Nuclear carrier and RNA-binding proteins in frontotemporal lobar degeneration associated with fused in sarcoma (FUS) pathological changes.

We aimed to investigate the role of the nuclear carrier and binding proteins, transportin 1 (TRN1) and transportin 2 (TRN2), TATA-binding protein-associated factor 15 (TAF15) and Ewing's sarcoma protein (EWS) in inclusion body formation in cases of frontotemporal lobar degeneration (FTLD) associated with fused in sarcoma protein (FTLD-FUS). Eight cases of FTLD-FUS (five cases of atypical FTLD-U, two of neuronal intermediate filament inclusion body disease and one of basophilic inclusion body disease) were immunostained for FUS, TRN1, TRN2, TAF15 and EWS. Ten cases of FTLD associated with TDP-43 inclusions served as reference cases. The inclusion bodies in FTLD-FUS contained TRN1 and TAF15 and, to a lesser extent, EWS, but not TRN2. The patterns of immunostaining for TRN1 and TAF15 were very similar to that of FUS. None of these proteins was associated with tau or TDP-43 aggregations in FTLD. Data suggest that FUS, TRN1 and TAF15 may participate in a functional pathway in an interdependent way, and imply that the function of TDP-43 may not necessarily be in parallel with, or complementary to, that of FUS, despite each protein sharing many similar structural elements.

Davidson YS ，Robinson AC ，Hu Q ，Mishra M ，Baborie A ，Jaros E ，Perry RH ，Cairns NJ ，Richardson A ，Gerhard A ，Neary D ，Snowden JS ，Bigio EH ，Mann DM ... -  《-》

Transportin 1 accumulates specifically with FET proteins but no other transportin cargos in FTLD-FUS and is absent in FUS inclusions in ALS with FUS mutations.

Neumann M ，Valori CF ，Ansorge O ，Kretzschmar HA ，Munoz DG ，Kusaka H ，Yokota O ，Ishihara K ，Ang LC ，Bilbao JM ，Mackenzie IR ... -  《-》

FET proteins TAF15 and EWS are selective markers that distinguish FTLD with FUS pathology from amyotrophic lateral sclerosis with FUS mutations.

Neumann M ，Bentmann E ，Dormann D ，Jawaid A ，DeJesus-Hernandez M ，Ansorge O ，Roeber S ，Kretzschmar HA ，Munoz DG ，Kusaka H ，Yokota O ，Ang LC ，Bilbao J ，Rademakers R ，Haass C ，Mackenzie IR ... -  《-》

FUS is phosphorylated by DNA-PK and accumulates in the cytoplasm after DNA damage.

Abnormal cytoplasmic accumulation of Fused in Sarcoma (FUS) in neurons defines subtypes of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). FUS is a member of the FET protein family that includes Ewing's sarcoma (EWS) and TATA-binding protein-associated factor 2N (TAF15). FET proteins are predominantly localized to the nucleus, where they bind RNA and DNA to modulate transcription, mRNA splicing, and DNA repair. In ALS cases with FUS inclusions (ALS-FUS), mutations in the FUS gene cause disease, whereas FTLD cases with FUS inclusions (FTLD-FUS) do not harbor FUS mutations. Notably, in FTLD-FUS, all FET proteins accumulate with their nuclear import receptor Transportin 1 (TRN1), in contrast ALS-FUS inclusions are exclusively positive for FUS. In the present study, we show that induction of DNA damage replicates several pathologic hallmarks of FTLD-FUS in immortalized human cells and primary human neurons and astrocytes. Treatment with the antibiotic calicheamicin γ1, which causes DNA double-strand breaks, leads to the cytoplasmic accumulation of FUS, TAF15, EWS, and TRN1. Moreover, cytoplasmic translocation of FUS is mediated by phosphorylation of its N terminus by the DNA-dependent protein kinase. Finally, we observed elevated levels of phospho-H2AX in FTLD-FUS brains, indicating that DNA damage occurs in patients. Together, our data reveal a novel regulatory mechanism for FUS localization in cells and suggest that DNA damage may contribute to the accumulation of FET proteins observed in human FTLD-FUS cases, but not in ALS-FUS.

Deng Q ，Holler CJ ，Taylor G ，Hudson KF ，Watkins W ，Gearing M ，Ito D ，Murray ME ，Dickson DW ，Seyfried NT ，Kukar T ... -  《-》

FET proteins in frontotemporal dementia and amyotrophic lateral sclerosis.

Mutations in the fused in sarcoma gene (FUS) cause amyotrophic lateral sclerosis (ALS) with TDP-43-negative, FUS-positive pathology. FUS is also the pathological protein in most tau/TDP-43-negative subtypes of frontotemporal lobar degeneration (FTLD-FUS). FUS, together with Ewing's sarcoma protein (EWS) and TATA-binding protein associated factor 15 (TAF15), make up the FET family of DNA/RNA binding proteins that share functional homology and have the potential to interact. We recently investigated the role of the other FET proteins in the clinicopathological spectrum of FUS-opathies. In all FTLD-FUS subtypes, FUS-positive pathology was also labeled for TAF15 and EWS and cells with inclusions showed a reduction in the normal nuclear staining of all FET proteins. In contrast, in cases of ALS-FUS, TAF15 and EWS remained localized to the nucleus and did not label FUS-positive inclusions. Cell culture models replicated the human diseases. These findings indicate that ALS-FUS and FTLD-FUS have different pathomechanisms and add TAF15 and EWS to the growing list of RNA-binding proteins involved in neurodegeneration. This article is part of a Special Issue entitled: RNA-Binding Proteins.

Mackenzie IR ，Neumann M 《-》