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Investigations of S100 proteins and their role in huntingtin aggregation
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Orientador(es)
Resumo(s)
Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by an autosomal
dominant inheritance, leading to a triad of motor, cognitive, and behavioural symptoms. HD is an
incurable disease caused by a CAG trinucleotide repeat expansion in the HTT gene, which translates
into an expanded polyglutamine tract (polyQ) in the huntingtin (Htt) protein, leading to the formation
of mutant huntingtin (mHtt). The expanded polyQ tract destabilizes the conformation of huntingtin, and
promotes the assembly of amyloidogenic protein aggregates, primarily composed of N-terminal Htt
fragments. This accumulation disrupts various essential brain functions, ultimately leading to neuronal
degeneration. S100B is a calcium-binding alarmin that is predominantly synthesized by astrocytes in
the nervous system. Depending on the concentration, S100B operates as an aggravating proinflammatory cytokine or as a protective anti-aggregation chaperone, inhibiting amyloid aggregation
and mitigating toxicity in the presence of Ca2+
. Considering S100B's significance in other
neurodegenerative conditions and its chaperone role, this work aims to explore its potential involvement
in huntingtin aggregation and in HD pathology. To address this, both cellular assays and in vitro assays
were performed. First, interactions between S100B and huntingtin were investigated using a dual
luminescence-based co-immunoprecipitation assay (LuTHy), for detection of protein-protein
interactions in mammalian cells. Secondly, the effects of endogenous and exogenous S100B on live
cells expressing wild-type and mutant huntingtin were studied through bimolecular fluorescence
complementation (BiFC) assays, to evaluate potential changes in the amounts and dynamics of Htt
inclusions. Furthermore, in vitro assays explored how the S100B protein influences Htt aggregation,
employing a FRET-based Htt aggregate seeding (FRASE) approach, which revealed that S100B
significantly delays and inhibits Htt aggregation, while operating at suprastoichiometric concentrations.
With this work, it is expected to unravel the relationship between HD and the S100B protein, which
might constitute a foundation for the development of novel therapeutic approaches.
Descrição
Tese de mestrado, Bioquímica e Biomedicina , 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Doença de Huntington huntingtina agregação proteica S100B Teses de mestrado - 2023