Transportin1: a marker of FTLD-FUS

Abstract

The term frontotemporal lobar degeneration (FTLD) describes a group of disorders that are subdivided by the presence of one of a number of pathological proteins identified in the inclusion bodies observed post-mortem. The FUS variant is defined by the presence of the fused in sarcoma protein (FUS) in the pathological inclusions. However, similar to other FTLDs, the disease pathogenesis of FTLD-FUS remains largely poorly understood. Here we present data that the protein transportin1 (TRN1) is abundant in the FUS-positive inclusions. TRN1, the protein product of the TNP01 gene, is responsible for shuttling proteins containing an M9 nuclear localisation signal between the nuclear and cytoplasmic compartments. RNA interacting proteins, including FUS, have been implicated as targets of TRN1. Using TRN1 immunohistochemistry and Western blotting in this study, we investigated 13 cases of FTLD-FUS including 6 cases with neuronal intermediate filament inclusion disease (NIFID) and 7 atypical frontotemporal lobar degeneration with ubiquitinated inclusion (aFTLD-U) cases. The data from our immunohistochemical studies show that FUS-immunoreactive inclusions are also strongly labelled with the anti-TRN1 antibody and double-label immunofluorescence studies indicate good co-localisation between the FUS and TRN1 pathologies. Our biochemical investigations demonstrate that urea-soluble TRN1 is present in aFTLD-U and NIFID, but not in normal control brains. These findings implicate abnormalities of FUS transport in the pathogenesis of FTLD-FUS.

Proteomic analyses reveal that loss of TDP-43 affects RNA processing and intracellular transport

“…Nuclear import factors transportin 1 and 2 are responsible for import of fused in sarcoma (FUS), another ALS-and FTLDinvolved RNA-binding protein, into the nucleus (Dormann et al, 2010). Transportin 1 colocalizes with FUS aggregates in FTLD with FUS inclusions (FTLD-FUS) (Brelstaff et al, 2011) and ALS with FUS inclusions without FUS mutations (Takeuchi et al, 2013) but not in ALS with FUS mutations (Neumann et al, 2012;Troakes et al, 2013). It does not colocalize with TDP-43 inclusions in FTLD or ALS (Brelstaff et al, 2011;Neumann et al, 2012) but there is variability in nuclear and cytoplasmic staining in ALS with TDP-43 pathology (Troakes et al, 2013).…”

“…Transportin 1 colocalizes with FUS aggregates in FTLD with FUS inclusions (FTLD-FUS) (Brelstaff et al, 2011) and ALS with FUS inclusions without FUS mutations (Takeuchi et al, 2013) but not in ALS with FUS mutations (Neumann et al, 2012;Troakes et al, 2013). It does not colocalize with TDP-43 inclusions in FTLD or ALS (Brelstaff et al, 2011;Neumann et al, 2012) but there is variability in nuclear and cytoplasmic staining in ALS with TDP-43 pathology (Troakes et al, 2013). Changes of other karyopherins in ALS and FTLD tissue have also been reported, and furthermore, impairment of the classical import pathway leads to accumulation of TDP-43 in the cytoplasm (Winton et al, 2008;Nishimura et al, 2010), suggesting a feed-forward loop.…”

Pathogenesis of FUS-associated ALS and FTD: insights from rodent models

“…However as an RNA-binding protein, it possesses the ability to move between both through its role in nucleocytoplasmic transport [13]. The characteristic presence of FUS-immunoreactive inclusions in the cytoplasm of ALS- FUS and FTLD-FUS has led to the suggestion that mislocalization of FUS to the cytoplasm contributes to neurodegeneration in these cases, by a gain-of-toxicity mechanism.…”

“…At least 20 sites within the FUS protein, mainly located in the RGG3 domain, are arginine methylated [63], mediated primarily by protein N -arginine methyltransferase 1 (PRMT1) [24], inhibition of which limits the capacity of mutant FUS to localize to the cytoplasm to form inclusions [82]. The nuclear import karyopherin protein Transportin-1 strongly co-localizes with FUS in FTLD-FUS [13], however in FTLD-FUS all FET proteins co-localize with Transportin-1, whereas ALS- FUS inclusions contain exclusively FUS. In 2012, Dormann et al [23] showed that arginine methylation impairs Transportin-1 dependent nuclear import of FUS by preventing Transportin-1 binding upstream of the NLS.…”

Sequential Extraction of Soluble and Insoluble Alpha-Synuclein from Parkinsonian Brains

“…Here, a biochemical extraction protocol (see scheme presented in Figure 1) for increasingly insoluble α-syn deposits from human post-mortem PD brain tissue that harbour α-syn aggregates to varying degrees has been described. This technique can also be adapted with modifications in buffer compositions to study aggregate proteins from other neurodegenerative diseases 23,24 and also from transgenic animal brain tissue Note: Blots can also be developed manually using developer and fixer from a commercial source in case an automated developer machine is not available.…”