Synaptotagmin 1

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Josep Rizo - One of the best experts on this subject based on the ideXlab platform.

  • Synaptotagmin 1 munc18 1 and munc13 1 dependent liposome fusion with a few neuronal snares
    Proceedings of the National Academy of Sciences of the United States of America, 2021
    Co-Authors: Karolina P Stepien, Josep Rizo
    Abstract:

    Neurotransmitter release is governed by eight central proteins among other factors: the neuronal SNAREs syntaxin-1, synaptobrevin, and SNAP-25, which form a tight SNARE complex that brings the synaptic vesicle and plasma membranes together; NSF and SNAPs, which disassemble SNARE complexes; Munc18-1 and Munc13-1, which organize SNARE complex assembly; and the Ca2+ sensor Synaptotagmin-1. Reconstitution experiments revealed that Munc18-1, Munc13-1, NSF, and α-SNAP can mediate Ca2+-dependent liposome fusion between synaptobrevin liposomes and syntaxin-1-SNAP-25 liposomes, but high fusion efficiency due to uncontrolled SNARE complex assembly did not allow investigation of the role of Synaptotagmin-1 on fusion. Here, we show that decreasing the synaptobrevin-to-lipid ratio in the corresponding liposomes to very low levels leads to inefficient fusion and that Synaptotagmin-1 strongly stimulates fusion under these conditions. Such stimulation depends on Ca2+ binding to the two C2 domains of Synaptotagmin-1. We also show that anchoring SNAP-25 on the syntaxin-1 liposomes dramatically enhances fusion. Moreover, we uncover a synergy between Synaptotagmin-1 and membrane anchoring of SNAP-25, which allows efficient Ca2+-dependent fusion between liposomes bearing very low synaptobrevin densities and liposomes containing very low syntaxin-1 densities. Thus, liposome fusion in our assays is achieved with a few SNARE complexes in a manner that requires Munc18-1 and Munc13-1 and that depends on Ca2+ binding to Synaptotagmin-1, all of which are fundamental features of neurotransmitter release in neurons.

  • ca2 dependent release of Synaptotagmin 1 from the snare complex on phosphatidylinositol 4 5 bisphosphate containing membranes
    eLife, 2020
    Co-Authors: Rashmi Voleti, Klaudia Jaczynska, Josep Rizo
    Abstract:

    Inside the brain, cells called neurons relay messages from one place to another in the form of electrical signals. When an electrical signal reaches a junction between two neurons (known as a synapse) it triggers small particles called calcium ions to enter one of the cells. This influx of calcium causes vesicles to fuse with the membrane surrounding the neuron and release molecules called neurotransmitters into the small gap between the two neurons. These molecules travel across the gap to activate an electrical signal in the second neuron which then carries the message onwards. A protein known as Synaptotagmin-1 senses calcium ions at synapses and works together with a group of proteins known as the SNARE complex to help vesicles fuse with the cell membrane. Previous studies have reported three different structures of Synaptotagmin-1 bound to the SNARE complex in a different way. But it was unclear which of these binding states actually result in the release of neurotransmitters. To address this question, Voleti, Jaczynska and Rizo studied how and when synptotagmin-1 and the SNARE complex bind together using two approaches known as NMR spectroscopy and fluorescence spectroscopy. The experiments suggest that before calcium enters the synapse, Synaptotagmin-1 is already bound to a surface on the SNARE complex. This binding inhibits the release of neurotransmitters and has been reported in previous studies. Adding calcium ions causes Synaptotagmin-1 to be released from the SNARE complex. This allows Synaptotagmin-1 to interact with the membrane and cooperate with the SNARE complex to trigger vesicle fusion. Finding out how neurons release neurotransmitters at synapses may help us to understand how the brain works. This could provide new insights into how defects in the synapse lead to neurological disorders, such as schizophrenia, and potentially aid the development of new treatments for such conditions.

  • Synaptotagmin 1 and doc2b exhibit distinct membrane remodeling mechanisms
    Biophysical Journal, 2020
    Co-Authors: Raya Sorkin, Josep Rizo, Rashmi Voleti, Margherita Marchetti, Emma Logtenberg, Melissa C Piontek, Emma Kerklingh, Guy Brand, Wouter H Roos, Alexander J Groffen
    Abstract:

    Synaptotagmin-1 (Syt1) is a calcium sensor protein that is critical for neurotransmission and is therefore extensively studied. Here, we use pairs of optically trapped beads coated with SNARE-free synthetic membranes to investigate Syt1-induced membrane remodeling. This activity is compared with that of Doc2b, which contains a conserved C2AB domain and induces membrane tethering and hemifusion in this cell-free model. We find that the soluble C2AB domain of Syt1 strongly affects the probability and strength of membrane-membrane interactions in a strictly Ca2+- and protein-dependent manner. Single-membrane loading of Syt1 yielded the highest probability and force of membrane interactions, whereas in contrast, Doc2b was more effective after loading both membranes. A lipid-mixing assay with confocal imaging reveals that both Syt1 and Doc2b are able to induce hemifusion; however, significantly higher Syt1 concentrations are required. Consistently, both C2AB fragments cause a reduction in the membrane-bending modulus, as measured by a method based on atomic force microscopy. This lowering of the energy required for membrane deformation may contribute to Ca2+-induced fusion.

  • Synaptotagmin 1 and doc2b exhibit distinct membrane remodeling mechanisms
    bioRxiv, 2019
    Co-Authors: Rashmi Voleti, Raya Sorkin, Margherita Marchetti, Emma Logtenberg, Melissa C Piontek, Emma Kerklingh, Guy Brand, Josep Rizo
    Abstract:

    Abstract While the role of Synaptotagmin-1 in living cells has been described in detail, it remains a challenge to dissect the contribution of membrane remodelling by its two cytoplasmic C2 domains (C2AB) to the Ca2+-secretion coupling mechanism. Here, we study membrane remodeling using pairs of optically-trapped beads coated with SNARE-free synthetic membranes. We find that the soluble C2AB domain of Syt1 strongly affects the probability and strength of membrane-membrane interactions in a strictly Ca2+- and protein-dependent manner. A lipid mixing assay with confocal imaging reveals that at low Syt1 concentrations, no hemifusion is observed. Notably, for similar low concentrations of Doc2b hemifusion does occur. Consistently, both C2AB fragments cause a reduction in the membrane bending modulus, as measured by an AFM-based method. This lowering of the energy required for membrane deformation likely contributes to the overall Ca2+-secretion triggering mechanism by calcium sensor proteins. When comparing symmetrical (both sides) and asymmetrical (one side) presence of protein on the membranes, Syt1 favors an asymmetrical but Doc2b a symmetrical configuration, as inferred from higher tether probabilities and break forces. This provides support for the direct bridging hypothesis for Syt-1, while hinting to possible preference for protein-protein (and not protein-membrane) interactions for Doc2b. Overall, our study sheds new light on the mechanism of Ca2+ induced fusion triggering, which is essential for fundamental understanding of secretion of neurotransmitters and endocrine substances.

  • prevalent mechanism of membrane bridging by Synaptotagmin 1
    Proceedings of the National Academy of Sciences of the United States of America, 2013
    Co-Authors: Alpay B Seven, Kyle D Brewer, Liang Shi, Qiuxing Jiang, Josep Rizo
    Abstract:

    Synaptotagmin-1 functions as a Ca2+ sensor in neurotransmitter release through its two C2 domains (the C2A and C2B domain). The ability of Synaptotagmin-1 to bridge two membranes is likely crucial for its function, enabling cooperation with the soluble N-ethylmaleimide sensitive factor adaptor protein receptors (SNAREs) in membrane fusion, but two bridging mechanisms have been proposed. A highly soluble Synaptotagmin-1 fragment containing both domains (C2AB) was shown to bind simultaneously to two membranes via the Ca2+-binding loops at the top of both domains and basic residues at the bottom of the C2B domain (direct bridging mechanism). In contrast, a longer fragment including a linker sequence (lnC2AB) was found to aggregate in solution and was proposed to bridge membranes through trans interactions between lnC2AB oligomers bound to each membrane via the Ca2+-binding loops, with no contact of the bottom of the C2B domain with the membranes. We now show that lnC2AB containing impurities indeed aggregates in solution, but properly purified lnC2AB is highly soluble. Moreover, cryo-EM images reveal that a majority of lnC2AB molecules bridge membranes directly. Fluorescence spectroscopy indicates that the bottom of the C2B domain contacts the membrane in a sizeable population of molecules of both membrane-bound C2AB and membrane-bound lnC2AB. NMR data on nanodiscs show that a fraction of C2AB molecules bind to membranes with antiparallel orientations of the C2 domains. Together with previous studies, these results show that direct bridging constitutes the prevalent mechanism of membrane bridging by both C2AB and lnC2AB, suggesting that this mechanism underlies the function of Synaptotagmin-1 in neurotransmitter release.

Christian Rosenmund - One of the best experts on this subject based on the ideXlab platform.

  • Synaptotagmin 1 drives synchronous ca2 triggered fusion by c2b domain mediated synaptic vesicle membrane attachment
    Nature Neuroscience, 2018
    Co-Authors: Shuwen Chang, Thorsten Trimbuch, Christian Rosenmund
    Abstract:

    The synaptic vesicle (SV) protein Synaptotagmin-1 (Syt1) is the Ca2+ sensor for fast synchronous release. Biochemical and structural data suggest that Syt1 interacts with phospholipids and SNARE complex, but the manner in which these interactions translate into SV fusion remains poorly understood. Using flash-and-freeze electron microscopy, which triggers action potentials with light and coordinately arrests synaptic structures with rapid freezing, we found that synchronous-release-impairing mutations in the Syt1 C2B domain (K325, 327; R398, 399) also disrupt SV-active-zone plasma-membrane attachment. Single action potential induction rescued membrane attachment in these mutants within less than 10 ms through activation of the Syt1 Ca2+-binding site. The rapid SV membrane translocation temporarily correlates with resynchronization of release and paired pulse facilitation. On the basis of these findings, we redefine the role of Syt1 as part of the Ca2+-dependent vesicle translocation machinery and propose that Syt1 enables fast neurotransmitter release by means of its dynamic membrane attachment activities.

  • the janus faced nature of the c2b domain is fundamental for Synaptotagmin 1 function
    Nature Structural & Molecular Biology, 2008
    Co-Authors: Mingshan Xue, Christian Rosenmund, Timothy K Craig, Josep Rizo
    Abstract:

    The Ca2+ binding loops of the C2A and C2B domains of Synaptotagmin-1 are known to be important in Ca2+-triggered neurotransmitter release. Biophysical and in vivo data now indicate that a basic patch on the opposite, Ca2+-independent face of the C2B domain has an equally crucial role.

  • a gain of function mutation in Synaptotagmin 1 reveals a critical role of ca2 dependent soluble n ethylmaleimide sensitive factor attachment protein receptor complex binding in synaptic exocytosis
    The Journal of Neuroscience, 2006
    Co-Authors: Zhiping P Pang, Christian Rosenmund, Ok Ho Shin, Alexander C Meyer, Thomas C Sudhof
    Abstract:

    Synaptotagmin-1, the Ca2+ sensor for fast neurotransmitter release, was proposed to function by Ca2+-dependent phospholipid binding and/or by Ca2+-dependent soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex binding. Extensive in vivo data support the first hypothesis, but testing the second hypothesis has been difficult because no Synaptotagmin-1 mutation is known that selectively interferes with SNARE complex binding. Using knock-in mice that carry aspartate-to-asparagine substitutions in a Ca2+-binding site of Synaptotagmin-1 (the D232N or D238N substitutions), we now show that the D232N mutation dramatically increases Ca2+-dependent SNARE complex binding by native Synaptotagmin-1, but leaves phospholipid binding unchanged. In contrast, the adjacent D238N mutation does not significantly affect SNARE complex binding, but decreases phospholipid binding. Electrophysiological recordings revealed that the D232N mutation increased Ca2+-triggered release, whereas the D238N mutation decreased release. These data establish that fast vesicle exocytosis is driven by a dual Ca2+-dependent activity of Synaptotagmin-1, namely Ca2+-dependent binding both to SNARE complexes and to phospholipids.

  • phosphatidylinositol phosphates as co activators of ca2 binding to c2 domains of Synaptotagmin 1
    Journal of Biological Chemistry, 2006
    Co-Authors: Ok Ho Shin, Christian Rosenmund, Josep Rizo, Jeong-seop Rhee, Jong Cheol Rah, Thomas C Sudhof, Demet Arac
    Abstract:

    Ca2+-dependent phospholipid binding to the C2A and C2B domains of Synaptotagmin 1 is thought to trigger fast neurotransmitter release, but only Ca2+ binding to the C2B domain is essential for release. To investigate the underlying mechanism, we have compared the role of basic residues in Ca2+/phospholipid binding and in release. Mutations in a polybasic sequence on the side of the C2B domain beta-sandwich or in a basic residue in a top Ca2+-binding loop of the C2A domain (R233) cause comparable decreases in the apparent Ca2+ affinity of Synaptotagmin 1 and the Ca2+ sensitivity of release, whereas mutation of the residue homologous to Arg233 in the C2B domain (Lys366) has no effect. Phosphatidylinositol polyphosphates co-activate Ca2+-dependent and -independent phospholipid binding to Synaptotagmin 1, but the effects of these mutations on release only correlate with their effects on the Ca2+-dependent component. These results reveal clear distinctions in the Ca2+-dependent phospholipid binding modes of the Synaptotagmin 1 C2 domains that may underlie their functional asymmetry and suggest that phosphatidylinositol polyphosphates may serve as physiological modulators of Ca2+ affinity of Synaptotagmin 1 in vivo.

  • augmenting neurotransmitter release by enhancing the apparent ca2 affinity of Synaptotagmin 1
    Proceedings of the National Academy of Sciences of the United States of America, 2005
    Co-Authors: Christian Rosenmund, Josep Rizo, Ok Ho Shin, Jeong-seop Rhee, Jong Cheol Rah, Thomas C Sudhof
    Abstract:

    Synaptotagmin 1 likely acts as a Ca2+ sensor in neurotransmitter release by Ca2+-binding to its two C2 domains. This notion was strongly supported by the observation that a mutation in the C2A domain causes parallel decreases in the apparent Ca2+ affinity of Synaptotagmin 1 and in the Ca2+ sensitivity of release. However, this study was based on a single loss-of-function mutation. We now show that tryptophan substitutions in the Synaptotagmin 1 C2 domains act as gain-of-function mutations to increase the apparent Ca2+ affinity of Synaptotagmin 1. The same substitutions, when introduced into Synaptotagmin 1 expressed in neurons, enhance the Ca2+ sensitivity of release. Mutations in the two C2 domains lead to comparable and additive effects in release. Our results thus show that the apparent Ca2+ sensitivity of release is dictated by the apparent Ca2+ affinity of Synaptotagmin 1 in both directions, and that Ca2+ binding to both C2 domains contributes to Ca2+ triggering of release.

Thomas C Sudhof - One of the best experts on this subject based on the ideXlab platform.

  • inositol hexakisphosphate suppresses excitatory neurotransmission via Synaptotagmin 1 c2b domain in the hippocampal neuron
    Proceedings of the National Academy of Sciences of the United States of America, 2012
    Co-Authors: Shao Nian Yang, Ok Ho Shin, Taulant Bacaj, Thomas C Sudhof, Yue Shi, Guang Yang, Perolof Berggren
    Abstract:

    Inositol hexakisphosphate (InsP6) levels rise and fall with neuronal excitation and silence, respectively, in the hippocampus, suggesting potential signaling functions of this inositol polyphosphate in hippocampal neurons. We now demonstrate that intracellular application of InsP6 caused a concentration-dependent inhibition of autaptic excitatory postsynaptic currents (EPSCs) in cultured hippocampal neurons. The treatment did not alter the size and replenishment rate of the readily releasable pool in autaptic neurons. Intracellular exposure to InsP6 did not affect spontaneous EPSCs or excitatory amino acid-activated currents in neurons lacking autapses. The InsP6-induced inhibition of autaptic EPSCs was effectively abolished by coapplication of an antibody to Synaptotagmin-1 C2B domain. Importantly, preabsorption of the antibody with a GST-WT Synaptotagmin-1 C2B domain fragment but not with a GST-mutant Synaptotagmin-1 C2B domain fragment that poorly reacted with the antibody impaired the activity of the antibody on the InsP6-induced inhibition of autaptic EPSCs. Furthermore, K+ depolarization significantly elevated endogenous levels of InsP6 and occluded the inhibition of autaptic EPSCs by exogenous InsP6. These data reveal that InsP6 suppresses excitatory neurotransmission via inhibition of the presynaptic Synaptotagmin-1 C2B domain-mediated fusion via an interaction with the Synaptotagmin Ca2+-binding sites rather than via interference with presynaptic Ca2+ levels, synaptic vesicle trafficking, or inactivation of postsynaptic ionotropic glutamate receptors. Therefore, elevated InsP6 in activated neurons serves as a unique negative feedback signal to control hippocampal excitatory neurotransmission.

  • differential but convergent functions of ca2 binding to Synaptotagmin 1 c2 domains mediate neurotransmitter release
    Proceedings of the National Academy of Sciences of the United States of America, 2009
    Co-Authors: Ok Ho Shin, Josep Rizo, Thomas C Sudhof
    Abstract:

    Neurotransmitter release is triggered by cooperative Ca2+-binding to the Ca2+-sensor protein Synaptotagmin-1. Synaptotagmin-1 contains two C2 domains, referred to as the C2A and C2B domains, that bind Ca2+ with similar properties and affinities. However, Ca2+ binding to the C2A domain is not required for release, whereas Ca2+ binding to the C2B domain is essential for release. We now demonstrate that despite its expendability, Ca2+-binding to the C2A domain significantly contributes to the overall triggering of neurotransmitter release, and determines its Ca2+ cooperativity. Biochemically, Ca2+ induces more tight binding of the isolated C2A domain than of the isolated C2B domain to standard liposomes composed of phosphatidylcholine and phosphatidylserine. However, here we show that surprisingly, the opposite holds true when the double C2A/B-domain fragment of Synaptotagmin-1 is used instead of isolated C2 domains, and when liposomes containing a physiological lipid composition are used. Under these conditions, Ca2+ binding to the C2B domain but not the C2A domain becomes the primary determinant of phospholipid binding. Thus, the unique requirement for Ca2+ binding to the C2B domain for Synaptotagmin-1 in Ca2+-triggered neurotransmitter release may be accounted for, at least in part, by the unusual phospholipid-binding properties of its double C2A/B-domain fragment.

  • Synaptotagmin 1 functions as a ca2 sensor for spontaneous release
    Nature Neuroscience, 2009
    Co-Authors: Ok Ho Shin, Thomas C Sudhof, Zhiping P Pang
    Abstract:

    Spontaneous 'mini' release occurs at all synapses, but its nature remains enigmatic. We found that >95% of spontaneous release in murine cortical neurons was induced by Ca2+-binding to Synaptotagmin-1 (Syt1), the Ca2+ sensor for fast synchronous neurotransmitter release. Thus, spontaneous and evoked release used the same Ca2+-dependent release mechanism. As a consequence, Syt1 mutations that altered its Ca2+ affinity altered spontaneous and evoked release correspondingly. Paradoxically, Syt1 deletions (as opposed to point mutations) massively increased spontaneous release. This increased spontaneous release remained Ca2+ dependent but was activated at lower Ca2+ concentrations and with a lower Ca2+ cooperativity than Synaptotagmin-driven spontaneous release. Thus, in addition to serving as a Ca2+ sensor for spontaneous and evoked release, Syt1 clamped a second, more sensitive Ca2+ sensor for spontaneous release that resembles the Ca2+ sensor for evoked asynchronous release. These data suggest that Syt1 controls both evoked and spontaneous release at a synapse as a simultaneous Ca2+-dependent activator and clamp of exocytosis.

  • a gain of function mutation in Synaptotagmin 1 reveals a critical role of ca2 dependent soluble n ethylmaleimide sensitive factor attachment protein receptor complex binding in synaptic exocytosis
    The Journal of Neuroscience, 2006
    Co-Authors: Zhiping P Pang, Christian Rosenmund, Ok Ho Shin, Alexander C Meyer, Thomas C Sudhof
    Abstract:

    Synaptotagmin-1, the Ca2+ sensor for fast neurotransmitter release, was proposed to function by Ca2+-dependent phospholipid binding and/or by Ca2+-dependent soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex binding. Extensive in vivo data support the first hypothesis, but testing the second hypothesis has been difficult because no Synaptotagmin-1 mutation is known that selectively interferes with SNARE complex binding. Using knock-in mice that carry aspartate-to-asparagine substitutions in a Ca2+-binding site of Synaptotagmin-1 (the D232N or D238N substitutions), we now show that the D232N mutation dramatically increases Ca2+-dependent SNARE complex binding by native Synaptotagmin-1, but leaves phospholipid binding unchanged. In contrast, the adjacent D238N mutation does not significantly affect SNARE complex binding, but decreases phospholipid binding. Electrophysiological recordings revealed that the D232N mutation increased Ca2+-triggered release, whereas the D238N mutation decreased release. These data establish that fast vesicle exocytosis is driven by a dual Ca2+-dependent activity of Synaptotagmin-1, namely Ca2+-dependent binding both to SNARE complexes and to phospholipids.

  • phosphatidylinositol phosphates as co activators of ca2 binding to c2 domains of Synaptotagmin 1
    Journal of Biological Chemistry, 2006
    Co-Authors: Ok Ho Shin, Christian Rosenmund, Josep Rizo, Jeong-seop Rhee, Jong Cheol Rah, Thomas C Sudhof, Demet Arac
    Abstract:

    Ca2+-dependent phospholipid binding to the C2A and C2B domains of Synaptotagmin 1 is thought to trigger fast neurotransmitter release, but only Ca2+ binding to the C2B domain is essential for release. To investigate the underlying mechanism, we have compared the role of basic residues in Ca2+/phospholipid binding and in release. Mutations in a polybasic sequence on the side of the C2B domain beta-sandwich or in a basic residue in a top Ca2+-binding loop of the C2A domain (R233) cause comparable decreases in the apparent Ca2+ affinity of Synaptotagmin 1 and the Ca2+ sensitivity of release, whereas mutation of the residue homologous to Arg233 in the C2B domain (Lys366) has no effect. Phosphatidylinositol polyphosphates co-activate Ca2+-dependent and -independent phospholipid binding to Synaptotagmin 1, but the effects of these mutations on release only correlate with their effects on the Ca2+-dependent component. These results reveal clear distinctions in the Ca2+-dependent phospholipid binding modes of the Synaptotagmin 1 C2 domains that may underlie their functional asymmetry and suggest that phosphatidylinositol polyphosphates may serve as physiological modulators of Ca2+ affinity of Synaptotagmin 1 in vivo.

Matthijs Verhage - One of the best experts on this subject based on the ideXlab platform.

  • post tetanic potentiation lowers the energy barrier for synaptic vesicle fusion independently of Synaptotagmin 1
    eLife, 2020
    Co-Authors: Vincent Huson, Marieke Meijer, Matthijs Verhage, Rien Dekker, Mirelle Ter Veer, Marvin Ruiter, Jan R T Van Weering, L N Cornelisse
    Abstract:

    Previously, we showed that modulation of the energy barrier for synaptic vesicle fusion boosts release rates supralinearly (Schotten, 2015). Here we show that mouse hippocampal synapses employ this principle to trigger Ca2+-dependent vesicle release and post-tetanic potentiation (PTP). We assess energy barrier changes by fitting release kinetics in response to hypertonic sucrose. Mimicking activation of the C2A domain of the Ca2+-sensor Synaptotagmin-1 (Syt1), by adding a positive charge (Syt1D232N) or increasing its hydrophobicity (Syt14W), lowers the energy barrier. Removing Syt1 or impairing its release inhibitory function (Syt19Pro) increases spontaneous release without affecting the fusion barrier. Both phorbol esters and tetanic stimulation potentiate synaptic strength, and lower the energy barrier equally well in the presence and absence of Syt1. We propose a model where tetanic stimulation activates Syt1-independent mechanisms that lower the energy barrier and act additively with Syt1-dependent mechanisms to produce PTP by exerting multiplicative effects on release rates.

  • post tetanic potentiation lowers the energy barrier for synaptic vesicle fusion independently of Synaptotagmin 1
    bioRxiv, 2020
    Co-Authors: Vincent Huson, Marieke Meijer, Matthijs Verhage, Rien Dekker, Mirelle Ter Veer, Marvin Ruiter, Jan R T Van Weering, Niels L Cornelisse
    Abstract:

    Abstract Previously, we showed that modulation of the energy barrier for synaptic vesicle fusion boosts release rates supralinearly (Schotten, 2015). Here we show that mouse hippocampal synapses employ this principle to trigger Ca2+-dependent vesicle release and post-tetanic potentiation (PTP). We assess energy barrier changes by fitting release kinetics in response to hypertonic sucrose. Mimicking activation of the C2A domain of the Ca2+-sensor Synaptotagmin-1 (Syt1), by adding a positive charge (Syt1D232N) or increasing its hydrophobicity (Syt14W), lowers the energy barrier. Removing Syt1 or impairing its release inhibitory function (Syt19Pro) increases spontaneous release without affecting the fusion barrier. Both phorbol esters and tetanic stimulation potentiate synaptic strength, and lower the energy barrier equally well in the presence and absence of Syt1. We propose a model where tetanic stimulation activates Syt1 dependent and independent mechanisms that lower the energy barrier independently in an additive manner to produce PTP by multiplication of release rates.

  • Synaptotagmin 1 enables frequency coding by suppressing asynchronous release in a temperature dependent manner
    Scientific Reports, 2019
    Co-Authors: Vincent Huson, Matthijs Verhage, Maaike A Van Boven, Alexia Stuefer, Niels L Cornelisse
    Abstract:

    To support frequency-coded information transfer, mammalian synapses tightly synchronize neurotransmitter release to action potentials (APs). However, release desynchronizes during AP trains, especially at room temperature. Here we show that suppression of asynchronous release by Synaptotagmin-1 (Syt1), but not release triggering, is highly temperature sensitive, and enhances synchronous release during high-frequency stimulation. In Syt1-deficient synapses, asynchronous release increased with temperature, opposite to wildtype synapses. Mutations in Syt1 C2B-domain polybasic stretch (Syt1 K326Q,K327Q,K331Q) did not affect synchronization during sustained activity, while the previously observed reduced synchronous response to a single AP was confirmed. However, an inflexible linker between the C2-domains (Syt1 9Pro) reduced suppression, without affecting synchronous release upon a single AP. Syt1 9Pro expressing synapses showed impaired synchronization during AP trains, which was rescued by buffering global Ca2+ to prevent asynchronous release. Hence, frequency coding relies on Syt1's temperature sensitive suppression of asynchronous release, an aspect distinct from its known vesicle recruitment and triggering functions.

  • doc2b acts as a calcium sensor for vesicle priming requiring Synaptotagmin 1 munc13 2 and snares
    eLife, 2017
    Co-Authors: Sebastien Houy, Matthijs Verhage, Alexander J Groffen, Iwona Ziomkiewicz, Paulo S Pinheiro, Jakob B Sorensen
    Abstract:

    Doc2B is a cytosolic protein with binding sites for Munc13 and Tctex-1 (dynein light chain), and two C2-domains that bind to phospholipids, Ca2+ and SNAREs. Whether Doc2B functions as a calcium sensor akin to Synaptotagmins, or in other calcium-independent or calcium-dependent capacities is debated. We here show by mutation and overexpression that Doc2B plays distinct roles in two sequential priming steps in mouse adrenal chromaffin cells. Mutating Ca2+-coordinating aspartates in the C2A-domain localizes Doc2B permanently at the plasma membrane, and renders an upstream priming step Ca2+-independent, whereas a separate function in downstream priming depends on SNARE-binding, Ca2+-binding to the C2B-domain of Doc2B, interaction with ubMunc13-2 and the presence of Synaptotagmin-1. Another function of Doc2B - inhibition of release during sustained calcium elevations - depends on an overlapping protein domain (the MID-domain), but is separate from its Ca2+-dependent priming function. We conclude that Doc2B acts as a vesicle priming protein.

  • phosphorylation of Synaptotagmin 1 controls a post priming step in pkc dependent presynaptic plasticity
    Proceedings of the National Academy of Sciences of the United States of America, 2016
    Co-Authors: Arthur P H De Jong, Jakob B Sorensen, Marieke Meijer, Ingrid Saarloos, L N Cornelisse, Ruud F Toonen, Matthijs Verhage
    Abstract:

    Presynaptic activation of the diacylglycerol (DAG)/protein kinase C (PKC) pathway is a central event in short-term synaptic plasticity. Two substrates, Munc13-1 and Munc18-1, are essential for DAG-induced potentiation of vesicle priming, but the role of most presynaptic PKC substrates is not understood. Here, we show that a mutation in Synaptotagmin-1 (Syt1(T112A)), which prevents its PKC-dependent phosphorylation, abolishes DAG-induced potentiation of synaptic transmission in hippocampal neurons. This mutant also reduces potentiation of spontaneous release, but only if alternative Ca(2+) sensors, Doc2A/B proteins, are absent. However, unlike mutations in Munc13-1 or Munc18-1 that prevent DAG-induced potentiation, the Synaptotagmin-1 mutation does not affect paired-pulse facilitation. Furthermore, experiments to probe vesicle priming (recovery after train stimulation and dual application of hypertonic solutions) also reveal no abnormalities. Expression of Synaptotagmin-2, which lacks a seven amino acid sequence that contains the phosphorylation site in Synaptotagmin-1, or a Synaptotagmin-1 variant with these seven residues removed (Syt1(Δ109-116)), supports normal DAG-induced potentiation. These data suggest that this seven residue sequence in Synaptotagmin-1 situated in the linker between the transmembrane and C2A domains is inhibitory in the unphosphorylated state and becomes permissive of potentiation upon phosphorylation. We conclude that Synaptotagmin-1 phosphorylation is an essential step in PKC-dependent potentiation of synaptic transmission, acting downstream of the two other essential DAG/PKC substrates, Munc13-1 and Munc18-1.

Simon J H Brookes - One of the best experts on this subject based on the ideXlab platform.

  • selective coexpression of synaptic proteins α synuclein cysteine string protein α synaptophysin Synaptotagmin 1 and synaptobrevin 2 in vesicular acetylcholine transporter immunoreactive axons in the guinea pig ileum
    The Journal of Comparative Neurology, 2013
    Co-Authors: D F Sharrad, Wei Ping Gai, Simon J H Brookes
    Abstract:

    Parkinson's disease is a neurodegenerative disorder characterized by Lewy bodies and neurites composed mainly of the presynaptic protein α-synuclein. Frequently, Lewy bodies and neurites are identified in the gut of Parkinson's disease patients and may underlie associated gastrointestinal dysfunctions. We recently reported selective expression of α-synuclein in the axons of cholinergic neurons in the guinea pig and human distal gut; however, it is not clear whether α-synuclein expression varies along the gut, nor how closely expression is associated with other synaptic proteins. We used multiple-labeling immunohistochemistry to quantify which neurons in the guinea pig ileum expressed α-synuclein, cysteine string protein-α (CSPα), synaptophysin, Synaptotagmin-1, or synaptobrevin-2 in their axons. Among the 10 neurochemically defined axonal populations, a significantly greater proportion of vesicular acetylcholine transporter-immunoreactive (VAChT-IR) varicosities (80% ± 1.7%, n = 4, P < 0.001) contained α-synuclein immunoreactivity, and a significantly greater proportion of α-synuclein-IR axons also contained VAChT immunoreactivity (78% ± 1.3%, n = 4) compared with any of the other nine populations (P < 0.001). Among synaptophysin-, Synaptotagmin-1-, synaptobrevin-2-, and CSPα-IR varicosities, 98% ± 0.7%, 96% ± 0.7%, 88% ± 1.6%, and 85% ± 2.9% (n = 4) contained α-synuclein immunoreactivity, respectively. Among α-synuclein-IR varicosities, 96% ± 0.9%, 99% ± 0.6%, 83% ± 1.9%, and 87% ± 2.3% (n = 4) contained synaptophysin-, Synaptotagmin-1-, synaptobrevin-2-, and CSPα immunoreactivity, respectively. We report a close association between the expression of α-synuclein and the expression of other synaptic proteins in cholinergic axons in the guinea pig ileum. Selective expression of α-synuclein may relate to the neurotransmitter system utilized and predispose cholinergic enteric neurons to degeneration in Parkinson's disease.

  • selective coexpression of synaptic proteins α synuclein cysteine string protein α synaptophysin Synaptotagmin 1 and synaptobrevin 2 in vesicular acetylcholine transporter immunoreactive axons in the guinea pig ileum
    The Journal of Comparative Neurology, 2013
    Co-Authors: D F Sharrad, Simon J H Brookes
    Abstract:

    Parkinson's disease is a neurodegenerative disorder characterized by Lewy bodies and neurites composed mainly of the presynaptic protein α-synuclein. Frequently, Lewy bodies and neurites are identified in the gut of Parkinson's disease patients and may underlie associated gastrointestinal dysfunctions. We recently reported selective expression of α-synuclein in the axons of cholinergic neurons in the guinea pig and human distal gut; however, it is not clear whether α-synuclein expression varies along the gut, nor how closely expression is associated with other synaptic proteins. We used multiple-labeling immunohistochemistry to quantify which neurons in the guinea pig ileum expressed α-synuclein, cysteine string protein-α (CSPα), synaptophysin, Synaptotagmin-1, or synaptobrevin-2 in their axons. Among the 10 neurochemically defined axonal populations, a significantly greater proportion of vesicular acetylcholine transporter-immunoreactive (VAChT-IR) varicosities (80% ± 1.7%, n = 4, P < 0.001) contained α-synuclein immunoreactivity, and a significantly greater proportion of α-synuclein-IR axons also contained VAChT immunoreactivity (78% ± 1.3%, n = 4) compared with any of the other nine populations (P < 0.001). Among synaptophysin-, Synaptotagmin-1-, synaptobrevin-2-, and CSPα-IR varicosities, 98% ± 0.7%, 96% ± 0.7%, 88% ± 1.6%, and 85% ± 2.9% (n = 4) contained α-synuclein immunoreactivity, respectively. Among α-synuclein-IR varicosities, 96% ± 0.9%, 99% ± 0.6%, 83% ± 1.9%, and 87% ± 2.3% (n = 4) contained synaptophysin-, Synaptotagmin-1-, synaptobrevin-2-, and CSPα immunoreactivity, respectively. We report a close association between the expression of α-synuclein and the expression of other synaptic proteins in cholinergic axons in the guinea pig ileum. Selective expression of α-synuclein may relate to the neurotransmitter system utilized and predispose cholinergic enteric neurons to degeneration in Parkinson's disease. J. Comp. Neurol. 521:2523–2537, 2013. © 2013 Wiley Periodicals, Inc.

Related terms

Synaptotagmin 1 - 15 days free trial to Access Experts & Abstracts