1
|
ADGRL1 haploinsufficiency causes a variable spectrum of neurodevelopmental disorders in humans and alters synaptic activity and behavior in a mouse model. Am J Hum Genet 2022; 109:1436-1457. [PMID: 35907405 PMCID: PMC9388395 DOI: 10.1016/j.ajhg.2022.06.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/22/2022] [Indexed: 02/06/2023] Open
Abstract
ADGRL1 (latrophilin 1), a well-characterized adhesion G protein-coupled receptor, has been implicated in synaptic development, maturation, and activity. However, the role of ADGRL1 in human disease has been elusive. Here, we describe ten individuals with variable neurodevelopmental features including developmental delay, intellectual disability, attention deficit hyperactivity and autism spectrum disorders, and epilepsy, all heterozygous for variants in ADGRL1. In vitro, human ADGRL1 variants expressed in neuroblastoma cells showed faulty ligand-induced regulation of intracellular Ca2+ influx, consistent with haploinsufficiency. In vivo, Adgrl1 was knocked out in mice and studied on two genetic backgrounds. On a non-permissive background, mice carrying a heterozygous Adgrl1 null allele exhibited neurological and developmental abnormalities, while homozygous mice were non-viable. On a permissive background, knockout animals were also born at sub-Mendelian ratios, but many Adgrl1 null mice survived gestation and reached adulthood. Adgrl1-/- mice demonstrated stereotypic behaviors, sexual dysfunction, bimodal extremes of locomotion, augmented startle reflex, and attenuated pre-pulse inhibition, which responded to risperidone. Ex vivo synaptic preparations displayed increased spontaneous exocytosis of dopamine, acetylcholine, and glutamate, but Adgrl1-/- neurons formed synapses in vitro poorly. Overall, our findings demonstrate that ADGRL1 haploinsufficiency leads to consistent developmental, neurological, and behavioral abnormalities in mice and humans.
Collapse
|
2
|
Diochot S. Pain-related toxins in scorpion and spider venoms: a face to face with ion channels. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20210026. [PMID: 34925480 PMCID: PMC8667759 DOI: 10.1590/1678-9199-jvatitd-2021-0026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/10/2021] [Indexed: 12/12/2022] Open
Abstract
Pain is a common symptom induced during envenomation by spiders and scorpions.
Toxins isolated from their venom have become essential tools for studying the
functioning and physiopathological role of ion channels, as they modulate their
activity. In particular, toxins that induce pain relief effects can serve as a
molecular basis for the development of future analgesics in humans. This review
provides a summary of the different scorpion and spider toxins that directly
interact with pain-related ion channels, with inhibitory or stimulatory effects.
Some of these toxins were shown to affect pain modalities in different animal
models providing information on the role played by these channels in the pain
process. The close interaction of certain gating-modifier toxins with membrane
phospholipids close to ion channels is examined along with molecular approaches
to improve selectivity, affinity or bioavailability in vivo for
therapeutic purposes.
Collapse
Affiliation(s)
- Sylvie Diochot
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS) UMR 7275 et Université Côte d'Azur (UCA), 06560 Valbonne, France. Institut de Pharmacologie Moléculaire et Cellulaire Centre National de la Recherche Scientifique Université Côte d'Azur Valbonne France
| |
Collapse
|
3
|
Chen M, Blum D, Engelhard L, Raunser S, Wagner R, Gatsogiannis C. Molecular architecture of black widow spider neurotoxins. Nat Commun 2021; 12:6956. [PMID: 34845192 PMCID: PMC8630228 DOI: 10.1038/s41467-021-26562-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 10/11/2021] [Indexed: 12/14/2022] Open
Abstract
Latrotoxins (LaTXs) are presynaptic pore-forming neurotoxins found in the venom of Latrodectus spiders. The venom contains a toxic cocktail of seven LaTXs, with one of them targeting vertebrates (α-latrotoxin (α-LTX)), five specialized on insects (α, β, γ, δ, ε- latroinsectotoxins (LITs), and one on crustaceans (α-latrocrustatoxin (α-LCT)). LaTXs bind to specific receptors on the surface of neuronal cells, inducing the release of neurotransmitters either by directly stimulating exocytosis or by forming Ca2+-conductive tetrameric pores in the membrane. Despite extensive studies in the past decades, a high-resolution structure of a LaTX is not yet available and the precise mechanism of LaTX action remains unclear. Here, we report cryoEM structures of the α-LCT monomer and the δ-LIT dimer. The structures reveal that LaTXs are organized in four domains. A C-terminal domain of ankyrin-like repeats shields a central membrane insertion domain of six parallel α-helices. Both domains are flexibly linked via an N-terminal α-helical domain and a small β-sheet domain. A comparison between the structures suggests that oligomerization involves major conformational changes in LaTXs with longer C-terminal domains. Based on our data we propose a cyclic mechanism of oligomerization, taking place prior membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca2+ ions and allow calcium flux at negative membrane potentials. Our comparative analysis between α-LCT and δ-LIT provides first crucial insights towards understanding the molecular mechanism of the LaTX family. The venom of Latrodectus spiders contains seven Latrotoxins (LaTXs), among them α-latrocrustatoxin (LCT) and δ- latroinsectotoxins δ-LIT. LaTXs bind to specific receptors on the surface of neuronal cells and target the molecular exocytosis machinery. Here, the authors present the cryo-EM structure of the α-LCT monomer and the δ-LIT dimer, which reveal that LaTXs are organized in four domains and they discuss the potential oligomerisation mechanism that takes place before LaTXs membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca2+ ions.
Collapse
Affiliation(s)
- Minghao Chen
- Institute for Medical Physics and Biophysics and Center for Soft Nanoscience, Westfälische Wilhelms Universität Münster, 48149, Münster, Germany.,Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Daniel Blum
- MOLIFE Research Center, Jacobs University Bremen, 28759, Bremen, Germany
| | - Lena Engelhard
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Richard Wagner
- MOLIFE Research Center, Jacobs University Bremen, 28759, Bremen, Germany
| | - Christos Gatsogiannis
- Institute for Medical Physics and Biophysics and Center for Soft Nanoscience, Westfälische Wilhelms Universität Münster, 48149, Münster, Germany. .,Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany.
| |
Collapse
|
4
|
Føns S, Ledsgaard L, Nikolaev MV, Vassilevski AA, Sørensen CV, Chevalier MK, Fiebig M, Laustsen AH. Discovery of a Recombinant Human Monoclonal Immunoglobulin G Antibody Against α-Latrotoxin From the Mediterranean Black Widow Spider ( Latrodectus tredecimguttatus). Front Immunol 2020; 11:587825. [PMID: 33262768 PMCID: PMC7688514 DOI: 10.3389/fimmu.2020.587825] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 10/19/2020] [Indexed: 12/26/2022] Open
Abstract
Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient's history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future.
Collapse
Affiliation(s)
- Sofie Føns
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Line Ledsgaard
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Maxim V. Nikolaev
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Alexander A. Vassilevski
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Christoffer V. Sørensen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Manon K. Chevalier
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | | | - Andreas H. Laustsen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| |
Collapse
|
5
|
Melland H, Carr EM, Gordon SL. Disorders of synaptic vesicle fusion machinery. J Neurochem 2020; 157:130-164. [PMID: 32916768 DOI: 10.1111/jnc.15181] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/20/2020] [Accepted: 08/26/2020] [Indexed: 12/11/2022]
Abstract
The revolution in genetic technology has ushered in a new age for our understanding of the underlying causes of neurodevelopmental, neuromuscular and neurodegenerative disorders, revealing that the presynaptic machinery governing synaptic vesicle fusion is compromised in many of these neurological disorders. This builds upon decades of research showing that disturbance to neurotransmitter release via toxins can cause acute neurological dysfunction. In this review, we focus on disorders of synaptic vesicle fusion caused either by toxic insult to the presynapse or alterations to genes encoding the key proteins that control and regulate fusion: the SNARE proteins (synaptobrevin, syntaxin-1 and SNAP-25), Munc18, Munc13, synaptotagmin, complexin, CSPα, α-synuclein, PRRT2 and tomosyn. We discuss the roles of these proteins and the cellular and molecular mechanisms underpinning neurological deficits in these disorders.
Collapse
Affiliation(s)
- Holly Melland
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Elysa M Carr
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| |
Collapse
|
6
|
Rahman MA, Manser C, Benlaouer O, Suckling J, Blackburn JK, Silva JP, Ushkaryov YA. C-terminal phosphorylation of latrophilin-1/ADGRL1 affects the interaction between its fragments. Ann N Y Acad Sci 2019; 1456:122-143. [PMID: 31553068 DOI: 10.1111/nyas.14242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 07/22/2019] [Accepted: 09/05/2019] [Indexed: 12/21/2022]
Abstract
Latrophilin-1 is an adhesion G protein-coupled receptor that mediates the effect of α-latrotoxin, causing massive release of neurotransmitters from nerve terminals and endocrine cells. Autoproteolysis cleaves latrophilin-1 into two parts: the extracellular N-terminal fragment (NTF) and the heptahelical C-terminal fragment (CTF). NTF and CTF can exist as independent proteins in the plasma membrane, but α-latrotoxin binding to NTF induces their association and G protein-mediated signaling. We demonstrate here that CTF in synapses is phosphorylated on multiple sites. Phosphorylated CTF has a high affinity for NTF and copurifies with it on affinity columns and sucrose density gradients. Dephosphorylated CTF has a lower affinity for NTF and can behave as a separate protein. α-Latrotoxin (and possibly other ligands of latrophilin-1) binds both to the NTF-CTF complex and receptor-like protein tyrosine phosphatase σ, bringing them together. This leads to CTF dephosphorylation and facilitates CTF release from the complex. We propose that ligand-dependent phosphorylation-dephosphorylation of latrophilin-1 could affect the interaction between its fragments and functions as a G protein-coupled receptor.
Collapse
Affiliation(s)
- M Atiqur Rahman
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Catherine Manser
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Ouafa Benlaouer
- School of Pharmacy, University of Kent, Chatham, United Kingdom
| | - Jason Suckling
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - John-Paul Silva
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Yuri A Ushkaryov
- Department of Life Sciences, Imperial College London, London, United Kingdom
- School of Pharmacy, University of Kent, Chatham, United Kingdom
| |
Collapse
|
7
|
Sakhnevych SS, Yasinska IM, Bratt AM, Benlaouer O, Gonçalves Silva I, Hussain R, Siligardi G, Fiedler W, Wellbrock J, Gibbs BF, Ushkaryov YA, Sumbayev VV. Cortisol facilitates the immune escape of human acute myeloid leukemia cells by inducing latrophilin 1 expression. Cell Mol Immunol 2018; 15:994-997. [PMID: 29907881 DOI: 10.1038/s41423-018-0053-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 05/22/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
| | - Inna M Yasinska
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK
| | - Alison M Bratt
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK
| | - Ouafa Benlaouer
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK
| | | | | | | | - Walter Fiedler
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald University Cancer Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jasmin Wellbrock
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald University Cancer Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Bernhard F Gibbs
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK.,Department of Medicine, Dermatology and Allergology, University of Oldenburg, Oldenburg, Germany
| | - Yuri A Ushkaryov
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK
| | - Vadim V Sumbayev
- Medway School of Pharmacy, Universities of Kent and Greenwich, Chatham Maritime, UK.
| |
Collapse
|
8
|
Gao S, Xiong W, Wei L, Liu J, Liu X, Xie J, Song X, Bi J, Li B. Transcriptome profiling analysis reveals the role of latrophilin in controlling development, reproduction and insecticide susceptibility in Tribolium castaneum. Genetica 2018; 146:287-302. [DOI: 10.1007/s10709-018-0020-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 04/30/2018] [Indexed: 12/23/2022]
|
9
|
de Roodt AR, Lanari LC, Laskowicz RD, Costa de Oliveira V, Irazu LE, González A, Giambelluca L, Nicolai N, Barragán JH, Ramallo L, López RA, Lopardo J, Jensen O, Larrieu E, Calabró A, Vurcharchuc MG, Lago NR, García SI, de Titto EH, Damín CF. Toxicity of the venom of Latrodectus (Araneae: Theridiidae) spiders from different regions of Argentina and neutralization by therapeutic antivenoms. Toxicon 2017; 130:63-72. [DOI: 10.1016/j.toxicon.2017.02.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 10/20/2022]
|
10
|
Martinez AF, Muenke M, Arcos-Burgos M. From the black widow spider to human behavior: Latrophilins, a relatively unknown class of G protein-coupled receptors, are implicated in psychiatric disorders. Am J Med Genet B Neuropsychiatr Genet 2011; 156B:1-10. [PMID: 21184579 PMCID: PMC4101183 DOI: 10.1002/ajmg.b.31137] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 09/28/2010] [Indexed: 12/24/2022]
Abstract
The findings of a recent study associate LPHN3, a member of the latrophilin family, with an increased risk of developing attention deficit/hyperactivity disorder (ADHD), the most common psychiatric disorder in childhood and adolescence. Latrophilins comprise a new family of G protein-coupled receptors of unknown native physiological function that mediate the neurotoxic effects of α-latrotoxin, a potent toxin found in black widow spider venom. This receptor-toxin interaction has helped to elucidate the mechanistic aspects of neurotransmitter and hormone release in vertebrates. Such unprecedented discovery points to a new direction in the assessment of ADHD and suggest that further study of this receptor family may provide novel insights into the etiology and treatment of ADHD and other related psychiatric conditions.
Collapse
Affiliation(s)
| | | | - Mauricio Arcos-Burgos
- Correspondence to: Dr. Mauricio Arcos-Burgos, M.D., Ph.D., National Human Genome Research Institute, National Institutes of Health, 35 Convent Drive, MSC 3717, Building 35, Room 1B209, Bethesda, MD 20892.
| |
Collapse
|
11
|
|
12
|
Abstract
For more than three decades, the venom of the black widow spider and its principal active components, latrotoxins, have been used to induce release of neurotransmitters and hormones and to study the mechanisms of exocytosis. Given the complex nature of alpha--latrotoxin (alpha-LTX) actions, this research has been continuously overshadowed by many enigmas, misconceptions and perpetual changes of the underlying hypotheses. Some of the toxin's mechanisms of action are still not completely understood. Despite all these difficulties, the extensive work of several generations of neurobiologists has brought about a great deal of fascinating insights into pre-synaptic processes and has led to the discovery of several novel proteins and synaptic systems. For example, alpha-LTX studies have contributed to the widespread acceptance of the vesicular theory of transmitter release. Pre-synaptic receptors for alpha-LTX--neurexins, latrophilins and protein tyrosine phosphatase sigma--and their endogenous ligands have now become centrepieces of their own areas of research, with a potential of uncovering new mechanisms of synapse formation and regulation that may have medical implications. However, any future success of alpha-LTX research will require a better understanding of this unusual natural tool and a more precise dissection of its multiple mechanisms.
Collapse
Affiliation(s)
- John-Paul Silva
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London, UK
| | | | | |
Collapse
|
13
|
Silva JP, Lelianova V, Hopkins C, Volynski KE, Ushkaryov Y. Functional cross-interaction of the fragments produced by the cleavage of distinct adhesion G-protein-coupled receptors. J Biol Chem 2009; 284:6495-506. [PMID: 19124473 DOI: 10.1074/jbc.m806979200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The unusual adhesion G-protein-coupled receptors (aGPCRs) contain large extracellular N-terminal domains, which resemble cell-adhesion receptors, and C-terminal heptahelical domains, which may couple to G-proteins. These receptors are cleaved post-translationally between these domains into two fragments (NTF and CTF). Using the aGPCR latrophilin 1, we previously demonstrated that the fragments behave as independent cell-surface proteins. Upon binding the agonist, alpha-latrotoxin (LTX), latrophilin fragments reassemble and induce intracellular signaling. Our observations raised important questions: is the aGPCR signaling mediated by reassembled fragments or by any non-cleaved receptors? Also, can the fragments originating from distinct aGPCRs form hybrid complexes? To answer these questions, we created two types of chimerical constructs. One contained the CTF of latrophilin joined to the NTF of another aGPCR, EMR2; the resulting protein did not bind LTX but, similar to latrophilin, could couple to G-proteins. In another construct, the NTF of latrophilin was fused with the C terminus of neurexin; this chimera bound LTX but could not signal via G-proteins. Both constructs were efficiently cleaved in cells. When the two constructs were co-expressed, their fragments could cross-interact, as shown by immunoprecipitation. Furthermore, LTX(N4C) induced intracellular Ca2+ signaling only in cells expressing both constructs but not each individual construct. Finally, we demonstrated that fragments of unrelated aGPCRs can be cross-immunoprecipitated from live tissues. Thus, (i) aGPCR fragments behave as independent proteins, (ii) the complementary fragments from distinct aGPCRs can cross-interact, and (iii) these cross-complexes are functionally active. This unusual cross-assembly of aGPCR fragments could couple cell-surface interactions to multiple signaling pathways.
Collapse
Affiliation(s)
- John-Paul Silva
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | | | | | | | | |
Collapse
|
14
|
Martineau M, Galli T, Baux G, Mothet JP. Confocal imaging and tracking of the exocytotic routes for D-serine-mediated gliotransmission. Glia 2008; 56:1271-84. [PMID: 18615566 DOI: 10.1002/glia.20696] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
D-Serine is an astrocyte-derived regulator for N-methyl-D-aspartate receptors, but the intracellular routes of its trafficking are still largely unknown. Here, we combined confocal microscopy with colocalization quantification to track the astrocytic organelles that store D-serine. We report that D-serine colocalizes with the transfected eGFP-synaptobrevin/VAMP2 and eGFP-cellubrevin/VAMP3, two v-SNAREs of the regulated secretory pathway. No significant colocalization was found with markers of the endosomal sorting and recycling system: EEA1, eGFP-endobrevin/VAMP8, eGFP-TI-VAMP/VAMP7, LAMP1, and CD63. Blockade of vesicular budding with colchicine shows that secretory vesicles import D-serine downstream to the Golgi apparatus. Finally, treatment of astrocytes with the Ca2+-ionophore A23187, glutamate agonists, or bradykinin trigger translocation of synaptobrevin/VAMP2 to the plasma membrane with a concomitant disappearance of D-serine from the regulated secretory pathway. Our results provide morphological evidence for a vesicular storage of D-serine in the regulated secretory pathway and the possible recruitment of these stores by Ca2+ mobilization to release D-serine.
Collapse
Affiliation(s)
- Magalie Martineau
- CNRS, Institut de Neurobiologie Alfred Fessard, FRC 2118, Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR 9040, F-91198 Gif-sur-Yvette, France
| | | | | | | |
Collapse
|
15
|
Latrophilin is an essential gene and mediates the toxicity of black widow spider venom in C. elegans. Toxicology 2008. [DOI: 10.1016/j.tox.2008.07.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
16
|
Abstract
alpha-Latrotoxin (alpha-LTX) from black widow spider venom induces exhaustive release of neurotransmitters from vertebrate nerve terminals and endocrine cells. This 130-kDa protein has been employed for many years as a molecular tool to study exocytosis. However, its action is complex: in neurons, alpha-LTX induces massive secretion both in the presence of extracellular Ca(2+) (Ca(2+) (e)) and in its absence; in endocrine cells, it usually requires Ca(2+) (e). To use this toxin for further dissection of secretory mechanisms, one needs an in-depth understanding of its functions. One such function that explains some alpha-LTX effects is its ability to form cation-permeable channels in artificial lipid bilayers. The mechanism of alpha-LTX pore formation, revealed by cryo-electron microscopy, involves toxin assembly into homotetrameric complexes which harbor a central channel and can insert into lipid membranes. However, in biological membranes, alpha-LTX cannot exert its actions without binding to specific receptors of the plasma membrane. Three proteins with distinct structures have been found to bind alpha-LTX: neurexin Ialpha, latrophilin 1, and receptor-like protein tyrosine phosphatase sigma. Upon binding a receptor, alpha-LTX forms channels permeable to cations and small molecules; the toxin may also activate the receptor. To distinguish between the pore- and receptor-mediated effects, and to study structure-function relationships in the toxin, alpha-LTX mutants have been used.
Collapse
Affiliation(s)
- Yuri A Ushkaryov
- Division of Cell and Molecular Biology, Imperial College London, London, SW7 2AY, UK.
| | | | | |
Collapse
|
17
|
Berninghausen O, Rahman MA, Silva JP, Davletov B, Hopkins C, Ushkaryov YA. Neurexin Ibeta and neuroligin are localized on opposite membranes in mature central synapses. J Neurochem 2007; 103:1855-63. [PMID: 17868325 PMCID: PMC2517655 DOI: 10.1111/j.1471-4159.2007.04918.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Synaptogenesis requires formation of trans-synaptic complexes between neuronal cell-adhesion receptors. Heterophilic receptor pairs, such as neurexin Ibeta and neuroligin, can mediate distinct intracellular signals and form different cytoplasmic scaffolds in the pre- and post-synaptic neuron, and may be particularly important for synaptogenesis. However, the functions of neurexin and neuroligin depend on their distribution in the synapse. Neuroligin has been experimentally assigned to the post-synaptic membrane, while the localization of neurexin remains unclear. To study the subcellular distribution of neurexin Ibeta and neuroligin in mature cerebrocortical synapses, we have developed a novel method for the physical separation of junctional membranes and their direct analysis by western blotting. Using urea and dithiothreitol, we disrupted trans-synaptic protein links, without dissolving the lipid phase, and fractionated the pre- and post-synaptic membranes. The purity of these fractions was validated by electron microscopy and western blotting using multiple synaptic markers. A quantitative analysis has confirmed that neuroligin is localized strictly in the post-synaptic membrane. We have also demonstrated that neurexin Ibeta is largely (96%) pre-synaptic. Thus, neurexin Ibeta and neuroligin normally form trans-synaptic complexes and can transduce bidirectional signals.
Collapse
Affiliation(s)
- Otto Berninghausen
- Division of Cell and Molecular Biology, Imperial College London, London, UK
| | | | | | | | | | | |
Collapse
|
18
|
Rohou A, Nield J, Ushkaryov Y. Insecticidal toxins from black widow spider venom. Toxicon 2006; 49:531-49. [PMID: 17210168 PMCID: PMC2517654 DOI: 10.1016/j.toxicon.2006.11.021] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 11/17/2006] [Indexed: 11/27/2022]
Abstract
The biological effects of Latrodectus spider venom are similar in animals from different phyla, but these symptoms are caused by distinct phylum-specific neurotoxins (collectively called latrotoxins) with molecular masses ranging from 110 to 140 kDa. To date, the venom has been found to contain five insecticidal toxins, termed α, β, γ, δ and ε-latroinsectotoxins (LITs). There is also a vertebrate-specific neurotoxin, α-latrotoxin (α-LTX), and one toxin affecting crustaceans, α-latrocrustatoxin (α-LCT). These toxins stimulate massive release of neurotransmitters from nerve terminals and act (1) by binding to specific receptors, some of which mediate an exocytotic signal, and (2) by inserting themselves into the membrane and forming ion-permeable pores. Specific receptors for LITs have yet to be identified, but all three classes of vertebrate receptors known to bind α-LTX are also present in insects. All LTXs whose structures have been elucidated (α-LIT, δ-LIT, α-LTX and α-LCT) are highly homologous and have a similar domain architecture, which consists of a unique N-terminal sequence and a large domain composed of 13–22 ankyrin repeats. Three-dimensional (3D) structure analysis, so far done for α-LTX only, has revealed its dimeric nature and an ability to form symmetrical tetramers, a feature probably common to all LTXs. Only tetramers have been observed to insert into membranes and form pores. A preliminary 3D reconstruction of a δ-LIT monomer demonstrates the spatial similarity of this toxin to the monomer of α-LTX.
Collapse
Affiliation(s)
| | | | - Y.A. Ushkaryov
- Corresponding author. Tel.: +44 20 7594 5237; fax: +44 20 7594 5207.
| |
Collapse
|
19
|
Schenning M, Proctor DT, Ragnarsson L, Barbier J, Lavidis NA, Molgó JJ, Zamponi GW, Schiavo G, Meunier FA. Glycerotoxin stimulates neurotransmitter release from N-type Ca2+ channel expressing neurons. J Neurochem 2006; 98:894-904. [PMID: 16749905 DOI: 10.1111/j.1471-4159.2006.03938.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glycerotoxin (GLTx) is capable of stimulating neurotransmitter release at the frog neuromuscular junction by directly interacting with N-type Ca2+ (Cav2.2) channels. Here we have utilized GLTx as a tool to investigate the functionality of Cav2.2 channels in various mammalian neuronal preparations. We first adapted a fluorescent-based high-throughput assay to monitor glutamate release from rat cortical synaptosomes. GLTx potently stimulates glutamate secretion and Ca2+ influx in synaptosomes with an EC50 of 50 pm. Both these effects were prevented using selective Cav2.2 channel blockers suggesting the functional involvement of Cav2.2 channels in mediating glutamate release in this system. We further show that both Cav2.1 (P/Q-type) and Cav2.2 channels contribute equally to depolarization-induced glutamate release. We then investigated the functionality of Cav2.2 channels at the neonatal rat neuromuscular junction. GLTx enhances both spontaneous and evoked neurotransmitter release causing a significant increase in the frequency of postsynaptic action potentials. These effects were blocked by specific Cav2.2 channel blockers demonstrating that either GLTx or its derivatives could be used to selectively enhance the neurotransmitter release from Cav2.2-expressing mammalian neurons.
Collapse
Affiliation(s)
- Mitja Schenning
- Molecular Dynamics of Synaptic Function Laboratory, The School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Li G, Lee D, Wang L, Khvotchev M, Chiew SK, Arunachalam L, Collins T, Feng ZP, Sugita S. N-terminal insertion and C-terminal ankyrin-like repeats of alpha-latrotoxin are critical for Ca2+-dependent exocytosis. J Neurosci 2006; 25:10188-97. [PMID: 16267226 PMCID: PMC6725796 DOI: 10.1523/jneurosci.3560-05.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-latrotoxin, a potent stimulator of exocytosis from neurons and neuroendocrine cells, has been studied intensively, but the mechanisms of its actions are poorly understood. Here, we developed a new method to generate active recombinant alpha-latrotoxin and conducted a structure/function analysis of the toxin in stimulating Ca2+-dependent exocytosis. alpha-Latrotoxin consists of a conserved N-terminal domain and C-terminal ankyrin-like repeats. After cleavage of an N-terminally fused purification tag of glutathione S-transferase (GST), the recombinant toxin strongly stimulated exocytosis, whereas the GST-fused toxin was much less potent. The GST-fused toxin bound to the receptors [neurexin 1alpha; CL1 (CIRL/latrophilin 1)] as efficiently as did the GST-cleaved toxin but was much less effective in inserting into the plasma membrane and inducing cation conductance. The toxin with deletion of the last two ankyrin-like repeats still bound the receptors but could neither stimulate exocytosis nor induce cation conductance efficiently. The abilities of the mutated toxins to stimulate exocytosis correlated well with their abilities to induce cation conductance, but not their binding to the receptors. Our results indicate that (1) C-terminal ankyrin-like repeats and a free (unfused) N terminus are both required for the toxin to form pores, which is essential for Ca2+-dependent exocytosis, and (2) receptor binding alone is not sufficient to stimulate Ca2+-dependent exocytosis.
Collapse
Affiliation(s)
- Gang Li
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario, M5T 2S8, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Lajus S, Vacher P, Huber D, Dubois M, Benassy MN, Ushkaryov Y, Lang J. α-Latrotoxin Induces Exocytosis by Inhibition of Voltage-dependent K+ Channels and by Stimulation of L-type Ca2+ Channels via Latrophilin in β-Cells. J Biol Chem 2006; 281:5522-31. [PMID: 16301314 DOI: 10.1074/jbc.m510528200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The spider venom alpha-latrotoxin (alpha-LTX) induces massive exocytosis after binding to surface receptors, and its mechanism is not fully understood. We have investigated its action using toxin-sensitive MIN6 beta-cells, which express endogenously the alpha-LTX receptor latrophilin (LPH), and toxin-insensitive HIT-T15 beta-cells, which lack endogenous LPH. alpha-LTX evoked insulin exocytosis in HIT-T15 cells only upon expression of full-length LPH but not of LPH truncated after the first transmembrane domain (LPH-TD1). In HIT-T15 cells expressing full-length LPH and in native MIN6 cells, alpha-LTX first induced membrane depolarization by inhibition of repolarizing K(+) channels followed by the appearance of Ca(2+) transients. In a second phase, the toxin induced a large inward current and a prominent increase in intracellular calcium ([Ca(2+)](i)) reflecting pore formation. Upon expression of LPH-TD1 in HIT-T15 cells just this second phase was observed. Moreover, the mutated toxin LTX(N4C), which is devoid of pore formation, only evoked oscillations of membrane potential by reversible inhibition of iberiotoxin-sensitive K(+) channels via phospholipase C, activated L-type Ca(2+) channels independently from its effect on membrane potential, and induced an inositol 1,4,5-trisphosphate receptor-dependent release of intracellular calcium in MIN6 cells. The combined effects evoked transient increases in [Ca(2+)](i) in these cells, which were sensitive to inhibitors of phospholipase C, protein kinase C, or L-type Ca(2+) channels. The latter agents also reduced toxin-induced insulin exocytosis. In conclusion, alpha-LTX induces signaling distinct from pore formation via full-length LPH and phospholipase C to regulate physiologically important K(+) and Ca(2+) channels as novel targets of its secretory activity.
Collapse
Affiliation(s)
- Sophie Lajus
- Institut Européen de Chimie et Biologie, JE 2390 and INSERM E347, 2 rue Robert Escarpit, 33607 Pessac/Bordeaux, France
| | | | | | | | | | | | | |
Collapse
|
22
|
α-LTX and α-LTXN4C induce [Ca2+]i elevation through different mechanisms in pancreatic β cells. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/s11434-005-1029-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
23
|
Lajus S, Lang J. Splice variant 3, but not 2 of receptor protein-tyrosine phosphatase σ can mediate stimulation of insulin-secretion by α-latrotoxin. J Cell Biochem 2006; 98:1552-9. [PMID: 16552719 DOI: 10.1002/jcb.20871] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Alpha-latrotoxin (alpha-LTX) binds to several cell surface receptors including receptor protein-tyrosine phosphatase sigma (RPTPsigma). Here we demonstrate that transient overexpression of the short splice variant 3 conferred alpha-LTX induced secretion to hamster insulinoma (HIT-15) cells. In contrast, the long splice variant 2 containing four additional extracellular fibronectin-III domains was inactive in secretion or in a single cell assay. Toxin-sensitive (MIN6) and toxin-insensitive (HIT-T15) insulinoma cell lines as well as PC12 cells expressed similar amounts of endogenous short RPTPsigma splice variant suggesting that this receptor does not play a role for toxin-sensitivity.
Collapse
Affiliation(s)
- Sophie Lajus
- Institut Européen de Chimie et Biologie, JE 2390, F-33607 Bordeaux/Pessac, France
| | | |
Collapse
|
24
|
Dolly JO. Molecular definition of neuronal targets for novel neurotherapeutics: SNAREs and Kv1 channels. Neurotoxicology 2005; 26:753-60. [PMID: 16125246 DOI: 10.1016/j.neuro.2005.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Accepted: 05/25/2005] [Indexed: 01/16/2023]
Affiliation(s)
- J Oliver Dolly
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland.
| |
Collapse
|
25
|
Andreev IA, Danilevich VN, Grishin EV. [Alternative splicing of pre-mRNA encoding the Musca domestica latrophilin-like protein(LLP): primary structures of four spliced forms of mRNA and their protein products]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2005; 31:175-85. [PMID: 15889792 DOI: 10.1007/s11171-005-0022-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
An internal DNA fragment (approximately 2000 bp) homologous to the conserved regions of genes encoding latrophilin-like proteins (LLPs) was obtained by the PCR technique using degenerate primers to these gene regions. The gene-specific primers were synthesized based on the results of sequencing of the isolated fragment, and all overlapping cDNA fragments of the llp gene encoding the Musca domestica LLP were obtained by the rapid amplification of cDNA 5'- and 3'-ends (5'- and 3'-RACE). Four alternatively spliced mRNAs were found while sequencing the obtained cDNA fragments. Two long mRNAs (approximately 6000 nt) differ in the structures of both the sites encoding signal peptides and 5'-terminal untranslated regions. They encode large proteins (approximately 1800 aa), whose domain organization is similar to that of mammalian latrophilins. Each deduced protein contains a domain with seven transmembrane regions followed by an extended cytoplasmic C-terminal domain. Two other mRNA forms are derived from these long mRNAs; they encode proteins severly truncated at their C-termini (approximately 900 aa). They are composed of only three transmembrane regions and a short unique cytoplasmic C-terminal domain (23 aa). The limitations and drawbacks of the existing 3'-RACE techniques found during study of the long alternatively spliced cDNAs are analyzed, and ways for overcoming these difficulties are proposed.
Collapse
|
26
|
Liu J, Wan Q, Lin X, Zhu H, Volynski K, Ushkaryov Y, Xu T. α-Latrotoxin Modulates the Secretory Machinery via Receptor-Mediated Activation of Protein Kinase C. Traffic 2005; 6:756-65. [PMID: 16101679 DOI: 10.1111/j.1600-0854.2005.00313.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The hypothesis whether alpha-latrotoxin (LTX) could directly regulate the secretory machinery was tested in pancreatic beta cells using combined techniques of membrane capacitance (Cm) measurement and Ca2+ uncaging. Employing ramp increase in [Ca2+]i to stimulate exocytosis, we found that LTX lowers the Ca2+ threshold required for exocytosis without affecting the size of the readily releasable pool (RRP). The burst component of exocytosis in response to step-like [Ca2+]i increase generated by flash photolysis of caged Ca2+ was also speeded up by LTX treatment. LTX increased the maximum rate of exocytosis compared with control responses with similar postflash [Ca2+]i and shifted the Ca2+ dependence of the exocytotic machinery toward lower Ca2+ concentrations. LTXN4C, a LTX mutant which cannot form membrane pores or penetrate through the plasma membrane but has similar affinity for the receptors as the wild-type LTX, mimicked the effect of LTX. Moreover, the effects of both LTX and LTXN4C) were independent of intracellular or extracellular Ca2+ but required extracellular Mg2+. Our data propose that LTX, by binding to the membrane receptors, sensitizes the fusion machinery to Ca2+ and, hence, may permit release at low [Ca2+]i level. This sensitization is mediated by activation of protein kinase C.
Collapse
Affiliation(s)
- Jie Liu
- Institute of Biophysics and Biochemistry, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074. P. R. China
| | | | | | | | | | | | | |
Collapse
|
27
|
Volynski KE, Silva JP, Lelianova VG, Atiqur Rahman M, Hopkins C, Ushkaryov YA. Latrophilin fragments behave as independent proteins that associate and signal on binding of LTX(N4C). EMBO J 2004; 23:4423-33. [PMID: 15483624 PMCID: PMC526461 DOI: 10.1038/sj.emboj.7600443] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Accepted: 09/20/2004] [Indexed: 11/09/2022] Open
Abstract
Heptahelical, or G-protein-coupled, receptors control many cellular functions and normally consist of one polypeptide chain. In contrast, heptahelical receptors that belong to the long N-terminus, group B (LNB) family are cleaved constitutively into two fragments. The N-terminal fragments (NTFs) resemble cell-adhesion proteins and the C-terminal fragments (CTFs) are typical G-protein-coupled receptors (GPCRs) with seven transmembrane regions. However, the functional roles of this cleavage and of any subsequent NTF-CTF interactions remain to be identified. Using latrophilin, a well-studied member of the LNB family, we now demonstrate that cleavage is critical for delivery of this receptor to the cell surface. On the plasma membrane, NTF and CTF behave as separate membrane proteins involved, respectively, in cell-surface reception and signalling. The two fragments can also internalise independently. However, separated NTF and CTF can re-associate on solubilisation. Agonist binding to NTF on the cell surface also induces re-association of fragments and provokes signal transduction via CTF. These findings define a novel principle of structural and functional organisation of the cleaved, two-subunit GPCRs.
Collapse
Affiliation(s)
| | - John-Paul Silva
- Department of Biological Sciences, Imperial College, London, UK
| | | | - M Atiqur Rahman
- Department of Biological Sciences, Imperial College, London, UK
| | - Colin Hopkins
- Department of Biological Sciences, Imperial College, London, UK
| | - Yuri A Ushkaryov
- Department of Biological Sciences, Imperial College, London, UK
- Department of Biological Sciences, Imperial College, London SW7 2AZ, UK. Tel.: +44 20 7594 5237; Fax: +44 20 7594 5207; E-mail:
| |
Collapse
|
28
|
Ushkaryov YA, Volynski KE, Ashton AC. The multiple actions of black widow spider toxins and their selective use in neurosecretion studies. Toxicon 2004; 43:527-42. [PMID: 15066411 DOI: 10.1016/j.toxicon.2004.02.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The black widow spider venom contains several large protein toxins--latrotoxins--that are selectively targeted against different classes of animals: vertebrates, insects, and crustaceans. These toxins are synthesised as large precursors that undergo proteolytic processing and activation in the lumen of the venom gland. The mature latrotoxins demonstrate strong functional structure conservation and contain multiple ankyrin repeats, which mediate toxin oligomerisation. The three-dimensional structure has been determined for alpha-latrotoxin (alphaLTX), a representative venom component toxic to vertebrates. This reconstruction explains the mechanism of alphaLTX pore formation by showing that it forms tetrameric complexes, harbouring a central channel, and that it is able to insert into lipid membranes. All latrotoxins cause massive release of neurotransmitters from nerve terminals of respective animals after binding to specific neuronal receptors. A G protein-coupled receptor latrophilin and a single-transmembrane receptor neurexin have been identified as major high-affinity receptors for alphaLTX. Latrotoxins act by several Ca(2+)-dependent and -independent mechanisms based on pore formation and activation of receptors. Mutant recombinant alphaLTX that does not form pores has been used to dissect the multiple actions of this toxin. As a result, important insights have been gained into the receptor signalling and the role of intracellular Ca(2+) stores in the effect of alphaLTX.
Collapse
Affiliation(s)
- Y A Ushkaryov
- Department of Biological Sciences, Imperial College, London, SW7 2AY, UK.
| | | | | |
Collapse
|
29
|
Mee CJ, Tomlinson SR, Perestenko PV, De Pomerai D, Duce IR, Usherwood PNR, Bell DR. Latrophilin is required for toxicity of black widow spider venom in Caenorhabditis elegans. Biochem J 2004; 378:185-91. [PMID: 14594448 PMCID: PMC1223931 DOI: 10.1042/bj20031213] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 10/14/2003] [Accepted: 10/31/2003] [Indexed: 11/17/2022]
Abstract
Black widow spider venom (BWSV) kills Caenorhabditis elegans after injection owing to the presence of heat- and detergent-sensitive components, which are high-molecular-mass latrotoxins. A C. elegans homologue of latrophilin/CIRL (calcium-independent receptor for latrotoxin), B0457.1, was identified and shown to have five conserved domains. RNAi (RNA interference) of this gene rendered C. elegans resistant to BWSV, whereas RNAi for CYP37A1 or a neurexin I homologue, and a deletion mutant of the related B0286.2 gene, had no effect on BWSV toxicity. The latrophilin RNAi mutants exhibit changes in defaecation cycle and alterations in drug sensitivity. These results demonstrate that latrophilin mediates the toxicity of BWSV and provide evidence for a physiological function of this receptor.
Collapse
Affiliation(s)
- Christopher J Mee
- School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | | | | | | | | | | | | |
Collapse
|
30
|
Volynski KE, Capogna M, Ashton AC, Thomson D, Orlova EV, Manser CF, Ribchester RR, Ushkaryov YA. Mutant alpha-latrotoxin (LTXN4C) does not form pores and causes secretion by receptor stimulation: this action does not require neurexins. J Biol Chem 2003; 278:31058-66. [PMID: 12782639 DOI: 10.1074/jbc.m210395200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alpha-latrotoxin (LTX) causes massive release of neurotransmitters via a complex mechanism involving (i) activation of receptor(s) and (ii) toxin insertion into the plasma membrane with (iii) subsequent pore formation. Using cryo-electron microscopy, electrophysiological and biochemical methods, we demonstrate here that the recently described toxin mutant (LTXN4C) is unable to insert into membranes and form pores due to its inability to assemble into tetramers. However, this mutant still binds to major LTX receptors (latrophilin and neurexin) and causes strong transmitter exocytosis in synaptosomes, hippocampal slice cultures, neuromuscular junctions, and chromaffin cells. In the absence of mutant incorporation into the membrane, receptor activation must be the only mechanism by which LTXN4C triggers exocytosis. An interesting feature of this receptor-mediated transmitter release is its dependence on extracellular Ca2+. Because Ca2+ is also strictly required for LTX interaction with neurexin, the latter might be the only receptor mediating the LTXN4C action. To test this hypothesis, we used conditions (substitution of Ca2+ in the medium with Sr2+) under which LTXN4C does not bind to any member of the neurexin family but still interacts with latrophilin. We show that, in all the systems tested, Sr2+ fully replaces Ca2+ in supporting the stimulatory effect of LTXN4C. These results indicate that LTXN4C can cause neurotransmitter release just by stimulating a receptor and that neurexins are not critical for this receptor-mediated action.
Collapse
Affiliation(s)
- Kirill E Volynski
- Department of Biological Sciences, Imperial College London, London SW7 2AY, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
31
|
The alpha-latrotoxin mutant LTXN4C enhances spontaneous and evoked transmitter release in CA3 pyramidal neurons. J Neurosci 2003. [PMID: 12764091 DOI: 10.1523/jneurosci.23-10-04044.2003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-latrotoxin (LTX) stimulates vesicular exocytosis by at least two mechanisms that include (1) receptor binding-stimulation and (2) membrane pore formation. Here, we use the toxin mutant LTX(N4C) to selectively study the receptor-mediated actions of LTX. LTX(N4C) binds to both LTX receptors (latrophilin and neurexin) and greatly enhances the frequency of spontaneous and miniature EPSCs recorded from CA3 pyramidal neurons in hippocampal slice cultures. The effect of LTX(N4C) is reversible and is not attenuated by La3+ that is known to block LTX pores. On the other hand, LTX(N4C) action, which requires extracellular Ca2+, is inhibited by thapsigargin, a drug depleting intracellular Ca2+ stores, by 2-aminoethoxydiphenyl borate, a blocker of inositol(1,4,5)-trisphosphate-induced Ca2+ release, and by U73122, a phospholipase C inhibitor. Furthermore, measurements using a fluorescent Ca2+ indicator directly demonstrate that LTX(N4C) increases presynaptic, but not dendritic, free Ca2+ concentration; this Ca2+ rise is blocked by thapsigargin, suggesting, together with electrophysiological data, that the receptor-mediated action of LTX(N4C) involves mobilization of Ca2+ from intracellular stores. Finally, in contrast to wild-type LTX, which inhibits evoked synaptic transmission probably attributable to pore formation, LTX(N4C) actually potentiates synaptic currents elicited by electrical stimulation of afferent fibers. We suggest that the mutant LTX(N4C), lacking the ionophore-like activity of wild-type LTX, activates a presynaptic receptor and stimulates Ca2+ release from intracellular stores, leading to the enhancement of synaptic vesicle exocytosis.
Collapse
|
32
|
Linetska MV, Storchak LG, Himmelreich NH. Phenylarsine oxide inhibits alpha-latrotoxin-stimulated [3H]GABA release from rat brain synaptosomes. Neurochem Int 2003; 42:583-90. [PMID: 12590941 DOI: 10.1016/s0197-0186(02)00158-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphatidylinositol 4,5-biphosphate has been implicated in a variety of membrane-trafficking processes, including exocytosis of neurotransmitters. However, there are contradictory findings concerned ability of phenylarsine oxide (PAO), an inhibitor of phosphatidylinositol 4-kinase, to affect exocytotic release of different types of neurotransmitters. We bent our efforts to a detailed analysis of action of PAO on Ca(2+)-dependent and Ca(2+)-independent [3H]GABA release produced by exposure of rat brain synaptosomes to different concentrations of alpha-latrotoxin. We also compared PAO action on alpha-latrotoxin- and 4-aminopyridine (4-AP)-evoked [3H]GABA release. The experiments have shown that release of [3H]GABA evoked by the depolarization with 4-AP was decreased by 80% as a result of action of 3 microM PAO and the complete inhibition of release was observed with 10 microM PAO. When alpha-latrotoxin as a stimulant was applied, release of [3H]GABA was increased as toxin concentration used was elevated from 0.5 to 3.0 nM, however, concomitantly, the response of the toxin-induced [3H]GABA release to PAO became attenuated: 10 microM PAO led to almost complete inhibition of the effect of 0.5 nM alpha-latrotoxin and only partly decreased (by 40%) the response to 3.0 nM alpha-latrotoxin. To test whether the efficacy of PAO depended on the toxin-induced outflow of cytosolic [3H]GABA, synaptosomes with depleted cytosolic [3H]GABA pool were also exploited. Depletion was performed by means of heteroexchange of cytosolic [3H]GABA with nipecotic acid. The experiments have shown that treatment of loaded synaptosomes with nipecotic acid resulted in some increase of [3H]GABA release evoked by 0.5 nM alpha-latrotoxin, but in the two-fold decrease of the response to 3.0 nM alpha-latrotoxin. PAO essentially inhibited [3H]GABA release from depleted synaptosomes irrespective of alpha-latrotoxin concentration used. Therefore, the amount of [3H]GABA released from cytosolic pool determined, in considerable degree, the insensitivity of alpha-latrotoxin action to PAO. Thus, our data show that subnanomolar concentrations of alpha-latrotoxin may be used for stimulation of exocytotic release of [3H]GABA. Exposure of synaptosomes with nanomolar toxin concentrations leads not only to stimulation of exocytosis, but also to leakage of [3H]GABA from cytosolic pool. PAO potently inhibits exocytotic release of [3H]GABA and its inhibitory effectiveness is diminished as far as the outflow of [3H]GABA is elevated.
Collapse
Affiliation(s)
- M V Linetska
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Science of Ukraine, Leontovich Street 9, Kiev 01601, Ukraine
| | | | | |
Collapse
|
33
|
Meunier FA, Feng ZP, Molgó J, Zamponi GW, Schiavo G. Glycerotoxin from Glycera convoluta stimulates neurosecretion by up-regulating N-type Ca2+ channel activity. EMBO J 2002; 21:6733-43. [PMID: 12485994 PMCID: PMC139097 DOI: 10.1093/emboj/cdf677] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report here the purification of glycerotoxin from the venom of Glycera convoluta, a novel 320 kDa protein capable of reversibly stimulating spontaneous and evoked neurotransmitter release at the frog neuromuscular junction. However, glycerotoxin is ineffective at the murine neuromuscular junction, which displays a different subtype of voltage- dependent Ca(2+) channels. By sequential and selective inhibition of various types of Ca(2+) channels, we found that glycerotoxin was acting via Ca(v)2.2 (N-type). In neuroendocrine cells, it elicits a robust, albeit transient, influx of Ca(2+) sensitive to the Ca(v)2.2 blockers omega-conotoxin GVIA and MVIIA. Moreover, glycerotoxin triggers a Ca(2+) transient in human embryonic kidney (HEK) cells over-expressing Ca(v)2.2 but not Ca(v)2.1 (P/Q-type). Whole-cell patch-clamp analysis of Ca(v)2.2 expressing HEK cells revealed an up-regulation of Ca(2+) currents due to a leftward shift of the activation peak upon glycerotoxin addition. A direct interaction between Ca(v)2.2 and this neurotoxin was revealed by co-immunoprecipitation experiments. Therefore, glycerotoxin is a unique addition to the arsenal of tools available to unravel the mechanism controlling Ca(2+)-regulated exocytosis via the specific activation of Ca(v)2.2.
Collapse
Affiliation(s)
- Frédéric A. Meunier
- Molecular Neuropathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada and Laboratoire de Neurobiologie Cellulaire et Moleculaire, UPR 9040, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding authors e-mail: or
| | - Zhong-Ping Feng
- Molecular Neuropathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada and Laboratoire de Neurobiologie Cellulaire et Moleculaire, UPR 9040, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding authors e-mail: or
| | - Jordi Molgó
- Molecular Neuropathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada and Laboratoire de Neurobiologie Cellulaire et Moleculaire, UPR 9040, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding authors e-mail: or
| | - Gerald W. Zamponi
- Molecular Neuropathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada and Laboratoire de Neurobiologie Cellulaire et Moleculaire, UPR 9040, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding authors e-mail: or
| | - Giampietro Schiavo
- Molecular Neuropathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London WC2A 3PX, UK, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive NW, Calgary T2N 4N1, Canada and Laboratoire de Neurobiologie Cellulaire et Moleculaire, UPR 9040, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding authors e-mail: or
| |
Collapse
|
34
|
Ouanounou G, Malo M, Stinnakre J, Kreger AS, Molgo J. Trachynilysin, a neurosecretory protein isolated from stonefish (Synanceia trachynis) venom, forms nonselective pores in the membrane of NG108-15 cells. J Biol Chem 2002; 277:39119-27. [PMID: 12177053 DOI: 10.1074/jbc.m203433200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trachynilysin, a protein toxin isolated from the venom of the stonefish Synanceia trachynis, has been reported to elicit massive acetylcholine release from motor nerve endings of isolated neuromuscular preparations and to increase both cytosolic Ca2+ and catecholamine release from chromaffin cells. In the present study, we used the patch clamp technique to investigate the effect of trachynilysin on the cytoplasmic membrane of differentiated NG108-15 cells in culture. Trachynilysin increased membrane conductance the most when the negativity of the cell holding membrane potential was reduced. The trachynilysin-induced current was carried by cations and reversed at about -3 mV in standard physiological solutions, which led to strong membrane depolarization and Ca2+ influx. La3+ blocked the trachynilysin current in a dose-, voltage-, and time-dependent manner, and antibodies raised against the toxin antagonized its effect on the cell membrane. The inside-out configuration of the patch clamp technique allowed the recording of single channel activity from which various multiples of 22 pS elementary conductance were resolved. These results indicate that trachynilysin forms pores in the NG108-15 cell membrane, and they advance our understanding of the toxin's mode of action on motor nerve endings and neurosecretory cells.
Collapse
Affiliation(s)
- Gilles Ouanounou
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR 9040 CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
| | | | | | | | | |
Collapse
|
35
|
Affiliation(s)
- Y Ushkaryov
- Biochemistry Department, Imperial College, SW7 2AY, London, UK.
| |
Collapse
|
36
|
Ashton AC, Volynski KE, Lelianova VG, Orlova EV, Van Renterghem C, Canepari M, Seagar M, Ushkaryov YA. alpha-Latrotoxin, acting via two Ca2+-dependent pathways, triggers exocytosis of two pools of synaptic vesicles. J Biol Chem 2001; 276:44695-703. [PMID: 11572875 DOI: 10.1074/jbc.m108088200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha-Latrotoxin stimulates three types of [(3)H]gamma-aminobutyric acid and [(14)C]glutamate release from synaptosomes. The Ca(2+)-independent component (i) is insensitive to SNAP-25 cleavage or depletion of vesicle contents by bafilomycin A1 and represents transmitter efflux mediated by alpha-latrotoxin pores. Two other components of release are Ca(2+)-dependent and vesicular but rely on distinct mechanisms. The fast receptor-mediated pathway (ii) involves intracellular Ca(2+) stores and acts upon sucrose-sensitive readily releasable vesicles; this mechanism is insensitive to inhibition of phosphatidylinositol 4-kinase (PI 4-kinase). The delayed pore-dependent exocytotic component (iii) is stimulated by Ca(2+) entering through alpha-latrotoxin pores; it requires PI 4-kinase and occurs mainly from depot vesicles. Lanthanum perturbs alpha-latrotoxin pores and blocks the two pore-mediated components (i, iii) but not the receptor-mediated release (ii). alpha-Latrotoxin mutant (LTX(N4C)) cannot form pores and stimulates only the Ca(2+)-dependent receptor-mediated amino acid exocytosis (ii) (detectable biochemically and electrophysiologically). These findings explain experimental data obtained by different laboratories and implicate the toxin receptors in the regulation of the readily releasable pool of synaptic vesicles. Our results also suggest that, similar to noradrenergic vesicles, amino acid-containing vesicles at some point in their cycle require PI 4-kinase.
Collapse
Affiliation(s)
- A C Ashton
- Biochemistry Department, Imperial College, Exhibition Road, London SW7 2AY, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Hardy SP, Ritchie C, Allen MC, Ashley RH, Granum PE. Clostridium perfringens type A enterotoxin forms mepacrine-sensitive pores in pure phospholipid bilayers in the absence of putative receptor proteins. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1515:38-43. [PMID: 11597350 DOI: 10.1016/s0005-2736(01)00391-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Clostridium perfringens enterotoxin (CPE) is an important cause of food poisoning with no significant homology to other enterotoxins and its mechanism of action remains uncertain. Although CPE has recently been shown to complex with tight junction proteins, we have previously demonstrated that CPE increases ionic permeability in single Caco-2 cells using the whole-cell patch-clamp technique, thereby excluding any paracellular permeability. In this paper we demonstrate that CPE forms pores in synthetic phospholipid membranes in the absence of receptor proteins. The properties of the pores are consistent with CPE-induced permeability changes in Caco-2 cells suggesting that CPE has innate pore-forming ability.
Collapse
Affiliation(s)
- S P Hardy
- Department of Pharmacy and Biomolecular Sciences, University of Brighton, Sussex, UK.
| | | | | | | | | |
Collapse
|