title: Monoamine oxidase A and repressor R1 are involved in apoptotic signaling pathway.
abstract: Monoamine oxidase A (MAO A) degrades serotonin, norepinephrine, and dopamine and produces reactive oxygen that may cause neuronal cell death. We have previously reported that a novel transcription factor R1 (RAM2/CDCA7L/JPO2) inhibits the MAO A promoter and enzymatic activities. This study reports the roles of MAO A and R1 in apoptosis and proliferation. We have found that in serum starvation-induced apoptosis, p38 kinase, MAO A, and caspase-3 were increased, whereas Bcl-2 and R1 were reduced. Using a p38 kinase inhibitor, R1 overexpression, and MAO A inhibitor, we have shown that MAO A and R1 are downstream of p38 kinase and Bcl-2, but upstream of caspase-3. Inhibition of MAO A prevents cell apoptosis. This notion was further supported by the finding that serum starvation-induced apoptosis is reduced in cortical brain cells from MAO A-deficient mice compared with WT. In addition, we found that MAO A and R1 are involved in the c-Myc-induced proliferative signaling pathway in the presence of serum. Immunoprecipitation and immunohistochemistry experiments indicate that the oncogene c-Myc colocalizes with R1 and induces R1 gene expression. Using R1 overexpression, R1 small interfering RNA, and a MAO A inhibitor, we found that R1 and MAO A act upstream of cyclin D1 and E2F1. In summary, this study demonstrates the functions of MAO A and its repressor R1 in apoptotic signaling pathways.
authors.affiliation: Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Ou
authors.forename: Kevin
authors.initials: K
authors.lastname: Chen
authors.forename: Jean C
authors.initials: JC
authors.lastname: Shih
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000201:enzymology; D016895:Culture Media, Serum-Free; D019938:Cyclin D1 / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008995:Monoamine Oxidase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins; D015398:Signal Transduction
chemical_list: C513450:CDCA7L protein, human; D016895:Culture Media, Serum-Free; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D019938:Cyclin D1; D008995:Monoamine Oxidase; D020928:Mitogen-Activated Protein Kinases