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Joensuu M, Syed P, Saber SH, Lanoue V, Wallis TP, Rae J, Blum A, Gormal RS, Small C, Sanders S, Jiang A, Mahrhold S, Krez N, Cousin MA, Cooper‐White R, Cooper‐White JJ, Collins BM, Parton RG, Balistreri G, Rummel A, Meunier FA. Presynaptic targeting of botulinum neurotoxin type A requires a tripartite PSG-Syt1-SV2 plasma membrane nanocluster for synaptic vesicle entry. EMBO J 2023; 42:e112095. [PMID: 37226896 PMCID: PMC10308369 DOI: 10.15252/embj.2022112095] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 04/18/2023] [Accepted: 04/28/2023] [Indexed: 05/26/2023] Open
Abstract
The unique nerve terminal targeting of botulinum neurotoxin type A (BoNT/A) is due to its capacity to bind two receptors on the neuronal plasma membrane: polysialoganglioside (PSG) and synaptic vesicle glycoprotein 2 (SV2). Whether and how PSGs and SV2 may coordinate other proteins for BoNT/A recruitment and internalization remains unknown. Here, we demonstrate that the targeted endocytosis of BoNT/A into synaptic vesicles (SVs) requires a tripartite surface nanocluster. Live-cell super-resolution imaging and electron microscopy of catalytically inactivated BoNT/A wildtype and receptor-binding-deficient mutants in cultured hippocampal neurons demonstrated that BoNT/A must bind coincidentally to a PSG and SV2 to target synaptic vesicles. We reveal that BoNT/A simultaneously interacts with a preassembled PSG-synaptotagmin-1 (Syt1) complex and SV2 on the neuronal plasma membrane, facilitating Syt1-SV2 nanoclustering that controls endocytic sorting of the toxin into synaptic vesicles. Syt1 CRISPRi knockdown suppressed BoNT/A- and BoNT/E-induced neurointoxication as quantified by SNAP-25 cleavage, suggesting that this tripartite nanocluster may be a unifying entry point for selected botulinum neurotoxins that hijack this for synaptic vesicle targeting.
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Affiliation(s)
- Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
| | - Parnayan Syed
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Saber H Saber
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
| | - Vanessa Lanoue
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - James Rae
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Ailisa Blum
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Rachel S Gormal
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Christopher Small
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Shanley Sanders
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Anmin Jiang
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Stefan Mahrhold
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Nadja Krez
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson BuildingUniversity of EdinburghEdinburghUK
- Muir Maxwell Epilepsy CentreUniversity of EdinburghEdinburghUK
- Simons Initiative for the Developing BrainUniversity of EdinburghEdinburghUK
| | - Ruby Cooper‐White
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
- School of Chemical EngineeringThe University of QueenslandBrisbaneQLDAustralia
| | - Justin J Cooper‐White
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandBrisbaneQLDAustralia
- School of Chemical EngineeringThe University of QueenslandBrisbaneQLDAustralia
- UQ Centre for Stem Cell Ageing and Regenerative EngineeringThe University of QueenslandBrisbaneQLDAustralia
| | - Brett M Collins
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Robert G Parton
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
- Centre for Microscopy and MicroanalysisThe University of QueenslandBrisbaneQLDAustralia
| | - Giuseppe Balistreri
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Department of Virology, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Andreas Rummel
- Institut für ToxikologieMedizinische Hochschule HannoverHannoverGermany
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
- School of Biomedical SciencesThe University of QueenslandBrisbaneQLDAustralia
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2
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Stout KA, Dunn AR, Hoffman C, Miller GW. The Synaptic Vesicle Glycoprotein 2: Structure, Function, and Disease Relevance. ACS Chem Neurosci 2019; 10:3927-3938. [PMID: 31394034 DOI: 10.1021/acschemneuro.9b00351] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The synaptic vesicle glycoprotein 2 (SV2) family is comprised of three paralogues: SV2A, SV2B, and SV2C. In vertebrates, SV2s are 12-transmembrane proteins present on every secretory vesicle, including synaptic vesicles, and are critical to neurotransmission. Structural and functional studies suggest that SV2 proteins may play several roles to promote proper vesicular function. Among these roles are their potential to stabilize the transmitter content of vesicles, to maintain and orient the releasable pool of vesicles, and to regulate vesicular calcium sensitivity to ensure efficient, coordinated release of the transmitter. The SV2 family is highly relevant to human health in a number of ways. First, SV2A plays a role in neuronal excitability and as such is the specific target for the antiepileptic drug levetiracetam. SV2 proteins also act as the target by which potent neurotoxins, particularly botulinum, gain access to neurons and exert their toxicity. Both SV2B and SV2C are increasingly implicated in diseases such as Alzheimer's disease and Parkinson's disease. Interestingly, despite decades of intensive research, their exact function remains elusive. Thus, SV2 proteins are intriguing in their potentially diverse roles within the presynaptic terminal, and several recent developments have enhanced our understanding and appreciation of the protein family. Here, we review the structure and function of SV2 proteins as well as their relevance to disease and therapeutic development.
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Affiliation(s)
- Kristen A Stout
- Department of Physiology , Northwestern University, Feinberg School of Medicine , Chicago , Illinois , United States
| | - Amy R Dunn
- The Jackson Laboratory , Bar Harbor , Maine , United States
| | - Carlie Hoffman
- Department of Environmental Health, Rollins School of Public Health , Emory University , Atlanta , Georgia , United States
| | - Gary W Miller
- Department of Environmental Health Sciences, Mailman School of Public Health , Columbia University , New York , New York , United States
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3
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Chromophore-Assisted Light Inactivation of the V-ATPase V0c Subunit Inhibits Neurotransmitter Release Downstream of Synaptic Vesicle Acidification. Mol Neurobiol 2018; 56:3591-3602. [PMID: 30155790 DOI: 10.1007/s12035-018-1324-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 08/17/2018] [Indexed: 10/28/2022]
Abstract
Synaptic vesicle proton V-ATPase is an essential component in synaptic vesicle function. Active acidification of synaptic vesicles, triggered by the V-ATPase, is necessary for neurotransmitter storage. Independently from its proton transport activity, an additional important function of the membrane-embedded sector of the V-ATPase has been uncovered over recent years. Subunits a and c of the membrane sector of this multi-molecular complex have been shown to interact with SNARE proteins and to be involved in modulating neurotransmitter release. The c-subunit interacts with the v-SNARE VAMP2 and facilitates neurotransmission. In this study, we used chromophore-assisted light inactivation and monitored the consequences on neurotransmission on line in CA3 pyramidal neurons. We show that V-ATPase c-subunit V0c is a key element in modulating neurotransmission and that its specific inactivation rapidly inhibited neurotransmission.
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4
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Surana S, Tosolini AP, Meyer IF, Fellows AD, Novoselov SS, Schiavo G. The travel diaries of tetanus and botulinum neurotoxins. Toxicon 2018; 147:58-67. [DOI: 10.1016/j.toxicon.2017.10.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 10/09/2017] [Accepted: 10/11/2017] [Indexed: 10/18/2022]
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5
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Stern D, Weisemann J, Le Blanc A, von Berg L, Mahrhold S, Piesker J, Laue M, Luppa PB, Dorner MB, Dorner BG, Rummel A. A lipid-binding loop of botulinum neurotoxin serotypes B, DC and G is an essential feature to confer their exquisite potency. PLoS Pathog 2018; 14:e1007048. [PMID: 29718991 PMCID: PMC5951583 DOI: 10.1371/journal.ppat.1007048] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/14/2018] [Accepted: 04/19/2018] [Indexed: 11/21/2022] Open
Abstract
The exceptional toxicity of botulinum neurotoxins (BoNTs) is mediated by high avidity binding to complex polysialogangliosides and intraluminal segments of synaptic vesicle proteins embedded in the presynaptic membrane. One peculiarity is an exposed hydrophobic loop in the toxin’s cell binding domain HC, which is located between the ganglioside- and protein receptor-binding sites, and that is particularly pronounced in the serotypes BoNT/B, DC, and G sharing synaptotagmin as protein receptor. Here, we provide evidence that this HC loop is a critical component of their tripartite receptor recognition complex. Binding to nanodisc-embedded receptors and toxicity were virtually abolished in BoNT mutants lacking residues at the tip of the HC loop. Surface plasmon resonance experiments revealed that only insertion of the HC loop into the lipid-bilayer compensates for the entropic penalty inflicted by the dual-receptor binding. Our results represent a new paradigm of how BoNT/B, DC, and G employ ternary interactions with a protein, ganglioside, and lipids to mediate their extraordinary neurotoxicity. Botulinum neurotoxins are Janus-faced molecules: due to their exquisite toxicity, botulinum neurotoxins are considered as biological weapons, but they are also highly effective medicines for numerous neurological indications. However, what mediates their exquisite toxicity? The exclusive binding to neurons and the subsequent paralysis cuts off the host’s communication networks. The neurospecific binding is ensured by anchoring to two receptor molecules both embedded in the membrane: a complex ganglioside and a synaptic vesicle protein. Here, we reveal a third interaction between a hydrophobic so-called HC loop protruding from the surface of the serotypes BoNT/B, DC, and G into the lipid membrane. Only this HC loop ensures their high-affinity binding to the neuronal receptors also at physiological temperature (37°C). Hereby, BoNT/B, DC, and G prevent untimely dissociation prior to uptake into the neuron. Therefore, our study provides the mechanistic basis for the development of inhibitors to combat botulism, but it also has implications for engineering toxin—membrane interactions yielding optimized BoNT-based therapeutics to treat neuromuscular dysfunctions successfully. Intriguingly, a broadly neutralizing anti-HIV-1 antibody shares a similar strategy, emphasizing the general relevance of our results for host—pathogen interactions.
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Affiliation(s)
- Daniel Stern
- Biological Toxins (ZBS 3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Jasmin Weisemann
- Institut für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Alexander Le Blanc
- Institute for Clinical Chemistry and Pathobiochemistry, Klinikum rechts der Isar, Technische Universität München, München, Germany
| | - Laura von Berg
- Biological Toxins (ZBS 3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Stefan Mahrhold
- Institut für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Janett Piesker
- Advanced Light and Electron Microscopy (ZBS 4), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Michael Laue
- Advanced Light and Electron Microscopy (ZBS 4), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Peter B. Luppa
- Institute for Clinical Chemistry and Pathobiochemistry, Klinikum rechts der Isar, Technische Universität München, München, Germany
| | - Martin Bernhard Dorner
- Biological Toxins (ZBS 3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Brigitte Gertrud Dorner
- Biological Toxins (ZBS 3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
- * E-mail: (BGD); (AR)
| | - Andreas Rummel
- Institut für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
- * E-mail: (BGD); (AR)
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6
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Yu CH, Song DH, Choi JY, Joe HE, Jeong WH, Hur GH, Shin YK, Jeong ST. A mutated recombinant subunit vaccine protects mice and guinea pigs against botulinum type A intoxication. Hum Vaccin Immunother 2018; 14:329-336. [PMID: 29140753 PMCID: PMC5806659 DOI: 10.1080/21645515.2017.1405201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/17/2017] [Accepted: 11/09/2017] [Indexed: 02/08/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are the most potent toxins to mammals. A toxoid vaccine was previously used for prevention of botulinum intoxication; however, this vaccine is no longer available. Currently, no approved botulinum vaccines are available from the Food and Drug Administration (FDA). Recently, a recombinant host cell receptor-binding subunit created for use as a potential vaccine completed phase 2 clinical trials. The current study designed a vaccine candidate against BoNT type A (BoNT/A) using a structural design. Our vaccine candidate was the BoNT/A heavy chain C-terminal region (HCR) that contained the point mutation BA15 (R1269A) within the ganglioside-binding site. A Biacore affinity test showed that the affinity of BA15 for ganglioside GT1b was 100 times lower than that of the HCR. A SNAP25 cleavage assay revealed that immunized sera blocked SNAP25 cleavage of the BoNT/A toxin via BA15. In an in vivo experiment, mice and guinea pigs immunized with BA15 produced neutralizing antibodies that protected against 3,000 LD50 of BoNT/A. In conclusion, the results of both in vitro and in vivo assays showed that our BA15 vaccine candidate was similar to the recombinant host cell receptor-binding subunit vaccine. The inability of BA15to bind ganglioside shows that BA15 is a potential safe vaccine candidate.
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Affiliation(s)
- Chi Ho Yu
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
| | - Dong Hyun Song
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
| | - Jun Young Choi
- Abion R&D Institute, Hanhwa Biz-Metro, Guro-gu, Seoul, Republic of Korea
| | - Hae Eun Joe
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
| | - Woo Hyeon Jeong
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
| | - Gyeung Haeng Hur
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
| | - Young Kee Shin
- Department of Pharmacy, College of Pharmacy, Seoul National University, Dajeon, Seoul, Republic of Korea
| | - Seong Tae Jeong
- Agency for Defense Development, Yuseong, Daejeon, Republic of Korea
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7
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Burns JR, Lambert GS, Baldwin MR. Insights into the Mechanisms by Which Clostridial Neurotoxins Discriminate between Gangliosides. Biochemistry 2017; 56:2571-2583. [DOI: 10.1021/acs.biochem.6b01246] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joshua R. Burns
- Department of Molecular Microbiology
and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | - Gregory S. Lambert
- Department of Molecular Microbiology
and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | - Michael R. Baldwin
- Department of Molecular Microbiology
and Immunology, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
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8
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Vazquez-Cintron EJ, Beske PH, Tenezaca L, Tran BQ, Oyler JM, Glotfelty EJ, Angeles CA, Syngkon A, Mukherjee J, Kalb SR, Band PA, McNutt PM, Shoemaker CB, Ichtchenko K. Engineering Botulinum Neurotoxin C1 as a Molecular Vehicle for Intra-Neuronal Drug Delivery. Sci Rep 2017; 7:42923. [PMID: 28220863 PMCID: PMC5318933 DOI: 10.1038/srep42923] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 01/16/2017] [Indexed: 12/21/2022] Open
Abstract
Botulinum neurotoxin (BoNT) binds to and internalizes its light chain into presynaptic compartments with exquisite specificity. While the native toxin is extremely lethal, bioengineering of BoNT has the potential to eliminate toxicity without disrupting neuron-specific targeting, thereby creating a molecular vehicle capable of delivering therapeutic cargo into the neuronal cytosol. Building upon previous work, we have developed an atoxic derivative (ad) of BoNT/C1 through rationally designed amino acid substitutions in the metalloprotease domain of wild type (wt) BoNT/C1. To test if BoNT/C1 ad retains neuron-specific targeting without concomitant toxic host responses, we evaluated the localization, activity, and toxicity of BoNT/C1 ad in vitro and in vivo. In neuronal cultures, BoNT/C1 ad light chain is rapidly internalized into presynaptic compartments, but does not cleave SNARE proteins nor impair spontaneous neurotransmitter release. In mice, systemic administration resulted in the specific co-localization of BoNT/C1 ad with diaphragmatic motor nerve terminals. The mouse LD50 of BoNT/C1 ad is 5 mg/kg, with transient neurological symptoms emerging at sub-lethal doses. Given the low toxicity and highly specific neuron-targeting properties of BoNT/C1 ad, these data suggest that BoNT/C1 ad can be useful as a molecular vehicle for drug delivery to the neuronal cytoplasm.
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Affiliation(s)
- Edwin J Vazquez-Cintron
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA.,CytoDel LLC, New York, NY, 10027, USA.,The United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA
| | - Phillip H Beske
- The United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA
| | - Luis Tenezaca
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA.,CytoDel LLC, New York, NY, 10027, USA
| | - Bao Q Tran
- Excet, Inc., 6225 Brandon Ave., Suite 360, Springfield, VA, 22150, USA
| | - Jonathan M Oyler
- The United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA
| | - Elliot J Glotfelty
- The United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA
| | - Christopher A Angeles
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA
| | - Aurelia Syngkon
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA
| | - Jean Mukherjee
- Department of Infectious Diseases and Global Health, Tufts University Clinical and Translational Science Institute, North Grafton, MA, 01536, USA
| | - Suzanne R Kalb
- Centers for Disease Control and Prevention, National Center for Environmental Health/Agency for Toxic Substances and Disease Registry, Atlanta, GA 30341, USA
| | - Philip A Band
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA.,CytoDel LLC, New York, NY, 10027, USA.,Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, New York, NY, 10016, USA
| | - Patrick M McNutt
- The United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA
| | - Charles B Shoemaker
- Department of Infectious Diseases and Global Health, Tufts University Clinical and Translational Science Institute, North Grafton, MA, 01536, USA
| | - Konstantin Ichtchenko
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, 10016, USA
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9
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Entry of Botulinum Neurotoxin Subtypes A1 and A2 into Neurons. Infect Immun 2016; 85:IAI.00795-16. [PMID: 27795365 DOI: 10.1128/iai.00795-16] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 10/05/2016] [Indexed: 11/20/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are the most toxic proteins for humans but also are common therapies for neurological diseases. BoNTs are dichain toxins, comprising an N-terminal catalytic domain (LC) disulfide bond linked to a C-terminal heavy chain (HC) which includes a translocation domain (HN) and a receptor binding domain (HC). Recently, the BoNT serotype A (BoNT/A) subtypes A1 and A2 were reported to possess similar potencies but different rates of cellular intoxication and pathology in a mouse model of botulism. The current study measured HCA1 and HCA2 entry into rat primary neurons and cultured Neuro2A cells. We found that there were two sequential steps during the association of BoNT/A with neurons. The initial step was ganglioside dependent, while the subsequent step involved association with synaptic vesicles. HCA1 and HCA2 entered the same population of synaptic vesicles and entered cells at similar rates. The primary difference was that HCA2 had a higher degree of receptor occupancy for cells and neurons than HcA1. Thus, HCA2 and HCA1 share receptors and entry pathway but differ in their affinity for receptor. The initial interaction of HCA1 and HCA2 with neurons may contribute to the unique pathologies of BoNT/A1 and BoNT/A2 in mouse models.
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10
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McGorum BC, Scholes S, Milne EM, Eaton SL, Wishart TM, Poxton IR, Moss S, Wernery U, Davey T, Harris JB, Pirie RS. Equine grass sickness, but not botulism, causes autonomic and enteric neurodegeneration and increases soluble N-ethylmaleimide-sensitive factor attachment receptor protein expression within neuronal perikarya. Equine Vet J 2016; 48:786-791. [PMID: 26640078 DOI: 10.1111/evj.12543] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 11/24/2015] [Indexed: 11/27/2022]
Abstract
REASONS FOR PERFORMING STUDY Equine grass sickness (EGS) is of unknown aetiology. Despite some evidence suggesting that it represents a toxico-infection with Clostridium botulinum types C and/or D, the effect of EGS on the functional targets of botulinum neurotoxins, namely the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, is unknown. Further, while it is commonly stated that, unlike EGS, equine botulism is not associated with autonomic and enteric neurodegeneration, this has not been definitively assessed. OBJECTIVES To determine: 1) whether botulism causes autonomic and enteric neurodegeneration; and 2) the effect of EGS on the expression of SNARE proteins within cranial cervical ganglion (CCG) and enteric neuronal perikarya. STUDY DESIGN Descriptive study. METHODS Light microscopy was used to compare the morphology of neurons in haematoxylin-eosin stained sections of CCG and ileum from 6 EGS horses, 5 botulism horses and 6 control horses. Immunohistochemistry was used to compare the expression of synaptosomal-associated protein-25, synaptobrevin (Syb) and syntaxin within CCG neurons, and of Syb in enteric neurons, from horses with EGS, horses with botulism and control horses. The concentrations of these SNARE proteins in extracts of CCG from EGS and control horses were compared using quantitative fluorescent western blotting. RESULTS EGS, but not botulism, was associated with autonomic and enteric neurodegeneration and with increased immunoreactivity for SNARE proteins within neuronal perikarya. Quantitative fluorescent western blotting confirmed increased concentrations of synaptosomal-associated protein-25, Syb and syntaxin within CCG extracts from EGS vs. control horses, with the increases in the latter 2 proteins being statistically significant. CONCLUSIONS The occurrence of autonomic and enteric neurodegeneration, and increased expression of SNARE proteins within neuronal perikarya, in EGS but not botulism, suggests that EGS may not be caused by botulinum neurotoxins. Further investigation of the aetiology of EGS is therefore warranted.
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Affiliation(s)
- B C McGorum
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK.
| | - S Scholes
- SAC Consulting Veterinary Services, Penicuik, Midlothian, UK
| | - E M Milne
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK
| | - S L Eaton
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK
| | - T M Wishart
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK.,Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Midlothian, UK
| | - I R Poxton
- Edinburgh Infectious Diseases, University of Edinburgh, Midlothian, UK
| | - S Moss
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK
| | - U Wernery
- Central Veterinary Research Laboratory, Dubai, United Arab Emirates
| | - T Davey
- Electron Microscopy Research Services, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - J B Harris
- Medical Toxicology Centre and Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - R S Pirie
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, University of Edinburgh, Roslin, UK
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11
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Rummel A. Two Feet on the Membrane: Uptake of Clostridial Neurotoxins. Curr Top Microbiol Immunol 2016; 406:1-37. [PMID: 27921176 DOI: 10.1007/82_2016_48] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
The extraordinary potency of botulinum neurotoxins (BoNT) and tetanus neurotoxin (TeNT) is mediated by their high neurospecificity, targeting peripheral cholinergic motoneurons leading to flaccid and spastic paralysis, respectively, and successive respiratory failure. Complex polysialo gangliosides accumulate BoNT and TeNT on the plasma membrane. The ganglioside binding in BoNT/A, B, E, F, G, and TeNT occurs via a conserved ganglioside-binding pocket within the most carboxyl-terminal 25 kDa domain HCC, whereas BoNT/C, DC, and D display here two different ganglioside binding sites. This enrichment step facilitates subsequent binding of BoNT/A, B, DC, D, E, F, and G to the intraluminal domains of the synaptic vesicle glycoprotein 2 (SV2) isoforms A-C and synaptotagmin-I/-II, respectively. Whereas an induced α-helical 20-mer Syt peptide binds via side chain interactions to the tip of the HCC domain of BoNT/B, DC and G, the preexisting, quadrilateral β-sheet helix of SV2C-LD4 binds the clinically most relevant serotype BoNT/A mainly through backbone-backbone interactions at the interface of HCC and HCN. In addition, the conserved, complex N559-glycan branch of SV2C establishes extensive interactions with BoNT/A resulting in delayed dissociation providing BoNT/A more time for endocytosis into synaptic vesicles. An analogous interaction occurs between SV2A/B and BoNT/E. Altogether, the nature of BoNT-SV2 recognition clearly differs from BoNT-Syt. Subsequently, the synaptic vesicle is recycled and the bound neurotoxin is endocytosed. Acidification of the vesicle lumen triggers membrane insertion of the translocation domain, pore formation, and finally translocation of the enzymatically active light chain into the neuronal cytosol to halt release of neurotransmitters.
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Affiliation(s)
- Andreas Rummel
- Institut Für Toxikologie, Medizinische Hochschule Hannover, 30623, Hannover, Germany.
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A Heterologous Reporter Defines the Role of the Tetanus Toxin Interchain Disulfide in Light-Chain Translocation. Infect Immun 2015; 83:2714-24. [PMID: 25895970 DOI: 10.1128/iai.00477-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 04/13/2015] [Indexed: 11/20/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) and tetanus toxin (TeNT) are the most potent toxins for humans and elicit unique pathologies due to their ability to traffic within motor neurons. BoNTs act locally within motor neurons to elicit flaccid paralysis, while retrograde TeNT traffics to inhibitory neurons within the central nervous system (CNS) to elicit spastic paralysis. BoNT and TeNT are dichain proteins linked by an interchain disulfide bond comprised of an N-terminal catalytic light chain (LC) and a C-terminal heavy chain (HC) that encodes an LC translocation domain (HCT) and a receptor-binding domain (HCR). LC translocation is the least understood property of toxin action, but it involves low pH, proteolysis, and an intact interchain disulfide bridge. Recently, Pirazzini et al. (FEBS Lett 587:150-155, 2013, http://dx.doi.org/10.1016/j.febslet.2012.11.007) observed that inhibitors of thioredoxin reductase (TrxR) blocked TeNT and BoNT action in cerebellar granular neurons. In the current study, an atoxic TeNT LC translocation reporter was engineered by fusing β-lactamase to the N terminus of TeNT [βlac-TeNT(RY)] to investigate LC translocation in primary cortical neurons and Neuro-2a cells. βlac-TeNT(RY) retained the interchain disulfide bond, showed ganglioside-dependent binding to neurons, required acidification to promote βlac translocation, and was sensitive to auranofin, an inhibitor of thioredoxin reductase. Mutation of βlac-TeNT(RY) at C439S and C467S eliminated the interchain disulfide bond and inhibited βlac translocation. These data support the requirement of an intact interchain disulfide for LC translocation and imply that disulfide reduction is a prerequisite for LC delivery into the host cytosol. The data also support a model that LC translocation proceeds from the C to the N terminus. βlac-TeNT(RY) is the first reporter system to measure translocation by an AB single-chain toxin in intact cells.
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Entry of a recombinant, full-length, atoxic tetanus neurotoxin into Neuro-2a cells. Infect Immun 2013; 82:873-81. [PMID: 24478100 DOI: 10.1128/iai.01539-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Tetanus neurotoxin (TeNT) and botulinum neurotoxin (BoNT) are clostridial neurotoxins (CNTs) responsible for the paralytic diseases tetanus and botulism, respectively. CNTs are AB toxins with an N-terminal zinc-metalloprotease light chain that is linked by a disulfide bond to a C-terminal heavy chain that includes a translocation domain and a receptor-binding domain (HCR). Current models predict that the HCR defines how CNTs enter and traffic in neurons. Recent studies implicate that domains outside the HCR contribute to CNT trafficking in neurons. In the current study, a recombinant, full-length TeNT derivative, TeNT(RY), was engineered to analyze TeNT cell entry. TeNT(RY) was atoxic in a mouse challenge model. Using Neuro-2a cells, a mouse neuroblastoma cell line, TeNT HCR (HCR/T) and TeNT(RY) were found to bind gangliosides with similar affinities and specificities, consistent with the HCR domain containing receptor binding function. Temporal studies showed that HCR/T and TeNT(RY) entered Neuro-2a cells slower than the HCR of BoNT/A (HCR/A), transferrin, and cholera toxin B. Intracellular localization showed that neither HCR/T nor TeNT(RY) localized with HCR/A or synaptic vesicle protein 2, the protein receptor for HCR/A. HCR/T and TeNT(RY) exhibited only partial intracellular colocalization, indicating that regions outside the HCR contribute to the intracellular TeNT trafficking. TeNT may require this complex functional entry organization to target neurons in the central nervous system.
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Karalewitz APA, Fu Z, Baldwin MR, Kim JJP, Barbieri JT. Botulinum neurotoxin serotype C associates with dual ganglioside receptors to facilitate cell entry. J Biol Chem 2012; 287:40806-16. [PMID: 23027864 PMCID: PMC3504792 DOI: 10.1074/jbc.m112.404244] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND How botulinum neurotoxin serotype C (BoNT/C) enters neurons is unclear. RESULTS BoNT/C utilizes dual gangliosides as host cell receptors. CONCLUSION BoNT/C accesses gangliosides on the plasma membrane. SIGNIFICANCE Plasma membrane accessibility of the dual ganglioside receptors suggests synaptic vesicle exocytosis may not be necessary to expose BoNT/C receptors. Botulinum neurotoxins (BoNTs) cleave SNARE proteins in motor neurons that inhibits synaptic vesicle (SV) exocytosis, resulting in flaccid paralysis. There are seven BoNT serotypes (A-G). In current models, BoNTs initially bind gangliosides on resting neurons and upon SV exocytosis associate with the luminal domains of SV-associated proteins as a second receptor. The entry of BoNT/C is less clear. Characterizing the heavy chain receptor binding domain (HCR), BoNT/C was shown to utilize gangliosides as dual host receptors. Crystallographic and biochemical studies showed that the two ganglioside binding sites, termed GBP2 and Sia-1, were independent and utilized unique mechanisms to bind complex gangliosides. The GBP2 binding site recognized gangliosides that contained a sia5 sialic acid, whereas the Sia-1 binding site recognized gangliosides that contained a sia7 sialic acid and sugars within the backbone of the ganglioside. Utilizing gangliosides that uniquely recognized the GBP2 and Sia-1 binding sites, HCR/C entry into Neuro-2A cells required both functional ganglioside binding sites. HCR/C entered cells differently than the HCR of tetanus toxin, which also utilizes dual gangliosides as host receptors. A point-mutated HCR/C that lacked GBP2 binding potential retained the ability to bind and enter Neuro-2A cells. This showed that ganglioside binding at the Sia-1 site was accessible on the plasma membrane, suggesting that SV exocytosis may not be required to expose BoNT/C receptors. These studies highlight the utility of BoNT HCRs as probes to study the role of gangliosides in neurotransmission.
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Affiliation(s)
| | - Zhuji Fu
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Michael R. Baldwin
- the Department of Microbiology and Molecular Genetics, University of Missouri, Columbia, Missouri 65212
| | - Jung-Ja P. Kim
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Joseph T. Barbieri
- From the Departments of Microbiology and Molecular Genetics and , To whom correspondence should be addressed: Dept. of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226. Tel.: 414-955-8412; Fax: 414-955-6535; E-mail:
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Peng L, Berntsson RPA, Tepp WH, Pitkin RM, Johnson EA, Stenmark P, Dong M. Botulinum neurotoxin D-C uses synaptotagmin I and II as receptors, and human synaptotagmin II is not an effective receptor for type B, D-C and G toxins. J Cell Sci 2012; 125:3233-42. [PMID: 22454523 DOI: 10.1242/jcs.103564] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are classified into seven types (A-G), but multiple subtype and mosaic toxins exist. These subtype and mosaic toxins share a high sequence identity, and presumably the same receptors and substrates with their parental toxins. Here, we report that a mosaic toxin, type D-C (BoNT/D-C), uses different receptors from its parental toxin BoNT/C. BoNT/D-C, but not BoNT/C, binds directly to the luminal domains of synaptic vesicle proteins synaptotagmin (Syt) I and II, and requires expression of SytI/II to enter neurons. The SytII luminal fragment containing the toxin-binding site can block the entry of BoNT/D-C into neurons and reduce its toxicity in vivo in mice. We also found that gangliosides increase binding of BoNT/D-C to SytI/II and enhance the ability of the SytII luminal fragment to block BoNT/D-C entry into neurons. These data establish SytI/II, in conjunction with gangliosides, as the receptors for BoNT/D-C, and indicate that BoNT/D-C is functionally distinct from BoNT/C. We further found that BoNT/D-C recognizes the same binding site on SytI/II where BoNT/B and G also bind, but utilizes a receptor-binding interface that is distinct from BoNT/B and G. Finally, we also report that human and chimpanzee SytII has diminished binding and function as the receptor for BoNT/B, D-C and G owing to a single residue change from rodent SytII within the toxin binding site, potentially reducing the potency of these BoNTs in humans and chimpanzees.
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Affiliation(s)
- Lisheng Peng
- Department of Microbiology and Immunobiology, Harvard Medical School and Division of Neuroscience, New England Primate Research Center, Southborough, MA 01772, USA
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Couesnon A, Molgó J, Connan C, Popoff MR. Preferential entry of botulinum neurotoxin A Hc domain through intestinal crypt cells and targeting to cholinergic neurons of the mouse intestine. PLoS Pathog 2012; 8:e1002583. [PMID: 22438808 PMCID: PMC3305446 DOI: 10.1371/journal.ppat.1002583] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 01/27/2012] [Indexed: 12/12/2022] Open
Abstract
Botulism, characterized by flaccid paralysis, commonly results from botulinum neurotoxin (BoNT) absorption across the epithelial barrier from the digestive tract and then dissemination through the blood circulation to target autonomic and motor nerve terminals. The trafficking pathway of BoNT/A passage through the intestinal barrier is not yet fully understood. We report that intralumenal administration of purified BoNT/A into mouse ileum segment impaired spontaneous muscle contractions and abolished the smooth muscle contractions evoked by electric field stimulation. Entry of BoNT/A into the mouse upper small intestine was monitored with fluorescent HcA (half C-terminal domain of heavy chain) which interacts with cell surface receptor(s). We show that HcA preferentially recognizes a subset of neuroendocrine intestinal crypt cells, which probably represent the entry site of the toxin through the intestinal barrier, then targets specific neurons in the submucosa and later (90–120 min) in the musculosa. HcA mainly binds to certain cholinergic neurons of both submucosal and myenteric plexuses, but also recognizes, although to a lower extent, other neuronal cells including glutamatergic and serotoninergic neurons in the submucosa. Intestinal cholinergic neuron targeting by HcA could account for the inhibition of intestinal peristaltism and secretion observed in botulism, but the consequences of the targeting to non-cholinergic neurons remains to be determined. Botulism is a severe and often fatal disease in man and animals characterized by flaccid paralysis. Clostridium botulinum produces a potent neurotoxin (botulinum neurotoxin) responsible for all the symptoms of botulism. Botulism is most often acquired by ingesting preformed botulinum neurotoxin in contaminated food or after intestinal colonization by C. botulinum under certain circumstances, such as in infant botulism, and toxin production in the intestine. The first step of the disease consists in the passage of the botulinum neurotoxin through the intestinal barrier, which is still poorly understood. We investigated the trafficking of the botulinum neurotoxin in a mouse intestinal loop model, using fluorescent HcA (half C-terminal domain of the heavy chain). We observed that HcA preferentially recognizes neuroendocrine intestinal crypt cells, which likely represent the entry site of the toxin through the intestinal barrier, then targets specific neurons, mainly cholinergic neurons, in the submucosa, and later (90–120 min) in the musculosa leading to local paralytic effects such as inhibition of intestinal peristaltism. These results represent an important advance in the understanding of the initial steps of botulism intoxication and can be the basis for the development of new specific countermeasures against botulism.
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Affiliation(s)
- Aurélie Couesnon
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
| | - Jordi Molgó
- CNRS, Institut de Neurobiologie Alfred Fessard – FRC2118, Laboratoire de Neurobiologie– et Développement UPR3294, Gif sur Yvette, France
| | - Chloé Connan
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
| | - Michel R. Popoff
- Institut Pasteur, Unité des Bactéries anaérobies et Toxines, Paris, France
- * E-mail:
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Tetanus toxin and botulinum toxin a utilize unique mechanisms to enter neurons of the central nervous system. Infect Immun 2012; 80:1662-9. [PMID: 22392932 DOI: 10.1128/iai.00057-12] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) and tetanus neurotoxin (TeNT) are the most toxic proteins for humans. While BoNTs cause flaccid paralysis, TeNT causes spastic paralysis. Characterized BoNT serotypes enter neurons upon binding dual receptors, a ganglioside and a neuron-specific protein, either synaptic vesicle protein 2 (SV2) or synaptotagmin, while TeNT enters upon binding gangliosides as dual receptors. Recently, TeNT was reported to enter central nervous system (CNS) neurons upon synaptic vesicle cycling that was mediated by the direct binding to SV2, implying that TeNT and BoNT utilize common mechanisms to enter CNS neurons. This prompted an assessment of TeNT entry into CNS neurons, using the prototypic BoNT serotype A as a reference for SV2-mediated entry into synaptic vesicles, analyzing the heavy-chain receptor binding domain (HCR) of each toxin. Synaptic vesicle cycling stimulated the entry of HCR/A into neurons, while HCR/T entered neurons with similar levels of efficiency in depolarized and nondepolarized neurons. ImageJ analysis identified two populations of cell-associated HCR/T in synaptic vesicle cycling neurons, a major population which segregated from HCR/A and a minor population which colocalized with HCR/A. HCR/T did not inhibit HCR/A entry into neurons in competition experiments and did not bind SV2, the protein receptor for BoNT/A. Intoxication experiments showed that TeNT efficiently cleaved VAMP2 in depolarized neurons and neurons blocked for synaptic vesicle cycling. These experiments demonstrate that TeNT enters neurons by two pathways, one independent of stimulated synaptic vesicle cycling and one by synaptic vesicles independent of SV2, showing that TeNT and BoNT/A enter neurons by unique mechanisms.
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Neurotransmitter vesicle release from human model neurons (NT2) is sensitive to botulinum toxin A. Cell Mol Neurobiol 2012; 32:1021-9. [PMID: 22373696 DOI: 10.1007/s10571-012-9818-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/14/2012] [Indexed: 01/06/2023]
Abstract
Botulinum neurotoxins (BoNTs) internalize into nerve terminals and block the release of neurotransmitters into the synapse. BoNTs are widely used as a therapeutic agent for treatment of movement disorders and recently gained more attention as a biological weapon. Consequently, there is strong interest to develop a cell-based assay platform to screen the toxicity and bioactivity of the BoNTs. In this study, we present an in vitro screening assay for BoNT/A based on differentiated human embryonal carcinoma stem (NT2) cells. The human NT2 cells fully differentiated into mature neurons that display immunoreactivity to cytoskeletal markers (βIII-tubulin and MAP2) and presynaptic proteins (synapsin and synaptotagmin I). We showed that the human NT2 cells undergo a process of exo-endocytotic synaptic vesicle recycling upon depolarization with high K(+) buffer. By employing an antibody directed against light chain of BoNT/A, we detected internalized toxin as a punctate staining along the neurites of the NT2 neurons. Using well-established methods of synaptic vesicle exocytosis assay (luminal synaptotagmin I and FM1-43 imaging) we show that pre-incubation with BoNT/A resulted in a blockade of vesicle release from human NT2 neurons in a dose-dependent manner. Moreover, this blocking effect of BoNT/A was abolished by pre-adsorbing the toxin with neutralizing antibody. In a proof of principle, we demonstrate that our cell culture assay for vesicle release is sensitive to BoNT/A and the activity of BoNT/A can be blocked by specific neutralizing antibodies. Overall our data suggest that human NT2 neurons are suitable for large scale screening of botulinum bioactivity.
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Kroken AR, Karalewitz APA, Fu Z, Kim JJP, Barbieri JT. Novel ganglioside-mediated entry of botulinum neurotoxin serotype D into neurons. J Biol Chem 2011; 286:26828-37. [PMID: 21632541 PMCID: PMC3143643 DOI: 10.1074/jbc.m111.254086] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 05/17/2011] [Indexed: 11/06/2022] Open
Abstract
Botulinum Neurotoxins (BoNTs) are organized into seven serotypes, A-G. Although several BoNT serotypes enter neurons through synaptic vesicle cycling utilizing dual receptors (a ganglioside and a synaptic vesicle-associated protein), the entry pathway of BoNT/D is less well understood. Although BoNT/D entry is ganglioside-dependent, alignment and structural studies show that BoNT/D lacks key residues within a conserved ganglioside binding pocket that are present in BoNT serotypes A, B, E, F, and G, which indicate that BoNT/D-ganglioside interactions may be unique. In this study BoNT/D is shown to have a unique association with ganglioside relative to the other BoNT serotypes, utilizing a ganglioside binding loop (GBL, residues Tyr-1235-Ala-1245) within the receptor binding domain of BoNT/D (HCR/D) via b-series gangliosides, including GT1b, GD1b, and GD2. HCR/D bound gangliosides and entered neurons dependent upon the aromatic ring of Phe-1240 within the GBL. This is the first BoNT-ganglioside interaction that is mediated by a phenylalanine. In contrast, Trp-1238, located near the N terminus of the ganglioside binding loop, was mostly solvent-inaccessible and appeared to contribute to maintaining the loop structure. BoNT/D entry and intoxication were enhanced by membrane depolarization via synaptic vesicle cycling, where HCR/D colocalized with synaptophysin, a synaptic vesicle marker, but immunoprecipitation experiments did not detect direct association with synaptic vesicle protein 2. Thus, BoNT/D utilizes unique associations with gangliosides and synaptic vesicles to enter neurons, which may facilitate new neurotoxin therapies.
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Affiliation(s)
- Abby R. Kroken
- From the Departments of Microbiology and Molecular Genetics and
| | | | - Zhuji Fu
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jung-Ja P. Kim
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Kroken AR, Karalewitz APA, Fu Z, Baldwin MR, Kim JJP, Barbieri JT. Unique ganglioside binding by botulinum neurotoxins C and D-SA. FEBS J 2011; 278:4486-96. [PMID: 21554541 DOI: 10.1111/j.1742-4658.2011.08166.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The botulinum neurotoxins (BoNTs) are the most potent protein toxins for humans. There are seven serotypes of BoNTs (A-G), based on a lack of cross-antiserum neutralization. The BoNT/C and BoNT/D serotypes include mosaic toxins that are organized as D-C and C-D toxins. One BoNT D-C mosaic toxin, BoNT/D-South Africa (BoNT/D-SA), was not fully neutralized by immunization with a vaccine composed of either prototype BoNT/C-Stockholm or BoNT/D-1873. Whereas several BoNT serotypes utilize dual receptors (gangliosides and proteins) to bind to and enter neurons, the basis for BoNT/C and BoNT/D entry into neurons is less well understood. Recent studies solved the crystal structures of the receptor-binding domains of BoNT/C, BoNT/D, and BoNT/D-SA. Comparative structural analysis showed that BoNT/C, BoNT/D and BoNT/D-SA lacked components of the ganglioside-binding pocket that exists within other BoNT serotypes. With the use of structure-based alignments, biochemical analyses, and cell-binding approaches, BoNT/C and BoNT/D-SA have been shown to possess a unique ganglioside-binding domain, the ganglioside-binding loop. Defining how BoNTs enter host cells provides insights towards understanding the evolution and extending the potential therapeutic and immunological values of the BoNT serotypes.
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Affiliation(s)
- Abby R Kroken
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Peng L, Tepp WH, Johnson EA, Dong M. Botulinum neurotoxin D uses synaptic vesicle protein SV2 and gangliosides as receptors. PLoS Pathog 2011; 7:e1002008. [PMID: 21483489 PMCID: PMC3068998 DOI: 10.1371/journal.ppat.1002008] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 01/10/2011] [Indexed: 02/03/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) include seven bacterial toxins (BoNT/A-G) that target presynaptic terminals and act as proteases cleaving proteins required for synaptic vesicle exocytosis. Here we identified synaptic vesicle protein SV2 as the protein receptor for BoNT/D. BoNT/D enters cultured hippocampal neurons via synaptic vesicle recycling and can bind SV2 in brain detergent extracts. BoNT/D failed to bind and enter neurons lacking SV2, which can be rescued by expressing one of the three SV2 isoforms (SV2A/B/C). Localization of SV2 on plasma membranes mediated BoNT/D binding in both neurons and HEK293 cells. Furthermore, chimeric receptors containing the binding sites for BoNT/A and E, two other BoNTs that use SV2 as receptors, failed to mediate the entry of BoNT/D suggesting that BoNT/D binds SV2 via a mechanism distinct from BoNT/A and E. Finally, we demonstrated that gangliosides are essential for the binding and entry of BoNT/D into neurons and for its toxicity in vivo, supporting a double-receptor model for this toxin. BoNTs are a family of seven bacterial toxins (BoNT/A-G). Among the seven BoNTs, whether BoNT/D uses the same entry pathways and similar receptor-binding strategies as other BoNTs is not known. Previous studies have suggested that BoNT/D does not need a protein receptor nor ganglioside co-receptor, in contrast to all other BoNTs. Here we demonstrate that BoNT/D uses synaptic vesicle protein SV2 as its protein receptor and gangliosides as co-receptor, thus supporting the “double-receptor” model as a central theme for this class of toxins. Furthermore, we found that BoNT/D utilizes a SV2 binding mechanism distinct from BoNT/A and BoNT/E, two other BoNTs that use SV2 as receptors. This indicates that different BoNTs can develop their distinct mechanisms to target a common receptor protein.
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Affiliation(s)
- Lisheng Peng
- Department of Microbiology and Molecular Genetics, Harvard Medical School and Division of Neuroscience, New England Primate Research Center, Southborough, Massachusetts, United States of America
| | - William H. Tepp
- Department of Food Microbiology and Toxicology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Eric A. Johnson
- Department of Food Microbiology and Toxicology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Min Dong
- Department of Microbiology and Molecular Genetics, Harvard Medical School and Division of Neuroscience, New England Primate Research Center, Southborough, Massachusetts, United States of America
- * E-mail:
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Chen S, Barbieri JT. Association of botulinum neurotoxin serotype A light chain with plasma membrane-bound SNAP-25. J Biol Chem 2011; 286:15067-72. [PMID: 21378164 DOI: 10.1074/jbc.m111.224493] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Clostridium botulinum neurotoxins (BoNTs) cleave SNARE proteins, which inhibit binding and thus fusion of neurotransmitter vesicles to the plasma membrane of peripheral neurons. BoNTs comprise an N-terminal light chain (LC) and C-terminal heavy chain, which are linked by a disulfide bond. There are seven serotypes (A-G) of BoNTs based upon immunological neutralization. Although the binding and entry of BoNT/A into neurons has been subjected to considerable investigation, the intracellular events that allow BoNT/A to efficiently cleave SNAP-25 within neurons is less well understood. Earlier studies showed that intracellular LC/A bound to the plasma membrane of neurons. In this study, intracellular LC/A is shown to directly bind SNAP-25 on the plasma membrane. Solid phase binding showed that the N-terminal residues of LC/A bound residues 80-110 of SNAP-25, which was also observed in cultured neurons. Association of the N-terminal 8 amino acids of LC/A and residues 80-110 of SNAP-25 also enhanced substrate cleavage. These findings explain how LC/A associates with SNAP-25 on the plasma membrane and provide a basis for LC/A cleavage of SNAP-25 within the SNARE complex.
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Affiliation(s)
- Sheng Chen
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom Kowloon, Hong Kong
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Pier CL, Chen C, Tepp WH, Lin G, Janda KD, Barbieri JT, Pellett S, Johnson EA. Botulinum neurotoxin subtype A2 enters neuronal cells faster than subtype A1. FEBS Lett 2010; 585:199-206. [PMID: 21126520 DOI: 10.1016/j.febslet.2010.11.045] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 11/23/2010] [Accepted: 11/25/2010] [Indexed: 10/18/2022]
Abstract
Botulinum neurotoxins (BoNTs), the causative agent of human botulism, are the most potent naturally occurring toxins known. BoNT/A1, the most studied BoNT, is also used as an important biopharmaceutical. In this study, the biological activity of BoNT/A1 is compared to that of BoNT/A2 using neuronal cell models. The data obtained indicate faster and increased intoxication of neuronal cells by BoNT/A2 than BoNT/A1, and that the mechanism underlying this increased toxicity is faster and more efficient cell entry that is independent of ganglioside binding. These results have important implications for the development of new BoNT based therapeutics and BoNT countermeasures.
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Affiliation(s)
- Christina L Pier
- Department of Bacteriology, University of Wisconsin, Madison, Madison, WI 53706, USA
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Yeh FL, Dong M, Yao J, Tepp WH, Lin G, Johnson EA, Chapman ER. SV2 mediates entry of tetanus neurotoxin into central neurons. PLoS Pathog 2010; 6:e1001207. [PMID: 21124874 PMCID: PMC2991259 DOI: 10.1371/journal.ppat.1001207] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 10/22/2010] [Indexed: 01/18/2023] Open
Abstract
Tetanus neurotoxin causes the disease tetanus, which is characterized by rigid paralysis. The toxin acts by inhibiting the release of neurotransmitters from inhibitory neurons in the spinal cord that innervate motor neurons and is unique among the clostridial neurotoxins due to its ability to shuttle from the periphery to the central nervous system. Tetanus neurotoxin is thought to interact with a high affinity receptor complex that is composed of lipid and protein components; however, the identity of the protein receptor remains elusive. In the current study, we demonstrate that toxin binding, to dissociated hippocampal and spinal cord neurons, is greatly enhanced by driving synaptic vesicle exocytosis. Moreover, tetanus neurotoxin entry and subsequent cleavage of synaptobrevin II, the substrate for this toxin, was also dependent on synaptic vesicle recycling. Next, we identified the potential synaptic vesicle binding protein for the toxin and found that it corresponded to SV2; tetanus neurotoxin was unable to cleave synaptobrevin II in SV2 knockout neurons. Toxin entry into knockout neurons was rescued by infecting with viruses that express SV2A or SV2B. Tetanus toxin elicited the hyper excitability in dissociated spinal cord neurons - due to preferential loss of inhibitory transmission - that is characteristic of the disease. Surprisingly, in dissociated cortical cultures, low concentrations of the toxin preferentially acted on excitatory neurons. Further examination of the distribution of SV2A and SV2B in both spinal cord and cortical neurons revealed that SV2B is to a large extent localized to excitatory terminals, while SV2A is localized to inhibitory terminals. Therefore, the distinct effects of tetanus toxin on cortical and spinal cord neurons are not due to differential expression of SV2 isoforms. In summary, the findings reported here indicate that SV2A and SV2B mediate binding and entry of tetanus neurotoxin into central neurons. Tetanus neurotoxin is one of the most deadly bacterial toxins known and is the causative agent for the disease tetanus, also known as lockjaw. Tetanus neurotoxin utilizes motor neurons as a means of transport in order to enter the spinal cord. Once in the spinal cord, the toxin leaves motor neurons and enters inhibitory neurons through a “Trojan-horse” strategy, thereby preventing the release of inhibitory neurotransmitters onto motor neurons. This causes hyper-excitability of the motor neuron and excessive release of acetylcholine at the neuromuscular junction, resulting in rigid paralysis. There is a major gap in our understanding of the mechanism by which tetanus neurotoxin enters neurons. In the current study we discovered that the “Trojan-horse”, utilized by tetanus neurotoxin to enter central neurons, corresponds to recycling synaptic vesicles. Furthermore, we discovered that SV2 is critical for the binding and entry of tetanus neurotoxin into these neurons. These findings will enable further development of drugs that antagonize the action of the toxin and will also aid in the development of drug delivery systems that target spinal cord neurons.
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Affiliation(s)
- Felix L. Yeh
- Department of Physiology, Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Min Dong
- New England Primate Research Center, Department of Microbiology and Molecular Genetics, Harvard Medical School, Southborough, Massachusetts, United States of America
| | - Jun Yao
- Department of Physiology, Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
| | - William H. Tepp
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Guangyun Lin
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Edwin R. Chapman
- Department of Physiology, Howard Hughes Medical Institute, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
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Light chain separated from the rest of the type a botulinum neurotoxin molecule is the most catalytically active form. PLoS One 2010; 5:e12872. [PMID: 20877571 PMCID: PMC2943925 DOI: 10.1371/journal.pone.0012872] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 08/20/2010] [Indexed: 11/19/2022] Open
Abstract
Botulinum neurotoxins (BoNT) are the most potent of all toxins. The 50 kDa N-terminal endopeptidase catalytic light chain (LC) of BoNT is located next to its central, putative translocation domain. After binding to the peripheral neurons, the central domain of BoNT helps the LC translocate into cytosol where its proteolytic action on SNARE (soluble NSF attachment protein receptor) proteins blocks exocytosis of acetyl choline leading to muscle paralysis and eventual death. The translocation domain also contains 105 Å -long stretch of ∼100 residues, known as “belt,” that crosses over and wraps around the LC to shield the active site from solvent. It is not known if the LC gets dissociated from the rest of the molecule in the cytosol before catalysis. To investigate the structural identity of the protease, we prepared four variants of type A BoNT (BoNT/A) LC, and compared their catalytic parameters with those of BoNT/A whole toxin. The four variants were LC + translocation domain, a trypsin-nicked LC + translocation domain, LC + belt, and a free LC. Our results showed that Km for a 17-residue SNAP-25 (synaptosomal associated protein of 25 kDa) peptide for these constructs was not very different, but the turnover number (kcat) for the free LC was 6-100-fold higher than those of its four variants. Moreover, none of the four variants of the LC was prone to autocatalysis. Our results clearly demonstrated that in vitro, the LC minus the rest of the molecule is the most catalytically active form. The results may have implication as to the identity of the active, toxic moiety of BoNT/A in vivo.
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Karalewitz APA, Kroken AR, Fu Z, Baldwin MR, Kim JJP, Barbieri JT. Identification of a unique ganglioside binding loop within botulinum neurotoxins C and D-SA . Biochemistry 2010; 49:8117-26. [PMID: 20731382 PMCID: PMC2939319 DOI: 10.1021/bi100865f] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The botulinum neurotoxins (BoNTs) are the most potent protein toxins for humans. There are seven serotypes of BoNTs (A-G) based on a lack of cross antiserum neutralization. BoNTs utilize gangliosides as components of the host receptors for binding and entry into neurons. Members of BoNT/C and BoNT/D serotypes include mosaic toxins that are organized in D/C and C/D toxins. One D/C mosaic toxin, BoNT/D-South Africa (BoNT/D-SA), was not fully neutralized by immunization with BoNT serotype C or D, which stimulated this study. Here the crystal structures of the receptor binding domains of BoNT/C, BoNT/D, and BoNT/D-SA are presented. Biochemical and cell binding studies show that BoNT/C and BoNT/D-SA possess unique mechanisms for ganglioside binding. These studies provide new information about how the BoNTs can enter host cells as well as a basis for understanding the immunological diversity of these neurotoxins.
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Affiliation(s)
- Andrew P-A. Karalewitz
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Abby R. Kroken
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Zhuji Fu
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michael R. Baldwin
- Department of Microbiology and Immunology at the University of Missouri, Columbia, Missouri
| | - Jung-Ja P. Kim
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Joseph T. Barbieri
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin
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Low pH-induced pore formation by the T domain of botulinum toxin type A is dependent upon NaCl concentration. J Membr Biol 2010; 236:191-201. [PMID: 20711775 DOI: 10.1007/s00232-010-9292-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 07/19/2010] [Indexed: 10/19/2022]
Abstract
Botulinum neurotoxins (BoNTs) undergo low pH-triggered membrane insertion, resulting in the translocation of their light (catalytic) chains into the cytoplasm. The T (translocation) domain of the BoNT heavy chain is believed to carry out translocation. Here, the behavior of isolated T domain from BoNT type A has been characterized, both in solution and when associated with model membranes. When BoNT T domain prepared in the detergent dodecylmaltoside was diluted into aqueous solution, it exhibited a low pH-dependent conformational change below pH 6. At low pH the T domain associated with, and formed pores within, model membrane vesicles composed of 30 mol% dioleoylphosphatidylglycerol/70 mol% dioleoylphosphatidylcholine. Although T domain interacted with vesicles at low (50 mM) and high (400 mM) NaCl concentrations, the interaction required much less lipid at low salt. However, even at high lipid concentrations pore formation was much more pronounced at low NaCl concentrations than at high NaCl concentration. Increasing salt concentration after insertion in the presence of 50 mM NaCl did not decrease pore formation. A similar effect of NaCl concentration upon pore formation was observed in vesicles composed solely of dioleoylphosphatidylcholine, showing that the effect of NaCl did not solely involve modulation of electrostatic interactions between protein and anionic lipids. These results indicate that some feature of membrane-bound T domain tertiary structure critical for pore formation is highly dependent upon salt concentration.
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Waggett B, McGorum B, Shaw D, Pirie R, MacIntyre N, Wernery U, Milne E. Evaluation of Synaptophysin as an Immunohistochemical Marker for Equine Grass Sickness. J Comp Pathol 2010; 142:284-90. [DOI: 10.1016/j.jcpa.2009.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 09/02/2009] [Accepted: 11/07/2009] [Indexed: 10/20/2022]
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Stenmark P, Dong M, Dupuy J, Chapman ER, Stevens RC. Crystal structure of the botulinum neurotoxin type G binding domain: insight into cell surface binding. J Mol Biol 2010; 397:1287-97. [PMID: 20219474 DOI: 10.1016/j.jmb.2010.02.041] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 02/22/2010] [Accepted: 02/23/2010] [Indexed: 10/19/2022]
Abstract
Botulinum neurotoxins (BoNTs) typically bind the neuronal cell surface via dual interactions with both protein receptors and gangliosides. We present here the 1.9-A X-ray structure of the BoNT serotype G (BoNT/G) receptor binding domain (residues 868-1297) and a detailed view of protein receptor and ganglioside binding regions. The ganglioside binding motif (SxWY) has a conserved structure compared to the corresponding regions in BoNT serotype A and BoNT serotype B (BoNT/B), but several features of interactions with the hydrophilic face of the ganglioside are absent at the opposite side of the motif in the BoNT/G ganglioside binding cleft. This may significantly reduce the affinity between BoNT/G and gangliosides. BoNT/G and BoNT/B share the protein receptor synaptotagmin (Syt) I/II. The Syt binding site has a conserved hydrophobic plateau located centrally in the proposed protein receptor binding interface (Tyr1189, Phe1202, Ala1204, Pro1205, and Phe1212). Interestingly, only 5 of 14 residues that are important for binding between Syt-II and BoNT/B are conserved in BoNT/G, suggesting that the means by which BoNT/G and BoNT/B bind Syt diverges more than previously appreciated. Indeed, substitution of Syt-II Phe47 and Phe55 with alanine residues had little effect on the binding of BoNT/G, but strongly reduced the binding of BoNT/B. Furthermore, an extended solvent-exposed hydrophobic loop, located between the Syt binding site and the ganglioside binding cleft, may serve as a third membrane association and binding element to contribute to high-affinity binding to the neuronal membrane. While BoNT/G and BoNT/B are homologous to each other and both utilize Syt-I/Syt-II as their protein receptor, the precise means by which these two toxin serotypes bind to Syt appears surprisingly divergent.
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Affiliation(s)
- Pål Stenmark
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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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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31
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Montecucco C, Rossetto O, Caccin P, Rigoni M, Carli L, Morbiato L, Muraro L, Paoli M. Different mechanisms of inhibition of nerve terminals by botulinum and snake presynaptic neurotoxins. Toxicon 2009; 54:561-4. [DOI: 10.1016/j.toxicon.2008.12.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 12/09/2008] [Indexed: 01/26/2023]
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32
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Caleo M, Schiavo G. Central effects of tetanus and botulinum neurotoxins. Toxicon 2009; 54:593-9. [DOI: 10.1016/j.toxicon.2008.12.026] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 12/04/2008] [Accepted: 12/08/2008] [Indexed: 01/26/2023]
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Fu Z, Chen C, Barbieri JT, Kim JJP, Baldwin MR. Glycosylated SV2 and gangliosides as dual receptors for botulinum neurotoxin serotype F. Biochemistry 2009; 48:5631-41. [PMID: 19476346 DOI: 10.1021/bi9002138] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxin causes rapid flaccid paralysis through the inhibition of acetylcholine release at the neuromuscular junction. The seven BoNT serotypes (A-G) have been proposed to bind motor neurons via ganglioside-protein dual receptors. To date, the structure-function properties of BoNT/F host receptor interactions have not been resolved. Here, we report the crystal structures of the receptor binding domains (HCR) of BoNT/A and BoNT/F and the characterization of the dual receptors for BoNT/F. The overall polypeptide fold of HCR/A is essentially identical to the receptor binding domain of the BoNT/A holotoxin, and the structure of HCR/F is very similar to that of HCR/A, except for two regions implicated in neuronal binding. Solid phase array analysis identified two HCR/F binding glycans: ganglioside GD1a and oligosaccharides containing an N-acetyllactosamine core. Using affinity chromatography, HCR/F bound native synaptic vesicle glycoproteins as part of a protein complex. Deglycosylation of glycoproteins using alpha(1-3,4)-fucosidase, endo-beta-galactosidase, and PNGase F disrupted the interaction with HCR/F, while the binding of HCR/B to its cognate receptor, synaptotagmin I, was unaffected. These data indicate that the HCR/F binds synaptic vesicle glycoproteins through the keratan sulfate moiety of SV2. The interaction of HCR/F with gangliosides was also investigated. HCR/F bound specifically to gangliosides that contain alpha2,3-linked sialic acid on the terminal galactose of a neutral saccharide core (binding order GT1b = GD1a >> GM3; no binding to GD1b and GM1a). Mutations within the putative ganglioside binding pocket of HCR/F decreased binding to gangliosides, synaptic vesicle protein complexes, and primary rat hippocampal neurons. Thus, BoNT/F neuronal discrimination involves the recognition of ganglioside and protein (glycosylated SV2) carbohydrate moieties, providing a structural basis for the high affinity and specificity of BoNT/F for neurons.
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Affiliation(s)
- Zhuji Fu
- Department of Biochemistry, Medical Collegeof Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA
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Rummel A, Häfner K, Mahrhold S, Darashchonak N, Holt M, Jahn R, Beermann S, Karnath T, Bigalke H, Binz T. Botulinum neurotoxins C, E and F bind gangliosides via a conserved binding site prior to stimulation-dependent uptake with botulinum neurotoxin F utilising the three isoforms of SV2 as second receptor. J Neurochem 2009; 110:1942-54. [PMID: 19650874 DOI: 10.1111/j.1471-4159.2009.06298.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The high toxicity of clostridial neurotoxins primarily results from their specific binding and uptake into neurons. At motor neurons, the seven botulinum neurotoxin serotypes A-G (BoNT/A-G) inhibit acetylcholine release, leading to flaccid paralysis, while tetanus neurotoxin blocks neurotransmitter release in inhibitory neurons, resulting in spastic paralysis. Uptake of BoNT/A, B, E and G requires a dual interaction with gangliosides and the synaptic vesicle (SV) proteins synaptotagmin or SV2, whereas little is known about the entry mechanisms of the remaining serotypes. Here, we demonstrate that BoNT/F as wells depends on the presence of gangliosides, by employing phrenic nerve hemidiaphragm preparations derived from mice expressing GM3, GM2, GM1 and GD1a or only GM3. Subsequent site-directed mutagenesis based on homology models identified the ganglioside binding site at a conserved location in BoNT/E and F. Using the mice phrenic nerve hemidiaphragm assay as a physiological model system, cross-competition of full-length neurotoxin binding by recombinant binding fragments, plus accelerated neurotoxin uptake upon increased electrical stimulation, indicate that BoNT/F employs SV2 as protein receptor, whereas BoNT/C and D utilise different SV receptor structures. The co-precipitation of SV2A, B and C from Triton-solubilised SVs by BoNT/F underlines this conclusion.
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Affiliation(s)
- Andreas Rummel
- Institut für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany.
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Abstract
Tetanus neurotoxin and botulinum neurotoxins are the causative agents of tetanus and botulism. They block the release of neurotransmitters from synaptic vesicles in susceptible animals and man and act in nanogram quantities because of their ability to specifically attack motoneurons. They developed an ingenious strategy to enter neurons. This involves a concentration step via complex polysialo gangliosides at the plasma membrane and the uptake and ride in recycling synaptic vesicles initiated by binding to a specific protein receptor. Finally, the neurotoxins shut down the synaptic vesicle cycle, which they had misused before to enter their target cells, via specific cleavage of protein core components of the cellular membrane fusion machinery. The uptake of four out of seven known botulinum neurotoxins into synaptic vesicles has been demonstrated to rely on binding to intravesicular segments of the synaptic vesicle proteins synaptotagmin or synaptic vesicle protein 2. This review summarizes the present knowledge about the cell receptor molecules and the mode of toxin-receptor interaction that enables the toxins' sophisticated access to their site of action.
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Affiliation(s)
- Thomas Binz
- Institut für Biochemie, Medizinische Hochschule Hannover, Hannover, Germany.
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Baldwin MR, Barbieri JT. Association of botulinum neurotoxins with synaptic vesicle protein complexes. Toxicon 2009; 54:570-4. [PMID: 19362106 DOI: 10.1016/j.toxicon.2009.01.040] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 01/25/2009] [Indexed: 11/19/2022]
Abstract
Botulinum neurotoxins (BoNTs) elicit flaccid paralysis by cleaving SNARE proteins within peripheral neurons. BoNTs are classified into seven serotypes, termed A-G, based on antibody cross-neutralization. Clostridia produce BoNTs as single-chain toxins that are cleaved into a di-chain protein that comprises an N-terminal zinc metalloprotease domain that is linked by a disulfide bond to the C-terminal translocation/receptor-binding domain. BoNT/A and BoNT/B utilize synaptic vesicle protein 2 (SV2) and synaptotagmin, respectively, as receptors for entry into neurons. Using affinity chromatography, BoNT/A and BoNT/B were found to bind a synaptic vesicle protein complex in CHAPS extracts of synaptic vesicles. Mass spectroscopy identified synaptic vesicle protein 2, synaptotagmin I, synaptophysin, vesicle-associated membrane protein 2, and the vacuolar ATPase-proton pump as components of the BoNT-synaptic vesicle protein complex. BoNT/A and BoNT/B possessed unique density-gradient profiles when bound to synaptic vesicle protein complexes. The identification of BoNT/A and BoNT/B bound to synaptic vesicle protein complexes provides insight into the interactions of BoNT and neuronal receptors.
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Affiliation(s)
- Michael R Baldwin
- Department of Microbiology and Molecular Genetics, 8701 Watertown Plank Rd., Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Brunger AT, Rummel A. Receptor and substrate interactions of clostridial neurotoxins. Toxicon 2009; 54:550-60. [PMID: 19268493 PMCID: PMC2756235 DOI: 10.1016/j.toxicon.2008.12.027] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/01/2008] [Accepted: 12/02/2008] [Indexed: 01/27/2023]
Abstract
The high potency of clostridial neurotoxins relies predominantly on their neurospecific binding and specific hydrolysis of SNARE proteins. Their multi-step mode of mechanism can be ascribed to their multi-domain three-dimensional structure. The C-terminal H(CC)-domain interacts subsequently with complex polysialo-gangliosides such as GT1b and a synaptic vesicle protein receptor via two neighbouring binding sites, resulting in highly specific uptake of the neurotoxins at synapses of cholinergic motoneurons. After its translocation the enzymatically active light chain specifically hydrolyses specific SNARE proteins, preventing SNARE complex assembly and thereby blocking exocytosis of neurotransmitter.
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Affiliation(s)
- Axel T Brunger
- The Howard Hughes Medical Institute and Departments of Molecular and Cellular Physiology, Neurology and Neurological Sciences, Structural Biology, and Photon Science, Stanford University, J.H. Clark Center, E300C, 318 Campus Drive, Stanford, CA 94305, USA.
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Willis B, Eubanks LM, Dickerson TJ, Janda KD. The strange case of the botulinum neurotoxin: using chemistry and biology to modulate the most deadly poison. Angew Chem Int Ed Engl 2008; 47:8360-79. [PMID: 18844202 DOI: 10.1002/anie.200705531] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the classic novella "The Strange Case of Dr. Jekyll and Mr. Hyde", Robert Louis Stevenson paints a stark picture of the duality of good and evil within a single man. Botulinum neurotoxin (BoNT), the most potent known toxin, possesses an analogous dichotomous nature: It shows a pronounced morbidity and mortality, but it is used with great effect in much lower doses in a wide range of clinical scenarios. Recently, tremendous strides have been made in the basic understanding of the structure and function of BoNT, which have translated into widespread efforts towards the discovery of biomacromolecules and small molecules that specifically modulate BoNT activity. Particular emphasis has been placed on the identification of inhibitors that can counteract BoNT exposure in the event of a bioterrorist attack. This Review summarizes the current advances in the development of therapeutics, including vaccines, peptides, and small-molecule inhibitors, for the prevention and treatment of botulism.
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Affiliation(s)
- Bert Willis
- Department of Chemistry, Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Willis B, Eubanks L, Dickerson T, Janda K. Der seltsame Fall des Botulinum-Neurotoxins: chemische und biologische Modulierung des tödlichsten aller Gifte. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Dong M, Liu H, Tepp WH, Johnson EA, Janz R, Chapman ER. Glycosylated SV2A and SV2B mediate the entry of botulinum neurotoxin E into neurons. Mol Biol Cell 2008; 19:5226-37. [PMID: 18815274 DOI: 10.1091/mbc.e08-07-0765] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Botulinum neurotoxin E (BoNT/E) can cause paralysis in humans and animals by blocking neurotransmitter release from presynaptic nerve terminals. How this toxin targets and enters neurons is not known. Here we identified two isoforms of the synaptic vesicle protein SV2, SV2A and SV2B, as the protein receptors for BoNT/E. BoNT/E failed to enter neurons cultured from SV2A/B knockout mice; entry was restored by expressing SV2A or SV2B, but not SV2C. Mice lacking SV2B displayed reduced sensitivity to BoNT/E. The fourth luminal domain of SV2A or SV2B alone, expressed in chimeric receptors by replacing the extracellular domain of the low-density lipoprotein receptor, can restore the binding and entry of BoNT/E into neurons lacking SV2A/B. Furthermore, we found disruption of a N-glycosylation site (N573Q) within the fourth luminal domain of SV2A rendered the mutant unable to mediate the entry of BoNT/E and also reduced the entry of BoNT/A. Finally, we demonstrate that BoNT/E failed to bind and enter ganglioside-deficient neurons; entry was rescued by loading exogenous gangliosides into neuronal membranes. Together, the data reported here demonstrate that glycosylated SV2A and SV2B act in conjunction with gangliosides to mediate the entry of BoNT/E into neurons.
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Affiliation(s)
- Min Dong
- Howard Hughes Medical Institute and Department of Physiology, University of Wisconsin, Madison, WI 53706, USA
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42
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Chen C, Baldwin MR, Barbieri JT. Molecular Basis for Tetanus Toxin Coreceptor Interactions. Biochemistry 2008; 47:7179-86. [DOI: 10.1021/bi800640y] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chen Chen
- Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226
| | - Michael R. Baldwin
- Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226
| | - Joseph T. Barbieri
- Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226
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Affiliation(s)
- Eric A Johnson
- Department of Bacteriology, Food Research Institute, University of Wisconsin, Madison, WI, USA.
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Abstract
Toxins that alter neurotransmitter release from nerve terminals are of considerable scientific and clinical importance. Many advances were recently made in the understanding of their molecular mechanisms of action and use in human therapy. Here, we focus on presynaptic neurotoxins, which are very potent inhibitors of the neurotransmitter release because they are endowed with specific enzymatic activities: (1) clostridial neurotoxins with a metallo-proteolytic activity and (2) snake presynaptic neurotoxins with a phospholipase A2 activity.
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Affiliation(s)
- Ornella Rossetto
- Departimento de Scienze Biomediche and Istituto CNR di Neuroscienze, Universita di Padova, Viale G. Colombo 3, 35121, Padova, Italy
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Dong M, Tepp WH, Liu H, Johnson EA, Chapman ER. Mechanism of botulinum neurotoxin B and G entry into hippocampal neurons. ACTA ACUST UNITED AC 2007; 179:1511-22. [PMID: 18158333 PMCID: PMC2373501 DOI: 10.1083/jcb.200707184] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Botulinum neurotoxins (BoNTs) target presynaptic nerve terminals by recognizing specific neuronal surface receptors. Two homologous synaptic vesicle membrane proteins, synaptotagmins (Syts) I and II, bind toxins BoNT/B and G. However, a direct demonstration that Syts I/II mediate toxin binding and entry into neurons is lacking. We report that BoNT/B and G fail to bind and enter hippocampal neurons cultured from Syt I knockout mice. Wild-type Syts I and II (but not Syt I loss-of-function toxin-binding domain mutants) restored binding and entry of BoNT/B and G in Syt I–null neurons, thus demonstrating that Syts I/II are protein receptors for BoNT/B and G. Furthermore, mice lacking complex gangliosides exhibit reduced sensitivity to BoNT/G, and binding and entry of BoNT/A, B, and G into hippocampal neurons lacking gangliosides is diminished. These data suggest that gangliosides are the shared coreceptor for BoNT/A, B, and G, supporting a double-receptor model for these three BoNTs for which the protein receptors are known.
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Affiliation(s)
- Min Dong
- Howard Hughes Medical Institute, Department of Physiology, University of Wisconsin, Madison, WI 53706, USA
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Abstract
Botulinum neurotoxins (BoNTs) are the most toxic proteins for humans and are classified as category A toxins. There are seven serotypes of BoNTs defined by the lack of cross-serotype toxin neutralization. Thus, an effective vaccine must neutralize each BoNT serotype. BoNTs are organized as dichain A-B toxins, where the N-terminal domain (light chain) is a zinc metalloprotease targeting soluble NSF attachment receptor proteins that is linked to the C-terminal domain (heavy chain [HC]) by a disulfide bond. The HC comprises a translocation domain and a C-terminal receptor binding domain (HCR). HCRs of the seven serotypes of BoNTs (hepta-HCR) were engineered for expression in Escherichia coli, and each HCR was purified from E. coli lysates. Immunization of mice with the E. coli-derived hepta-serotype HCR vaccine elicited an antibody response to each of the seven BoNT HCRs and neutralized challenge by 10,000 50% lethal doses of each of the seven BoNT serotypes. A solid-phase assay showed that the anti-hepta-serotype HCR sera inhibited the binding of HCR serotypes A and B to the ganglioside GT1b, the first step in BoNT intoxication of neurons. This is the first E. coli-derived vaccine that effectively neutralizes each of the seven BoNT serotypes.
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Abstract
The botulinum neurotoxins (BoNT) are the most toxic proteins for humans and designated "Category A Select Agents." The current vaccine against botulism is in limited supply, and there is a need to develop new vaccine strategies. A recombinant BoNT/A toxoid was produced in Clostridium botulinum that contained a double amino acid substitution, R363A Y365F (termed BoNT/A(RYM)). BoNT/A(RYM) was noncatalytic for SNAP25 and nontoxic for mice. Immunization with BoNT/A(RYM) protected mice from challenge at levels that were similar to chemically inactivated BoNT/A toxoid. BoNT/A(RYM) elicited an immune response against the light-chain and heavy-chain components of the toxin. Neutralizing anti-BoNT/A(RYM) sera blocked BoNT toxicity in primary cortical neurons and blocked ganglioside binding by the heavy chain. BoNT/A(RYM) represents a viable vaccine candidate for a holotoxoid against botulism.
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