Mechanistic Insights into Neurotransmitter Release and Presynaptic Plasticity from the Crystal Structure of Munc13-1 C1C2BMUN
- University of Texas Southwestern Medical Center, United States
- Charité-Universitätsmedizin Berlin, Germany
- Huazhong University of Science and Technology, China
Abstract
Munc13-1 acts as a master regulator of neurotransmitter release, mediating docking-priming of synaptic vesicles and diverse presynaptic plasticity processes. It is unclear how the functions of the multiple domains of Munc13-1 are coordinated. The crystal structure of a Munc13-1 fragment including its C1, C2B and MUN domains (C1C2BMUN) reveals a 19.5 nm-long multi-helical structure with the C1 and C2B domains packed at one end. The similar orientations of the respective diacyglycerol- and Ca2+-binding sites of the C1 and C2B domains suggest that the two domains cooperate in plasma-membrane binding and that activation of Munc13-1 by Ca2+ and diacylglycerol during short-term presynaptic plasticity are closely interrelated. Electrophysiological experiments in mouse neurons support the functional importance of the domain interfaces observed in C1C2BMUN. The structure imposes key constraints for models of neurotransmitter release and suggests that Munc13-1 bridges the vesicle and plasma membranes from the periphery of the membrane-membrane interface.
Data availability
-
C1C2BMUN structurePublicly available at the Protein Data Bank (accession no: 5UE8).
-
Refined MUN domain structurePublicly available at the Protein Data Bank (accession no: 5UF7).
Article and author information
Author details
Christian Rosenmund
Funding
National Institutes of Health (R35 NS097333)
- Josep Rizo
Welch Foundation (I-1304)
- Josep Rizo
German Research Council (SFB958)
- Christian Rosenmund
German Research Council (SFB665)
- Christian Rosenmund
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Reinhard Jahn, Max Planck Institute for Biophysical Chemistry, Germany
Ethics
Animal experimentation: Animal welfare committees of Charité Medical University and the Berlin state government Agency for Health and Social Services approved all protocols for animal maintenance and experiments (license no. T 0220/09).
Version history
- Received: October 21, 2016
- Accepted: February 7, 2017
- Accepted Manuscript published: February 8, 2017 (version 1)
- Version of Record published: March 9, 2017 (version 2)
Copyright
© 2017, Xu et al.
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.
Metrics
-
- 2,854
- views
-
- 723
- downloads
-
- 100
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Mechanistic Insights into Neurotransmitter Release and Presynaptic Plasticity from the Crystal Structure of Munc13-1 C1C2BMUN
eLife 6:e22567.
https://doi.org/10.7554/eLife.22567
Further reading
-
- Structural Biology and Molecular Biophysics
Regulated hydrolysis of the phosphoinositide phosphatidylinositol(4,5)-bis-phosphate to diacylglycerol and inositol-1,4,5-P3 defines a major eukaryotic pathway for translation of extracellular cues to intracellular signaling circuits. Members of the lipid-activated protein kinase C isoenzyme family (PKCs) play central roles in this signaling circuit. One of the regulatory mechanisms employed to downregulate stimulated PKC activity is via a proteasome-dependent degradation pathway that is potentiated by peptidyl-prolyl isomerase Pin1. Here, we show that contrary to prevailing models, Pin1 does not regulate conventional PKC isoforms α and βII via a canonical cis-trans isomerization of the peptidyl-prolyl bond. Rather, Pin1 acts as a PKC binding partner that controls PKC activity via sequestration of the C-terminal tail of the kinase. The high-resolution structure of full-length Pin1 complexed to the C-terminal tail of PKCβII reveals that a novel bivalent interaction mode underlies the non-catalytic mode of Pin1 action. Specifically, Pin1 adopts a conformation in which it uses the WW and PPIase domains to engage two conserved phosphorylated PKC motifs, the turn motif and hydrophobic motif, respectively. Hydrophobic motif is a non-canonical Pin1-interacting element. The structural information combined with the results of extensive binding studies and experiments in cultured cells suggest that non-catalytic mechanisms represent unappreciated modes of Pin1-mediated regulation of AGC kinases and other key enzymes/substrates.
-
- Structural Biology and Molecular Biophysics
Roco proteins entered the limelight after mutations in human LRRK2 were identified as a major cause of familial Parkinson’s disease. LRRK2 is a large and complex protein combining a GTPase and protein kinase activity, and disease mutations increase the kinase activity, while presumably decreasing the GTPase activity. Although a cross-communication between both catalytic activities has been suggested, the underlying mechanisms and the regulatory role of the GTPase domain remain unknown. Several structures of LRRK2 have been reported, but structures of Roco proteins in their activated GTP-bound state are lacking. Here, we use single-particle cryo-electron microscopy to solve the structure of a bacterial Roco protein (CtRoco) in its GTP-bound state, aided by two conformation-specific nanobodies: NbRoco1 and NbRoco2. This structure presents CtRoco in an active monomeric state, featuring a very large GTP-induced conformational change using the LRR-Roc linker as a hinge. Furthermore, this structure shows how NbRoco1 and NbRoco2 collaborate to activate CtRoco in an allosteric way. Altogether, our data provide important new insights into the activation mechanism of Roco proteins, with relevance to LRRK2 regulation, and suggest new routes for the allosteric modulation of their GTPase activity.
