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Rahman MM, Pathak A, Schueler KL, Alsharif H, Michl A, Alexander J, Kim JA, Bhatnagar S. Genetic ablation of synaptotagmin-9 alters tomosyn-1 function to increase insulin secretion from pancreatic β-cells improving glucose clearance. FASEB J 2023; 37:e23075. [PMID: 37432648 PMCID: PMC10348599 DOI: 10.1096/fj.202300291rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023]
Abstract
Stimulus-coupled insulin secretion from the pancreatic islet β-cells involves the fusion of insulin granules to the plasma membrane (PM) via SNARE complex formation-a cellular process key for maintaining whole-body glucose homeostasis. Less is known about the role of endogenous inhibitors of SNARE complexes in insulin secretion. We show that an insulin granule protein synaptotagmin-9 (Syt9) deletion in mice increased glucose clearance and plasma insulin levels without affecting insulin action compared to the control mice. Upon glucose stimulation, increased biphasic and static insulin secretion were observed from ex vivo islets due to Syt9 loss. Syt9 colocalizes and binds with tomosyn-1 and the PM syntaxin-1A (Stx1A); Stx1A is required for forming SNARE complexes. Syt9 knockdown reduced tomosyn-1 protein abundance via proteasomal degradation and binding of tomosyn-1 to Stx1A. Furthermore, Stx1A-SNARE complex formation was increased, implicating Syt9-tomosyn-1-Stx1A complex is inhibitory in insulin secretion. Rescuing tomosyn-1 blocked the Syt9-knockdown-mediated increases in insulin secretion. This shows that the inhibitory effects of Syt9 on insulin secretion are mediated by tomosyn-1. We report a molecular mechanism by which β-cells modulate their secretory capacity rendering insulin granules nonfusogenic by forming the Syt9-tomosyn-1-Stx1A complex. Altogether, Syt9 loss in β-cells decreases tomosyn-1 protein abundance, increasing the formation of Stx1A-SNARE complexes, insulin secretion, and glucose clearance. These outcomes differ from the previously published work that identified Syt9 has either a positive or no effect of Syt9 on insulin secretion. Future work using β-cell-specific deletion of Syt9 mice is key for establishing the role of Syt9 in insulin secretion.
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Affiliation(s)
- Md Mostafizur Rahman
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Asmita Pathak
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | | | - Haifa Alsharif
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Ava Michl
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Justin Alexander
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Jeong-A Kim
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Sushant Bhatnagar
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
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Keller MP, Hudkins KL, Shalev A, Bhatnagar S, Kebede MA, Merrins MJ, Davis DB, Alpers CE, Kimple ME, Attie AD. What the BTBR/J mouse has taught us about diabetes and diabetic complications. iScience 2023; 26:107036. [PMID: 37360692 PMCID: PMC10285641 DOI: 10.1016/j.isci.2023.107036] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023] Open
Abstract
Human and mouse genetics have delivered numerous diabetogenic loci, but it is mainly through the use of animal models that the pathophysiological basis for their contribution to diabetes has been investigated. More than 20 years ago, we serendipidously identified a mouse strain that could serve as a model of obesity-prone type 2 diabetes, the BTBR (Black and Tan Brachyury) mouse (BTBR T+ Itpr3tf/J, 2018) carrying the Lepob mutation. We went on to discover that the BTBR-Lepob mouse is an excellent model of diabetic nephropathy and is now widely used by nephrologists in academia and the pharmaceutical industry. In this review, we describe the motivation for developing this animal model, the many genes identified and the insights about diabetes and diabetes complications derived from >100 studies conducted in this remarkable animal model.
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Affiliation(s)
- Mark P. Keller
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kelly L. Hudkins
- Department of Pathology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Anath Shalev
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, UK
| | - Sushant Bhatnagar
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294, UK
| | - Melkam A. Kebede
- School of Medical Sciences, Faculty of Medicine and Health, Charles Perkins Centre, University of Sydney, Camperdown, Sydney, NSW 2006, Australia
| | - Matthew J. Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
- William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Dawn Belt Davis
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
- William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Charles E. Alpers
- Department of Pathology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Michelle E. Kimple
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
- William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Alan D. Attie
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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3
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Jensen D, Chen J, Turner JA, Stephen JM, Wang YP, Wilson TW, Calhoun VD, Liu J. Epigenetic associations with adolescent grey matter maturation and cognitive development. Front Genet 2023; 14:1222619. [PMID: 37529779 PMCID: PMC10390095 DOI: 10.3389/fgene.2023.1222619] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 06/30/2023] [Indexed: 08/03/2023] Open
Abstract
Introduction: Adolescence, a critical phase of human neurodevelopment, is marked by a tremendous reorganization of the brain and accompanied by improved cognitive performance. This development is driven in part by gene expression, which in turn is partly regulated by DNA methylation (DNAm). Methods: We collected brain imaging, cognitive assessments, and DNAm in a longitudinal cohort of approximately 200 typically developing participants, aged 9-14. This data, from three time points roughly 1 year apart, was used to explore the relationships between seven cytosine-phosphate-guanine (CpG) sites in genes highly expressed in brain tissues (GRIN2D, GABRB3, KCNC1, SLC12A9, CHD5, STXBP5, and NFASC), seven networks of grey matter (GM) volume change, and scores from seven cognitive tests. Results: The demethylation of the CpGs as well as the rates of change in DNAm were significantly related to improvements in total, crystalized, and fluid cognition scores, executive function, episodic memory, and processing speed, as well as several networks of GM volume increases and decreases that highlight typical patterns of brain maturation. Discussion: Our study provides a first look at the DNAm of genes involved in myelination, excitatory and inhibitory receptors, and connectivity, how they are related to the large-scale changes occurring in the brain structure as well as cognition during adolescence.
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Affiliation(s)
- Dawn Jensen
- Tri-Institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - Jiayu Chen
- Tri-Institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
- Department of Computer Science, Georgia State University, Atlanta, GA, United States
| | - Jessica A. Turner
- Tri-Institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
- Wexnar Medical Center, Department of Psychiatry and Behavioral Health, Ohio State University, Columbus, OH, United States
| | | | - Yu-Ping Wang
- Department of Biomedical Engineering, Tulane University, New Orleans, LA, United States
| | - Tony W. Wilson
- Institute for Human Neuroscience, Boys Town National Research Hospital, Omaha, NE, United States
| | - Vince D. Calhoun
- Tri-Institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
- Department of Computer Science, Georgia State University, Atlanta, GA, United States
- The Mind Research Network, Albuquerque, NM, United States
- Psychology Department and Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - Jingyu Liu
- Tri-Institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State University, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
- Department of Computer Science, Georgia State University, Atlanta, GA, United States
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Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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Chow CH, Huang M, Sugita S. The Role of Tomosyn in the Regulation of Neurotransmitter Release. ADVANCES IN NEUROBIOLOGY 2023; 33:233-254. [PMID: 37615869 DOI: 10.1007/978-3-031-34229-5_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Soluble NSF attachment protein receptor (SNARE) proteins play a central role in synaptic vesicle (SV) exocytosis. These proteins include the vesicle-associated SNARE protein (v-SNARE) synaptobrevin and the target membrane-associated SNARE proteins (t-SNAREs) syntaxin and SNAP-25. Together, these proteins drive membrane fusion between synaptic vesicles (SV) and the presynaptic plasma membrane to generate SV exocytosis. In the presynaptic active zone, various proteins may either enhance or inhibit SV exocytosis by acting on the SNAREs. Among the inhibitory proteins, tomosyn, a syntaxin-binding protein, is of particular importance because it plays a critical and evolutionarily conserved role in controlling synaptic transmission. In this chapter, we describe how tomosyn was discovered, how it interacts with SNAREs and other presynaptic regulatory proteins to regulate SV exocytosis and synaptic plasticity, and how its various domains contribute to its synaptic functions.
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Affiliation(s)
- Chun Hin Chow
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
- Faculty of Medicine, Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Mengjia Huang
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
- Faculty of Medicine, Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Shuzo Sugita
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada.
- Faculty of Medicine, Department of Physiology, University of Toronto, Toronto, ON, Canada.
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Hwang J, Thurmond DC. Exocytosis Proteins: Typical and Atypical Mechanisms of Action in Skeletal Muscle. Front Endocrinol (Lausanne) 2022; 13:915509. [PMID: 35774142 PMCID: PMC9238359 DOI: 10.3389/fendo.2022.915509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is of fundamental importance to prevent postprandial hyperglycemia, and long-term deficits in insulin-stimulated glucose uptake underlie insulin resistance and type 2 diabetes. Skeletal muscle is responsible for ~80% of the peripheral glucose uptake from circulation via the insulin-responsive glucose transporter GLUT4. GLUT4 is mainly sequestered in intracellular GLUT4 storage vesicles in the basal state. In response to insulin, the GLUT4 storage vesicles rapidly translocate to the plasma membrane, where they undergo vesicle docking, priming, and fusion via the high-affinity interactions among the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) exocytosis proteins and their regulators. Numerous studies have elucidated that GLUT4 translocation is defective in insulin resistance and type 2 diabetes. Emerging evidence also links defects in several SNAREs and SNARE regulatory proteins to insulin resistance and type 2 diabetes in rodents and humans. Therefore, we highlight the latest research on the role of SNAREs and their regulatory proteins in insulin-stimulated GLUT4 translocation in skeletal muscle. Subsequently, we discuss the novel emerging role of SNARE proteins as interaction partners in pathways not typically thought to involve SNAREs and how these atypical functions reveal novel therapeutic targets for combating peripheral insulin resistance and diabetes.
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Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute at City of Hope, Duarte, CA, United States
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7
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Sauvola CW, Akbergenova Y, Cunningham KL, Aponte-Santiago NA, Littleton JT. The decoy SNARE Tomosyn sets tonic versus phasic release properties and is required for homeostatic synaptic plasticity. eLife 2021; 10:e72841. [PMID: 34713802 PMCID: PMC8612732 DOI: 10.7554/elife.72841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/27/2021] [Indexed: 12/14/2022] Open
Abstract
Synaptic vesicle (SV) release probability (Pr) is a key presynaptic determinant of synaptic strength established by cell-intrinsic properties and further refined by plasticity. To characterize mechanisms that generate Pr heterogeneity between distinct neuronal populations, we examined glutamatergic tonic (Ib) and phasic (Is) motoneurons in Drosophila with stereotyped differences in Pr and synaptic plasticity. We found the decoy soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) Tomosyn is differentially expressed between these motoneuron subclasses and contributes to intrinsic differences in their synaptic output. Tomosyn expression enables tonic release in Ib motoneurons by reducing SNARE complex formation and suppressing Pr to generate decreased levels of SV fusion and enhanced resistance to synaptic fatigue. In contrast, phasic release dominates when Tomosyn expression is low, enabling high intrinsic Pr at Is terminals at the expense of sustained release and robust presynaptic potentiation. In addition, loss of Tomosyn disrupts the ability of tonic synapses to undergo presynaptic homeostatic potentiation.
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Affiliation(s)
- Chad W Sauvola
- Department of Brain and Cognitive Sciences, The Picower Institute of Learning and Memory, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yulia Akbergenova
- Department of Brain and Cognitive Sciences, The Picower Institute of Learning and Memory, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Karen L Cunningham
- Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | | | - J Troy Littleton
- Department of Brain and Cognitive Sciences, The Picower Institute of Learning and Memory, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
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8
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Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
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Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
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9
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Wang S, Liu Y, Crisman L, Wan C, Miller J, Yu H, Shen J. Genetic evidence for an inhibitory role of tomosyn in insulin-stimulated GLUT4 exocytosis. Traffic 2021; 21:636-646. [PMID: 32851733 DOI: 10.1111/tra.12760] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/21/2020] [Accepted: 08/22/2020] [Indexed: 12/11/2022]
Abstract
Exocytosis is a vesicle fusion process driven by soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). A classic exocytic pathway is insulin-stimulated translocation of the glucose transporter type 4 (GLUT4) from intracellular vesicles to the plasma membrane in adipocytes and skeletal muscles. The GLUT4 exocytic pathway plays a central role in maintaining blood glucose homeostasis and is compromised in insulin resistance and type 2 diabetes. A candidate regulator of GLUT4 exocytosis is tomosyn, a soluble protein expressed in adipocytes. Tomosyn directly binds to GLUT4 exocytic SNAREs in vitro but its role in GLUT4 exocytosis was unknown. In this work, we used CRISPR-Cas9 genome editing to delete the two tomosyn-encoding genes in adipocytes. We observed that both basal and insulin-stimulated GLUT4 exocytosis was markedly elevated in the double knockout (DKO) cells. By contrast, adipocyte differentiation and insulin signaling remained intact in the DKO adipocytes. In a reconstituted liposome fusion assay, tomosyn inhibited all the SNARE complexes underlying GLUT4 exocytosis. The inhibitory activity of tomosyn was relieved by NSF and α-SNAP, which act in concert to remove tomosyn from GLUT4 exocytic SNAREs. Together, these studies revealed an inhibitory role for tomosyn in insulin-stimulated GLUT4 exocytosis in adipocytes. We suggest that tomosyn-arrested SNAREs represent a reservoir of fusion capacity that could be harnessed to treat patients with insulin resistance and type 2 diabetes.
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Affiliation(s)
- Shifeng Wang
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA.,Department of Chinese Medicine Information Science, Beijing University of Chinese Medicine, Beijing, China
| | - Yinghui Liu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Lauren Crisman
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Jessica Miller
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Haijia Yu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
| | - Jingshi Shen
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA
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10
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Melland H, Carr EM, Gordon SL. Disorders of synaptic vesicle fusion machinery. J Neurochem 2020; 157:130-164. [PMID: 32916768 DOI: 10.1111/jnc.15181] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/20/2020] [Accepted: 08/26/2020] [Indexed: 12/11/2022]
Abstract
The revolution in genetic technology has ushered in a new age for our understanding of the underlying causes of neurodevelopmental, neuromuscular and neurodegenerative disorders, revealing that the presynaptic machinery governing synaptic vesicle fusion is compromised in many of these neurological disorders. This builds upon decades of research showing that disturbance to neurotransmitter release via toxins can cause acute neurological dysfunction. In this review, we focus on disorders of synaptic vesicle fusion caused either by toxic insult to the presynapse or alterations to genes encoding the key proteins that control and regulate fusion: the SNARE proteins (synaptobrevin, syntaxin-1 and SNAP-25), Munc18, Munc13, synaptotagmin, complexin, CSPα, α-synuclein, PRRT2 and tomosyn. We discuss the roles of these proteins and the cellular and molecular mechanisms underpinning neurological deficits in these disorders.
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Affiliation(s)
- Holly Melland
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Elysa M Carr
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
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11
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Madera-Salcedo IK, Danelli L, Tiwari N, Dema B, Pacreau E, Vibhushan S, Birnbaum J, Agabriel C, Liabeuf V, Klingebiel C, Menasche G, Macias-Silva M, Benhamou M, Charles N, González-Espinosa C, Vitte J, Blank U. Tomosyn functions as a PKCδ-regulated fusion clamp in mast cell degranulation. Sci Signal 2018; 11:11/537/eaan4350. [DOI: 10.1126/scisignal.aan4350] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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12
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Saldate JJ, Shiau J, Cazares VA, Stuenkel EL. The ubiquitin-proteasome system functionally links neuronal Tomosyn-1 to dendritic morphology. J Biol Chem 2017; 293:2232-2246. [PMID: 29269412 DOI: 10.1074/jbc.m117.815514] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 12/02/2017] [Indexed: 12/29/2022] Open
Abstract
Altering the expression of Tomosyn-1 (Tomo-1), a soluble, R-SNARE domain-containing protein, significantly affects behavior in mice, Drosophila, and Caenorhabditis elegans Yet, the mechanisms that modulate Tomo-1 expression and its regulatory activity remain poorly defined. Here, we found that Tomo-1 expression levels influence postsynaptic spine density. Tomo-1 overexpression increased dendritic spine density, whereas Tomo-1 knockdown (KD) decreased spine density. These findings identified a novel action of Tomo-1 on dendritic spines, which is unique because it occurs independently of Tomo-1's C-terminal R-SNARE domain. We also demonstrated that the ubiquitin-proteasome system (UPS), which is known to influence synaptic strength, dynamically regulates Tomo-1 protein levels. Immunoprecipitated and affinity-purified Tomo-1 from cultured rat hippocampal neurons was ubiquitinated, and the levels of ubiquitinated Tomo-1 dramatically increased upon pharmacological proteasome blockade. Moreover, Tomo-1 ubiquitination appeared to be mediated through an interaction with the E3 ubiquitin ligase HRD1, as immunoprecipitation of Tomo-1 from neurons co-precipitated HRD1, and this interaction increases upon proteasome inhibition. Further, in vitro reactions indicated direct, HRD1 concentration-dependent Tomo-1 ubiquitination. We also noted that the UPS regulates both Tomo-1 expression and functional output, as HRD1 KD in hippocampal neurons increased Tomo-1 protein level and dendritic spine density. Notably, the effect of HRD1 KD on spine density was mitigated by additional KD of Tomo-1, indicating a direct HRD1/Tomo-1 effector relationship. In summary, our results indicate that the UPS is likely to participate in tuning synaptic efficacy and spine dynamics by precise regulation of neuronal Tomo-1 levels.
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Affiliation(s)
| | - Jason Shiau
- the Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, Michigan 48109-5624
| | - Victor A Cazares
- the Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, Michigan 48109-5624
| | - Edward L Stuenkel
- From the Neuroscience Graduate Program and .,the Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, Michigan 48109-5624
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13
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Ehrmann I, Gazzara MR, Pagliarini V, Dalgliesh C, Kheirollahi-Chadegani M, Xu Y, Cesari E, Danilenko M, Maclennan M, Lowdon K, Vogel T, Keskivali-Bond P, Wells S, Cater H, Fort P, Santibanez-Koref M, Middei S, Sette C, Clowry GJ, Barash Y, Cunningham MO, Elliott DJ. A SLM2 Feedback Pathway Controls Cortical Network Activity and Mouse Behavior. Cell Rep 2017; 17:3269-3280. [PMID: 28009295 PMCID: PMC5199341 DOI: 10.1016/j.celrep.2016.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 10/25/2016] [Accepted: 11/29/2016] [Indexed: 02/07/2023] Open
Abstract
The brain is made up of trillions of synaptic connections that together form neural networks needed for normal brain function and behavior. SLM2 is a member of a conserved family of RNA binding proteins, including Sam68 and SLM1, that control splicing of Neurexin1-3 pre-mRNAs. Whether SLM2 affects neural network activity is unknown. Here, we find that SLM2 levels are maintained by a homeostatic feedback control pathway that predates the divergence of SLM2 and Sam68. SLM2 also controls the splicing of Tomosyn2, LysoPLD/ATX, Dgkb, Kif21a, and Cask, each of which are important for synapse function. Cortical neural network activity dependent on synaptic connections between SLM2-expressing-pyramidal neurons and interneurons is decreased in Slm2-null mice. Additionally, these mice are anxious and have a decreased ability to recognize novel objects. Our data reveal a pathway of SLM2 homeostatic auto-regulation controlling brain network activity and behavior. SLM2 splicing targets are spatially controlled within the hippocampus RNA-seq reveals SLM2 feedback control and synaptic protein splicing targets Loss of SLM2 dampens patterns of hippocampal γ oscillations Loss of SLM2 changes mouse behavior that depends on these neural networks
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Affiliation(s)
- Ingrid Ehrmann
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Matthew R Gazzara
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Vittoria Pagliarini
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome and Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Caroline Dalgliesh
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | | | - Yaobo Xu
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Eleonora Cesari
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome and Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Marina Danilenko
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Marie Maclennan
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Kate Lowdon
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Tanja Vogel
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Medical Faculty, University of Freiburg, 79104 Freiburg, Germany
| | | | - Sara Wells
- Mary Lyon Centre, MRC Harwell Institute, Oxfordshire OX11 ORD, UK
| | - Heather Cater
- Mary Lyon Centre, MRC Harwell Institute, Oxfordshire OX11 ORD, UK
| | - Philippe Fort
- Université Montpellier, UMR 5237, Centre de Recherche de Biologie cellulaire de Montpellier, CNRS, Montpellier 34293, France
| | | | - Silvia Middei
- Institute of Cell Biology and Neurobiology, Consiglio Nazionale delle Ricerche, Via E. Ramarini 32, 00015 Monterotondo Scalo-Roma, Italy
| | - Claudio Sette
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00133 Rome and Laboratory of Neuroembryology, Fondazione Santa Lucia, 00143 Rome, Italy
| | - Gavin J Clowry
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
| | - Yoseph Barash
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Computer and Information Science, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Mark O Cunningham
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
| | - David J Elliott
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK.
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Batten SR, Matveeva EA, Whiteheart SW, Vanaman TC, Gerhardt GA, Slevin JT. Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn-1 gene. Brain Behav 2017; 7:e00795. [PMID: 28948088 PMCID: PMC5607557 DOI: 10.1002/brb3.795] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/29/2017] [Accepted: 07/02/2017] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION In kindling, repeated electrical stimulation of certain brain areas causes progressive and permanent intensification of epileptiform activity resulting in generalized seizures. We focused on the role(s) of glutamate and a negative regulator of glutamate release, STXBP5/tomosyn-1, in kindling. METHODS Stimulating electrodes were implanted in the amygdala and progression to two successive Racine stage 5 seizures was measured in wild-type and STXBP5/tomosyn-1-/- (Tom-/-) animals. Glutamate release measurements were performed in distinct brain regions using a glutamate-selective microelectrode array (MEA). RESULTS Naïve Tom-/- mice had significant increases in KCl-evoked glutamate release compared to naïve wild type as measured by MEA of presynaptic release in the hippocampal dentate gyrus (DG). Kindling progression was considerably accelerated in Tom-/- mice, requiring fewer stimuli to reach a fully kindled state. Following full kindling, MEA measurements of both kindled Tom+/+ and Tom-/- mice showed significant increases in KCl-evoked and spontaneous glutamate release in the DG, indicating a correlation with the fully kindled state independent of genotype. Resting glutamate levels in all hippocampal subregions were significantly lower in the kindled Tom-/- mice, suggesting possible changes in basal control of glutamate circuitry in the kindled Tom-/- mice. CONCLUSIONS Our studies demonstrate that increased glutamate release in the hippocampal DG correlates with acceleration of the kindling process. Although STXBP5/tomosyn-1 loss increased evoked glutamate release in naïve animals contributing to their prokindling phenotype, the kindling process can override any attenuating effect of STXBP5/tomosyn-1. Loss of this "braking" effect of STXBP5/tomosyn-1 on kindling progression may set in motion an alternative but ultimately equally ineffective compensatory response, detected here as reduced basal glutamate release.
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Affiliation(s)
- Seth R. Batten
- Department of PsychologyUniversity of KentuckyCollege of Arts and SciencesLexingtonKYUSA
| | - Elena A. Matveeva
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Sidney W. Whiteheart
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Thomas C. Vanaman
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Greg A. Gerhardt
- Department of NeuroscienceUniversity of Kentucky Medical CenterLexingtonKYUSA
- Department of NeurologyUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - John T. Slevin
- Neurology ServiceVeterans Affairs Medical CenterLexingtonKYUSA
- Department of NeurologyUniversity of Kentucky Medical CenterLexingtonKYUSA
- Department of Pharmacology and Nutritional SciencesUniversity of Kentucky Medical CenterLexingtonKYUSA
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15
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Geerts CJ, Mancini R, Chen N, Koopmans FTW, Li KW, Smit AB, van Weering JRT, Verhage M, Groffen AJA. Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains. PLoS One 2017; 12:e0180912. [PMID: 28746398 PMCID: PMC5529015 DOI: 10.1371/journal.pone.0180912] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/22/2017] [Indexed: 02/03/2023] Open
Abstract
The secretory pathway in neurons requires efficient targeting of cargos and regulatory proteins to their release sites. Tomosyn contributes to synapse function by regulating synaptic vesicle (SV) and dense-core vesicle (DCV) secretion. While there is large support for the presynaptic accumulation of tomosyn in fixed preparations, alternative subcellular locations have been suggested. Here we studied the dynamic distribution of tomosyn-1 (Stxbp5) and tomosyn-2 (Stxbp5l) in mouse hippocampal neurons and observed a mixed diffuse and punctate localization pattern of both isoforms. Tomosyn-1 accumulations were present in axons and dendrites. As expected, tomosyn-1 was expressed in about 75% of the presynaptic terminals. Interestingly, also bidirectional moving tomosyn-1 and -2 puncta were observed. Despite the lack of a membrane anchor these puncta co-migrated with synapsin and neuropeptide Y, markers for respectively SVs and DCVs. Genetic blockade of two known tomosyn interactions with synaptotagmin-1 and its cognate SNAREs did not abolish its vesicular co-migration, suggesting an interplay of protein interactions mediated by the WD40 and SNARE domains. We hypothesize that the vesicle-binding properties of tomosyns may control the delivery, pan-synaptic sharing and secretion of neuronal signaling molecules, exceeding its canonical role at the plasma membrane.
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Affiliation(s)
- Cornelia J. Geerts
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Roberta Mancini
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Ning Chen
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Frank T. W. Koopmans
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Ka Wan Li
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - August B. Smit
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | | | - Matthijs Verhage
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, The Netherlands
| | - Alexander J. A. Groffen
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, The Netherlands
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16
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Dynamic Partitioning of Synaptic Vesicle Pools by the SNARE-Binding Protein Tomosyn. J Neurosci 2017; 36:11208-11222. [PMID: 27807164 DOI: 10.1523/jneurosci.1297-16.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 09/13/2016] [Indexed: 12/13/2022] Open
Abstract
Neural networks engaged in high-frequency activity rely on sustained synaptic vesicle recycling and coordinated recruitment from functionally distinct synaptic vesicle (SV) pools. However, the molecular pathways matching neural activity to SV dynamics and release requirements remain unclear. Here we identify unique roles of SNARE-binding Tomosyn1 (Tomo1) proteins as activity-dependent substrates that regulate dynamics of SV pool partitioning at rat hippocampal synapses. Our analysis is based on monitoring changes in distinct functionally defined SV pools via V-Glut1-pHluorin fluorescence in cultured hippocampal neurons in response to alterations in presynaptic protein expression. Specifically, we find knockdown of Tomo1 facilitates release efficacy from the Readily Releasable Pool (RRP), and regulates SV distribution to the Total Recycling Pool (TRP), which is matched by a decrease in the SV Resting Pool. Notably, these effects were reversed by Tomo1 rescue and overexpression. Further, we identify that these actions of Tomo1 are regulated via activity-dependent phosphorylation by cyclin-dependent kinase 5 (Cdk5). Assessment of molecular interactions that may contribute to these actions identified Tomo1 interaction with the GTP-bound state of Rab3A, an SV GTPase involved in SV targeting and presynaptic membrane tethering. In addition, Tomo1 via Rab3A-GTP was also observed to interact with Synapsin 1a/b cytoskeletal interacting proteins. Finally, our data indicate that Tomo1 regulation of SV pool sizes serves to adapt presynaptic neurotransmitter release to chronic silencing of network activity. Overall, the results establish Tomo1 proteins as central mediators in neural activity-dependent changes in SV distribution among SV pools. SIGNIFICANCE STATEMENT Although information transfer at central synapses via sustained high-frequency neural activity requires coordinated synaptic vesicle (SV) recycling, the mechanism(s) by which synapses sense and dynamically modify SV pools to match network demands remains poorly defined. To advance understanding, we quantified SV pool sizes and their sensitivity to neural activity while altering Tomo1 expression, a putative regulator of the presynaptic Readily Releasable Pool. Remarkably, we find Tomo1 actions to extend beyond the Readily Releasable Pool to mediate the Total Recycling Pool and SV Resting Pool distribution, and this action is sensitive to neural activity through Cdk5 phosphorylation of Tomo1. Moreover, Tomo1 appears to exert these actions through interaction with Rab3A-GTP and synapsin proteins. Together, our results argue that Tomo1 is a central mediator of SV availability for neurotransmission.
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17
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Abstract
STAR (signal transduction and activation of RNA) proteins regulate splicing of target genes that have roles in neural connectivity, survival and myelination in the vertebrate nervous system. These regulated splicing targets include mRNAs such as the Neurexins (Nrxn), SMN2 (survival of motor neuron) and MAG (myelin-associated glycoprotein). Recent work has made it possible to identify and validate STAR protein splicing targets in vivo by using genetically modified mouse models. In this review, we will discuss the importance of STAR protein splicing targets in the CNS (central nervous system).
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18
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SUMOylation and calcium control syntaxin-1A and secretagogin sequestration by tomosyn to regulate insulin exocytosis in human ß cells. Sci Rep 2017; 7:248. [PMID: 28325894 PMCID: PMC5428262 DOI: 10.1038/s41598-017-00344-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 02/22/2017] [Indexed: 11/09/2022] Open
Abstract
Insulin secretion from pancreatic ß cells is a multistep process that requires the coordination of exocytotic proteins that integrate diverse signals. These include signals derived from metabolic control of post-translational SUMOylation and depolarization-induced rises in intracellular Ca2+. Here we show that tomosyn, which suppresses insulin exocytosis by binding syntaxin1A, does so in a manner which requires its SUMOylation. Glucose-dependent de-SUMOylation of tomosyn1 at K298 releases syntaxin1A and controls the amplification of exocytosis in concert with a recently-identified tomosyn1-interacting partner; the Ca2+-binding protein secretagogin, which dissociates from tomosyn1 in response to Ca2+-raising stimuli and is required for insulin granule trafficking and exocytosis downstream of Ca2+ influx. Together our results suggest that tomosyn acts as a key signaling hub in insulin secretion by integrating signals mediated by metabolism-dependent de-SUMOylation and electrically-induced entry of Ca2+ to regulate the availability of exocytotic proteins required for the amplification of insulin secretion.
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19
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Zhu QM, Ko KA, Ture S, Mastrangelo MA, Chen MH, Johnson AD, O'Donnell CJ, Morrell CN, Miano JM, Lowenstein CJ. Novel Thrombotic Function of a Human SNP in STXBP5 Revealed by CRISPR/Cas9 Gene Editing in Mice. Arterioscler Thromb Vasc Biol 2017; 37:264-270. [PMID: 28062498 PMCID: PMC5269475 DOI: 10.1161/atvbaha.116.308614] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/13/2016] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To identify and characterize the effect of a SNP (single-nucleotide polymorphism) in the STXBP5 locus that is associated with altered thrombosis in humans. GWAS (genome-wide association studies) have identified numerous SNPs associated with human thrombotic phenotypes, but determining the functional significance of an individual candidate SNP can be challenging, particularly when in vivo modeling is required. Recent GWAS led to the discovery of STXBP5 as a regulator of platelet secretion in humans. Further clinical studies have identified genetic variants of STXBP5 that are linked to altered plasma von Willebrand factor levels and thrombosis in humans, but the functional significance of these variants in STXBP5 is not understood. APPROACH AND RESULTS We used CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated 9) techniques to produce a precise mouse model carrying a human coding SNP rs1039084 (encoding human p. N436S) in the STXBP5 locus associated with decreased thrombosis. Mice carrying the orthologous human mutation (encoding p. N437S in mouse STXBP5) have lower plasma von Willebrand factor levels, decreased thrombosis, and decreased platelet secretion compared with wild-type mice. This thrombosis phenotype recapitulates the phenotype of humans carrying the minor allele of rs1039084. Decreased plasma von Willebrand factor and platelet activation may partially explain the decreased thrombotic phenotype in mutant mice. CONCLUSIONS Using precise mammalian genome editing, we have identified a human nonsynonymous SNP rs1039084 in the STXBP5 locus as a causal variant for a decreased thrombotic phenotype. CRISPR/Cas9 genetic editing facilitates the rapid and efficient generation of animals to study the function of human genetic variation in vascular diseases.
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Affiliation(s)
- Qiuyu Martin Zhu
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Kyung Ae Ko
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Sara Ture
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Michael A Mastrangelo
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Ming-Huei Chen
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Andrew D Johnson
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Christopher J O'Donnell
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Craig N Morrell
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Joseph M Miano
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.)
| | - Charles J Lowenstein
- From the Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, NY (Q.M.Z., K.A.K., S.T., M.A.M., C.N.M., J.M.M., C.J.L.); Division of Intramural Research, National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, and NHLBI Framingham Heart Study, Framingham, MA (M.-H.C., A.D.J., C.J.O.D.); and Cardiovascular Division, Massachusetts General Hospital, Harvard Medical School, Boston (C.J.O.D.).
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20
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Ferdaoussi M, MacDonald PE. Toward Connecting Metabolism to the Exocytotic Site. Trends Cell Biol 2016; 27:163-171. [PMID: 27932063 DOI: 10.1016/j.tcb.2016.10.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/28/2016] [Accepted: 10/31/2016] [Indexed: 12/14/2022]
Abstract
Within cells the regulated exocytosis of secretory granules controls multiple physiological functions, including endocrine hormone secretion. Release of the glucose-regulating hormone insulin from pancreatic islet β cells is critical for whole-body metabolic homeostasis. Impaired insulin secretion appears early in the progression to type 2 diabetes (T2D). Key mechanisms that control the β-cell exocytotic response, mediating the long-known but little understood metabolic amplification of insulin secretion, are becoming clearer. Recent insights indicate a convergence of metabolism-driven signals, such as lipid-derived messengers and redox-dependent deSUMOylation, at the plasma membrane to augment Ca2+-dependent insulin exocytosis. These pathways have important implications for the metabolic control of hormone secretion, for the functional compensation that occurs in obesity, and for impaired insulin secretion in diabetes.
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Affiliation(s)
- Mourad Ferdaoussi
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
| | - Patrick E MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1.
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21
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Abstract
Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells target infected or transformed cells with perforin-containing cytotoxic granules through immune synapses, while platelets secrete several types of granules which contents are essential for thrombosis and hemostasis. Recent work has culminated in the notion that an exocytic SNARE complex, based on a very similar set of components, is primarily responsible for exocytosis of the diverse granules in these different cell types. Granule exocytosis is, in particular, uniquely dependent on the atypical Q-SNARE syntaxin 11, its interacting partners of the Sec/Munc (SM) family, and is regulated by Rab27a. Mutations in these exocytic components underlie disease manifestations of familial hemophagocytic lymphohistiocytosis (FHL) subtypes, characterized by hyperactivation of the immune system, as well as platelet granule secretion defects. Here we discuss the key discoveries that led to the converging notion of the syntaxin 11-based exocytosis machinery for cytotoxic granules and platelet-derived granules.
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Affiliation(s)
- Bor Luen Tang
- a Department of Biochemistry , Yong Loo Lin School of Medicine, National University of Singapore , Singapore and.,b NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , Singapore
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22
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Yong CSM, Westwood JA, Schröder J, Papenfuss AT, von Scheidt B, Moeller M, Devaud C, Darcy PK, Kershaw MH. Expression of a Chimeric Antigen Receptor in Multiple Leukocyte Lineages in Transgenic Mice. PLoS One 2015; 10:e0140543. [PMID: 26505904 PMCID: PMC4624721 DOI: 10.1371/journal.pone.0140543] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/24/2015] [Indexed: 12/25/2022] Open
Abstract
Genetically modified CD8+ T lymphocytes have shown significant anti-tumor effects in the adoptive immunotherapy of cancer, with recent studies highlighting a potential role for a combination of other immune subsets to enhance these results. However, limitations in present genetic modification techniques impose difficulties in our ability to fully explore the potential of various T cell subsets and assess the potential of other leukocytes armed with chimeric antigen receptors (CARs). To address this issue, we generated a transgenic mouse model using a pan-hematopoietic promoter (vav) to drive the expression of a CAR specific for a tumor antigen. Here we present a characterization of the immune cell compartment in two unique vav-CAR transgenic mice models, Founder 9 (F9) and Founder 38 (F38). We demonstrate the vav promoter is indeed capable of driving the expression of a CAR in cells from both myeloid and lymphoid lineage, however the highest level of expression was observed in T lymphocytes from F38 mice. Lymphoid organs in vav-CAR mice were smaller and had reduced cell numbers compared to the wild type (WT) controls. Furthermore, the immune composition of F9 mice differed greatly with a significant reduction in lymphocytes found in the thymus, lymph node and spleen of these mice. To gain insight into the altered immune phenotype of F9 mice, we determined the chromosomal integration site of the transgene in both mouse strains using whole genome sequencing (WGS). We demonstrated that compared to the 7 copies found in F38 mice, F9 mice harbored almost 270 copies. These novel vav-CAR models provide a ready source of CAR expressing myeloid and lymphoid cells and will aid in facilitating future experiments to delineate the role for other leukocytes for adoptive immunotherapy against cancer.
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Affiliation(s)
- Carmen S. M. Yong
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jennifer A. Westwood
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jan Schröder
- Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
- Bioinformatics and Cancer Genomics, Peter MacCallum Cancer Centre, East Melbourne, Victoria, 3002, Australia
- Department of Computing and Information Systems, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Anthony T. Papenfuss
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
- Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
- Bioinformatics and Cancer Genomics, Peter MacCallum Cancer Centre, East Melbourne, Victoria, 3002, Australia
- Department of Computing and Information Systems, The University of Melbourne, Parkville, Victoria, 3010, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Bianca von Scheidt
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Maria Moeller
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Christel Devaud
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
- INSERM U1043 Centre de Physiopathologie Toulouse Purpan (CPTP), Toulouse, France
- * E-mail: (MK); (PD); (CD)
| | - Phillip K. Darcy
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
- Department of Immunology, Monash University, Prahran Victoria 3181 Australia
- * E-mail: (MK); (PD); (CD)
| | - Michael H. Kershaw
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria 3010, Australia
- Department of Immunology, Monash University, Prahran Victoria 3181 Australia
- * E-mail: (MK); (PD); (CD)
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Watson K, Rossi G, Temple B, Brennwald P. Structural basis for recognition of the Sec4 Rab GTPase by its effector, the Lgl/tomosyn homologue, Sro7. Mol Biol Cell 2015. [PMID: 26202462 PMCID: PMC4569318 DOI: 10.1091/mbc.e15-04-0228] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Members of the tomosyn/Lgl/Sro7 family play important roles in vesicle trafficking and cell polarity in eukaryotic cells. The yeast homologue, Sro7, is believed to act as a downstream effector of the Sec4 Rab GTPase to promote soluble N-ethylmaleimide-sensitive factor adaptor protein receptor (SNARE) assembly during Golgi-to-cell surface vesicle transport. Here we describe the identification of a Sec4 binding site on the surface of Sro7 that is contained within a cleft created by the junction of two adjacent β-propellers that form the core structure of Sro7. Computational docking experiments suggested four models for interaction of GTP-Sec4 with the Sro7 binding cleft. Further mutational and biochemical analyses confirmed that only one of the four docking arrangements is perfectly consistent with our genetic and biochemical interaction data. Close examination of this docking model suggests a structural basis for the high substrate and nucleotide selectivity in effector binding by Sro7. Finally, analysis of the surface variation within the homologous interaction site on tomosyn-1 and Lgl-1 structural models suggests a possible conserved Rab GTPase effector function in tomosyn vertebrate homologues.
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Affiliation(s)
- Kelly Watson
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599 Graduate Program in Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Guendalina Rossi
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Brenda Temple
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, NC 27599 R. L. Juliano Structural Bioinformatics Core, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Patrick Brennwald
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599 Graduate Program in Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
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24
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A Combined Optogenetic-Knockdown Strategy Reveals a Major Role of Tomosyn in Mossy Fiber Synaptic Plasticity. Cell Rep 2015; 12:396-404. [PMID: 26166572 DOI: 10.1016/j.celrep.2015.06.037] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 05/21/2015] [Accepted: 06/09/2015] [Indexed: 11/23/2022] Open
Abstract
Neurotransmitter release probability (P(r)) largely determines the dynamic properties of synapses. While much is known about the role of presynaptic proteins in transmitter release, their specific contribution to synaptic plasticity is unclear. One such protein, tomosyn, is believed to reduce P(r) by interfering with the SNARE complex formation. Tomosyn is enriched at hippocampal mossy fiber-to-CA3 pyramidal cell synapses (MF-CA3), which characteristically exhibit low P(r), strong synaptic facilitation, and pre-synaptic protein kinase A (PKA)-dependent long-term potentiation (LTP). To evaluate tomosyn's role in MF-CA3 function, we used a combined knockdown (KD)-optogenetic strategy whereby presynaptic neurons with reduced tomosyn levels were selectively activated by light. Using this approach in mouse hippocampal slices, we found that facilitation, LTP, and PKA-induced potentiation were significantly impaired at tomosyn-deficient synapses. These findings not only indicate that tomosyn is a key regulator of MF-CA3 plasticity but also highlight the power of a combined KD-optogenetic approach to determine the role of presynaptic proteins.
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25
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Kumar R, Corbett MA, Smith NJC, Jolly LA, Tan C, Keating DJ, Duffield MD, Utsumi T, Moriya K, Smith KR, Hoischen A, Abbott K, Harbord MG, Compton AG, Woenig JA, Arts P, Kwint M, Wieskamp N, Gijsen S, Veltman JA, Bahlo M, Gleeson JG, Haan E, Gecz J. Homozygous mutation of STXBP5L explains an autosomal recessive infantile-onset neurodegenerative disorder. Hum Mol Genet 2014; 24:2000-10. [DOI: 10.1093/hmg/ddu614] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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26
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Henley JM, Craig TJ, Wilkinson KA. Neuronal SUMOylation: mechanisms, physiology, and roles in neuronal dysfunction. Physiol Rev 2014; 94:1249-85. [PMID: 25287864 PMCID: PMC4187031 DOI: 10.1152/physrev.00008.2014] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Protein SUMOylation is a critically important posttranslational protein modification that participates in nearly all aspects of cellular physiology. In the nearly 20 years since its discovery, SUMOylation has emerged as a major regulator of nuclear function, and more recently, it has become clear that SUMOylation has key roles in the regulation of protein trafficking and function outside of the nucleus. In neurons, SUMOylation participates in cellular processes ranging from neuronal differentiation and control of synapse formation to regulation of synaptic transmission and cell survival. It is a highly dynamic and usually transient modification that enhances or hinders interactions between proteins, and its consequences are extremely diverse. Hundreds of different proteins are SUMO substrates, and dysfunction of protein SUMOylation is implicated in a many different diseases. Here we briefly outline core aspects of the SUMO system and provide a detailed overview of the current understanding of the roles of SUMOylation in healthy and diseased neurons.
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Affiliation(s)
- Jeremy M Henley
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Tim J Craig
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Kevin A Wilkinson
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
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27
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Zhu Q, Yamakuchi M, Ture S, de la Luz Garcia-Hernandez M, Ko KA, Modjeski KL, LoMonaco MB, Johnson AD, O'Donnell CJ, Takai Y, Morrell CN, Lowenstein CJ. Syntaxin-binding protein STXBP5 inhibits endothelial exocytosis and promotes platelet secretion. J Clin Invest 2014; 124:4503-16. [PMID: 25244095 DOI: 10.1172/jci71245] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 07/24/2014] [Indexed: 01/25/2023] Open
Abstract
In humans, vWF levels predict the risk of myocardial infarction and thrombosis; however, the factors that influence vWF levels are not completely understood. Recent genome-wide association studies (GWAS) have identified syntaxin-binding protein 5 (STXBP5) as a candidate gene linked to changes in vWF plasma levels, though the functional relationship between STXBP5 and vWF is unknown. We hypothesized that STXBP5 inhibits endothelial cell exocytosis. We found that STXBP5 is expressed in human endothelial cells and colocalizes with and interacts with syntaxin 4. In human endothelial cells reduction of STXBP5 increased exocytosis of vWF and P-selectin. Mice lacking Stxbp5 had higher levels of vWF in the plasma, increased P-selectin translocation, and more platelet-endothelial interactions, which suggests that STXBP5 inhibits endothelial exocytosis. However, Stxbp5 KO mice also displayed hemostasis defects, including prolonged tail bleeding times and impaired mesenteric arteriole and carotid artery thrombosis. Furthermore, platelets from Stxbp5 KO mice had defects in platelet secretion and activation; thus, STXBP5 inhibits endothelial exocytosis but promotes platelet secretion. Our study reveals a vascular function for STXBP5, validates the functional relevance of a candidate gene identified by GWAS, and suggests that variation within STXBP5 is a genetic risk for venous thromboembolic disease.
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28
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Yu H, Rathore SS, Gulbranson DR, Shen J. The N- and C-terminal domains of tomosyn play distinct roles in soluble N-ethylmaleimide-sensitive factor attachment protein receptor binding and fusion regulation. J Biol Chem 2014; 289:25571-80. [PMID: 25063806 DOI: 10.1074/jbc.m114.591487] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tomosyn negatively regulates SNARE-dependent exocytic pathways including insulin secretion, GLUT4 exocytosis, and neurotransmitter release. The molecular mechanism of tomosyn, however, has not been fully elucidated. Here, we reconstituted SNARE-dependent fusion reactions in vitro to recapitulate the tomosyn-regulated exocytic pathways. We then expressed and purified active full-length tomosyn and examined how it regulates the reconstituted SNARE-dependent fusion reactions. Using these defined fusion assays, we demonstrated that tomosyn negatively regulates SNARE-mediated membrane fusion by inhibiting the assembly of the ternary SNARE complex. Tomosyn recognizes the t-SNARE complex and prevents its pairing with the v-SNARE, therefore arresting the fusion reaction at a pre-docking stage. The inhibitory function of tomosyn is mediated by its C-terminal domain (CTD) that contains an R-SNARE-like motif, confirming previous studies carried out using truncated tomosyn fragments. Interestingly, the N-terminal domain (NTD) of tomosyn is critical (but not sufficient) to the binding of tomosyn to the syntaxin monomer, indicating that full-length tomosyn possesses unique features not found in the widely studied CTD fragment. Finally, we showed that the inhibitory function of tomosyn is dominant over the stimulatory activity of the Sec1/Munc18 protein in fusion. We suggest that tomosyn uses its CTD to arrest SNARE-dependent fusion reactions, whereas its NTD is required for the recruitment of tomosyn to vesicle fusion sites through syntaxin interaction.
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Affiliation(s)
- Haijia Yu
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Shailendra S Rathore
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Daniel R Gulbranson
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Jingshi Shen
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309
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29
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Bhatnagar S, Soni MS, Wrighton LS, Hebert AS, Zhou AS, Paul PK, Gregg T, Rabaglia ME, Keller MP, Coon JJ, Attie AD. Phosphorylation and degradation of tomosyn-2 de-represses insulin secretion. J Biol Chem 2014; 289:25276-86. [PMID: 25002582 DOI: 10.1074/jbc.m114.575985] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The abundance and functional activity of proteins involved in the formation of the SNARE complex are tightly regulated for efficient exocytosis. Tomosyn proteins are negative regulators of exocytosis. Tomosyn causes an attenuation of insulin secretion by limiting the formation of the SNARE complex. We hypothesized that glucose-dependent stimulation of insulin secretion from β-cells must involve reversing the inhibitory action of tomosyn. Here, we show that glucose increases tomosyn protein turnover. Within 1 h of exposure to 15 mM glucose, ~50% of tomosyn was degraded. The degradation of tomosyn in response to high glucose was blocked by inhibitors of the proteasomal pathway. Using (32)P labeling and mass spectrometry, we showed that tomosyn-2 is phosphorylated in response to high glucose, phorbol esters, and analogs of cAMP, all key insulin secretagogues. We identified 11 phosphorylation sites in tomosyn-2. Site-directed mutagenesis was used to generate phosphomimetic (Ser → Asp) and loss-of-function (Ser → Ala) mutants. The Ser → Asp mutant had enhanced protein turnover compared with the Ser → Ala mutant and wild type tomosyn-2. Additionally, the Ser → Asp tomosyn-2 mutant was ineffective at inhibiting insulin secretion. Using a proteomic screen for tomosyn-2-binding proteins, we identified Hrd-1, an E3-ubiquitin ligase. We showed that tomosyn-2 ubiquitination is increased by Hrd-1, and knockdown of Hrd-1 by short hairpin RNA resulted in increased abundance in tomosyn-2 protein levels. Taken together, our results reveal a mechanism by which enhanced phosphorylation of a negative regulator of secretion, tomosyn-2, in response to insulin secretagogues targets it to degradation by the Hrd-1 E3-ubiquitin ligase.
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Affiliation(s)
| | | | | | - Alexander S Hebert
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | | | | | | | | | | | - Joshua J Coon
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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30
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Bielopolski N, Lam AD, Bar-On D, Sauer M, Stuenkel EL, Ashery U. Differential interaction of tomosyn with syntaxin and SNAP25 depends on domains in the WD40 β-propeller core and determines its inhibitory activity. J Biol Chem 2014; 289:17087-99. [PMID: 24782308 DOI: 10.1074/jbc.m113.515296] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal exocytosis depends on efficient formation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes and is regulated by tomosyn, a SNARE-binding protein. To gain new information about tomosyn's activity, we characterized its mobility and organization on the plasma membrane (PM) in relation to other SNARE proteins and inhibition of exocytosis. By using direct stochastic optical reconstruction microscopy (dSTORM), we found tomosyn to be organized in small clusters adjacent to syntaxin clusters. In addition, we show that tomosyn is present in both syntaxin-tomosyn complexes and syntaxin-SNAP25-tomosyn complexes. Tomosyn mutants that lack residues 537-578 or 897-917 from its β-propeller core diffused faster on the PM and exhibited reduced binding to SNAP25, suggesting that these mutants shift the equilibrium between tomosyn-syntaxin-SNAP25 complexes on the PM to tomosyn-syntaxin complexes. As these deletion mutants impose less inhibition on exocytosis, we suggest that tomosyn inhibition is mediated via tomosyn-syntaxin-SNAP25 complexes and not tomosyn-syntaxin complexes. These findings characterize, for the first time, tomosyn's dynamics at the PM and its relation to its inhibition of exocytosis.
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Affiliation(s)
- Noa Bielopolski
- From the Department of Neurobiology, Life Sciences Faculty, and
| | - Alice D Lam
- the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Dana Bar-On
- From the Department of Neurobiology, Life Sciences Faculty, and Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Markus Sauer
- the Department of Biotechnology and Biophysics, Julius Maximilians University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Edward L Stuenkel
- the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Uri Ashery
- From the Department of Neurobiology, Life Sciences Faculty, and Sagol School of Neuroscience, Tel Aviv University, 69978 Tel Aviv, Israel,
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31
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Tomosyn-2 is required for normal motor performance in mice and sustains neurotransmission at motor endplates. Brain Struct Funct 2014; 220:1971-82. [DOI: 10.1007/s00429-014-0766-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Accepted: 03/26/2014] [Indexed: 11/25/2022]
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32
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Geerts CJ, Jacobsen L, van de Bospoort R, Verhage M, Groffen AJA. Tomosyn interacts with the SUMO E3 ligase PIASγ. PLoS One 2014; 9:e91697. [PMID: 24614299 PMCID: PMC3948876 DOI: 10.1371/journal.pone.0091697] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 02/14/2014] [Indexed: 11/23/2022] Open
Abstract
Protein modification by Small Ubiquitin-like MOdifier (SUMO) entities is involved in a number of neuronal functions, including synaptogenesis and synaptic plasticity. Tomosyn-1 (syntaxin-binding protein 5; STXPB5) binds to t-SNARE (Soluble NSF Attachment Protein Receptor) proteins to regulate neurotransmission and is one of the few neuronal SUMO substrate proteins identified. Here we used yeast two-hybrid screening to show that tomosyn-1 interacts with the SUMO E3 ligase PIASγ (Protein Inhibitor of Activated STAT; PIAS4 or ZMIZ6). This novel interaction involved the C-terminus of tomosyn-1 and the N-terminus of PIASγ. It was confirmed by two-way immunoprecipitation experiments using the full-length proteins expressed in HEK293T cells. Tomosyn-1 was preferentially modified by the SUMO-2/3 isoform. PIASγ-dependent modification of tomosyn-1 with SUMO-2/3 presents a novel mechanism to adapt secretory strength to the dynamic synaptic environment.
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Affiliation(s)
- Cornelia J. Geerts
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, Netherlands
| | - Linda Jacobsen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, Netherlands
| | - Rhea van de Bospoort
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, Netherlands
| | - Alexander J. A. Groffen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, Netherlands
- * E-mail:
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33
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Short AD, Boag A, Catchpole B, Kennedy LJ, Massey J, Rothwell S, Husebye E, Ollier B. A candidate gene analysis of canine hypoadrenocorticism in 3 dog breeds. J Hered 2013; 104:807-20. [PMID: 23997205 DOI: 10.1093/jhered/est051] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Canine hypoadrenocorticism is believed to be an immune-related condition. It is rare in the overall dog population but shows a breed-related predisposition with Standard poodles and Portuguese water dogs having a greater prevalence of the condition. It shares many similarities with human primary adrenal insufficiency and is believed to be a naturally occurring, spontaneous model for the human condition. Short haplotype blocks and low levels of linkage disequilibrium in the human genome mean that the identification of genetic contributors to the condition requires large sample numbers. Pedigree dogs have high linkage disequilibrium and long haplotypes within a breed, increasing the potential of identifying novel genes that contribute to canine genetic disease. We investigated 222 SNPs from 42 genes that have been associated or may be implicated in human Addison's disease. We conducted case-control analyses in 3 pedigree dog breeds (Labrador retriever: affected n = 30, unaffected = 76; Cocker Spaniel: affected n = 19, unaffected = 53; Springer spaniel: affected n = 26, unaffected = 46) and identified 8 associated alleles in genes COL4A4, OSBPL9, CTLA4, PTPN22, and STXBP5 in 3 pedigree breeds. Association with immune response genes PTPN22 and CTLA4 in certain breeds suggests an underlying immunopathogenesis of the disease. These results suggest that canine hypoadrenocorticism could be a useful model for studying comparative genetics relevant to human Addison's disease.
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Affiliation(s)
- Andrea D Short
- the Centre for Integrated Genomic Medical Research, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
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Identification of rare recurrent copy number variants in high-risk autism families and their prevalence in a large ASD population. PLoS One 2013; 8:e52239. [PMID: 23341896 PMCID: PMC3544904 DOI: 10.1371/journal.pone.0052239] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 11/09/2012] [Indexed: 11/29/2022] Open
Abstract
Structural variation is thought to play a major etiological role in the development of autism spectrum disorders (ASDs), and numerous studies documenting the relevance of copy number variants (CNVs) in ASD have been published since 2006. To determine if large ASD families harbor high-impact CNVs that may have broader impact in the general ASD population, we used the Affymetrix genome-wide human SNP array 6.0 to identify 153 putative autism-specific CNVs present in 55 individuals with ASD from 9 multiplex ASD pedigrees. To evaluate the actual prevalence of these CNVs as well as 185 CNVs reportedly associated with ASD from published studies many of which are insufficiently powered, we designed a custom Illumina array and used it to interrogate these CNVs in 3,000 ASD cases and 6,000 controls. Additional single nucleotide variants (SNVs) on the array identified 25 CNVs that we did not detect in our family studies at the standard SNP array resolution. After molecular validation, our results demonstrated that 15 CNVs identified in high-risk ASD families also were found in two or more ASD cases with odds ratios greater than 2.0, strengthening their support as ASD risk variants. In addition, of the 25 CNVs identified using SNV probes on our custom array, 9 also had odds ratios greater than 2.0, suggesting that these CNVs also are ASD risk variants. Eighteen of the validated CNVs have not been reported previously in individuals with ASD and three have only been observed once. Finally, we confirmed the association of 31 of 185 published ASD-associated CNVs in our dataset with odds ratios greater than 2.0, suggesting they may be of clinical relevance in the evaluation of children with ASDs. Taken together, these data provide strong support for the existence and application of high-impact CNVs in the clinical genetic evaluation of children with ASD.
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35
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Muppirala M, Gupta V, Swarup G. Tyrosine phosphorylation of a SNARE protein, syntaxin 17: implications for membrane trafficking in the early secretory pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:2109-19. [PMID: 23006999 DOI: 10.1016/j.bbamcr.2012.09.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 09/13/2012] [Indexed: 10/27/2022]
Abstract
The T-cell protein tyrosine phosphatase is expressed as two splice variants - TC45, a nuclear protein, and TC48, which is localized predominantly in the ER (endoplasmic reticulum). Yeast two-hybrid screening revealed direct interaction of TC48 with Syntaxin17, a SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein localized predominantly in the ER and to some extent in the ER-Golgi intermediate compartment. Syntaxin 17 did not interact with TC45. C-terminal 40 amino acids of TC48 were sufficient for interaction with syntaxin 17. Overexpressed syntaxin 17 was phosphorylated at tyrosine upon pervanadate treatment (a tyrosine phosphatase inhibitor/tyrosine kinase activator) of COS-1 cells. Mutational analysis identified Tyr156 in the cytoplasmic domain as the major site of phosphorylation. Endogenous syntaxin 17 was phosphorylated by pervanadate treatment in CHO and MIN6 cells but was not phosphorylated in a variety of other cell lines tested. c-Abl was identified as one of the kinases, which phosphorylates syntaxin 17 in MIN6 cells. Phosphorylation of endogenous and overexpressed syntaxin 17 was reduced in the presence of IGF receptor and EGF receptor kinase inhibitors. Serum depletion reduced pervanadate-induced phosphorylation of endogenous syntaxin 17. TC48 coexpression reduced phosphorylation of syntaxin 17 by pervanadate and purified TC48 directly dephosphorylated syntaxin 17. β-COP dispersal by overexpressed syntaxin 17 was reduced after pervanadate-induced phosphorylation. A phospho-mimicking mutant (Y156E) of syntaxin 17 showed reduced interaction with COPI vesicles. These results suggest that tyrosine phosphorylation of syntaxin 17 is likely to have a role in regulating syntaxin 17 dependent membrane trafficking in the early secretory pathway.
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Affiliation(s)
- Madhavi Muppirala
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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36
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Craig TJ, Henley JM. Protein SUMOylation in spine structure and function. Curr Opin Neurobiol 2012; 22:480-7. [PMID: 22054923 PMCID: PMC3379963 DOI: 10.1016/j.conb.2011.10.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 10/18/2011] [Accepted: 10/18/2011] [Indexed: 11/18/2022]
Abstract
The active regulation of spine structure and function is of fundamental importance for information storage in the brain. Many proteins involved in spine development and activity-dependent remodelling are potential or validated substrates for modification by the Small Ubiquitin-like Modifier (SUMO). The functional consequences of neuronal protein SUMOylation appear diverse and, in many cases, have not yet been determined. However, for several proteins SUMOylation has been shown to be a key regulator, which has a profound impact on spine dynamics and protein trafficking and function. Here we provide an overview of neuronal SUMOylation and discuss how greater understanding of this relatively recently discovered posttranslational modification will provide insight into the complexity of protein interactions that control synaptic activity and dysfunction.
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Affiliation(s)
- Tim J Craig
- MRC Centre for Synaptic Plasticity, School of Biochemistry Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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