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Imoto Y, Raychaudhuri S, Ma Y, Fenske P, Sandoval E, Itoh K, Blumrich EM, Matsubayashi HT, Mamer L, Zarebidaki F, Söhl-Kielczynski B, Trimbuch T, Nayak S, Iwasa JH, Liu J, Wu B, Ha T, Inoue T, Jorgensen EM, Cousin MA, Rosenmund C, Watanabe S. Dynamin is primed at endocytic sites for ultrafast endocytosis. Neuron 2022; 110:2815-2835.e13. [PMID: 35809574 PMCID: PMC9464723 DOI: 10.1016/j.neuron.2022.06.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 03/24/2022] [Accepted: 06/09/2022] [Indexed: 02/06/2023]
Abstract
Dynamin mediates fission of vesicles from the plasma membrane during endocytosis. Typically, dynamin is recruited from the cytosol to endocytic sites, requiring seconds to tens of seconds. However, ultrafast endocytosis in neurons internalizes vesicles as quickly as 50 ms during synaptic vesicle recycling. Here, we demonstrate that Dynamin 1 is pre-recruited to endocytic sites for ultrafast endocytosis. Specifically, Dynamin 1xA, a splice variant of Dynamin 1, interacts with Syndapin 1 to form molecular condensates on the plasma membrane. Single-particle tracking of Dynamin 1xA molecules confirms the liquid-like property of condensates in vivo. When Dynamin 1xA is mutated to disrupt its interaction with Syndapin 1, the condensates do not form, and consequently, ultrafast endocytosis slows down by 100-fold. Mechanistically, Syndapin 1 acts as an adaptor by binding the plasma membrane and stores Dynamin 1xA at endocytic sites. This cache bypasses the recruitment step and accelerates endocytosis at synapses.
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Affiliation(s)
- Yuuta Imoto
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA.
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Ye Ma
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Pascal Fenske
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Eduardo Sandoval
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Kie Itoh
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Eva-Maria Blumrich
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK; The Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK; Simons Initiatives for the Developing Brain, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK
| | - Hideaki T Matsubayashi
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA; The Center for Cell Dynamics, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Lauren Mamer
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Fereshteh Zarebidaki
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | | | - Thorsten Trimbuch
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Shraddha Nayak
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Janet H Iwasa
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Jian Liu
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK
| | - Bin Wu
- The Center for Cell Dynamics, Johns Hopkins University, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21205, USA; Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Taekjip Ha
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA; Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Baltimore, MD 21205, USA
| | - Takanari Inoue
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA; The Center for Cell Dynamics, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Erik M Jorgensen
- HHMI, Department of Biology, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK; The Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK; Simons Initiatives for the Developing Brain, University of Edinburgh, Edinburgh, Scotland EH8 9XD, UK
| | - Christian Rosenmund
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA; The Center for Cell Dynamics, Johns Hopkins University, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21205, USA.
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FMRP Sustains Presynaptic Function via Control of Activity-Dependent Bulk Endocytosis. J Neurosci 2022; 42:1618-1628. [PMID: 34996816 PMCID: PMC8883869 DOI: 10.1523/jneurosci.0852-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 12/22/2021] [Accepted: 12/23/2021] [Indexed: 11/21/2022] Open
Abstract
Synaptic vesicle (SV) recycling is essential for the maintenance of neurotransmission, with a number of neurodevelopmental disorders linked to defects in this process. Fragile X syndrome (FXS) results from a loss of fragile X mental retardation protein (FMRP) encoded by the FMR1 gene. Hyperexcitability of neuronal circuits is a key feature of FXS, therefore we investigated whether SV recycling was affected by the absence of FMRP during increased neuronal activity. We revealed that primary neuronal cultures from male Fmr1 knock-out (KO) rats display a specific defect in activity-dependent bulk endocytosis (ADBE). ADBE is dominant during intense neuronal activity, and this defect resulted in an inability of Fmr1 KO neurons to sustain SV recycling during trains of high-frequency stimulation. Using a molecular replacement strategy, we also revealed that a human FMRP mutant that cannot bind BK channels failed to correct ADBE dysfunction in KO neurons, however this dysfunction was corrected by BK channel agonists. Therefore, FMRP performs a key role in sustaining neurotransmitter release via selective control of ADBE, suggesting intervention via this endocytosis mode may correct the hyperexcitability observed in FXS.SIGNIFICANCE STATEMENT Loss of fragile X mental retardation protein (FMRP) results in fragile X syndrome (FXS), however whether its loss has a direct role in neurotransmitter release remains a matter of debate. We demonstrate that neurons lacking FMRP display a specific defect in a mechanism that sustains neurotransmitter release during intense neuronal firing, called activity-dependent bulk endocytosis (ADBE). This discovery provides key insights into mechanisms of brain communication that occur because of loss of FMRP function. Importantly it also reveals ADBE as a potential therapeutic target to correct the circuit hyperexcitability observed in FXS.
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Gaddam RR, Kim Y, Jacobs JS, Yoon J, Li Q, Cai A, Shankaiahgari H, London B, Irani K, Vikram A. The microRNA-204-5p inhibits APJ signalling and confers resistance to cardiac hypertrophy and dysfunction. Clin Transl Med 2022; 12:e693. [PMID: 35060347 PMCID: PMC8777385 DOI: 10.1002/ctm2.693] [Citation(s) in RCA: 2] [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: 10/18/2021] [Revised: 11/29/2021] [Accepted: 12/16/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND MicroRNAs regulate cardiac hypertrophy development, which precedes and predicts the risk of heart failure. microRNA-204-5p (miR-204) is well expressed in cardiomyocytes, but its role in developing cardiac hypertrophy and cardiac dysfunction (CH/CD) remains poorly understood. METHODS We performed RNA-sequencing, echocardiographic, and molecular/morphometric analysis of the heart of mice lacking or overexpressing miR-204 five weeks after trans-aortic constriction (TAC). The neonatal rat cardiomyocytes, H9C2, and HEK293 cells were used to determine the mechanistic role of miR-204. RESULTS The stretch induces miR-204 expression, and miR-204 inhibits the stretch-induced hypertrophic response of H9C2 cells. The mice lacking miR-204 displayed a higher susceptibility to CH/CD during pressure overload, which was reversed by the adeno-associated virus serotype-9-mediated cardioselective miR-204 overexpression. Bioinformatic analysis of the cardiac transcriptomics of miR-204 knockout mice following pressure overload suggested deregulation of apelin-receptor (APJ) signalling. We found that the stretch-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation and hypertrophy-related genes expression depend on the APJ, and both of these effects are subject to miR-204 levels. The dynamin inhibitor dynasore inhibited both stretch-induced APJ endocytosis and ERK1/2 activation. In contrast, the miR-204-induced APJ endocytosis was neither inhibited by dynamin inhibitors (dynasore and dyngo) nor associated with ERK1/2 activation. We find that the miR-204 increases the expression of ras-associated binding proteins (e.g., Rab5a, Rab7) that regulate cellular endocytosis. CONCLUSIONS Our results show that miR-204 regulates trafficking of APJ and confers resistance to pressure overload-induced CH/CD, and boosting miR-204 can inhibit the development of CH/CD.
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Affiliation(s)
- Ravinder Reddy Gaddam
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Young‐Rae Kim
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Julia S. Jacobs
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Jin‐Young Yoon
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Qiuxia Li
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Angela Cai
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Hamsitha Shankaiahgari
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Barry London
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Kaikobad Irani
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
| | - Ajit Vikram
- Department of Internal MedicineCarver College of Medicine University of IowaIowa CityIowaUSA
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4
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Wu C, Guo WB, Liu YY, Yang L, Miao AJ. Molecular mechanisms underlying the calcium-mediated uptake of hematite nanoparticles by the ciliate Tetrahymena thermophila. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 288:117749. [PMID: 34329064 DOI: 10.1016/j.envpol.2021.117749] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/21/2021] [Accepted: 07/06/2021] [Indexed: 06/13/2023]
Abstract
In aquatic ecosystems, the calcium (Ca) concentration varies greatly. It is well known that Ca affects the aggregation of nanoparticles (NPs) and thus their bioaccumulation. Nevertheless, Ca also plays critical roles in various biological processes, whose effects on NP accumulation in aquatic organisms remain unclear. In this study, the effects of Ca on the uptake of polyacrylate-coated hematite NPs (HemNPs) by the aquatic ciliate Tetrahymena thermophila were investigated. At all of the tested Ca concentrations, HemNPs were well dispersed in the experimental medium, excluding the possibility of Ca to influence HemNP bioaccumulation by aggregating the NPs. Instead, Ca was shown to induce the clathrin-mediated endocytosis and phagocytosis of HemNPs. Manipulation of the Ca speciation in the experimental medium as well as the influx and intracellular availability of Ca in T. thermophila indicated that HemNP uptake was regulated by the intracellular Ca level. The results of the proteomics analyses further showed that the binding of intracellular Ca to calmodulin altered the activity of proteins involved in clathrin-mediated endocytosis (calcineurin and dynamin) and phagocytosis (actin). Overall, the biologically inductive effects of Ca on NP accumulation in aquatic organisms should be considered when evaluating the environmental risks of NPs.
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Affiliation(s)
- Chao Wu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, 210023, China
| | - Wen-Bo Guo
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, 210023, China
| | - Yue-Yue Liu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, 210023, China
| | - Liuyan Yang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, 210023, China
| | - Ai-Jun Miao
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, 210023, China.
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5
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Harper CB, Blumrich EM, Cousin MA. Synaptophysin controls synaptobrevin-II retrieval via a cryptic C-terminal interaction site. J Biol Chem 2021; 296:100266. [PMID: 33769286 PMCID: PMC7948965 DOI: 10.1016/j.jbc.2021.100266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 01/03/2021] [Accepted: 01/06/2021] [Indexed: 12/22/2022] Open
Abstract
The accurate retrieval of synaptic vesicle (SV) proteins during endocytosis is essential for the maintenance of neurotransmission. Synaptophysin (Syp) and synaptobrevin-II (SybII) are the most abundant proteins on SVs. Neurons lacking Syp display defects in the activity-dependent retrieval of SybII and a general slowing of SV endocytosis. To determine the role of the cytoplasmic C terminus of Syp in the control of these two events, we performed molecular replacement studies in primary cultures of Syp knockout neurons using genetically encoded reporters of SV cargo trafficking at physiological temperatures. Under these conditions, we discovered, 1) no slowing in SV endocytosis in Syp knockout neurons, and 2) a continued defect in SybII retrieval in knockout neurons expressing a form of Syp lacking its C terminus. Sequential truncations of the Syp C-terminus revealed a cryptic interaction site for the SNARE motif of SybII that was concealed in the full-length form. This suggests that a conformational change within the Syp C terminus is key to permitting SybII binding and thus its accurate retrieval. Furthermore, this study reveals that the sole presynaptic role of Syp is the control of SybII retrieval, since no defect in SV endocytosis kinetics was observed at physiological temperatures.
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Affiliation(s)
- Callista B Harper
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK
| | - Eva-Maria Blumrich
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, Scotland, EH8 9XD, UK.
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6
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Alyenbaawi H, Kanyo R, Locskai LF, Kamali-Jamil R, DuVal MG, Bai Q, Wille H, Burton EA, Allison WT. Seizures are a druggable mechanistic link between TBI and subsequent tauopathy. eLife 2021; 10:58744. [PMID: 33527898 PMCID: PMC7853719 DOI: 10.7554/elife.58744] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 12/07/2020] [Indexed: 12/18/2022] Open
Abstract
Traumatic brain injury (TBI) is a prominent risk factor for dementias including tauopathies like chronic traumatic encephalopathy (CTE). The mechanisms that promote prion-like spreading of Tau aggregates after TBI are not fully understood, in part due to lack of tractable animal models. Here, we test the putative role of seizures in promoting the spread of tauopathy. We introduce ‘tauopathy reporter’ zebrafish expressing a genetically encoded fluorescent Tau biosensor that reliably reports accumulation of human Tau species when seeded via intraventricular brain injections. Subjecting zebrafish larvae to a novel TBI paradigm produced various TBI features including cell death, post–traumatic seizures, and Tau inclusions. Bath application of dynamin inhibitors or anticonvulsant drugs rescued TBI-induced tauopathy and cell death. These data suggest a role for seizure activity in the prion-like seeding and spreading of tauopathy following TBI. Further work is warranted regarding anti-convulsants that dampen post-traumatic seizures as a route to moderating subsequent tauopathy. Traumatic brain injury can result from direct head concussions, rapid head movements, or a blast wave generated by an explosion. Traumatic brain injury often causes seizures in the short term and is a risk factor for certain dementias, including Alzheimer’s disease and chronic traumatic encephalopathy in the long term. A protein called Tau undergoes a series of chemical changes in these dementias that makes it accumulate, form toxic filaments and kill neurons. The toxic abnormal Tau proteins are initially found only in certain regions of the brain, but they spread as the disease progresses. Previous studies in Alzheimer’s disease and other diseases where Tau proteins are abnormal suggest that Tau can spread between neighboring neurons and this can be promoted by neuron activity. However, scientists do not know whether similar mechanisms are at work following traumatic brain injury. Given that seizures are very common following traumatic brain injury, could they be partly responsible for promoting dementia? To investigate this, researchers need animal models in which they can measure neural activity associated with traumatic brain injury and observe the spread of abnormal Tau proteins. Alyenbaawi et al. engineered zebrafish so that their Tau proteins would be fluorescent, making it possible to track the accumulation of aggregated Tau protein in the brain. Next, they invented a simple way to perform traumatic brain injury on zebrafish larvae by using a syringe to produce a pressure wave. After this procedure, many of the fish exhibited features consistent with progression towards dementia, and seizure-like behaviors. The results showed that post-traumatic seizures are linked to the spread of aggregates of abnormal Tau following traumatic brain injury. Alyenbaawi et al. also found that anticonvulsant drugs can lower the levels of abnormal Tau proteins in neurons, preventing cell death, and could potentially ameliorate dementias associated with traumatic brain injury. These drugs are already being used to prevent post-traumatic epilepsy, but more research is needed to confirm whether they reduce the risk or severity of Tau-related neurodegeneration.
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Affiliation(s)
- Hadeel Alyenbaawi
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Medical Genetics, University of Alberta, Edmonton, Canada.,Majmaah University, Majmaah, Saudi Arabia
| | - Richard Kanyo
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - Laszlo F Locskai
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - Razieh Kamali-Jamil
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Biochemistry, University of Alberta, Edmonton, Canada
| | - Michèle G DuVal
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - Qing Bai
- Department of Neurology, University of Pittsburgh, Pittsburgh, United States
| | - Holger Wille
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Biochemistry, University of Alberta, Edmonton, Canada
| | - Edward A Burton
- Department of Neurology, University of Pittsburgh, Pittsburgh, United States.,Geriatric Research, Education and Clinical Center, Pittsburgh VA Healthcare System, Pittsburgh, United States
| | - W Ted Allison
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Canada.,Department of Medical Genetics, University of Alberta, Edmonton, Canada.,Department of Biological Sciences, University of Alberta, Edmonton, Canada
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7
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Cremer T, Neefjes J, Berlin I. The journey of Ca 2+ through the cell - pulsing through the network of ER membrane contact sites. J Cell Sci 2020; 133:133/24/jcs249136. [PMID: 33376155 DOI: 10.1242/jcs.249136] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Calcium is the third most abundant metal on earth, and the fundaments of its homeostasis date back to pre-eukaryotic life forms. In higher organisms, Ca2+ serves as a cofactor for a wide array of (enzymatic) interactions in diverse cellular contexts and constitutes the most important signaling entity in excitable cells. To enable responsive behavior, cytosolic Ca2+ concentrations are kept low through sequestration into organellar stores, particularly the endoplasmic reticulum (ER), but also mitochondria and lysosomes. Specific triggers are then used to instigate a local release of Ca2+ on demand. Here, communication between organelles comes into play, which is accomplished through intimate yet dynamic contacts, termed membrane contact sites (MCSs). The field of MCS biology in relation to cellular Ca2+ homeostasis has exploded in recent years. Taking advantage of this new wealth of knowledge, in this Review, we invite the reader on a journey of Ca2+ flux through the ER and its associated MCSs. New mechanistic insights and technological advances inform the narrative on Ca2+ acquisition and mobilization at these sites of communication between organelles, and guide the discussion of their consequences for cellular physiology.
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Affiliation(s)
- Tom Cremer
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
| | - Jacques Neefjes
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
| | - Ilana Berlin
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
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8
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Calcium Dyshomeostasis and Lysosomal Ca 2+ Dysfunction in Amyotrophic Lateral Sclerosis. Cells 2019; 8:cells8101216. [PMID: 31597311 PMCID: PMC6829585 DOI: 10.3390/cells8101216] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 09/24/2019] [Accepted: 10/03/2019] [Indexed: 12/11/2022] Open
Abstract
Recent findings in the understanding of amyotrophic lateral sclerosis (ALS) revealed that alteration in calcium (Ca2+) homeostasis may largely contribute to motor neuron demise. A large part of these alterations is due to dysfunctional Ca2+-storing organelles, including the endoplasmic reticulum (ER) and mitochondria. Very recently, lysosomal Ca2+ dysfunction has emerged as an important pathological change leading to neuronal loss in ALS. Remarkably, the Ca2+-storing organelles are interacting with each other at specialized domains controlling mitochondrial dynamics, ER/lysosomal function, and autophagy. This occurs as a result of interaction between specific ionic channels and Ca2+-dependent proteins located in each structure. Therefore, the dysregulation of these ionic mechanisms could be considered as a key element in the neurodegenerative process. This review will focus on the possible role of lysosomal Ca2+ dysfunction in the pathogenesis of several neurodegenerative diseases, including ALS and shed light on the possibility that specific lysosomal Ca2+ channels might represent new promising targets for preventing or at least delaying neurodegeneration in ALS.
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9
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Devine MJ, Kittler JT. Mitochondria at the neuronal presynapse in health and disease. Nat Rev Neurosci 2019; 19:63-80. [PMID: 29348666 DOI: 10.1038/nrn.2017.170] [Citation(s) in RCA: 333] [Impact Index Per Article: 66.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Synapses enable neurons to communicate with each other and are therefore a prerequisite for normal brain function. Presynaptically, this communication requires energy and generates large fluctuations in calcium concentrations. Mitochondria are optimized for supplying energy and buffering calcium, and they are actively recruited to presynapses. However, not all presynapses contain mitochondria; thus, how might synapses with and without mitochondria differ? Mitochondria are also increasingly recognized to serve additional functions at the presynapse. Here, we discuss the importance of presynaptic mitochondria in maintaining neuronal homeostasis and how dysfunctional presynaptic mitochondria might contribute to the development of disease.
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Affiliation(s)
- Michael J Devine
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Josef T Kittler
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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10
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Kelly MJ, Qiu J, Rønnekleiv OK. TRPCing around the hypothalamus. Front Neuroendocrinol 2018; 51:116-124. [PMID: 29859883 PMCID: PMC6175656 DOI: 10.1016/j.yfrne.2018.05.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 01/13/2023]
Abstract
All of the canonical transient receptor potential channels (TRPC) with the exception of TRPC 2 are expressed in hypothalamic neurons and are involved in multiple homeostatic functions. Although the metabotropic glutamate receptors have been shown to be coupled to TRPC channel activation in cortical and sub-cortical brain regions, in the hypothalamus multiple amine and peptidergic G protein-coupled receptors (GPCRs) and growth factor/cytokine receptors are linked to activation of TRPC channels that are vital for reproduction, temperature regulation, arousal and energy homeostasis. In addition to the neurotransmitters, circulating hormones like insulin and leptin through their cognate receptors activate TRPC channels in POMC neurons. Many of the post-synaptic effects of the neurotransmitters and hormones are regulated in different physiological states by expression of TRPC channels in the post-synaptic neurons. Therefore, TRPC channels are key targets not only for neurotransmitters but circulating hormones in their vital role to control multiple hypothalamic functions, which is the focus of this review.
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Affiliation(s)
- Martin J Kelly
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA; Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA.
| | - Jian Qiu
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA
| | - Oline K Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA; Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA
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11
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Qiu J, Rivera HM, Bosch MA, Padilla SL, Stincic TL, Palmiter RD, Kelly MJ, Rønnekleiv OK. Estrogenic-dependent glutamatergic neurotransmission from kisspeptin neurons governs feeding circuits in females. eLife 2018; 7:e35656. [PMID: 30079889 PMCID: PMC6103748 DOI: 10.7554/elife.35656] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 07/24/2018] [Indexed: 11/13/2022] Open
Abstract
The neuropeptides tachykinin2 (Tac2) and kisspeptin (Kiss1) in hypothalamic arcuate nucleus Kiss1 (Kiss1ARH) neurons are essential for pulsatile release of GnRH and reproduction. Since 17β-estradiol (E2) decreases Kiss1 and Tac2 mRNA expression in Kiss1ARH neurons, the role of Kiss1ARH neurons during E2-driven anorexigenic states and their coordination of POMC and NPY/AgRP feeding circuits have been largely ignored. Presently, we show that E2 augmented the excitability of Kiss1ARH neurons by amplifying Cacna1g, Hcn1 and Hcn2 mRNA expression and T-type calcium and h-currents. E2 increased Slc17a6 mRNA expression and glutamatergic synaptic input to arcuate neurons, which excited POMC and inhibited NPY/AgRP neurons via metabotropic receptors. Deleting Slc17a6 in Kiss1 neurons eliminated glutamate release and led to conditioned place preference for sucrose in E2-treated KO female mice. Therefore, the E2-driven increase in Kiss1 neuronal excitability and glutamate neurotransmission may play a key role in governing the motivational drive for palatable food in females.
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Affiliation(s)
- Jian Qiu
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
| | - Heidi M Rivera
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
| | - Martha A Bosch
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
| | - Stephanie L Padilla
- Department of BiochemistryHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
| | - Todd L Stincic
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
| | - Richard D Palmiter
- Department of BiochemistryHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
| | - Martin J Kelly
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
- Division of NeuroscienceOregon National Primate Research Center, Oregon Health and Science UniversityBeavertonUnited States
| | - Oline K Rønnekleiv
- Department of Physiology and PharmacologyOregon Health and Science UniversityPortlandUnited States
- Division of NeuroscienceOregon National Primate Research Center, Oregon Health and Science UniversityBeavertonUnited States
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12
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Florenzano F, Veronica C, Ciasca G, Ciotti MT, Pittaluga A, Olivero G, Feligioni M, Iannuzzi F, Latina V, Maria Sciacca MF, Sinopoli A, Milardi D, Pappalardo G, Marco DS, Papi M, Atlante A, Bobba A, Borreca A, Calissano P, Amadoro G. Extracellular truncated tau causes early presynaptic dysfunction associated with Alzheimer's disease and other tauopathies. Oncotarget 2017; 8:64745-64778. [PMID: 29029390 PMCID: PMC5630290 DOI: 10.18632/oncotarget.17371] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/11/2017] [Indexed: 12/14/2022] Open
Abstract
The largest part of tau secreted from AD nerve terminals and released in cerebral spinal fluid (CSF) is C-terminally truncated, soluble and unaggregated supporting potential extracellular role(s) of NH2 -derived fragments of protein on synaptic dysfunction underlying neurodegenerative tauopathies, including Alzheimer's disease (AD). Here we show that sub-toxic doses of extracellular-applied human NH2 tau 26-44 (aka NH 2 htau) -which is the minimal active moiety of neurotoxic 20-22kDa peptide accumulating in vivo at AD synapses and secreted into parenchyma- acutely provokes presynaptic deficit in K+ -evoked glutamate release on hippocampal synaptosomes along with alteration in local Ca2+ dynamics. Neuritic dystrophy, microtubules breakdown, deregulation in presynaptic proteins and loss of mitochondria located at nerve endings are detected in hippocampal cultures only after prolonged exposure to NH 2 htau. The specificity of these biological effects is supported by the lack of any significant change, either on neuronal activity or on cellular integrity, shown by administration of its reverse sequence counterpart which behaves as an inactive control, likely due to a poor conformational flexibility which makes it unable to dynamically perturb biomembrane-like environments. Our results demonstrate that one of the AD-relevant, soluble and secreted N-terminally truncated tau forms can early contribute to pathology outside of neurons causing alterations in synaptic activity at presynaptic level, independently of overt neurodegeneration.
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Affiliation(s)
| | | | - Gabriele Ciasca
- Institute of Physics, Catholic University of the Sacred Heart, Largo F Vito 1, Rome, Italy
| | - Maria Teresa Ciotti
- Institute of Cellular Biology and Neuroscience, CNR, IRCSS Santa Lucia Foundation, Rome, Italy
| | - Anna Pittaluga
- Department of Pharmacy, Pharmacology and Toxicology Section, University of Genoa, Genoa, Viale Cembrano, Italy
| | - Gunedalina Olivero
- Department of Pharmacy, Pharmacology and Toxicology Section, University of Genoa, Genoa, Viale Cembrano, Italy
| | - Marco Feligioni
- European Brain Research Institute, Rome, Italy
- Department of Neurorehabilitation Sciences, Casa Cura Policlinico, Milan, Italy
| | | | | | | | | | - Danilo Milardi
- Institute of Biostructures and Bioimaging, CNR, Catania, Italy
| | | | - De Spirito Marco
- Institute of Physics, Catholic University of the Sacred Heart, Largo F Vito 1, Rome, Italy
| | - Massimiliano Papi
- Institute of Physics, Catholic University of the Sacred Heart, Largo F Vito 1, Rome, Italy
| | - Anna Atlante
- Institute of Biomembranes and Bioenergetics, CNR, Bari, Italy
- Center of Excellence for Biomedical Research, University of Genoa, Genoa, Viale Benedetto XV, Italy
| | - Antonella Bobba
- Institute of Biomembranes and Bioenergetics, CNR, Bari, Italy
- Center of Excellence for Biomedical Research, University of Genoa, Genoa, Viale Benedetto XV, Italy
| | - Antonella Borreca
- Institute of Cellular Biology and Neuroscience, CNR, IRCSS Santa Lucia Foundation, Rome, Italy
| | | | - Giuseppina Amadoro
- European Brain Research Institute, Rome, Italy
- Institute of Translational Pharmacology, CNR, Rome, Italy
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13
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Wang YL, Zhang CX. Putting a brake on synaptic vesicle endocytosis. Cell Mol Life Sci 2017; 74:2917-2927. [PMID: 28361181 PMCID: PMC11107501 DOI: 10.1007/s00018-017-2506-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/14/2017] [Accepted: 03/14/2017] [Indexed: 01/16/2023]
Abstract
In chemical synapses, action potentials evoke synaptic vesicle fusion with the presynaptic membrane at the active zone to release neurotransmitter. Synaptic vesicle endocytosis (SVE) then follows exocytosis to recapture vesicle proteins and lipid components for recycling and the maintenance of membrane homeostasis. Therefore, SVE plays an essential role during neurotransmission and is one of the most precisely regulated biological processes. Four modes of SVE have been characterized and both positive and negative regulators have been identified. However, our understanding of SVE regulation remains unclear, especially the identity of negative regulators and their mechanisms of action. Here, we review the current knowledge of proteins that function as inhibitors of SVE and their modes of action in different forms of endocytosis. We also propose possible physiological roles of such negative regulation. We believe that a better understanding of SVE regulation, especially the inhibitory mechanisms, will shed light on neurotransmission in health and disease.
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Affiliation(s)
- Ya-Long Wang
- Center of Parkinson's Disease, Beijing Institute for Brain Disorders, Capital Medical University, Key Laboratory for the Neurodegenerative Disorders of the Chinese Ministry of Education, Beijing, China
| | - Claire Xi Zhang
- Center of Parkinson's Disease, Beijing Institute for Brain Disorders, Capital Medical University, Key Laboratory for the Neurodegenerative Disorders of the Chinese Ministry of Education, Beijing, China.
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14
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Sphingosine 1-phosphate lyase ablation disrupts presynaptic architecture and function via an ubiquitin- proteasome mediated mechanism. Sci Rep 2016; 6:37064. [PMID: 27883090 PMCID: PMC5121647 DOI: 10.1038/srep37064] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/24/2016] [Indexed: 01/28/2023] Open
Abstract
The bioactive lipid sphingosine 1-phosphate (S1P) is a degradation product of sphingolipids that are particularly abundant in neurons. We have shown previously that neuronal S1P accumulation is toxic leading to ER-stress and an increase in intracellular calcium. To clarify the neuronal function of S1P, we generated brain-specific knockout mouse models in which S1P-lyase (SPL), the enzyme responsible for irreversible S1P cleavage was inactivated. Constitutive ablation of SPL in the brain (SPLfl/fl/Nes) but not postnatal neuronal forebrain-restricted SPL deletion (SPLfl/fl/CaMK) caused marked accumulation of S1P. Hence, altered presynaptic architecture including a significant decrease in number and density of synaptic vesicles, decreased expression of several presynaptic proteins, and impaired synaptic short term plasticity were observed in hippocampal neurons from SPLfl/fl/Nes mice. Accordingly, these mice displayed cognitive deficits. At the molecular level, an activation of the ubiquitin-proteasome system (UPS) was detected which resulted in a decreased expression of the deubiquitinating enzyme USP14 and several presynaptic proteins. Upon inhibition of proteasomal activity, USP14 levels, expression of presynaptic proteins and synaptic function were restored. These findings identify S1P metabolism as a novel player in modulating synaptic architecture and plasticity.
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15
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Qiu J, Nestor CC, Zhang C, Padilla SL, Palmiter RD, Kelly MJ, Rønnekleiv OK. High-frequency stimulation-induced peptide release synchronizes arcuate kisspeptin neurons and excites GnRH neurons. eLife 2016; 5:e16246. [PMID: 27549338 PMCID: PMC4995096 DOI: 10.7554/elife.16246] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 07/18/2016] [Indexed: 12/19/2022] Open
Abstract
Kisspeptin (Kiss1) and neurokinin B (NKB) neurocircuits are essential for pubertal development and fertility. Kisspeptin neurons in the hypothalamic arcuate nucleus (Kiss1(ARH)) co-express Kiss1, NKB, dynorphin and glutamate and are postulated to provide an episodic, excitatory drive to gonadotropin-releasing hormone 1 (GnRH) neurons, the synaptic mechanisms of which are unknown. We characterized the cellular basis for synchronized Kiss1(ARH) neuronal activity using optogenetics, whole-cell electrophysiology, molecular pharmacology and single cell RT-PCR in mice. High-frequency photostimulation of Kiss1(ARH) neurons evoked local release of excitatory (NKB) and inhibitory (dynorphin) neuropeptides, which were found to synchronize the Kiss1(ARH) neuronal firing. The light-evoked synchronous activity caused robust excitation of GnRH neurons by a synaptic mechanism that also involved glutamatergic input to preoptic Kiss1 neurons from Kiss1(ARH) neurons. We propose that Kiss1(ARH) neurons play a dual role of driving episodic secretion of GnRH through the differential release of peptide and amino acid neurotransmitters to coordinate reproductive function.
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Affiliation(s)
- Jian Qiu
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, United States
| | - Casey C Nestor
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, United States
| | - Chunguang Zhang
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, United States
| | - Stephanie L Padilla
- Department of Biochemistry, Howard Hughes Medical Institute, University of Washington, Seattle, United States
| | - Richard D Palmiter
- Department of Biochemistry, Howard Hughes Medical Institute, University of Washington, Seattle, United States
| | - Martin J Kelly
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, United States
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, United States
| | - Oline K Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, United States
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, United States
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16
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Tan LY, Huang B, Xu S, Wei ZB, Yang LY, Miao AJ. TiO2 Nanoparticle Uptake by the Water Flea Daphnia magna via Different Routes is Calcium-Dependent. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:7799-7807. [PMID: 27359244 DOI: 10.1021/acs.est.6b01645] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Calcium plays versatile roles in aquatic ecosystems. In this study, we investigated its effects on the uptake of polyacrylate-coated TiO2 nanoparticles (PAA-TiO2-NPs) by the water flea (cladoceran) Daphnia magna. Particle distribution in these daphnids was also visualized using synchrotron radiation-based micro X-ray fluorescence spectroscopy, transmission electron microscopy, and scanning electron microscopy. At low ambient Ca concentrations in the experimental medium ([Ca]dis), PAA-TiO2-NPs were well dispersed and distributed throughout the daphnid; the particle concentration was highest in the abdominal zone and the gut, as a result of endocytosis and passive drinking of the nanoparticles, respectively. Further, Ca induced PAA-TiO2-NP uptake as a result of the increased Ca influx. At a high [Ca]dis, the PAA-TiO2-NPs formed micrometer-sized aggregates that were ingested by D. magna and concentrated only in its gut, independent of the Ca influx. Our results demonstrated the multiple effects of Ca on nanoparticle bioaccumulation. Specifically, well-dispersed nanoparticles were taken up by D. magna through endocytosis and passive drinking whereas the uptake of micrometer-sized aggregates relied on active ingestion.
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Affiliation(s)
- Ling-Yan Tan
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
| | - Bin Huang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
| | - Shen Xu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
| | - Zhong-Bo Wei
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
| | - Liu-Yan Yang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
| | - Ai-Jun Miao
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu Province 210023, China
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17
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Cano R, Tabares L. The Active and Periactive Zone Organization and the Functional Properties of Small and Large Synapses. Front Synaptic Neurosci 2016; 8:12. [PMID: 27252645 PMCID: PMC4877509 DOI: 10.3389/fnsyn.2016.00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/09/2016] [Indexed: 12/29/2022] Open
Abstract
The arrival of an action potential (AP) at a synaptic terminal elicits highly synchronized quanta release. Repetitive APs produce successive synaptic vesicle (SV) fusions that require management of spent SV components in the presynaptic membrane with minimum disturbance of the secretory apparatus. To this end, the synaptic machinery is structured accordingly to the strength and the range of frequencies at which each particular synapse operates. This results in variations in the number and dimension of Active Zones (AZs), amount and distribution of SVs, and probably, in the primary endocytic mechanisms they use. Understanding better how these structural differences determine the functional response in each case has been a matter of long-term interest. Here we review the structural and functional properties of three distinct types of synapses: the neuromuscular junction (NMJ; a giant, highly reliable synapse that must exocytose a large number of quanta with each stimulus to guarantee excitation of the postsynaptic cell), the hippocampal excitatory small synapse (which most often has a single release site and a relatively small pool of vesicles), and the cerebellar mossy fiber-granule cell synapse (which possesses hundreds of release sites and is able to translocate, dock and prime vesicles at high speed). We will focus on how the release apparatus is organized in each case, the relative amount of vesicular membrane that needs to be accommodated within the periAZ upon stimulation, the different mechanisms for retrieving the excess of membrane and finally, how these factors may influence the functioning of the release sites.
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Affiliation(s)
- Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
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18
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Nestor CC, Qiu J, Padilla SL, Zhang C, Bosch MA, Fan W, Aicher SA, Palmiter RD, Rønnekleiv OK, Kelly MJ. Optogenetic Stimulation of Arcuate Nucleus Kiss1 Neurons Reveals a Steroid-Dependent Glutamatergic Input to POMC and AgRP Neurons in Male Mice. Mol Endocrinol 2016; 30:630-44. [PMID: 27093227 DOI: 10.1210/me.2016-1026] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Kisspeptin (Kiss1) neurons are essential for reproduction, but their role in the control of energy balance and other homeostatic functions remains unclear. Proopiomelanocortin (POMC) and agouti-related peptide (AgRP) neurons, located in the arcuate nucleus (ARC) of the hypothalamus, integrate numerous excitatory and inhibitory inputs to ultimately regulate energy homeostasis. Given that POMC and AgRP neurons are contacted by Kiss1 neurons in the ARC (Kiss1(ARC)) and they express androgen receptors, Kiss1(ARC) neurons may mediate the orexigenic action of testosterone via POMC and/or AgRP neurons. Quantitative PCR analysis of pooled Kiss1(ARC) neurons revealed that mRNA levels for Kiss1 and vesicular glutamate transporter 2 were higher in castrated male mice compared with gonad-intact males. Single-cell RT-PCR analysis of yellow fluorescent protein (YFP) ARC neurons harvested from males injected with AAV1-EF1α-DIO-ChR2:YFP revealed that 100% and 88% expressed mRNAs for Kiss1 and vesicular glutamate transporter 2, respectively. Whole-cell, voltage-clamp recordings from nonfluorescent postsynaptic ARC neurons showed that low frequency photo-stimulation (0.5 Hz) of Kiss1-ChR2:YFP neurons elicited a fast glutamatergic inward current in POMC and AgRP neurons. Paired-pulse, photo-stimulation revealed paired-pulse depression, which is indicative of greater glutamate release, in the castrated male mice compared with gonad-intact male mice. Group I and group II metabotropic glutamate receptor agonists depolarized and hyperpolarized POMC and AgRP neurons, respectively, which was mimicked by high frequency photo-stimulation (20 Hz) of Kiss1(ARC) neurons. Therefore, POMC and AgRP neurons receive direct steroid- and frequency-dependent glutamatergic synaptic input from Kiss1(ARC) neurons in male mice, which may be a critical pathway for Kiss1 neurons to help coordinate energy homeostasis and reproduction.
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Affiliation(s)
- Casey C Nestor
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Jian Qiu
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Stephanie L Padilla
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Chunguang Zhang
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Martha A Bosch
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Wei Fan
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Sue A Aicher
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Richard D Palmiter
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Oline K Rønnekleiv
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
| | - Martin J Kelly
- Department of Physiology and Pharmacology (C.CN., J.Q., C.Z., M.A.B., S.A.A., O.K.R., M.J.K.) and Anesthesiology and Perioperative Medicine and Knight Cardiovascular Institute (W.F.), Oregon Health & Science University, Portland, Oregon 97239; Division of Neuroscience (O.K.R., M.J.K.), Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006; and Howard Hughes Medical Institute (S.L.P., R.D.P.), University of Washington, Seattle, Washington 98195
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19
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Marland JRK, Hasel P, Bonnycastle K, Cousin MA. Mitochondrial Calcium Uptake Modulates Synaptic Vesicle Endocytosis in Central Nerve Terminals. J Biol Chem 2015; 291:2080-6. [PMID: 26644474 PMCID: PMC4732196 DOI: 10.1074/jbc.m115.686956] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Indexed: 12/15/2022] Open
Abstract
Presynaptic calcium influx triggers synaptic vesicle (SV) exocytosis and modulates subsequent SV endocytosis. A number of calcium clearance mechanisms are present in central nerve terminals that regulate intracellular free calcium levels both during and after stimulation. During action potential stimulation, mitochondria rapidly accumulate presynaptic calcium via the mitochondrial calcium uniporter (MCU). The role of mitochondrial calcium uptake in modulating SV recycling has been debated extensively, but a definitive conclusion has not been achieved. To directly address this question, we manipulated the expression of the MCU channel subunit in primary cultures of neurons expressing a genetically encoded reporter of SV turnover. Knockdown of MCU resulted in ablation of activity-dependent mitochondrial calcium uptake but had no effect on the rate or extent of SV exocytosis. In contrast, the rate of SV endocytosis was increased in the absence of mitochondrial calcium uptake and slowed when MCU was overexpressed. MCU knockdown did not perturb activity-dependent increases in presynaptic free calcium, suggesting that SV endocytosis may be controlled by calcium accumulation and efflux from mitochondria in their immediate vicinity.
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Affiliation(s)
- Jamie Roslin Keynes Marland
- From the Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Philip Hasel
- From the Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Katherine Bonnycastle
- From the Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Michael Alan Cousin
- From the Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
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20
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Abstract
Ca(2+)-dependent synaptic vesicle recycling is essential for structural homeostasis of synapses and maintenance of neurotransmission. Although, the executive role of intrasynaptic Ca(2+) transients in synaptic vesicle exocytosis is well established, identifying the exact role of Ca(2+) in endocytosis has been difficult. In some studies, Ca(2+) has been suggested as an essential trigger required to initiate synaptic vesicle retrieval, whereas others manipulating synaptic Ca(2+) concentrations reported a modulatory role for Ca(2+) leading to inhibition or acceleration of endocytosis. Molecular studies of synaptic vesicle endocytosis, on the other hand, have consistently focused on the roles of Ca(2+)-calmodulin dependent phosphatase calcineurin and synaptic vesicle protein synaptotagmin as potential Ca(2+) sensors for endocytosis. Most studies probing the role of Ca(2+) in endocytosis have relied on measurements of synaptic vesicle retrieval after strong stimulation. Strong stimulation paradigms elicit fusion and retrieval of multiple synaptic vesicles and therefore can be affected by several factors besides the kinetics and duration of Ca(2+) signals that include the number of exocytosed vesicles and accumulation of released neurotransmitters thus altering fusion and retrieval processes indirectly via retrograde signaling. Studies monitoring single synaptic vesicle endocytosis may help resolve this conundrum as in these settings the impact of Ca(2+) on synaptic fusion probability can be uncoupled from its putative role on synaptic vesicle retrieval. Future experiments using these single vesicle approaches will help dissect the specific role(s) of Ca(2+) and its sensors in synaptic vesicle endocytosis.
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Affiliation(s)
- Jeremy Leitz
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, USA
| | - Ege T Kavalali
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, USA Department of Physiology, UT Southwestern Medical Center, Dallas, TX, USA
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21
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Morton A, Marland JRK, Cousin MA. Synaptic vesicle exocytosis and increased cytosolic calcium are both necessary but not sufficient for activity-dependent bulk endocytosis. J Neurochem 2015; 134:405-15. [PMID: 25913068 PMCID: PMC4950031 DOI: 10.1111/jnc.13132] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 03/23/2015] [Accepted: 03/30/2015] [Indexed: 01/22/2023]
Abstract
Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. By definition this mode is triggered by neuronal activity; however, key questions regarding its mechanism of activation remain unaddressed. To determine the basic requirements for ADBE triggering in central nerve terminals, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. ADBE was monitored both optically and morphologically by observing uptake of the fluid phase markers tetramethylrhodamine‐dextran and horse radish peroxidase respectively. Ablation of SV fusion with tetanus toxin resulted in the arrest of ADBE, but had no effect on other calcium‐dependent events such as activity‐dependent dynamin I dephosphorylation, indicating that SV exocytosis is necessary for triggering. Furthermore, the calcium chelator EGTA abolished ADBE while leaving SV exocytosis intact, demonstrating that ADBE is triggered by intracellular free calcium increases outside the active zone. Activity‐dependent dynamin I dephosphorylation was also arrested in EGTA‐treated neurons, consistent with its proposed role in triggering ADBE. Thus, SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient individually to trigger ADBE.![]() Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. To determine the minimal requirements for ADBE triggering, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. We found that SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient to trigger ADBE.
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Affiliation(s)
- Andrew Morton
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Jamie R K Marland
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
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22
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McCluskey A, Daniel JA, Hadzic G, Chau N, Clayton EL, Mariana A, Whiting A, Gorgani NN, Lloyd J, Quan A, Moshkanbaryans L, Krishnan S, Perera S, Chircop M, von Kleist L, McGeachie AB, Howes MT, Parton RG, Campbell M, Sakoff JA, Wang X, Sun JY, Robertson MJ, Deane FM, Nguyen TH, Meunier FA, Cousin MA, Robinson PJ. Building a better dynasore: the dyngo compounds potently inhibit dynamin and endocytosis. Traffic 2013; 14:1272-89. [PMID: 24025110 PMCID: PMC4138991 DOI: 10.1111/tra.12119] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 09/09/2013] [Accepted: 09/11/2013] [Indexed: 12/16/2022]
Abstract
Dynamin GTPase activity increases when it oligomerizes either into helices in the presence of lipid templates or into rings in the presence of SH3 domain proteins. Dynasore is a dynamin inhibitor of moderate potency (IC₅₀ ~ 15 μM in vitro). We show that dynasore binds stoichiometrically to detergents used for in vitro drug screening, drastically reducing its potency (IC₅₀ = 479 μM) and research tool utility. We synthesized a focused set of dihydroxyl and trihydroxyl dynasore analogs called the Dyngo™ compounds, five of which had improved potency, reduced detergent binding and reduced cytotoxicity, conferred by changes in the position and/or number of hydroxyl substituents. The Dyngo compound 4a was the most potent compound, exhibiting a 37-fold improvement in potency over dynasore for liposome-stimulated helical dynamin activity. In contrast, while dynasore about equally inhibited dynamin assembled in its helical or ring states, 4a and 6a exhibited >36-fold reduced activity against rings, suggesting that they can discriminate between helical or ring oligomerization states. 4a and 6a inhibited dynamin-dependent endocytosis of transferrin in multiple cell types (IC₅₀ of 5.7 and 5.8 μM, respectively), at least sixfold more potently than dynasore, but had no effect on dynamin-independent endocytosis of cholera toxin. 4a also reduced synaptic vesicle endocytosis and activity-dependent bulk endocytosis in cultured neurons and synaptosomes. Overall, 4a and 6a are improved and versatile helical dynamin and endocytosis inhibitors in terms of potency, non-specific binding and cytotoxicity. The data further suggest that the ring oligomerization state of dynamin is not required for clathrin-mediated endocytosis.
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Affiliation(s)
- Adam McCluskey
- Chemistry, Centre for Chemical Biology, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308, Australia
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23
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McGeachie AB, Odell LR, Quan A, Daniel JA, Chau N, Hill TA, Gorgani NN, Keating DJ, Cousin MA, van Dam EM, Mariana A, Whiting A, Perera S, Novelle A, Young KA, Deane FM, Gilbert J, Sakoff JA, Chircop M, McCluskey A, Robinson PJ. Pyrimidyn compounds: dual-action small molecule pyrimidine-based dynamin inhibitors. ACS Chem Biol 2013; 8:1507-18. [PMID: 23642287 DOI: 10.1021/cb400137p] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Dynamin is required for clathrin-mediated endocytosis (CME). Its GTPase activity is stimulated by phospholipid binding to its PH domain, which induces helical oligomerization. We have designed a series of novel pyrimidine-based "Pyrimidyn" compounds that inhibit the lipid-stimulated GTPase activity of full length dynamin I and II with similar potency. The most potent analogue, Pyrimidyn 7, has an IC50 of 1.1 μM for dynamin I and 1.8 μM for dynamin II, making it among the most potent dynamin inhibitors identified to date. We investigated the mechanism of action of the Pyrimidyn compounds in detail by examining the kinetics of Pyrimidyn 7 inhibition of dynamin. The compound competitively inhibits both GTP and phospholipid interactions with dynamin I. While both mechanisms of action have been previously observed separately, this is the first inhibitor series to incorporate both and thereby to target two distinct domains of dynamin. Pyrimidyn 6 and 7 reversibly inhibit CME of both transferrin and EGF in a number of non-neuronal cell lines as well as inhibiting synaptic vesicle endocytosis (SVE) in nerve terminals. Therefore, Pyrimidyn compounds block endocytosis by directly competing with GTP and lipid binding to dynamin, limiting both the recruitment of dynamin to membranes and its activation. This dual mode of action provides an important new tool for molecular dissection of dynamin's role in endocytosis.
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Affiliation(s)
- Andrew B. McGeachie
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Luke R. Odell
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | - Annie Quan
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - James A. Daniel
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Ngoc Chau
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Timothy A. Hill
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | - Nick N. Gorgani
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Damien J. Keating
- Department of Human Physiology, Flinders University, Adelaide, South Australia, 5001,
Australia
| | - Michael A. Cousin
- Department of Human Physiology, Flinders University, Adelaide, South Australia, 5001,
Australia
| | - Ellen M. van Dam
- The Garvan Institute, 384 Victoria Street,
Darlinghurst, Sydney, NSW 2010, Australia
| | - Anna Mariana
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | | | - Swetha Perera
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Aimee Novelle
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Kelly A. Young
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | - Fiona M. Deane
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | - Jayne Gilbert
- Department
of Medical Oncology, Calvary Mater Newcastle Hospital, Waratah, NSW 2298,
Australia
| | - Jennette A. Sakoff
- Department
of Medical Oncology, Calvary Mater Newcastle Hospital, Waratah, NSW 2298,
Australia
| | - Megan Chircop
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
| | - Adam McCluskey
- Centre for Chemical Biology,
Chemistry, The University of Newcastle,
Callaghan, NSW 2308, Australia
| | - Phillip J. Robinson
- Cell Signalling Unit, Children’s
Medical Research Institute, The University of Sydney, Sydney, NSW 2145, Australia
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24
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Daniel JA, Malladi CS, Kettle E, McCluskey A, Robinson PJ. Analysis of synaptic vesicle endocytosis in synaptosomes by high-content screening. Nat Protoc 2012; 7:1439-55. [PMID: 22767087 DOI: 10.1038/nprot.2012.070] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Small molecules modulating synaptic vesicle endocytosis (SVE) may ultimately be useful for diseases where pathological neurotransmission is implicated. Only a small number of specific SVE modulators have been identified to date. Slow progress is due to the laborious nature of traditional approaches to study SVE, in which nerve terminals are identified and studied in cultured neurons, typically yielding data from 10-20 synapses per experiment. We provide a protocol for a quantitative, high-throughput method for studying SVE in thousands of nerve terminals. Rat forebrain synaptosomes are attached to 96-well microplates and depolarized; SVE is then quantified by uptake of the dye FM4-64, which is imaged by high-content screening. Synaptosomes that have been frozen and stored can be used in place of fresh synaptosomes, reducing the experimental time and animal numbers required. With a supply of frozen synaptosomes, the assay can be performed within a day, including data analysis.
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Affiliation(s)
- James A Daniel
- Cell Signalling Unit, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
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25
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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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26
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Wu H, Gao SB, Sakurai T, Terakawa S. Fucoidan suppresses endocytosis in cultured HeLa cells. Chin J Integr Med 2011. [PMID: 21853347 DOI: 10.1007/s11655-011-0797-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Indexed: 10/17/2022]
Abstract
OBJECTIVE: To evaluate the effects of fucoidan on endocytosis in cultured HeLa cells: in vitro using live cell imaging. METHODS: A confocal scanning system and an incubation imaging system were used to: observe the effects of fucoidan on the initial (6 h) stages of endocytosis using the fl uorescent probe FM1-43 and inorganic fl uorescent quantum dot (Q-dots). RESULTS: According to the time-lapse images, fucoidan inhibited the: formation of endocytic vesicles in HeLa cells, in which the FM1-43 dye was entrapped. Fucoidan also had an inhibitory effect on the uptake of the Q-dots by the cell membranes of HeLa cells. CONCLUSION: It was concluded: that fucoidan suppresses Ca(2+)-dependent endocytosis in HeLa cells, which may be caused by its inhibitory -effects on agonist-induced Ca(2+) responses.
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Affiliation(s)
- Hong Wu
- The laboratory of Cell Imaging, Henan College of Traditional Chinese Medicine, Zhengzhou, 450002, China,
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27
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Li HD, Liu WX, Michalak M. Enhanced clathrin-dependent endocytosis in the absence of calnexin. PLoS One 2011; 6:e21678. [PMID: 21747946 PMCID: PMC3128601 DOI: 10.1371/journal.pone.0021678] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 06/08/2011] [Indexed: 12/24/2022] Open
Abstract
Background Calnexin, together with calreticulin, constitute the calnexin/calreticulin cycle. Calnexin is a type I endoplasmic reticulum integral membrane protein and molecular chaperone responsible for the folding and quality control of newly-synthesized (glyco)proteins. The endoplasmic reticulum luminal domain of calnexin is responsible for lectin-like activity and interaction with nascent polypeptide chains. The role of the C-terminal, cytoplasmic portion of calnexin is not clear. Methodology/Principal Findings Using yeast two hybrid screen and immunoprecipitation techniques, we showed that the Src homology 3-domain growth factor receptor-bound 2-like (Endophilin) interacting protein 1 (SGIP1), a neuronal specific regulator of endocytosis, forms complexes with the C-terminal cytoplasmic domain of calnexin. The calnexin cytoplasmic C-tail interacts with SGIP1 C-terminal domains containing the adaptor complexes medium subunit (Adap-Comp-Sub) region. Calnexin-deficient cells have enhanced clathrin-dependent endocytosis in neuronal cells and mouse neuronal system. This is reversed by expression of full length calnexin or calnexin C-tail. Conclusions/Significance We show that the effects of SGIP1 and calnexin C-tail on clathrin-dependent endocytosis are due to modulation of the internalization of the receptor-ligand complexes. Enhanced clathrin-dependent endocytosis in the absence of calnexin may contribute to the neurological phenotype of calnexin-deficient mice.
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Affiliation(s)
- Hao-Dong Li
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Wen-Xin Liu
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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28
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Budzinski KL, Sgro AE, Fujimoto BS, Gadd JC, Shuart NG, Gonen T, Bajjaleih SM, Chiu DT. Synaptosomes as a platform for loading nanoparticles into synaptic vesicles. ACS Chem Neurosci 2011; 2:236-241. [PMID: 21666849 DOI: 10.1021/cn200009n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Synaptosomes are intact, isolated nerve terminals that contain the necessary machinery to recycle synaptic vesicles via endocytosis and exocytosis upon stimulation. Here we use this property of synaptosomes to load quantum dots into synaptic vesicles. Vesicles are then isolated from the synaptosomes, providing a method to probe isolated, individual synaptic vesicles where each vesicle contains a single, encapsulated nanoparticle. This technique provided an encapsulation efficiency of ~16%, that is, ~16% of the vesicles contained a single quantum dot while the remaining vesicles were empty. The ability to load single nanoparticles into synaptic vesicles opens new opportunity for employing various nanoparticle-based sensors to study the dynamics of vesicular transporters.
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Affiliation(s)
- Kristi L. Budzinski
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Allyson E. Sgro
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Bryant S. Fujimoto
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Jennifer C. Gadd
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Noah G. Shuart
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Tamir Gonen
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Sandra M. Bajjaleih
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
| | - Daniel T. Chiu
- Department of Chemistry, ‡Department of Biochemistry Biochemistry, §Howard Hughes Medical Institute, and ∥Department of Pharmacology, University of Washington, Seattle, Washington 98195-1700, United States
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29
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Song HO, Lee J, Ji YJ, Dwivedi M, Cho JH, Park BJ, Ahnn J. Calcineurin regulates coelomocyte endocytosis via DYN-1 and CUP-4 in Caenorhabditis elegans. Mol Cells 2010; 30:255-62. [PMID: 20803083 DOI: 10.1007/s10059-010-0116-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 05/30/2010] [Accepted: 06/01/2010] [Indexed: 12/31/2022] Open
Abstract
C. elegans coelomocytes are macrophage-like scavenger cells that provide an excellent in vivo system for the study of clathrin-mediated endocytosis. Using this in vivo system, several genes involved in coelomocyte endocytosis have been identified previously. However, the detailed mechanism of endocytic pathway is still unknown. Here, we report a new function of calcineurin, an evolutionarily conserved Ca(2+)/calmodulin-dependent Ser/Thr protein phosphatase, in coelomocyte endocytosis. We found that calcineurin mutants show defective coelomocyte endocytosis. Genetic analysis suggests that calcineurin and a GTPase, dynamin (DYN-1), may function upstream of an orphan receptor, CUP-4, to regulate endocytosis. Therefore, we propose a model in which calcineurin may regulate coelomocyte endocytosis via DYN-1 and CUP-4 in C. elegans.
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Affiliation(s)
- Hyun-Ok Song
- Department of Life Science, College of Natural Sciences, Hanyang University, Seoul, 133-791, Korea
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30
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de Groot T, Verkaart S, Xi Q, Bindels RJM, Hoenderop JGJ. The identification of Histidine 712 as a critical residue for constitutive TRPV5 internalization. J Biol Chem 2010; 285:28481-7. [PMID: 20628046 DOI: 10.1074/jbc.m110.117143] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The epithelial Ca(2+) channel TRPV5 constitutes the apical entry gate for Ca(2+) transport in renal epithelial cells. Ablation of the trpv5 gene in mice leads to a reduced Ca(2+) reabsorption. TRPV5 is tightly regulated by various calciotropic hormones, associated proteins, and other factors, which mainly affect channel activity via the C terminus. To further identify the role of the C terminus in TRPV5 regulation, we expressed channels harboring C-terminal deletions and studied channel activity by measuring intracellular Ca(2+) concentration ([Ca(2+)](i)) using fura-2 analysis. Removal of amino acid His(712) elevated the [Ca(2+)](i), indicating enlarged TRPV5 activity. In addition, substitution of the positively charged His(712) for a negative (H712D) or neutral (H712N) amino acid also stimulated TRPV5 activity. This critical role of His(712) was confirmed by patch clamp analysis, which demonstrates increased Na(+) and Ca(2+) currents for TRPV5-H712D. Cell surface biotinylation studies revealed enhanced plasma membrane expression of TRPV5-H712D as compared with wild-type (WT) TRPV5. This elevated plasma membrane presence also was observed with the Ca(2+)-impermeable TRPV5-H712D and TRPV5-WT pore mutants, demonstrating that the elevation is not due to the increased [Ca(2+)](i). Finally, using an internalization assay, we demonstrated a delayed cell surface retrieval for TRPV5-H712D, likely causing the increase in plasma membrane expression. Together, these results demonstrate that His(712) plays an essential role in plasma membrane regulation of TRPV5 via a constitutive endocytotic mechanism.
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Affiliation(s)
- Theun de Groot
- Department of Physiology, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
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31
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Dynamin 2 and human diseases. J Mol Med (Berl) 2010; 88:339-50. [PMID: 20127478 DOI: 10.1007/s00109-009-0587-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 12/21/2009] [Accepted: 12/25/2009] [Indexed: 10/25/2022]
Abstract
Dynamin 2 (DNM2) mutations cause autosomal dominant centronuclear myopathy, a rare form of congenital myopathy, and intermediate and axonal forms of Charcot-Marie-Tooth disease, a peripheral neuropathy. DNM2 is a large GTPase mainly involved in membrane trafficking through its function in the formation and release of nascent vesicles from biological membranes. DNM2 participates in clathrin-dependent and clathrin-independent endocytosis and intracellular membrane trafficking (from endosomes and Golgi apparatus). Recent studies have also implicated DNM2 in exocytosis. DNM2 belongs to the machinery responsible for the formation of vesicles and regulates the cytoskeleton providing intracellular vesicle transport. In addition, DNM2 tightly interacts with and is involved in the regulation of actin and microtubule networks, independent from membrane trafficking processes. We summarize here the molecular, biochemical, and functional data on DNM2 and discuss the possible pathophysiological mechanisms via which DNM2 mutations can lead to two distinct neuromuscular disorders.
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32
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Perforin activates clathrin- and dynamin-dependent endocytosis, which is required for plasma membrane repair and delivery of granzyme B for granzyme-mediated apoptosis. Blood 2009; 115:1582-93. [PMID: 20038786 DOI: 10.1182/blood-2009-10-246116] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytotoxic T lymphocytes and natural killer cells destroy target cells via the polarized exocytosis of lytic effector proteins, perforin and granzymes, into the immunologic synapse. How these molecules enter target cells is not fully understood. It is debated whether granzymes enter via perforin pores formed at the plasma membrane or whether perforin and granzymes are first endocytosed and granzymes are then released from endosomes into the cytoplasm. We previously showed that perforin disruption of the plasma membrane induces a transient Ca(2+) flux into the target cell that triggers a wounded membrane repair response in which lysosomes and endosomes donate their membranes to reseal the damaged membrane. Here we show that perforin activates clathrin- and dynamin-dependent endocytosis, which removes perforin and granzymes from the plasma membrane to early endosomes, preserving outer membrane integrity. Inhibiting clathrin- or dynamin-dependent endocytosis shifts death by perforin and granzyme B from apoptosis to necrosis. Thus by activating endocytosis to preserve membrane integrity, perforin facilitates granzyme uptake and avoids the proinflammatory necrotic death of a membrane-damaged cell.
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33
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Parodi J, Sepúlveda FJ, Roa J, Opazo C, Inestrosa NC, Aguayo LG. Beta-amyloid causes depletion of synaptic vesicles leading to neurotransmission failure. J Biol Chem 2009; 285:2506-14. [PMID: 19915004 DOI: 10.1074/jbc.m109.030023] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Alzheimer disease is a progressive neurodegenerative brain disorder that leads to major debilitating cognitive deficits. It is believed that the alterations capable of causing brain circuitry dysfunctions have a slow onset and that the full blown disease may take several years to develop. Therefore, it is important to understand the early, asymptomatic, and possible reversible states of the disease with the aim of proposing preventive and disease-modifying therapeutic strategies. It is largely unknown how amyloid beta-peptide (A beta), a principal agent in Alzheimer disease, affects synapses in brain neurons. In this study, we found that similar to other pore-forming neurotoxins, A beta induced a rapid increase in intracellular calcium and miniature currents, indicating an enhancement in vesicular transmitter release. Significantly, blockade of these effects by low extracellular calcium and a peptide known to act as an inhibitor of the A beta-induced pore prevented the delayed failure, indicating that A beta blocks neurotransmission by causing vesicular depletion. This new mechanism for A beta synaptic toxicity should provide an alternative pathway to search for small molecules that can antagonize these effects of A beta.
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Affiliation(s)
- Jorge Parodi
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Edmundo Larenas S/N, P.O. Box 160-C, Concepción, Chile
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34
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Yao CK, Lin YQ, Ly CV, Ohyama T, Haueter CM, Moiseenkova-Bell VY, Wensel TG, Bellen HJ. A synaptic vesicle-associated Ca2+ channel promotes endocytosis and couples exocytosis to endocytosis. Cell 2009; 138:947-60. [PMID: 19737521 PMCID: PMC2749961 DOI: 10.1016/j.cell.2009.06.033] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Revised: 04/27/2009] [Accepted: 06/12/2009] [Indexed: 02/06/2023]
Abstract
Synaptic vesicle (SV) exo- and endocytosis are tightly coupled to sustain neurotransmission in presynaptic terminals, and both are regulated by Ca(2+). Ca(2+) influx triggered by voltage-gated Ca(2+) channels is necessary for SV fusion. However, extracellular Ca(2+) has also been shown to be required for endocytosis. The intracellular Ca(2+) levels (<1 microM) that trigger endocytosis are typically much lower than those (>10 microM) needed to induce exocytosis, and endocytosis is inhibited when the Ca(2+) level exceeds 1 microM. Here, we identify and characterize a transmembrane protein associated with SVs that, upon SV fusion, localizes at periactive zones. Loss of Flower results in impaired intracellular resting Ca(2+) levels and impaired endocytosis. Flower multimerizes and is able to form a channel to control Ca(2+) influx. We propose that Flower functions as a Ca(2+) channel to regulate synaptic endocytosis and hence couples exo- with endocytosis.
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Affiliation(s)
- Chi-Kuang Yao
- Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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35
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Hosoi N, Holt M, Sakaba T. Calcium dependence of exo- and endocytotic coupling at a glutamatergic synapse. Neuron 2009; 63:216-29. [PMID: 19640480 DOI: 10.1016/j.neuron.2009.06.010] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 05/13/2009] [Accepted: 06/08/2009] [Indexed: 01/01/2023]
Abstract
The mechanism coupling exocytosis and endocytosis remains to be elucidated at central synapses. Here, we show that the mechanism linking these two processes is dependent on microdomain-[Ca2+](i) similar to that which triggers exocytosis, as well as the exocytotic protein synaptobrevin/VAMP. Furthermore, block of endocytosis has a limited, retrograde action on exocytosis, delaying recruitment of release-ready vesicles and enhancing short-term depression. This effect sets in so rapidly that it cannot be explained by the nonavailability of recycled vesicles. Rather, we postulate that perturbation of a step linking exocytosis and endocytosis temporarily prevents new vesicles from docking at specialized sites for exocytosis.
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Affiliation(s)
- Nobutake Hosoi
- Independent Junior Research Group of Biophysics of Synaptic Transmission, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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36
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Tsai CC, Lin CL, Wang TL, Chou AC, Chou MY, Lee CH, Peng IW, Liao JH, Chen YT, Pan CY. Dynasore inhibits rapid endocytosis in bovine chromaffin cells. Am J Physiol Cell Physiol 2009; 297:C397-406. [DOI: 10.1152/ajpcell.00562.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vesicle recycling is vital for maintaining membrane homeostasis and neurotransmitter release. Multiple pathways for retrieving vesicles fused to the plasma membrane have been reported in neuroendocrine cells. Dynasore, a dynamin GTPase inhibitor, has been shown to specifically inhibit endocytosis and vesicle recycling in nerve terminals. To characterize its effects in modulating vesicle recycling and repetitive exocytosis, changes in the whole cell membrane capacitance of bovine chromaffin cells were recorded in the perforated-patch configuration. Constitutive endocytosis was blocked by dynasore treatment, as shown by an increase in membrane capacitance. The membrane capacitance was increased during strong depolarizations and declined within 30 s to a value lower than the prestimulus level. The amplitude, but not the time constant, of the rapid exponential decay was significantly decreased by dynasore treatment. Although the maximal increase in capacitance induced by stimulation was significantly increased by dynasore treatment, the intercepts at time 0 of the curve fitted to the decay phase were all ∼110% of the membrane capacitance before stimulation, regardless of the dynasore concentration used. Membrane depolarization caused clathrin aggregation and F-actin continuity disruption at the cell boundary, whereas dynasore treatment induced clathrin aggregation without affecting F-actin continuity. The number of invagination pits on the surface of the plasma membrane determined using atomic force microscopy was increased and the pore was wider in dynasore-treated cells. Our data indicate that dynamin-mediated endocytosis is the main pathway responsible for rapid compensatory endocytosis.
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Khelfaoui M, Pavlowsky A, Powell AD, Valnegri P, Cheong KW, Blandin Y, Passafaro M, Jefferys JGR, Chelly J, Billuart P. Inhibition of RhoA pathway rescues the endocytosis defects in Oligophrenin1 mouse model of mental retardation. Hum Mol Genet 2009; 18:2575-83. [PMID: 19401298 PMCID: PMC2701329 DOI: 10.1093/hmg/ddp189] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The patho-physiological hypothesis of mental retardation caused by the deficiency of the RhoGAP Oligophrenin1 (OPHN1), relies on the well-known functions of Rho GTPases on neuronal morphology, i.e. dendritic spine structure. Here, we describe a new function of this Bin/Amphiphysin/Rvs domain containing protein in the control of clathrin-mediated endocytosis (CME). Through interactions with Src homology 3 domain containing proteins involved in CME, OPHN1 is concentrated to endocytic sites where it down-regulates the RhoA/ROCK signaling pathway and represses the inhibitory function of ROCK on endocytosis. Indeed disruption of Ophn1 in mice reduces the endocytosis of synaptic vesicles and the post-synaptic alpha-amino-3-hydroxy-5-methylisoazol-4-propionate (AMPA) receptor internalization, resulting in almost a complete loss of long-term depression in the hippocampus. Finally, pharmacological inhibition of this pathway by ROCK inhibitors fully rescued not only the CME deficit in OPHN1 null cells but also synaptic plasticity in the hippocampus from Ophn1 null model. Altogether, we uncovered a new patho-physiological mechanism for intellectual disabilities associated to mutations in RhoGTPases linked genes and also opened new directions for therapeutic approaches of congenital mental retardation.
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Affiliation(s)
- Malik Khelfaoui
- Institut Cochin, Université Paris Descartes, CNRS UMR8104, 24 rue du Faubourg Saint Jacques 75014, Paris, France.
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38
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The synaptic vesicle cluster: A source of endocytic proteins during neurotransmitter release. Neuroscience 2009; 158:204-10. [DOI: 10.1016/j.neuroscience.2008.03.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/17/2008] [Accepted: 03/18/2008] [Indexed: 12/11/2022]
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39
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Parodi J, Romero F. Synaptic effects of low molecular weight components from Chilean Black Widow spider venom. Neurotoxicology 2008; 29:1121-6. [PMID: 18824024 DOI: 10.1016/j.neuro.2008.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 08/09/2008] [Accepted: 08/27/2008] [Indexed: 11/26/2022]
Abstract
alpha-Latrotoxin is the principal component of the venom from the euroasiatic Black Widow spider and has been studied for its pharmacological use as a synaptic modulator. Interestingly, smaller molecular weight fractions have been found to be associated with this toxin, but their cellular actions have not been studied in detail. The venom from the Chilean Black Widow spider (Latrodectus mactans) does not produce alpha-latrotoxin, however it does contain several small polypeptides. We have recently demonstrated cellular effects of these peptides at the synaptic level using whole-cell patch clamp techniques. Purified venom from the glands of L. mactans was studied in 12 DIV rat hippocampal neuronal cultures. Venom at a concentration of 10nM was able to decrease neuronal conductance thereby increasing membrane resistance. This effect on the passive properties of the neurons induced a change in action potential kinetics simulating the action of classic potassium channel blockers. These changes produced an increase in spontaneous synaptic activity in rat hippocampal cultures in the presence of the venom in a concentration- and time-dependent manner. These results indicate that venom from Chilean spider L. mactans is capable of increasing cell membrane resistance, prolonging the action potential and generating an increase in synaptic activity demonstrating an interesting pharmacological effect of these low molecular weight fragments.
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Affiliation(s)
- Jorge Parodi
- Laboratorio de Neurociencia-CEBIOR, Departamento de Ciencia Preclinicas, Facultad de Medicina, Universidad de la Frontera, Montevideo 0870, Temuco, Chile.
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40
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Kroeger JH, Geitmann A, Grant M. Model for calcium dependent oscillatory growth in pollen tubes. J Theor Biol 2008; 253:363-74. [PMID: 18471831 DOI: 10.1016/j.jtbi.2008.02.042] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Revised: 02/25/2008] [Accepted: 02/27/2008] [Indexed: 01/28/2023]
Abstract
Experiments have shown that pollen tubes grow in an oscillatory mode, the mechanism of which is poorly understood. We propose a theoretical growth model of pollen tubes exhibiting such oscillatory behaviour. The pollen tube and the surrounding medium are represented by two immiscible fluids separated by an interface. The physical variables are pressure, surface tension, density and viscosity, which depend on relevant biological quantities, namely calcium concentration and thickness of the cell wall. The essential features generally believed to control oscillating growth are included in the model, namely a turgor pressure, a viscous cell wall which yields under pressure, stretch-activated calcium channels which transport calcium ions into the cytoplasm and an exocytosis rate dependent on the cytosolic calcium concentration in the apex of the cell. We find that a calcium dependent vesicle recycling mechanism is necessary to obtain an oscillating growth rate in our model. We study the variation in the frequency of the growth rate by changing the extracellular calcium concentration and the density of ion channels in the membrane. We compare the predictions of our model with experimental data on the frequency of oscillation versus growth speed, calcium concentration and density of calcium channels.
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Affiliation(s)
- Jens H Kroeger
- Ernest Rutherford Physics Building, McGill University, 3600 Rue University, Montréal, Québec H3A2T8, Canada.
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41
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Quan A, McGeachie AB, Keating DJ, van Dam EM, Rusak J, Chau N, Malladi CS, Chen C, McCluskey A, Cousin MA, Robinson PJ. Myristyl trimethyl ammonium bromide and octadecyl trimethyl ammonium bromide are surface-active small molecule dynamin inhibitors that block endocytosis mediated by dynamin I or dynamin II. Mol Pharmacol 2007; 72:1425-39. [PMID: 17702890 DOI: 10.1124/mol.107.034207] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dynamin is a GTPase enzyme involved in membrane constriction and fission during endocytosis. Phospholipid binding via its pleckstrin homology domain maximally stimulates dynamin activity. We developed a series of surface-active small-molecule inhibitors, such as myristyl trimethyl ammonium bromide (MiTMAB) and octadecyltrimethyl ammonium bromide (OcTMAB), and we now show MiTMAB targets the dynamin-phospholipid interaction. MiTMAB inhibited dynamin GTPase activity, with a Ki of 940 +/- 25 nM. It potently inhibited receptor-mediated endocytosis (RME) of transferrin or epidermal growth factor (EGF) in a range of cells without blocking EGF binding, receptor number, or autophosphorylation. RME inhibition was rapidly reversed after washout. The rank order of potency for a variety of MiTMAB analogs on RME matched the rank order for dynamin inhibition, suggesting dynamin recruitment to the membrane is a primary cellular target. MiTMAB also inhibited synaptic vesicle endocytosis in rat brain nerve terminals (synaptosomes) without inducing depolarization or morphological defects. Therefore, the drug rapidly and reversibly blocks multiple forms of endocytosis with no acute cellular damage. The unique mechanism of action of MiTMAB provides an important tool to better understand dynamin-mediated membrane trafficking events in a variety of cells.
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Affiliation(s)
- Annie Quan
- Cell Signaling Unit, Children's Medical Research Institute, University of Sydney, Sydney, NSW 2145, Australia
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Cnops L, Hu TT, Eysel UT, Arckens L. Effect of binocular retinal lesions on CRMP2 and CRMP4 but not Dyn I and Syt I expression in adult cat area 17. Eur J Neurosci 2007; 25:1395-401. [PMID: 17425566 DOI: 10.1111/j.1460-9568.2007.05395.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Removal of retinal input from a restricted region of adult cat visual cortex leads to a substantial reorganization of the retinotopy within the sensory-deprived cortical lesion projection zone (LPZ). Still little is known about the molecular mechanisms underlying this cortical map reorganization. We chose two members of the collapsin response mediator protein (CRMP) family, CRMP2 and CRMP4, because of their involvement in neurite growth, and compared gene and protein expression levels between normal control and reorganizing visual cortex upon induction of central retinal lesions. Parallel analysis of Dynamin I (Dyn I) and Synaptotagmin I (Syt I), two molecules implicated in the exocytosis-endocytosis cycle, was performed because changes in neurotransmitter release have been implicated in cortical plasticity. Western blotting and real-time polymerase chain reaction revealed a clear time-dependent effect of retinal lesioning on CRMP2 and CRMP4 expression, with maximal impact 2 weeks post-lesion. Altered CRMP levels were not a direct consequence of decreased visual activity in the LPZ as complete surgical removal of retinal input to one hemisphere had no effect on CRMP2 or CRMP4 expression. Thus, CRMP expression is correlated to cortical reorganization following partial deafferentation of adult visual cortex. In contrast, Dyn I and Syt I were not influenced and thereby do not promote exocytosis-endocytosis cycle modifications in adult cat cortical plasticity.
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Affiliation(s)
- Lieselotte Cnops
- Laboratory of Neuroplasticity and Neuroproteomics, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
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Bednarek EM, Schaheen L, Gaubatz J, Jorgensen EM, Fares H. The plasma membrane calcium ATPase MCA-3 is required for clathrin-mediated endocytosis in scavenger cells of Caenorhabditis elegans. Traffic 2007; 8:543-53. [PMID: 17343680 DOI: 10.1111/j.1600-0854.2007.00547.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plasma membrane Ca2+ ATPases (PMCAs) maintain proper intracellular Ca2+ levels by extruding Ca2+ from the cytosol. PMCA genes and splice forms are expressed in tissue-specific patterns in vertebrates, suggesting that these isoforms may regulate specific biological processes. However, knockout mutants die as embryos or undergo cell death; thus, it is unclear whether other cell processes utilize PMCAs or whether these pumps are largely committed to the control of toxic levels of calcium. Here, we analyze the role of the PMCA gene, mca-3, in Caenorhabditis elegans. We report that partial loss-of-function mutations disrupt clathrin-mediated endocytosis in a class of scavenger cells called coelomocytes. Moreover, components of early endocytic machinery are mislocalized in mca-3 mutants, including phosphatidylinositol-4,5-bisphosphate, clathrin and the Eps15 homology (EH) domain protein RME-1. This defect in endocytosis in the coelomocytes can be reversed by lowering calcium. Together, these data support a function for PMCAs in the regulation of endocytosis in the C. elegans coelomocytes. In addition, they suggest that endocytosis can be blocked by high calcium levels.
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Affiliation(s)
- Ewa M Bednarek
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112, USA
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Cnops L, Hu TT, Vanden Broeck J, Burnat K, Van Den Bergh G, Arckens L. Age- and experience-dependent expression of Dynamin I and Synaptotagmin I in cat visual system. J Comp Neurol 2007; 504:254-64. [PMID: 17640048 DOI: 10.1002/cne.21415] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Dynamin I (Dyn I) and Synaptotagmin I (Syt I) are essential for endocytosis-exocytosis processes, thus for neurotransmission. Despite their related function at presynaptic terminals, Dyn I and Syt I displayed opposite expression patterns during visual cortex maturation in the cat. Dyn I was more abundantly expressed in adults, while Syt I exhibited higher levels in kittens of postnatal day 30 (P30). In area 17 this developmental difference was most obvious in layers II/III. Layer VI displayed a strong hybridization signal for both molecules, independent of age. In addition, Syt I levels were higher in posterior compared to anterior area 17 in adult subjects. Moreover, in higher-order visual areas Syt I was unevenly distributed over the cortical layers, thereby setting clear areal boundaries in mature cortex. In contrast, Dyn I was rather homogeneously distributed over extrastriate areas at both ages. Both molecules thus demonstrated a widespread but different distribution and an opposite temporal expression pattern during visual system development. Notably, monocular deprivation during the critical period of ocular dominance plasticity significantly decreased Syt I expression levels in area 17 ipsilateral to the deprived eye, while no effect was observed on Dyn I expression. We therefore conclude that visual experience induces changes in Syt I expression that may reflect changes in constitutive exocytosis involved in postnatal structural refinements of the visual cortex. On the other hand, the spatial and temporal expression patterns of Dyn I correlate with the establishment and maintenance of the mature neuronal structure rather than neurite remodeling.
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Affiliation(s)
- Lieselotte Cnops
- Laboratory of Neuroplasticity and Neuroproteomics, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
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45
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Anggono V, Smillie KJ, Graham ME, Valova VA, Cousin MA, Robinson PJ. Syndapin I is the phosphorylation-regulated dynamin I partner in synaptic vesicle endocytosis. Nat Neurosci 2006; 9:752-60. [PMID: 16648848 PMCID: PMC2082060 DOI: 10.1038/nn1695] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 04/10/2006] [Indexed: 01/12/2023]
Abstract
Dynamin I is dephosphorylated at Ser-774 and Ser-778 during synaptic vesicle endocytosis (SVE) in nerve terminals. Phosphorylation was proposed to regulate the assembly of an endocytic protein complex with amphiphysin or endophilin. Instead, we found it recruits syndapin I for SVE and does not control amphiphysin or endophilin binding in rat synaptosomes. After depolarization, syndapin showed a calcineurin-mediated interaction with dynamin. A peptide mimicking the phosphorylation sites disrupted the dynamin-syndapin complex, not the dynamin-endophilin complex, arrested SVE and produced glutamate release fatigue after repetitive stimulation. Pseudophosphorylation of Ser-774 or Ser-778 inhibited syndapin binding without affecting amphiphysin recruitment. Site mutagenesis to alanine arrested SVE in cultured neurons. The effects of the sites were additive for syndapin I binding and SVE. Thus syndapin I is a central component of the endocytic protein complex for SVE via stimulus-dependent recruitment to dynamin I and has a key role in synaptic transmission.
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Affiliation(s)
- Victor Anggono
- Cell Signalling Unit, Children's Medical Research Institute, Locked Bag 23, Wentworthville, NSW 2145, Australia
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46
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Kip SN, Gray NW, Burette A, Canbay A, Weinberg RJ, Strehler EE. Changes in the expression of plasma membrane calcium extrusion systems during the maturation of hippocampal neurons. Hippocampus 2006; 16:20-34. [PMID: 16200642 PMCID: PMC3873839 DOI: 10.1002/hipo.20129] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Spatial and temporal control of intracellular calcium signaling is essential for neuronal development and function. The termination of local Ca2+ signaling and the maintenance of basal Ca2+ levels require specific extrusion systems in the plasma membrane. In rat hippocampal neurons (HNs) developing in vitro, transcripts for all isoforms of the plasma membrane Ca2+ pump and the Na/Ca2+ exchanger, and the major nonphotoreceptor Na+/Ca2+,K+ exchangers (NCKX) were strongly upregulated during the second week in culture. Upregulation of plasma membrane calcium ATPases (PMCAs)1, 3, and 4 mRNA coincided with a splice shift from the ubiquitous b-type to the neuron-specific a-type with altered calmodulin regulation. Expression of all PMCA isoforms increased over 5-fold during the first 2 weeks. PMCA immunoreactivity was initially concentrated in the soma and growth cones of developing HNs. As the cells matured, PMCAs concentrated in the dendritic membrane and often colocalized with actin-rich dendritic spines in mature neurons. In the developing rat hippocampal CA1 region, immunohistochemistry confirmed the upregulation of all PMCAs and showed that by the end of the second postnatal week, PMCAs1, 2, and 3 were concentrated in the neuropil, with less intense staining of cell bodies in the pyramidal layer. PMCA4 staining was restricted to a few cells showing intense labeling of the cell periphery and neurites. These results establish that all major Ca2+ extrusion systems are strongly upregulated in HNs during the first 2 weeks of postnatal development. The overall increase in Ca2+ extrusion systems is accompanied by changes in the expression and cellular localization of different isoforms of the Ca2+ pumps and exchangers. The accumulation of PMCAs in dendrites and dendritic spines coincides with the functional maturation in these neurons, suggesting the importance of the proper spatial organization of Ca2+ extrusion systems for synaptic function and development.
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Affiliation(s)
- Sertac N. Kip
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Noah W. Gray
- Molecular Neuroscience Graduate Program, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Alain Burette
- Department of Cell and Developmental Biology and Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Ali Canbay
- Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Richard J. Weinberg
- Department of Cell and Developmental Biology and Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Emanuel E. Strehler
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
- Molecular Neuroscience Graduate Program, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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MacDonald PE, Eliasson L, Rorsman P. Calcium increases endocytotic vesicle size and accelerates membrane fission in insulin-secreting INS-1 cells. J Cell Sci 2005; 118:5911-20. [PMID: 16317049 DOI: 10.1242/jcs.02685] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In many cells, endocytotic membrane retrieval is accelerated by Ca2+. The effect of Ca2+ on single endocytotic vesicles and fission pore kinetics was examined by measuring capacitance and conductance changes in small membrane patches of insulin-secreting INS-1 cells. In intact cells, elevation of Ca2+ by glucose stimulation induced a 1.8-fold increase in membrane internalisation. This surprisingly resulted from an increased unitary capacitance of endocytotic vesicles whereas the frequency of endocytosis was unaltered. This effect of glucose was prevented by inhibition of L- or R-type Ca2+ channels. Extracellular (pipette) Ca2+ was found to regulate endocytotic vesicle capacitance in a bimodal manner. Vesicle capacitance was increased at intermediate Ca2+ (2.6 mM), but not at high Ca2+ (10 mM). Similar results were obtained upon direct application of 100 nM and 0.5 mM Ca2+ to the intracellular surface of inside-out excised membrane patches, and in these experiments the increase in vesicle capacitance was prevented by the calcineurin inhibitor deltamethrin. Endocytotic fission pore kinetics were accelerated by Ca2+ in both the intact cells and isolated membrane patches; however, the effect in this case was neither bimodal nor deltamethrin sensitive. Membrane retrieval can therefore be upregulated by a Ca2+-dependent increase in endocytotic vesicle size and acceleration of membrane fission in insulin-secreting INS-1 cells.
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Affiliation(s)
- Patrick E MacDonald
- Division of Diabetes, Metabolism and Endocrinology, Lund University, 221 84 Lund, Sweden.
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48
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Girard M, Allaire PD, McPherson PS, Blondeau F. Non-stoichiometric relationship between clathrin heavy and light chains revealed by quantitative comparative proteomics of clathrin-coated vesicles from brain and liver. Mol Cell Proteomics 2005; 4:1145-54. [PMID: 15933375 DOI: 10.1074/mcp.m500043-mcp200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We used tandem mass spectrometry with peptide counts to identify and to determine the relative levels of expression of abundant protein components of highly enriched clathrin-coated vesicles (CCVs) from rat liver. The stoichiometry of stable protein complexes including clathrin heavy chain and clathrin light chain dimers and adaptor protein (AP) heterotetramers was assessed. We detected a deficit of clathrin light chain compared with clathrin heavy chain in non-brain tissues, suggesting a level of regulation of clathrin cage formation specific to brain. The high ratio of AP-1 to AP-2 in liver CCVs is reversed compared with brain where there is more AP-2 than AP-1. Despite this, general endocytic cargo proteins were readily detected in liver but not in brain CCVs, consistent with the previous demonstration that a major function for brain CCVs is recycling synaptic vesicles. Finally we identified 21 CCV-associated proteins in liver not yet characterized in mammals. Our results further validate the peptide accounting approach, reveal new information on the properties of CCVs, and allow for the use of quantitative proteomics to compare abundant components of organelles under different experimental and pathological conditions.
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Affiliation(s)
- Martine Girard
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Québec H3A 2B4, Canada
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49
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Teng H, Wilkinson RS. Clathrin-mediated endocytosis in snake motor terminals is directly facilitated by intracellular Ca2+. J Physiol 2005; 565:743-50. [PMID: 15860527 PMCID: PMC1464571 DOI: 10.1113/jphysiol.2005.087296] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
At the snake neuromuscular junction, low temperature (LT, 5-7 degrees C) blocks clathrin-mediated endocytosis (CME) while exocytosis is largely unaffected. Thus compensatory endocytosis that normally follows transmitter release is inhibited, or 'delayed' until the preparation is warmed to room temperature (RT). This delay was exploited to observe how changes in bulk [Ca(2+)](i) directly affect CME. Motor terminals were loaded with fura-2 to monitor [Ca(2+)](i). With brief stimulation at LT, [Ca(2+)](i) transiently increased but returned to baseline ( approximately 63 nm) in < 8 min. After 15 min at LT, [Ca(2+)](i) was altered by incubating preparations in the Ca(2+) ionophore ionomyocin. Preparations were then warmed to RT to initiate delayed endocytosis, which was quantified as uptake of the fluorescent optical probe sulforhodamine 101. Endocytosis was more rapid when [Ca(2+)](i) increased; the rate at 300 nm Ca(2+) was approximately double that under basal conditions. Thus the rate of CME - isolated from stimulation, transmitter release, and other forms of endocytosis - is directly influenced by intraterminal Ca(2+).
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Affiliation(s)
- Haibing Teng
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Ave., Box 8228, St. Louis, MO 63110, USA
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50
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Abstract
Certain excitatory pathways in the rat hippocampus can release aspartate along with glutamate. This study utilized rat hippocampal synaptosomes to characterize the mechanism of aspartate release and to compare it with glutamate release. Releases of aspartate and glutamate from the same tissue samples were quantitated simultaneously. Both amino acids were released by 25 mM K(+), 300 microM 4-aminopyridine (4-AP) and 0.5 and 1 microM ionomycin in a predominantly Ca(2+)-dependent manner. For a roughly equivalent quantity of glutamate released, aspartate release was significantly greater during exposure to elevated [K(+)] than to 4-AP and during exposure to 0.5 than to 1 microM ionomycin. Aspartate release was inefficiently coupled to P/Q-type voltage-dependent Ca(2+) channels and was reduced by KB-R7943, an inhibitor of reversed Na(+)/Ca(2+) exchange. In contrast, glutamate release depended primarily on Ca(2+) influx through P/Q-type channels and was not significantly affected by KB-R7943. Pretreatment of the synaptosomes with tetanus toxin and botulinum neurotoxins C and F reduced glutamate release, but not aspartate release. Aspartate release was also resistant to bafilomycin A(1), an inhibitor of vacuolar H(+)-ATPase, whereas glutamate release was markedly reduced. (+/-) -Threo-3-methylglutamate, a non-transportable competitive inhibitor of excitatory amino acid transport, did not reduce aspartate release. Niflumic acid, a blocker of Ca(2+)-dependent anion channels, did not alter the release of either amino acid. Exogenous aspartate and aspartate recently synthesized from glutamate accessed the releasable pool of aspartate as readily as exogenous glutamate and glutamate recently synthesized from aspartate accessed the releasable glutamate pool. These results are compatible with release of aspartate from either a vesicular pool by a "non-classical" form of exocytosis or directly from the cytoplasm by an as-yet-undescribed Ca(2+)-dependent mechanism. In either case, they suggest aspartate is released mainly outside the presynaptic active zones and may therefore serve as the predominant agonist for extrasynaptic N-methyl-D-aspartate receptors.
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Affiliation(s)
- S E Bradford
- Department of Pharmacology and Cancer Biology, Box 3813, 100B Research Park 2, Research Drive, Duke University Medical Center, Durham, NC 27710, USA
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