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Kweon DH, Kong B, Shin YK. Search for a minimal machinery for Ca 2+-triggered millisecond neuroexocytosis. Neuroscience 2018; 420:4-11. [PMID: 30056116 DOI: 10.1016/j.neuroscience.2018.07.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 07/11/2018] [Accepted: 07/18/2018] [Indexed: 11/25/2022]
Abstract
Neurons have the remarkable ability to release a batch of neurotransmitters into the synapse immediately after an action potential. This signature event is made possible by the simultaneous fusion of a number of synaptic vesicles to the plasma membrane upon Ca2+ entry into the active zone. The outcomes of both cellular and in vitro studies suggest that soluble N-ethylmaleimide-sensitive-factor attachment protein receptors (SNAREs) and synaptotagmin 1 (Syt1) constitute the minimal fast exocytosis machinery in the neuron. Syt1 is the major Ca2+-sensor and orchestrates the synchronous start of individual vesicle fusion events while SNAREs are the membrane fusion machinery that dictates the kinetics of each single fusion event. The data also suggest that Ca2+-bound Syt1 is involved in the upstream docking step which leads to an increase in the number of fusion events or the size of the release, leaving the SNARE complex alone to carry out membrane fusion by themselves.
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Affiliation(s)
- Dae-Hyuk Kweon
- Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, South Korea
| | - Byoungjae Kong
- Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, South Korea
| | - Yeon-Kyun Shin
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, United States.
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2
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Abstract
Synaptic vesicles release their vesicular contents to the extracellular space by Ca(2+)-triggered exocytosis. The Ca(2+)-triggered exocytotic process is regulated by synaptotagmin (Syt), a vesicular Ca(2+)-binding C2 domain protein. Synaptotagmin 1 (Syt1), the most studied major isoform among 16 Syt isoforms, mediates Ca(2+)-triggered synaptic vesicle exocytosis by interacting with the target membranes and SNARE/complexin complex. In synapses of the central nervous system, synaptobrevin 2, a major vesicular SNARE protein, forms a ternary SNARE complex with the plasma membrane SNARE proteins, syntaxin 1 and SNAP25. The affinities of Ca(2+)-dependent interactions between Syt1 and its targets (i.e., SNARE complexes and membranes) are well correlated with the efficacies of the corresponding exocytotic processes. Therefore, different SNARE protein isoforms and membrane lipids, which interact with Syt1 with various affinities, are capable of regulating the efficacy of Syt1-mediated exocytosis. Otoferlin, another type of vesicular C2 domain protein that binds to the membrane in a Ca(2+)-dependent manner, is also involved in the Ca(2+)-triggered synaptic vesicle exocytosis in auditory hair cells. However, the functions of otoferlin in the exocytotic process are not well understood. In addition, at least five different types of synaptic vesicle proteins such as synaptic vesicle protein 2, cysteine string protein α, rab3, synapsin, and a group of proteins containing four transmembrane regions, which includes synaptophysin, synaptogyrin, and secretory carrier membrane protein, are involved in modulating the exocytotic process by regulating the formation and trafficking of synaptic vesicles.
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Affiliation(s)
- Ok-Ho Shin
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas
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3
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Ma J, Kelly L, Ingram J, Price TJ, Meriney SD, Dittrich M. New insights into short-term synaptic facilitation at the frog neuromuscular junction. J Neurophysiol 2014; 113:71-87. [PMID: 25210157 DOI: 10.1152/jn.00198.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Short-term synaptic facilitation occurs during high-frequency stimulation, is known to be dependent on presynaptic calcium ions, and persists for tens of milliseconds after a presynaptic action potential. We have used the frog neuromuscular junction as a model synapse for both experimental and computer simulation studies aimed at testing various mechanistic hypotheses proposed to underlie short-term synaptic facilitation. Building off our recently reported excess-calcium-binding-site model of synaptic vesicle release at the frog neuromuscular junction (Dittrich M, Pattillo JM, King JD, Cho S, Stiles JR, Meriney SD. Biophys J 104: 2751-2763, 2013), we have investigated several mechanisms of short-term facilitation at the frog neuromuscular junction. Our studies place constraints on previously proposed facilitation mechanisms and conclude that the presence of a second class of calcium sensor proteins distinct from synaptotagmin can explain known properties of facilitation observed at the frog neuromuscular junction. We were further able to identify a novel facilitation mechanism, which relied on the persistent binding of calcium-bound synaptotagmin molecules to lipids of the presynaptic membrane. In a real physiological context, both mechanisms identified in our study (and perhaps others) may act simultaneously to cause the experimentally observed facilitation. In summary, using a combination of computer simulations and physiological recordings, we have developed a stochastic computer model of synaptic transmission at the frog neuromuscular junction, which sheds light on the facilitation mechanisms in this model synapse.
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Affiliation(s)
- Jun Ma
- Biomedical Applications Group, Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pennsylvania; Joint Carnegie Mellon-University of Pittsburgh PhD Program in Computational Biology, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Lauren Kelly
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Justin Ingram
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Thomas J Price
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Stephen D Meriney
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Markus Dittrich
- Biomedical Applications Group, Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pennsylvania; Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; and Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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4
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Duning K, Wennmann DO, Bokemeyer A, Reissner C, Wersching H, Thomas C, Buschert J, Guske K, Franzke V, Flöel A, Lohmann H, Knecht S, Brand SM, Pöter M, Rescher U, Missler M, Seelheim P, Pröpper C, Boeckers TM, Makuch L, Huganir R, Weide T, Brand E, Pavenstädt H, Kremerskothen J. Common exonic missense variants in the C2 domain of the human KIBRA protein modify lipid binding and cognitive performance. Transl Psychiatry 2013; 3:e272. [PMID: 23778582 PMCID: PMC3693407 DOI: 10.1038/tp.2013.49] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The human KIBRA gene has been linked to human cognition through a lead intronic single-nucleotide polymorphism (SNP; rs17070145) that is associated with episodic memory performance and the risk to develop Alzheimer's disease. However, it remains unknown how this relates to the function of the KIBRA protein. Here, we identified two common missense SNPs (rs3822660G/T [M734I], rs3822659T/G [S735A]) in exon 15 of the human KIBRA gene to affect cognitive performance, and to be in almost complete linkage disequilibrium with rs17070145. The identified SNPs encode variants of the KIBRA C2 domain with distinct Ca(2+) dependent binding preferences for monophosphorylated phosphatidylinositols likely due to differences in the dynamics and folding of the lipid-binding pocket. Our results further implicate the KIBRA protein in higher brain function and provide direction to the cellular pathways involved.
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Affiliation(s)
- K Duning
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - D O Wennmann
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - A Bokemeyer
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - C Reissner
- Department of Anatomy and Molecular Neurobiology, University Münster, Münster, Germany
| | - H Wersching
- Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
| | - C Thomas
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - J Buschert
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - K Guske
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - V Franzke
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - A Flöel
- Department of Neurology, University Hospital Münster, Münster, Germany
| | - H Lohmann
- Department of Neurology, University Hospital Münster, Münster, Germany
| | - S Knecht
- Department of Neurology, University Hospital Münster, Münster, Germany
| | - S-M Brand
- Institute of Sports Medicine, University of Münster, Münster, Germany
| | - M Pöter
- Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, Münster, Germany
| | - U Rescher
- Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, Münster, Germany
| | - M Missler
- Department of Anatomy and Molecular Neurobiology, University Münster, Münster, Germany
| | - P Seelheim
- Institute of Biochemistry, University of Münster, Münster, Germany
| | - C Pröpper
- Institute of Anatomy and Cell Biology, University Ulm, Ulm, Germany
| | - T M Boeckers
- Institute of Anatomy and Cell Biology, University Ulm, Ulm, Germany
| | - L Makuch
- Howard Hughes Medical Center, John Hopkins University, Baltimore, MD, USA
| | - R Huganir
- Howard Hughes Medical Center, John Hopkins University, Baltimore, MD, USA
| | - T Weide
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - E Brand
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - H Pavenstädt
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany
| | - J Kremerskothen
- Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Münster, Germany,Internal Medicine D, Department of Nephrology, Hypertension and Rheumatology, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany. E-mail:
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Dissection of SNARE-driven membrane fusion and neuroexocytosis by wedging small hydrophobic molecules into the SNARE zipper. Proc Natl Acad Sci U S A 2010; 107:22145-50. [PMID: 21135223 DOI: 10.1073/pnas.1006899108] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Neuronal SNARE proteins mediate neurotransmitter release at the synapse by facilitating the fusion of vesicles to the presynaptic plasma membrane. Cognate v-SNAREs and t-SNAREs from the vesicle and the plasma membrane, respectively, zip up and bring about the apposition of two membranes attached at the C-terminal ends. Here, we demonstrate that SNARE zippering can be modulated in the midways by wedging with small hydrophobic molecules. Myricetin, which intercalated into the hydrophobic inner core near the middle of the SNARE complex, stopped SNARE zippering in motion and accumulated the trans-complex, where the N-terminal region of v-SNARE VAMP2 is in the coiled coil with the frayed C-terminal region. Delphinidin and cyanidin inhibited N-terminal nucleation of SNARE zippering. Neuronal SNARE complex in PC12 cells showed the same pattern of vulnerability to small hydrophobic molecules. We propose that the half-zipped trans-SNARE complex is a crucial intermediate waiting for a calcium trigger that leads to fusion pore opening.
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