The IAP family member BRUCE regulates autophagosome-lysosome fusion

Nat Commun. 2018 Feb 9;9(1):599. doi: 10.1038/s41467-018-02823-x.


Autophagy has an important role in cellular homeostasis by degrading and recycling cytotoxic components. Ubiquitination is known to target cargoes for autophagy; however, key components of this pathway remain elusive. Here we performed an RNAi screen to uncover ubiquitin modifiers that are required for starvation-induced macroautophagy in mammalian cells. Our screen uncovered BRUCE/Apollon/Birc6, an IAP protein, as a new autophagy regulator. Depletion of BRUCE leads to defective fusion of autophagosomes and lysosomes. Mechanistically, BRUCE selectively interacts with two ATG8 members GABARAP and GABARAPL1, as well as with Syntaxin 17, which are all critical regulators of autophagosome-lysosome fusion. In addition, BRUCE colocalizes with LAMP2. Interestingly, a non-catalytic N-terminal BRUCE fragment that is sufficient to bind GABARAP/GABARAPL1 and Syntaxin 17, and to colocalize with LAMP2, rescues autolysosome formation in Bruce -/- cells. Thus, BRUCE promotes autolysosome formation independently of its ubiquitin-conjugating activity and is a regulator of both macroautophagy and apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Apoptosis / genetics
  • Apoptosis Regulatory Proteins
  • Autophagosomes / metabolism*
  • Autophagy / genetics
  • CRISPR-Cas Systems
  • Cell Line
  • Cells, Cultured
  • HEK293 Cells
  • Humans
  • Inhibitor of Apoptosis Proteins / genetics
  • Inhibitor of Apoptosis Proteins / metabolism*
  • Lysosomes / genetics
  • Lysosomes / metabolism*
  • Membrane Fusion*
  • Mice, Knockout
  • Microscopy, Fluorescence
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Protein Binding
  • RNA Interference


  • Adaptor Proteins, Signal Transducing
  • Apoptosis Regulatory Proteins
  • GABARAP protein, human
  • GABARAPL1 protein, human
  • Inhibitor of Apoptosis Proteins
  • Microtubule-Associated Proteins