Tar DNA binding protein of 43 kDa (TDP-43), 14-3-3 proteins and copper/zinc superoxide dismutase (SOD1) interact to modulate NFL mRNA stability. Implications for altered RNA processing in amyotrophic lateral sclerosis (ALS).
Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease characterized by progressive motor neuron degeneration in association with neurofilament (NF) aggregate formation. This process is accompanied by an alteration in the stoichiometry of NF subunit protein expression such that the steady state levels of the low molecular weight NF (NFL) mRNA levels are selectively suppressed. We have previously shown that each of TDP-43, 14-3-3 and mutant SOD1 can function as NFL mRNA 3'UTR binding proteins that directly affect the stability of NFL transcripts. In this study, we demonstrate that the interaction of TDP-43 with the NFL mRNA 3' UTR involves ribonucleotide (UG) motifs present on stem loops of the 3'UTR as well as the RRM1 and RRM2 motifs of TDP-43. Ex vivo, TDP-43, 14-3-3 and SOD1 proteins interact to modulate NFL mRNA stability, although in vivo, only TDP-43 and either mutant or wild-type SOD1 co-localize in ALS motor neurons. TDP-43 was observed to co-localize to RNA transport granules (Staufen immunoreactive) in both control and ALS spinal motor neurons. In contrast, both stress granules (TIA-1 immunoreactive) and processing bodies (P-bodies; XRN-1 immunoreactive) were more prevalent in ALS motor neurons than in controls and demonstrated strong co-localization with TDP-43. Using RNA-IP-PCR, we further demonstrate that NFL mRNA is preferentially sequestered to both stress granules and P-bodies in ALS. These data suggest that NFL mRNA processing is fundamentally altered in ALS spinal motor neurons to favour compartmentalization within both stress granules and P-bodies, and that TDP-43 plays a fundamental role in this process.
Volkening
Kathryn
K
Molecular Brain Research Group, Robarts Research Institute, 100 Perth Drive, London, Ontario, Canada N6A 5K8.
Leystra-Lantz
Cheryl
C
Yang
Wenchang
W
Jaffee
Howard
H
Strong
Michael J
MJ
D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism*; D020413:3' Untranslated Regions / Q000235:genetics; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D009046:Motor Neurons / Q000378:metabolism; D016900:Neurofilament Proteins / Q000235:genetics* / Q000378:metabolism; D020871:RNA Stability / Q000235:genetics; D034443:RNA Transport / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013116:Spinal Cord / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
D048948:14-3-3 Proteins; D020413:3' Untranslated Regions; D004268:DNA-Binding Proteins; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C044882:neurofilament protein L; D013482:Superoxide Dismutase