Qi Ma1, Qing-song Hu1, Ran-jie Xu2, Xue-chu Zhen1, Guang-hui Wang1. 1. Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou 215021, China. 2. Laboratory of Molecular Neuropathology, Key Laboratory of Brain Function and Diseases and School of Life Sciences, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, China.
Abstract
AIM: Omi is an ATP-independent serine protease that is necessary for neuronal function and survival. The aim of this study was to investigate the role of protease Omi in regulating differentiation of mouse neuroblastoma cells and to identify the substrate of Omi involved in this process. METHODS: Mouse neuroblastoma N2a cells and Omi protease-deficient mnd2 mice were used in this study. To modulate Omi and E2F1 expression, N2a cells were transfected with expression plasmids, shRNA plasmids or siRNA. Protein levels were detected using immunoblot assays. The interaction between Omi and E2F1 was studied using immunoprecipitation, GST pulldown and in vitro cleavage assays. N2a cells were treated with 20 μmol/L retinoic acid (RA) and 1% fetal bovine serum to induce neurite outgrowth, which was measured using Image J software. RESULTS: E2F1 was significantly increased in Omi knockdown cells and in brain lysates of mnd2 mice, and was decreased in cells overexpressing wild-type Omi, but not inactive Omi S276C. In brain lysates of mnd2 mice, endogenous E2F1 was co-immunoprecipitated with endogenous Omi. In vitro cleavage assay demonstrated that Omi directly cleaved E2F1. Treatment of N2a cells with RA induced marked differentiation and neurite outgrowth accompanied by significantly increased Omi and decreased E2F1 levels, which were suppressed by pretreatment with the specific Omi inhibitor UCF-101. Knockdown of Omi in N2a cells suppressed RA-induced neurite outgrowth, which was partially restored by knockdown of E2F1. CONCLUSION: Protease Omi facilitates neurite outgrowth by cleaving the transcription factor E2F1 in differentiated neuroblastoma cells; E2F1 is a substrate of Omi.
AIM: Omi is an ATP-independent serine protease that is necessary for neuronal function and survival. The aim of this study was to investigate the role of protease Omi in regulating differentiation of mouseneuroblastoma cells and to identify the substrate of Omi involved in this process. METHODS:Mouseneuroblastoma N2a cells and Omi protease-deficient mnd2mice were used in this study. To modulate Omi and E2F1 expression, N2a cells were transfected with expression plasmids, shRNA plasmids or siRNA. Protein levels were detected using immunoblot assays. The interaction between Omi and E2F1 was studied using immunoprecipitation, GST pulldown and in vitro cleavage assays. N2a cells were treated with 20 μmol/L retinoic acid (RA) and 1% fetal bovine serum to induce neurite outgrowth, which was measured using Image J software. RESULTS:E2F1 was significantly increased in Omi knockdown cells and in brain lysates of mnd2mice, and was decreased in cells overexpressing wild-type Omi, but not inactive Omi S276C. In brain lysates of mnd2mice, endogenous E2F1 was co-immunoprecipitated with endogenous Omi. In vitro cleavage assay demonstrated that Omi directly cleaved E2F1. Treatment of N2a cells with RA induced marked differentiation and neurite outgrowth accompanied by significantly increased Omi and decreased E2F1 levels, which were suppressed by pretreatment with the specific Omi inhibitor UCF-101. Knockdown of Omi in N2a cells suppressed RA-induced neurite outgrowth, which was partially restored by knockdown of E2F1. CONCLUSION: Protease Omi facilitates neurite outgrowth by cleaving the transcription factor E2F1 in differentiated neuroblastoma cells; E2F1 is a substrate of Omi.
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