Knockdown of phosphotyrosyl phosphatase activator induces apoptosis via mitochondrial pathway and the attenuation by simultaneous tau hyperphosphorylation

Authors

  • Dan-Ju Luo,

    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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  • Qiong Feng,

    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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  • Zhi-Hao Wang,

    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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  • Dong-Sheng Sun,

    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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  • Qun Wang,

    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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  • Jian-Zhi Wang,

    Corresponding author
    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
    • Address correspondence and reprint requests to Gong-Ping Liu or Jian-Zhi Wang, Department of Pathophysiology, Key Laboratory of Neurological Diseases of Education Committee of China, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, 430030 Wuhan, China. E-mails: liugp111@mail.hust.edu.cn; or wangjz@mails.tjmu.edu.cn

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  • Gong-Ping Liu

    Corresponding author
    1. Department of Pathophysiology, Key Laboratory of Chinese Ministry of Education for Neurological Diseases, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
    • Address correspondence and reprint requests to Gong-Ping Liu or Jian-Zhi Wang, Department of Pathophysiology, Key Laboratory of Neurological Diseases of Education Committee of China, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, 430030 Wuhan, China. E-mails: liugp111@mail.hust.edu.cn; or wangjz@mails.tjmu.edu.cn

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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.

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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.

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