Increased cytoplasmic TDP-43 reduces global protein synthesis by interacting with RACK1 on polyribosomes.
TDP-43 is a well known RNA binding protein involved in the pathogenesis of Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Lobar Dementia (FTLD). In physiological conditions, TDP-43 mainly localizes in the nucleus and shuttles, at least in neurons, to the cytoplasm to form TDP-43 RNA granules. In the nucleus, TDP-43 participates to the expression and splicing of RNAs, while in the cytoplasm its functions range from transport to translation of specific mRNAs. However, if loss or gain of these TDP-43 functions are affected in ALS/FTLD pathogenesis is not clear. Here, we report that TDP-43 localizes on ribosomes not only in primary neurons but also in SH-SY5Y human neuroblastoma cells. We find that binding of TDP-43 to the translational machinery is mediated by an interaction with a specific ribosomal protein, RACK1, and that an increase in cytoplasmic TDP-43 represses global protein synthesis, an effect which is rescued by overexpression of RACK1. Ribosomal loss of RACK1, which excludes TDP-43 from the translational machinery, remarkably reduces formation of TDP-43 cytoplasmic inclusions in neuroblastoma cells. Finally, we corroborate the interaction between TDP-43 and RACK1 on polyribosomes of neuroblastoma cells with mis-localization of RACK1 on TDP-43 positive cytoplasmic inclusions in motor neurons of ALS patients. In conclusions, results from this study suggest that TDP-43 represents a translational repressor not only for specific mRNAs but for overall translation and that its binding to polyribosomes through RACK1 may promote, under conditions inducing ALS pathogenesis, the formation of cytoplasmic inclusions.
Department of Ecology and Biology, Tuscia University, Viterbo 01100, Italy.
Arianna
A
Russo
Institute of Translational Pharmacology, National Council of Research, Rome 00133, Italy.|European Brain Research Institute, Rita Levi-Montalcini Foundation, Rome 00133, Italy.
Raffaella
R
Scardigli
European Brain Research Institute, Rita Levi-Montalcini Foundation, Rome 00133, Italy.
Federico
F
La Regina
Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.
Melissa E
ME
Murray
Department of Ecology and Biology, Tuscia University, Viterbo 01100, Italy.
Nicla
N
Romano
Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA.
Dennis W
DW
Dickson
Department of Pharmacology and Experimental Therapeutics.|Department of Neurology, University School of Medicine, Boston, MA 02118, USA.
Benjamin
B
Wolozin
BioSNS Laboratory, Scuola Normale Superiore, Pisa 56126, Italy.
Antonino
A
Cattaneo
Department of Ecology and Biology, Tuscia University, Viterbo 01100, Italy.
Marcello
M
Ceci
D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000473:pathology; D002467:Cell Nucleus / Q000235:genetics; D003593:Cytoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D057180:Frontotemporal Dementia / Q000235:genetics* / Q000473:pathology; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D009046:Motor Neurons / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D009447:Neuroblastoma; D011132:Polyribosomes / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics; D012270:Ribosomes / Q000235:genetics
D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D012333:RNA, Messenger; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; C000598624:TARDBP protein, human; D019204:GTP-Binding Proteins