Integrated proteomics identifies p62-dependent selective autophagy of the supramolecular vault complex

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Autophagy selectively degrades biomolecular condensates, such as p62/SQSTM1 bodies, to prevent diseases like cancer.
• While mechanisms of p62 body degradation are studied, their molecular constituents remain largely unknown.

Purpose of the Study:

• To identify the constituents of p62 bodies and understand the mechanisms of their selective degradation.
• To establish a method for purifying phase-separation-mediated selective autophagy cargoes.

Main Methods:

• Developed a fluorescence-activated particle sorting method for p62 body purification from human cell lines.
• Utilized mass spectrometry to determine the constituents of purified p62 bodies.
• Analyzed mass spectrometry data from selective-autophagy-defective mouse tissues.

Main Results:

• Identified the vault complex, a large supramolecular assembly, as a cargo within p62 bodies.
• Demonstrated that the major vault protein interacts with NBR1 to recruit vault into p62 bodies for degradation.
• Named this degradation process 'vault-phagy', revealing its role in regulating homeostatic vault levels in vivo.

Conclusions:

• Vault-phagy is a novel selective autophagy pathway for degrading the vault complex.
• Impaired vault-phagy may be linked to non-alcoholic steatohepatitis-derived hepatocellular carcinoma.
• The study provides a method for identifying selective autophagy cargoes formed via phase separation, advancing understanding of proteostasis.