Posttranslational Modification of Deubiquitinating Enzymes in Neurodegeneration

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DESCRIPTION (provided by applicant): Neurodegeneration is closely linked to perturbations in protein quality control (PQC). Ubiquitin pathways are central to PQC through their role in protein degradation. Here, I will investigate how deubiquitinatng enzymes (DUBs), integral components of ubiquitin pathways, are regulated by ubiquitination and how ubiquitination in turn affects their roles in PQC. These studies focus initially on a unique DUB and polyglutamine disease protein, ataxin-3 (ATS), and later will be extended to other brain-expressed DUBs. Mentored Phase (Dr. Henry Paulson; Univ. of Michigan): ATS is a deubiquitinating enzyme that functions in PQC. Mutations in ATS cause Spinocerebellar Ataxia Type S. I have collected evidence that ATS is ubiquitinated and its ubiquitinaion increases in proteotoxic stress. Importantly, ubiquitination directly enhances ATS activity. Here, I will determine where ATS is ubiquitinated, how ubiquitination activates it, and examine changes in ATS ubiquitination in neurodegeneration. As ubiquitination may regulate DUBs generally, I will also study ubiquitination of other brain-expressed DUBs (JosDI & 2, USP25, 28 & S7), strong contenders for this type of regulation. Together with training in neurodegeneration and biochemistry, student mentorship, presentation of my work at various meetings, and manuscript preparation, these studies will prepare me for an independent academic position. Independent Phase: Catalytically active ATS is neuroprotective in fly models of neurodegeneration. I will generate Drosophila lines expressing wild type or non-ubiquitinatable forms of ATS throughout the nervous system or in the eye. Through structural, behavioral and physiological studies I will examine whether ATS ubiquitination is important to its neuroprotective role in intact animals. I will also extend findings from the Mentored Phase to determine if ubiquitination of other DUBs regulates their activity and their relation to PQC. Indeed, very little is known about DUB function and regulation in neurons. Together with continued development of my knowledge and skills as an independent scientist and mentor, this research will provide strong foundations for a lab that studies a family of enzymes that is important to all ubiquitin pathways. PUBLIC HEALTH RELEVANCE: Age-dependent neurodegeneration affects millions of Americans. Here, I propose to investigate mechanisms important in protecting neurons against toxic proteinaceous agents that accumulate in the brain.