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The SM protein Vps33 and the t-SNARE Habc domain promote fusion pore opening

Nature Structural & Molecular Biology volume 17, pages 710–717 (2010)Cite this article

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Abstract

Intracellular membrane fusion proceeds via distinct stages of membrane docking, hemifusion and fusion pore opening and depends on interacting families of Rab, SNARE and SM proteins. Trans-SNARE complexes dock the membranes in close apposition. Efficient fusion requires further SNARE-associated proteins. They might increase the number of trans-SNARE complexes or the fusogenic potential of a single SNARE complex. We investigated the contributions of the SM protein Vps33 to hemifusion and pore opening between yeast vacuoles. Mutations in Vps33 that weaken its interactions with the SNARE complex allowed normal trans-SNARE pairing and lipid mixing but retarded content mixing. Deleting the Habc domain of the vacuolar t-SNARE Vam3, which interacts with Vps33, had the same effect. This suggests that SM proteins promote fusion pore opening by enhancing the fusogenic activity of a SNARE complex. They should thus be considered integral parts of the fusion machinery.

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Figure 1: Fusion of ΔN-Vam3 vacuoles.
Figure 2: Trans-SNARE assay for WT and ΔN-Vam3.
Figure 3: Fusion of vps33WT and vps33tsf variants.
Figure 4: Structure-based sequence alignments and coimmunoprecipitations of Vam3 and Vps33.
Figure 5: Fusion of vps33WT or vps33tsf-L vacuoles.
Figure 6: Fusion of vps33WT or vps33 D88K vacuoles.
Figure 7: Vps33-Vam3 binding interface.

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Acknowledgements

We thank S. Emr (Weill Institute for Cell and Molecular Biology) for strains and plasmids and V. Comte and M. Reinhardt for assistance. This work was supported by grants from the Swiss National Science Foundation, the Roche Research Foundation, the Human Frontier Science Program and the Leenaards Foundation.

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Authors and Affiliations

  1. Département de Biochimie, Université de Lausanne, Epalinges, Switzerland

    Michel Pieren, Andrea Schmidt & Andreas Mayer

  2. Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA

    Andreas Mayer

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  1. Michel Pieren
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  2. Andrea Schmidt
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M.P. and A.S. performed the experiments; M.P. and A.M. designed the experiments and wrote the paper.

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Correspondence to Andreas Mayer.

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Pieren, M., Schmidt, A. & Mayer, A. The SM protein Vps33 and the t-SNARE Habc domain promote fusion pore opening. Nat Struct Mol Biol 17, 710–717 (2010). https://doi.org/10.1038/nsmb.1809

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