A mechanism for exocytotic arrest by the Complexin C-terminus

Abstract
Data availability
Article and author information
Metrics

Abstract

ComplexinII (CpxII) inhibits non-synchronized vesicle fusion, but the underlying mechanisms have remained unclear. Here, we provide evidence that the far C-terminal domain (CTD) of CpxII interferes with SNARE assembly, thereby arresting tonic exocytosis. Acute infusion of a CTD-derived peptide into mouse chromaffin cells enhances synchronous release by diminishing premature vesicle fusion like full-length CpxII, indicating a direct, inhibitory function of the CTD that sets the magnitude of the primed vesicle pool. We describe a high degree of structural similarity between the CpxII CTD and the SNAP25-SN1 domain (C-terminal half) and show that the CTD peptide lowers the rate of SDS-resistant SNARE complex formation in vitro. Moreover, corresponding CpxII:SNAP25 chimeras do restore complexin's function and even 'superclamp' tonic secretion. Collectively, these results support a so far unrecognized clamping mechanism wherein the CpxII C-terminus hinders spontaneous SNARE complex assembly, enabling the build-up of a release-ready pool of vesicles for synchronized Ca²⁺-triggered exocytosis.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files.

Article and author information

Author details

Mazen Makke

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.
Maria Mantero Martinez

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.
Surya Gaya

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-0163-5748
Yvonne Schwarz

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.
Walentina Frisch

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.
Lina Silva-Bermudez

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.
Martin Jung

Institute for Medical Biochemistry and Molecular Biology, University of Saarland, Homburg, Germany

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-1482-7020
Ralf Mohrmann

Institute of Physiology, Otto-von-Guericke University, Magdeburg, Germany

Competing interests
The authors declare that no competing interests exist.
Madhurima Dhara

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

For correspondence
madhurima.dhara@uks.eu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-7745-472X
Dieter Bruns

Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany

For correspondence
dieter.bruns@uks.eu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-2497-1878

Funding

Deutsche Forschungsgemeinschaft (SFB894)

Martin Jung
Dieter Bruns

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.