The Carboxy-Terminal Domain of Complexin I Stimulates Liposome Fusion

Regulated exocytosis requires tight coupling of the membrane fusion machinery to a triggering signal and a fast response time. Complexins are part of this regulation and, together with synaptotagmins, control calcium-dependent exocytosis. Stimulatory and inhibitory functions have been reported for c...

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Published in:Proceedings of the National Academy of Sciences - PNAS 2009-02, Vol.106 (6), p.2001-2006
Main Authors: Malsam, Jörg, Seiler, Florian, Schollmeier, Yvette, Rusu, Patricia, Krause, Jean Michel, Söllner, Thomas H., Rothman, James E.
Format: Article
Language:English
Subjects:
Adaptor Proteins, Vesicular Transport
Amino Acid Sequence
Amino acids
Binding sites
Biological Sciences
Cell membranes
Cells
Drosophila
Exocytosis
Lipids
Liposomes
Liposomes - chemistry
Low temperature
Mammals
Membrane Fusion
Membranes
Nerve Tissue Proteins - pharmacology
Neurons
Protein isoforms
Protein Structure, Tertiary
Proteins
SNARE proteins
SNARE Proteins - pharmacology
Synaptotagmins
Vesicle-Associated Membrane Protein 2 - pharmacology
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Summary:Regulated exocytosis requires tight coupling of the membrane fusion machinery to a triggering signal and a fast response time. Complexins are part of this regulation and, together with synaptotagmins, control calcium-dependent exocytosis. Stimulatory and inhibitory functions have been reported for complexins. To test if complexins directly affect membrane fusion, we analyzed the 4 known mammalian complexin isoforms in a reconstituted fusion assay. In contrast to complexin III (Cpxlll) and CpxIV, Cpxl and Cpxll stimulated soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-pin assembly and membrane fusion. This stimulatory effect required a preincubation at low temperature and was specific for neuronal t-SNAREs. Stimulation of membrane fusion was lost when the carboxy-terminal domain of Cpxl was deleted or serine 115, a putative phosphorylation site, was mutated. Transfer of the carboxy-terminal domain of Cpxl to Cpxlll resulted in a stimulatory Cpxlll-I chimera. Thus, the carboxyterminal domains of Cpxl and Cpxll promote the fusion of highcurvature liposomes.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0812813106