Journal
CELL STRESS & CHAPERONES
Volume 23, Issue 6, Pages 1177-1183Publisher
SPRINGER
DOI: 10.1007/s12192-018-0930-1
Keywords
Proteostasis; Protein aggregation; HSP; FRAP; ALS
Categories
Funding
- Japan Society for Promotion of Science (JSPS) [16KK0156]
- JSPS [26440090]
- Nakabayashi Trust for ALS Research (Tokyo, Japan)
- Japan Amyotrophic Lateral Sclerosis Association (JALSA, Tokyo, Japan)
- Nakatani Foundation for Advancement of Measuring Technologies in Biomedical Engineering
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Transactive response DNA/RNA-binding protein 43-kDa (TDP-43) C-terminal fragments, such as a 25-kDa fragment (TDP-25), have been identified as a ubiquitinated and phosphorylated components of inclusion bodies (IBs) in motor neurons from amyotrophic lateral sclerosis patients. Cells contain proteins that function as molecular chaperones and prevent aggregate formation of misfolded and aggregation-prone proteins. Recently, we reported that heat shock protein (HSP)70, an abundant molecular chaperone, binds to TDP-25 in an ATP-dependent manner; however, whether HSP70 can prevent the formation of TDP-25-related IBs remains unknown. Here, we showed that HSP70 prevented TDP-25 aggregation according to green fluorescent protein-tagged TDP-25 (G-TDP-25) colocalization in the cytoplasm with mCherry-tagged HSP70 (HSP70-R). The mobile fraction of HSP70-R in the cytoplasmic IBs associated with G-TDP-25 increased relative to that of G-TDP-25, suggesting that HSP70 strongly bound to G-TDP-25 in the IBs, whereas a portion remained dissociated from the IBs. Importantly, the proportion of G-TDP-25 IBs was significantly decreased by HSP70-R overexpression; however, G-TDP-25 levels in the insoluble fraction remained unchanged by HSP70-R overexpression, suggesting that G-TDP-25 formed aggregated species that cannot be dissolved, even in the presence of strong detergents. These results indicated that HSP70 prevented the accumulation of G-TDP-25 aggregates in cytoplasmic IBs, but was insufficient for G-TDP-25 disassembly and solubilization.
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