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Mol Biol Cell. 2014 Apr;25(8):1327-37. doi: 10.1091/mbc.E13-08-0447. Epub 2014 Feb 19.

The HOPS complex mediates autophagosome-lysosome fusion through interaction with syntaxin 17.

Author information

1
Department of Biochemistry and Molecular Biology, Graduate School, and Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Research Center for Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064, Japan.

Abstract

Membrane fusion is generally controlled by Rabs, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), and tethering complexes. Syntaxin 17 (STX17) was recently identified as the autophagosomal SNARE required for autophagosome-lysosome fusion in mammals and Drosophila. In this study, to better understand the mechanism of autophagosome-lysosome fusion, we searched for STX17-interacting proteins. Immunoprecipitation and mass spectrometry analysis identified vacuolar protein sorting 33A (VPS33A) and VPS16, which are components of the homotypic fusion and protein sorting (HOPS)-tethering complex. We further confirmed that all HOPS components were coprecipitated with STX17. Knockdown of VPS33A, VPS16, or VPS39 blocked autophagic flux and caused accumulation of STX17- and microtubule-associated protein light chain (LC3)-positive autophagosomes. The endocytic pathway was also affected by knockdown of VPS33A, as previously reported, but not by knockdown of STX17. By contrast, ultraviolet irradiation resistance-associated gene (UVRAG), a known HOPS-interacting protein, did not interact with the STX17-HOPS complex and may not be directly involved in autophagosome-lysosome fusion. Collectively these results suggest that, in addition to its well-established function in the endocytic pathway, HOPS promotes autophagosome-lysosome fusion through interaction with STX17.

PMID:
24554770
PMCID:
PMC3982997
DOI:
10.1091/mbc.E13-08-0447
[Indexed for MEDLINE]
Free PMC Article

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