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Title: Structural Basis for a Munc13–1 Homodimer to Munc13–1/RIM Heterodimer Switch

Journal Article · · PLoS Biology (Online)
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. University of Texas Southwestern Medical Center, Dallas, TX (United States)
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C2 domains are well characterized as Ca2+/phospholipid-binding modules, but little is known about how they mediate protein–protein interactions. In neurons, a Munc13–1 C2A-domain/RIM zinc-finger domain (ZF) heterodimer couples synaptic vesicle priming to presynaptic plasticity. We now show that the Munc13–1 C2A domain homodimerizes, and that homodimerization competes with Munc13–1/RIM heterodimerization. X-ray diffraction studies guided by nuclear magnetic resonance (NMR) experiments reveal the crystal structures of the Munc13–1 C2A-domain homodimer and the Munc13–1 C2A-domain/RIM ZF heterodimer at 1.44 Å and 1.78 Å resolution, respectively. The C2A domain adopts a bsandwich structure with a four-stranded concave side that mediates homodimerization, leading to the formation of an eight-stranded b-barrel. In contrast, heterodimerization involves the bottom tip of the C2A-domain β-sandwich and a C-terminal α-helical extension, which wrap around the RIM ZF domain. Our results describe the structural basis for a Munc13–1 homodimer–Munc13–1/RIM heterodimer switch that may be crucial for vesicle priming and presynaptic plasticity, uncovering at the same time an unexpected versatility of C2 domains as protein–protein interaction modules, and illustrating the power of combining NMR spectroscopy and X-ray crystallography to study protein complexes.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States); University of Texas Southwestern Medical Center, Dallas, TX (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
W-31–109-ENG-38
OSTI ID:
1627147
Journal Information:
PLoS Biology (Online), Vol. 4, Issue 7; ISSN 1545-7885
Publisher:
Public Library of ScienceCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (28)

Regulation of synaptic release-site Ca 2+ channel coupling as a mechanism to control release probability and short-term plasticity journal July 2018
Autoinhibition of Munc18-1 modulates synaptobrevin binding and helps to enable Munc13-dependent regulation of membrane fusion journal May 2017
Molecular Docking and Dynamics Simulation Studies Predict Munc18b as a Target of Mycolactone: A Plausible Mechanism for Granule Exocytosis Impairment in Buruli Ulcer Pathogenesis journal March 2019
Rapid active zone remodeling consolidates presynaptic potentiation journal March 2019
Munc13-4*rab27 complex tethers secretory lysosomes at the plasma membrane journal January 2012
Munc13 mediates the transition from the closed syntaxin–Munc18 complex to the SNARE complex journal April 2011
Mechanism of neurotransmitter release coming into focus: Mechanism of Neurotransmitter Release journal July 2018
Application of Solution NMR to Structural Studies on α-Helical Integral Membrane Proteins journal August 2017
Membrane bridging by Munc13-1 is crucial for neurotransmitter release journal February 2019
A lipid-binding protein mediates rhoptry discharge and invasion in Plasmodium falciparum and Toxoplasma gondii parasites journal September 2019
The Vesicle Priming Factor CAPS Functions as a Homodimer via C2 Domain Interactions to Promote Regulated Vesicle Exocytosis. text January 2016
Soluble α-synuclein facilitates priming and fusion by releasing Ca2+ from thapsigargin-sensitive Ca2+ pool in PC12 cells journal January 2018
E-Syts, a family of membranous Ca2+-sensor proteins with multiple C2 domains journal February 2007
Heterodimerization of UNC-13/RIM regulates synaptic vesicle release probability but not priming in C. elegans journal February 2019
The Vesicle Priming Factor CAPS Functions as a Homodimer via C2 Domain Interactions to Promote Regulated Vesicle Exocytosis journal August 2016
Intrinsic and extrinsic mechanisms of synapse formation and specificity in C. elegans journal April 2019
Enlightening molecular mechanisms through study of protein interactions journal June 2012
The munc13-4–rab27 complex is specifically required for tethering secretory lysosomes at the plasma membrane journal August 2011
Rapid active zone remodeling consolidates presynaptic potentiation posted_content December 2018
Structure of membrane tethers and their role in fusion journal May 2019
Role of Inn1 and its interactions with Hof1 and Cyk3 in promoting cleavage furrow and septum formation in S. cerevisiae journal June 2009
BAIAP3, a C2 domain–containing Munc13 protein, controls the fate of dense-core vesicles in neuroendocrine cells journal June 2017
Structural and Mutational Analysis of Functional Differentiation between Synaptotagmins-1 and -7 journal September 2010
Dysferlin Forms a Dimer Mediated by the C2 Domains and the Transmembrane Domain In Vitro and in Living Cells journal November 2011
Munc13-1 Translocates to the Plasma Membrane in a Doc2B- and Calcium-Dependent Manner journal January 2013
New Insights Into Interactions of Presynaptic Calcium Channel Subtypes and SNARE Proteins in Neurotransmitter Release journal July 2018
Position of UNC-13 in the active zone regulates synaptic vesicle release probability and release kinetics journal November 2013
Mechanistic insights into neurotransmitter release and presynaptic plasticity from the crystal structure of Munc13-1 C1C2BMUN journal February 2017

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Related Subjects

59 BASIC BIOLOGICAL SCIENCES
heteronuclear single quantum coherence
isothermal titration calorimetry
long-term potentiation
nuclear magnetic resonance
root mean square
Sec1/Munc18
Tris(2-carboxyethyl)-phosphine
zinc finger