scholarly journals Normal Biogenesis and Cycling of Empty Synaptic Vesicles in Dopamine Neurons of Vesicular Monoamine Transporter 2 Knockout Mice

2005 ◽  
Vol 16 (1) ◽  
pp. 306-315 ◽  
Author(s):  
Benjamin G. Croft ◽  
Gabriel D. Fortin ◽  
Amadou T. Corera ◽  
Robert H. Edwards ◽  
Alain Beaudet ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Knockout Mice ◽  
Synaptic Vesicles ◽  
Dopamine Neurons ◽  
Vesicular Monoamine Transporter ◽  
Wild Type ◽  
Monoamine Transporter ◽  
Vesicle Biogenesis ◽  
And Function ◽  
Activity Dependent

The neuronal isoform of vesicular monoamine transporter, VMAT2, is responsible for packaging dopamine and other monoamines into synaptic vesicles and thereby plays an essential role in dopamine neurotransmission. Dopamine neurons in mice lacking VMAT2 are unable to store or release dopamine from their synaptic vesicles. To determine how VMAT2-mediated filling influences synaptic vesicle morphology and function, we examined dopamine terminals from VMAT2 knockout mice. In contrast to the abnormalities reported in glutamatergic terminals of mice lacking VGLUT1, the corresponding vesicular transporter for glutamate, we found that the ultrastructure of dopamine terminals and synaptic vesicles in VMAT2 knockout mice were indistinguishable from wild type. Using the activity-dependent dyes FM1-43 and FM2-10, we also found that synaptic vesicles in dopamine neurons lacking VMAT2 undergo endocytosis and exocytosis with kinetics identical to those seen in wild-type neurons. Together, these results demonstrate that dopamine synaptic vesicle biogenesis and cycling are independent of vesicle filling with transmitter. By demonstrating that such empty synaptic vesicles can cycle at the nerve terminal, our study suggests that physiological changes in VMAT2 levels or trafficking at the synapse may regulate dopamine release by altering the ratio of fillable-to-empty synaptic vesicles, as both continue to cycle in response to neural activity.

scholarly journals Munc13 controls the location and efficiency of dense-core vesicle release in neurons

2012 ◽  
Vol 199 (6) ◽  
pp. 883-891 ◽  
Author(s):  
Rhea van de Bospoort ◽  
Margherita Farina ◽  
Sabine K. Schmitz ◽  
Arthur de Jong ◽  
Heidi de Wit ◽  
...  
Keyword(s):  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Dense Core ◽  
Dense Core Vesicle ◽  
Wild Type ◽  
Vesicle Release ◽  
Prolonged Stimulation ◽  
And Function ◽  
Activity Dependent ◽  
Single Vesicle

Neuronal dense-core vesicles (DCVs) contain diverse cargo crucial for brain development and function, but the mechanisms that control their release are largely unknown. We quantified activity-dependent DCV release in hippocampal neurons at single vesicle resolution. DCVs fused preferentially at synaptic terminals. DCVs also fused at extrasynaptic sites but only after prolonged stimulation. In munc13-1/2–null mutant neurons, synaptic DCV release was reduced but not abolished, and synaptic preference was lost. The remaining fusion required prolonged stimulation, similar to extrasynaptic fusion in wild-type neurons. Conversely, Munc13-1 overexpression (M13OE) promoted extrasynaptic DCV release, also without prolonged stimulation. Thus, Munc13-1/2 facilitate DCV fusion but, unlike for synaptic vesicles, are not essential for DCV release, and M13OE is sufficient to produce efficient DCV release extrasynaptically.

scholarly journals Genetic or Toxicant-Induced Disruption of Vesicular Monoamine Storage and Global Metabolic Profiling in Caenorhabditis elegans

2021 ◽  
Author(s):  
Joshua M Bradner ◽  
Vrinda Kalia ◽  
Fion K Lau ◽  
Monica Sharma ◽  
Meghan L Bucher ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Caenorhabditis Elegans ◽  
High Resolution ◽  
High Resolution Mass Spectrometry ◽  
Dopamine Neurons ◽  
Vesicular Monoamine Transporter ◽  
Monoamine Transporter ◽  
C Elegans ◽  
High Resolution Mass ◽  
Resolution Mass

Abstract The proper storage and release of monoamines contributes to a wide range of neuronal activity. Here, we examine the effects of altered vesicular monoamine transport in the nematode Caenorhabditis elegans. The gene cat-1 is responsible for the encoding of the vesicular monoamine transporter (VMAT) in C. elegans and is analogous to the mammalian vesicular monoamine transporter 2 (VMAT2). Our laboratory has previously shown that reduced VMAT2 activity confers vulnerability on catecholamine neurons in mice. The purpose of this article was to determine whether this function is conserved and to determine the impact of reduced VMAT activity in C. elegans. Here we show that deletion of cat-1/VMAT increases sensitivity to the neurotoxicant 1-methyl-4-phenylpyridinium (MPP+) as measured by enhanced degeneration of dopamine neurons. Reduced cat-1/VMAT also induces changes in dopamine-mediated behaviors. High-resolution mass spectrometry-based metabolomics in the whole organism reveals changes in amino acid metabolism, including tyrosine metabolism in the cat-1/VMAT mutants. Treatment with MPP+ disrupted tryptophan metabolism. Both conditions altered glycerophospholipid metabolism, suggesting a convergent pathway of neuronal dysfunction. Our results demonstrate the evolutionarily conserved nature of monoamine function in C. elegans and further suggest that high-resolution mass spectrometry-based metabolomics can be used in this model to study environmental and genetic contributors to complex human disease.

Lack of a Requirement for the Inhibitory Fcγ Receptor In IVIG-Mediated Treatment of ITP

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3338-3338
Author(s):  
Danila Leontyev ◽  
Yulia Katsman ◽  
Xue-Zhong Ma ◽  
Donald R. Branch
Keyword(s):  
Knockout Mice ◽  
Conflicts Of Interest ◽  
Inflammatory Diseases ◽  
Ivig Therapy ◽  
Ivig Treatment ◽  
Wild Type ◽  
Fcγ Receptor ◽  
Antiplatelet Antibody ◽  
And Function ◽  
Knockout Animals

Abstract Abstract 3338 One of the most quoted articles in publications and at International meetings regarding the mechanism of intravenous immunoglobulin (IVIg) therapy in autoimmune and inflammatory diseases is that by Samuelsson et al., Science 291, 484 (2001). This article deals with the mechanism of effect of IVIg being due to an increase in the expression and function of the inhibitory Fcγ receptor (FcγRIIB) in splenic macrophages. The conclusions in this Science paper are based primarily on the use of an experimental mouse model of immune thrombocytopenia (ITP) and mice made deficient in FcγRIIB (FcγRIIB-/- knockouts). We have not been able to support these previous findings but instead find the presence of FcγRIIB receptor not necessary for successful treatment of experimental ITP through IVIg treatment. Administration of IVIg to wild-type Balb/c mice previously made thrombocytopenic using an escalating dose of antiplatelet antibody, MWReg30, leads to amelioration of experimental ITP while in untreated mice, platelet counts stay close to nadir. Similar dynamics of the amelioration of ITP were found using splenectomized or FcγRIIB-/- knockout (Taconic Labs) Balb/c mice. However, as previously published (Blood 15, 558 (2003)), IVIg does not work with FcγRIIB-/- knockout mice that are on a mixed B6:129S4 background, obtained from the Jackson Labs. Indeed, B6 (129S4-Fcgr2btm1Rav/J) FcγRIIB-/- knockout mice made thrombocytopenic are completely unresponsive to IVIg treatment. However, surprisingly, when using the recommended control wild-type mice for this knockout, the B6.129SF2 mouse, we found that this wild-type FcγRIIB+/+ mouse also does not respond to IVIg treatment. Confirmation of genotype was done; thus, we suggest that something about the 129S background prevents a response to IVIg therapy and this phenomenon is independent of the FcγRIIB. We have confirmed that wild-type 129S4 mice made thrombocytopenic do not respond to IVIg. We have also examined the B6 FcγRIIB-/- knockout mice from Taconic Labs which are purported to be fully congenic and these mice also do not respond to IVIg. Because of the lack of response to IVIg of wild-type 129S4 mice, we believe that the Taconic B6 FcγRIIB-/- knockout mice may, in fact, be mixed background as are the Jackson mice. Thus, we plan to use SNP protocols for determination of congenicity, comparing C57BL/6 and 129S4 strains to Taconic and Jackson Labs B6 FcγRIIB-/- knockout mice. We expect to show that both B6 FcγRIIB-/- knockout animals are not fully congenic, being a mixture of both C57BL/6 and 129S4 strains. Previous publications that indicated a lack of response to IVIg using FcγRIIB-/- knockout mice either did not test the fully congenic Taconic Balb/c knockouts and/or failed to use the most suitable control animals with the nonfully congenic B6 knockouts, using instead, C57BL/6 wild-type mice which respond well to IVIg treatment. In order to avoid misinterpretation of results, all experiments testing the role for FcγRIIB in the mechanism of IVIg should be done using Taconic Balb/c FcγRIIB-/- knockout mice until congenicity can be established with the B6 knockout animals. These data taken together lead us to the conclusion that the presence of the FcγRIIB receptor is not important for the therapeutic action of IVIg. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The AP-3 Complex Required for Endosomal Synaptic Vesicle Biogenesis is Associated with a Casein Kinase Ια-Like Isoform

2000 ◽  
Vol 11 (8) ◽  
pp. 2591-2604 ◽  
Author(s):  
Victor V. Faundez ◽  
Regis B. Kelly
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Enzymatic Reaction ◽  
Casein Kinase ◽  
Small Gtpase ◽  
Casein Kinase I ◽  
Vesicle Membranes ◽  
Vesicle Biogenesis ◽  
Hinge Domain

The formation of small vesicles is mediated by cytoplasmic coats the assembly of which is regulated by the activity of GTPases, kinases, and phosphatases. A heterotetrameric AP-3 adaptor complex has been implicated in the formation of synaptic vesicles from PC12 endosomes ( Faundez et al., 1998 ). When the small GTPase ARF1 is prevented from hydrolyzing GTP, we can reconstitute AP-3 recruitment to synaptic vesicle membranes in an assembly reaction that requires temperatures above 15°C and the presence of ATP suggesting that an enzymatic step is involved in the coat assembly. We have now found an enzymatic reaction, the phosphorylation of the AP-3 adaptor complex, that is linked with synaptic vesicle coating. Phosphorylation occurs in the β3 subunit of the complex by a kinase similar to casein kinase 1α. The kinase copurifies with neuronal-specific AP-3. In vitro, purified casein kinase I selectively phosphorylates the β3A and β3B subunit at its hinge domain. Inhibiting the kinase hinders the recruitment of AP-3 to synaptic vesicles. The same inhibitors that prevent coat assembly in vitro also inhibit the formation of synaptic vesicles in PC12 cells. The data suggest, therefore, that the mechanism of AP-3-mediated vesiculation from neuroendocrine endosomes requires the phosphorylation of the adaptor complex at a step during or after AP-3 recruitment to membranes.

scholarly journals Relaxin increases human endothelial progenitor cell NO and migration and vasculogenesis in mice

Blood ◽  
2012 ◽  
Vol 119 (2) ◽  
pp. 629-636 ◽  
Author(s):  
Mark S. Segal ◽  
Laura Sautina ◽  
Shiyu Li ◽  
YanPeng Diao ◽  
Alexander I. Agoulnik ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Vascular Remodeling ◽  
Progenitor Cell ◽  
Therapeutic Potential ◽  
Peptide Hormone ◽  
No Production ◽  
Wild Type ◽  
And Migration ◽  
Relaxin 2 ◽  
And Function

The ovarian peptide hormone, relaxin, circulates during pregnancy, contributing to profound maternal vasodilation through endothelial and nitric oxide (NO)–dependent mechanisms. Circulating numbers of bone marrow–derived endothelial cells (BMDECs), which facilitate angiogenesis and contribute to repair of vascular endothelium, increase during pregnancy. Thus, we hypothesized that relaxin enhances BMDEC NO production, circulating numbers, and function. Recombinant human relaxin-2 (rhRLX) stimulated PI3K/Akt B-dependent NO production in human BMDECs within minutes, and activated BMDEC migration that was inhibited by L-NG-nitroarginine methyl ester. In BMDECs isolated from relaxin/insulin-like family peptide receptor 2 gene (Rxfp2) knockout and wild-type mice, but not Rxfp1 knockout mice, rhRLX rapidly increased NO production. Similarly, rhRLX increased circulating BMDEC number in Rxfp2 knockout and wild-type mice, but not Rxfp1 knockout mice as assessed by colony formation and flow cytometry. Taken together, these results indicate that relaxin effects BMDEC function through the RXFP1 receptor. Finally, both vascularization and incorporation of GFP-labeled BMDECs were stimulated in rhRLX-impregnated Matrigel pellets implanted in mice. To conclude, relaxin is a novel regulator of BMDECs number and function, which has implications for angiogenesis and vascular remodeling in pregnancy, as well as therapeutic potential in vascular disease.

scholarly journals Increased MPTP Neurotoxicity in Vesicular Monoamine Transporter 2 Heterozygote Knockout Mice

2002 ◽  
Vol 70 (5) ◽  
pp. 1973-1978 ◽  
Author(s):  
Raul R. Gainetdinov ◽  
Fabio Fumagalli ◽  
Yan-Min Wang ◽  
Sara R. Jones ◽  
Allan I. Levey ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Vesicular Monoamine Transporter ◽  
Monoamine Transporter ◽  
Vesicular Monoamine Transporter 2

scholarly journals Synaptic Vesicle Protein 2 and Vesicular Monoamine Transporter 1 and 2 Are Expressed in Neuroblastoma

2019 ◽  
Vol 30 (3) ◽  
pp. 173-179
Author(s):  
Kleopatra Georgantzi ◽  
Apostolos V. Tsolakis ◽  
Åke Jakobson ◽  
Rolf Christofferson ◽  
Eva Tiensuu Janson ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Vesicular Monoamine Transporter ◽  
Monoamine Transporter ◽  
Synaptic Vesicle Protein ◽  
Vesicle Protein
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