TDP-43 and FUS RNA-binding Proteins Bind Distinct Sets of Cytoplasmic Messenger RNAs and Differently Regulate Their Post-transcriptional Fate in Motoneuron-like Cells

Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Milan 20149, Italy.
Journal of Biological Chemistry (Impact Factor: 4.57). 03/2012; 287(19):15635-47. DOI: 10.1074/jbc.M111.333450
Source: PubMed

ABSTRACT The RNA-binding proteins TDP-43 and FUS form abnormal cytoplasmic aggregates in affected tissues of patients with amyotrophic lateral sclerosis and frontotemporal lobar dementia. TDP-43 and FUS localize mainly in the nucleus where they regulate pre-mRNA splicing, but they are also involved in mRNA transport, stability, and translation. To better investigate their cytoplasmic activities, we applied an RNA immunoprecipitation and chip analysis to define the mRNAs associated to TDP-43 and FUS in the cytoplasmic ribonucleoprotein complexes from motoneuronal NSC-34 cells. We found that they bind different sets of mRNAs although converging on common cellular pathways. Bioinformatics analyses identified the (UG)(n) consensus motif in 80% of 3'-UTR sequences of TDP-43 targets, whereas for FUS the binding motif was less evident. By in vitro assays we validated binding to selected target 3'-UTRs, including Vegfa and Grn for TDP-43, and Vps54, Nvl, and Taf15 for FUS. We showed that TDP-43 has a destabilizing activity on Vegfa and Grn mRNAs and may ultimately affect progranulin protein content, whereas FUS does not affect mRNA stability/translation of its targets. We also demonstrated that three different point mutations in TDP-43 did not change the binding affinity for Vegfa and Grn mRNAs or their protein level. Our data indicate that TDP-43 and FUS recognize distinct sets of mRNAs and differently regulate their fate in the cytoplasm of motoneuron-like cells, therefore suggesting complementary roles in neuronal RNA metabolism and neurodegeneration.

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Available from: Emanuele Buratti, Aug 15, 2015
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    • "Inthispicture(Figure6)FUSandTDP-43RNAbindingpro- teinsareatthecoreofthenetwork,sincetheyoftenareassociated factorsthatsharesimilarfeatures,withsometimesdifferentbut complementaryroles(Colombritaetal.,2012).Theyinteractwith RNAinthreemainroles:asRNAbindingproteinsparticipating onthedifferentaspectsofmRNAprocessing(Boscoetal.,2010; Colombritaetal.,2011),asregulatorsofmicroRNAsprocessing, "
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    ABSTRACT: Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by degeneration of the fronto temporal lobes and abnormal protein inclusions. It exhibits a broad clinicopathological spectrum and has been linked to mutations in seven different genes. We will provide a picture, which connects the products of these genes, albeit diverse in nature and function, in a network. Despite the paucity of information available for some of these genes, we believe that RNA processing and post-transcriptional regulation of gene expression might constitute a common theme in the network. Recent studies have unraveled the role of mutations affecting the functions of RNA binding proteins and regulation of microRNAs. This review will combine all the recent findings on genes involved in the pathogenesis of FTD, highlighting the importance of a common network of interactions in order to study and decipher the heterogeneous clinical manifestations associated with FTD. This approach could be helpful for the research of potential therapeutic strategies.
    Frontiers in Molecular Neuroscience 03/2015; 8:9. DOI:10.3389/fnmol.2015.00009 · 4.08 Impact Factor
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    • "Alternatively, or in addition, RNA-binding activity might enable TDP-43 and FUS to sequester essential RNAs and other RNA-binding proteins in inclusions. Because TDP-43 and FUS regulate the splicing of myriad mRNAs with large introns that are critical for neuronal viability (Polymenidou et al., 2011; Colombrita et al., 2012; Lagier-Tourenne et al., 2012), it seems probable that sequestration of these mRNAs might be particularly damaging for specific neurons. Thus, strategies to release these RNAs from aggregated FUS or TDP-43 traps could have therapeutic utility. "
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    The Journal of Cell Biology 04/2013; 201(3):361-72. DOI:10.1083/jcb.201302044 · 9.69 Impact Factor
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    • "Apart from Nd1-L, many other mRNAs might possibly be transported in association with FUS into dendrites in neuronal cells. RNA immunoprecipitation (RIP) followed by microarray analysis identified several hundred cytosolic mRNA targets of FUS in the motoneuron-like cell line NSC-34 (Colombrita et al., 2012). Whether FUS is involved in dendritic transport of these mRNAs or in regulating their local translation remains to be seen. "
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    ABSTRACT: Fused in sarcoma (FUS) is a nuclear DNA/RNA binding protein that regulates different steps of gene expression, including transcription, splicing and mRNA transport. FUS has been implicated in neurodegeneration, since mutations in FUS cause familial amyotrophic lateral sclerosis (ALS-FUS) and lead to the cytosolic deposition of FUS in the brain and spinal cord of ALS-FUS patients. Moreover, FUS and two related proteins of the same protein family (FET family) are co-deposited in cytoplasmic inclusions in a subset of patients with frontotemporal lobar degeneration (FTLD-FUS). Cytosolic deposition of these otherwise nuclear proteins most likely causes the loss of a yet unknown essential nuclear function and/or the gain of a toxic function in the cytosol. Here we summarize what is known about the physiological functions of the FET proteins in the nucleus and cytoplasm and review the distinctive pathomechanisms that lead to the deposition of only FUS in ALS-FUS, but all three FET proteins in FTLD-FUS. We suggest that ALS-FUS is caused by a selective dysfunction of FUS, while FTLD-FUS may be caused by a dysfunction of the entire FET family.
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