The caspase-6-p62 axis modulates p62 droplets based autophagy in a dominant-negative manner

Area of Science:

• Cell Biology
• Molecular Biology
• Autophagy Research

Background:

• SQSTM1/p62 is a key autophagy receptor involved in cargo recognition and autophagosome formation.
• p62 forms liquid droplets that serve as platforms for autophagosome assembly.
• Regulation of p62 droplet formation under stress is not well understood.

Purpose of the Study:

• To investigate the regulation of p62 droplet formation under inflammatory conditions.
• To identify the molecular mechanisms by which inflammatory toxicity affects p62 droplet formation.
• To explore the functional consequences of p62 cleavage on autophagy.

Main Methods:

• Utilized cellular models to study p62 cleavage and droplet formation.
• Identified a novel caspase-6 cleavage site (D256) in p62.
• Performed in vitro phase separation assays to confirm the role of p62 cleavage products.
• Assessed the impact of p62 cleavage on autophagosome formation.

Main Results:

• Inflammatory toxicity selectively blocks p62 droplet formation.
• Caspase-6 cleaves p62 at a conserved D256 site.
• The N-terminal p62 cleavage product (p62-N) acts in a dominant-negative manner to inhibit p62 droplet formation.
• Caspase-6-mediated p62 cleavage impairs autophagosome formation dependent on p62 droplets.

Conclusions:

• Discovered a novel mechanism where caspase-6 cleavage of p62 inhibits its droplet formation.
• p62-N acts as a dominant-negative regulator, blocking p62 liquid assembly.
• This highlights a new pathway, the caspase-6-p62 axis, for modulating autophagy under stress.