006801:Humans; D051379:Mice; D008954:Models, Biological; D008995:Monoamine Oxidase / Q000378:metabolism*; D009154:Mutation; D041681:NIH 3T3 Cells; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism; D010300:Parkinson Disease / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D015102:3,4-Dihydroxyphenylacetic Acid; D008995:Monoamine Oxidase; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; C001746:3-methoxytyramine; D004298:Dopamine; D006719:Homovanillic Acid