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Complexin and Ca2+ stimulate SNARE-mediated membrane fusion

Nature Structural & Molecular Biology volume 15, pages 707–713 (2008)Cite this article

Abstract

Ca2+-triggered, synchronized synaptic vesicle fusion underlies interneuronal communication. Complexin is a major binding partner of the SNARE complex, the core fusion machinery at the presynapse. The physiological data on complexin, however, have been at odds with each other, making delineation of its molecular function difficult. Here we report direct observation of two-faceted functions of complexin using the single-vesicle fluorescence fusion assay and EPR. We show that complexin I has two opposing effects on trans-SNARE assembly: inhibition of SNARE complex formation and stabilization of assembled SNARE complexes. Of note, SNARE-mediated fusion is markedly stimulated by complexin, and it is further accelerated by two orders of magnitude in response to an externally applied Ca2+ wave. We suggest that SNARE complexes, complexins and phospholipids collectively form a complex substrate for Ca2+ and Ca2+-sensing fusion effectors in neurotransmitter release.

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Figure 1: Single-vesicle FRET analysis of neuronal SNARE-induced membrane fusion.
Figure 2: Observation of dual functions of complexin I in the absence of Ca2+.
Figure 3: Complexin-assisted, Ca2+-triggered single-vesicle fusion events.
Figure 4: Molecular model of complexin function for Ca2+-triggered neurotransmitter release.

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Acknowledgements

We thank J. Rizo (University of Texas Southwestern Medical Center) for kindly providing the plasmid for complexin I. T.-Y.Y. thanks C. Joo and J. Ryu for help with preparing illustrations and critical reading of the manuscript. This work was supported by US National Institutes of Health grants (R21 GM074526 to T.H. and GM051290-14 to Y.-K.S.).

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Author notes

  1. Tae-Young Yoon

    Present address: Present address: Department of Physics and KAIST Institute for the BioCentury, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea.,

  2. Tae-Young Yoon, Xiaobing Lu and Jiajie Diao: These authors contributed equally to this work.

Authors and Affiliations

  1. Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, 61801-3080, Illinois, USA

    Tae-Young Yoon & Taekjip Ha

  2. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, 61801-3080, Illinois, USA

    Tae-Young Yoon, Jiajie Diao & Taekjip Ha

  3. Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, 4152 Molecular Biology Building, Ames, 50011, Iowa, USA

    Xiaobing Lu, Soo-Min Lee & Yeon-Kyun Shin

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Contributions

T.-Y.Y., T.H. and Y.-K.S. designed research. T.-Y.Y. and J.D. performed the single-vesicle measurements. X.L. performed protein purification and vesicle reconstitution. S.-M.L. and X.L. performed the EPR analysis. T.H. and Y.-K.S. provided project management and contributed to new reagents and analytic tools. T.-Y.Y., T.H. and Y.-K.S. wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Taekjip Ha or Yeon-Kyun Shin.

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Yoon, TY., Lu, X., Diao, J. et al. Complexin and Ca2+ stimulate SNARE-mediated membrane fusion. Nat Struct Mol Biol 15, 707–713 (2008). https://doi.org/10.1038/nsmb.1446

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