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

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.
Mesh Terms:
Animals, Cell Fusion, Green Fluorescent Proteins, HEK293 Cells, HeLa Cells, Humans, Intracellular Signaling Peptides and Proteins, Lysosomes, Membrane Fusion, Mice, Microtubule-Associated Proteins, Oligopeptides, Phagosomes, Protein Binding, Qa-SNARE Proteins, RNA Interference, RNA, Small Interfering, Tumor Suppressor Proteins, Vesicular Transport Proteins
Mol. Biol. Cell
Date: Apr. 01, 2014
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