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    FUS/TLS in Stress Response - Implications for Amyotrophic Lateral Sclerosis: A Dissertation

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    Authors
    Sama, Reddy Ranjith Kumar
    Faculty Advisor
    Daryl A. Bosco, PhD
    Academic Program
    Cell Biology
    UMass Chan Affiliations
    Neurology
    Document Type
    Doctoral Dissertation
    Publication Date
    2014-03-28
    Keywords
    Dissertations, UMMS
    Amyotrophic Lateral Sclerosis
    DNA Damage
    DNA-Binding Proteins
    Mutation
    RNA-Binding Protein FUS
    p38 Mitogen-Activated Protein Kinases
    Amyotrophic Lateral Sclerosis
    DNA Damage
    DNA-Binding Proteins
    Mutation
    RNA-Binding Protein FUS
    p38 Mitogen-Activated Protein Kinases
    Biochemistry, Biophysics, and Structural Biology
    Cellular and Molecular Physiology
    Molecular Genetics
    Nervous System Diseases
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    Abstract
    Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease is a fatal neurodegenerative disease. ALS is typically adult onset and is characterized by rapidly progressive loss of both upper and lower motor neurons that leads to death usually within 3-5 years. About 90% of all the cases are sporadic with no family history while the remaining 10% are familial cases with mutations in several genes including SOD1, FUS/TLS, TDP43 and C9ORF72. FUS/TLS (Fused in Sarcoma/Translocated in Liposarcoma or FUS) is an RNA/DNA binding protein that is involved in multiple cellular functions including DNA damage repair, transcription, mRNA splicing, RNA transport and stress response. More than 40 mutations have now been identified in FUS that account for about 5% of all the familial cases of ALS. However, the exact mechanism by which FUS causes ALS is unknown. While significant progress has been made in understanding the disease mechanism and identifying therapeutic strategies, several questions still remain largely unknown. The work presented here aims at understanding the normal functions of FUS as well as the pathogenic mechanisms by which it leads to disease. Several studies showed the association of mutant-FUS with structures made up of RNA and proteins, called stress granules that form under various stress conditions. However, little is known about the role of endogenous FUS under stress conditions. I have shown that under hyperosmolar conditions, the predominantly nuclear FUS translocates into the cytoplasm and incorporates into stress granules. The response is specific to hyperosmolar stress because FUS remains nuclear under other stress conditions tested, such as oxidative stress, ER stress and heat shock. The response of FUS is rapid, and cells with reduced FUS levels are susceptible to the hyperosmolar stress, indicating a pro-survival role for FUS. In addition to investigating the functions of endogenous wild-type (WT) FUS, the work presented also focuses on identifying the pathogenic mechanism(s) of FUS variants. Using various biochemical techniques, I have shown that ALS-causing FUS variants are misfolded compared to the WT protein. Furthermore, in a squid axoplasm based vesicle motility assay, the FUS variants inhibit fast axonal transport (FAT) in a p38 MAPK dependent manner, indicating a role for the kinase in mutant-FUS mediated disease pathogenesis. Analysis of human ALS patient samples indicates higher levels of total and phospho p38, supporting the notion that aberrant regulation of p38 MAPK is involved in ALS. The results presented in this dissertation 1) support a novel prosurvival role for FUS under hyperosmolar stress conditions and, 2) demonstrate that protein misfolding and aberrant kinase activation contribute to ALS pathogenesis by FUS variants.
    DOI
    10.13028/M2QG74
    Permanent Link to this Item
    http://hdl.handle.net/20.500.14038/32062
    Rights
    Copyright is held by the author, with all rights reserved.
    ae974a485f413a2113503eed53cd6c53
    10.13028/M2QG74
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