Complexin synchronizes primed vesicle exocytosis and regulates fusion pore dynamics

Dhara, Madhurima; Yarzagaray, Antonio; Schwarz, Yvonne; Dutta, Soumyajit; Grabner, Chad P.; Moghadam, Paanteha K; Bost, Anneka; Schirra, Claudia; Rettig, Jens; Reim, Kerstin; Brose, Nils; Mohrmann, Ralf; Bruns, Dieter

doi:10.1083/jcb.201311085

Cited by 64 publications

(113 citation statements)

References 73 publications

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“…3). Although we cannot exclude the possibility that these mutants exert subtle effects on vesicle pool sizes, or vesicle release kinetics and synchronicity (19,21,31,35), our findings indicate a trans Cpx/SNARE array is not absolutely required for vesicle release following an action potential.…”

Section: Discussionmentioning

confidence: 70%

Genetic analysis of the Complexin trans-clamping model for cross-linking SNARE complexes in vivo

Cho

Kümmel

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

102

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Complexin (Cpx) is a SNARE-binding protein that regulates neurotransmission by clamping spontaneous synaptic vesicle fusion in the absence of Ca 2+ influx while promoting evoked release in response to an action potential. Previous studies indicated Cpx may cross-link multiple SNARE complexes via a trans interaction to function as a fusion clamp. During Ca 2+ influx, Cpx is predicted to undergo a conformational switch and collapse onto a single SNARE complex in a cis-binding mode to activate vesicle release. To test this model in vivo, we performed structure-function studies of the Cpx protein in Drosophila. Using genetic rescue approaches with cpx mutants that disrupt SNARE cross-linking, we find that manipulations that are predicted to block formation of the trans SNARE array disrupt the clamping function of Cpx. Unexpectedly, these same mutants rescue action potential-triggered release, indicating trans-SNARE cross-linking by Cpx is not a prerequisite for triggering evoked fusion. In contrast, mutations that impair Cpxmediated cis-SNARE interactions that are necessary for transition from an open to closed conformation fail to rescue evoked release defects in cpx mutants, although they clamp spontaneous release normally. Our in vivo genetic manipulations support several predictions made by the Cpx cross-linking model, but unexpected results suggest additional mechanisms are likely to exist that regulate Cpx's effects on SNARE-mediated fusion. Our findings also indicate that the inhibitory and activating functions of Cpx are genetically separable, and can be mapped to distinct molecular mechanisms that differentially regulate the SNARE fusion machinery.synapse | neurotransmitter release | exocytosis

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Section: Discussionmentioning

confidence: 70%

Genetic analysis of the Complexin trans-clamping model for cross-linking SNARE complexes in vivo

Cho

Kümmel

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

102

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“…1A): flexible N-and C-terminal domains, an accessory domain, and a central α-helical domain (11). The N-terminal domain (residues 1-27) of Cpx plays a role in activation of fast synchronous release in murine neurons (12)(13)(14) and in isolated chromaffin cells (15). The C-terminal domain (amino acid residues 71-134) binds to phospholipids (16)(17)(18), and it is important for synaptic vesicle priming in neurons (15,16).…”

mentioning

confidence: 99%

“…The N-terminal domain (residues 1-27) of Cpx plays a role in activation of fast synchronous release in murine neurons (12)(13)(14) and in isolated chromaffin cells (15). The C-terminal domain (amino acid residues 71-134) binds to phospholipids (16)(17)(18), and it is important for synaptic vesicle priming in neurons (15,16). Cpx without the C-terminal domain does not suppress spontaneous release in neuronal cultures, but it still activates Ca 2+ -triggered release in neuronal cultures (16) and in a reconstituted system (19).…”

mentioning

confidence: 99%

C-terminal domain of mammalian complexin-1 localizes to highly curved membranes

Gong

Lai

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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In presynaptic nerve terminals, complexin regulates spontaneous "mini" neurotransmitter release and activates Ca 2+ -triggered synchronized neurotransmitter release. We studied the role of the C-terminal domain of mammalian complexin in these processes using singleparticle optical imaging and electrophysiology. The C-terminal domain is important for regulating spontaneous release in neuronal cultures and suppressing Ca 2+ -independent fusion in vitro, but it is not essential for evoked release in neuronal cultures and in vitro. This domain interacts with membranes in a curvature-dependent fashion similar to a previous study with worm complexin [Snead D, Wragg RT, Dittman JS, Eliezer D (2014) Membrane curvature sensing by the C-terminal domain of complexin. Nat Commun 5:4955]. The curvature-sensing value of the C-terminal domain is comparable to that of α-synuclein. Upon replacement of the C-terminal domain with membrane-localizing elements, preferential localization to the synaptic vesicle membrane, but not to the plasma membrane, results in suppression of spontaneous release in neurons. Membrane localization had no measurable effect on evoked postsynaptic currents of AMPA-type glutamate receptors, but mislocalization to the plasma membrane increases both the variability and the mean of the synchronous decay time constant of NMDA-type glutamate receptor evoked postsynaptic currents.

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“…Cpx is also involved in regulating large dense-core vesicle exocytosis [25][26][27] and rapid delivery of AMPA receptors to the plasma membrane [3] . Cpx-deficient chromaffin cells show a significant decrease in both evoked norepinephrine release and the pool size of releasable vesicles [25,26] . In olfactory neurons, Cpx-deficiency is associated with an impairment of Synaptotagmin 10 (Syt10)-regulated insulin-like growth factor-1 (IGF-1) release [27] .…”

Section: Cpx Is Involved In Regulating Various Types Of Exocytotic Prmentioning

confidence: 99%

Regulation of Exocytosis by Complexin

Shin

2015

Journal of Biochemistry and Molecular Biology Research

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AbbreviationsAMPA: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; Cpx: Complexin (also known as Synaphin); GST: glutathione S-transferase; IGF-1: insulin-like growth factor-1; KD: knock-down; KO: knock-out; LTP: long-term potentiation; SNAP-23 or -25: synaptosomal-associated protein 23 or 25; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SNARE complex: a ternary complex composed of Syntaxin, Synaptobrevin, and either SNAP-23 or SNAP-25; Syb2: Synaptobrevin 2 (also known as vesicle-associated membrane protein 2, VAMP2); Syt1: Synaptotagmin 1; Syt10: Synaptotagmin 10; WT: wild-type. INTRODUCTION Ca2+ -triggered exocytosis is an essential cellular process that mediates transmitter release to the extracellular space for intercellular communications particularly in neurons [1][2][3] . The same or similar processes are used for intracellular trafficking to deliver membrane patches or proteins to the plasma membrane [4,5] . Stimulations of neurons cause an increase in cytosolic Ca 2+ concentrations and trigger fusions of synaptic vesicles into the plasma membrane to release transmitters to the extracellular space [1][2][3] . Synaptotagmin 1 -dependent manner [6,7] . Synaptobrevin 2 (Syb2; also known as vesicle-associated membrane protein 2, VAMP2), a vesicular SNARE protein, forms a ternary SNARE complex with Syntaxin and SNAP-25 that are located in the target plasma membrane [8] . ABSTRACTComplexin (Cpx), which is expressed mainly in the nervous system, binds efficiently to the SNARE complex that is composed of either Syntaxin 1 or Syntaxin 3. Both Syntaxin 1 and Syntaxin 3 are involved in mediating synchronous neurotransmitter release in the nervous system. Cpx stabilizes the SNARE complex upon binding, and potentiates the efficacy of synchronous exocytotic process. Cpx is consisted of N-terminal, accessory α-helix, central α-helix, and C-terminal domains. Each domain of Cpx has a distinct function that is differentially involved in the regulation of priming, clamping, and activating in the exocytotic process. These functions of Cpx domains coordinately potentiate the efficacy of synchronous exocytotic process.

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Complexin synchronizes primed vesicle exocytosis and regulates fusion pore dynamics

Abstract: ComplexinII and SynaptotagminI coordinately transform the constitutively active SNARE-mediated fusion mechanism into a highly synchronized, Ca2+-triggered release apparatus.

Cited by 64 publications

References 73 publications

Genetic analysis of the Complexin trans-clamping model for cross-linking SNARE complexes in vivo

Genetic analysis of the Complexin trans-clamping model for cross-linking SNARE complexes in vivo

C-terminal domain of mammalian complexin-1 localizes to highly curved membranes

Regulation of Exocytosis by Complexin

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