Distinct pathways leading to TDP-43-induced cellular dysfunctions

• Published in: Human molecular genetics 2014-08, Vol.23 (16), p.4345-4356
• Main Authors: Yamashita, Makiko, Nonaka, Takashi, Hirai, Shinobu, Miwa, Akiko, Okado, Haruo, Arai, Tetsuaki, Hosokawa, Masato, Akiyama, Haruhiko, Hasegawa, Masato
• Format: Article
• Language: English
• Subjects: Amyotrophic Lateral Sclerosis - metabolism; Apoptosis - drug effects; Cell Line, Tumor; Cyclic AMP Response Element-Binding Protein - metabolism; DNA-Binding Proteins - pharmacology; Frontotemporal Dementia - metabolism; G2 Phase Cell Cycle Checkpoints - drug effects; Gene Expression Regulation - drug effects; Humans; Metabolic Networks and Pathways; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Peptides - pharmacology; RNA Polymerase II - metabolism; Sp1 Transcription Factor - metabolism
• ISSN: 0964-6906; 1460-2083
• DOI: 10.1093/hmg/ddu152

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.