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Navarro-Martínez A, Vicente-García C, Carvajal JJ. NMJ-related diseases beyond the congenital myasthenic syndromes. Front Cell Dev Biol 2023; 11:1216726. [PMID: 37601107 PMCID: PMC10436495 DOI: 10.3389/fcell.2023.1216726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/21/2023] [Indexed: 08/22/2023] Open
Abstract
Neuromuscular junctions (NMJs) are a special type of chemical synapse that transmits electrical stimuli from motor neurons (MNs) to their innervating skeletal muscle to induce a motor response. They are an ideal model for the study of synapses, given their manageable size and easy accessibility. Alterations in their morphology or function lead to neuromuscular disorders, such as the congenital myasthenic syndromes, which are caused by mutations in proteins located in the NMJ. In this review, we highlight novel potential candidate genes that may cause or modify NMJs-related pathologies in humans by exploring the phenotypes of hundreds of mouse models available in the literature. We also underscore the fact that NMJs may differ between species, muscles or even sexes. Hence the importance of choosing a good model organism for the study of NMJ-related diseases: only taking into account the specific features of the mammalian NMJ, experimental results would be efficiently translated to the clinic.
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Affiliation(s)
| | - Cristina Vicente-García
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, Spain
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Robbins M, Clayton E, Kaminski Schierle GS. Synaptic tau: A pathological or physiological phenomenon? Acta Neuropathol Commun 2021; 9:149. [PMID: 34503576 PMCID: PMC8428049 DOI: 10.1186/s40478-021-01246-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 08/12/2021] [Indexed: 12/17/2022] Open
Abstract
In this review, we discuss the synaptic aspects of Tau pathology occurring during Alzheimer's disease (AD) and how this may relate to memory impairment, a major hallmark of AD. Whilst the clinical diagnosis of AD patients is a loss of working memory and long-term declarative memory, the histological diagnosis is the presence of neurofibrillary tangles of hyperphosphorylated Tau and Amyloid-beta plaques. Tau pathology spreads through synaptically connected neurons to impair synaptic function preceding the formation of neurofibrillary tangles, synaptic loss, axonal retraction and cell death. Alongside synaptic pathology, recent data suggest that Tau has physiological roles in the pre- or post- synaptic compartments. Thus, we have seen a shift in the research focus from Tau as a microtubule-stabilising protein in axons, to Tau as a synaptic protein with roles in accelerating spine formation, dendritic elongation, and in synaptic plasticity coordinating memory pathways. We collate here the myriad of emerging interactions and physiological roles of synaptic Tau, and discuss the current evidence that synaptic Tau contributes to pathology in AD.
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Gundersen CB. Cysteine string proteins. Prog Neurobiol 2020; 188:101758. [DOI: 10.1016/j.pneurobio.2020.101758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 01/06/2020] [Accepted: 01/13/2020] [Indexed: 12/17/2022]
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Bachiller S, Roca-Ceballos MA, García-Domínguez I, Pérez-Villegas EM, Martos-Carmona D, Pérez-Castro MÁ, Real LM, Rosa JL, Tabares L, Venero JL, Armengol JÁ, Carrión ÁM, Ruiz R. HERC1 Ubiquitin Ligase Is Required for Normal Axonal Myelination in the Peripheral Nervous System. Mol Neurobiol 2018; 55:8856-8868. [PMID: 29603094 DOI: 10.1007/s12035-018-1021-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 03/16/2018] [Indexed: 12/14/2022]
Abstract
A missense mutation in HERC1 provokes loss of cerebellar Purkinje cells, tremor, and unstable gait in tambaleante (tbl) mice. Recently, we have shown that before cerebellar degeneration takes place, the tbl mouse suffers from a reduction in the number of vesicles available for release at the neuromuscular junction (NMJ). The aim of the present work was to study to which extent the alteration in HERC1 may affect other cells in the nervous system and how this may influence the motor dysfunction observed in these mice. The functional analysis showed a consistent delay in the propagation of the action potential in mutant mice in comparison with control littermates. Morphological analyses of glial cells in motor axons revealed signs of compact myelin damage as tomacula and local hypermyelination foci. Moreover, we observed an alteration in non-myelinated terminal Schwann cells at the level of the NMJ. Additionally, we found a significant increment of phosphorylated Akt-2 in the sciatic nerve. Based on these findings, we propose a molecular model that could explain how mutated HERC1 in tbl mice affects the myelination process in the peripheral nervous system. Finally, since the myelin abnormalities found in tbl mice are histological hallmarks of neuropathic periphery diseases, tbl mutant mice could be considered as a new mouse model for this type of diseases.
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Affiliation(s)
- Sara Bachiller
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain
| | - María Angustias Roca-Ceballos
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville, and Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Calle Profesor García González 2, 41012, Sevilla, Spain
| | - Irene García-Domínguez
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville, and Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Calle Profesor García González 2, 41012, Sevilla, Spain
| | - Eva María Pérez-Villegas
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain
| | - David Martos-Carmona
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain
| | - Miguel Ángel Pérez-Castro
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville, and Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Calle Profesor García González 2, 41012, Sevilla, Spain
| | - Luis Miguel Real
- Unit of Infectious Diseases and Microbiology, Valme University Hospital, Seville, Spain
| | - José Luis Rosa
- Departament de Ciències Fisiològiques II, IDIBELL, Campus de Bellvitge, Universitat de Barcelona, L'Hospitalet de Llobregat, E-08907, Barcelona, Spain
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - José Luis Venero
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville, and Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Calle Profesor García González 2, 41012, Sevilla, Spain
| | - José Ángel Armengol
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain
| | - Ángel Manuel Carrión
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain
| | - Rocío Ruiz
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Seville, Spain. .,Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville, and Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Calle Profesor García González 2, 41012, Sevilla, Spain.
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Tejero R, Lopez-Manzaneda M, Arumugam S, Tabares L. Synaptotagmin-2, and -1, linked to neurotransmission impairment and vulnerability in Spinal Muscular Atrophy. Hum Mol Genet 2018; 25:4703-4716. [PMID: 28173138 DOI: 10.1093/hmg/ddw297] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 08/22/2016] [Accepted: 08/23/2016] [Indexed: 01/19/2023] Open
Abstract
Spinal muscular atrophy (SMA) is the most frequent genetic cause of infant mortality. The disease is characterized by progressive muscle weakness and paralysis of axial and proximal limb muscles. It is caused by homozygous loss or mutation of the SMN1 gene, which codes for the Survival Motor Neuron (SMN) protein. In mouse models of the disease, neurotransmitter release is greatly impaired, but the molecular mechanisms of the synaptic dysfunction and the basis of the selective muscle vulnerability are unknown. In the present study, we investigated these open questions by comparing the molecular and functional properties of nerve terminals in severely and mildly affected muscles in the SMNΔ7 mouse model. We discovered that synaptotagmin-1 (Syt1) was developmentally downregulated in nerve terminals of highly affected muscles but not in low vulnerable muscles. Additionally, the expression levels of synaptotagmin-2 (Syt2), and its interacting protein, synaptic vesicle protein 2 (SV2) B, were reduced in proportion to the degree of muscle vulnerability while other synaptic proteins, such as syntaxin-1B (Stx1B) and synaptotagmin-7 (Syt7), were not affected. Consistently with the extremely low levels of both Syt-isoforms, and SV2B, in most affected neuromuscular synapses, the functional analysis of neurotransmission revealed highly reduced evoked release, altered short-term plasticity, low release probability, and inability to modulate normally the number of functional release sites. Together, we propose that the strong reduction of Syt2 and SV2B are key factors of the functional synaptic alteration and that the physiological downregulation of Syt1 plays a determinant role in muscle vulnerability in SMA.
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Affiliation(s)
- Rocío Tejero
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Mario Lopez-Manzaneda
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Saravanan Arumugam
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
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Ross JA, Webster RG, Lechertier T, Reynolds LE, Turmaine M, Bencze M, Jamshidi Y, Cetin H, Muntoni F, Beeson D, Hodilvala-Dilke K, Conti FJ. Multiple roles of integrin-α3 at the neuromuscular junction. J Cell Sci 2017; 130:1772-1784. [PMID: 28386022 PMCID: PMC5450193 DOI: 10.1242/jcs.201103] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 03/31/2017] [Indexed: 12/22/2022] Open
Abstract
The neuromuscular junction (NMJ) is the synapse between motoneurons and skeletal muscle, and is responsible for eliciting muscle contraction. Neurotransmission at synapses depends on the release of synaptic vesicles at sites called active zones (AZs). Various proteins of the extracellular matrix are crucial for NMJ development; however, little is known about the identity and functions of the receptors that mediate their effects. Using genetically modified mice, we find that integrin-α3 (encoded by Itga3), an adhesion receptor at the presynaptic membrane, is involved in the localisation of AZ components and efficient synaptic vesicle release. Integrin-α3 also regulates integrity of the synapse - mutant NMJs present with progressive structural changes and upregulated autophagy, features commonly observed during ageing and in models of neurodegeneration. Unexpectedly, we find instances of nerve terminal detachment from the muscle fibre; to our knowledge, this is the first report of a receptor that is required for the physical anchorage of pre- and postsynaptic elements at the NMJ. These results demonstrate multiple roles of integrin-α3 at the NMJ, and suggest that alterations in its function could underlie defects that occur in neurodegeneration or ageing.
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Affiliation(s)
- Jacob A Ross
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Richard G Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Tanguy Lechertier
- Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - Louise E Reynolds
- Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - Mark Turmaine
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Maximilien Bencze
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Yalda Jamshidi
- Department of Genetics, Institute of Molecular and Clinical Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK
| | - Hakan Cetin
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Kairbaan Hodilvala-Dilke
- Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - Francesco J Conti
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
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Lopez-Ortega E, Ruiz R, Tabares L. CSPα, a Molecular Co-chaperone Essential for Short and Long-Term Synaptic Maintenance. Front Neurosci 2017; 11:39. [PMID: 28239331 PMCID: PMC5301022 DOI: 10.3389/fnins.2017.00039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 01/19/2017] [Indexed: 01/26/2023] Open
Abstract
Cysteine string protein α (CSPα) is a vesicle protein located in the presynaptic terminal of most synapses. CSPα is an essential molecular co-chaperone that facilitates the correct folding of proteins and the assembly of the exocytic machinery. The absence of this protein leads to altered neurotransmitter release and neurodegeneration in multiple model systems, from flies to mice. In humans, CSPα mutations are associated with the development of neuronal ceroid lipofuscinosis (NCL), a neurodegenerative disease characterized by intracellular accumulation of lysosomal material. Here, we review the physiological role of CSPα and the pathology resulting from the homozygous deletion of the gene or its mutations. In addition, we investigate whether long-term moderate reduction of the protein produces motor dysfunction. We found that 1-year-old CSPα heterozygous mice display a reduced ability to sustain motor unit recruitment during repetitive stimulation, which indicates that physiological levels of CSPα are required for normal neuromuscular responses in mice and, likely, in humans.
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Affiliation(s)
- Elena Lopez-Ortega
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
| | - Rocío Ruiz
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Seville Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
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Fontaine SN, Zheng D, Sabbagh JJ, Martin MD, Chaput D, Darling A, Trotter JH, Stothert AR, Nordhues BA, Lussier A, Baker J, Shelton L, Kahn M, Blair LJ, Stevens SM, Dickey CA. DnaJ/Hsc70 chaperone complexes control the extracellular release of neurodegenerative-associated proteins. EMBO J 2016; 35:1537-49. [PMID: 27261198 PMCID: PMC4946142 DOI: 10.15252/embj.201593489] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 04/25/2016] [Accepted: 04/27/2016] [Indexed: 12/12/2022] Open
Abstract
It is now known that proteins associated with neurodegenerative disease can spread throughout the brain in a prionlike manner. However, the mechanisms regulating the trans-synaptic spread propagation, including the neuronal release of these proteins, remain unknown. The interaction of neurodegenerative disease-associated proteins with the molecular chaperone Hsc70 is well known, and we hypothesized that much like disaggregation, refolding, degradation, and even normal function, Hsc70 may dictate the extracellular fate of these proteins. Here, we show that several proteins, including TDP-43, α-synuclein, and the microtubule-associated protein tau, can be driven out of the cell by an Hsc70 co-chaperone, DnaJC5. In fact, DnaJC5 overexpression induced tau release in cells, neurons, and brain tissue, but only when activity of the chaperone Hsc70 was intact and when tau was able to associate with this chaperone. Moreover, release of tau from neurons was reduced in mice lacking the DnaJC5 gene and when the complement of DnaJs in the cell was altered. These results demonstrate that the dynamics of DnaJ/Hsc70 complexes are critically involved in the release of neurodegenerative disease proteins.
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Affiliation(s)
- Sarah N Fontaine
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA James A. Haley Veteran's Hospital, Tampa, FL, USA
| | - Dali Zheng
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Jonathan J Sabbagh
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA James A. Haley Veteran's Hospital, Tampa, FL, USA
| | - Mackenzie D Martin
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA James A. Haley Veteran's Hospital, Tampa, FL, USA
| | - Dale Chaput
- Department of Cell, Molecular and Life Sciences, University of South Florida, Tampa, FL, USA
| | - April Darling
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Justin H Trotter
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA
| | - Andrew R Stothert
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Bryce A Nordhues
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - April Lussier
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Jeremy Baker
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Lindsey Shelton
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Mahnoor Kahn
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Laura J Blair
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA
| | - Stanley M Stevens
- Department of Cell, Molecular and Life Sciences, University of South Florida, Tampa, FL, USA
| | - Chad A Dickey
- Department of Molecular Medicine, College of Medicine, Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, USA James A. Haley Veteran's Hospital, Tampa, FL, USA
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Bachiller S, Rybkina T, Porras-García E, Pérez-Villegas E, Tabares L, Armengol JA, Carrión AM, Ruiz R. The HERC1 E3 Ubiquitin Ligase is essential for normal development and for neurotransmission at the mouse neuromuscular junction. Cell Mol Life Sci 2015; 72:2961-71. [PMID: 25746226 PMCID: PMC11113414 DOI: 10.1007/s00018-015-1878-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/15/2015] [Accepted: 02/27/2015] [Indexed: 12/14/2022]
Abstract
The ubiquitin-proteasome system (UPS) plays a fundamental role in protein degradation in neurons, and there is strong evidence that it fulfills a key role in synaptic transmission. The aim of the present work was to study the implication of one component of the UPS, the HERC1 E3 Ubiquitin Ligase, in motor function and neuromuscular transmission. The tambaleante (tbl) mutant mouse carries a spontaneous mutation in HERC1 E3 Ubiquitin Ligase, provoking an ataxic phenotype that develops in the second month of life. Our results show that motor performance in mutant mice is altered at postnatal day 30, before the cerebellar neurodegeneration takes place. This defect is associated with by: (a) a reduction of the motor end-plate area, (b) less efficient neuromuscular activity in vivo, and (c) an impaired evoked neurotransmitter release. Together, these data suggest that the HERC1 E3 Ubiquitin Ligase is fundamental for normal muscle function and that it is essential for neurotransmitter release at the mouse neuromuscular junction.
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Affiliation(s)
- S. Bachiller
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
| | - T. Rybkina
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
| | - E. Porras-García
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
| | - E. Pérez-Villegas
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
| | - L. Tabares
- Department of Medical Physiology and Biophysics, University of Seville, Seville, Spain
| | - J. A. Armengol
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
- School of Medicine, University of Cartagena de Indias, Cartagena, Colombia
| | - A. M. Carrión
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
| | - R. Ruiz
- Department of Physiology, Anatomy and Cellular Biology, University of Pablo de Olavide, Carretera de Utrera Km 1, 41013 Seville, Spain
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Burgoyne RD, Morgan A. Cysteine string protein (CSP) and its role in preventing neurodegeneration. Semin Cell Dev Biol 2015; 40:153-9. [PMID: 25800794 PMCID: PMC4447612 DOI: 10.1016/j.semcdb.2015.03.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 03/16/2015] [Indexed: 11/25/2022]
Abstract
Cysteine string protein (CSP) is a member of the DnaJ/Hsp40 family of co-chaperones that localises to neuronal synaptic vesicles. Its name derives from the possession of a string of 12–15 cysteine residues, palmitoylation of which is required for targeting to post-Golgi membranes. The DnaJ domain of CSP enables it to bind client proteins and recruit Hsc70 chaperones, thereby contributing to the maintenance of protein folding in the presynaptic compartment. Mutation of CSP in flies, worms and mice reduces lifespan and causes synaptic dysfunction and neurodegeneration. Furthermore, recent studies have revealed that the neurodegenerative disease, adult onset neuronal ceroid lipofuscinosis, is caused by mutations in the human CSPα-encoding DNAJC5 gene. Accumulating evidence suggests that the major mechanism by which CSP prevents neurodegeneration is by maintaining the conformation of SNAP-25, thereby facilitating its entry into the membrane-fusing SNARE complex. In this review, we focus on the role of CSP in preventing neurodegeneration and discuss how recent studies of this universal neuroprotective chaperone are being translated into potential novel therapeutics for neurodegenerative diseases.
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Affiliation(s)
- Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown St., Liverpool L69 3BX, UK
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown St., Liverpool L69 3BX, UK.
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Donnelier J, Braun JEA. CSPα-chaperoning presynaptic proteins. Front Cell Neurosci 2014; 8:116. [PMID: 24808827 PMCID: PMC4010753 DOI: 10.3389/fncel.2014.00116] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 04/09/2014] [Indexed: 12/11/2022] Open
Abstract
Synaptic transmission relies on precisely regulated and exceedingly fast protein-protein interactions that involve voltage-gated channels, the exocytosis/endocytosis machinery as well as signaling pathways. Although we have gained an ever more detailed picture of synaptic architecture much remains to be learned about how synapses are maintained. Synaptic chaperones are “folding catalysts” that preserve proteostasis by regulating protein conformation (and therefore protein function) and prevent unwanted protein-protein interactions. Failure to maintain synapses is an early hallmark of several degenerative diseases. Cysteine string protein (CSPα) is a presynaptic vesicle protein and molecular chaperone that has a central role in preventing synaptic loss and neurodegeneration. Over the past few years, a number of different “client proteins” have been implicated as CSPα substrates including voltage-dependent ion channels, signaling proteins and proteins critical to the synaptic vesicle cycle. Here we review the ion channels and synaptic protein complexes under the influence of CSPα and discuss gaps in our current knowledge.
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Affiliation(s)
- Julien Donnelier
- Department of Physiology and Pharmacology, The Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary Calgary, AB, Canada
| | - Janice E A Braun
- Department of Physiology and Pharmacology, The Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary Calgary, AB, Canada
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Ahrendt E, Kyle B, Braun AP, Braun JEA. Cysteine string protein limits expression of the large conductance, calcium-activated K⁺ (BK) channel. PLoS One 2014; 9:e86586. [PMID: 24475152 PMCID: PMC3903548 DOI: 10.1371/journal.pone.0086586] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 12/15/2013] [Indexed: 01/12/2023] Open
Abstract
Large-conductance, calcium-activated K+ (BK) channels are widely distributed throughout the nervous system and play an essential role in regulation of action potential duration and firing frequency, along with neurotransmitter release at the presynaptic terminal. We have previously demonstrated that select mutations in cysteine string protein (CSPα), a presynaptic J-protein and co-chaperone, increase BK channel expression. This observation raised the possibility that wild-type CSPα normally functions to limit neuronal BK channel expression. Here we show by Western blot analysis of transfected neuroblastoma cells that when BK channels are present at elevated levels, CSPα acts to reduce expression. Moreover, we demonstrate that the accessory subunits, BKβ4 and BKβ1 do not alter CSPα-mediated reduction of expressed BKα subunits. Structure-function analysis reveals that the N-terminal J-domain of CSPα is critical for the observed regulation of BK channels levels. Finally, we demonstrate that CSPα limits BK current amplitude, while the loss-of-function homologue CSPαHPD-AAA increases BK current. Our observations indicate that CSPα has a role in regulating synaptic excitability and neurotransmission by limiting expression of BK channels.
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Affiliation(s)
- Eva Ahrendt
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Barry Kyle
- Libin Cardiovascular Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Libin Cardiovascular Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Janice E. A. Braun
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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14
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Barth J, Volknandt W. Proteomic investigations of the synaptic vesicle interactome. Expert Rev Proteomics 2014; 8:211-20. [DOI: 10.1586/epr.11.7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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α-Synuclein A30P decreases neurodegeneration and increases synaptic vesicle release probability in CSPα-null mice. Neuropharmacology 2013; 76 Pt A:106-17. [PMID: 24036317 DOI: 10.1016/j.neuropharm.2013.08.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 08/19/2013] [Accepted: 08/23/2013] [Indexed: 12/24/2022]
Abstract
α-Synuclein and Cysteine-string protein-α (CSPα) are presynaptic proteins that participate in the maintenance of synaptic function. Mutations or overexpression of the wild type form of α-synuclein have been related to Parkinson's disease, and CSPα mutations cause one type of neuronal ceroid lipofuscinosis. Both are adult-onset neurodegenerative diseases characterized by neuronal protein aggregations. Strikingly, while in mouse the lack of CSPα produces defective neurotransmission and neurodegeneration of motor terminals, blindness and early lethality, the moderate overexpression of wild-type α-synuclein fully rescues the CSPα-null phenotype. Contrarily, the overexpression of the mutated human α-synuclein A30P (α-synuclein(hA30P)) has much less effect in CSPα KO mice. To explore how the A30P mutation affects the neuroprotective function of α-synuclein we investigated synaptic structure and neurotransmission in motor nerve terminals of wild-type and CSPα-null mice transgenic for α-synuclein(hA30P). We found that although α-synuclein(hA30P) did not fully prevent neurodegeneration, it significantly improved synaptic organization and function in CSPα-null mice by enhancing quantal content, release probability, synaptic vesicle content, active zone number, postsynaptic area, and microtubule appearance. These results demonstrate that α-synuclein(hA30P) is able to ameliorate synapse degeneration, despite its apparent lack of functionality and its long-term pathogenic effects in neurons. These findings may help to understand better the dual function of α-synuclein regarding neurodegeneration. This article is part of the Special Issue entitled 'The Synaptic Basis of Neurodegenerative Disorders'.
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Hu HY, He L, Fominykh K, Yan Z, Guo S, Zhang X, Taylor MS, Tang L, Li J, Liu J, Wang W, Yu H, Khaitovich P. Evolution of the human-specific microRNA miR-941. Nat Commun 2013; 3:1145. [PMID: 23093182 PMCID: PMC3493648 DOI: 10.1038/ncomms2146] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 09/20/2012] [Indexed: 01/22/2023] Open
Abstract
MicroRNA-mediated gene regulation is important in many physiological processes. Here we explore the roles of a microRNA, miR-941, in human evolution. We find that miR-941 emerged de novo in the human lineage, between six and one million years ago, from an evolutionarily volatile tandem repeat sequence. Its copy-number remains polymorphic in humans and shows a trend for decreasing copy-number with migration out of Africa. Emergence of miR-941 was accompanied by accelerated loss of miR-941-binding sites, presumably to escape regulation. We further show that miR-941 is highly expressed in pluripotent cells, repressed upon differentiation and preferentially targets genes in hedgehog- and insulin-signalling pathways, thus suggesting roles in cellular differentiation. Human-specific effects of miR-941 regulation are detectable in the brain and affect genes involved in neurotransmitter signalling. Taken together, these results implicate miR-941 in human evolution, and provide an example of rapid regulatory evolution in the human linage.
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Affiliation(s)
- Hai Yang Hu
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, 320 Yue Yang Road, Shanghai 200031, China
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17
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Fast motor axon loss in SMARD1 does not correspond to morphological and functional alterations of the NMJ. Neurobiol Dis 2013; 54:169-82. [PMID: 23295857 DOI: 10.1016/j.nbd.2012.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Revised: 11/30/2012] [Accepted: 12/21/2012] [Indexed: 11/20/2022] Open
Abstract
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a childhood motoneuron disease caused by mutations in the gene encoding for IGHMBP2, an ATPase/Helicase. Paralysis of the diaphragm is an early and prominent clinical sign resulting both from denervation and myopathy. In skeletal muscles, muscle atrophy mainly results from loss of motoneuron cell bodies and axonal degeneration. Although it is well known that loss of motoneurons at the lumbar spinal cord is an early event in the pathogenesis of the disease, it is not clear whether the corresponding proximal axons and NMJs are also early affected. In order to address this question, we have investigated the time course of the disease progression at the level of the motoneuron cell body, proximal axon (ventral root), distal axon (sciatic nerve), NMJ, and muscle fiber in Nmd(2J) mice, a mouse model for SMARD1. Our results show an early and apparently parallel loss of motoneurons, proximal axons, and NMJs. In affected muscles, however, denervated fibers coexist with NMJs with normal morphology and unaltered neurotransmission. Furthermore, unaffected axons are able to sprout and reinnervate muscle fibers, suggesting selective vulnerability of neurons to Ighmbp2 deficiency. The preservation of the NMJ morphology and neurotransmission in the Nmd(2J) mouse until motor axon loss takes place, differs from that observed in SMA mouse models in which NMJ impairment is an early and more general phenomenon in affected muscles.
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Cano R, Torres-Benito L, Tejero R, Biea AI, Ruiz R, Betz WJ, Tabares L. Structural and functional maturation of active zones in large synapses. Mol Neurobiol 2012; 47:209-19. [PMID: 22992975 DOI: 10.1007/s12035-012-8347-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 08/27/2012] [Indexed: 11/29/2022]
Abstract
Virtually all functions of the nervous system rely upon synapses, the sites of communication between neurons and between neurons and other cells. Synapses are complex structures, each one comprising hundreds of different types of molecules working in concert. They are organized by adhesive and scaffolding molecules that align presynaptic vesicular release sites, namely, active zones, with postsynaptic neurotransmitter receptors, thereby allowing rapid and reliable intercellular communication. Most synapses are relatively small, and acting alone exerts little effect on their postsynaptic partners. Some, however, are much larger and stronger, reliably driving the postsynaptic cell to its action potential threshold, acting essentially as electrical relays of excitation. These large synapses are among the best understood, and two of these are the subject of this review, namely, the vertebrate neuromuscular junction and the calyx of Held synapse in the mammalian auditory pathway of the brain stem. Both synapses undergo through a complex and well-coordinated maturation process, during which time the molecular elements and the biophysical properties of the secretory machinery are continuously adjusted to the synapse size and to the functional requirements. We here review the morphological and functional changes occurring during postnatal maturation, noting particular similarities and differences between these two large synapses.
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Affiliation(s)
- Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sanchez Pizjuan 4, 41009, Seville, Spain
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Motorneurons Require Cysteine String Protein-α to Maintain the Readily Releasable Vesicular Pool and Synaptic Vesicle Recycling. Neuron 2012; 74:151-65. [DOI: 10.1016/j.neuron.2012.02.019] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2012] [Indexed: 11/22/2022]
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20
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Torres-Benito L, Neher MF, Cano R, Ruiz R, Tabares L. SMN requirement for synaptic vesicle, active zone and microtubule postnatal organization in motor nerve terminals. PLoS One 2011; 6:e26164. [PMID: 22022549 PMCID: PMC3192162 DOI: 10.1371/journal.pone.0026164] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 09/21/2011] [Indexed: 11/18/2022] Open
Abstract
Low levels of the Survival Motor Neuron (SMN) protein produce Spinal Muscular Atrophy (SMA), a severe monogenetic disease in infants characterized by muscle weakness and impaired synaptic transmission. We report here severe structural and functional alterations in the organization of the organelles and the cytoskeleton of motor nerve terminals in a mouse model of SMA. The decrease in SMN levels resulted in the clustering of synaptic vesicles (SVs) and Active Zones (AZs), reduction in the size of the readily releasable pool (RRP), and the recycling pool (RP) of synaptic vesicles, a decrease in active mitochondria and limiting of neurofilament and microtubule maturation. We propose that SMN is essential for the normal postnatal maturation of motor nerve terminals and that SMN deficiency disrupts the presynaptic organization leading to neurodegeneration.
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Affiliation(s)
- Laura Torres-Benito
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Margret Feodora Neher
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Rocio Ruiz
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
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Abstract
Cysteine-string protein (CSP), a member of the DnaJ/Hsp40 family of cochaperones, is critical for maintaining neurotransmitter release and preventing neurodegeneration. CSP likely forms a chaperone complex on synaptic vesicles together with the 70-kDa heat shock cognate (Hsc70) and the small glutamine-rich tetratricopeptide repeat (TPR)-containing protein (SGT) that may control or protect the assembly and activity of SNARE proteins and various other protein substrates. Here, the author summarizes studies that elucidated CSP's neuroprotective role.
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Affiliation(s)
- Konrad E Zinsmaier
- Department of Neuroscience and Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721-0077, USA.
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22
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Active zones and the readily releasable pool of synaptic vesicles at the neuromuscular junction of the mouse. J Neurosci 2011; 31:2000-8. [PMID: 21307238 DOI: 10.1523/jneurosci.4663-10.2011] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synchronous neurotransmitter release is a highly regulated process that takes place at specializations at the presynaptic membrane called active zones (AZs). The relationships between AZs, quantal release, and vesicle replenishment are not well understood in a mature synapse. We have measured the number, distribution, and other properties of AZs in mouse motor nerve terminals and combined these observations with electrophysiological estimates of the size of the readily releasable pool (RRP) of synaptic vesicles. On average, we counted 850 AZs per terminal. Assuming two primary docked vesicles per AZ, we predict a total of ∼1700 vesicles optimally positioned for exocytosis. Electrophysiological estimates of the size of the RRP, using a simple kinetic model that assumes exponential depletion of the initial pool and refilling by recruitment, gave an average value of 1730 quanta during 100 Hz stimulation, in satisfying agreement with the morphology. At lower stimulus frequencies, however, the model revealed that the estimated RRP size is smaller, suggesting that not all AZs participate in release at low stimulation frequencies.
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Sharma M, Burré J, Südhof TC. CSPα promotes SNARE-complex assembly by chaperoning SNAP-25 during synaptic activity. Nat Cell Biol 2010; 13:30-9. [PMID: 21151134 DOI: 10.1038/ncb2131] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 10/28/2010] [Indexed: 12/26/2022]
Abstract
A neuron forms thousands of presynaptic nerve terminals on its axons, far removed from the cell body. The protein CSPα resides in presynaptic terminals, where it forms a chaperone complex with Hsc70 and SGT. Deletion of CSPα results in massive neurodegeneration that impairs survival in mice and flies. In CSPα-knockout mice, levels of presynaptic SNARE complexes and the SNARE protein SNAP-25 are reduced, suggesting that CSPα may chaperone SNARE proteins, which catalyse synaptic vesicle fusion. Here, we show that the CSPα-Hsc70-SGT complex binds directly to monomeric SNAP-25 to prevent its aggregation, enabling SNARE-complex formation. Deletion of CSPα produces an abnormal SNAP-25 conformer that inhibits SNARE-complex formation, and is subject to ubiquitylation and proteasomal degradation. Even in wild-type mouse terminals, SNAP-25 degradation is regulated by synaptic activity; this degradation is decreased by CSPα overexpression, and enhanced by CSPα deletion. Thus, SNAP-25 function is maintained during rapid SNARE cycles by equilibrium between CSPα-dependent chaperoning and ubiquitin-dependent degradation, revealing unique protein quality-control machinery within the presynaptic compartment.
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Affiliation(s)
- Manu Sharma
- Department of Molecular and Cellular Physiology, Stanford University, SIM1, 265 Campus Drive, Palo Alto, CA 94304-5453, USA.
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24
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Boal F, Laguerre M, Milochau A, Lang J, Scotti PA. A charged prominence in the linker domain of the cysteine‐string protein Cspα mediates its regulated interaction with the calcium sensor synaptotagmin 9 during exocytosis. FASEB J 2010; 25:132-43. [DOI: 10.1096/fj.09-152033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Frédéric Boal
- Department of BiochemistrySchool of Medical SciencesUniversity of BristolBristolUK
| | - Michel Laguerre
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Alexandra Milochau
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Jochen Lang
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
| | - Pier A. Scotti
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 5248Universitedé Bordeaux IPessacFrance
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Duncan G, Rabl K, Gemp I, Heidelberger R, Thoreson WB. Quantitative analysis of synaptic release at the photoreceptor synapse. Biophys J 2010; 98:2102-10. [PMID: 20483317 DOI: 10.1016/j.bpj.2010.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 01/11/2010] [Accepted: 02/02/2010] [Indexed: 02/02/2023] Open
Abstract
Exocytosis from the rod photoreceptor is stimulated by submicromolar Ca(2+) and exhibits an unusually shallow dependence on presynaptic Ca(2+). To provide a quantitative description of the photoreceptor Ca(2+) sensor for exocytosis, we tested a family of conventional and allosteric computational models describing the final Ca(2+)-binding steps leading to exocytosis. Simulations were fit to two measures of release, evoked by flash-photolysis of caged Ca(2+): exocytotic capacitance changes from individual rods and postsynaptic currents of second-order neurons. The best simulations supported the occupancy of only two Ca(2+) binding sites on the rod Ca(2+) sensor rather than the typical four or five. For most models, the on-rates for Ca(2+) binding and maximal fusion rate were comparable to those of other neurons. However, the off-rates for Ca(2+) unbinding were unexpectedly slow. In addition to contributing to the high-affinity of the photoreceptor Ca(2+) sensor, slow Ca(2+) unbinding may support the fusion of vesicles located at a distance from Ca(2+) channels. In addition, partial sensor occupancy due to slow unbinding may contribute to the linearization of the first synapse in vision.
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Affiliation(s)
- Gabriel Duncan
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas, USA
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26
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Cysteine string protein-alpha prevents activity-dependent degeneration in GABAergic synapses. J Neurosci 2010; 30:7377-91. [PMID: 20505105 DOI: 10.1523/jneurosci.0924-10.2010] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The continuous release of neurotransmitter could be seen to place a persistent burden on presynaptic proteins, one that could compromise nerve terminal function. This supposition and the molecular mechanisms that might protect highly active synapses merit investigation. In hippocampal cultures from knock-out mice lacking the presynaptic cochaperone cysteine string protein-alpha (CSP-alpha), we observe progressive degeneration of highly active synaptotagmin 2 (Syt2)-expressing GABAergic synapses, but surprisingly not of glutamatergic terminals. In CSP-alpha knock-out mice, synaptic degeneration of basket cell terminals occurs in vivo in the presence of normal glutamatergic synapses onto dentate gyrus granule cells. Consistent with this, in hippocampal cultures from these mice, the frequency of miniature IPSCs, caused by spontaneous GABA release, progressively declines, whereas the frequency of miniature excitatory AMPA receptor-mediated currents (mEPSCs), caused by spontaneous release of glutamate, is normal. However, the mEPSC amplitude progressively decreases. Remarkably, long-term block of glutamatergic transmission in cultures lacking CSP-alpha substantially rescues Syt2-expressing GABAergic synapses from neurodegeneration. These findings demonstrate that elevated neural activity increases synapse vulnerability and that CSP-alpha is essential to maintain presynaptic function under a physiologically high-activity regimen.
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Altered intracellular Ca2+ homeostasis in nerve terminals of severe spinal muscular atrophy mice. J Neurosci 2010; 30:849-57. [PMID: 20089893 DOI: 10.1523/jneurosci.4496-09.2010] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Low levels of survival motor neuron (SMN) protein result in spinal muscular atrophy (SMA), a severe genetic disease characterized by motor impairment and premature lethality. Although SMN is a ubiquitous protein, motor neurons are much more vulnerable to low levels of SMN than other cells. To gain insight into the pathogenesis of SMA, we have compared synaptic function of motor terminals in wild-type and severe SMA mice at different ages and in two proximal muscles. Our results show that mutant muscle fibers fire normal action potentials and that multi-innervated terminals are functional. By studying the characteristics of the three main components of synaptic transmission in nerve terminals (spontaneous, evoked, and asynchronous release), we found that the kinetics of the postsynaptic potentials are slowed and evoked neurotransmitter release is decreased by approximately 55%. In addition, asynchronous release is increased approximately 300%, indicating an anomalous augmentation of intraterminal bulk Ca(2+) during repetitive stimulation. Together, these results show that the reduction of SMN affects synaptic maturation, evoked release, and regulation of intraterminal Ca(2+) levels.
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28
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Prescott GR, Gorleku OA, Greaves J, Chamberlain LH. Palmitoylation of the synaptic vesicle fusion machinery. J Neurochem 2009; 110:1135-49. [PMID: 19508429 DOI: 10.1111/j.1471-4159.2009.06205.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion of synaptic vesicles with the pre-synaptic plasma membrane mediates the secretion of neurotransmitters at nerve terminals. This pathway is regulated by an array of protein-protein interactions. Of central importance are the soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor (SNARE) proteins syntaxin 1 and SNAP25, which are associated with the pre-synaptic plasma membrane and vesicle-associated membrane protein (VAMP2), a synaptic vesicle SNARE. Syntaxin 1, SNAP25 and VAMP2 interact to form a tight complex bridging the vesicle and plasma membranes, which has been suggested to represent the minimal membrane fusion machinery. Synaptic vesicle fusion is stimulated by a rise in intraterminal Ca2+ levels, and a major Ca2+ sensor for vesicle fusion is synaptotagmin I. Synaptotagmin is likely to couple Ca2+ entry to vesicle fusion via Ca2+-dependent and independent interactions with membrane phospholipids and the SNARE proteins. Intriguingly, syntaxin 1, SNAP25, VAMP2 and synaptotagmin I have all been reported to be modified by palmitoylation in neurons. In this review, we discuss the mechanisms and dynamics of palmitoylation of these proteins and speculate on how palmitoylation might contribute to the regulation of synaptic vesicle fusion.
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Affiliation(s)
- Gerald R Prescott
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
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29
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Gibbs SJ, Barren B, Beck KE, Proft J, Zhao X, Noskova T, Braun AP, Artemyev NO, Braun JEA. Hsp40 couples with the CSPalpha chaperone complex upon induction of the heat shock response. PLoS One 2009; 4:e4595. [PMID: 19242542 PMCID: PMC2643527 DOI: 10.1371/journal.pone.0004595] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 01/13/2009] [Indexed: 01/22/2023] Open
Abstract
In response to a conditioning stress, the expression of a set of molecular chaperones called heat shock proteins is increased. In neurons, stress-induced and constitutively expressed molecular chaperones protect against damage induced by ischemia and neurodegenerative diseases, however the molecular basis of this protection is not known. Here we have investigated the crosstalk between stress-induced chaperones and cysteine string protein (CSPα). CSPα is a constitutively expressed synaptic vesicle protein bearing a J domain and a cysteine rich “string” region that has been implicated in the long term functional integrity of synaptic transmission and the defense against neurodegeneration. We have shown previously that the CSPα chaperone complex increases isoproterenol-mediated signaling by stimulating GDP/GTP exchange of Gαs. In this report we demonstrate that in response to heat shock or treatment with the Hsp90 inhibitor geldanamycin, the J protein Hsp40 becomes a major component of the CSPα complex. Association of Hsp40 with CSPα decreases CSPα-CSPα dimerization and enhances the CSPα-induced increase in steady state GTP hydrolysis of Gαs. This newly identified CSPα-Hsp40 association reveals a previously undescribed coupling of J proteins. In view of the crucial importance of stress-induced chaperones in the protection against cell death, our data attribute a role for Hsp40 crosstalk with CSPα in neuroprotection.
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Affiliation(s)
- Sarah J. Gibbs
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Brandy Barren
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
| | - Katy E. Beck
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Juliane Proft
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Xiaoxi Zhao
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Tatiana Noskova
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Department of Pharmacology and Therapeutics & Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Nikolai O. Artemyev
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
| | - Janice E. A. Braun
- Department of Physiology and Biophysics & Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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30
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Prescott GR, Jenkins RE, Walsh CM, Morgan A. Phosphorylation of cysteine string protein on Serine 10 triggers 14-3-3 protein binding. Biochem Biophys Res Commun 2008; 377:809-14. [DOI: 10.1016/j.bbrc.2008.10.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 10/11/2008] [Indexed: 10/21/2022]
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