Abstract
A hexanucleotide repeat expansion in the C9orf72 gene is the most common cause of inherited amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Unconventional translation of the C9orf72 repeat produces dipeptide repeat proteins (DPRs). Previously, we showed that the DPRs PR50 and GR50 are highly toxic when expressed in Caenorhabditis elegans, and this toxicity depends on nuclear localization of the DPR. In an unbiased genome-wide RNA interference (RNAi) screen for suppressors of PR50 toxicity, we identified 12 genes that consistently suppressed either the developmental arrest and/or paralysis phenotype evoked by PR50 expression. All of these genes have vertebrate homologs, and 7 of 12 contain predicted nuclear localization signals. One of these genes was spop-1, the C. elegans homolog of SPOP, a nuclear localized E3 ubiquitin ligase adaptor only found in metazoans. SPOP is also required for GR50 toxicity and functions in a genetic pathway that includes cul-3, which is the canonical E3 ligase partner for SPOP. Genetic or pharmacological inhibition of SPOP in mammalian primary spinal cord motor neurons suppressed DPR toxicity without affecting DPR expression levels. Finally, we find that knockdown of bromodomain proteins in both C. elegans and mammalian neurons, which are known SPOP ubiquitination targets, suppresses the protective effect of SPOP inhibition. Together, these data suggest a model in which SPOP promotes the DPR-dependent ubiquitination and degradation of BRD proteins. We speculate the pharmacological manipulation of this pathway, which is currently underway for multiple cancer subtypes, could also represent an entry point for therapeutic intervention to treat C9orf72 FTD/ALS.
| Original language | English (US) |
|---|---|
| Article number | e2104664118 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 118 |
| Issue number | 40 |
| DOIs | |
| State | Published - Oct 5 2021 |
Funding
This work was supported by grants from the NIH (NS094921 and NS096319 to T.L., NS05225 and NS087077 to R.G.K). Research in the R.G.K. laboratory is supported by the Heather Koster Family Charitable Fund and the Les Turner ALS Center. We thank the laboratory of Dr. Caiguang Yang (Shaghai Institute of Materia Medica, Chinese Academy of Sciences) for generously providing Compound 6b. We thank Ed Kipreos (University of Georgia) for providing the cul-3(RNAi) clone. Some strains were provided by the Caenorhabditis elegans Stock Center (CGC), which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440). ACKNOWLEDGMENTS. This work was supported by grants from the NIH (NS094921 and NS096319 to T.L., NS05225 and NS087077 to R.G.K). Research in the R.G.K. laboratory is supported by the Heather Koster Family Charitable Fund and the Les Turner ALS Center. We thank the laboratory of Dr. Caiguang Yang (Shaghai Institute of Materia Medica, Chinese Academy of Sciences) for generously providing Compound 6b. We thank Ed Kipreos (University of Georgia) for providing the cul-3(RNAi) clone. Some strains were provided by the Caenorhabditis elegans Stock Center (CGC), which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).
Keywords
- Bromodomain proteins
- C. elegans
- Genetic screen
- Neurodegeneration
- Proteasome
ASJC Scopus subject areas
- General
