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Polishchuk A, Cilleros-Mañé V, Just-Borràs L, Balanyà-Segura M, Vandellòs Pont G, Silvera Simón C, Tomàs M, Garcia N, Tomàs J, Lanuza MA. Synaptic retrograde regulation of the PKA-induced SNAP-25 and Synapsin-1 phosphorylation. Cell Mol Biol Lett 2023; 28:17. [PMID: 36869288 PMCID: PMC9985302 DOI: 10.1186/s11658-023-00431-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 02/09/2023] [Indexed: 03/05/2023] Open
Abstract
BACKGROUND Bidirectional communication between presynaptic and postsynaptic components contribute to the homeostasis of the synapse. In the neuromuscular synapse, the arrival of the nerve impulse at the presynaptic terminal triggers the molecular mechanisms associated with ACh release, which can be retrogradely regulated by the resulting muscle contraction. This retrograde regulation, however, has been poorly studied. At the neuromuscular junction (NMJ), protein kinase A (PKA) enhances neurotransmitter release, and the phosphorylation of the molecules of the release machinery including synaptosomal associated protein of 25 kDa (SNAP-25) and Synapsin-1 could be involved. METHODS Accordingly, to study the effect of synaptic retrograde regulation of the PKA subunits and its activity, we stimulated the rat phrenic nerve (1 Hz, 30 min) resulting or not in contraction (abolished by µ-conotoxin GIIIB). Changes in protein levels and phosphorylation were detected by western blotting and cytosol/membrane translocation by subcellular fractionation. Synapsin-1 was localized in the levator auris longus (LAL) muscle by immunohistochemistry. RESULTS Here we show that synaptic PKA Cβ subunit regulated by RIIβ or RIIα subunits controls activity-dependent phosphorylation of SNAP-25 and Synapsin-1, respectively. Muscle contraction retrogradely downregulates presynaptic activity-induced pSynapsin-1 S9 while that enhances pSNAP-25 T138. Both actions could coordinately contribute to decreasing the neurotransmitter release at the NMJ. CONCLUSION This provides a molecular mechanism of the bidirectional communication between nerve terminals and muscle cells to balance the accurate process of ACh release, which could be important to characterize molecules as a therapy for neuromuscular diseases in which neuromuscular crosstalk is impaired.
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Affiliation(s)
- Aleksandra Polishchuk
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Víctor Cilleros-Mañé
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Laia Just-Borràs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Marta Balanyà-Segura
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Genís Vandellòs Pont
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Carolina Silvera Simón
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Marta Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Neus Garcia
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Josep Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain.
| | - Maria A Lanuza
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain.
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Just-Borràs L, Cilleros-Mañé V, Polishchuk A, Balanyà-Segura M, Tomàs M, Garcia N, Tomàs J, Lanuza MA. TrkB signaling is correlated with muscular fatigue resistance and less vulnerability to neurodegeneration. Front Mol Neurosci 2022; 15:1069940. [PMID: 36618825 PMCID: PMC9813967 DOI: 10.3389/fnmol.2022.1069940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 11/29/2022] [Indexed: 12/24/2022] Open
Abstract
At the neuromuscular junction (NMJ), motor neurons and myocytes maintain a bidirectional communication that guarantees adequate functionality. Thus, motor neurons' firing pattern, which is influenced by retrograde muscle-derived neurotrophic factors, modulates myocyte contractibility. Myocytes can be fast-twitch fibers and become easily fatigued or slow-twitch fibers and resistant to fatigue. Extraocular muscles (EOM) show mixed properties that guarantee fast contraction speed and resistance to fatigue and the degeneration caused by Amyotrophic lateral sclerosis (ALS) disease. The TrkB signaling is an activity-dependent pathway implicated in the NMJ well-functioning. Therefore, it could mediate the differences between fast and slow myocytes' resistance to fatigue. The present study elucidates a specific protein expression profile concerning the TrkB signaling that correlates with higher resistance to fatigue and better neuroprotective capacity through time. The results unveil that Extra-ocular muscles (EOM) express lower levels of NT-4 that extend TrkB signaling, differential PKC expression, and a higher abundance of phosphorylated synaptic proteins that correlate with continuous neurotransmission requirements. Furthermore, common molecular features between EOM and slow soleus muscles including higher neurotrophic consumption and classic and novel PKC isoforms balance correlate with better preservation of these two muscles in ALS. Altogether, higher resistance of Soleus and EOM to fatigue and ALS seems to be associated with specific protein levels concerning the TrkB neurotrophic signaling.
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Cilleros-Mañé V, Just-Borràs L, Polishchuk A, Durán M, Tomàs M, Garcia N, Tomàs JM, Lanuza MA. M 1 and M 2 mAChRs activate PDK1 and regulate PKC βI and ε and the exocytotic apparatus at the NMJ. FASEB J 2021; 35:e21724. [PMID: 34133802 DOI: 10.1096/fj.202002213r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 05/07/2021] [Accepted: 05/24/2021] [Indexed: 01/14/2023]
Abstract
Neuromuscular junctions (NMJ) regulate cholinergic exocytosis through the M1 and M2 muscarinic acetylcholine autoreceptors (mAChR), involving the crosstalk between receptors and downstream pathways. Protein kinase C (PKC) regulates neurotransmission but how it associates with the mAChRs remains unknown. Here, we investigate whether mAChRs recruit the classical PKCβI and the novel PKCε isoforms and modulate their priming by PDK1, translocation and activity on neurosecretion targets. We show that each M1 and M2 mAChR activates the master kinase PDK1 and promotes a particular priming of the presynaptic PKCβI and ε isoforms. M1 recruits both primed-PKCs to the membrane and promotes Munc18-1, SNAP-25, and MARCKS phosphorylation. In contrast, M2 downregulates PKCε through a PKA-dependent pathway, which inhibits Munc18-1 synthesis and PKC phosphorylation. In summary, our results discover a co-dependent balance between muscarinic autoreceptors which orchestrates the presynaptic PKC and their action on ACh release SNARE-SM mechanism. Altogether, this molecular signaling explains previous functional studies at the NMJ and guide toward potential therapeutic targets.
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Affiliation(s)
- V Cilleros-Mañé
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - L Just-Borràs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - A Polishchuk
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - M Durán
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - M Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - N Garcia
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - J M Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - M A Lanuza
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Facultat de Medicina i Ciències de la Salut, Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
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Fagiani F, Lanni C, Racchi M, Pascale A, Govoni S. Amyloid-β and Synaptic Vesicle Dynamics: A Cacophonic Orchestra. J Alzheimers Dis 2020; 72:1-14. [PMID: 31561377 DOI: 10.3233/jad-190771] [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: 12/14/2022]
Abstract
It is now more than two decades since amyloid-β (Aβ), the proteolytic product of the amyloid-β protein precursor (AβPP), was first demonstrated to be a normal and soluble product of neuronal metabolism. To date, despite a growing body of evidence suggests its regulatory role on synaptic function, the exact cellular and molecular pathways involved in Aβ-driven synaptic effects remain elusive. This review provides an overview of the mounting evidence showing Aβ-mediated effects on presynaptic functions and neurotransmitter release from axon terminals, focusing on its interaction with synaptic vesicle cycle. Indeed, Aβ peptides have been found to interact with key presynaptic scaffold proteins and kinases affecting the consequential steps of the synaptic vesicle dynamics (e.g., synaptic vesicles exocytosis, endocytosis, and trafficking). Defects in the fine-tuning of synaptic vesicle cycle by Aβ and deregulation of key molecules and kinases, which orchestrate synaptic vesicle availability, may alter synaptic homeostasis, possibly contributing to synaptic loss and cognitive decline. Elucidating the presynaptic mechanisms by which Aβ regulate synaptic transmission is fundamental for a deeper comprehension of the biology of presynaptic terminals as well as of Aβ-driven early synaptic defects occurring in prodromal stage of AD. Moreover, a better understating of Aβ involvement in cellular signal pathways may allow to set up more effective therapeutic interventions by detecting relevant molecular mechanisms, whose imbalance might ultimately lead to synaptic impairment in AD.
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Affiliation(s)
- Francesca Fagiani
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Italy.,Scuola Universitaria Superiore IUSS, Pavia, Italy
| | - Cristina Lanni
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Italy
| | - Marco Racchi
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Italy
| | - Alessia Pascale
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Italy
| | - Stefano Govoni
- Department of Drug Sciences, Pharmacology Section, University of Pavia, Italy
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Cilleros-Mañé V, Just-Borràs L, Tomàs M, Garcia N, Tomàs JM, Lanuza MA. The M 2 muscarinic receptor, in association to M 1 , regulates the neuromuscular PKA molecular dynamics. FASEB J 2020; 34:4934-4955. [PMID: 32052889 DOI: 10.1096/fj.201902113r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/23/2019] [Accepted: 01/20/2020] [Indexed: 01/13/2023]
Abstract
Muscarinic acetylcholine receptor 1 subtype (M1 ) and muscarinic acetylcholine receptor 2 subtype (M2 ) presynaptic muscarinic receptor subtypes increase and decrease, respectively, neurotransmitter release at neuromuscular junctions. M2 involves protein kinase A (PKA), although the muscarinic regulation to form and inactivate the PKA holoenzyme is unknown. Here, we show that M2 signaling inhibits PKA by downregulating Cβ subunit, upregulating RIIα/β and liberating RIβ and RIIα to the cytosol. This promotes PKA holoenzyme formation and reduces the phosphorylation of the transmitter release target synaptosome-associated protein 25 and the gene regulator cAMP response element binding. Instead, M1 signaling, which is downregulated by M2 , opposes to M2 by recruiting R subunits to the membrane. The M1 and M2 reciprocal actions are performed through the anchoring protein A kinase anchor protein 150 as a common node. Interestingly, M2 modulation on protein expression needs M1 signaling. Altogether, these results describe the dynamics of PKA subunits upon M2 muscarinic signaling in basal and under presynaptic nerve activity, uncover a specific involvement of the M1 receptor and reveal the M1 /M2 balance to activate PKA to regulate neurotransmission. This provides a molecular mechanism to the PKA holoenzyme formation and inactivation which could be general to other synapses and cellular models.
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Affiliation(s)
- Víctor Cilleros-Mañé
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - Laia Just-Borràs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - Marta Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - Neus Garcia
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - Josep Maria Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
| | - Maria Angel Lanuza
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Universitat Rovira i Virgili, Reus, Spain
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6
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Ruiter M, Houy S, Engholm-Keller K, Graham ME, Sørensen JB. SNAP-25 phosphorylation at Ser187 is not involved in Ca 2+ or phorbolester-dependent potentiation of synaptic release. Mol Cell Neurosci 2019; 102:103452. [PMID: 31794878 DOI: 10.1016/j.mcn.2019.103452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/13/2019] [Accepted: 11/29/2019] [Indexed: 11/25/2022] Open
Abstract
SNAP-25, one of the three SNARE-proteins responsible for synaptic release, can be phosphorylated by Protein Kinase C on Ser-187, close to the fusion pore. In neuroendocrine cells, this phosphorylation event potentiates vesicle recruitment into releasable pools, whereas the consequences of phosphorylation for synaptic release remain unclear. We mutated Ser-187 and expressed two mutants (S187C and S187E) in the context of the SNAP-25B-isoform in SNAP-25 knockout glutamatergic autaptic neurons. Whole-cell patch clamp recordings were performed to assess the effect of Ser-187 phosphorylation on synaptic transmission. Blocking phosphorylation by expressing the S187C mutant did not affect synapse density, basic evoked or spontaneous neurotransmission, the readily-releasable pool size or its Ca2+-independent or Ca2+-dependent replenishment. Furthermore, it did not affect the response to phorbol esters, which activate PKC. Expressing S187C in the context of the SNAP-25A isoform also did not affect synaptic transmission. Strikingly, the - potentially phosphomimetic - mutant S187E reduced spontaneous release and release probability, with the largest effect seen in the SNAP-25B isoform, showing that a negative charge in this position is detrimental for neurotransmission, in agreement with electrostatic fusion triggering. During the course of our experiments, we found that higher SNAP-25B expression levels led to decreased paired pulse potentiation, probably due to higher release probabilities. Under these conditions, the potentiation of evoked EPSCs by phorbol esters was followed by a persistent down-regulation, probably due to a ceiling effect. In conclusion, our results indicate that phosphorylation of Ser-187 in SNAP-25 is not involved in modulation of synaptic release by Ca2+ or phorbol esters.
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Affiliation(s)
- Marvin Ruiter
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark
| | - Sébastien Houy
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark
| | - Kasper Engholm-Keller
- Synapse Proteomics Group, Children's Medical Research Institute, The University of Sydney, 214 Hawkesbury Road, Westmead NSW 2145, New South Wales, Australia; Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Mark E Graham
- Synapse Proteomics Group, Children's Medical Research Institute, The University of Sydney, 214 Hawkesbury Road, Westmead NSW 2145, New South Wales, Australia
| | - Jakob B Sørensen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark.
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The SNAP-25 Protein Family. Neuroscience 2019; 420:50-71. [DOI: 10.1016/j.neuroscience.2018.09.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 08/31/2018] [Accepted: 09/14/2018] [Indexed: 01/04/2023]
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8
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Lanni C, Fagiani F, Racchi M, Preda S, Pascale A, Grilli M, Allegri N, Govoni S. Beta-amyloid short- and long-term synaptic entanglement. Pharmacol Res 2019; 139:243-260. [DOI: 10.1016/j.phrs.2018.11.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/06/2018] [Accepted: 11/09/2018] [Indexed: 12/17/2022]
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Wang X, Liu Y, Jia M, Sun X, Wang N, Li Y, Cui C. Phosphorylated SNAP25 in the CA1 regulates morphine-associated contextual memory retrieval via increasing GluN2B-NMDAR surface localization. Addict Biol 2018; 23:1067-1078. [PMID: 28884870 DOI: 10.1111/adb.12558] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Revised: 07/13/2017] [Accepted: 08/18/2017] [Indexed: 01/10/2023]
Abstract
Although our previous studies have demonstrated both protein kinase C (PKC) and GluN2B-containing N-methyl-d-aspartate receptor (GluN2B-NMDAR) play crucial roles in morphine-associated learning and memory, the relationship between them remains unexplored. In this study, we validated the enhanced PKC and membrane GluN2B protein expression in the hippocampal CA1 after morphine conditioned place preference (CPP) expression in rats. Interestingly, we also found that phosphorylation of SNAP25 at Ser187 (pSer187-SNAP25), a PKC-activated target, was significantly increased following morphine CPP expression. Blocking the pSer187-SNAP25 by intra-CA1 injection of an interfering peptide impaired morphine CPP expression and accompanied by the reduced ratio of GluN2B membrane/total in the CA1. In addition, intra-CA1 blockade of pSer187-SNAP25 did not affect natural learning and memory process as evidenced by intact sucrose-induced CPP expression and normal locomotor activity in rats. Therefore, our results reveal that enhanced pSer187-SNAP25 by PKC recruits GluN2B-NMDAR to the membrane surface in the hippocampal CA1 and mediates context-induced addiction memory retrieval. Our findings in this study fill in the missing link and provide better understanding of the molecular mechanisms involved in morphine-associated contextual memory retrieval.
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Affiliation(s)
- Xinjuan Wang
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Yan Liu
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Meng Jia
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Xiaowei Sun
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Na Wang
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Yijing Li
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
| | - Cailian Cui
- Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience of the Ministry of Education and National Health and Family Planning Commission, Neuroscience Research Institute; Peking University; China
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Simó A, Just-Borràs L, Cilleros-Mañé V, Hurtado E, Nadal L, Tomàs M, Garcia N, Lanuza MA, Tomàs J. BDNF-TrkB Signaling Coupled to nPKCε and cPKCβI Modulate the Phosphorylation of the Exocytotic Protein Munc18-1 During Synaptic Activity at the Neuromuscular Junction. Front Mol Neurosci 2018; 11:207. [PMID: 29946239 PMCID: PMC6007318 DOI: 10.3389/fnmol.2018.00207] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/25/2018] [Indexed: 11/13/2022] Open
Abstract
Munc18-1, a neuron-specific member of the Sec1/Munc18 family, is involved in neurotransmitter release by binding tightly to syntaxin. Munc18-1 is phosphorylated by PKC on Ser-306 and Ser-313 in vitro which reduces the amount of Munc18-1 able to bind syntaxin. We have previously identified that PKC is involved in neurotransmitter release when continuous electrical stimulation imposes a moderate activity on the NMJ and that muscle contraction through TrkB has an important impact on presynaptic PKC isoforms levels, specifically cPKCβI and nPKCε. Therefore, the present study was designed to understand how Munc18-1 phosphorylation is affected by (1) synaptic activity at the neuromuscular junction, (2) nPKCε and cPKCβI isoforms activity, (3) muscle contraction per se, and (4) the BDNF/TrkB signaling in a neuromuscular activity-dependent manner. We performed immunohistochemistry and confocal techniques to evidence the presynaptic location of Munc18-1 in the rat diaphragm muscle. To study synaptic activity, we stimulated the phrenic nerve (1 Hz, 30 min) with or without contraction (abolished by μ-conotoxin GIIIB). Specific inhibitory reagents were used to block nPKCε and cPKCβI activity and to modulate the tropomyosin receptor kinase B (TrkB). Main results obtained from Western blot experiments showed that phosphorylation of Munc18-1 at Ser-313 increases in response to a signaling mechanism initiated by synaptic activity and directly mediated by nPKCε. Otherwise, cPKCβI and TrkB activities work together to prevent this synaptic activity-induced Munc18-1 phosphorylation by a negative regulation of cPKCβI over nPKCε. Therefore, a balance between the activities of these PKC isoforms could be a relevant cue in the regulation of the exocytotic apparatus. The results also demonstrate that muscle contraction prevents the synaptic activity-induced Munc18-1 phosphorylation through a mechanism that opposes the TrkB/cPKCβI/nPKCε signaling.
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Affiliation(s)
- Anna Simó
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Laia Just-Borràs
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Víctor Cilleros-Mañé
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Erica Hurtado
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Laura Nadal
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Marta Tomàs
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Neus Garcia
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Maria A Lanuza
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
| | - Josep Tomàs
- Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
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SNARE phosphorylation: a control mechanism for insulin-stimulated glucose transport and other regulated exocytic events. Biochem Soc Trans 2017; 45:1271-1277. [PMID: 29101310 DOI: 10.1042/bst20170202] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/03/2017] [Accepted: 10/04/2017] [Indexed: 11/17/2022]
Abstract
Trafficking within eukaryotic cells is a complex and highly regulated process; events such as recycling of plasma membrane receptors, formation of multivesicular bodies, regulated release of hormones and delivery of proteins to membranes all require directionality and specificity. The underpinning processes, including cargo selection, membrane fusion, trafficking flow and timing, are controlled by a variety of molecular mechanisms and engage multiple families of lipids and proteins. Here, we will focus on control of trafficking processes via the action of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) family of proteins, in particular their regulation by phosphorylation. We will describe how these proteins are controlled in a range of regulated trafficking events, with particular emphasis on the insulin-stimulated delivery of glucose transporters to the surface of adipose and muscle cells. Here, we focus on a few examples of SNARE phosphorylation which exemplify distinct ways in which SNARE machinery phosphorylation may regulate membrane fusion.
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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Horváth D, Tamás I, Sipos A, Darula Z, Bécsi B, Nagy D, Iván J, Erdődi F, Lontay B. Myosin phosphatase and RhoA-activated kinase modulate neurotransmitter release by regulating SNAP-25 of SNARE complex. PLoS One 2017; 12:e0177046. [PMID: 28486561 PMCID: PMC5423623 DOI: 10.1371/journal.pone.0177046] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 04/23/2017] [Indexed: 11/19/2022] Open
Abstract
Reversible phosphorylation of neuronal proteins plays an important role in the regulation of neurotransmitter release. Myosin phosphatase holoenzyme (MP) consists of a protein phosphatase-1 (PP1) catalytic subunit (PP1c) and a regulatory subunit, termed myosin phosphatase targeting subunit (MYPT1). The primary function of MP is to regulate the phosphorylation level of contractile proteins; however, recent studies have shown that MP is localized to neurons, and is also involved in the mediation of neuronal processes. Our goal was to investigate the effect of RhoA-activated kinase (ROK) and MP on the phosphorylation of one potential neuronal substrate, the synaptosomal-associated protein of 25 kDa (SNAP-25). SNAP-25 is a member of the SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) complex, along with synaptobrevin and syntaxin, and the primary role of SNAP25 is to mediate vesicle fusion. We showed that MYPT1 interacts with SNAP-25, as revealed by immunoprecipitation and surface plasmon resonance based binding studies. Mass spectrometry analysis and in vitro phosphorylation/dephosphorylation assays demonstrated that ROK phosphorylates, while MP dephosphorylates, SNAP-25 at Thr138. Silencing MYPT1 in B50 neuroblastoma cells increased phosphorylation of SNAP-25 at Thr138. Inhibition of PP1 with tautomycetin increased, whereas inhibition of ROK by H1152, decreased the phosphorylation of SNAP-25 at Thr138 in B50 cells, in cortical synaptosomes, and in brain slices. In response to the transduction of the MP inhibitor, kinase-enhanced PP1 inhibitor (KEPI), into synaptosomes, an increase in phosphorylation of SNAP-25 and a decrease in the extent of neurotransmitter release were detected. The interaction between SNAP-25 and syntaxin increased with decreasing phosphorylation of SNAP-25 at Thr138, upon inhibition of ROK. Our data suggest that ROK/MP play a crucial role in vesicle trafficking, fusion, and neurotransmitter release by oppositely regulating the phosphorylation of SNAP-25 at Thr138.
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Affiliation(s)
- Dániel Horváth
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - István Tamás
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Adrienn Sipos
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsuzsanna Darula
- Hungarian Academy of Sciences, Proteomics Research Group, Biological Research Centre, Szeged, Hungary
| | - Bálint Bécsi
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dénes Nagy
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Judit Iván
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Ferenc Erdődi
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beáta Lontay
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- * E-mail:
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14
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Weng W, Chen Y, Wang M, Zhuang Y, Behnisch T. Potentiation of Schaffer-Collateral CA1 Synaptic Transmission by eEF2K and p38 MAPK Mediated Mechanisms. Front Cell Neurosci 2016; 10:247. [PMID: 27826228 PMCID: PMC5078695 DOI: 10.3389/fncel.2016.00247] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 10/10/2016] [Indexed: 12/20/2022] Open
Abstract
The elongation factor 2 kinase (eEF2K), likewise known as CaMKIII, has been demonstrated to be involved in antidepressant responses of NMDA receptor antagonists. Even so, it remains open whether direct inhibition of eEF2K without altering up-stream or other signaling pathways affects hippocampal synaptic transmission and neuronal network synchrony. Inhibition of eEF2K by the selective and potent eEF2K inhibitor A-484954 induced a fast pre-synaptically mediated enhancement of synaptic transmission and synchronization of neural network activity. The eEF2K-inhibition mediated potentiation of synaptic transmission of hippocampal CA1 neurons is most notably independent of protein synthesis and does not rely on protein kinase C, protein kinase A or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase 1/2. Moreover, the strengthening of synaptic transmission in the response to the inhibition of eEF2K was strongly attenuated by the inhibition of p38 MAPK. In addition, we show the involvement of barium-sensitive and more specific the TWIK-related potassium-1 (TREK-1) channels in the eEF2K-inhibition mediated potentiation of synaptic transmission. These findings reveal a novel pathway of eEF2K mediated regulation of hippocampal synaptic transmission. Further research is required to study whether such compounds could be beneficial for the development of mood disorder treatments with a fast-acting antidepressant response.
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Affiliation(s)
- Weiguang Weng
- The Institutes of Brain Science, The State Key Laboratory of Medical Neurobiology, and the Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
| | - Ying Chen
- The Institutes of Brain Science, The State Key Laboratory of Medical Neurobiology, and the Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
| | - Man Wang
- The Institutes of Brain Science, The State Key Laboratory of Medical Neurobiology, and the Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
| | - Yinghan Zhuang
- The Institutes of Brain Science, The State Key Laboratory of Medical Neurobiology, and the Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
| | - Thomas Behnisch
- The Institutes of Brain Science, The State Key Laboratory of Medical Neurobiology, and the Collaborative Innovation Center for Brain Science, Fudan University Shanghai, China
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15
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Gao J, Hirata M, Mizokami A, Zhao J, Takahashi I, Takeuchi H, Hirata M. Differential role of SNAP-25 phosphorylation by protein kinases A and C in the regulation of SNARE complex formation and exocytosis in PC12 cells. Cell Signal 2015; 28:425-437. [PMID: 26721188 DOI: 10.1016/j.cellsig.2015.12.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 12/15/2015] [Accepted: 12/21/2015] [Indexed: 11/30/2022]
Abstract
The final step of regulated exocytosis, membrane fusion, is mediated by formation of the SNARE complex by syntaxin, SNAP-25 (synaptosomal-associated protein of 25 kDa), and VAMP (vesicle-associated membrane protein). Phosphorylation of SNARE and accessory proteins contributes to regulation of exocytosis. We previously identified residues of SNAP-25 phosphorylated by protein kinase A (PKA) and PKC. However, the physiological role of SNAP-25 phosphorylation in exocytosis, in particular with regard to SNARE complex formation, has remained elusive. SNARE complex formation by purified recombinant SNAP-25, syntaxin-1, and VAMP-2 in vitro was inhibited or promoted as a result of the phosphorylation at Thr(138) by PKA or at Ser(187) by PKC, respectively. SNARE complex formation in intact PC12 cells was similarly inhibited by forskolin (activator of PKA) and promoted by phorbol 12-myristate 13-acetate (PMA, activator of PKC). Noradrenaline secretion from PC12 cells induced by a high K(+) concentration was enhanced by forskolin or PMA. Stable depletion of SNAP-25 inhibited high-K(+)-induced noradrenaline secretion. Forced expression of WT SNAP-25 restored the secretory response of the SNAP-25-depleted cells to high-K(+), and this response was enhanced by forskolin or PMA. Expression of the nonphosphorylatable T138A or S187A mutants of SNAP-25 similarly rescued the secretory response to high-K(+), but the augmentation of this response by forskolin was more pronounced in the cells expressing SNAP-25 (T138A) than in those expressing SNAP-25 (WT), whereas that by PMA was less pronounced in those expressing SNAP-25 (S187A). Our results thus suggest that SNAP-25 phosphorylation by PKA or PKC contributes differentially to the control of exocytosis in PC12 cells by regulating SNARE complex formation.
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Affiliation(s)
- Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Makiko Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Section of Orthodontics, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Akiko Mizokami
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Jin Zhao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Ichiro Takahashi
- Section of Orthodontics, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Hiroshi Takeuchi
- Division of Applied Pharmacology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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16
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Kiris E, Nuss JE, Stanford SM, Wanner LM, Cazares L, Maestre MF, Du HT, Gomba GY, Burnett JC, Gussio R, Bottini N, Panchal RG, Kane CD, Tessarollo L, Bavari S. Phosphatase Inhibitors Function as Novel, Broad Spectrum Botulinum Neurotoxin Antagonists in Mouse and Human Embryonic Stem Cell-Derived Motor Neuron-Based Assays. PLoS One 2015; 10:e0129264. [PMID: 26061731 PMCID: PMC4462581 DOI: 10.1371/journal.pone.0129264] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/06/2015] [Indexed: 12/05/2022] Open
Abstract
There is an urgent need to develop novel treatments to counter Botulinum neurotoxin (BoNT) poisoning. Currently, the majority of BoNT drug development efforts focus on directly inhibiting the proteolytic components of BoNT, i.e. light chains (LC). Although this is a rational approach, previous research has shown that LCs are extremely difficult drug targets and that inhibiting multi-serotype BoNTs with a single LC inhibitor may not be feasible. An alternative approach would target neuronal pathways involved in intoxication/recovery, rather than the LC itself. Phosphorylation-related mechanisms have been implicated in the intoxication pathway(s) of BoNTs. However, the effects of phosphatase inhibitors upon BoNT activity in the physiological target of BoNTs, i.e. motor neurons, have not been investigated. In this study, a small library of phosphatase inhibitors was screened for BoNT antagonism in the context of mouse embryonic stem cell-derived motor neurons (ES-MNs). Four inhibitors were found to function as BoNT/A antagonists. Subsequently, we confirmed that these inhibitors protect against BoNT/A in a dose-dependent manner in human ES-MNs. Additionally, these compounds provide protection when administered in post-intoxication scenario. Importantly, the inhibitors were also effective against BoNT serotypes B and E. To the best of our knowledge, this is the first study showing phosphatase inhibitors as broad-spectrum BoNT antagonists.
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Affiliation(s)
- Erkan Kiris
- Geneva Foundation, Tacoma, WA, United States of America
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute (NCI), Frederick, MD, United States of America
| | - Jonathan E. Nuss
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - Stephanie M. Stanford
- Division of Cellular Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, United States of America
| | - Laura M. Wanner
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - Lisa Cazares
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - Michael F. Maestre
- Division of Cellular Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, United States of America
| | - Hao T. Du
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - Glenn Y. Gomba
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - James C. Burnett
- Leidos Biomedical Research, Inc., Computational Drug Development Group (CDDG), NCI, Frederick, MD, United States of America
- CDDG, Developmental Therapeutics Program, NCI, Frederick, MD, United States of America
| | - Rick Gussio
- CDDG, Developmental Therapeutics Program, NCI, Frederick, MD, United States of America
| | - Nunzio Bottini
- Division of Cellular Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, United States of America
| | - Rekha G. Panchal
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
| | - Christopher D. Kane
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
- Henry M. Jackson Foundation, Bethesda, MD, United States of America
- DoD Biotechnology High Performance Computing Software Applications Institute (BHSAI), Telemedicine and Advanced Technology Research Center (TATRC), US Army Medical Research and Materiel Command (USAMRMC), Frederick, MD, United States of America
| | - Lino Tessarollo
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute (NCI), Frederick, MD, United States of America
| | - Sina Bavari
- Department of Molecular and Translational Sciences, US Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States of America
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17
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Brozzi F, Lajus S, Diraison F, Rajatileka S, Hayward K, Regazzi R, Molnár E, Váradi A. MyRIP interaction with MyoVa on secretory granules is controlled by the cAMP-PKA pathway. Mol Biol Cell 2012; 23:4444-55. [PMID: 22993210 PMCID: PMC3496617 DOI: 10.1091/mbc.e12-05-0369] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Myosin- and Rab-interacting protein is not a classic receptor for MyoVa on large, dense-core secretory granules (SGs), but it aids in PKA-dependent phosphorylation of MyoVa-associated proteins on SGs in endocrine and neuroendocrine cells. Myosin- and Rab-interacting protein (MyRIP), which belongs to the protein kinase A (PKA)–anchoring family, is implicated in hormone secretion. However, its mechanism of action is not fully elucidated. Here we investigate the role of MyRIP in myosin Va (MyoVa)-dependent secretory granule (SG) transport and secretion in pancreatic beta cells. These cells solely express the brain isoform of MyoVa (BR-MyoVa), which is a key motor protein in SG transport. In vitro pull-down, coimmunoprecipitation, and colocalization studies revealed that MyRIP does not interact with BR-MyoVa in glucose-stimulated pancreatic beta cells, suggesting that, contrary to previous notions, MyRIP does not link this motor protein to SGs. Glucose-stimulated insulin secretion is augmented by incretin hormones, which increase cAMP levels and leads to MyRIP phosphorylation, its interaction with BR-MyoVa, and phosphorylation of the BR-MyoVa receptor rabphilin-3A (Rph-3A). Rph-3A phosphorylation on Ser-234 was inhibited by small interfering RNA knockdown of MyRIP, which also reduced cAMP-mediated hormone secretion. Demonstrating the importance of this phosphorylation, nonphosphorylatable and phosphomimic Rph-3A mutants significantly altered hormone release when PKA was activated. These data suggest that MyRIP only forms a functional protein complex with BR-MyoVa on SGs when cAMP is elevated and under this condition facilitates phosphorylation of SG-associated proteins, which in turn can enhance secretion.
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Affiliation(s)
- Flora Brozzi
- Centre for Research in Biomedicine, Faculty of Health and Life Sciences, University of the West of England, Bristol BS16 1QY, United Kingdom
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18
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Gao J, Takeuchi H, Zhang Z, Fukuda M, Hirata M. Phospholipase C-related but catalytically inactive protein (PRIP) modulates synaptosomal-associated protein 25 (SNAP-25) phosphorylation and exocytosis. J Biol Chem 2012; 287:10565-10578. [PMID: 22311984 DOI: 10.1074/jbc.m111.294645] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Exocytosis is one of the most fundamental cellular events. The basic mechanism of the final step, membrane fusion, is mediated by the formation of the SNARE complex, which is modulated by the phosphorylation of proteins controlled by the concerted actions of protein kinases and phosphatases. We have previously shown that a protein phosphatase-1 (PP1) anchoring protein, phospholipase C-related but catalytically inactive protein (PRIP), has an inhibitory role in regulated exocytosis. The current study investigated the involvement of PRIP in the phospho-dependent modulation of exocytosis. Dephosphorylation of synaptosome-associated protein of 25 kDa (SNAP-25) was mainly catalyzed by PP1, and the process was modulated by wild-type PRIP but not by the mutant (F97A) lacking PP1 binding ability in in vitro studies. We then examined the role of PRIP in phospho-dependent regulation of exocytosis in cell-based studies using pheochromocytoma cell line PC12 cells, which secrete noradrenalin. Exogenous expression of PRIP accelerated the dephosphorylation process of phosphorylated SNAP-25 after forskolin or phorbol ester treatment of the cells. The phospho-states of SNAP-25 were correlated with noradrenalin secretion, which was enhanced by forskolin or phorbol ester treatment and modulated by PRIP expression in PC12 cells. Both SNAP-25 and PP1 were co-precipitated in anti-PRIP immunocomplex isolated from PC12 cells expressing PRIP. Collectively, together with our previous observation regarding the roles of PRIP in PP1 regulation, these results suggest that PRIP is involved in the regulation of the phospho-states of SNAP-25 by modulating the activity of PP1, thus regulating exocytosis.
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Affiliation(s)
- Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan and
| | - Hiroshi Takeuchi
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan and
| | - Zhao Zhang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan and
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan and.
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19
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Connell E, Darios F, Peak-Chew S, Soloviev M, Davletov B. N-terminal acetylation of the neuronal protein SNAP-25 is revealed by the SMI81 monoclonal antibody. Biochemistry 2009; 48:9582-9. [PMID: 19747004 DOI: 10.1021/bi9012403] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The monoclonal antibody SMI81 binds SNAP-25, a major player in neurotransmitter release, with high affinity and has previously been used to follow changes in the levels of this protein in neuropsychiatric disorders. We report here that the SMI81 epitope is present at the extreme N-terminus of SNAP-25 and, unusually, cannot be recognized when present as an internal sequence. Although it is known that SNAP-25 can be palmitoylated and phosphorylated in brain, we now reveal the existence of a third modification, acetylation of the N-terminus. This acetylation event greatly increases the efficiency of SMI81 antibody binding. We show that this highly specific antibody can be used for studying brain function in many vertebrate organisms.
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Affiliation(s)
- Emma Connell
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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20
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Petrov AM, Giniatullin AR, Zefirov AL. Role of the cAMP cascade in the turnover of synaptic vesicles of the frog motor nerve terminal. NEUROCHEM J+ 2008. [DOI: 10.1134/s1819712408030069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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21
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Pozzi D, Condliffe S, Bozzi Y, Chikhladze M, Grumelli C, Proux-Gillardeaux V, Takahashi M, Franceschetti S, Verderio C, Matteoli M. Activity-dependent phosphorylation of Ser187 is required for SNAP-25-negative modulation of neuronal voltage-gated calcium channels. Proc Natl Acad Sci U S A 2008; 105:323-8. [PMID: 18162553 PMCID: PMC2224210 DOI: 10.1073/pnas.0706211105] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Indexed: 11/18/2022] Open
Abstract
Synaptosomal-associated protein of 25 kDa (SNAP-25) is a SNARE protein that regulates neurotransmission by the formation of a complex with syntaxin 1 and synaptobrevin/VAMP2. SNAP-25 also reduces neuronal calcium responses to stimuli, but neither the functional relevance nor the molecular mechanisms of this modulation have been clarified. In this study, we demonstrate that hippocampal slices from Snap25(+/-) mice display a significantly larger facilitation and that higher calcium peaks are reached after depolarization by Snap25(-/-) and Snap25(+/-) cultured neurons compared with wild type. We also show that SNAP-25b modulates calcium dynamics by inhibiting voltage-gated calcium channels (VGCCs) and that PKC phosphorylation of SNAP-25 at ser187 is essential for this process, as indicated by the use of phosphomimetic (S187E) or nonphosphorylated (S187A) mutants. Neuronal activity is the trigger that induces the transient phosphorylation of SNAP-25 at ser187. Indeed, enhancement of network activity increases the levels of phosphorylated SNAP-25, whereas network inhibition reduces the extent of protein phosphorylation. A transient peak of SNAP-25 phosphorylation also is detectable in rat hippocampus in vivo after i.p. injection with kainate to induce seizures. These findings demonstrate that differences in the expression levels of SNAP-25 impact on calcium dynamics and neuronal plasticity, and that SNAP-25 phosphorylation, by promoting inhibition of VGCCs, may mediate a negative feedback modulation of neuronal activity during intense activation.
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Affiliation(s)
- Davide Pozzi
- *Department of Medical Pharmacology and Consiglio Nazionale delle Ricerche–Institute of Neuroscience, University of Milano, Via Vanvitelli 32, 20129 Milan, Italy
- Italian Institute of Technology, Via Morego 30, 16163 Genoa, Italy
| | - Steven Condliffe
- *Department of Medical Pharmacology and Consiglio Nazionale delle Ricerche–Institute of Neuroscience, University of Milano, Via Vanvitelli 32, 20129 Milan, Italy
| | - Yuri Bozzi
- Consiglio Nazionale delle Ricerche Institute of Neuroscience, Via G. Moruzzi 1, 56100 Pisa, Italy
| | - Maia Chikhladze
- Istituto Neurologico C. Besta, Via Celoria 11, 20133 Milan, Italy
| | - Carlotta Grumelli
- *Department of Medical Pharmacology and Consiglio Nazionale delle Ricerche–Institute of Neuroscience, University of Milano, Via Vanvitelli 32, 20129 Milan, Italy
| | | | - Masami Takahashi
- Department of Biochemistry, Kitasato University School of Medicine, Kanagawa 228-8555, Japan
| | | | - Claudia Verderio
- *Department of Medical Pharmacology and Consiglio Nazionale delle Ricerche–Institute of Neuroscience, University of Milano, Via Vanvitelli 32, 20129 Milan, Italy
| | - Michela Matteoli
- *Department of Medical Pharmacology and Consiglio Nazionale delle Ricerche–Institute of Neuroscience, University of Milano, Via Vanvitelli 32, 20129 Milan, Italy
- **Istituto di Ricovero e Cura a Carattere Scientifico Fondazione Don C. Gnocchi, 20129 Milan, Italy; and
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22
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Abstract
G-proteins (guanine nucleotide-binding proteins) are membrane-attached proteins composed of three subunits, alpha, beta, and gamma. They transduce signals from G-protein coupled receptors (GPCRs) to target effector proteins. The agonistactivated receptor induces a conformational change in the G-protein trimer so that the alpha-subunit binds GTP in exchange for GDP and alpha-GTP, and betagamma-subunits separate to interact with the target effector. Effector-interaction is terminated by the alpha-subunit GTPase activity, whereby bound GTP is hydrolyzed to GDP. This is accelerated in situ by RGS proteins, acting as GTPase-activating proteins (GAPs). Galpha-GDP and Gbetagamma then reassociate to form the Galphabetagamma trimer. G-proteins primarily involved in the modulation of neurotransmitter release are G(o), G(q) and G(s). G(o) mediates the widespread presynaptic auto-inhibitory effect of many neurotransmitters (e.g., via M2/M4 muscarinic receptors, alpha(2) adrenoreceptors, micro/delta opioid receptors, GABAB receptors). The G(o) betagamma-subunit acts in two ways: first, and most ubiquitously, by direct binding to CaV2 Ca(2+) channels, resulting in a reduced sensitivity to membrane depolarization and reduced Ca(2+) influx during the terminal action potential; and second, through a direct inhibitory effect on the transmitter release machinery, by binding to proteins of the SNARE complex. G(s) and G(q) are mainly responsible for receptor-mediated facilitatory effects, through activation of target enzymes (adenylate cyclase, AC and phospholipase-C, PLC respectively) by the GTP-bound alpha-subunits.
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Affiliation(s)
- David A Brown
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Cunha DA, Roma LP, Boschero AC. Prolactin modulates the association and phosphorylation of SNARE and kinesin/MAP-2 proteins in neonatal pancreatic rat islets. Mol Cell Endocrinol 2007; 273:32-41. [PMID: 17573185 DOI: 10.1016/j.mce.2007.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 05/02/2007] [Accepted: 05/08/2007] [Indexed: 11/18/2022]
Abstract
Prolactin induces maturation of insulin secretion in cultured neonatal rat islets. In this study, we investigated whether the improved secretory response to glucose caused by prolactin involves alteration in the expression, association and phosphorylation of several proteins that participate in these processes. Messenger RNA was extracted from neonatal rat islets cultured for 5 days in the presence of prolactin and reverse transcribed. Gene expression was analyzed by semi-quantitative RT-PCR and by Western blotting for proteins. The gene transcription and protein expression of kinesin and MAP-2 were increased in prolactin-treated islets compared to the controls. The association and phosphorylation of proteins was analyzed by immunoprecipitation followed by Western blotting, after acute exposure to prolactin. Prolactin increased the association between SNARE proteins and kinesin/MAP-2 while the association of munc-18/syntaxin 1A was decreased. Serine phosphorylation of SNAP-25, syntaxin 1A, munc-18, MAP-2 was significantly higher whereas kinesin phosphorylation was decreased in prolactin-treated islets. There was an increase in SNARE complex formation in islets stimulated with prolactin, 22 mM glucose, 40 mM K(+), 200 microM carbachol and 1 microM PMA. The prolactin-induced increase in the formation of SNARE complex and syntaxin 1A phosphorylation was inhibited by PD098059 and U0126, inhibitors of the MAPK pathway. These findings indicate that prolactin primes pancreatic beta-cells to release insulin by increasing the expression and phosphorylation/association of proteins implicated in the secretory machinery and the MAPK/PKC pathway is important for this effect.
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Affiliation(s)
- Daniel A Cunha
- Department of Physiology and Biophysics, Institute of Biology, State University of Campinas (UNICAMP), CP 6109, Campinas 13083-970, SP, Brazil
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Yang Y, Craig TJ, Chen X, Ciufo LF, Takahashi M, Morgan A, Gillis KD. Phosphomimetic mutation of Ser-187 of SNAP-25 increases both syntaxin binding and highly Ca2+-sensitive exocytosis. ACTA ACUST UNITED AC 2007; 129:233-44. [PMID: 17325194 PMCID: PMC2151612 DOI: 10.1085/jgp.200609685] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The phosphorylation targets that mediate the enhancement of exocytosis by PKC are unknown. PKC phosporylates the SNARE protein SNAP-25 at Ser-187. We expressed mutants of SNAP-25 using the Semliki Forest Virus system in bovine adrenal chromaffin cells and then directly measured the Ca2+ dependence of exocytosis using photorelease of caged Ca2+ together with patch-clamp capacitance measurements. A flash of UV light used to elevate [Ca2+]i to several μM and release the highly Ca2+-sensitive pool (HCSP) of vesicles was followed by a train of depolarizing pulses to elicit exocytosis from the less Ca2+-sensitive readily releasable pool (RRP) of vesicles. Carbon fiber amperometry confirmed that the amount and kinetics of catecholamine release from individual granules were similar for the two phases of exocytosis. Mimicking PKC phosphorylation with expression of the S187E SNAP-25 mutant resulted in an approximately threefold increase in the HCSP, whereas the response to depolarization increased only 1.5-fold. The phosphomimetic S187D mutation resulted in an ∼1.5-fold increase in the HCSP but a 30% smaller response to depolarization. In vitro binding assays with recombinant SNARE proteins were performed to examine shifts in protein–protein binding that may promote the highly Ca2+-sensitive state. The S187E mutant exhibited increased binding to syntaxin but decreased Ca2+-independent binding to synaptotagmin I. Mimicking phosphorylation of the putative PKA phosphorylation site of SNAP-25 with the T138E mutation decreased binding to both syntaxin and synaptotagmin I in vitro. Expressing the T138E/ S187E double mutant in chromaffin cells demonstrated that enhancing the size of the HCSP correlates with an increase in SNAP-25 binding to syntaxin in vitro, but not with Ca2+-independent binding of SNAP-25 to synaptotagmin I. Our results support the hypothesis that exocytosis triggered by lower Ca2+ concentrations (from the HCSP) occurs by different molecular mechanisms than exocytosis triggered by higher Ca2+ levels.
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Affiliation(s)
- Yan Yang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
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25
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Doyle ME, Egan JM. Mechanisms of action of glucagon-like peptide 1 in the pancreas. Pharmacol Ther 2007; 113:546-93. [PMID: 17306374 PMCID: PMC1934514 DOI: 10.1016/j.pharmthera.2006.11.007] [Citation(s) in RCA: 474] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 11/27/2006] [Indexed: 12/13/2022]
Abstract
Glucagon-like peptide 1 (GLP-1) is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate, and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past 20 years culminating in a naturally occurring GLP-1 receptor (GLP-1R) agonist, exendin 4 (Ex-4), now being used to treat type 2 diabetes mellitus (T2DM). GLP-1 engages a specific guanine nucleotide-binding protein (G-protein) coupled receptor (GPCR) that is present in tissues other than the pancreas (brain, kidney, lung, heart, and major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting beta cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1R activation, adenylyl cyclase (AC) is activated and cAMP is generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the protein kinase A (PKA) and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1R activation also increases insulin synthesis, beta cell proliferation, and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in T2DM patients treated with Ex-4. This review will focus on the effects resulting from GLP-1R activation in the pancreas.
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Affiliation(s)
- Máire E Doyle
- Department of Pathology, Immunology & Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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26
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Rutter GA, Tsuboi T, Ravier MA. Ca2+ microdomains and the control of insulin secretion. Cell Calcium 2006; 40:539-51. [PMID: 17030367 DOI: 10.1016/j.ceca.2006.08.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 08/23/2006] [Indexed: 11/19/2022]
Abstract
Nutrient-induced increases in intracellular free Ca(2+) concentrations are the key trigger for insulin release from pancreatic islet beta-cells. These Ca(2+) changes are tightly regulated temporally, occurring as Ca(2+) influx-dependent baseline oscillations. We explore here the concept that locally high [Ca(2+)] concentrations (i.e. Ca(2+) microdomains) may control exocytosis via the recruitment of key effector proteins to sites of exocytosis. Importantly, recent advances in the development of organelle- and membrane-targeted green fluorescent protein (GFP-) or aequorin-based Ca(2+) indicators, as well as in rapid imaging techniques, are providing new insights into the potential role of these Ca(2+) microdomains in beta-cells. We summarise here some of the evidence indicating that Ca(2+) microdomains beneath the plasma membrane and at the surface of large dense core vesicles may be important in the normal regulation of insulin secretion, and may conceivably contribute to "ATP-sensitive K(+)-channel independent" effects of glucose. We also discuss evidence that, in contrast to certain non-excitable cells, direct transfer of Ca(2+) from the ER to mitochondria via localised physical contacts between these organelles is relatively less important for efficient mitochondrial Ca(2+) uptake in beta-cells. Finally, we discuss evidence from single cell imaging that increases in cytosolic Ca(2+) are not required for the upstroke of oscillations in mitochondrial redox state, but may underlie the reoxidation process.
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Affiliation(s)
- Guy A Rutter
- Department of Cell Biology, Division of Medicine, Imperial College London, Sir Alexander Fleming Building, London, UK.
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27
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Kataoka M, Kuwahara R, Matsuo R, Sekiguchi M, Inokuchi K, Takahashi M. Development- and activity-dependent regulation of SNAP-25 phosphorylation in rat brain. Neurosci Lett 2006; 407:258-62. [PMID: 16978778 DOI: 10.1016/j.neulet.2006.08.055] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 08/21/2006] [Accepted: 08/22/2006] [Indexed: 11/22/2022]
Abstract
Synaptosomal-associated protein of 25kDa (SNAP-25), a member of the SNARE proteins essential for neurotransmitter release, is phosphorylated at Ser(187) in PC12 cells and in the rat brain in a protein kinase C-dependent manner. It remains unclear how the phosphorylation of SNAP-25 is regulated during development and by neuronal activity. We studied the mode of SNAP-25 phosphorylation at Ser(187) in the rat brain using an anti-phosphorylated SNAP-25 antibody. Both the expression and phosphorylation of SNAP-25 increased remarkably during the early postnatal period, but their onsets were quite different. SNAP-25 expression was detected as early as embryonic Day 18, whereas the phosphorylation of SNAP-25 could not be detected until postnatal Day 4. A delay in the onset of phosphorylation was also observed in cultured rat hippocampal neurons. The phosphorylation of SNAP-25 was regulated in a neuronal activity-dependent manner and, in the rat hippocampus, decreased by introducing seizures with kainic acid. These results clearly indicated that the phosphorylation of SNAP-25 at Ser(187) is regulated in development- and neuronal activity-dependent manners, and is likely to play important roles in higher brain functions.
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Affiliation(s)
- Masakazu Kataoka
- Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Wakasato 4-17-1, Nagano-shi, Nagano, Japan
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28
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Houeland G, Nakhost A, Sossin WS, Castellucci VF. PKC modulation of transmitter release by SNAP-25 at sensory-to-motor synapses in aplysia. J Neurophysiol 2006; 97:134-43. [PMID: 16971689 DOI: 10.1152/jn.00122.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of phosphokinase C (PKC) can increase transmitter release at sensory-motor neuron synapses in Aplysia, but the target of PKC phosphorylation has not been determined. One putative target of PKC at synapses is the synaptosomal-associated protein of 25 kDa (SNAP-25), a member of the SNARE protein complex implicated in synaptic vesicle docking and fusion. To determine whether PKC regulated transmitter release through phosphorylation of SNAP-25, we cloned Aplysia SNAP-25 and expressed enhanced green fluorescent protein (EGFP)-coupled SNAP-25 constructs mutated at the PKC phosphorylation site Ser198 in Aplysia sensory neurons. We found several distinct effects of expression of EGFP-SNAP-25 constructs. First, the rates of synaptic depression were slowed when cells contained SNAP-25 with phosphomimetic residues Glu or Asp. Second, PDBu-mediated increases in transmitter release at naïve synapses were blocked in cells expressing nonphosphorylated-state SNAP-25. Finally, expression of EGFP-coupled SNAP-25 but not uncoupled SNAP-25 inhibited 5-HT-mediated reversal of depression and the ability of EGFP-coupled SNAP-25 to inhibit the reversal of depression was affected by changes at Ser198. These results suggest SNAP-25 and phosphorylation of SNAP-25 by PKC can regulate transmitter release at Aplysia sensory-motor neuron synapses by a number of distinct processes.
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Affiliation(s)
- Gry Houeland
- Department of Physiology, University of Montreal, Montreal, Quebec, Canada
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29
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Lu HC, Butts DA, Kaeser PS, She WC, Janz R, Crair MC. Role of efficient neurotransmitter release in barrel map development. J Neurosci 2006; 26:2692-703. [PMID: 16525048 PMCID: PMC6675166 DOI: 10.1523/jneurosci.3956-05.2006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cortical maps are remarkably precise, with organized arrays of thalamocortical afferents (TCAs) that project into distinct neuronal modules. Here, we present evidence for the involvement of efficient neurotransmitter release in mouse cortical barrel map development using barrelless mice, a loss-of-function mutant of calcium/calmodulin-activated adenylyl cyclase I (AC1), and mice with a mutation in Rab3-interacting molecule 1alpha (RIM1alpha), an active zone protein that regulates neurotransmitter release. We demonstrate that release efficacy is substantially decreased in barrelless TCAs. We identify RIMs as important phosphorylation targets for AC1 in the presynaptic terminal. We further show that RIM1alpha mutant mice have reduced TCA neurotransmitter release efficacy and barrel map deficits, although not as severe as those found in barrelless mice. This supports the role of RIM proteins in mediating, in part, AC1 signaling in barrel map development. Finally, we present a model to show how inadequacies in presynaptic function can interfere with activity-dependent processes in neuronal circuit formation. These results demonstrate how efficient synaptic transmission mediated by AC1 function contributes to the development of cortical barrel maps.
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Affiliation(s)
- Hui-Chen Lu
- Department of Neuroscience, Program in Developmental Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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30
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Abstract
PKC (protein kinase C) has been known for many years to modulate regulated exocytosis in a wide variety of cell types. In neurons and neuroendocrine cells, PKC regulates several different stages of the exocytotic process, suggesting that these multiple actions of PKC are mediated by phosphorylation of distinct protein targets. In recent years, a variety of exocytotic proteins have been identified as PKC substrates, the best characterized of which are SNAP-25 (25 kDa synaptosome-associated protein) and Munc18. In the present study, we review recent evidence suggesting that site-specific phosphorylation of SNAP-25 and Munc18 by PKC regulates distinct stages of exocytosis.
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31
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Abstract
Stimulus-secretion coupling is an essential process in secretory cells in which regulated exocytosis occurs, including neuronal, neuroendocrine, endocrine, and exocrine cells. While an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) is the principal signal, other intracellular signals also are important in regulated exocytosis. In particular, the cAMP signaling system is well known to regulate and modulate exocytosis in a variety of secretory cells. Until recently, it was generally thought that the effects of cAMP in regulated exocytosis are mediated by activation of cAMP-dependent protein kinase (PKA), a major cAMP target, followed by phosphorylation of the relevant proteins. Although the involvement of PKA-independent mechanisms has been suggested in cAMP-regulated exocytosis by pharmacological approaches, the molecular mechanisms are unknown. Newly discovered cAMP-GEF/Epac, which belongs to the cAMP-binding protein family, exhibits guanine nucleotide exchange factor activities and exerts diverse effects on cellular functions including hormone/transmitter secretion, cell adhesion, and intracellular Ca(2+) mobilization. cAMP-GEF/Epac mediates the PKA-independent effects on cAMP-regulated exocytosis. Thus cAMP regulates and modulates exocytosis by coordinating both PKA-dependent and PKA-independent mechanisms. Localization of cAMP within intracellular compartments (cAMP compartmentation or compartmentalization) may be a key mechanism underlying the distinct effects of cAMP in different domains of the cell.
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Affiliation(s)
- Susumu Seino
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
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32
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Baba T, Sakisaka T, Mochida S, Takai Y. PKA-catalyzed phosphorylation of tomosyn and its implication in Ca2+-dependent exocytosis of neurotransmitter. J Cell Biol 2005; 170:1113-25. [PMID: 16186257 PMCID: PMC2171531 DOI: 10.1083/jcb.200504055] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Accepted: 08/22/2005] [Indexed: 12/24/2022] Open
Abstract
Neurotransmitter is released from nerve terminals by Ca2+-dependent exocytosis through many steps. SNARE proteins are key components at the priming and fusion steps, and the priming step is modulated by cAMP-dependent protein kinase (PKA), which causes synaptic plasticity. We show that the SNARE regulatory protein tomosyn is directly phosphorylated by PKA, which reduces its interaction with syntaxin-1 (a component of SNAREs) and enhances the formation of the SNARE complex. Electrophysiological studies using cultured superior cervical ganglion (SCG) neurons revealed that this enhanced formation of the SNARE complex by the PKA-catalyzed phosphorylation of tomosyn increased the fusion-competent readily releasable pool of synaptic vesicles and, thereby, enhanced neurotransmitter release. This mechanism was indeed involved in the facilitation of neurotransmitter release that was induced by a potent biological mediator, the pituitary adenylate cyclase-activating polypeptide, in SCG neurons. We describe the roles and modes of action of PKA and tomosyn in Ca2+-dependent neurotransmitter release.
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Affiliation(s)
- Takeshi Baba
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita 565-0871, Japan
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33
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Barclay JW, Morgan A, Burgoyne RD. Calcium-dependent regulation of exocytosis. Cell Calcium 2005; 38:343-53. [PMID: 16099500 DOI: 10.1016/j.ceca.2005.06.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 11/30/2022]
Abstract
A rapid increase in intracellular calcium directly triggers regulated exocytosis. In addition, changes in intracellular calcium concentration can adjust the extent of exocytosis (quantal content) or the magnitude of individual release events (quantal size) in both the short- and long-term. It is generally agreed that calcium achieves this regulation via an interaction with a number of different molecular targets located at or near to the site of membrane fusion. We review here the synaptic proteins with defined calcium-binding domains and protein kinases activated by calcium, summarize what is known about their function in membrane fusion and the experimental evidence in support of their involvement in synaptic plasticity.
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Affiliation(s)
- Jeff W Barclay
- Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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34
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Leenders AM, Sheng ZH. Modulation of neurotransmitter release by the second messenger-activated protein kinases: implications for presynaptic plasticity. Pharmacol Ther 2005; 105:69-84. [PMID: 15626456 PMCID: PMC1804289 DOI: 10.1016/j.pharmthera.2004.10.012] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Activity-dependent modulation of synaptic function and structure is emerging as one of the key mechanisms underlying synaptic plasticity. Whereas over the past decade considerable progress has been made in identifying postsynaptic mechanisms for synaptic plasticity, the presynaptic mechanisms involved have remained largely elusive. Recent evidence implicates that second messenger regulation of the protein interactions in synaptic vesicle release machinery is one mechanism by which cellular events modulate synaptic transmission. Thus, identifying protein kinases and their targets in nerve terminals, particularly those functionally regulated by synaptic activity or intracellular [Ca2+], is critical to the elucidation of the molecular mechanisms underlying modulation of neurotransmitter release and presynaptic plasticity. The phosphorylation and dephosphorylation states of synaptic proteins that mediate vesicle exocytosis could regulate the biochemical pathways leading from synaptic vesicle docking to fusion. However, functional evaluation of the activity-dependent phosphorylation events for modulating presynaptic functions still represents a considerable challenge. Here, we present a brief overview of the data on the newly identified candidate targets of the second messenger-activated protein kinases in the presynaptic release machinery and discuss the potential impact of these phosphorylation events in synaptic strength and presynaptic plasticity.
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Affiliation(s)
| | - Zu-Hang Sheng
- * Corresponding author. Tel.: 301 435 4596; fax: 301 480 5763. E-mail address: (Z.-H. Sheng)
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35
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Hepp R, Puri N, Hohenstein AC, Crawford GL, Whiteheart SW, Roche PA. Phosphorylation of SNAP-23 Regulates Exocytosis from Mast Cells. J Biol Chem 2005; 280:6610-20. [PMID: 15611044 DOI: 10.1074/jbc.m412126200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulated exocytosis is a process in which a physiological trigger initiates the translocation, docking, and fusion of secretory granules with the plasma membrane. A class of proteins termed SNAREs (including SNAP-23, syntaxins, and VAMPs) are known regulators of secretory granule/plasma membrane fusion events. We have investigated the molecular mechanisms of regulated exocytosis in mast cells and find that SNAP-23 is phosphorylated when rat basophilic leukemia mast cells are triggered to degranulate. The kinetics of SNAP-23 phosphorylation mirror the kinetics of exocytosis. We have identified amino acid residues Ser(95) and Ser(120) as the major phosphorylation sites in SNAP-23 in rodent mast cells. Quantitative analysis revealed that approximately 10% of SNAP-23 was phosphorylated when mast cell degranulation was induced. These same residues were phosphorylated when mouse platelet degranulation was induced with thrombin, demonstrating that phosphorylation of SNAP-23 Ser(95) and Ser(120) is not restricted to mast cells. Although triggering exocytosis did not alter the absolute amount of SNAP-23 bound to SNAREs, after stimulation essentially all of the SNAP-23 bound to the plasma membrane SNARE syntaxin 4 and the vesicle SNARE VAMP-2 was phosphorylated. Regulated exocytosis studies revealed that overexpression of SNAP-23 phosphorylation mutants inhibited exocytosis from rat basophilic leukemia mast cells, demonstrating that phosphorylation of SNAP-23 on Ser(120) and Ser(95) modulates regulated exocytosis by mast cells.
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Affiliation(s)
- Régine Hepp
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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36
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Boczan J, Leenders AGM, Sheng ZH. Phosphorylation of Syntaphilin by cAMP-dependent Protein Kinase Modulates Its Interaction with Syntaxin-1 and Annuls Its Inhibitory Effect on Vesicle Exocytosis. J Biol Chem 2004; 279:18911-9. [PMID: 14985338 DOI: 10.1074/jbc.m400496200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
cAMP-dependent protein kinase (PKA) can modulate synaptic transmission by acting directly on the neurotransmitter secretory machinery. Here, we identify one possible target: syntaphilin, which was identified as a molecular clamp that controls free syntaxin-1 and dynamin-1 availability and thereby regulates synaptic vesicle exocytosis and endocytosis. Deletion mutation and site-directed mutagenesis experiments pinpoint dominant PKA phosphorylation sites to serines 43 and 56. PKA phosphorylation of syntaphilin significantly decreases its binding to syntaxin-1A in vitro. A syntaphilin mutation of serine 43 to aspartic acid (S43D) shows similar effects on binding. To characterize in vivo phosphorylation events, we generated antisera against a peptide of syntaphilin containing a phosphorylated serine 43. Treatment of rat brain synaptosomes or syntaphilin-transfected HEK 293 cells with the cAMP analogue BIMPS induces in vivo phosphorylation of syntaphilin and inhibits its interaction with syntaxin-1 in neurons. To determine whether PKA phosphorylation of syntaphilin is involved in the regulation of Ca(2+)-dependent exocytosis, we investigated the effect of overexpression of syntaphilin and its S43D mutant on the regulated secretion of human growth hormone from PC12 cells. Although expression of wild type syntaphilin in PC12 cells exhibits significant reduction in high K(+)-induced human growth hormone release, the S43D mutant fails to inhibit exocytosis. Our data predict that syntaphilin could be a highly regulated molecule and that PKA phosphorylation could act as an "off" switch for syntaphilin, thus blocking its inhibitory function via the cAMP-dependent signal transduction pathway.
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Affiliation(s)
- Judit Boczan
- Synaptic Function Unit, National Institute of Neurological Dideases and Stroke, National Institutes of Health, Bethesda, Maryland 20892-4154, USA
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37
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Nagy G, Reim K, Matti U, Brose N, Binz T, Rettig J, Neher E, Sørensen JB. Regulation of releasable vesicle pool sizes by protein kinase A-dependent phosphorylation of SNAP-25. Neuron 2004; 41:417-29. [PMID: 14766180 DOI: 10.1016/s0896-6273(04)00038-8] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Revised: 12/02/2003] [Accepted: 01/07/2004] [Indexed: 11/18/2022]
Abstract
Protein kinase A (PKA) is a key regulator of neurosecretion, but the molecular targets remain elusive. We combined pharmacological manipulations of kinase and phosphatase activities with mutational studies on the exocytotic machinery driving fusion of catecholamine-containing vesicles from chromaffin cells. We found that constitutive PKA activity was necessary to maintain a large number of vesicles in the release-ready, so-called primed, state, whereas calcineurin (protein phosphatase 2B) activity antagonized this effect. Overexpression of the SNARE protein SNAP-25a mutated in a PKA phosphorylation site (Thr-138) eliminated the effect of PKA inhibitors on the vesicle priming process. Another, unidentified, PKA target regulated the relative size of two different primed vesicle pools that are distinguished by their release kinetics. Overexpression of the SNAP-25b isoform increased the size of both primed vesicle pools by a factor of two, and mutations in the conserved Thr-138 site had similar effects as in the a isoform.
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Affiliation(s)
- Gábor Nagy
- Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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38
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Logan MR, Odemuyiwa SO, Moqbel R. Understanding exocytosis in immune and inflammatory cells: The molecular basis of mediator secretion. J Allergy Clin Immunol 2003. [DOI: 10.1016/s0091-6749(03)80114-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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