ORCID Profile
0000-0002-5615-1014
Current Organisations
Institute of Molecular and Cell Biology
,
National University of Singapore
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Publications
Quantitative Analysis of Synaptic Vesicle Rabs Uncovers Distinct Yet Overlapping Roles for Rab3a and Rab27b in Ca2+-Triggered Exocytosis
Publisher: Society for Neuroscience
Date: 06-10-2010
DOI: 10.1523/JNEUROSCI.0907-10.2010
Abstract: Rab GTPases are molecular switches that orchestrate protein complexes before membrane fusion reactions. In synapses, Rab3 and Rab5 proteins have been implicated in the exo-endocytic cycling of synaptic vesicles (SVs), but an involvement of additional Rabs cannot be excluded. Here, combining high-resolution mass spectrometry and chemical labeling (iTRAQ) together with quantitative immunoblotting and fluorescence microscopy, we have determined the exocytotic (Rab3a, Rab3b, Rab3c, and Rab27b) and endocytic (Rab4b, Rab5a/b, Rab10, Rab11b, and Rab14) Rab machinery of SVs. Analysis of two closely related proteins, Rab3a and Rab27b, revealed colocalization in synaptic nerve terminals, where they reside on distinct but overlapping SV pools. Moreover, whereas Rab3a readily dissociates from SVs during Ca 2+ -triggered exocytosis, and is susceptible to membrane extraction by Rab-GDI, Rab27b persists on SV membranes upon stimulation and is resistant to GDI-coupled Rab retrieval. Finally, we demonstrate that selective modulation of the GTP/GDP switch mechanism of Rab27b impairs SV recycling, suggesting that Rab27b, probably in concert with Rab3s, is involved in SV exocytosis.
Author response: The GTPase Rab26 links synaptic vesicles to the autophagy pathway
Publisher: eLife Sciences Publications, Ltd
Date: 21-01-2015
The non-structural 3 (NS3) protein of dengue virus type 2 interacts with human nuclear receptor binding protein and is associated with alterations in membrane structure
Publisher: Elsevier BV
Date: 06-2004
Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter.
Publisher: Proceedings of the National Academy of Sciences
Date: 26-03-2012
Abstract: Presynaptic nerve terminals are formed from preassembled vesicles that are delivered to the prospective synapse by kinesin-mediated axonal transport. However, precisely how the various cargoes are linked to the motor proteins remains unclear. Here, we report a transport complex linking syntaxin 1a (Stx) and Munc18, two proteins functioning in synaptic vesicle exocytosis at the presynaptic plasma membrane, to the motor protein Kinesin-1 via the kinesin adaptor FEZ1. Mutation of the FEZ1 ortholog UNC-76 in Caenorhabditis elegans causes defects in the axonal transport of Stx. We also show that binding of FEZ1 to Kinesin-1 and Munc18 is regulated by phosphorylation, with a conserved site (serine 58) being essential for binding. When expressed in C. elegans , wild-type but not phosphorylation-deficient FEZ1 (S58A) restored axonal transport of Stx. We conclude that FEZ1 operates as a kinesin adaptor for the transport of Stx, with cargo loading and unloading being regulated by protein kinases.
Abstract
Publisher: eLife Sciences Publications, Ltd
Date: 2014
S-Nitrosylation of Divalent Metal Transporter 1 Enhances Iron Uptake to Mediate Loss of Dopaminergic Neurons and Motoric Deficit
Publisher: Society for Neuroscience
Date: 13-08-2018
DOI: 10.1523/JNEUROSCI.3262-17.2018
Abstract: Elevated iron deposition has been reported in Parkinson's disease (PD). However, the route of iron uptake leading to high deposition in the substantia nigra is unresolved. Here, we show a mechanism in enhanced Fe 2+ uptake via S-nitrosylation of alent metal transporter 1 (DMT1). While DMT1 could be S-nitrosylated by exogenous nitric oxide donors, in human PD brains, endogenously S-nitrosylated DMT1 was detected in postmortem substantia nigra. Patch-cl electrophysiological recordings and iron uptake assays confirmed increased Mn 2+ or Fe 2+ uptake through S-nitrosylated DMT1. We identified two major S-nitrosylation sites, C23 and C540, by mass spectrometry, and DMT1 C23A or C540A substitutions abolished nitric oxide (NO)-mediated DMT1 current increase. To evaluate in vivo significance, lipopolysaccharide (LPS) was stereotaxically injected into the substantia nigra of female and male mice to induce inflammation and production of NO. The intranigral LPS injection resulted in corresponding increase in Fe 2+ deposition, JNK activation, dopaminergic neuronal loss and deficit in motoric activity, and these were rescued by the NO synthase inhibitor l -NAME or by the DMT1-selective blocker ebselen. Lentiviral knockdown of DMT1 abolished LPS-induced dopaminergic neuron loss. SIGNIFICANCE STATEMENT Neuroinflammation and high cytoplasmic Fe 2+ levels have been implicated in the initiation and progression of neurodegenerative diseases. Here, we report the unexpected enhancement of the functional activity of transmembrane alent metal transporter 1 (DMT1) by S-nitrosylation. We demonstrated that S-nitrosylation increased DMT1-mediated Fe 2+ uptake, and two cysteines were identified by mass spectrometry to be the sites for S-nitrosylation and for enhanced iron uptake. One conceptual advance is that while DMT1 activity could be increased by external acidification because the gating of the DMT1 transporter is proton motive, we discovered that DMT1 activity could also be enhanced by S-nitrosylation. Significantly, lipopolysaccharide-induced nitric oxide (NO)-mediated neuronal death in the substantia nigra could be ameliorated by using l -NAME, a NO synthase inhibitor, or by ebselen, a DMT1-selective blocker.
Quantitative Comparison of Glutamatergic and GABAergic Synaptic Vesicles Unveils Selectivity for Few Proteins Including MAL2, a Novel Synaptic Vesicle Protein
Publisher: Society for Neuroscience
Date: 06-01-2010
DOI: 10.1523/JNEUROSCI.4074-09.2010
Abstract: Synaptic vesicles (SVs) store neurotransmitters and release them by exocytosis. The vesicular neurotransmitter transporters discriminate which transmitter will be sequestered and stored by the vesicles. However, it is unclear whether the neurotransmitter phenotype of SVs is solely defined by the transporters or whether it is associated with additional proteins. Here we have compared the protein composition of SVs enriched in vesicular glutamate (VGLUT-1) and GABA transporters (VGAT), respectively, using quantitative proteomics. Of quantified proteins, ∼50 were differentially distributed between the populations, with only few of them being specific for SVs. Of these, the most striking differences were observed for the zinc transporter ZnT3 and the vesicle proteins SV2B and SV31 that are associated preferentially with VGLUT-1 vesicles, and for SV2C that is associated mainly with VGAT vesicles. Several additional proteins displayed a preference for VGLUT-1 vesicles including, surprisingly, synaptophysin, synaptotagmins, and syntaxin 1a. Moreover, MAL2, a membrane protein of unknown function distantly related to synaptophysins and SCAMPs, cofractionated with VGLUT-1 vesicles. Both subcellular fractionation and immunolocalization at the light and electron microscopic level revealed that MAL2 is a bona-fide membrane constituent of SVs that is preferentially associated with VGLUT-1-containing nerve terminals. We conclude that SVs specific for different neurotransmitters share the majority of their protein constituents, with only few vesicle proteins showing preferences that, however, are nonexclusive, thus confirming that the vesicular transporters are the only components essential for defining the neurotransmitter phenotype of a SV.
Recombinant non-structural 1 (NS1) protein of dengue-2 virus interacts with human STAT3β protein
Publisher: Elsevier BV
Date: 09-2005
DOI: 10.1016/J.VIRUSRES.2005.03.025
Abstract: A combination of yeast two-hybrid library screening, co-immunoprecipitation and immunofluorescence microscopy demonstrated that dengue-2 virus non-structural 1 (NS1) protein can interact with an N-terminally truncated form of human STAT3beta (DeltaN40-STAT3beta) protein. The NS1 protein interacted with the activated STAT3beta protein in vesicle-like structures in the cell cytoplasm. In addition, transfection of dendritic cells with plasmid expressing NS1 protein also resulted in significant induction of tumor necrosis factor-alpha (TNFalpha) and interleukin-6 (IL-6). Since the STAT3beta protein is an acute-phase response factor, its interaction with NS1 protein may influence the pathological changes observed in dengue fever, dengue hemorrhagic fever and dengue shock syndrome.
The GTPase Rab26 links synaptic vesicles to the autophagy pathway
Publisher: eLife Sciences Publications, Ltd
Date: 02-02-2015
DOI: 10.7554/ELIFE.05597
Abstract: Small GTPases of the Rab family not only regulate target recognition in membrane traffic but also control other cellular functions such as cytoskeletal transport and autophagy. Here we show that Rab26 is specifically associated with clusters of synaptic vesicles in neurites. Overexpression of active but not of GDP-preferring Rab26 enhances vesicle clustering, which is particularly conspicuous for the EGFP-tagged variant, resulting in a massive accumulation of synaptic vesicles in neuronal somata without altering the distribution of other organelles. Both endogenous and induced clusters co-localize with autophagy-related proteins such as Atg16L1, LC3B and Rab33B but not with other organelles. Furthermore, Atg16L1 appears to be a direct effector of Rab26 and binds Rab26 in its GTP-bound form, albeit only with low affinity. We propose that Rab26 selectively directs synaptic and secretory vesicles into preautophagosomal structures, suggesting the presence of a novel pathway for degradation of synaptic vesicles.
Mapping genomic loci implicates genes and synaptic biology in schizophrenia
Publisher: Springer Science and Business Media LLC
Date: 08-04-2022
Tissue-selective restriction of RNA editing of CaV1.3 by splicing factor SRSF9
Publisher: Oxford University Press (OUP)
Date: 04-05-2018
DOI: 10.1093/NAR/GKY348
Related Organisations
Max-Planck-Institut Für Multidisziplinäre Naturwissenschaften
Location: Germany
Related Funding Activities
No related grants have been discovered for John Jia En Chua.