The truncated C-terminal RNA recognition motif of TDP-43 protein plays a key role in forming proteinaceous aggregates.
TDP-43 is the major pathological protein identified in the cellular inclusions in amyotrophic lateral sclerosis and frontotemporal lobar degeneration. The pathogenic forms of TDP-43 are processed C-terminal fragments containing a truncated RNA-recognition motif (RRM2) and a glycine-rich region. Although extensive studies have focused on this protein, it remains unclear how the dimeric full-length TDP-43 is folded and assembled and how the processed C-terminal fragments are misfolded and aggregated. Here, using size-exclusion chromatography, pulldown assays, and small angle x-ray scattering, we show that the C-terminal-deleted TDP-43 without the glycine-rich tail is sufficient to form a head-to-head homodimer primarily via its N-terminal domain. The truncated RRM2, as well as two β-strands within the RRM2, form fibrils in vitro with a similar amyloid-negative staining property to those of TDP-43 pathogenic fibrils in diseases. In addition to the glycine-rich region, the truncated RRM2, but not the intact RRM2, plays a key role in forming cytoplasmic inclusions in neuronal cells. Our data thus suggest that the process that disrupts the dimeric structure, such as the proteolytic cleavage of TDP-43 within the RRM2 that removes the N-terminal dimerization domain, may produce unassembled truncated RRM2 fragments with abnormally exposed β-strands, which can oligomerize into high-order inclusions.
Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan.
Yi-Ting
YT
Wang
Pan-Hsien
PH
Kuo
Chien-Hao
CH
Chiang
Jhe-Ruei
JR
Liang
Yun-Ru
YR
Chen
Shuying
S
Wang
James C K
JC
Shen
Hanna S
HS
Yuan
D020816:Amino Acid Motifs; D058227:Amyloidogenic Proteins / Q000378:metabolism; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism; D052160:Benzothiazoles; D002845:Chromatography / Q000379:methods; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D019281:Dimerization; D057174:Frontotemporal Lobar Degeneration / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D005998:Glycine / Q000737:chemistry; D006801:Humans; D019636:Neurodegenerative Diseases / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D013844:Thiazoles / Q000737:chemistry; D014965:X-Rays
D058227:Amyloidogenic Proteins; D052160:Benzothiazoles; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D010455:Peptides; D013844:Thiazoles; C009462:thioflavin T; D005982:Glutathione Transferase; D005998:Glycine