Research & Scholarship
Profilin 1 Associates with Stress Granules and ALS-Linked Mutations Alter Stress Granule Dynamics
JOURNAL OF NEUROSCIENCE
2014; 34 (24): 8083-8097
Mutations in the PFN1 gene encoding profilin 1 are a rare cause of familial amyotrophic lateral sclerosis (ALS). Profilin 1 is a well studied actin-binding protein but how PFN1 mutations cause ALS is unknown. The budding yeast, Saccharomyces cerevisiae, has one PFN1 ortholog. We expressed the ALS-linked profilin 1 mutant proteins in yeast, demonstrating a loss of protein stability and failure to restore growth to profilin mutant cells, without exhibiting gain-of-function toxicity. This model provides for simple and rapid screening of novel ALS-linked PFN1 variants. To gain insight into potential novel roles for profilin 1, we performed an unbiased, genome-wide synthetic lethal screen with yeast cells lacking profilin (pfy1Δ). Unexpectedly, deletion of several stress granule and processing body genes, including pbp1Δ, were found to be synthetic lethal with pfy1Δ. Mutations in ATXN2, the human ortholog of PBP1, are a known ALS genetic risk factor and ataxin 2 is a stress granule component in mammalian cells. Given this genetic interaction and recent evidence linking stress granule dynamics to ALS pathogenesis, we hypothesized that profilin 1 might also associate with stress granules. Here we report that profilin 1 and related protein profilin 2 are novel stress granule-associated proteins in mouse primary cortical neurons and in human cell lines and that ALS-linked mutations in profilin 1 alter stress granule dynamics, providing further evidence for the potential role of stress granules in ALS pathogenesis.
View details for DOI 10.1523/JNEUROSCI.0543-14.2014
View details for Web of Science ID 000338338700004
Evaluating noncoding nucleotide repeat expansions in amyotrophic lateral sclerosis.
Neurobiology of aging
2014; 35 (4): 936 e1-4
Intermediate-length polyglutamine expansions in ataxin 2 are a risk factor for amyotrophic lateral sclerosis (ALS). The polyglutamine tract is encoded by a trinucleotide repeat in a coding region of the ataxin 2 gene (ATXN2). Noncoding nucleotide repeat expansions in several genes are also associated with neurodegenerative and neuromuscular diseases. For example, hexanucleotide repeat expansions located in a noncoding region of C9ORF72 are the most common cause of ALS. We sought to assess a potential larger role of noncoding nucleotide repeat expansions in ALS. We analyzed the nucleotide repeat lengths of 6 genes (ATXN8, ATXN10, PPP2R2B, NOP56, DMPK, and JPH3) that have previously been associated with neurologic or neuromuscular disorders, in several hundred sporadic patients with ALS and healthy control subjects. We report no association between ALS and repeat length in any of these genes, suggesting that variation in the noncoding repetitive regions in these genes does not contribute to ALS.
View details for DOI 10.1016/j.neurobiolaging.2013.09.024
View details for PubMedID 24269018
Yeast genetic screen reveals novel therapeutic strategy for ALS.
Rare diseases (Austin, Tex.)
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease caused by a selective loss of motor neurons. There is no cure and few effective treatments. The RNA-binding protein TDP-43 contributes to the pathogenesis of ALS. TDP-43 is depleted from the nucleus and accumulates in cytoplasmic aggregates in the degenerating neurons and glia of most ALS patients. Furthermore, mutations in the TDP-43 gene cause rare familial and sporadic forms of the disease. Thus, therapeutic strategies targeting TDP-43 may be efficacious. We have used the yeast model system to identify the mechanisms by which TDP-43 aggregation contributes to ALS and to identify approaches to protect cells from the toxic effects of TDP-43 aggregation. Using an unbiased yeast genetic screen we discovered Dbr1 as a potent suppressor of TDP-43 toxicity. Yeast cells in which Dbr1 is deleted are resistant to TDP-43 toxicity. Dbr1 inhibition in mammalian cells is also sufficient to protect against TDP-43 cytotoxicity. Here, we review this recent discovery, highlighting future approaches aimed at extending these studies and pursuing Dbr1 as a novel therapeutic target for ALS.
View details for DOI 10.4161/rdis.24420
View details for PubMedID 25002991
Inhibition of RNA lariat debranching enzyme suppresses TDP-43 toxicity in ALS disease models
2012; 44 (12): 1302-1309
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease primarily affecting motor neurons. Mutations in the gene encoding TDP-43 cause some forms of the disease, and cytoplasmic TDP-43 aggregates accumulate in degenerating neurons of most individuals with ALS. Thus, strategies aimed at targeting the toxicity of cytoplasmic TDP-43 aggregates may be effective. Here, we report results from two genome-wide loss-of-function TDP-43 toxicity suppressor screens in yeast. The strongest suppressor of TDP-43 toxicity was deletion of DBR1, which encodes an RNA lariat debranching enzyme. We show that, in the absence of Dbr1 enzymatic activity, intronic lariats accumulate in the cytoplasm and likely act as decoys to sequester TDP-43, preventing it from interfering with essential cellular RNAs and RNA-binding proteins. Knockdown of Dbr1 in a human neuronal cell line or in primary rat neurons is also sufficient to rescue TDP-43 toxicity. Our findings provide insight into TDP-43-mediated cytotoxicity and suggest that decreasing Dbr1 activity could be a potential therapeutic approach for ALS.
View details for DOI 10.1038/ng.2434
View details for Web of Science ID 000311713200006
View details for PubMedID 23104007