Amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease) is a progressive and fatal neurodegenerative disease. A general symptom of ALS is muscle weakness and wasting triggered by denervation at neuromuscular junctions. The majority of ALS cases are sporadic, and approximately 10% are familial. Several ALS genes have been identified as their mutation can lead to familial ALS, including two genes encoding RNA processing proteins TDP-43 and fused in sarcoma/translocated in liposarcoma (FUS/TLS). FUS is a ubiquitously expressed multi-domain RNA-binding protein. In neurons and glial cells, FUS is almost exclusively localized to the nucleus but is also reported to transport mRNA for local translation in dendrites in neurons. In addition, FUS plays a role in a variety of processes including nucleocytoplasmic shuttling of mRNA, transcriptional regulation and mRNA splicing. However, little is known regarding how FUS mutations cause motor neuron degeneration and ALS, which is the focus of this study. We recently published that the C-terminus of FUS, where the ALS-causing mutations are clustered, functions as an effective nuclear localization sequence (NLS). Our newly generated data suggest that a FUS- interacting protein Gemin3 plays a critical role in the perturbations caused by FUS mutations. Gemin3 can be sequestered by ALS mutant FUS, which causes reduced Gemin3-positive nuclear structures (Gems), decreased assembly of snRNPs, and attenuated spliceosome activity. The Drosophila model we established showed motor function deficiency when FUS was over-expressed in motor neurons. Interestingly, Gemin3 was also reported to be required for larval motor function in Drosophila. Moreover, we generated FUS/Gemin3 double transgenic flies and showed that expression of Gemin3 rescued the phenotypes of FUS transgenic flies. We thus hypothesize that the ALS-related FUS mutants or WT FUS with deregulated over-expression can accumulate in cytoplasm and sequester Gemin3, which results in decreased assembly of snRNPs in cytoplasm and compromised spliceosome function in the nucleus. To test the central hypothesis, three specific aims have been designed to determine the role of FUS in ALS.
Aim 1 is to understand the regulation of FUS subcellular localization by the localization sequence elements within FUS as well as by its RNA binding ability.
In Aim 2, we will first determine the molecular mechanism how FUS and Gemin 3 interact. We will further characterize how FUS mutations disturb Gemin 3- mediated snRNP assembly and spliceosome activity.
Aim 3 will test the molecular mechanisms defined in Aims 1 and 2 using the Drosophila model. We will first determine whether motor neuron death and neuromuscular denervation are prominent in the transgenic flies with motor neuron-specific FUS expression. FUS-mediated Gemin3 sequestering and subsequent spliceosome changes will be especially tested in flies since Gemin3 over-expression rescued the motor function deficit phenotype caused by FUS. Furthermore, the significance of FUS subcellular localization and RNA binding in producing toxicity in motor neurons will be investigated. Lastly, we will carry out RNA-Seq experiment to determine the FUS-mediated splicing alterations. This project will utilize the combination of cellular and Drosophila models to investigate the FUS- mediated ALS etiology. The findings are expected to provide critical insights into the mechanisms by which FUS mutations perturb the RNA processing pathways and ultimately lead to the disease.

Public Health Relevance

Several amyotrophic lateral sclerosis (ALS) genes have been identified as their mutation can lead to familial ALS, including two genes encoding RNA processing proteins TDP-43 and fused in sarcoma (FUS). The major challenge in the field is that little is known how FUS mutations cause motor neuron degeneration in ALS. We propose to test the hypothesis that the ALS-related FUS mutants or WT FUS with deregulated over- expression can accumulate in cytoplasm and sequester Gemin3, which results in decreased assembly of snRNPs in cytoplasm and compromised spliceosome function in the nucleus. To test the central hypothesis, three specific aims have been designed to determine the role of FUS in ALS. We have produced novel preliminary data, developed unique tools, generated nearly all critical reagents, and established collaborations with leading experts. We propose to use the combination of cellular and Drosophila models to test the hypothesis. The findings are expected to provide critical insights into the mechanisms by which FUS mutations perturb the RNA processing pathways and ultimately lead to the disease. The knowledge generated in the proposed research will also provide much-needed future direction for developing ALS treatment.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS077284-04
Application #
8640219
Study Section
Neural Oxidative Metabolism and Death Study Section (NOMD)
Program Officer
Gubitz, Amelie
Project Start
2011-08-15
Project End
2015-04-30
Budget Start
2014-05-01
Budget End
2015-04-30
Support Year
4
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Kentucky
Department
Biochemistry
Type
Schools of Medicine
DUNS #
City
Lexington
State
KY
Country
United States
Zip Code
40506
Li, Jing; Song, Jun; Zaytseva, Yekaterina Y et al. (2016) An obligatory role for neurotensin in high-fat-diet-induced obesity. Nature 533:411-5
Kamelgarn, Marisa; Chen, Jing; Kuang, Lisha et al. (2016) Proteomic analysis of FUS interacting proteins provides insights into FUS function and its role in ALS. Biochim Biophys Acta 1862:2004-14
Meier, Shelby; Bell, Michelle; Lyons, Danielle N et al. (2016) Pathological Tau Promotes Neuronal Damage by Impairing Ribosomal Function and Decreasing Protein Synthesis. J Neurosci 36:1001-7
Kapeli, Katannya; Pratt, Gabriel A; Vu, Anthony Q et al. (2016) Distinct and shared functions of ALS-associated proteins TDP-43, FUS and TAF15 revealed by multisystem analyses. Nat Commun 7:12143
Gal, Jozsef; Kuang, Lisha; Barnett, Kelly R et al. (2016) ALS mutant SOD1 interacts with G3BP1 and affects stress granule dynamics. Acta Neuropathol 132:563-76
Lee, Joo-Yong; Kawaguchi, Yoshiharu; Li, Ming et al. (2015) Uncoupling of Protein Aggregation and Neurodegeneration in a Mouse Amyotrophic Lateral Sclerosis Model. Neurodegener Dis 15:339-49
Meier, Shelby; Bell, Michelle; Lyons, Danielle N et al. (2015) Identification of Novel Tau Interactions with Endoplasmic Reticulum Proteins in Alzheimer's Disease Brain. J Alzheimers Dis 48:687-702
Yang, Liuqing; Zhang, Jiayu; Kamelgarn, Marisa et al. (2015) Subcellular localization and RNAs determine FUS architecture in different cellular compartments. Hum Mol Genet 24:5174-83
Dhar, Sanjit Kumar; Zhang, Jiayu; Gal, Jozsef et al. (2014) FUsed in sarcoma is a novel regulator of manganese superoxide dismutase gene transcription. Antioxid Redox Signal 20:1550-66
Yang, Liuqing; Gal, Jozsef; Chen, Jing et al. (2014) Self-assembled FUS binds active chromatin and regulates gene transcription. Proc Natl Acad Sci U S A 111:17809-14

Showing the most recent 10 out of 16 publications