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Beclin1-binding UVRAG targets the class C Vps complex to coordinate autophagosome maturation and endocytic trafficking

Abstract

Autophagic and endocytic pathways are tightly regulated membrane rearrangement processes that are crucial for homeostasis, development and disease. Autophagic cargo is delivered from autophagosomes to lysosomes for degradation through a complex process that topologically resembles endosomal maturation. Here, we report that a Beclin1-binding autophagic tumour suppressor, UVRAG, interacts with the class C Vps complex, a key component of the endosomal fusion machinery. This interaction stimulates Rab7 GTPase activity and autophagosome fusion with late endosomes/lysosomes, thereby enhancing delivery and degradation of autophagic cargo. Furthermore, the UVRAG-class-C-Vps complex accelerates endosome–endosome fusion, resulting in rapid degradation of endocytic cargo. Remarkably, autophagosome/endosome maturation mediated by the UVRAG-class-C-Vps complex is genetically separable from UVRAG–Beclin1-mediated autophagosome formation. This result indicates that UVRAG functions as a multivalent trafficking effector that regulates not only two important steps of autophagy — autophagosome formation and maturation — but also endosomal fusion, which concomitantly promotes transport of autophagic and endocytic cargo to the degradative compartments.

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Figure 1: Interaction and colocalization of UVRAG with C-Vps.
Figure 2: Mapping of Vps16 binding domains of UVRAG.
Figure 3: UVRAG recruits C-Vps protein to the GFP–LC3-labelled autophagosomes.
Figure 4: Autophagosome maturation in UVRAG-expressing HeLa cells.
Figure 5: UVRAG-mediated autophagosome maturation is dependent on C-Vps, but not Beclin1.
Figure 6: Rab7 acquisition and activation by UVRAG.
Figure 7: UVRAG promotes endocytic trafficking.
Figure 8: Model of the role of UVRAG as a coordinator of the autophagosomal and endosomal machineries.

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Acknowledgements

This work was partly supported by U.S. Public Health Service grants CA82057, CA91819, CA31363, CA106156, RR00168 (J.U.J.) and AI 42999, AI069345 (V.D.). C. L. is a Leukemia & Lymphoma Society Fellow. We thank B. Levine, M.J. Hardwick, S. Virgin, S. Field, T. Yoshimori and Y. Ohsumi for providing reagents, S.W. Richardson for helping with the in vitro endosome fusion assay, S. Gygi for mass spectrometry analysis and Michelle Connole for FACS analysis. Finally, we thank all lab members for their support and discussions.

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C.L. performed all aspects of this study; L.S., K.I., M.G., Q.L. and P.F. assisted with the experimental design and in collecting the data; E.R., I.V. and V.D. assisted with the autophagic protein degradation and in vitro endosome fusion assay; C.A. provided Vps constructs and their antibodies; C.L. and J.J. organized this study and wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Jae U. Jung.

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The authors declare no competing financial interests.

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Liang, C., Lee, Js., Inn, KS. et al. Beclin1-binding UVRAG targets the class C Vps complex to coordinate autophagosome maturation and endocytic trafficking. Nat Cell Biol 10, 776–787 (2008). https://doi.org/10.1038/ncb1740

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