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ATG12-ATG3 interacts with Alix to promote basal autophagic flux and late endosome function.

ABSTRACT: The ubiquitin-like molecule ATG12 is required for the early steps of autophagy. Recently, we identified ATG3, the E2-like enzyme required for LC3 lipidation during autophagy, as an ATG12 conjugation target. Here, we demonstrate that cells lacking ATG12-ATG3 have impaired basal autophagic flux, accumulation of perinuclear late endosomes, and impaired endolysosomal trafficking. Furthermore, we identify an interaction between ATG12-ATG3 and the ESCRT-associated protein Alix (also known as PDCD6IP) and demonstrate that ATG12-ATG3 controls multiple Alix-dependent processes including late endosome distribution, exosome biogenesis and viral budding. Similar to ATG12-ATG3, Alix is functionally required for efficient basal, but not starvation-induced, autophagy. Overall, these results identify a link between the core autophagy and ESCRT machineries and uncover a role for ATG12-ATG3 in late endosome function that is distinct from the canonical role of either ATG in autophagosome formation.

SUBMITTER: Murrow L

PROVIDER: S-EPMC4344874 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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ATG12-ATG3 interacts with Alix to promote basal autophagic flux and late endosome function.

Murrow Lyndsay L Malhotra Ritu R Debnath Jayanta J

Nature cell biology 20150216 3

The ubiquitin-like molecule ATG12 is required for the early steps of autophagy. Recently, we identified ATG3, the E2-like enzyme required for LC3 lipidation during autophagy, as an ATG12 conjugation target. Here, we demonstrate that cells lacking ATG12-ATG3 have impaired basal autophagic flux, accumulation of perinuclear late endosomes, and impaired endolysosomal trafficking. Furthermore, we identify an interaction between ATG12-ATG3 and the ESCRT-associated protein Alix (also known as PDCD6IP) ...[more]

PMID: 25686249

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Project description:The interactions between viruses and cellular autophagy have been widely reported. On the one hand, autophagy is an important innate immune response against viral infection. On the other hand, some viruses exploit the autophagy pathway for their survival and proliferation in host cells. Vaccinia virus is a member of the family of Poxviridae which includes the smallpox virus. The biogenesis of vaccinia envelopes, including the core envelope of the immature virus (IV), is not fully understood. In this study we investigated the possible interaction between vaccinia virus and the autophagy membrane biogenesis machinery. Massive LC3 lipidation was observed in mouse fibroblast cells upon vaccinia virus infection. Surprisingly, the vaccinia virus induced LC3 lipidation was shown to be independent of ATG5 and ATG7, as the atg5 and atg7 null mouse embryonic fibroblasts (MEFs) exhibited the same high levels of LC3 lipidation as compared with the wild-type MEFs. Mass spectrometry and immunoblotting analyses revealed that the viral infection led to the direct conjugation of ATG3, which is the E2-like enzyme required for LC3-phosphoethanonamine conjugation, to ATG12, which is a component of the E3-like ATG12–ATG5-ATG16 complex for LC3 lipidation. Consistently, ATG3 was shown to be required for the vaccinia virus induced LC3 lipidation. Strikingly, despite the high levels of LC3 lipidation, subsequent electron microscopy showed that vaccinia virus-infected cells were devoid of autophagosomes, either in normal growth medium or upon serum and amino acid deprivation. In addition, no autophagy flux was observed in virus-infected cells. We further demonstrated that neither ATG3 nor LC3 lipidation is crucial for viral membrane biogenesis or viral proliferation and infection. Together, these results indicated that vaccinia virus does not exploit the cellular autophagic membrane biogenesis machinery for their viral membrane production. Moreover, this study demonstrated that vaccinia virus instead actively disrupts the cellular autophagy through a novel molecular mechanism that is associated with aberrant LC3 lipidation and a direct conjugation between ATG12 and ATG3.

Dataset Information

ATG12-ATG3 interacts with Alix to promote basal autophagic flux and late endosome function.

Publications

ATG12-ATG3 interacts with Alix to promote basal autophagic flux and late endosome function.

Similar Datasets

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