The anti-apoptosis ubiquitin E3 ligase XIAP promotes autophagosome-lysosome fusion during autophagy

Isabella Poetsch, Petra Ebner, Luiza Deszcz, Iris Bachtrog, Madlen Stephani, Carlos Gómez Díaz, Yasin Dagdas, Fumiyo Ikeda

Research output: Contribution to journalArticlepeer-review


The Inhibitor of Apoptosis Protein (IAP) family members are well-known endogenous regulators of apoptosis. Whether these proteins regulate other degradation pathways is unclear. Here, we discovered that the IAP member X-linked IAP (XIAP) is crucial for macroautophagy. Loss of XIAP in mouse and human cells inhibited starvation-induced degradation of LC3 proteins and an autophagy substrate p62. It also led to the accumulation of mature autophagosomes, suggesting that XIAP controls autophagic flux by mediating autolysosome formation. Xiap∆RING/∆RING cells phenocopy the autophagy defects of Xiap−/− cells, suggesting that the ubiquitinating activity mediated by the catalytic RING domain is critical for autophagic flux. We found that XIAP physically interacts with Syntaxin 17, a regulator of autophagosome-lysosome fusion. Syntaxin 17-positive mature autophagosomes positive accumulate in the cytoplasm of starved Xiap−/− cells, suggesting that XIAP might regulate its dissociation from autophagosomes after fusion. XIAP selectively interacts with GABARAP among LC3 family members via the LIR-Docking Site (LDS). Together, our data suggest that XIAP-mediated ubiquitination regulates key autophagy regulators to promote autophagosome-lysosome fusion.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - Mar 29 2018

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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