Skip to Content
Merck
  • The stress granule protein G3BP1 alleviates spinocerebellar ataxia-associated deficits.

The stress granule protein G3BP1 alleviates spinocerebellar ataxia-associated deficits.

Brain : a journal of neurology (2022-12-14)
Rebekah Koppenol, André Conceição, Inês T Afonso, Ricardo Afonso-Reis, Rafael G Costa, Sandra Tomé, Diogo Teixeira, Joana Pinto da Silva, José Miguel Côdesso, David V C Brito, Liliana Mendonça, Adriana Marcelo, Luís Pereira de Almeida, Carlos A Matos, Clévio Nóbrega
ABSTRACT

Polyglutamine diseases are a group of neurodegenerative disorders caused by an abnormal expansion of CAG repeat tracts in the codifying regions of nine, otherwise unrelated, genes. While the protein products of these genes are suggested to play diverse cellular roles, the pathogenic mutant proteins bearing an expanded polyglutamine sequence share a tendency to self-assemble, aggregate and engage in abnormal molecular interactions. Understanding the shared paths that link polyglutamine protein expansion to the nervous system dysfunction and the degeneration that takes place in these disorders is instrumental to the identification of targets for therapeutic intervention. Among polyglutamine diseases, spinocerebellar ataxias (SCAs) share many common aspects, including the fact that they involve dysfunction of the cerebellum, resulting in ataxia. Our work aimed at exploring a putative new therapeutic target for the two forms of SCA with higher worldwide prevalence, SCA type 2 (SCA2) and type 3 (SCA3), which are caused by expanded forms of ataxin-2 (ATXN2) and ataxin-3 (ATXN3), respectively. The pathophysiology of polyglutamine diseases has been described to involve an inability to properly respond to cell stress. We evaluated the ability of GTPase-activating protein-binding protein 1 (G3BP1), an RNA-binding protein involved in RNA metabolism regulation and stress responses, to counteract SCA2 and SCA3 pathology, using both in vitro and in vivo disease models. Our results indicate that G3BP1 overexpression in cell models leads to a reduction of ATXN2 and ATXN3 aggregation, associated with a decrease in protein expression. This protective effect of G3BP1 against polyglutamine protein aggregation was reinforced by the fact that silencing G3bp1 in the mouse brain increases human expanded ATXN2 and ATXN3 aggregation. Moreover, a decrease of G3BP1 levels was detected in cells derived from patients with SCA2 and SCA3, suggesting that G3BP1 function is compromised in the context of these diseases. In lentiviral mouse models of SCA2 and SCA3, G3BP1 overexpression not only decreased protein aggregation but also contributed to the preservation of neuronal cells. Finally, in an SCA3 transgenic mouse model with a severe ataxic phenotype, G3BP1 lentiviral delivery to the cerebellum led to amelioration of several motor behavioural deficits. Overall, our results indicate that a decrease in G3BP1 levels may be a contributing factor to SCA2 and SCA3 pathophysiology, and that administration of this protein through viral vector-mediated delivery may constitute a putative approach to therapy for these diseases, and possibly other polyglutamine disorders.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-DARPP-32 Antibody, from rabbit, purified by affinity chromatography
Sigma-Aldrich
Anti-PABP 1 Antibody, clone 10E10, clone 10E10, from mouse
Sigma-Aldrich
Anti-Puromycin Antibody, clone 12D10, clone 12D10, from mouse
Sigma-Aldrich
Monoclonal Anti-β-Actin antibody produced in mouse, clone AC-74, ascites fluid
Sigma-Aldrich
Monoclonal Anti-β-Tubulin I antibody produced in mouse, clone SAP.4G5, ascites fluid
Sigma-Aldrich
Monoclonal Anti-Calbindin-D-28K antibody produced in mouse, clone CB-955, ascites fluid
Sigma-Aldrich
Anti-phospho-eIF-2α (Ser51), Upstate®, from rabbit