TRIM32-UBQLN2-p62 axis promotes TDP-43 inclusion formation and amyloid aggregation through shuttle condensates

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Aberrant protein aggregation is central to neurodegenerative diseases like ALS, FTLD, AD, and LATE.
• A shared molecular pathway driving pathological protein aggregation across these diseases remains elusive.

Purpose of the Study:

• To investigate the role of the E3 ubiquitin ligase TRIM32 in protein aggregation pathways relevant to neurodegenerative diseases.
• To elucidate the molecular mechanisms underlying TRIM32-mediated protein condensate formation and client protein capture.

Main Methods:

• Biochemical assays to study condensate formation involving TRIM32, UBQLN2, and p62/SQSTM1.
• Analysis of TRIM32's substrate-binding domain and its interaction with client proteins like TDP-43 and ANXA11.
• Investigation of TRIM32 condensate effects on TDP-43 amyloid aggregation in vitro.
• Immunohistochemical analysis of TRIM32 and pTDP-43 co-localization in human neurodegenerative disease brain tissues.

Main Results:

• TRIM32, UBQLN2, and p62/SQSTM1 form E3 ligase activity-dependent condensates.
• These condensates selectively capture UBQLN2 client proteins, including TDP-43 and ANXA11, modulating their mobility.
• TRIM32 condensates promote TDP-43 amyloid aggregation, an effect enhanced by pathogenic UBQLN2 mutations.
• TRIM32 co-localizes with pathological pTDP-43 inclusions in diverse neurodegenerative disease brains.

Conclusions:

• TRIM32-driven condensates act as selective proteostasis sorting compartments.
• These findings propose a broad role for TRIM32 in TDP-43 proteinopathies across various neurodegenerative diseases.