Friday, April 19, 2024
4/19/2024
Abstract A devastating movement disorder affecting older population is Parkinson's disease (PD), characterized by the abnormal deposition of alpha-Synuclein (a-Syn) in neuronal aggregates, and belongs to a group of neurological disorders termed a-Synucleinopathies. Other PD hallmarks are loss of dopaminergic neurons from substantia nigra and mitochondrial dysfunctions. A highly conserved and less understood family of human Tubulin Polymerization Promoting Proteins (TPPP) shows aggregation promoting properties with a-Syn and forms pathological protein deposits in a-Synucleinopathies. However, the in vivo role of mammalian TPPP is still largely uncharacterized, thus creating a clear knowledge gap in our understanding of how TPPP aggregation and neurotoxicity contributes to PD. Our recent studies were aimed at addressing this knowledge gap by developing a new Drosophila model of PD utilizing a mutation in the only Drosophila homolog of human TPPP, named Ringer, which recapitulates many of the salient features of human PD patients including progressive locomotor disabilities, loss of dopaminergic neurons and mitochondrial dysfunctions. Our studies demonstrate that TPPP/Ringer is a mitochondrial protein and loss of Ringer affects multiple components of the mitochondrial machinery, such as the fission/fusion as indicated by elevated levels of Mfn1 and Opa1, decreased levels of Drp1, and Complex I of mitochondrial respiratory chain. Furthermore, our findings showed that Ringer modulates the level of aggregated human a-Syn in adult brain neurons. While these studies capitalized on the strengths of Drosophila, the overall objective of this proposal is to extend findings from our Drosophila model to human PD patient brain tissues and healthy controls and assess the extent to which the levels and/or localization of TPPP, a-Syn and various mitochondrial proteins are altered with the goal of finding potential therapeutics that could target the affected proteins/mechanisms. The central hypothesis of the proposed studies is that human PD patient brains will display altered localization/levels of various mitochondrial proteins resembling Ringer mutants and show similar co-aggregation of TPPP/a-Syn. We will use postmortem PD patient and healthy control samples from similar brain regions of both genders to perform immunostaining/immunoblot analyses of TPPP and a-Syn to examine any alteration in their localizations/levels. We will also determine the subcellular localization/levels of various mitochondrial proteins that are part of the mitochondrial dynamics (fission/fusion machinery, such as Drp1, Mfn1/2 and Opa1), electron transport chain such as Complex I proteins and members of TOM complex in control and PD patient brains. Thus, launching from Drosophila, our studies will explore the broader mechanistic underpinnings of TPPP/a-Syn mediated neurotoxicity as well as TPPP-associated mitochondrial functions in neurodegeneration in PD and related disorders through comparative analyses. This will provide further impetus for utilizing Drosophila as an in vivo discovery platform for genetic, proteomic and pharmacological screens to uncover therapeutic targets to prevent or delay the progression of PD.
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