Polyglutamine-Expanded Ataxin-3 Accelerates CFTR Degradation Through K63-Linked Ubiquitination to Exacerbate...

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Ataxin-3 (ATXN3) is linked to spinocerebellar ataxia type 3 (SCA3) via polyglutamine expansion.
• The role of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel in the nervous system and its regulation by ATXN3 are not well understood.

Purpose of the Study:

• To investigate the interaction between Ataxin-3 and CFTR in human microglia.
• To elucidate the role of this interaction in neuroinflammation and SCA3 pathogenesis.

Main Methods:

• Co-immunoprecipitation (Co-IP) to detect protein interactions.
• Western blotting to analyze protein levels and ubiquitination.
• Small interfering RNA (siRNA) to modulate gene expression.
• Cell culture and stimulation with lipopolysaccharide (LPS).

Main Results:

• Ataxin-3 interacts with and promotes the degradation of CFTR in microglia via K63-linked polyubiquitination, reducing CFTR half-life.
• Pathogenic Ataxin-3Q80 mutant shows enhanced degradation of CFTR compared to wild-type.
• This Ataxin-3-CFTR interaction drives microglial polarization towards a pro-inflammatory phenotype, exacerbating neuroinflammation.
• A feedback mechanism was observed where K63-linked polyubiquitin chains also promote Ataxin-3 degradation.

Conclusions:

• A novel Ataxin-3-K63 ubiquitin chain-CFTR pathway regulates microglial activation.
• This pathway contributes to neuroinflammation in SCA3.
• Targeting this pathway may offer new therapeutic strategies for SCA3.