A fine balance between Prpf19 and Exoc7 in achieving degradation of aggregated protein and suppression of cell death in spinocerebellar ataxia type 3.

Abstract

Polyglutamine (polyQ) diseases comprise Huntington's disease and several subtypes of spinocerebellar ataxia, including spinocerebellar ataxia type 3 (SCA3). The genomic expansion of coding CAG trinucleotide sequence in disease genes leads to the production and accumulation of misfolded polyQ domain-containing disease proteins, which cause cellular dysfunction and neuronal death. As one of the principal cellular protein clearance pathways, the activity of the ubiquitin-proteasome system (UPS) is tightly regulated to ensure efficient clearance of damaged and toxic proteins. Emerging evidence demonstrates that UPS plays a crucial role in the pathogenesis of polyQ diseases. Ubiquitin (Ub) E3 ligases catalyze the transfer of a Ub tag to label proteins destined for proteasomal clearance. In this study, we identified an E3 ligase, pre-mRNA processing factor 19 (Prpf19/prp19), that modulates expanded ataxin-3 (ATXN3-polyQ), disease protein of SCA3, induced neurodegeneration in both mammalian and Drosophila disease models. We further showed that Prpf19/prp19 promotes poly-ubiquitination and degradation of mutant ATXN3-polyQ protein. Our data further demonstrated the nuclear localization of Prpf19/prp19 is essential for eliciting its modulatory function towards toxic ATXN3-polyQ protein. Intriguingly, we found that exocyst complex component 7 (Exoc7/exo70), a Prpf19/prp19 interacting partner, modulates expanded ATXN3-polyQ protein levels and toxicity in an opposite manner to Prpf19/prp19. Our data suggest that Exoc7/exo70 exerts its ATXN3-polyQ-modifying effect through regulating the E3 ligase function of Prpf19/prp19. In summary, this study allows us to better define the mechanistic role of Exoc7/exo70-regulated Prpf19/prp19-associated protein ubiquitination pathway in SCA3 pathogenesis.

• Authors: Zhefan Stephen Chen, Xiaoying Huang, Kevin Talbot, Ho Yin Edwin Chan
• Journal: Cell death & disease (Cell Death Dis) Vol. 12 Issue 2 Pg. 136 (02 02 2021) ISSN: 2041-4889 [Electronic] England
• PMID: 33542212 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Drosophila Proteins
• EXOC7 protein, human
• Nuclear Proteins
• Peptides
• Protein Aggregates
• RNA Splicing Factors
• Repressor Proteins
• Vesicular Transport Proteins
• polyglutamine
• ATXN3 protein, human
• Ataxin-3
• Proteasome Endopeptidase Complex
• DNA Repair Enzymes
• PRPF19 protein, human
• Prp19 protein, Drosophila

Topics

• Animals
• Animals, Genetically Modified
• Ataxin-3 (genetics, metabolism)
• Cell Death
• Cell Line, Tumor
• DNA Repair Enzymes (genetics, metabolism)
• Disease Models, Animal
• Drosophila Proteins (genetics, metabolism)
• Drosophila melanogaster (enzymology, genetics)
• HEK293 Cells
• Humans
• Machado-Joseph Disease (enzymology, genetics, pathology)
• Neurons (enzymology, pathology)
• Nuclear Proteins (genetics, metabolism)
• Peptides (metabolism)
• Proteasome Endopeptidase Complex (genetics, metabolism)
• Protein Aggregates
• Protein Aggregation, Pathological
• Proteolysis
• RNA Splicing Factors (genetics, metabolism)
• Repressor Proteins (genetics, metabolism)
• Vesicular Transport Proteins (genetics, metabolism)