Distinct pathways leading to TDP-43-induced cellular dysfunctions.
TAR DNA-binding protein of 43 kDa (TDP-43) is the major component protein of inclusions found in brains of patients with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP). However, the molecular mechanisms by which TDP-43 causes neuronal dysfunction and death remain unknown. Here, we report distinct cytotoxic effects of full-length TDP-43 (FL-TDP) and its C-terminal fragment (CTF) in SH-SY5Y cells. When FL-TDP was overexpressed in the cells using a lentiviral system, exogenous TDP-43, like endogenous TDP-43, was expressed mainly in nuclei of cells without any intracellular inclusions. However, these cells showed striking cell death, caspase activation and growth arrest at G2/M phase, indicating that even simple overexpression of TDP-43 induces cellular dysfunctions leading to apoptosis. On the other hand, cells expressing TDP-43 CTF showed cytoplasmic aggregates but without significant cell death, compared with cells expressing FL-TDP. Confocal microscopic analyses revealed that RNA polymerase II (RNA pol II) and several transcription factors, such as specificity protein 1 and cAMP-response-element-binding protein, were co-localized with the aggregates of TDP-43 CTF, suggesting that sequestration of these factors into TDP-43 aggregates caused transcriptional dysregulation. Indeed, accumulation of RNA pol II at TDP-43 inclusions was detected in brains of patients with FTLD-TDP. Furthermore, apoptosis was not observed in affected neurons of FTLD-TDP brains containing phosphorylated and aggregated TDP-43 pathology. Our results suggest that different pathways of TDP-43-induced cellular dysfunction may contribute to the degeneration cascades involved in the onset of ALS and FTLD-TDP.
Department of Neuropathology and Cell Biology.
Makiko
M
Yamashita
Department of Neuropathology and Cell Biology, nonaka-tk@igakuken.or.jp hasegawa-ms@igakuken.or.jp.
Takashi
T
Nonaka
Department of Brain Development and Neural Regeneration and.
Shinobu
S
Hirai
Department of Brain Development and Neural Regeneration and.
Akiko
A
Miwa
Department of Brain Development and Neural Regeneration and.
Haruo
H
Okado
Department of Neuropsychiatry, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
Tetsuaki
T
Arai
Dementia Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
Masato
M
Hosokawa
Dementia Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
Haruhiko
H
Akiyama
Department of Neuropathology and Cell Biology, nonaka-tk@igakuken.or.jp hasegawa-ms@igakuken.or.jp.
Masato
M
Hasegawa
D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D057180:Frontotemporal Dementia / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D053858:Metabolic Networks and Pathways; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D012319:RNA Polymerase II / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism
C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D010455:Peptides; D016329:Sp1 Transcription Factor; C108209:SP1 protein, human; C000598624:TARDBP protein, human; D012319:RNA Polymerase II