3' untranslated region in a light neurofilament (NF-L) mRNA triggers aggregation of NF-L and mutant superoxide dismutase 1 proteins in neuronal cells.
The pathogenesis of neurodegenerative diseases is believed to involve abnormal aggregation of proteins, but the mechanisms initiating protein aggregation are unclear. Here we report a novel phenomenon that could be instrumental in triggering protein aggregation in neurodegenerative diseases. We show that the 3' untranslated region (3'UTR) of a light neurofilament (NF-L) transcript enhances the reactivity of its own translated product and leads to loss of solubility and aggregation of NF-L protein and to coaggregation of mutant superoxide dismutase 1 (SOD1) protein. Full-length mouse NF-L cDNAs, with and without NF-L 3'UTR, were fused to the C terminus of a green fluorescent protein (GFP) reporter gene, and the GFP-tagged NF-L proteins were examined in transfected Neuro2a cells. The GFP-tagged NF-L protein expressed from the transgene containing NF-L 3'UTR, but not from the transgene lacking NF-L 3'UTR, colocalizes with endogenous heavy neurofilament protein and, at high-level expression, leads to loss of solubility and aggregation of GFP-tagged NF-L protein. Aggregation of GFP-tagged NF-L protein triggers coaggregation and loss of solubility of coexpressed DsRed-tagged mutant (G93A) SOD1 protein but not wild-type SOD1 protein. Deletional mutagenesis maps the RNA sequence causing aggregation of GFP-tagged NF-L protein to the proximal 45 nucleotides of NF-L 3'UTR. This is the site of a major destabilizing element in NF-L RNA and binding site for RNA-binding proteins. Our findings support a working model whereby NF-L RNA, or cognate RNA-binding factors, enhances the reactivity of NF-L protein and provides a triggering mechanism leading to aggregation of NF-L and other proteins in neurodegenerative diseases.
Lin
Hong
H
Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA.
Zhai
Jinbin
J
Cañete-Soler
Rafaela
R
Schlaepfer
William W
WW
D020413:3' Untranslated Regions / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D017930:Genes, Reporter / Q000235:genetics; D049452:Green Fluorescent Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D046911:Macromolecular Substances; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism; D019636:Neurodegenerative Diseases / Q000209:etiology / Q000378:metabolism; D016900:Neurofilament Proteins / Q000235:genetics* / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D014162:Transfection; D019076:Transgenes; D019680:Trinucleotide Repeat Expansion; D014452:Ubiquitins / Q000378:metabolism
D020413:3' Untranslated Regions; D006360:Heat-Shock Proteins; D008164:Luminescent Proteins; D046911:Macromolecular Substances; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D011944:Receptors, Androgen; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins; C044882:neurofilament protein L; C051774:neurofilament protein H; D049452:Green Fluorescent Proteins; C109415:SOD1 G93A protein; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1