Ubiquitin-specific protease 2a stabilizes MDM4 and facilitates the p53-mediated intrinsic apoptotic pathway in glioblastoma.
The mouse double minute 4 (MDM4) oncoprotein may inhibit tumorigenesis by regulating the apoptotic mediator p53. Ubiquitin-specific protease 2a (USP2a) is a deubiquitinating enzyme that protects MDM4 against degradation, so USP2-MDM4 interaction may be a key determinant of the malignant potential of human cancers. MDM4 and USP2a, as well as the MDM4-USP2a complex, were more highly expressed in glioblastoma multiforme tissue samples from patients with good prognosis compared with patients with poor prognosis. Analysis of the prognostic parameters indicated that MDM4 expression was positively correlated with an increased likelihood for survival. Compared with the poor prognosis patients, mitochondria from good prognosis glioma patients contained higher levels of both MDM4 and the proapoptotic protein p53Ser46(P). In U87MG glioma cell line, the overexpression of MDM4 enhanced ultraviolet (UV)-induced cytochrome c release and apoptosis. In contrast, MDM4 knockdown decreased mitochondrial p53Ser46(P) levels and rescued cells from UV-induced apoptosis. The expression of MDM4 and USP2a were positively correlated with each other. MDM4-USP2a complexes were found only in the cytoplasmic fraction, whereas the mitochondrial fraction contained MDM4-p53Ser46(P) and MDM4-Bcl-2 complexes. Overexpression of USP2a increased p53 and p53Ser46(P) levels in the mitochondria, whereas simultaneous MDM4 knockdown completely reversed this effect. UV-induced apoptosis was reduced by USP2a knockdown but restored by the simultaneous overexpression of MDM4. This apoptotic response was reduced by knockdown of p53 but not p21. Our results suggest that USP2a binds to and stabilizes MDM4; thus in turn, it enhances the mitochondrial localization of p53 and promotes apoptosis in glioma cells.
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China, Department of Neurosurgery, the 105th Hospital of PLA, Hefei 230000, Anhui Province, China.
Chun-Lin
CL
Wang
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Jun-Yu
JY
Wang
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Zhen-Yang
ZY
Liu
Department of Pathology, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Xiao-Mei
XM
Ma
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Xiao-Wen
XW
Wang
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Hai
H
Jin
The Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences/Shanghai JiaoTong University School of Medicine, 225 South Chongqing Road, Shanghai 200025, China and Department of Nuclear Medicine, Shanghai 10th People's Hospital, Tongji University School of Medicine, 301 Yan Chang Road, Shanghai 200072, China.
Xiao-Ping
XP
Zhang
The Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences/Shanghai JiaoTong University School of Medicine, 225 South Chongqing Road, Shanghai 200025, China and.
Da
D
Fu
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China, luyicheng1947@163.com lijunhou2010@163.com.
Li-Jun
LJ
Hou
Department of Neurosurgery, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China, luyicheng1947@163.com.
Yi-Cheng
YC
Lu
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005909:Glioblastoma / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D051379:Mice; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase
C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D010450:Endopeptidases; C108665:USP2 protein, human; D043222:Ubiquitin Thiolesterase