title: Knockdown of phosphotyrosyl phosphatase activator induces apoptosis via mitochondrial pathway and the attenuation by simultaneous tau hyperphosphorylation.
abstract: Phosphotyrosyl phosphatase activator (PTPA) is decreased in the brains of Alzheimer's disease (AD) and the AD transgenic mouse models. Here, we investigated whether down-regulation of PTPA affects cell viability and the underlying mechanisms. We found that PTPA was located in the integral membrane of mitochondria, and knockdown of PTPA induced cell apoptosis in HEK293 and N2a cell lines. PTPA knockdown decreased mitochondrial membrane potential and induced Bax translocation into the mitochondria with a simultaneous release of Cyt C, activation of caspase-3, cleavage of poly (DNA ribose) polymerase (PARP), and decrease in Bcl-xl and Bcl-2 protein levels. Over-expression of Protein phosphatase 2A (PP2A) catalytic subunit (PP2AC ) did not rescue the apoptosis induced by PTPA knockdown, and PTPA knockdown did not affect the level of and their phosphorylation of mitogen-activated protein kinases (MAPKs), indicating that PP2A and MAPKs were not involved in the apoptosis induced by PTPA knockdown. In the cells with over-expression of tau, PTPA knockdown induced PP2A inhibition and tau hyperphosphorylation but did not cause significant cell death. These data suggest that PTPA deficit causes apoptotic cell death through mitochondrial pathway and simultaneous tau hyperphosphorylation attenuates the PTPA-induced cell death. Phosphotyrosyl phosphatase activator (PTPA) is decreased in the brains of Alzheimer's disease (AD) and AD transgenic mouse models. Here, we investigated whether down-regulation of PTPA affects cell viability. We found that PTPA located in the integral membrane of mitochondria, and knockdown of PTPA induced cell apoptosis in HEK293 and N2a cell lines by decreasing mitochondrial membrane potential, which leads to translocation of Bax and a simultaneous release of Cyt C. In the cells with tau over-expression, PTPA knockdown inactivated PP2A to phosphorylate tau to avoid cell apoptosis which induced by PTPA knockdown.
authors.affiliation: Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Dan-Ju
authors.initials: DJ
authors.lastname: Luo
authors.forename: Qiong
authors.initials: Q
authors.lastname: Feng
authors.forename: Zhi-Hao
authors.initials: ZH
authors.lastname: Wang
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Sun
authors.forename: Qun
authors.initials: Q
authors.lastname: Wang
authors.forename: Jian-Zhi
authors.initials: JZ
authors.lastname: Wang
authors.forename: Gong-Ping
authors.initials: GP
authors.lastname: Liu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D009447:Neuroblastoma / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D012844:Sincalide / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D051028:bcl-2-Associated X Protein; D016875:tau Proteins; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D010749:Phosphoprotein Phosphatases; C087440:PTPA protein, human; D012844:Sincalide
keywords: Alzheimer's disease; Apoptosis; Cyt C; PTPA; mitochondrial pathway; tau hyperphosphorylation