Inhibition of SQSTM1/p62 oligomerization and Keap1 sequestration by the Cullin-3 adaptor SHKBP1

Area of Science:

• Cellular Biology
• Molecular Mechanisms
• Protein Degradation Pathways

Background:

• SQSTM1/p62 is crucial for protein degradation via autophagy and ubiquitination, and for antioxidant response.
• p62 forms cytoplasmic p62 bodies, regulating its functions through assembly and sequestration of factors.
• Mechanisms governing p62 body formation and dynamics are not fully understood.

Purpose of the Study:

• To identify novel regulatory mechanisms of p62 oligomerization and p62 body formation.
• To investigate the role of SHKBP1, a Cullin-3 E3 ubiquitin ligase adaptor, in p62 regulation.
• To elucidate the impact of SHKBP1-mediated regulation on cellular antioxidant responses.

Main Methods:

• Mapping of protein-protein interactions between SHKBP1 and p62.
• Analysis of p62 body formation and dynamics in the presence of SHKBP1.
• Assessment of Keap1 sequestration and degradation under varying SHKBP1 and p62 conditions.

Main Results:

• SHKBP1 directly interacts with p62 outside of p62 bodies, independent of ubiquitination.
• This interaction inhibits p62 oligomerization and its incorporation into p62 bodies.
• SHKBP1 binding to p62 prevents Keap1 sequestration and degradation, thereby modulating the antioxidant response.

Conclusions:

• SHKBP1 employs a non-ubiquitination-dependent mechanism to regulate p62 phase separation.
• This interaction provides a novel layer of control over p62 body dynamics.
• The findings reveal a new pathway linking E3 ligase adaptors to cellular oxidative stress management.