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Nguyen DPQ, Pham S, Jallow AW, Ho NT, Le B, Quang HT, Lin YF, Lin YF. Multiple Transcriptomic Analyses Explore Potential Synaptic Biomarker Rabphilin-3A for Alzheimer's Disease. Sci Rep 2024; 14:18717. [PMID: 39134564 PMCID: PMC11319786 DOI: 10.1038/s41598-024-66693-8] [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: 04/01/2024] [Accepted: 07/03/2024] [Indexed: 08/15/2024] Open
Abstract
Alzheimer's disease (AD) is a prevalent neurodegenerative disorder afflicting the elderly population worldwide. The identification of potential gene candidates for AD holds promises for diagnostic biomarkers and therapeutic targets. Employing a comprehensive strategy, this study integrated transcriptomic data from diverse data sources, including microarray and single-cell datasets from blood and tissue samples, enabling a detailed exploration of gene expression dynamics. Through this thorough investigation, 19 notable candidate genes were found with consistent expression changes across both blood and tissue datasets, suggesting their potential as biomarkers for AD. In addition, single cell sequencing analysis further highlighted their specific expression in excitatory and inhibitory neurons, the primary functional units in the brain, underscoring their relevance to AD pathology. Moreover, the functional enrichment analysis revealed that three of the candidate genes were downregulated in synaptic signaling pathway. Further validation experiments significantly showed reduced levels of rabphilin-3A (RPH3A) in 3xTg-AD model mice, implying its role in disease pathogenesis. Given its role in neurotransmitter exocytosis and synaptic function, further investigation into RPH3A and its interactions with neurotrophic proteins may provide valuable insights into the complex molecular mechanisms underlying synaptic dysfunction in AD.
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Affiliation(s)
- Doan Phuong Quy Nguyen
- Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, No. 301, Yuantong Rd., Zhonghe Dist., New Taipei City, 235, Taiwan
- Institute of Biomedicine, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam
| | - Son Pham
- BioTuring Inc., San Diego, CA, 92121, USA
| | - Amadou Wurry Jallow
- Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, No. 301, Yuantong Rd., Zhonghe Dist., New Taipei City, 235, Taiwan
| | | | - Bao Le
- Faculty of Pharmacy, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| | - Hung Tran Quang
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, New Taipei City, 235, Taiwan
| | - Yi-Fang Lin
- Department of Laboratory Medicine, Taipei Medical University-Shuang Ho Hospital, New Taipei City, 235, Taiwan
| | - Yung-Feng Lin
- Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, No. 301, Yuantong Rd., Zhonghe Dist., New Taipei City, 235, Taiwan.
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, New Taipei City, 235, Taiwan.
- Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei City, 110, Taiwan.
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Yang L, Wei M, Wang Y, Zhang J, Liu S, Liu M, Wang S, Li K, Dong Z, Zhang C. Rabphilin-3A undergoes phase separation to regulate GluN2A mobility and surface clustering. Nat Commun 2023; 14:379. [PMID: 36693856 PMCID: PMC9873702 DOI: 10.1038/s41467-023-36046-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 01/13/2023] [Indexed: 01/25/2023] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs) are essential for excitatory neurotransmission and synaptic plasticity. GluN2A and GluN2B, two predominant Glu2N subunits of NMDARs in the hippocampus and the cortex, display distinct clustered distribution patterns and mobility at synaptic and extrasynaptic sites. However, how GluN2A clusters are specifically organized and stabilized remains poorly understood. Here, we found that the previously reported GluN2A-specific binding partner Rabphilin-3A (Rph3A) has the ability to undergo phase separation, which relies on arginine residues in its N-terminal domain. Rph3A phase separation promotes GluN2A clustering by binding GluN2A's C-terminal domain. A complex formed by Rph3A, GluN2A, and the scaffolding protein PSD95 promoted Rph3A phase separation. Disrupting Rph3A's phase separation suppressed the synaptic and extrasynaptic surface clustering, synaptic localization, stability, and synaptic response of GluN2A in hippocampal neurons. Together, our results reveal the critical role of Rph3A phase separation in determining the organization and stability of GluN2A in the neuronal surface.
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Affiliation(s)
- Lei Yang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Mengping Wei
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Yangzhen Wang
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jingtao Zhang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Sen Liu
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Mengna Liu
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Shanshan Wang
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Ke Li
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Zhaoqi Dong
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Chen Zhang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China. .,Chinese Institute for Brain Research, Beijing, 102206, China. .,State Key Laboratory of Translational Medicine and Innovative Drug Development, Nanjing, 210000, Jiangsu, China. .,Beijing Laboratory of Oral Health, Capital Medical University, Beijing, 100050, China.
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3
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Li T, Cheng Q, Wang S, Ma C. Rabphilin 3A binds the N-peptide of SNAP-25 to promote SNARE complex assembly in exocytosis. eLife 2022; 11:e79926. [PMID: 36173100 PMCID: PMC9522249 DOI: 10.7554/elife.79926] [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] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 09/13/2022] [Indexed: 11/13/2022] Open
Abstract
Exocytosis of secretory vesicles requires the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and small GTPase Rabs. As a Rab3/Rab27 effector protein on secretory vesicles, Rabphilin 3A was implicated to interact with SNAP-25 to regulate vesicle exocytosis in neurons and neuroendocrine cells, yet the underlying mechanism remains unclear. In this study, we have characterized the physiologically relevant binding sites between Rabphilin 3A and SNAP-25. We found that an intramolecular interplay between the N-terminal Rab-binding domain and C-terminal C2AB domain enables Rabphilin 3A to strongly bind the SNAP-25 N-peptide region via its C2B bottom α-helix. Disruption of this interaction significantly impaired docking and fusion of vesicles with the plasma membrane in rat PC12 cells. In addition, we found that this interaction allows Rabphilin 3A to accelerate SNARE complex assembly. Furthermore, we revealed that this interaction accelerates SNARE complex assembly via inducing a conformational switch from random coils to α-helical structure in the SNAP-25 SNARE motif. Altogether, our data suggest that the promotion of SNARE complex assembly by binding the C2B bottom α-helix of Rabphilin 3A to the N-peptide of SNAP-25 underlies a pre-fusion function of Rabphilin 3A in vesicle exocytosis.
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Affiliation(s)
- Tianzhi Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and TechnologyWuhanChina
| | - Qiqi Cheng
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and TechnologyWuhanChina
| | - Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and TechnologyWuhanChina
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and TechnologyWuhanChina
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4
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Sekine Y, Kannan R, Wang X, Strittmatter SM. Rabphilin3A reduces integrin-dependent growth cone signaling to restrict axon regeneration after trauma. Exp Neurol 2022; 353:114070. [PMID: 35398339 PMCID: PMC9555232 DOI: 10.1016/j.expneurol.2022.114070] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/09/2022] [Accepted: 04/04/2022] [Indexed: 01/03/2023]
Abstract
Neural repair after traumatic spinal cord injury depends upon the restoration of neural networks via axonal sprouting and regeneration. Our previous genome wide loss-of-function screen identified Rab GTPases as playing a prominent role in preventing successful axon sprouting and regeneration. Here, we searched for Rab27b interactors and identified Rabphilin3A as an effector within regenerating axons. Growth cone Rabphilin3a colocalized and physically associated with integrins at puncta in the proximal body of the axonal growth cone. In regenerating axons, loss of Rabphilin3a increased integrin enrichment in the growth cone periphery, enhanced focal adhesion kinase activation, increased F-actin-rich filopodial density and stimulated axon extension. Compared to wild type, mice lacking Rabphilin3a exhibited greater regeneration of retinal ganglion cell axons after optic nerve crush as well as greater corticospinal axon regeneration after complete thoracic spinal cord crush injury. After moderate spinal cord contusion injury, there was greater corticospinal regrowth in the absence of Rph3a. Thus, an endogenous Rab27b - Raphilin3a pathway limits integrin action in the growth cone, and deletion of this monomeric GTPase pathway permits reparative axon growth in the injured adult mammalian central nervous system.
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Affiliation(s)
- Yuichi Sekine
- Cellular Neuroscience, Neurodegeneration, Repair, Departments of Neurology and of Neuroscience, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Ramakrishnan Kannan
- Cellular Neuroscience, Neurodegeneration, Repair, Departments of Neurology and of Neuroscience, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Xingxing Wang
- Cellular Neuroscience, Neurodegeneration, Repair, Departments of Neurology and of Neuroscience, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Stephen M Strittmatter
- Cellular Neuroscience, Neurodegeneration, Repair, Departments of Neurology and of Neuroscience, Yale University School of Medicine, New Haven, CT 06536, USA.
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5
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Konopka A, Atkin JD. The Role of DNA Damage in Neural Plasticity in Physiology and Neurodegeneration. Front Cell Neurosci 2022; 16:836885. [PMID: 35813507 PMCID: PMC9259845 DOI: 10.3389/fncel.2022.836885] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 05/09/2022] [Indexed: 12/15/2022] Open
Abstract
Damage to DNA is generally considered to be a harmful process associated with aging and aging-related disorders such as neurodegenerative diseases that involve the selective death of specific groups of neurons. However, recent studies have provided evidence that DNA damage and its subsequent repair are important processes in the physiology and normal function of neurons. Neurons are unique cells that form new neural connections throughout life by growth and re-organisation in response to various stimuli. This “plasticity” is essential for cognitive processes such as learning and memory as well as brain development, sensorial training, and recovery from brain lesions. Interestingly, recent evidence has suggested that the formation of double strand breaks (DSBs) in DNA, the most toxic form of damage, is a physiological process that modifies gene expression during normal brain activity. Together with subsequent DNA repair, this is thought to underlie neural plasticity and thus control neuronal function. Interestingly, neurodegenerative diseases such as Alzheimer’s disease, amyotrophic lateral sclerosis, frontotemporal dementia, and Huntington’s disease, manifest by a decline in cognitive functions, which are governed by plasticity. This suggests that DNA damage and DNA repair processes that normally function in neural plasticity may contribute to neurodegeneration. In this review, we summarize current understanding about the relationship between DNA damage and neural plasticity in physiological conditions, as well as in the pathophysiology of neurodegenerative diseases.
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Affiliation(s)
- Anna Konopka
- Centre for Motor Neuron Disease Research, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, NSW, Australia
- *Correspondence: Anna Konopka
| | - Julie D. Atkin
- Centre for Motor Neuron Disease Research, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, NSW, Australia
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
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6
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Shahoha M, Cohen R, Ben-Simon Y, Ashery U. cAMP-Dependent Synaptic Plasticity at the Hippocampal Mossy Fiber Terminal. Front Synaptic Neurosci 2022; 14:861215. [PMID: 35444523 PMCID: PMC9013808 DOI: 10.3389/fnsyn.2022.861215] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/23/2022] [Indexed: 11/24/2022] Open
Abstract
Cyclic adenosine monophosphate (cAMP) is a crucial second messenger involved in both pre- and postsynaptic plasticity in many neuronal types across species. In the hippocampal mossy fiber (MF) synapse, cAMP mediates presynaptic long-term potentiation and depression. The main cAMP-dependent signaling pathway linked to MF synaptic plasticity acts via the activation of the protein kinase A (PKA) molecular cascade. Accordingly, various downstream putative synaptic PKA target proteins have been linked to cAMP-dependent MF synaptic plasticity, such as synapsin, rabphilin, synaptotagmin-12, RIM1a, tomosyn, and P/Q-type calcium channels. Regulating the expression of some of these proteins alters synaptic release probability and calcium channel clustering, resulting in short- and long-term changes to synaptic efficacy. However, despite decades of research, the exact molecular mechanisms by which cAMP and PKA exert their influences in MF terminals remain largely unknown. Here, we review current knowledge of different cAMP catalysts and potential downstream PKA-dependent molecular cascades, in addition to non-canonical cAMP-dependent but PKA-independent cascades, which might serve as alternative, compensatory or competing pathways to the canonical PKA cascade. Since several other central synapses share a similar form of presynaptic plasticity with the MF, a better description of the molecular mechanisms governing MF plasticity could be key to understanding the relationship between the transcriptional and computational levels across brain regions.
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Affiliation(s)
- Meishar Shahoha
- Faculty of Life Sciences, School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Ronni Cohen
- Faculty of Life Sciences, School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Yoav Ben-Simon
- Department of Neurophysiology, Vienna Medical University, Vienna, Austria
- *Correspondence: Yoav Ben-Simon,
| | - Uri Ashery
- Faculty of Life Sciences, School of Neurobiology, Biochemistry and Biophysics, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- Uri Ashery,
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7
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Studies on anti-rabphilin-3A antibodies in 15 consecutive patients presenting with central diabetes insipidus at a single referral center. Sci Rep 2022; 12:4440. [PMID: 35292721 PMCID: PMC8924241 DOI: 10.1038/s41598-022-08552-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 03/09/2022] [Indexed: 12/11/2022] Open
Abstract
Central diabetes insipidus (CDI) is a rare condition caused by various underlying diseases including inflammatory and autoimmune diseases, and neoplasms. Obtaining an accurate definitive diagnosis of the underlying cause of CDI is difficult. Recently, anti-rabphilin-3A antibodies were demonstrated to be a highly sensitive and specific marker of lymphocytic infundibuloneurohypophysitis (LINH). Here, we report a detailed case series, and evaluated the significance of anti-rabphilin-3A antibodies in differentiating the etiologies of CDI. A prospective analysis was conducted in 15 consecutive patients with CDI from 2013 to 2020 at a single referral center. Anti-rabphilin-3A antibodies were measured and the relationship between antibody positivity and the clinical/histopathological diagnoses was evaluated. Among 15 CDI patients, the positive anti-rabphilin-3A antibodies were found in 4 of 5 LINH cases, 3 of 4 lymphocytic panhypophysitis (LPH) cases, one of 2 sarcoidosis cases, and one intracranial germinoma case, respectively. Two Rathke cleft cyst cases and one craniopharyngioma case were negative. This is the first report of anti-rabphilin-3A antibodies positivity in CDI patients with biopsy-proven LPH. Measurement of anti-rabphilin-3A antibodies may be valuable for differentiating CDI etiologies.
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8
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Izumi T. In vivo Roles of Rab27 and Its Effectors in Exocytosis. Cell Struct Funct 2021; 46:79-94. [PMID: 34483204 PMCID: PMC10511049 DOI: 10.1247/csf.21043] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
The monomeric GTPase Rab27 regulates exocytosis of a broad range of vesicles in multicellular organisms. Several effectors bind GTP-bound Rab27a and/or Rab27b on secretory vesicles to execute a series of exocytic steps, such as vesicle maturation, movement along microtubules, anchoring within the peripheral F-actin network, and tethering to the plasma membrane, via interactions with specific proteins and membrane lipids in a local milieu. Although Rab27 effectors generally promote exocytosis, they can also temporarily restrict it when they are involved in the rate-limiting step. Genetic alterations in Rab27-related molecules cause discrete diseases manifesting pigment dilution and immunodeficiency, and can also affect common diseases such as diabetes and cancer in complex ways. Although the function and mechanism of action of these effectors have been explored, it is unclear how multiple effectors act in coordination within a cell to regulate the secretory process as a whole. It seems that Rab27 and various effectors constitutively reside on individual vesicles to perform consecutive exocytic steps. The present review describes the unique properties and in vivo roles of the Rab27 system, and the functional relationship among different effectors coexpressed in single cells, with pancreatic beta cells used as an example.Key words: membrane trafficking, regulated exocytosis, insulin granules, pancreatic beta cells.
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Affiliation(s)
- Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
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9
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Sticco MJ, Peña Palomino PA, Lukacsovich D, Thompson BL, Földy C, Ressl S, Martinelli DC. C1QL3 promotes cell-cell adhesion by mediating complex formation between ADGRB3/BAI3 and neuronal pentraxins. FASEB J 2021; 35:e21194. [PMID: 33337553 DOI: 10.1096/fj.202000351rr] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 10/28/2020] [Accepted: 10/30/2020] [Indexed: 11/11/2022]
Abstract
Synapses are the fundamental structural unit by which neurons communicate. An orchestra of proteins regulates diverse synaptic functions, including synapse formation, maintenance, and elimination-synapse homeostasis. Some proteins of the larger C1q super-family are synaptic organizers involved in crucial neuronal processes in various brain regions. C1Q-like (C1QL) proteins bind to the adhesion G protein-coupled receptor B3 (ADGRB3) and act at synapses in a subset of circuits. To investigate the hypothesis that the secreted C1QL proteins mediate tripartite trans-synaptic adhesion complexes, we conducted an in vivo interactome study and identified new binding candidates. We demonstrate that C1QL3 mediates a novel cell-cell adhesion complex involving ADGRB3 and two neuronal pentraxins, NPTX1 and NPTXR. Analysis of single-cell RNA-Seq data from the cerebral cortex shows that C1ql3, Nptx1, and Nptxr are highly co-expressed in the same excitatory neurons. Thus, our results suggest the possibility that in vivo the three co-expressed proteins are presynaptically secreted and form a complex capable of binding to postsynaptically localized ADGRB3, thereby creating a novel trans-synaptic adhesion complex. Identifying new binding partners for C1QL proteins and deciphering their underlying molecular principles will accelerate our understanding of their role in synapse organization.
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Affiliation(s)
- Matthew J Sticco
- Department of Neuroscience, University of Connecticut Health, Farmington, CT, USA
| | - Perla A Peña Palomino
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - David Lukacsovich
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich, Switzerland
| | - Brianna L Thompson
- Department of Neuroscience, University of Connecticut Health, Farmington, CT, USA
| | - Csaba Földy
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich, Switzerland
| | - Susanne Ressl
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Neuroscience, The University of Texas at Austin, Austin, TX, USA
| | - David C Martinelli
- Department of Neuroscience, University of Connecticut Health, Farmington, CT, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,The Connecticut Institute for the Brain and Cognitive Sciences (IBACS), Storrs, CT, USA
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10
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Maselli RA, Wei DT, Hodgson TS, Sampson JB, Vazquez J, Smith HL, Pytel P, Ferns M. Dominant and recessive congenital myasthenic syndromes caused by SYT2 mutations. Muscle Nerve 2021; 64:219-224. [PMID: 34037996 DOI: 10.1002/mus.27332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 05/14/2021] [Accepted: 05/19/2021] [Indexed: 01/11/2023]
Abstract
INTRODUCTION/AIMS We studied a patient with a congenital myasthenic syndrome (CMS) caused by a dominant mutation in the synaptotagmin 2 gene (SYT2) and compared the clinical features of this patient with those of a previously described patient with a recessive mutation in the same gene. METHODS We performed electrodiagnostic (EDX) studies, genetic studies, muscle biopsy, microelectrode recordings and electron microscopy (EM). RESULTS Both patients presented with muscle weakness and bulbar deficits, which were worse in the recessive form. EDX studies showed presynaptic failure, which was more prominent in the recessive form. Microelectrode studies in the dominant form showed a marked reduction of the quantal content, which increased linearly with higher frequencies of nerve stimulation. The MEPP frequencies were normal at rest but increased markedly with higher frequencies of nerve stimulation. The EM demonstrated overdeveloped postsynaptic folding, and abundant endosomes, multivesicular bodies and degenerative lamellar bodies inside small nerve terminals. DISCUSSION The recessive form of CMS caused by a SYT2 mutation showed far more severe clinical manifestations than the dominant form. The pathogenesis of the dominant form likely involves a dominant-negative effect due to disruption of the dual function of synaptotagmin as a Ca2+ -sensor and modulator of synaptic vesicle exocytosis.
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Affiliation(s)
- Ricardo A Maselli
- Department of Neurology, University of California Davis, Sacramento, California, USA
| | - David T Wei
- Department of Neurology, University of California Davis, Sacramento, California, USA
| | - Trent S Hodgson
- Kaiser Permanente Oakland Medical Center, Oakland, California, USA
| | - Jacinda B Sampson
- Department of Neurology, Stanford University, Palo Alto, California, USA
| | - Jessica Vazquez
- Department of Neurology, University of California Davis, Sacramento, California, USA
| | - Heather L Smith
- Department of Pathology, The University of Chicago, Chicago, Illinois, USA
| | - Peter Pytel
- Department of Pathology, The University of Chicago, Chicago, Illinois, USA
| | - Michael Ferns
- Department of Anesthesiology, University of California Davis, Davis, California, USA
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11
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Bourgeois-Jaarsma Q, Miaja Hernandez P, Groffen AJ. Ca 2+ sensor proteins in spontaneous release and synaptic plasticity: Limited contribution of Doc2c, rabphilin-3a and synaptotagmin 7 in hippocampal glutamatergic neurons. Mol Cell Neurosci 2021; 112:103613. [PMID: 33753311 DOI: 10.1016/j.mcn.2021.103613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 11/28/2022] Open
Abstract
Presynaptic neurotransmitter release is strictly regulated by SNARE proteins, Ca2+ and a number of Ca2+ sensors including synaptotagmins (Syts) and Double C2 domain proteins (Doc2s). More than seventy years after the original description of spontaneous release, the mechanism that regulates this process is still poorly understood. Syt-1, Syt7 and Doc2 proteins contribute predominantly, but not exclusively, to synchronous, asynchronous and spontaneous phases of release. The proteins share a conserved tandem C2 domain architecture, but are functionally diverse in their subcellular location, Ca2+-binding properties and protein interactions. In absence of Syt-1, Doc2a and -b, neurons still exhibit spontaneous vesicle fusion which remains Ca2+-sensitive, suggesting the existence of additional sensors. Here, we selected Doc2c, rabphilin-3a and Syt-7 as three potential Ca2+ sensors for their sequence homology with Syt-1 and Doc2b. We genetically ablated each candidate gene in absence of Doc2a and -b and investigated spontaneous and evoked release in glutamatergic hippocampal neurons, cultured either in networks or on microglial islands (autapses). The removal of Doc2c had no effect on spontaneous or evoked release. Syt-7 removal also did not affect spontaneous release, although it altered short-term plasticity by accentuating short-term depression. The removal of rabphilin caused an increased spontaneous release frequency in network cultures, an effect that was not observed in autapses. Taken together, we conclude that Doc2c and Syt-7 do not affect spontaneous release of glutamate in hippocampal neurons, while our results suggest a possible regulatory role of rabphilin-3a in neuronal networks. These findings importantly narrow down the repertoire of synaptic Ca2+ sensors that may be implicated in the spontaneous release of glutamate.
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Affiliation(s)
- Quentin Bourgeois-Jaarsma
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Pablo Miaja Hernandez
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Alexander J Groffen
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; Department of Clinical Genetics, VU Medical Center, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
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12
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Patel PA, Liang C, Arora A, Vijayan S, Ahuja S, Wagley PK, Settlage R, LaConte LEW, Goodkin HP, Lazar I, Srivastava S, Mukherjee K. Haploinsufficiency of X-linked intellectual disability gene CASK induces post-transcriptional changes in synaptic and cellular metabolic pathways. Exp Neurol 2020; 329:113319. [PMID: 32305418 DOI: 10.1016/j.expneurol.2020.113319] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 04/04/2020] [Accepted: 04/15/2020] [Indexed: 12/17/2022]
Abstract
Heterozygous mutations in the X-linked gene CASK are associated with intellectual disability, microcephaly, pontocerebellar hypoplasia, optic nerve hypoplasia and partially penetrant seizures in girls. The Cask+/- heterozygous knockout female mouse phenocopies the human disorder and exhibits postnatal microencephaly, cerebellar hypoplasia and optic nerve hypoplasia. It is not known if Cask+/- mice also display seizures, nor is known the molecular mechanism by which CASK haploinsufficiency produces the numerous documented phenotypes. 24-h video electroencephalography demonstrates that despite sporadic seizure activity, the overall electrographic patterns remain unaltered in Cask+/- mice. Additionally, seizure threshold to the commonly used kindling agent, pentylenetetrazol, remains unaltered in Cask+/- mice, indicating that even in mice the seizure phenotype is only partially penetrant and may have an indirect mechanism. RNA sequencing experiments on Cask+/- mouse brain uncovers a very limited number of changes, with most differences arising in the transcripts of extracellular matrix proteins and the transcripts of a group of nuclear proteins. In contrast to limited changes at the transcript level, quantitative whole-brain proteomics using iTRAQ quantitative mass-spectrometry reveals major changes in synaptic, metabolic/mitochondrial, cytoskeletal, and protein metabolic pathways. Unbiased protein-protein interaction mapping using affinity chromatography demonstrates that CASK may form complexes with proteins belonging to the same functional groups in which altered protein levels are observed. We discuss the mechanism of the observed changes in the context of known molecular function/s of CASK. Overall, our data indicate that the phenotypic spectrum of female Cask+/- mice includes sporadic seizures and thus closely parallels that of CASK haploinsufficient girls; the Cask+/- mouse is thus a face-validated model for CASK-related pathologies. We therefore surmise that CASK haploinsufficiency is likely to affect brain structure and function due to dysregulation of several cellular pathways including synaptic signaling and cellular metabolism.
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Affiliation(s)
- P A Patel
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States; Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, United States
| | - C Liang
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States
| | - A Arora
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States
| | - S Vijayan
- School of Neuroscience, Virginia Tech, Blacksburg, VA, United States
| | - S Ahuja
- Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - P K Wagley
- Neurology, University of Virginia, Charlottesville, VA, USA
| | - R Settlage
- Advanced Research Computing, Virginia Tech, Blacksburg, VA, United States
| | - L E W LaConte
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States
| | - H P Goodkin
- Neurology, University of Virginia, Charlottesville, VA, USA
| | - I Lazar
- Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - S Srivastava
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States
| | - K Mukherjee
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States; Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, United States; Department of Psychiatry and Behavioral Medicine, Virginia Tech Carilion School of Medicine, Roanoke, VA, United States.
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13
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Liu M, Jin HS, Park S. Protein and fat intake interacts with the haplotype of PTPN11_rs11066325, RPH3A_rs886477, and OAS3_rs2072134 to modulate serum HDL concentrations in middle-aged people. Clin Nutr 2020; 39:942-949. [PMID: 31006500 DOI: 10.1016/j.clnu.2019.03.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 03/25/2019] [Accepted: 03/26/2019] [Indexed: 12/14/2022]
Abstract
BACKGROUND & AIMS Low serum HDL cholesterol (HDL-C) concentration is a risk factor for cardiovascular diseases and it is influenced by genetic and environmental factors. We hypothesized that genetic variants that decrease serum HDL-C concentrations may interact with nutrient intakes in ways that increase or decrease the risk of cardiovascular disease. METHODS Candidate genetic variants that can lower serum HDL-C concentrations were explored by genome-wide association studies (GWAS), after adjusting for covariates, in the Ansan/Ansung cohort (n = 8842) from KoGES. The best genetic variants were selected and used to form a haplotype. According to the haplotype frequencies of SNPs, they were divided into major allele, heterozygote allele, and minor allele. The association of haplotype with serum HDL-C levels was determined using logistic regression after adjusting for confounding factors. Interaction of the haplotype with nutrient intake was also determined. RESULTS PTPN11_rs11066325, RPH3A_rs886477 and OAS3_rs2072134 were selected to modulate serum HDL-C levels from GWAS(P = 1.09E-09, 7.04E-10, and 1.27E-09, respectively). The adjusted odds ratios (ORs) for a decrease in serum HDL-C concentration in the minor-allele group of the haplotype were elevated by 1.534 fold, compared to the major-allele group of the haplotype. Furthermore, the adjusted ORs for serum LDL cholesterol and levels increased by 1.645 in the minor-alleles compared to the major-alleles of the haplotype without a significant change of serum cholesterol levels. Interestingly, the adjusted ORs for serum triglyceride were lower in the minor-alleles than in the major-alleles. The haplotype had a significant interaction with the intake of protein, fat, saturated fatty acids (SAF) and polyunsaturated fatty acids (PUFA; P < 0.05). In particular, the minor alleles of the haplotype decreased serum HDL-C levels compared to the major-alleles in the high intake of protein, fat, SFA, and PUFA, not in the low intake. CONCLUSIONS People carrying the minor-allele of haplotypes should avoid diets that are high in protein and fat, especially rich in SFA and PUFA.
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Affiliation(s)
- Meiling Liu
- Dept. of Food and Nutrition, Institue of Basic Science, Obesity/Diabetes Research Center, Hoseo University, Asan, Chungnam, 31499, South Korea
| | - Hyun Seok Jin
- Department of Biomedical Laboratory Science, College of Life and Health Sciences, Hoseo University, Asan, Chungnam, 31499, South Korea
| | - Sunmin Park
- Dept. of Food and Nutrition, Institue of Basic Science, Obesity/Diabetes Research Center, Hoseo University, Asan, Chungnam, 31499, South Korea.
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14
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Maglione M, Kochlamazashvili G, Eisenberg T, Rácz B, Michael E, Toppe D, Stumpf A, Wirth A, Zeug A, Müller FE, Moreno-Velasquez L, Sammons RP, Hofer SJ, Madeo F, Maritzen T, Maier N, Ponimaskin E, Schmitz D, Haucke V, Sigrist SJ. Spermidine protects from age-related synaptic alterations at hippocampal mossy fiber-CA3 synapses. Sci Rep 2019; 9:19616. [PMID: 31873156 PMCID: PMC6927957 DOI: 10.1038/s41598-019-56133-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 12/06/2019] [Indexed: 12/15/2022] Open
Abstract
Aging is associated with functional alterations of synapses thought to contribute to age-dependent memory impairment (AMI). While therapeutic avenues to protect from AMI are largely elusive, supplementation of spermidine, a polyamine normally declining with age, has been shown to restore defective proteostasis and to protect from AMI in Drosophila. Here we demonstrate that dietary spermidine protects from age-related synaptic alterations at hippocampal mossy fiber (MF)-CA3 synapses and prevents the aging-induced loss of neuronal mitochondria. Dietary spermidine rescued age-dependent decreases in synaptic vesicle density and largely restored defective presynaptic MF-CA3 long-term potentiation (LTP) at MF-CA3 synapses (MF-CA3) in aged animals. In contrast, spermidine failed to protect CA3-CA1 hippocampal synapses characterized by postsynaptic LTP from age-related changes in function and morphology. Our data demonstrate that dietary spermidine attenuates age-associated deterioration of MF-CA3 synaptic transmission and plasticity. These findings provide a physiological and molecular basis for the future therapeutic usage of spermidine.
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Affiliation(s)
- Marta Maglione
- Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195, Berlin, Germany
- Department of Molecular Pharmacology and Cell Biology, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Gaga Kochlamazashvili
- Department of Molecular Pharmacology and Cell Biology, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010, Graz, Austria
- BioTechMed-Graz, 8010, Graz, Austria
| | - Bence Rácz
- Department of Anatomy and Histology, University of Veterinary Medicine Budapest, 1078, Budapest, Hungary
| | - Eva Michael
- Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195, Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - David Toppe
- Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195, Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Alexander Stumpf
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany
| | - Alexander Wirth
- Cellular Neurophysiology, Hannover Medical School, 30625, Hannover, Germany
| | - André Zeug
- Cellular Neurophysiology, Hannover Medical School, 30625, Hannover, Germany
| | - Franziska E Müller
- Cellular Neurophysiology, Hannover Medical School, 30625, Hannover, Germany
| | - Laura Moreno-Velasquez
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany
| | - Rosanna P Sammons
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany
| | - Sebastian J Hofer
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010, Graz, Austria
- BioTechMed-Graz, 8010, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010, Graz, Austria
- BioTechMed-Graz, 8010, Graz, Austria
| | - Tanja Maritzen
- Department of Molecular Pharmacology and Cell Biology, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Nikolaus Maier
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany
| | - Evgeni Ponimaskin
- Cellular Neurophysiology, Hannover Medical School, 30625, Hannover, Germany
| | - Dietmar Schmitz
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany
| | - Volker Haucke
- Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195, Berlin, Germany.
- Department of Molecular Pharmacology and Cell Biology, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.
| | - Stephan J Sigrist
- Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195, Berlin, Germany.
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.
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15
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Furber KL, Backlund PS, Yergey AL, Coorssen JR. Unbiased Thiol-Labeling and Top-Down Proteomic Analyses Implicate Multiple Proteins in the Late Steps of Regulated Secretion. Proteomes 2019; 7:proteomes7040034. [PMID: 31569819 PMCID: PMC6958363 DOI: 10.3390/proteomes7040034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/20/2019] [Accepted: 09/23/2019] [Indexed: 12/12/2022] Open
Abstract
Regulated exocytosis enables temporal and spatial control over the secretion of biologically active compounds; however, the mechanism by which Ca2+ modulates different stages of exocytosis is still poorly understood. For an unbiased, top-down proteomic approach, select thiol- reactive reagents were used to investigate this process in release-ready native secretory vesicles. We previously characterized a biphasic effect of these reagents on Ca2+-triggered exocytosis: low doses potentiated Ca2+ sensitivity, whereas high doses inhibited Ca2+ sensitivity and extent of vesicle fusion. Capitalizing on this novel potentiating effect, we have now identified fluorescent thiol- reactive reagents producing the same effects: Lucifer yellow iodoacetamide, monobromobimane, and dibromobimane. Top-down proteomic analyses of fluorescently labeled proteins from total and cholesterol-enriched vesicle membrane fractions using two-dimensional gel electrophoresis coupled with mass spectrometry identified several candidate targets, some of which have been previously linked to the late steps of regulated exocytosis and some of which are novel. Initial validation studies indicate that Rab proteins are involved in the modulation of Ca2+ sensitivity, and thus the efficiency of membrane fusion, which may, in part, be linked to their previously identified upstream roles in vesicle docking.
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Affiliation(s)
- Kendra L Furber
- Northern Medical Program, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada.
| | - Peter S Backlund
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Alfred L Yergey
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jens R Coorssen
- Department of Health Sciences, Faculty of Applied Health Sciences and Department of Biological Sciences, Faculty of Mathematics & Science, Brock University, St. Catharines, ON L2S 3A1, Canada.
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16
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Deák F, Anderson RE, Fessler JL, Sherry DM. Novel Cellular Functions of Very Long Chain-Fatty Acids: Insight From ELOVL4 Mutations. Front Cell Neurosci 2019; 13:428. [PMID: 31616255 PMCID: PMC6763723 DOI: 10.3389/fncel.2019.00428] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 09/06/2019] [Indexed: 12/22/2022] Open
Abstract
Elongation of Very Long chain fatty acids-4 (ELOVL4) protein is a member of the ELOVL family of fatty acid elongases that is collectively responsible for catalyzing formation of long chain fatty acids. ELOVL4 is the only family member that catalyzes production of Very Long Chain Saturated Fatty Acids (VLC-SFA) and Very Long Chain Polyunsaturated Fatty Acids (VLC-PUFA) with chain lengths ≥28 carbons. ELOVL4 and its VLC-SFA and VLC-PUFA products are emerging as important regulators of synaptic signaling and neuronal survival in the central nervous system (CNS). Distinct sets of mutations in ELOVL4 cause three different neurological diseases in humans. Heterozygous inheritance of one set of autosomal dominant ELOVL4 mutations that leads to truncation of the ELOVL4 protein causes Stargardt-like macular dystrophy (STGD3), an aggressive juvenile-onset retinal degeneration. Heterozygous inheritance of a different set of autosomal dominant ELOVL4 mutations that leads to a full-length protein with single amino acid substitutions causes spinocerebellar ataxia 34 (SCA34), a late-onset neurodegenerative disease characterized by gait ataxia and cerebellar atrophy. Homozygous inheritance of a different set of ELOVL4 mutations causes a more severe disease with infantile onset characterized by seizures, spasticity, intellectual disability, ichthyosis, and premature death. ELOVL4 is expressed widely in the CNS and is found primarily in neurons. ELOVL4 is expressed in cell-specific patterns within different regions of the CNS that are likely to be related to disease symptoms. In the retina, ELOVL4 is expressed exclusively in photoreceptors and produces VLC-PUFA that are incorporated into phosphatidylcholine and enriched in the light sensitive membrane disks of the photoreceptor outer segments. VLC-PUFA are enzymatically converted into "elovanoid" compounds that appear to provide paracrine signals that promote photoreceptor and neuronal survival. In the brain, the main ELOVL4 products are VLC-SFA that are incorporated into sphingolipids and enriched in synaptic vesicles, where they regulate kinetics of presynaptic neurotransmitter release. Understanding the function of ELOVL4 and its VLC-SFA and VLC-PUFA products will advance our understanding of basic mechanisms in neural signaling and has potential for developing novel therapies for seizure and neurodegenerative diseases.
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Affiliation(s)
- Ferenc Deák
- Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Robert E Anderson
- Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Jennifer L Fessler
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - David M Sherry
- Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
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17
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Quevedo MF, Bustos MA, Masone D, Roggero CM, Bustos DM, Tomes CN. Grab recruitment by Rab27A-Rabphilin3a triggers Rab3A activation in human sperm exocytosis. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2019; 1866:612-622. [PMID: 30599141 DOI: 10.1016/j.bbamcr.2018.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/30/2018] [Accepted: 12/09/2018] [Indexed: 12/12/2022]
Abstract
Sperm must undergo the regulated exocytosis of its dense core granule (the acrosome reaction, AR) to fertilize the egg. We have previously described that Rabs3 and 27 are organized in a RabGEF cascade within the signaling pathway elicited by exocytosis stimuli in human sperm. Here, we report the identity and the role of two molecules that link these secretory Rabs in the RabGEF cascade: Rabphilin3a and GRAB. Like Rab3 and Rab27, GRAB and Rabphilin3a are present, localize to the acrosomal region and are required for calcium-triggered exocytosis in human sperm. Sequestration of either protein with specific antibodies introduced into streptolysin O-permeabilized sperm impairs the activation of Rab3 in the acrosomal region elicited by calcium, but not that of Rab27. Biochemical and functional assays indicate that Rabphilin3a behaves as a Rab27 effector during the AR and that GRAB exhibits GEF activity toward Rab3A. Recombinant, active Rab27A pulls down Rabphilin3a and GRAB from human sperm extracts. Conversely, immobilized Rabphilin3a recruits Rab27 and GRAB; the latter promotes Rab3A activation. The enzymatic activity of GRAB toward Rab3A was also suggested by in silico and in vitro assays with purified proteins. In summary, we describe here a signaling module where Rab27A-GTP interacts with Rabphilin3a, which in turn recruits a guanine nucleotide-exchange activity toward Rab3A. This is the first description of the interaction of Rabphilin3a with a GEF. Because the machinery that drives exocytosis is highly conserved, it is tempting to hypothesize that the RabGEF cascade unveiled here might be part of the molecular mechanisms that drive exocytosis in other secretory systems.
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Affiliation(s)
- María Florencia Quevedo
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Matías Alberto Bustos
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Diego Masone
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ingeniería, Universidad Nacional de Cuyo, Argentina
| | | | - Diego Martín Bustos
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Argentina
| | - Claudia Nora Tomes
- Instituto de Histologia y Embriologia de Mendoza (IHEM) Dr. Mario H. Burgos-CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Argentina; Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Argentina.
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18
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Nicolau S, Milone M. The Electrophysiology of Presynaptic Congenital Myasthenic Syndromes With and Without Facilitation: From Electrodiagnostic Findings to Molecular Mechanisms. Front Neurol 2019; 10:257. [PMID: 30941097 PMCID: PMC6433874 DOI: 10.3389/fneur.2019.00257] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 02/26/2019] [Indexed: 11/13/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are a group of inherited disorders of neuromuscular transmission most commonly presenting with early onset fatigable weakness, ptosis, and ophthalmoparesis. CMS are classified according to the localization of the causative molecular defect. CMS with presynaptic dysfunction can be caused by mutations in several different genes, including those involved in acetylcholine synthesis, its packaging into synaptic vesicles, vesicle docking, and release from the presynaptic nerve terminal and neuromuscular junction development and maintenance. Electrodiagnostic testing is key in distinguishing CMS from other neuromuscular disorders with similar clinical features as well as for revealing features pointing to a specific molecular diagnosis. A decremental response on low-frequency repetitive nerve stimulation (RNS) is present in most presynaptic CMS. In CMS with deficits in acetylcholine resynthesis however, a decrement may only appear after conditioning with exercise or high-frequency RNS and characteristically displays a slow recovery. Facilitation occurs in CMS caused by mutations in VAMP1, UNC13A, SYT2, AGRN, LAMA5. By contrast, facilitation is absent in the other presynaptic CMS described to date. An understanding of the underlying molecular mechanisms therefore assists the interpretation of electrodiagnostic findings in patients with suspected CMS.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
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19
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Alford S, Hamm H, Rodriguez S, Zurawski Z. Gβγ SNARE Interactions and Their Behavioral Effects. Neurochem Res 2018; 44:636-649. [PMID: 29752624 DOI: 10.1007/s11064-018-2531-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 04/09/2018] [Accepted: 04/16/2018] [Indexed: 11/25/2022]
Abstract
Presynaptic terminals possess interlocking molecular mechanisms that control exocytosis. An example of such complexity is the modulation of release by presynaptic G Protein Coupled Receptors (GPCRs). GPCR ubiquity at synapses-GPCRs are present at every studied presynaptic terminal-underlies their critical importance in synaptic function. GPCRs mediate presynaptic modulation by mechanisms including via classical Gα effectors, but membrane-delimited actions of Gβγ can also alter probability of release by altering presynaptic ionic conductances. This directly or indirectly modifies action potential-evoked presynaptic Ca2+ entry. In addition, Gβγ can interact directly with SNARE complexes responsible for synaptic vesicle fusion to reduce peak cleft neurotransmitter concentrations during evoked release. The interaction of Gβγ with SNARE is displaced via competitive interaction with C2AB-domain containing calcium sensors such as synaptotagmin I in a Ca2+-sensitive manner, restoring exocytosis. Synaptic modulation of this form allows selective inhibition of postsynaptic receptor-mediated responses, and this, in combination with Ca2+ sensitivity of Gβγ effects on SNARE complexes allows for specific behavioral outcomes. One such outcome mediated by 5-HT receptors in the spinal cord seen in all vertebrates shows remarkable synergy between presynaptic effects of Gβγ and postsynaptic 5-HT-mediated changes in activation of Ca2+-dependent K+ channels. While acting through entirely separate cellular compartments and signal transduction pathways, these effects converge on the same effect on locomotion and other critical functions of the central nervous system.
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Affiliation(s)
- Simon Alford
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, 60612-7308, USA.
| | - Heidi Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232-6600, USA
| | - Shelagh Rodriguez
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, 60612-7308, USA
| | - Zack Zurawski
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, 60612-7308, USA
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232-6600, USA
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20
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Maselli RA, Vázquez J, Schrumpf L, Arredondo J, Lara M, Strober JB, Pytel P, Wollmann RL, Ferns M. Presynaptic congenital myasthenic syndrome with altered synaptic vesicle homeostasis linked to compound heterozygous sequence variants in RPH3A. Mol Genet Genomic Med 2018; 6:434-440. [PMID: 29441694 PMCID: PMC6014458 DOI: 10.1002/mgg3.370] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Revised: 01/06/2018] [Accepted: 11/20/2017] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Monogenic defects of synaptic vesicle (SV) homeostasis have been implicated in many neurologic diseases, including autism, epilepsy, and movement disorders. In addition, abnormal vesicle exocytosis has been associated with several endocrine dysfunctions. METHODS We report an 11 year old girl with learning disabilities, tremors, ataxia, transient hyperglycemia, and muscle fatigability responsive to albuterol sulfate. Failure of neuromuscular transmission was confirmed by single fiber electromyography. Electron microscopy of motor nerve terminals revealed marked reduction in SV density, double-membrane-bound sacs containing SVs, abundant endosomes, and degenerative lamellar bodies. The patient underwent whole exome sequencing (WES) and relevant sequence variants were expressed and studied in a mammalian cell line. RESULTS Chromosomal microarray studies and next generation sequencing (NGS) of mitochondrial DNA were unrevealing; however, NGS of genomic DNA showed two rare sequence variants in the gene encoding rabphilin 3a (RPH3A). The paternally inherited variant c.806 G>A (p.Arg269Gln) involves a substitution of a conserved residue in the linker region, while the maternally inherited variant c.1390 G>T (p.Val464Leu) involves a conserved amino acid substitution in the highly conserved C2A region. Expression studies revealed that p.Arg269Gln strongly impairs the binding of rabphilin 3a to 14-3-3, which is a proposed regulator of synaptic transmission and plasticity. In contrast, the binding of rabphilin 3a to 14-3-3 is only marginally impaired by p.Val464Leu; thus, the pathogenic role of p.Val464Leu remains unclear. CONCLUSION In summary, we report a patient with a multisystem neurologic disorder and altered SV regulation attributed to defects in RPH3A, which grants further studies of this gene in human disorders of synaptic transmission.
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Affiliation(s)
| | - Jessica Vázquez
- Department of NeurologyUniversity of California DavisSacramentoCAUSA
| | - Leah Schrumpf
- Department of NeurologyUniversity of California DavisSacramentoCAUSA
| | - Juan Arredondo
- Department of NeurologyUniversity of California DavisSacramentoCAUSA
| | - Marian Lara
- Department of NeurologyUniversity of California DavisSacramentoCAUSA
| | - Jonathan B. Strober
- Department of NeurologyUniversity of California San FranciscoSan FranciscoCAUSA
| | - Peter Pytel
- Department of PathologyUniversity of ChicagoChicagoILUSA
| | | | - Michael Ferns
- Department of Anesthesiology and Pain MedicineUniversity of California DavisSacramentoCAUSA
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21
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Yasuda Y, Iwama S, Kiyota A, Izumida H, Nakashima K, Iwata N, Ito Y, Morishita Y, Goto M, Suga H, Banno R, Enomoto A, Takahashi M, Arima H, Sugimura Y. Critical role of rabphilin-3A in the pathophysiology of experimental lymphocytic neurohypophysitis. J Pathol 2018; 244:469-478. [PMID: 29377134 DOI: 10.1002/path.5046] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 01/04/2018] [Accepted: 01/09/2018] [Indexed: 12/17/2023]
Abstract
Autoimmune hypophysitis (AH) is thought to be an autoimmune disease characterized by lymphocytic infiltration of the pituitary gland. Among AH pathologies, lymphocytic infundibulo-neurohypophysitis (LINH) involves infiltration of the neurohypophysis and/or the hypothalamic infundibulum, causing central diabetes insipidus resulting from insufficiency of arginine vasopressin secretion. The pathophysiological and pathogenetic mechanisms underlying LINH are largely unknown. Clinically, differentiating LINH from other pituitary diseases accompanied by mass lesions, including tumours, has often been difficult, because of similar clinical manifestations. We recently reported that rabphilin-3A is an autoantigen and that anti-rabphilin-3A antibodies constitute a possible diagnostic marker for LINH. However, the involvement of rabphilin-3A in the pathogenesis of LINH remains to be elucidated. This study was undertaken to explore the role of rabphilin-3A in lymphocytic neurohypophysitis and to investigate the mechanism. We found that immunization of mice with rabphilin-3A led to neurohypophysitis. Lymphocytic infiltration was observed in the neurohypophysis and supraoptic nucleus 1 month after the first immunization. Mice immunized with rabphilin-3A showed an increase in the volume of urine that was hypotonic as compared with control mice. Administration of a cocktail of monoclonal anti-rabphilin-3A antibodies did not induce neurohypophysitis. However, abatacept, which is a chimeric protein that suppresses T-cell activation, decreased the number of T cells specific for rabphilin-3A in peripheral blood mononuclear cells (PBMCs). It ameliorated lymphocytic infiltration of CD3+ T cells in the neurohypophysis of mice that had been immunized with rabphilin-3A. Additionally, there was a linear association between the number of T cells specific for rabphilin-3A in PBMCs and the number of CD3+ T cells infiltrating the neurohypophysis. In conclusion, we suggest that rabphilin-3A is a pathogenic antigen, and that T cells specific for rabphilin-3A are involved in the pathogenesis of neurohypophysitis in mice. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Yoshinori Yasuda
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shintaro Iwama
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Research Centre of Health, Physical Fitness and Sports, Nagoya University, Japan
| | - Atsushi Kiyota
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hisakazu Izumida
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kohtaro Nakashima
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Naoko Iwata
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshihiro Ito
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshiaki Morishita
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Motomitsu Goto
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hidetaka Suga
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Ryoichi Banno
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Atsushi Enomoto
- Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Masahide Takahashi
- Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hiroshi Arima
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshihisa Sugimura
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Fujita Health University, Toyoake, Japan
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22
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Nakashima K, Takeuchi S, Iwama S, Kiyota A, Yasuda Y, Iwata N, Enomoto A, Arima H, Sugimura Y. Cullin-associated NEDD8-dissociated protein 1, a novel interactor of rabphilin-3A, deubiquitylates rabphilin-3A and regulates arginine vasopressin secretion in PC12 cells. Endocr J 2018; 65:325-334. [PMID: 29367474 DOI: 10.1507/endocrj.ej17-0399] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The molecular mechanism involved in the exocytosis of arginine vasopressin (AVP) is not fully known. Rabphilin-3A has been suggested as a novel autoantigen in infundibulo-neurohypophysitis (LINH), which leads to central diabetes insipidus through insufficient secretion of AVP. However, the role of rabphilin-3A in the pathogenesis of LINH remains unclear. Thus, the aim of the present study was to identify proteins binding rabphilin-3A in the posterior pituitary. Using glutathione S-transferase (GST)-pulldown assays and proteomic analyses, cullin-associated NEDD8-dissociated protein 1 (CAND1) was identified as a rabphilin-3A-binding protein in the posterior pituitary. Co-immunoprecipitation assays indicated that CAND1 interacted endogenously with rabphilin-3A. In addition, immunohistochemistry experiments showed that CAND1 immunoreactivity was detected mainly in the posterior pituitary, intermediate lobe, and the supraoptic nucleus in the hypothalamus, and less in the anterior lobe, partially co-localizing with rabphilin-3A. Overexpression of CAND1 resulted in deubiquitylation of rabphilin-3A in PC12 cells. Moreover, overexpression of CAND1 in PC12 cells co-transfected with AVP enhanced both basal and KCl-stimulated AVP secretion. The findings indicate that CAND1 inhibits the ubiquitylation of rabphilin-3A and positively regulates AVP secretion. These data shed light on a novel potential mechanism involving rabphilin-3A in AVP secretion, and suggest a new role of CAND1 as a regulator of hormone or neurotransmitter secretion.
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Affiliation(s)
- Kohtaro Nakashima
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Seiji Takeuchi
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Shintaro Iwama
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Atsushi Kiyota
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Yoshinori Yasuda
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Naoko Iwata
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Atsushi Enomoto
- Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Hiroshi Arima
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Yoshihisa Sugimura
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Fujita Health University, Toyoake, Aichi 470-1192 Japan
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23
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Abstract
Synapse is the basic structural and functional component for neural communication in the brain. The presynaptic terminal is the structural and functionally essential area that initiates communication and maintains the continuous functional neural information flow. It contains synaptic vesicles (SV) filled with neurotransmitters, an active zone for release, and numerous proteins for SV fusion and retrieval. The structural and functional synaptic plasticity is a representative characteristic; however, it is highly vulnerable to various pathological conditions. In fact, synaptic alteration is thought to be central to neural disease processes. In particular, the alteration of the structural and functional phenotype of the presynaptic terminal is a highly significant evidence for neural diseases. In this review, we specifically describe structural and functional alteration of nerve terminals in several neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD).
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Affiliation(s)
- Jae Ryul Bae
- Department of Biomedical Science, Graduate School, Kyung Hee University, Seoul 02447, Korea
| | - Sung Hyun Kim
- Department of Physiology, School of Medicine, Kyung Hee University, Seoul 02447, Korea
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24
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Molecular Insights into the Roles of Rab Proteins in Intracellular Dynamics and Neurodegenerative Diseases. Neuromolecular Med 2018; 20:18-36. [PMID: 29423895 DOI: 10.1007/s12017-018-8479-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/27/2018] [Indexed: 02/01/2023]
Abstract
In eukaryotes, the cellular functions are segregated to membrane-bound organelles. This inherently requires sorting of metabolites to membrane-limited locations. Sorting the metabolites from ribosomes to various organelles along the intracellular trafficking pathways involves several integral cellular processes, including an energy-dependent step, in which the sorting of metabolites between organelles is catalyzed by membrane-anchoring protein Rab-GTPases (Rab). They contribute to relaying the switching of the secretory proteins between hydrophobic and hydrophilic environments. The intracellular trafficking routes include exocytic and endocytic pathways. In these pathways, numerous Rab-GTPases are participating in discrete shuttling of cargoes. Long-distance trafficking of cargoes is essential for neuronal functions, and Rabs are critical for these functions, including the transport of membranes and essential proteins for the development of axons and neurites. Rabs are also the key players in exocytosis of neurotransmitters and recycling of neurotransmitter receptors. Thus, Rabs are critical for maintaining neuronal communication, as well as for normal cellular physiology. Therefore, cellular defects of Rab components involved in neural functions, which severely affect normal brain functions, can produce neurological complications, including several neurodegenerative diseases. In this review, we provide a comprehensive overview of the current understanding of the molecular signaling pathways of Rab proteins and the impact of their defects on different neurodegenerative diseases. The insights gathered into the dynamics of Rabs that are described in this review provide new avenues for developing effective treatments for neurodegenerative diseases-associated with Rab defects.
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25
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 446] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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26
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Homozygous Expression of Mutant ELOVL4 Leads to Seizures and Death in a Novel Animal Model of Very Long-Chain Fatty Acid Deficiency. Mol Neurobiol 2017; 55:1795-1813. [PMID: 29168048 PMCID: PMC5820379 DOI: 10.1007/s12035-017-0824-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 11/07/2017] [Indexed: 10/24/2022]
Abstract
Lipids are essential components of the nervous system. However, the functions of very long-chain fatty acids (VLC-FA; ≥ 28 carbons) in the brain are unknown. The enzyme ELOngation of Very Long-chain fatty acids-4 (ELOVL4) catalyzes the rate-limiting step in the biosynthesis of VLC-FA (Agbaga et al., Proc Natl Acad Sci USA 105(35): 12843-12848, 2008; Logan et al., J Lipid Res 55(4): 698-708, 2014), which we identified in the brain as saturated fatty acids (VLC-SFA). Homozygous mutations in ELOVL4 cause severe neuropathology in humans (Ozaki et al., JAMA Neurol 72(7): 797-805, 2015; Mir et al., BMC Med Genet 15: 25, 2014; Cadieux-Dion et al., JAMA Neurol 71(4): 470-475, 2014; Bourassa et al., JAMA Neurol 72(8): 942-943, 2015; Aldahmesh et al., Am J Hum Genet 89(6): 745-750, 2011) and are post-natal lethal in mice (Cameron et al., Int J Biol Sci 3(2): 111-119, 2007; Li et al., Int J Biol Sci 3(2): 120-128, 2007; McMahon et al., Molecular Vision 13: 258-272, 2007; Vasireddy et al., Hum Mol Genet 16(5): 471-482, 2007) from dehydration due to loss of VLC-SFA that comprise the skin permeability barrier. Double transgenic mice with homozygous knock-in of the Stargardt-like macular dystrophy (STDG3; 797-801_AACTT) mutation of Elovl4 with skin-specific rescue of wild-type Elovl4 expression (S + Elovl4 mut/mut mice) develop seizures by P19 and die by P21. Electrophysiological analyses of hippocampal slices showed aberrant epileptogenic activity in S + Elovl4 mut/mut mice. FM1-43 dye release studies showed that synapses made by cultured hippocampal neurons from S + Elovl4 mut/mut mice exhibited accelerated synaptic release kinetics. Supplementation of VLC-SFA to cultured hippocampal neurons from mutant mice rescued defective synaptic release to wild-type rates. Together, these studies establish a critical, novel role for ELOVL4 and its VLC-SFA products in regulating synaptic release kinetics and epileptogenesis. Future studies aimed at understanding the molecular mechanisms by which VLC-SFA regulate synaptic function may provide new targets for improved seizure therapies.
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27
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Ferrer-Orta C, Pérez-Sánchez MD, Coronado-Parra T, Silva C, López-Martínez D, Baltanás-Copado J, Gómez-Fernández JC, Corbalán-García S, Verdaguer N. Structural characterization of the Rabphilin-3A-SNAP25 interaction. Proc Natl Acad Sci U S A 2017; 114:E5343-E5351. [PMID: 28634303 PMCID: PMC5502619 DOI: 10.1073/pnas.1702542114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Membrane fusion is essential in a myriad of eukaryotic cell biological processes, including the synaptic transmission. Rabphilin-3A is a membrane trafficking protein involved in the calcium-dependent regulation of secretory vesicle exocytosis in neurons and neuroendocrine cells, but the underlying mechanism remains poorly understood. Here, we report the crystal structures and biochemical analyses of Rabphilin-3A C2B-SNAP25 and C2B-phosphatidylinositol 4,5-bisphosphate (PIP2) complexes, revealing how Rabphilin-3A C2 domains operate in cooperation with PIP2/Ca2+ and SNAP25 to bind the plasma membrane, adopting a conformation compatible to interact with the complete SNARE complex. Comparisons with the synaptotagmin1-SNARE show that both proteins contact the same SNAP25 surface, but Rabphilin-3A uses a unique structural element. Data obtained here suggest a model to explain the Ca2+-dependent fusion process by membrane bending with a myriad of variations depending on the properties of the C2 domain-bearing protein, shedding light to understand the fine-tuning control of the different vesicle fusion events.
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Affiliation(s)
- Cristina Ferrer-Orta
- Structural Biology Unit, Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain;
| | - María Dolores Pérez-Sánchez
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Teresa Coronado-Parra
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Cristina Silva
- Structural Biology Unit, Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain
| | - David López-Martínez
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Jesús Baltanás-Copado
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Juan Carmelo Gómez-Fernández
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Senena Corbalán-García
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Regional Campus of International Excellence "Campus Mare Nostrum," Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, 30100 Murcia, Spain
| | - Núria Verdaguer
- Structural Biology Unit, Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain;
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28
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Pinheiro PS, Houy S, Sørensen JB. C2-domain containing calcium sensors in neuroendocrine secretion. J Neurochem 2016; 139:943-958. [DOI: 10.1111/jnc.13865] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/17/2016] [Accepted: 10/05/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Paulo S. Pinheiro
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Sébastien Houy
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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29
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Petrie M, Esquibel J, Kabachinski G, Maciuba S, Takahashi H, Edwardson JM, Martin TFJ. The Vesicle Priming Factor CAPS Functions as a Homodimer via C2 Domain Interactions to Promote Regulated Vesicle Exocytosis. J Biol Chem 2016; 291:21257-21270. [PMID: 27528604 PMCID: PMC5076532 DOI: 10.1074/jbc.m116.728097] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/29/2016] [Indexed: 11/06/2022] Open
Abstract
Neurotransmitters and peptide hormones are secreted by regulated vesicle exocytosis. CAPS (also known as CADPS) is a 145-kDa cytosolic and peripheral membrane protein required for vesicle docking and priming steps that precede Ca2+-triggered vesicle exocytosis. CAPS binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and SNARE proteins and is proposed to promote SNARE protein complex assembly for vesicle docking and priming. We characterized purified soluble CAPS as mainly monomer in equilibrium with small amounts of dimer. However, the active form of CAPS bound to PC12 cell membranes or to liposomes containing PI(4,5)P2 and Q-SNARE proteins was mainly dimer. CAPS dimer formation required its C2 domain based on mutation or deletion studies. Moreover, C2 domain mutations or deletions resulted in a loss of CAPS function in regulated vesicle exocytosis, indicating that dimerization is essential for CAPS function. Comparison of the CAPS C2 domain to a structurally defined Munc13-1 C2A domain dimer revealed conserved residues involved in CAPS dimerization. We conclude that CAPS functions as a C2 domain-mediated dimer in regulated vesicle exocytosis. The unique tandem C2-PH domain of CAPS may serve as a PI(4,5)P2-triggered switch for dimerization. CAPS dimerization may be coupled to oligomeric SNARE complex assembly for vesicle docking and priming.
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Affiliation(s)
- Matt Petrie
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Joseph Esquibel
- From the Department of Biochemistry, Program of Molecular and Cellular Pharmacology, and
| | - Greg Kabachinski
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Stephanie Maciuba
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and
| | - Hirohide Takahashi
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - J Michael Edwardson
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Thomas F J Martin
- From the Department of Biochemistry, Integrated Program in Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, and Program of Molecular and Cellular Pharmacology, and
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30
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Bello OD, Cappa AI, de Paola M, Zanetti MN, Fukuda M, Fissore RA, Mayorga LS, Michaut MA. Rab3A, a possible marker of cortical granules, participates in cortical granule exocytosis in mouse eggs. Exp Cell Res 2016; 347:42-51. [PMID: 27423421 DOI: 10.1016/j.yexcr.2016.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 07/04/2016] [Accepted: 07/12/2016] [Indexed: 10/21/2022]
Abstract
Fusion of cortical granules with the oocyte plasma membrane is the most significant event to prevent polyspermy. This particular exocytosis, also known as cortical reaction, is regulated by calcium and its molecular mechanism is still not known. Rab3A, a member of the small GTP-binding protein superfamily, has been implicated in calcium-dependent exocytosis and is not yet clear whether Rab3A participates in cortical granules exocytosis. Here, we examine the involvement of Rab3A in the physiology of cortical granules, particularly, in their distribution during oocyte maturation and activation, and their participation in membrane fusion during cortical granule exocytosis. Immunofluorescence and Western blot analysis showed that Rab3A and cortical granules have a similar migration pattern during oocyte maturation, and that Rab3A is no longer detected after cortical granule exocytosis. These results suggested that Rab3A might be a marker of cortical granules. Overexpression of EGFP-Rab3A colocalized with cortical granules with a Pearson correlation coefficient of +0.967, indicating that Rab3A and cortical granules have almost a perfect colocalization in the egg cortical region. Using a functional assay, we demonstrated that microinjection of recombinant, prenylated and active GST-Rab3A triggered cortical granule exocytosis, indicating that Rab3A has an active role in this secretory pathway. To confirm this active role, we inhibited the function of endogenous Rab3A by microinjecting a polyclonal antibody raised against Rab3A prior to parthenogenetic activation. Our results showed that Rab3A antibody microinjection abolished cortical granule exocytosis in parthenogenetically activated oocytes. Altogether, our findings confirm that Rab3A might function as a marker of cortical granules and participates in cortical granule exocytosis in mouse eggs.
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Affiliation(s)
- Oscar Daniel Bello
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina
| | - Andrea Isabel Cappa
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina
| | - Matilde de Paola
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina
| | - María Natalia Zanetti
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina
| | - Mitsunori Fukuda
- Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Rafael A Fissore
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, 661 North Pleasant Street, Amherst, MA 01003, USA
| | - Luis S Mayorga
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina
| | - Marcela A Michaut
- Instituto de Histología y Embriología, CONICET - Universidad Nacional de Cuyo, Av. Libertador 80, 5500 Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Argentina.
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31
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Benleulmi-Chaachoua A, Chen L, Sokolina K, Wong V, Jurisica I, Emerit MB, Darmon M, Espin A, Stagljar I, Tafelmeyer P, Zamponi GW, Delagrange P, Maurice P, Jockers R. Protein interactome mining defines melatonin MT1 receptors as integral component of presynaptic protein complexes of neurons. J Pineal Res 2016; 60:95-108. [PMID: 26514267 DOI: 10.1111/jpi.12294] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 10/26/2015] [Indexed: 01/11/2023]
Abstract
In mammals, the hormone melatonin is mainly produced by the pineal gland with nocturnal peak levels. Its peripheral and central actions rely either on its intrinsic antioxidant properties or on binding to melatonin MT1 and MT2 receptors, belonging to the G protein-coupled receptor (GPCR) super-family. Melatonin has been reported to be involved in many functions of the central nervous system such as circadian rhythm regulation, neurotransmission, synaptic plasticity, memory, sleep, and also in Alzheimer's disease and depression. However, little is known about the subcellular localization of melatonin receptors and the molecular aspects involved in neuronal functions of melatonin. Identification of protein complexes associated with GPCRs has been shown to be a valid approach to improve our understanding of their function. By combining proteomic and genomic approaches we built an interactome of MT1 and MT2 receptors, which comprises 378 individual proteins. Among the proteins interacting with MT1 , but not with MT2 , we identified several presynaptic proteins, suggesting a potential role of MT1 in neurotransmission. Presynaptic localization of MT1 receptors in the hypothalamus, striatum, and cortex was confirmed by subcellular fractionation experiments and immunofluorescence microscopy. MT1 physically interacts with the voltage-gated calcium channel Cav 2.2 and inhibits Cav 2.2-promoted Ca(2+) entry in an agonist-independent manner. In conclusion, we show that MT1 is part of the presynaptic protein network and negatively regulates Cav 2.2 activity, providing a first hint for potential synaptic functions of MT1.
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Affiliation(s)
- Abla Benleulmi-Chaachoua
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Lina Chen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Kate Sokolina
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Victoria Wong
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Igor Jurisica
- Princess Margaret Cancer Centre, University Health Network and TECHNA Institute for the Advancement of Technology for Health, Toronto, ON, Canada
| | - Michel Boris Emerit
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France
| | - Michèle Darmon
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France
| | - Almudena Espin
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Igor Stagljar
- Donnelly Centre, Department of Biochemistry, Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | | | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | | | - Pascal Maurice
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Ralf Jockers
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
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Mutational Analysis of Rab3 Function for Controlling Active Zone Protein Composition at the Drosophila Neuromuscular Junction. PLoS One 2015; 10:e0136938. [PMID: 26317909 PMCID: PMC4552854 DOI: 10.1371/journal.pone.0136938] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/11/2015] [Indexed: 11/26/2022] Open
Abstract
At synapses, the release of neurotransmitter is regulated by molecular machinery that aggregates at specialized presynaptic release sites termed active zones. The complement of active zone proteins at each site is a determinant of release efficacy and can be remodeled to alter synapse function. The small GTPase Rab3 was previously identified as playing a novel role that controls the distribution of active zone proteins to individual release sites at the Drosophila neuromuscular junction. Rab3 has been extensively studied for its role in the synaptic vesicle cycle; however, the mechanism by which Rab3 controls active zone development remains unknown. To explore this mechanism, we conducted a mutational analysis to determine the molecular and structural requirements of Rab3 function at Drosophila synapses. We find that GTP-binding is required for Rab3 to traffick to synapses and distribute active zone components across release sites. Conversely, the hydrolytic activity of Rab3 is unnecessary for this function. Through a structure-function analysis we identify specific residues within the effector-binding switch regions that are required for Rab3 function and determine that membrane attachment is essential. Our findings suggest that Rab3 controls the distribution of active zone components via a vesicle docking mechanism that is consistent with standard Rab protein function.
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Chang RYK, Etheridge N, Nouwens AS, Dodd PR. SWATH analysis of the synaptic proteome in Alzheimer's disease. Neurochem Int 2015; 87:1-12. [PMID: 25958317 DOI: 10.1016/j.neuint.2015.04.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 10/23/2022]
Abstract
Brain tissue from Alzheimer's disease patients exhibits synaptic degeneration in selected regions. Synaptic dysfunction occurs early in the disease and is a primary pathological target for treatment. The molecular mechanisms underlying this degeneration remain unknown. Quantifying the synaptic proteome in autopsy brain and comparing tissue from Alzheimer's disease cases and subjects with normal aging are critical to understanding the molecular mechanisms associated with Alzheimer pathology. We isolated synaptosomes from hippocampus and motor cortex so as to reduce sample complexity relative to whole-tissue homogenates. Synaptosomal extracts were subjected to strong cation exchange (SCX) fractionation to further partition sample complexity; each fraction received SWATH-based information-dependent acquisition to generate a comprehensive peptide-ion library. The expression of synaptic proteins from AD hippocampus and motor cortex was then compared between groups. A total of 2077 unique proteins were identified at a critical local false discovery rate <5%. Thirty of these, including 17 novel proteins, exhibited significant expression differences between cases and controls; these proteins are involved in cellular functions including structural maintenance, signal transduction, autophagy, oxidative stress, and proteasome activity, or they have synaptic-vesicle related or energy-related functions. Differentially expressed proteins were subjected to pathway analysis to identify protein-protein interactions. This revealed that the most perturbed molecular and cellular functions were cellular assembly and organization. Core analysis revealed RhoA signaling to be the top canonical pathway. Network analysis showed that differentially expressed proteins were related to cellular assembly and organization, and cellular function and maintenance. This is the first study to combine SCX fractionation with SWATH analysis. SWATH is a promising new technique that can greatly enhance protein identification in any proteome, and has many other benefits; however, there are limitations yet to be resolved.
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Affiliation(s)
| | - Naomi Etheridge
- School of Chemistry and Molecular Biosciences, University of Queensland, Australia
| | - Amanda S Nouwens
- School of Chemistry and Molecular Biosciences, University of Queensland, Australia
| | - Peter R Dodd
- School of Chemistry and Molecular Biosciences, University of Queensland, Australia.
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Südhof TC. Der molekulare Mechanismus der Neurotransmitterfreisetzung und Nervenzell-Synapsen (Nobel-Aufsatz). Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406359] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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de Jong APH, Fioravante D. Translating neuronal activity at the synapse: presynaptic calcium sensors in short-term plasticity. Front Cell Neurosci 2014; 8:356. [PMID: 25400547 PMCID: PMC4212674 DOI: 10.3389/fncel.2014.00356] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 10/09/2014] [Indexed: 01/03/2023] Open
Abstract
The complex manner in which patterns of presynaptic neural activity are translated into short-term plasticity (STP) suggests the existence of multiple presynaptic calcium (Ca(2+)) sensors, which regulate the amplitude and time-course of STP and are the focus of this review. We describe two canonical Ca(2+)-binding protein domains (C2 domains and EF-hands) and define criteria that need to be met for a protein to qualify as a Ca(2+) sensor mediating STP. With these criteria in mind, we discuss various forms of STP and identify established and putative Ca(2+) sensors. We find that despite the multitude of proposed sensors, only three are well established in STP: Munc13, protein kinase C (PKC) and synaptotagmin-7. For putative sensors, we pinpoint open questions and potential pitfalls. Finally, we discuss how the molecular properties and modes of action of Ca(2+) sensors can explain their differential involvement in STP and shape net synaptic output.
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Affiliation(s)
| | - Diasynou Fioravante
- Department of Neurobiology, Physiology and Behavior, Center for Neuroscience, University of California Davis Davis, CA, USA
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Südhof TC. The molecular machinery of neurotransmitter release (Nobel lecture). Angew Chem Int Ed Engl 2014; 53:12696-717. [PMID: 25339369 DOI: 10.1002/anie.201406359] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Indexed: 12/18/2022]
Abstract
The most important property of synaptic transmission is its speed, which is crucial for the overall workings of the brain. In his Nobel Lecture, T. C. Südhof explains how the synaptic vesicle and the plasma membrane undergo rapid fusion during neurotransmitter release and how this process is spatially organized, such that opening of Ca(2+) -channels allows rapid translation of the entering Ca(2+) signal into a fusion event.
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Affiliation(s)
- Thomas C Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Lorry Lokey SIM1 Building 07-535 Room G1021, 265 Campus Drive, Stanford University School of Medicine, CA 94305 (USA)
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Wang D, Takeuchi H, Gao J, Zhang Z, Hirata M. Hetero-oligomerization of C2 domains of phospholipase C-related but catalytically inactive protein and synaptotagmin-1. Adv Biol Regul 2014; 57:120-9. [PMID: 25242442 DOI: 10.1016/j.jbior.2014.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 09/01/2014] [Accepted: 09/01/2014] [Indexed: 10/24/2022]
Abstract
The C2 domain is a protein module often found in molecules that regulate exocytosis. C2 domains mediate interactions between the parental molecule and Ca(2+), phospholipids, and proteins. Although various molecules have been shown to interact with several C2 domains, no interactions between the C2 domains from different molecules have yet been reported. In the present study, we identified direct interactions between the C2 domain of PRIP (phospholipase C-related but catalytically inactive protein) and the C2 domains of other molecules. Among the C2 domains examined, those of synaptotagmin-1 (Syt1-C2A and Syt1-C2B) and phospholipase C δ-1 bound to the C2 domain of PRIP. We investigated the interactions between the C2 domain of PRIP (PRIP-C2) with Syt1-C2A and Syt1-C2B, and the mode of binding of each was Ca(2+)-dependent and -independent, respectively. We further demonstrated that the Ca(2+) dependence of the interaction between PRIP-C2 and Syt1-C2A was attributed to Ca(2+) binding with Syt1-C2A, but not PRIP-C2, using a series of mutants prepared from both C2 domains. We previously reported that the interaction between PRIP-C2 and the membrane fusion machinery suggested a critical role for PRIP in exocytosis; therefore, the results of the present study further support the importance of PRIP-C2 in the inhibitory function of PRIP in regulating exocytosis.
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Affiliation(s)
- DaGuang Wang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Fukuoka 812-8582, Japan
| | - Hiroshi Takeuchi
- Division of Applied Pharmacology, Kyushu Dental University, Kitakyushu 803-8580, Japan.
| | - Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Fukuoka 812-8582, Japan
| | - Zhao Zhang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Fukuoka 812-8582, Japan; Stomatological Hospital of Hebei Medical University, Shijiazhuang 050017, PR China
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Fukuoka 812-8582, Japan.
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Signaling through C2 domains: more than one lipid target. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1536-47. [PMID: 24440424 DOI: 10.1016/j.bbamem.2014.01.008] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 12/30/2013] [Accepted: 01/07/2014] [Indexed: 02/05/2023]
Abstract
C2 domains are membrane-binding modules that share a common overall fold: a single compact Greek-key motif organized as an eight-stranded anti-parallel β-sandwich consisting of a pair of four-stranded β-sheets. A myriad of studies have demonstrated that in spite of sharing the common structural β-sandwich core, slight variations in the residues located in the interconnecting loops confer C2 domains with functional abilities to respond to different Ca(2+) concentrations and lipids, and to signal through protein-protein interactions as well. This review summarizes the main structural and functional findings on Ca(2+) and lipid interactions by C2 domains, including the discovery of the phosphoinositide-binding site located in the β3-β4 strands. The wide variety of functions, together with the different Ca(2+) and lipid affinities of these domains, converts this superfamily into a crucial player in many functions in the cell and more to be discovered. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Tan MGK, Lee C, Lee JH, Francis PT, Williams RJ, Ramírez MJ, Chen CP, Wong PTH, Lai MKP. Decreased rabphilin 3A immunoreactivity in Alzheimer's disease is associated with Aβ burden. Neurochem Int 2014; 64:29-36. [PMID: 24200817 DOI: 10.1016/j.neuint.2013.10.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/12/2013] [Accepted: 10/28/2013] [Indexed: 11/22/2022]
Abstract
Synaptic dysfunction, together with neuritic plaques, neurofibrillary tangles and cholinergic neuron loss is an established finding in the Alzheimer's disease (AD) neocortex. The synaptopathology of AD is known to involve both pre- and postsynaptic components. However, the status of rabphilin 3A (RPH3A), which interacts with the SNARE complex and regulates synaptic vesicle exocytosis and Ca(2+)-triggered neurotransmitter release, is at present unclear. In this study, we measured RPH3A and its ligand Rab3A as well as several SNARE proteins in postmortem neocortex of patients with AD, and found specific reductions of RPH3A immunoreactivity compared with aged controls. RPH3A loss correlated with dementia severity, cholinergic deafferentation, and increased β-amyloid (Aβ) concentrations. Furthermore, RPH3A expression is selectively downregulated in cultured neurons treated with Aβ25-35 peptides. Our data suggest that presynaptic SNARE dysfunction forms part of the synaptopathology of AD.
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Affiliation(s)
- Michelle G K Tan
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Clinical Research, Singapore General Hospital, Singapore
| | - Chingli Lee
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Jasinda H Lee
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Paul T Francis
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - Robert J Williams
- Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - María J Ramírez
- Department of Pharmacology, School of Medicine, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain
| | - Christopher P Chen
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Memory, Aging and Cognition Centre (MACC), National University Health System, Singapore
| | - Peter T-H Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Memory, Aging and Cognition Centre (MACC), National University Health System, Singapore
| | - Mitchell K P Lai
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Memory, Aging and Cognition Centre (MACC), National University Health System, Singapore.
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41
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Guillén J, Ferrer-Orta C, Buxaderas M, Pérez-Sánchez D, Guerrero-Valero M, Luengo-Gil G, Pous J, Guerra P, Gómez-Fernández JC, Verdaguer N, Corbalán-García S. Structural insights into the Ca2+ and PI(4,5)P2 binding modes of the C2 domains of rabphilin 3A and synaptotagmin 1. Proc Natl Acad Sci U S A 2013; 110:20503-8. [PMID: 24302762 PMCID: PMC3870689 DOI: 10.1073/pnas.1316179110] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteins containing C2 domains are the sensors for Ca(2+) and PI(4,5)P2 in a myriad of secretory pathways. Here, the use of a free-mounting system has enabled us to capture an intermediate state of Ca(2+) binding to the C2A domain of rabphilin 3A that suggests a different mechanism of ion interaction. We have also determined the structure of this domain in complex with PI(4,5)P2 and IP3 at resolutions of 1.75 and 1.9 Å, respectively, unveiling that the polybasic cluster formed by strands β3-β4 is involved in the interaction with the phosphoinositides. A comparative study demonstrates that the C2A domain is highly specific for PI(4,5)P2/PI(3,4,5)P3, whereas the C2B domain cannot discriminate among any of the diphosphorylated forms. Structural comparisons between C2A domains of rabphilin 3A and synaptotagmin 1 indicated the presence of a key glutamic residue in the polybasic cluster of synaptotagmin 1 that abolishes the interaction with PI(4,5)P2. Together, these results provide a structural explanation for the ability of different C2 domains to pull plasma and vesicle membranes close together in a Ca(2+)-dependent manner and reveal how this family of proteins can use subtle structural changes to modulate their sensitivity and specificity to various cellular signals.
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Affiliation(s)
- Jaime Guillén
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
| | - Cristina Ferrer-Orta
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain; and
| | - Mònica Buxaderas
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain; and
| | - Dolores Pérez-Sánchez
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
| | - Marta Guerrero-Valero
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
| | - Ginés Luengo-Gil
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
| | - Joan Pous
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain; and
- Institute for Research in Biomedicine, Parc Científic de Barcelona, 08028 Barcelona, Spain
| | - Pablo Guerra
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain; and
| | - Juan C. Gómez-Fernández
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
| | - Nuria Verdaguer
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Cientificas, 08028 Barcelona, Spain; and
| | - Senena Corbalán-García
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, 30100 Murcia, Spain
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Doc2b synchronizes secretion from chromaffin cells by stimulating fast and inhibiting sustained release. J Neurosci 2013; 33:16459-70. [PMID: 24133251 DOI: 10.1523/jneurosci.2656-13.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptotagmin-1 and -7 constitute the main calcium sensors mediating SNARE-dependent exocytosis in mouse chromaffin cells, but the role of a closely related calcium-binding protein, Doc2b, remains enigmatic. We investigated its role in chromaffin cells using Doc2b knock-out mice and high temporal resolution measurements of exocytosis. We found that the calcium dependence of vesicle priming and release triggering remained unchanged, ruling out an obligatory role for Doc2b in those processes. However, in the absence of Doc2b, release was shifted from the readily releasable pool to the subsequent sustained component. Conversely, upon overexpression of Doc2b, the sustained component was largely inhibited whereas the readily releasable pool was augmented. Electron microscopy revealed an increase in the total number of vesicles upon Doc2b overexpression, ruling out vesicle depletion as the cause for the reduced sustained component. Further experiments showed that, in the absence of Doc2b, the refilling of the readily releasable vesicle pools is faster, but incomplete. Faster refilling leads to an increase in the sustained component as newly primed vesicles fuse while the [Ca(2+)]i following stimulation is still high. We conclude that Doc2b acts to inhibit vesicle priming during prolonged calcium elevations, thus protecting unprimed vesicles from fusing prematurely, and redirecting them to refill the readily releasable pool after relaxation of the calcium signal. In sum, Doc2b favors fast, synchronized release, and limits out-of-phase secretion.
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43
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Bui L, Glavinović MI. Is replenishment of the readily releasable pool associated with vesicular movement? Cogn Neurodyn 2013; 8:99-110. [PMID: 24624230 DOI: 10.1007/s11571-013-9264-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 06/19/2013] [Accepted: 07/23/2013] [Indexed: 12/30/2022] Open
Abstract
At the excitatory synapse of rat hippocampus the short-term synaptic depression observed during long high-frequency stimulation is associated with slower replenishment of the readily-releasable pool. Given that the replenishment rate is also not [Ca(++)]o sensitive this puts into question a widely held notion that the vesicles-constrained by the cytoskeleton and rendered free from such constraints by Ca(++) entry that renders them more mobile-are important in the replenishment of the readily-releasable pool. This raises a question-Is vesicular replenishment of the readily releasable pool associated with significant movement? To answer this question we evaluated how okadaic acid and staurosporine (compounds known to affect vesicular mobility) influence the replenishment rate. We used patterned stimulation on the Schaffer collateral fiber pathway and recorded the excitatory post-synaptic currents (EPSCs) from rat CA1 neurons, in the absence and presence of these drugs. The parameters of a circuit model with two vesicular pools were estimated by minimizing the squared difference between the ESPC amplitudes and simulated model output. [Ca(2+)]o did not influence the progressive decrease of the replenishment rate during long, high frequency stimulation. Okadaic acid did not significantly affect any parameters of the vesicular storage and release system, including the replenishment rate. Staurosporine reduced the replenishment coupling, but not the replenishment rate, and this is owing to the fact that it also reduces the ability of the readily releasable pool to contain quanta. Moreover, these compounds were ineffective in influencing how the replenishment rate decreases during long, high frequency stimulation. In conclusion at the excitatory synapses of rat hippocampus the replenishment of the readily releasable pool does not appear to be associated with a significant vesicular movement, and during long high frequency stimulation [Ca(++)]o does not influence the progressive decrease of vesicular replenishment.
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Affiliation(s)
- Loc Bui
- Department of Physiology, McGill University, 3655 Sir William Osler Promenade, Montreal, H3G 1Y6 Canada
| | - Mladen I Glavinović
- Department of Physiology, McGill University, 3655 Sir William Osler Promenade, Montreal, H3G 1Y6 Canada
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Zhang Z, Takeuchi H, Gao J, Wang D, James DJ, Martin TFJ, Hirata M. PRIP (phospholipase C-related but catalytically inactive protein) inhibits exocytosis by direct interactions with syntaxin 1 and SNAP-25 through its C2 domain. J Biol Chem 2013; 288:7769-7780. [PMID: 23341457 DOI: 10.1074/jbc.m112.419317] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane fusion for exocytosis is mediated by SNAREs, forming trans-ternary complexes to bridge vesicle and target membranes. There is an array of accessory proteins that directly interact with and regulate SNARE proteins. PRIP (phospholipase C-related but catalytically inactive protein) is likely one of these proteins; PRIP, consisting of multiple functional modules including pleckstrin homology and C2 domains, inhibited exocytosis, probably via the binding to membrane phosphoinositides through the pleckstrin homology domain. However, the roles of the C2 domain have not yet been investigated. In this study, we found that the C2 domain of PRIP directly interacts with syntaxin 1 and SNAP-25 but not with VAMP2. The C2 domain promoted PRIP to co-localize with syntaxin 1 and SNAP-25 in PC12 cells. The binding profile of the C2 domain to SNAP-25 was comparable with that of synaptotagmin I, and PRIP inhibited synaptotagmin I in binding to SNAP-25 and syntaxin 1. It was also shown that the C2 domain was required for PRIP to suppress SDS-resistant ternary SNARE complex formation and inhibit high K(+)-induced noradrenalin release from PC12 cells. These results suggest that PRIP inhibits regulated exocytosis through the interaction of its C2 domain with syntaxin 1 and SNAP-25, potentially competing with other SNARE-binding, C2 domain-containing accessory proteins such as synaptotagmin I and by directly inhibiting trans-SNARE complex formation.
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Affiliation(s)
- Zhao Zhang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Stomatological Hospital of Hebei Medical University, Shijiazhuang 050017, China
| | - Hiroshi Takeuchi
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Division of Applied Pharmacology, Kyushu Dental College, Kitakyushu 803-8580, Japan.
| | - Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - DaGuang Wang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Declan J James
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
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Multiple roles for the actin cytoskeleton during regulated exocytosis. Cell Mol Life Sci 2012; 70:2099-121. [PMID: 22986507 DOI: 10.1007/s00018-012-1156-5] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/28/2012] [Accepted: 08/30/2012] [Indexed: 01/01/2023]
Abstract
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e., secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane, and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules.
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Abstract
Different types of synapses are specialized to interpret spike trains in their own way by virtue of the complement of short-term synaptic plasticity mechanisms they possess. Numerous types of short-term, use-dependent synaptic plasticity regulate neurotransmitter release. Short-term depression is prominent after a single conditioning stimulus and recovers in seconds. Sustained presynaptic activation can result in more profound depression that recovers more slowly. An enhancement of release known as facilitation is prominent after single conditioning stimuli and lasts for hundreds of milliseconds. Finally, tetanic activation can enhance synaptic strength for tens of seconds to minutes through processes known as augmentation and posttetantic potentiation. Progress in clarifying the properties, mechanisms, and functional roles of these forms of short-term plasticity is reviewed here.
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Affiliation(s)
- Wade G Regehr
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Deak F, Sonntag WE. Aging, synaptic dysfunction, and insulin-like growth factor (IGF)-1. J Gerontol A Biol Sci Med Sci 2012; 67:611-25. [PMID: 22503992 PMCID: PMC3348499 DOI: 10.1093/gerona/gls118] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 03/16/2012] [Indexed: 01/05/2023] Open
Abstract
Insulin-like growth factor (IGF)-1 is an important neurotrophic hormone. Deficiency of this hormone has been reported to influence the genesis of cognitive impairment and dementia in the elderly patients. Nevertheless, there are studies indicating that cognitive function can be maintained into old age even in the absence of circulating IGF-1 and studies that link IGF-1 to an acceleration of neurological diseases. Although IGF-1 has a complex role in brain function, synaptic effects appear to be central to the IGF-1-induced improvement in learning and memory. In this review, synaptic mechanisms of learning and memory and the effects of IGF-1 on synaptic communication are discussed. The emerging data indicate that synaptic function decreases with age and that IGF-1 contributes to information processing in the brain. Further studies that detail the specific actions of this important neurotrophic hormone will likely lead to therapies that result in improved cognitive function for the elderly patients.
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Affiliation(s)
- Ferenc Deak
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida
| | - William E. Sonntag
- Reynolds Oklahoma Center on Aging, Donald W. Reynolds Department of Geriatric Medicine, Oklahoma City, Oklahoma
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Raingo J, Khvotchev M, Liu P, Darios F, Li YC, Ramirez DMO, Adachi M, Lemieux P, Toth K, Davletov B, Kavalali ET. VAMP4 directs synaptic vesicles to a pool that selectively maintains asynchronous neurotransmission. Nat Neurosci 2012; 15:738-45. [PMID: 22406549 PMCID: PMC3337975 DOI: 10.1038/nn.3067] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 02/07/2012] [Indexed: 01/07/2023]
Abstract
Synaptic vesicles in the brain harbor several soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins. With the exception of synaptobrevin2, or VAMP2 (syb2), which is directly involved in vesicle fusion, the role of these SNAREs in neurotransmission is unclear. Here we show that in mice syb2 drives rapid Ca(2+)-dependent synchronous neurotransmission, whereas the structurally homologous SNARE protein VAMP4 selectively maintains bulk Ca(2+)-dependent asynchronous release. At inhibitory nerve terminals, up- or downregulation of VAMP4 causes a correlated change in asynchronous release. Biochemically, VAMP4 forms a stable complex with SNAREs syntaxin-1 and SNAP-25 that does not interact with complexins or synaptotagmin-1, proteins essential for synchronous neurotransmission. Optical imaging of individual synapses indicates that trafficking of VAMP4 and syb2 show minimal overlap. Taken together, these findings suggest that VAMP4 and syb2 diverge functionally, traffic independently and support distinct forms of neurotransmission. These results provide molecular insight into how synapses diversify their release properties by taking advantage of distinct synaptic vesicle-associated SNAREs.
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Affiliation(s)
- Jesica Raingo
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Koch M, Holt M. Coupling exo- and endocytosis: an essential role for PIP₂ at the synapse. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1114-32. [PMID: 22387937 DOI: 10.1016/j.bbalip.2012.02.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Revised: 02/12/2012] [Accepted: 02/13/2012] [Indexed: 12/24/2022]
Abstract
Chemical synapses are specialist points of contact between two neurons, where information transfer takes place. Communication occurs through the release of neurotransmitter substances from small synaptic vesicles in the presynaptic terminal, which fuse with the presynaptic plasma membrane in response to neuronal stimulation. However, as neurons in the central nervous system typically only possess ~200 vesicles, high levels of release would quickly lead to a depletion in the number of vesicles, as well as leading to an increase in the area of the presynaptic plasma membrane (and possible misalignment with postsynaptic structures). Hence, synaptic vesicle fusion is tightly coupled to a local recycling of synaptic vesicles. For a long time, however, the exact molecular mechanisms coupling fusion and subsequent recycling remained unclear. Recent work now indicates a unique role for the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), acting together with the vesicular protein synaptotagmin, in coupling these two processes. In this work, we review the evidence for such a mechanism and discuss both the possible advantages and disadvantages for vesicle recycling (and hence signal transduction) in the nervous system. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Marta Koch
- Laboratory of Neurogenetics, VIB Center for the Biology of Disease and K.U. Leuven Center for Human Genetics, O&N4 Herestraat 49, 3000 Leuven, Belgium
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Gustavsson N, Wu B, Han W. Calcium sensing in exocytosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:731-57. [PMID: 22453967 DOI: 10.1007/978-94-007-2888-2_32] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Neurotransmitters, neuropeptides and hormones are released through regulated exocytosis of synaptic vesicles and large dense core vesicles. This complex and highly regulated process is orchestrated by SNAREs and their associated proteins. The triggering signal for regulated exocytosis is usually an increase in intracellular calcium levels. Besides the triggering role, calcium signaling modulates the precise amount and kinetics of vesicle release. Thus, it is a central question to understand the molecular machineries responsible for calcium sensing in exocytosis. Here we provide an overview of our current understanding of calcium sensing in neurotransmitter release and hormone secretion.
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Affiliation(s)
- Natalia Gustavsson
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore.
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