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Nagata E, Nonaka T, Moriya Y, Fujii N, Okada Y, Tsukamoto H, Itoh J, Okada C, Satoh T, Arai T, Hasegawa M, Takizawa S. Inositol Hexakisphosphate Kinase 2 Promotes Cell Death in Cells with Cytoplasmic TDP-43 Aggregation. Mol Neurobiol 2015; 53:5377-83. [PMID: 26440668 DOI: 10.1007/s12035-015-9470-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 09/30/2015] [Indexed: 12/30/2022]
Abstract
TAR DNA-binding protein 43 (TDP-43) has been identified as a major component of ubiquitin-positive inclusions in the brains and spinal cords of patients with frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) or amyotrophic lateral sclerosis (ALS). The phosphorylated C-terminal fragment of TDP-43 forms aggregates in the neuronal cytoplasm, possibly resulting in neuronal cell death in patients with FTLD-U or ALS. The inositol pyrophosphate known as diphosphoinositol pentakisphosphate (InsP7) contains highly energetic pyrophosphate bonds. We previously reported that inositol hexakisphosphate kinase type 2 (InsP6K2), which converts inositol hexakisphosphate (InsP6) to InsP7, mediates cell death in mammalian cells. Moreover, InsP6K2 is translocated from the nucleus to the cytosol during apoptosis. In this study, we verified that phosphorylated TDP-43 co-localized and co-bound with InsP6K2 in the cytoplasm of anterior horn cells of the spinal cord. Furthermore, we verified that cell death was augmented in the presence of cytoplasmic TDP-43 aggregations and activated InsP6K2. However, cells with only cytoplasmic TDP-43 aggregation survived because Akt activity increased. In the presence of both TDP-43 aggregation and activated InsP6K2 in the cytoplasm of cells, the expression levels of HSP90 and casein kinase 2 decreased, as the activity of Akt decreased. These conditions may promote cell death. Thus, InsP6K2 could cause neuronal cell death in patients with FTLD-U or ALS. Moreover, InsP6K2 plays an important role in a novel cell death pathway present in FTLD-U and ALS.
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Affiliation(s)
- Eiichiro Nagata
- Department of Neurology, Tokai University School of Medicine, Isehara, Japan.
- , 143 Shimo-Kasuya, Isehara, Kanagawa, 259-1193, Japan.
| | - Takashi Nonaka
- Department of Neuropathology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Yusuke Moriya
- Department of Neurology, Tokai University School of Medicine, Isehara, Japan
| | - Natsuko Fujii
- Department of Neurology, Tokai University School of Medicine, Isehara, Japan
| | - Yoshinori Okada
- Support Center for Medical Research and Education, Tokai University, Isehara, Japan
| | - Hideo Tsukamoto
- Support Center for Medical Research and Education, Tokai University, Isehara, Japan
| | - Johbu Itoh
- Support Center for Medical Research and Education, Tokai University, Isehara, Japan
| | - Chisa Okada
- Support Center for Medical Research and Education, Tokai University, Isehara, Japan
| | - Tadayuki Satoh
- Support Center for Medical Research and Education, Tokai University, Isehara, Japan
| | - Tetsuaki Arai
- Department of Neuropsychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Masato Hasegawa
- Department of Neuropathology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Shunya Takizawa
- Department of Neurology, Tokai University School of Medicine, Isehara, Japan
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