Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 106, Issue 6, Pages 2001-2006Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0812813106
Keywords
exocytosis; SNARE
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Funding
- Graduierten Kolleg [GK1188]
- US National Institutes of Health [NS043391]
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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 (CpxIII) and CpxIV, CpxI and CpxII 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 CpxI was deleted or serine 115, a putative phosphorylation site, was mutated. Transfer of the carboxy-terminal domain of CpxI to CpxIII resulted in a stimulatory CpxIII-I chimera. Thus, the carboxyterminal domains of CpxI and CpxII promote the fusion of high-curvature liposomes.
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