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Li Y, Patel M, Baroudi J, Wu M, Gatti S, Liang M, Wipf P, Badawi Y, Meriney SD. A cross-sectional study of ageing at the mouse neuromuscular junction and effects of an experimental therapeutic approach for dynapenia. J Physiol 2023; 601:4135-4150. [PMID: 37606613 DOI: 10.1113/jp284749] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 08/08/2023] [Indexed: 08/23/2023] Open
Abstract
Despite prior efforts to understand and target dynapenia (age-induced loss of muscle strength), this condition remains a major challenge that reduces the quality of life in the aged population. We have focused on the neuromuscular junction (NMJ) where changes in structure and function have rarely been systematically studied as a dynamic and progressive process. Our cross-sectional study found neurotransmission at the male mouse NMJ to be biphasic, displaying an early increase followed by a later decrease, and this phenotype was associated with structural changes to the NMJ. A cross-sectional characterization showed that age-induced alterations fell into four age groups: young adult (3-6 months), adult (7-18 months), early aged (19-24 months), and later aged (25-30 months). We then utilized a small molecule therapeutic candidate, GV-58, applied acutely during the later aged stage to combat age-induced reductions in transmitter release by increasing calcium influx during an action potential, which resulted in a significant increase in transmitter release. This comprehensive study of neuromuscular ageing at the NMJ will enable future research to target critical time points for therapeutic intervention. KEY POINTS: Age-induced frailty and falls are the leading causes of injury-related death and are caused by an age-induced loss of muscle strength due to a combination of neurological and muscular changes. A cross-sectional approach was used to study age-induced changes to the neuromuscular junction in a mouse model, and physiological changes that were biphasic over the ageing time course were found. Changes in physiology at the neuromuscular junction were correlated with alterations in neuromuscular junction morphology. An acutely applied positive allosteric gating modifier of presynaptic voltage-gated calcium channels was tested as a candidate therapeutic strategy that could increase transmitter release at aged neuromuscular junctions. These results provide a detailed time course of age-induced changes at the neuromuscular junction in a mouse model and test a candidate therapeutic strategy for weakness.
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Affiliation(s)
- Y Li
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - M Patel
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - J Baroudi
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - M Wu
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - S Gatti
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - M Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - P Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Y Badawi
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
| | - Stephen D Meriney
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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Ojala KS, Kaufhold CJ, Davey MR, Yang D, Liang M, Wipf P, Badawi Y, Meriney SD. Potentiation of neuromuscular transmission by a small molecule calcium channel gating modifier improves motor function in a severe spinal muscular atrophy mouse model. Hum Mol Genet 2023; 32:1901-1911. [PMID: 36757138 DOI: 10.1093/hmg/ddad019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 01/03/2023] [Accepted: 01/24/2023] [Indexed: 02/10/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a monogenic disease that clinically manifests as severe muscle weakness owing to neurotransmission defects and motoneuron degeneration. Individuals affected by SMA experience neuromuscular weakness that impacts functional activities of daily living. We have used a mouse model of severe SMA (SMNΔ7) to test whether a calcium channel gating modifier (GV-58), alone or in combination with a potassium channel antagonist (3,4-diaminopyridine; 3,4-DAP), can improve neuromuscular function in this mouse model. Bath application of GV-58 alone or in combination with 3,4-DAP significantly restored neuromuscular transmission to control levels in both a mildly vulnerable forearm muscle and a strongly vulnerable trunk muscle in SMNΔ7 mice at postnatal days 10-12. Similarly, acute subcutaneous administration of GV-58 to postnatal day 10 SMNΔ7 mice, alone or in combination with 3,4-DAP, significantly increased a behavioral measure of muscle strength. These data suggest that GV-58 may be a promising treatment candidate that could address deficits in neuromuscular function and strength and that the addition of 3,4-DAP to GV-58 treatment could aid in restoring function in SMA.
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Affiliation(s)
- Kristine S Ojala
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Cassandra J Kaufhold
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Mykenzie R Davey
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Donggyun Yang
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Yomna Badawi
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
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3
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Ginebaugh SP, Badawi Y, Laghaei R, Mersky G, Wallace CJ, Tarr TB, Kaufhold C, Reddel S, Meriney SD. Simulations of active zone structure and function at mammalian NMJs predict that loss of calcium channels alone is not sufficient to replicate LEMS effects. J Neurophysiol 2023; 129:1259-1277. [PMID: 37073966 PMCID: PMC10202491 DOI: 10.1152/jn.00404.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 04/14/2023] [Accepted: 04/14/2023] [Indexed: 04/20/2023] Open
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune-mediated neuromuscular disease thought to be caused by autoantibodies against P/Q-type voltage-gated calcium channels (VGCCs), which attack and reduce the number of VGCCs within transmitter release sites (active zones; AZs) at the neuromuscular junction (NMJ), resulting in neuromuscular weakness. However, patients with LEMS also have antibodies to other neuronal proteins, and about 15% of patients with LEMS are seronegative for antibodies against VGCCs. We hypothesized that a reduction in the number of P/Q-type VGCCs alone is not sufficient to explain LEMS effects on transmitter release. Here, we used a computational model to study a variety of LEMS-mediated effects on AZ organization and transmitter release constrained by electron microscopic, pharmacological, immunohistochemical, voltage imaging, and electrophysiological observations. We show that models of healthy AZs can be modified to predict the transmitter release and short-term facilitation characteristics of LEMS and that in addition to a decrease in the number of AZ VGCCs, disruption in the organization of AZ proteins, a reduction in AZ number, a reduction in the amount of synaptotagmin, and the compensatory expression of L-type channels outside the remaining AZs are important contributors to LEMS-mediated effects on transmitter release. Furthermore, our models predict that antibody-mediated removal of synaptotagmin in combination with disruption in AZ organization alone could mimic LEMS effects without the removal of VGCCs (a seronegative model). Overall, our results suggest that LEMS pathophysiology may be caused by a collection of pathological alterations to AZs at the NMJ, rather than by a simple loss of VGCCs.NEW & NOTEWORTHY We used a computational model of the active zone (AZ) in the mammalian neuromuscular junction to investigate Lambert-Eaton myasthenic syndrome (LEMS) pathophysiology. This model suggests that disruptions in presynaptic active zone organization and protein content (particularly synaptotagmin), beyond the simple removal of presynaptic calcium channels, play an important role in LEMS pathophysiology.
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Affiliation(s)
- Scott P Ginebaugh
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yomna Badawi
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Rozita Laghaei
- Biomedical Application Group, Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
| | - Glenn Mersky
- Biomedical Application Group, Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
| | - Caleb J Wallace
- Biomedical Application Group, Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
| | - Tyler B Tarr
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Cassandra Kaufhold
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Stephen Reddel
- Department of Clinical Neurology, Concord Hospital, Sydney, New South Wales, Australia
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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Lückemeyer DD, Prudente AS, de Amorim Ferreira M, da Silva AM, Tonello R, Junior SJM, do Prado CSH, de Castro Júnior CJ, Gomez MV, Calixto JB, Ferreira J. Critical Pronociceptive Role of Family 2 Voltage-Gated Calcium Channels in a Novel Mouse Model of HIV-Associated Sensory Neuropathy. Mol Neurobiol 2023; 60:2954-2968. [PMID: 36754911 DOI: 10.1007/s12035-023-03244-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 01/13/2023] [Indexed: 02/10/2023]
Abstract
Some people living with HIV present painful sensory neuropathy (HIV-SN) that is pharmacoresistant, sex-associated, and a major source of morbidity. Since the specific mechanisms underlying HIV-SN are not well understood, the aim of our study was to characterize a novel model of painful HIV-SN by combining the HIV-1 gp120 protein and the antiretroviral stavudine (d4T) in mice and to investigate the pronociceptive role of the family 2 voltage-gated calcium channel (VGCC) α1 subunit (Cav2.X channels) in such a model. HIV-SN was induced in male and female C57BL/6 mice by administration of gp120 and/or d4T and detected by a battery of behavior tests and by immunohistochemistry. The role of Cav2.X channels was assessed by the treatment with selective blockers and agonists as well as by mRNA detection. Repeated administration with gp120 and/or d4T produced long-lasting touch-evoked painful-like behaviors (starting at 6 days, reaching a maximum on day 13, and lasting up to 28 days after treatment started), with a greater intensity in female mice treated with the combination of gp120 + d4T. Moreover, gp120 + d4T treatment reduced the intraepidermal nerve fibers and well-being of female mice, without altering other behaviors. Mechanistically, gp120 + d4T treatment induced Cav2.1, 2.2, and 2.3 transcriptional increases in the dorsal root ganglion and the Cav2.X agonist-induced nociception. Accordingly, intrathecal selective Cav2.2 blockade presented longer and better efficacy in reversing the hyperalgesia induced by gp120 + d4T treatment compared with Cav2.1 or Cav2.3, but also presented the worst safety (inducing side effects at effective doses). We conclude that the family 2 calcium channels (Cav2.X) exert a critical pronociceptive role in a novel mouse model of HIV-SN.
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Affiliation(s)
- Debora Denardin Lückemeyer
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Arthur Silveira Prudente
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Marcella de Amorim Ferreira
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Ana Merian da Silva
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Raquel Tonello
- Department of Anesthesiology, Pain Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Sérgio José Macedo Junior
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
- Centro de Inovação E Ensaios Pré-Clínicos, Florianópolis, SC, Brazil
| | | | | | - Marcus Vinicius Gomez
- Instituto de Educação E Pesquisa da Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brazil
| | | | - Juliano Ferreira
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
- Departamento de Farmacologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
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Ginebaugh SP, Badawi Y, Tarr TB, Meriney SD. Neuromuscular Active Zone Structure and Function in Healthy and Lambert-Eaton Myasthenic Syndrome States. Biomolecules 2022; 12:biom12060740. [PMID: 35740866 PMCID: PMC9221282 DOI: 10.3390/biom12060740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/16/2022] [Accepted: 05/18/2022] [Indexed: 12/02/2022] Open
Abstract
The mouse neuromuscular junction (NMJ) has long been used as a model synapse for the study of neurotransmission in both healthy and disease states of the NMJ. Neurotransmission from these neuromuscular nerve terminals occurs at highly organized structures called active zones (AZs). Within AZs, the relationships between the voltage-gated calcium channels and docked synaptic vesicles govern the probability of acetylcholine release during single action potentials, and the short-term plasticity characteristics during short, high frequency trains of action potentials. Understanding these relationships is important not only for healthy synapses, but also to better understand the pathophysiology of neuromuscular diseases. In particular, we are interested in Lambert-Eaton myasthenic syndrome (LEMS), an autoimmune disorder in which neurotransmitter release from the NMJ decreases, leading to severe muscle weakness. In LEMS, the reduced neurotransmission is traditionally thought to be caused by the antibody-mediated removal of presynaptic voltage-gated calcium channels. However, recent experimental data and AZ computer simulations have predicted that a disruption in the normally highly organized active zone structure, and perhaps autoantibodies to other presynaptic proteins, contribute significantly to pathological effects in the active zone and the characteristics of chemical transmitters.
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Cho HY, Chen PC, Chuang TH, Yu MC, Wu SN. Activation of Voltage-Gated Na+ Current by GV-58, a Known Activator of CaV Channels. Biomedicines 2022; 10:biomedicines10030721. [PMID: 35327523 PMCID: PMC8945347 DOI: 10.3390/biomedicines10030721] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/10/2022] [Accepted: 03/17/2022] [Indexed: 02/04/2023] Open
Abstract
GV-58 ((2R)-2-[(6-{[(5-methylthiophen-2-yl)methyl]amino}-9-propyl-9H-purin-2-yl)amino]butan-1-ol) is recognized to be an activator of N- and P/Q-type Ca2+ currents. However, its modulatory actions on other types of ionic currents in electrically excitable cells remain largely unanswered. This study was undertaken to explore the possible modifications caused by GV-58 in ionic currents (e.g., voltage-gated Na+ current [INa], A-type K+ current [IK(A)], and erg-mediated K+ current [IK(erg)]) identified from pituitary GH3 lactotrophs. GH3 cell exposure to GV-58 enhanced the transient and late components of INa with varying potencies; consequently, the EC50 values of GV-58 required for its differential increase in peak and late INa in GH3 cells were estimated to be 8.9 and 2.6 μM, respectively. The INa in response to brief depolarizing pulse was respectively stimulated or suppressed by GV-58 or tetrodotoxin, but it failed to be altered by ω-conotoxin MVIID. Cell exposure to this compound increased the recovery of INa inactivation evoked by two-pulse protocol based on a geometrics progression; however, in its presence, there was a slowing in the inactivation rate of current decay evoked by a train of depolarizing pulses. The existence of GV-58 also resulted in an increase in the amplitude of ramp-induced resurgent and window INa. The presence of this compound inhibited IK(A) magnitude, accompanied by a shortening in inactivation time course of the current; however, it mildly decreased IK(erg). Under current-clamp conditions, GV-58 increased the frequency of spontaneous action potentials in GH3 cells. Moreover, in NSC-34 motor neuron-like cells, the presence of GV-58 not only raised INa amplitude but also reduced current inactivation. Taken together, the overall work provides a noticeable yet unidentified finding which implies that, in addition to its agonistic effect on Ca2+ currents, GV-58 may concertedly modify the amplitude and gating kinetics of INa in electrically excitable cells, hence modifiying functional activities in these cells.
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Affiliation(s)
- Hsin-Yen Cho
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Pei-Chun Chen
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City 70101, Taiwan
| | - Tzu-Hsien Chuang
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Meng-Cheng Yu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City 70101, Taiwan
- Correspondence: ; Tel.: +886-6-2353535-5334; Fax: +886-6-2362780
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Jablonka S, Hennlein L, Sendtner M. Therapy development for spinal muscular atrophy: perspectives for muscular dystrophies and neurodegenerative disorders. Neurol Res Pract 2022; 4:2. [PMID: 34983696 PMCID: PMC8725368 DOI: 10.1186/s42466-021-00162-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/21/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Major efforts have been made in the last decade to develop and improve therapies for proximal spinal muscular atrophy (SMA). The introduction of Nusinersen/Spinraza™ as an antisense oligonucleotide therapy, Onasemnogene abeparvovec/Zolgensma™ as an AAV9-based gene therapy and Risdiplam/Evrysdi™ as a small molecule modifier of pre-mRNA splicing have set new standards for interference with neurodegeneration. MAIN BODY Therapies for SMA are designed to interfere with the cellular basis of the disease by modifying pre-mRNA splicing and enhancing expression of the Survival Motor Neuron (SMN) protein, which is only expressed at low levels in this disorder. The corresponding strategies also can be applied to other disease mechanisms caused by loss of function or toxic gain of function mutations. The development of therapies for SMA was based on the use of cell culture systems and mouse models, as well as innovative clinical trials that included readouts that had originally been introduced and optimized in preclinical studies. This is summarized in the first part of this review. The second part discusses current developments and perspectives for amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease, as well as the obstacles that need to be overcome to introduce RNA-based therapies and gene therapies for these disorders. CONCLUSION RNA-based therapies offer chances for therapy development of complex neurodegenerative disorders such as amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease. The experiences made with these new drugs for SMA, and also the experiences in AAV gene therapies could help to broaden the spectrum of current approaches to interfere with pathophysiological mechanisms in neurodegeneration.
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Affiliation(s)
- Sibylle Jablonka
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany.
| | - Luisa Hennlein
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany.
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Using induced pluripotent stem cells to investigate human neuronal phenotypes in 1q21.1 deletion and duplication syndrome. Mol Psychiatry 2022; 27:819-830. [PMID: 34112971 PMCID: PMC9054650 DOI: 10.1038/s41380-021-01182-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 05/17/2021] [Accepted: 05/27/2021] [Indexed: 01/08/2023]
Abstract
Copy Number Variation (CNV) at the 1q21.1 locus is associated with a range of neurodevelopmental and psychiatric disorders in humans, including abnormalities in head size and motor deficits. Yet, the functional consequences of these CNVs (both deletion and duplication) on neuronal development remain unknown. To determine the impact of CNV at the 1q21.1 locus on neuronal development, we generated induced pluripotent stem cells from individuals harbouring 1q21.1 deletion or duplication and differentiated them into functional cortical neurons. We show that neurons with 1q21.1 deletion or duplication display reciprocal phenotype with respect to proliferation, differentiation potential, neuronal maturation, synaptic density and functional activity. Deletion of the 1q21.1 locus was also associated with an increased expression of lower cortical layer markers. This difference was conserved in the mouse model of 1q21.1 deletion, which displayed altered corticogenesis. Importantly, we show that neurons with 1q21.1 deletion and duplication are associated with differential expression of calcium channels and demonstrate that physiological deficits in neurons with 1q21.1 deletion or duplication can be pharmacologically modulated by targeting Ca2+ channel activity. These findings provide biological insight into the neuropathological mechanism underlying 1q21.1 associated brain disorder and indicate a potential target for therapeutic interventions.
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9
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Villarroel-Campos D, Schiavo G, Sleigh JN. Dissection, in vivo imaging and analysis of the mouse epitrochleoanconeus muscle. J Anat 2021; 241:1108-1119. [PMID: 34121181 PMCID: PMC9558155 DOI: 10.1111/joa.13478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/07/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
Analysis of rodent muscles affords an opportunity to glean key insights into neuromuscular development and the detrimental impact of disease‐causing genetic mutations. Muscles of the distal leg, for instance the gastrocnemius and tibialis anterior, are commonly used in such studies with mice and rats. However, thin and flat muscles, which can be dissected, processed and imaged without major disruption to muscle fibres and nerve‐muscle contacts, are more suitable for accurate and detailed analyses of the peripheral motor nervous system. One such wholemount muscle is the predominantly fast twitch epitrochleoanconeus (ETA), which is located in the upper forelimb, innervated by the radial nerve, and contains relatively large and uniformly flat neuromuscular junctions (NMJs). To facilitate incorporation of the ETA into the experimental toolkit of the neuromuscular disease field, here, we describe a simple method for its rapid isolation (<5 min), supported by high‐resolution videos and step‐by‐step images. Furthermore, we outline how the ETA can be imaged in live, anaesthetised mice, to enable examination of dynamic cellular processes occurring at the NMJ and within intramuscular axons, including transport of organelles, such as mitochondria and signalling endosomes. Finally, we present reference data on wild‐type ETA fibre‐type composition in young adult, male C57BL6/J mice. Comparative neuroanatomical studies of different muscles in rodent models of disease can generate critical insights into pathogenesis and pathology; dissection of the wholemount ETA provides the possibility to diversify the repertoire of muscles analysed for this endeavour.
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Affiliation(s)
- David Villarroel-Campos
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Giampietro Schiavo
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| | - James N Sleigh
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
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In Search of a Cure: The Development of Therapeutics to Alter the Progression of Spinal Muscular Atrophy. Brain Sci 2021; 11:brainsci11020194. [PMID: 33562482 PMCID: PMC7915832 DOI: 10.3390/brainsci11020194] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/19/2022] Open
Abstract
Until the recent development of disease-modifying therapeutics, spinal muscular atrophy (SMA) was considered a devastating neuromuscular disease with a poor prognosis for most affected individuals. Symptoms generally present during early childhood and manifest as muscle weakness and progressive paralysis, severely compromising the affected individual’s quality of life, independence, and lifespan. SMA is most commonly caused by the inheritance of homozygously deleted SMN1 alleles with retention of one or more copies of a paralog gene, SMN2, which inversely correlates with disease severity. The recent advent and use of genetically targeted therapies have transformed SMA into a prototype for monogenic disease treatment in the era of genetic medicine. Many SMA-affected individuals receiving these therapies achieve traditionally unobtainable motor milestones and survival rates as medicines drastically alter the natural progression of this disease. This review discusses historical SMA progression and underlying disease mechanisms, highlights advances made in therapeutic research, clinical trials, and FDA-approved medicines, and discusses possible second-generation and complementary medicines as well as optimal temporal intervention windows in order to optimize motor function and improve quality of life for all SMA-affected individuals.
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11
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Ojala KS, Ginebaugh SP, Wu M, Miller EW, Ortiz G, Covarrubias M, Meriney SD. A high-affinity, partial antagonist effect of 3,4-diaminopyridine mediates action potential broadening and enhancement of transmitter release at NMJs. J Biol Chem 2021; 296:100302. [PMID: 33465376 PMCID: PMC7949096 DOI: 10.1016/j.jbc.2021.100302] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 12/03/2022] Open
Abstract
3,4-Diaminopyridine (3,4-DAP) increases transmitter release from neuromuscular junctions (NMJs), and low doses of 3,4-DAP (estimated to reach ∼1 μM in serum) are the Food and Drug Administration (FDA)-approved treatment for neuromuscular weakness caused by Lambert–Eaton myasthenic syndrome. Canonically, 3,4-DAP is thought to block voltage-gated potassium (Kv) channels, resulting in prolongation of the presynaptic action potential (AP). However, recent reports have shown that low millimolar concentrations of 3,4-DAP have an off-target agonist effect on the Cav1 subtype (“L-type”) of voltage-gated calcium (Cav) channels and have speculated that this agonist effect might contribute to 3,4-DAP effects on transmitter release at the NMJ. To address 3,4-DAP’s mechanism(s) of action, we first used the patch-clamp electrophysiology to characterize the concentration-dependent block of 3,4-DAP on the predominant presynaptic Kv channel subtypes found at the mammalian NMJ (Kv3.3 and Kv3.4). We identified a previously unreported high-affinity (1–10 μM) partial antagonist effect of 3,4-DAP in addition to the well-known low-affinity (0.1–1 mM) antagonist activity. We also showed that 1.5-μM DAP had no effects on Cav1.2 or Cav2.1 current. Next, we used voltage imaging to show that 1.5- or 100-μM 3,4-DAP broadened the AP waveform in a dose-dependent manner, independent of Cav1 calcium channels. Finally, we demonstrated that 1.5- or 100-μM 3,4-DAP augmented transmitter release in a dose-dependent manner and this effect was also independent of Cav1 channels. From these results, we conclude that low micromolar concentrations of 3,4-DAP act solely on Kv channels to mediate AP broadening and enhance transmitter release at the NMJ.
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Affiliation(s)
- Kristine S Ojala
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Scott P Ginebaugh
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Man Wu
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Evan W Miller
- Departments of Chemistry and Molecular & Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Gloria Ortiz
- Departments of Chemistry and Molecular & Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Manuel Covarrubias
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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12
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Phillips MB, Nigam A, Johnson JW. Interplay between Gating and Block of Ligand-Gated Ion Channels. Brain Sci 2020; 10:brainsci10120928. [PMID: 33271923 PMCID: PMC7760600 DOI: 10.3390/brainsci10120928] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/21/2020] [Accepted: 11/26/2020] [Indexed: 02/03/2023] Open
Abstract
Drugs that inhibit ion channel function by binding in the channel and preventing current flow, known as channel blockers, can be used as powerful tools for analysis of channel properties. Channel blockers are used to probe both the sophisticated structure and basic biophysical properties of ion channels. Gating, the mechanism that controls the opening and closing of ion channels, can be profoundly influenced by channel blocking drugs. Channel block and gating are reciprocally connected; gating controls access of channel blockers to their binding sites, and channel-blocking drugs can have profound and diverse effects on the rates of gating transitions and on the stability of channel open and closed states. This review synthesizes knowledge of the inherent intertwining of block and gating of excitatory ligand-gated ion channels, with a focus on the utility of channel blockers as analytic probes of ionotropic glutamate receptor channel function.
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Affiliation(s)
- Matthew B. Phillips
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Aparna Nigam
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
| | - Jon W. Johnson
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
- Correspondence: ; Tel.: +1-(412)-624-4295
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13
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Rare CACNA1A mutations leading to congenital ataxia. Pflugers Arch 2020; 472:791-809. [DOI: 10.1007/s00424-020-02396-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/05/2020] [Accepted: 05/06/2020] [Indexed: 01/03/2023]
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14
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Satake S, Konishi S. Roscovitine differentially facilitates cerebellar glutamatergic and GABAergic neurotransmission by enhancing Ca v 2.1 channel-mediated multivesicular release. Eur J Neurosci 2020; 52:3002-3021. [PMID: 32383214 DOI: 10.1111/ejn.14771] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Revised: 04/22/2020] [Accepted: 05/01/2020] [Indexed: 11/29/2022]
Abstract
Synaptic vesicle exocytosis is triggered by Ca2+ influx through several subtypes of voltage-gated calcium channels in the presynaptic terminal. We previously reported that paired-pulse stimulation at brief intervals increases Cav 2.1 (P/Q-type) channel-mediated multivesicular release (MVR) at glutamatergic synapses between granule cells (GCs) and molecular layer interneurons (MLIs) in rat cerebellar slices. However, it has yet to be determined how Cav 2 channel subtypes take part in MVR in single axon terminal. This study therefore aimed at examining the effects of roscovitine on different types of cerebellar synapses that make contacts with Purkinje cells (PCs), because this compound has been shown to enhance Cav 2.1 channel-mediated MVR at GC-MLI synapses. Bath application of roscovitine profoundly increased the amplitude of excitatory postsynaptic currents (EPSCs) at GC-PC synapses by a presynaptic mechanism as previously observed at GC-MLI synapses, whereas it caused a marginal effect on climbing fiber-mediated EPSCs in PCs. At MLI-PC synapses, roscovitine increased both the amplitude and decay time of inhibitory postsynaptic currents (IPSCs) by enhancing multivesicular GABA release. When extracellular Ca2+ concentration ([Ca2+ ]e ) decreased, roscovitine became less effective in increasing GC-PC EPSCs. By contrast, roscovitine was able to augment MLI-PC IPSCs in the low [Ca2+ ]e . The Cav 2.1 channel blocker ω-agatoxin IVA suppressed the roscovitine-induced facilitatory actions on both GC-PC EPSCs and MLI-PC IPSCs. These results demonstrate that roscovitine enhances MVR at the GC-PC excitatory synapses in a manner dependent on the driving force of Cav 2.1 channel-mediated Ca2+ influx into the nerve terminal, while it also facilitates MLI-PC inhibitory transmission via Ca2+ -insensitive mechanisms.
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Affiliation(s)
- Shin'Ichiro Satake
- Department of Fundamental Neuroscience, National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan
| | - Shiro Konishi
- Department of Neurophysiology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Japan
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15
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The Frog Motor Nerve Terminal Has Very Brief Action Potentials and Three Electrical Regions Predicted to Differentially Control Transmitter Release. J Neurosci 2020; 40:3504-3516. [PMID: 32265260 DOI: 10.1523/jneurosci.2415-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 03/02/2020] [Accepted: 03/09/2020] [Indexed: 11/21/2022] Open
Abstract
The action potential (AP) waveform controls the opening of voltage-gated calcium channels and contributes to the driving force for calcium ion flux that triggers neurotransmission at presynaptic nerve terminals. Although the frog neuromuscular junction (NMJ) has long been a model synapse for the study of neurotransmission, its presynaptic AP waveform has never been directly studied, and thus the AP waveform shape and propagation through this long presynaptic nerve terminal are unknown. Using a fast voltage-sensitive dye, we have imaged the AP waveform from the presynaptic terminal of male and female frog NMJs and shown that the AP is very brief in duration and actively propagated along the entire length of the terminal. Furthermore, based on measured AP waveforms at different regions along the length of the nerve terminal, we show that the terminal is divided into three distinct electrical regions: A beginning region immediately after the last node of Ranvier where the AP is broadest, a middle region with a relatively consistent AP duration, and an end region near the tip of nerve terminal branches where the AP is briefer. We hypothesize that these measured changes in the AP waveform along the length of the motor nerve terminal may explain the proximal-distal gradient in transmitter release previously reported at the frog NMJ.SIGNIFICANCE STATEMENT The AP waveform plays an essential role in determining the behavior of neurotransmission at the presynaptic terminal. Although the frog NMJ is a model synapse for the study of synaptic transmission, there are many unknowns centered around the shape and propagation of its presynaptic AP waveform. Here, we demonstrate that the presynaptic terminal of the frog NMJ has a very brief AP waveform and that the motor nerve terminal contains three distinct electrical regions. We propose that the changes in the AP waveform as it propagates along the terminal can explain the proximal-distal gradient in transmitter release seen in electrophysiological studies.
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16
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Tyagi S, Ribera AB, Bannister RA. Zebrafish as a Model System for the Study of Severe Ca V2.1 (α 1A) Channelopathies. Front Mol Neurosci 2020; 12:329. [PMID: 32116539 PMCID: PMC7018710 DOI: 10.3389/fnmol.2019.00329] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 12/23/2019] [Indexed: 02/02/2023] Open
Abstract
The P/Q-type CaV2.1 channel regulates neurotransmitter release at neuromuscular junctions (NMJ) and many central synapses. CACNA1A encodes the pore-containing α1A subunit of CaV2.1 channels. In humans, de novo CACNA1A mutations result in a wide spectrum of neurological, neuromuscular, and movement disorders, such as familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2), as well as a more recently discovered class of more severe disorders, which are characterized by ataxia, hypotonia, cerebellar atrophy, and cognitive/developmental delay. Heterologous expression of CaV2.1 channels has allowed for an understanding of the consequences of CACNA1A missense mutations on channel function. In contrast, a mechanistic understanding of how specific CACNA1A mutations lead in vivo to the resultant phenotypes is lacking. In this review, we present the zebrafish as a model to both study in vivo mechanisms of CACNA1A mutations that result in synaptic and behavioral defects and to screen for effective drug therapies to combat these and other CaV2.1 channelopathies.
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Affiliation(s)
- Sidharth Tyagi
- Medical Scientist Training Program, Yale University School of Medicine, New Haven, CT, United States
| | - Angeles B Ribera
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, United States
| | - Roger A Bannister
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, United States.,Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
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17
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Tejero R, Balk S, Franco-Espin J, Ojeda J, Hennlein L, Drexl H, Dombert B, Clausen JD, Torres-Benito L, Saal-Bauernschubert L, Blum R, Briese M, Appenzeller S, Tabares L, Jablonka S. R-Roscovitine Improves Motoneuron Function in Mouse Models for Spinal Muscular Atrophy. iScience 2020; 23:100826. [PMID: 31981925 PMCID: PMC6992996 DOI: 10.1016/j.isci.2020.100826] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 08/08/2019] [Accepted: 01/06/2020] [Indexed: 12/27/2022] Open
Abstract
Neurotransmission defects and motoneuron degeneration are hallmarks of spinal muscular atrophy, a monogenetic disease caused by the deficiency of the SMN protein. In the present study, we show that systemic application of R-Roscovitine, a Cav2.1/Cav2.2 channel modifier and a cyclin-dependent kinase 5 (Cdk-5) inhibitor, significantly improved survival of SMA mice. In addition, R-Roscovitine increased Cav2.1 channel density and sizes of the motor endplates. In vitro, R-Roscovitine restored axon lengths and growth cone sizes of Smn-deficient motoneurons corresponding to enhanced spontaneous Ca2+ influx and elevated Cav2.2 channel cluster formations independent of its capability to inhibit Cdk-5. Acute application of R-Roscovitine at the neuromuscular junction significantly increased evoked neurotransmitter release, increased the frequency of spontaneous miniature potentials, and lowered the activation threshold of silent terminals. These data indicate that R-Roscovitine improves Ca2+ signaling and Ca2+ homeostasis in Smn-deficient motoneurons, which is generally crucial for motoneuron differentiation, maturation, and function. R-Roscovitine prolongs survival of SMA mice R-Roscovitine increases Ca2+ influx and growth cone size of SMA motoneurons R-Roscovitine beneficially affects neurotransmission in SMA motor nerve terminals R-Roscovitine wakes up dormant synapses of SMA motoneurons
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Affiliation(s)
- Rocio Tejero
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Stefanie Balk
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Julio Franco-Espin
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Jorge Ojeda
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | - Luisa Hennlein
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Hans Drexl
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Benjamin Dombert
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Jan-Dierk Clausen
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Laura Torres-Benito
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain
| | | | - Robert Blum
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Michael Briese
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany
| | - Silke Appenzeller
- Comprehensive Cancer Center Mainfranken, University Hospital Würzburg, 97080 Würzburg, Germany; Core Unit SysMed, University of Würzburg, 97080 Würzburg, Germany
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, 41009 Seville, Spain.
| | - Sibylle Jablonka
- Institute of Clinical Neurobiology, University Hospital Würzburg, 97078 Würzburg, Germany.
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18
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Abstract
Introduction: The present status of amifampridine (AFP) for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) is reviewed. Areas covered: All relevant literature identified through a PubMed search under treatment of LEMS, aminopyridine, and amifampridine are reviewed. An expert opinion on AFP was formulated. Expert opinion: AFPs, 3,4-DAP and 3,4-DAPP, are the most studied drugs in neuromuscular diseases. Randomized and non-randomized studies showed the most effective drug as symptomatic medication for LEMS. AFPs are safe and tolerable. Thus, AFPs should be the drug of choice for the symptomatic treatment in LEMS. As long as the daily dose is less than 80 mg a day, there is no concern for the serious side-reaction, seizure. Because of short-acting drug effects, it should be given three or four times a day. Peri-oral and finger paresthesia, the most common side-reaction, is accepted as a sign of drug-intake by many patients. Gastro-intestinal side reactions, the next common side-reaction of AFPs, are tolerable. AFPs are also the drug of choice and life-saving for LEMS crisis. For the long-term usage, it is proven to be safe and AFPs can be supplemented with liberal amount of pyridostigmine to sustain a symptomatic improvement without any undue side-reaction.
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Affiliation(s)
- Shin J Oh
- Department of Neurology, University of Alabama , Birmingham , AL , USA
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19
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Tyagi S, Bendrick TR, Filipova D, Papadopoulos S, Bannister RA. A mutation in Ca V2.1 linked to a severe neurodevelopmental disorder impairs channel gating. J Gen Physiol 2019; 151:850-859. [PMID: 31015257 PMCID: PMC6571999 DOI: 10.1085/jgp.201812237] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 02/04/2019] [Accepted: 03/18/2019] [Indexed: 01/07/2023] Open
Abstract
Ca2+ flux into axon terminals via P-/Q-type CaV2.1 channels is the trigger for neurotransmitter vesicle release at neuromuscular junctions (NMJs) and many central synapses. Recently, an arginine to proline substitution (R1673P) in the S4 voltage-sensing helix of the fourth membrane-bound repeat of CaV2.1 was linked to a severe neurological disorder characterized by generalized hypotonia, ataxia, cerebellar atrophy, and global developmental delay. The R1673P mutation was proposed to cause a gain of function in CaV2.1 leading to neuronal Ca2+ toxicity based on the ability of the mutant channel to rescue the photoreceptor response in CaV2.1-deficient Drosophila cacophony larvae. Here, we show that the corresponding mutation in rat CaV2.1 (R1624P) causes a profound loss of channel function; voltage-clamp analysis of tsA-201 cells expressing this mutant channel revealed an ∼25-mV depolarizing shift in the voltage dependence of activation. This alteration in activation implies that a significant fraction of CaV2.1 channels resident in presynaptic terminals are unlikely to open in response to an action potential, thereby increasing the probability of synaptic failure at both NMJs and central synapses. Indeed, the mutant channel supported only minimal Ca2+ flux in response to an action potential-like waveform. Application of GV-58, a compound previously shown to stabilize the open state of wild-type CaV2.1 channels, partially restored Ca2+ current by shifting mutant activation to more hyperpolarizing potentials and slowing deactivation. Consequently, GV-58 also rescued a portion of Ca2+ flux during action potential-like stimuli. Thus, our data raise the possibility that therapeutic agents that increase channel open probability or prolong action potential duration may be effective in combatting this and other severe neurodevelopmental disorders caused by loss-of-function mutations in CaV2.1.
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Affiliation(s)
- Sidharth Tyagi
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, Aurora, CO
| | - Tyler R Bendrick
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, Aurora, CO
| | - Dilyana Filipova
- Department of Vegetative Physiology, University of Cologne, Cologne, Germany
| | - Symeon Papadopoulos
- Department of Vegetative Physiology, University of Cologne, Cologne, Germany
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, Aurora, CO
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20
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El-Badry YAM, Sallam MS, El-Hashash MAA. Efficient 1,3,4-Thiadiazole-4,5-dihydropyridazin-3(2H)-ones as Antimicrobial Agents. Chem Pharm Bull (Tokyo) 2018; 66:427-433. [PMID: 29607908 DOI: 10.1248/cpb.c17-00918] [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] [Indexed: 11/22/2022]
Abstract
A set of novel series of 1,3,4-thiadiazolyl-sulfanyl-4,5-dihydropyridazin-3(2H)-ones with anticipated antimicrobial activity has been synthesized. The synthetic protocol of the targeted compounds was accomplished by treating β-aroylacrylic acid 1 with 5-amino-1,3,4-thiadiazole-2-thiol (2) to afford the thia-Michael adduct 3. Afterwards, the obtained thia-Michael adduct 3 was cyclized to 4,5-dihydropyridazin-3(2H)-ones 4a-d and the non-cyclized product hydrazone 5 by using different hydrazines. Moreover, adduct 3 was reacted with esters like diethyl malonate and ethyl acetoacetate affording 1,3,4-thiadiazolobutanamides 6a, b. Furthermore, the concurrent reaction of later butamides 6a, b with the hydrazine derivatives furnished thiadiazolopyridazin-3(2H)-ones 7a-d, 8, and butanoic acid 9.
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Affiliation(s)
- Yaser Abdel-Moemen El-Badry
- Organic Chemistry Lab., Faculty of Specific Education, Ain Shams University.,Organic Chemistry Dep., Faculty of Science, Taif University
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21
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Dittrich M, Homan AE, Meriney SD. Presynaptic mechanisms controlling calcium-triggered transmitter release at the neuromuscular junction. CURRENT OPINION IN PHYSIOLOGY 2018; 4:15-24. [PMID: 30272045 DOI: 10.1016/j.cophys.2018.03.004] [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] [Indexed: 12/11/2022]
Abstract
Calcium-triggered neurotransmission underlies most communication in the nervous system. Yet, despite the conserved and essential nature of this process, the molecular underpinnings of calcium-triggered neurotransmission have been difficult to study directly and our understanding to this date remains incomplete. Here we frame more recent efforts to understand this process with a historical perspective of the study of neurotransmitter release at the neuromuscular junction. We focus on the role of calcium channel distribution and organization relative to synaptic vesicles, as well as the nature of the calcium sensors that trigger release. Importantly, we provide a framework for understanding how the function of neurotransmitter release sites, or active zones, contributes to the function of the synapse as a whole.
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Affiliation(s)
| | - Anne E Homan
- Department of Neuroscience, A210 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260
| | - Stephen D Meriney
- Department of Neuroscience, A210 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260
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22
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Laghaei R, Ma J, Tarr TB, Homan AE, Kelly L, Tilvawala MS, Vuocolo BS, Rajasekaran HP, Meriney SD, Dittrich M. Transmitter release site organization can predict synaptic function at the neuromuscular junction. J Neurophysiol 2017; 119:1340-1355. [PMID: 29357458 DOI: 10.1152/jn.00168.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We have investigated the impact of transmitter release site (active zone; AZ) structure on synaptic function by physically rearranging the individual AZ elements in a previously published frog neuromuscular junction (NMJ) AZ model into the organization observed in a mouse NMJ AZ. We have used this strategy, purposefully without changing the properties of AZ elements between frog and mouse models (even though there are undoubtedly differences between frog and mouse AZ elements in vivo), to directly test how structure influences function at the level of an AZ. Despite a similarly ordered ion channel array substructure within both frog and mouse AZs, frog AZs are much longer and position docked vesicles in a different location relative to AZ ion channels. Physiologically, frog AZs have a lower probability of transmitter release compared with mouse AZs, and frog NMJs facilitate strongly during short stimulus trains in contrast with mouse NMJs that depress slightly. Using our computer modeling approach, we found that a simple rearrangement of the AZ building blocks of the frog model into a mouse AZ organization could recapitulate the physiological differences between these two synapses. These results highlight the importance of simple AZ protein organization to synaptic function. NEW & NOTEWORTHY A simple rearrangement of the basic building blocks in the frog neuromuscular junction model into a mouse transmitter release site configuration predicted the major physiological differences between these two synapses, suggesting that transmitter release site structure and organization is a strong predictor of function.
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Affiliation(s)
- Rozita Laghaei
- Biomedical Applications Group, Pittsburgh Supercomputing Center, Carnegie Mellon University , Pittsburgh, Pennsylvania
| | - Jun Ma
- Biomedical Applications Group, Pittsburgh Supercomputing Center, Carnegie Mellon University , Pittsburgh, Pennsylvania
| | - Tyler B Tarr
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Anne E Homan
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Lauren Kelly
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Megha S Tilvawala
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Blake S Vuocolo
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Harini P Rajasekaran
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Markus Dittrich
- Biomedical Applications Group, Pittsburgh Supercomputing Center, Carnegie Mellon University , Pittsburgh, Pennsylvania.,Department of Neuroscience, Center for Neuroscience, University of Pittsburgh , Pittsburgh, Pennsylvania.,BioTeam Inc., Middleton , Massachusetts
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23
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Wu M, White HV, Boehm BA, Meriney CJ, Kerrigan K, Frasso M, Liang M, Gotway EM, Wilcox MR, Johnson JW, Wipf P, Meriney SD. New Cav2 calcium channel gating modifiers with agonist activity and therapeutic potential to treat neuromuscular disease. Neuropharmacology 2017; 131:176-189. [PMID: 29246857 DOI: 10.1016/j.neuropharm.2017.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 11/28/2017] [Accepted: 12/10/2017] [Indexed: 12/13/2022]
Abstract
Voltage-gated calcium channels (VGCCs) are critical regulators of many cellular functions, including the activity-dependent release of chemical neurotransmitter from nerve terminals. At nerve terminals, the Cav2 family of VGCCs are closely positioned with neurotransmitter-containing synaptic vesicles. The relationship between calcium ions and transmitter release is such that even subtle changes in calcium flux through VGCCs have a strong influence on the magnitude of transmitter released. Therefore, modulators of the calcium influx at nerve terminals have the potential to strongly affect transmitter release at synapses. We have previously developed novel Cav2-selective VGCC gating modifiers (notably GV-58) that slow the deactivation of VGCC current, increasing total calcium ion flux. Here, we describe ten new gating modifiers based on the GV-58 structure that extend our understanding of the structure-activity relationship for this class of molecules and extend the range of modulation of channel activities. In particular, we show that one of these new compounds (MF-06) was more efficacious than GV-58, another (KK-75) acts more quickly on VGCCs than GV-58, and a third (KK-20) has a mix of increased speed and efficacy. A subset of these new VGCC agonist gating modifiers can increase transmitter release during action potentials at neuromuscular synapses, and as such, show potential as therapeutics for diseases with a presynaptic deficit that results in neuromuscular weakness. Further, several of these new compounds can be useful tool compounds for the study of VGCC gating and function.
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Affiliation(s)
- Man Wu
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Hayley V White
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Blake A Boehm
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Christopher J Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Kaylan Kerrigan
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Michael Frasso
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Erika M Gotway
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Madeleine R Wilcox
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Jon W Johnson
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States.
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24
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Use-dependent potentiation of voltage-gated calcium channels rescues neurotransmission in nerve terminals intoxicated by botulinum neurotoxin serotype A. Sci Rep 2017; 7:15862. [PMID: 29158500 PMCID: PMC5696531 DOI: 10.1038/s41598-017-16064-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 11/06/2017] [Indexed: 01/27/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are highly potent toxins that cleave neuronal SNARE proteins required for neurotransmission, causing flaccid paralysis and death by asphyxiation. Currently, there are no clinical treatments to delay or reverse BoNT-induced blockade of neuromuscular transmission. While aminopyridines have demonstrated varying efficacy in transiently reducing paralysis following BoNT poisoning, the precise mechanisms by which aminopyridines symptomatically treat botulism are not understood. Here we found that activity-dependent potentiation of presynaptic voltage-gated calcium channels (VGCCs) underlies 3,4-diaminopyridine (3,4-DAP)-mediated rescue of neurotransmission in central nervous system synapses and mouse diaphragm neuromuscular junctions fully intoxicated by BoNT serotype A. Combinatorial treatments with 3,4-DAP and VGCC agonists proved synergistic in restoring suprathreshold endplate potentials in mouse diaphragms fully intoxicated by BoNT/A. In contrast, synapses fully intoxicated by BoNT serotypes D or E were refractory to synaptic rescue by any treatment. We interpret these data to propose that increasing the duration or extent of VGCC activation prolongs the opportunity for low-efficiency fusion by fusogenic complexes incorporating BoNT/A-cleaved SNAP-25. The identification of VGCC agonists that rescue neurotransmission in BoNT/A-intoxicated synapses provides compelling evidence for potential therapeutic utility in some cases of human botulism.
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Meriney SD, Tarr TB, Ojala KS, Wu M, Li Y, Lacomis D, Garcia-Ocaña A, Liang M, Valdomir G, Wipf P. Lambert-Eaton myasthenic syndrome: mouse passive-transfer model illuminates disease pathology and facilitates testing therapeutic leads. Ann N Y Acad Sci 2017; 1412:73-81. [PMID: 29125190 DOI: 10.1111/nyas.13512] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 08/31/2017] [Accepted: 09/09/2017] [Indexed: 11/29/2022]
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder caused by antibodies directed against the voltage-gated calcium channels that provide the calcium ion flux that triggers acetylcholine release at the neuromuscular junction. To study the pathophysiology of LEMS and test candidate therapeutic strategies, a passive-transfer animal model has been developed in mice, which can be created by daily intraperitoneal injections of LEMS patient serum or IgG into mice for 2-4 weeks. Results from studies of the mouse neuromuscular junction have revealed that each synapse has hundreds of transmitter release sites but that the probability for release at each one is likely to be low. LEMS further reduces this low probability such that transmission is no longer effective at triggering a muscle contraction. The LEMS-mediated attack reduces the number of presynaptic calcium channels, disorganizes transmitter release sites, and results in the homeostatic upregulation of other calcium channel types. Symptomatic treatment is focused on increasing the probability of release from dysfunctional release sites. Current treatment uses the potassium channel blocker 3,4-diaminopyridine (DAP) to broaden the presynaptic action potential, providing more time for calcium channels to open. Current research is focused on testing new calcium channel gating modifiers that work synergistically with DAP.
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Affiliation(s)
- Stephen D Meriney
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Tyler B Tarr
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Kristine S Ojala
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Man Wu
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yizhi Li
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - David Lacomis
- Division of Neuromuscular Diseases, Departments of Neurology and Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Adolfo Garcia-Ocaña
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Guillermo Valdomir
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
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Beske PH, Bradford AB, Hoffman KM, Mason SJ, McNutt PM. In vitro and ex vivo screening of candidate therapeutics to restore neurotransmission in nerve terminals intoxicated by botulinum neurotoxin serotype A1. Toxicon 2017; 147:47-53. [PMID: 29054436 DOI: 10.1016/j.toxicon.2017.10.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/14/2017] [Accepted: 10/16/2017] [Indexed: 11/26/2022]
Abstract
Botulinum neurotoxins (BoNTs) are exceedingly potent neurological poisons that block cholinergic release in the peripheral nervous system and cause death by asphyxiation. While post-exposure prophylaxis can effectively eliminate toxin in the bloodstream, there are no clinically effective treatments to prevent or reverse disease once BoNT has entered the neuron. To address the need for post-symptomatic countermeasures, we designed and developed an in vitro assay based on whole-cell, patch-clamp electrophysiological monitoring of miniature excitatory post-synaptic currents in synaptically active murine embryonic stem cell-derived neurons. This synaptic function-based assay was used to assess the efficacy of rationally selected drugs to restore neurotransmission in neurons comprehensively intoxicated by BoNT/A. Based on clinical reports suggesting that elevated Ca2+ signaling promotes symptomatic relief from botulism, we identified seven candidate drugs that modulate presynaptic Ca2+ signaling and assessed their ability to reverse BoNT/A-induced synaptic blockade. The most effective drugs from the screen were found to phasically agonize voltage-gated calcium channel (VGCC) activity. Lead candidates were then applied to ex vivo studies in BoNT/A-paralyzing mouse phrenic nerve-hemidiaphragm (PND) preparations. Treatment of PNDs with VGCC agonists after paralytic onset transiently potentiated nerve-elicited muscle contraction and delayed progression to neuromuscular failure. Collectively, this study suggests that Ca2+-modulating drugs represent a novel symptomatic treatment for neuromuscular paralysis following BoNT/A poisoning.
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Affiliation(s)
- Phillip H Beske
- Department of Neuroscience, U.S. Army Medical Research Institute of Chemical Defense, Gunpowder, MD, 21010, USA
| | - Aaron B Bradford
- Department of Neuroscience, U.S. Army Medical Research Institute of Chemical Defense, Gunpowder, MD, 21010, USA
| | - Katie M Hoffman
- Department of Neuroscience, U.S. Army Medical Research Institute of Chemical Defense, Gunpowder, MD, 21010, USA
| | - Sydney J Mason
- Department of Neuroscience, U.S. Army Medical Research Institute of Chemical Defense, Gunpowder, MD, 21010, USA
| | - Patrick M McNutt
- Department of Neuroscience, U.S. Army Medical Research Institute of Chemical Defense, Gunpowder, MD, 21010, USA.
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Black BJ, Atmaramani R, Pancrazio JJ. Spontaneous and Evoked Activity from Murine Ventral Horn Cultures on Microelectrode Arrays. Front Cell Neurosci 2017; 11:304. [PMID: 29033792 PMCID: PMC5626830 DOI: 10.3389/fncel.2017.00304] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 09/12/2017] [Indexed: 12/11/2022] Open
Abstract
Motor neurons are the site of action for several neurological disorders and paralytic toxins, with cell bodies located in the ventral horn (VH) of the spinal cord along with interneurons and support cells. Microelectrode arrays (MEAs) have emerged as a high content assay platform for mechanistic studies and drug discovery. Here, we explored the spontaneous and evoked electrical activity of VH cultures derived from embryonic mouse spinal cord on multi-well plates of MEAs. Primary VH cultures from embryonic day 15–16 mice were characterized by expression of choline acetyltransferase (ChAT) by immunocytochemistry. Well resolved, all-or-nothing spontaneous spikes with profiles consistent with extracellular action potentials were observed after 3 days in vitro, persisting with consistent firing rates until at least day in vitro 19. The majority of the spontaneous activity consisted of tonic firing interspersed with coordinated bursting across the network. After 5 days in vitro, spike activity was readily evoked by voltage pulses where a minimum amplitude and duration required for excitation was 300 mV and 100 μs/phase, respectively. We characterized the sensitivity of spontaneous and evoked activity to a host of pharmacological agents including AP5, CNQX, strychnine, ω-agatoxin IVA, and botulinum neurotoxin serotype A (BoNT/A). These experiments revealed sensitivity of the cultured VH to both agonist and antagonist compounds in a manner consistent with mature tissue derived from slices. In the case of BoNT/A, we also demonstrated intoxication persistence over an 18-day period, followed by partial intoxication recovery induced by N- and P/Q-type calcium channel agonist GV-58. In total, our findings suggest that VH cultures on multi-well MEA plates may represent a moderate throughput, high content assay for performing mechanistic studies and for screening potential therapeutics pertaining to paralytic toxins and neurological disorders.
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Affiliation(s)
- Bryan J Black
- Neuronal Networks and Interfaces Laboratory, Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Rahul Atmaramani
- Neuronal Networks and Interfaces Laboratory, Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Joseph J Pancrazio
- Neuronal Networks and Interfaces Laboratory, Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
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El-Moselhy TF, Sidhom PA, Esmat EA, El-Mahdy NA. Synthesis, Docking Simulation, Biological Evaluations and 3D-QSAR Study of 1,4-Dihydropyridines as Calcium Channel Blockers. Chem Pharm Bull (Tokyo) 2017; 65:893-903. [DOI: 10.1248/cpb.c17-00186] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | - Peter Ayoub Sidhom
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Tanta University
| | - Eman Ahmed Esmat
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Tanta University
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Rogers RS, Nishimune H. The role of laminins in the organization and function of neuromuscular junctions. Matrix Biol 2016; 57-58:86-105. [PMID: 27614294 DOI: 10.1016/j.matbio.2016.08.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 08/10/2016] [Accepted: 08/17/2016] [Indexed: 01/11/2023]
Abstract
The synapse between motor neurons and skeletal muscle is known as the neuromuscular junction (NMJ). Proper alignment of presynaptic and post-synaptic structures of motor neurons and muscle fibers, respectively, is essential for efficient motor control of skeletal muscles. The synaptic cleft between these two cells is filled with basal lamina. Laminins are heterotrimer extracellular matrix molecules that are key members of the basal lamina. Laminin α4, α5, and β2 chains specifically localize to NMJs, and these laminin isoforms play a critical role in maintenance of NMJs and organization of synaptic vesicle release sites known as active zones. These individual laminin chains exert their role in organizing NMJs by binding to their receptors including integrins, dystroglycan, and voltage-gated calcium channels (VGCCs). Disruption of these laminins or the laminin-receptor interaction occurs in neuromuscular diseases including Pierson syndrome and Lambert-Eaton myasthenic syndrome (LEMS). Interventions to maintain proper level of laminins and their receptor interactions may be insightful in treating neuromuscular diseases and aging related degeneration of NMJs.
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Affiliation(s)
- Robert S Rogers
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
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Abstract
BACKGROUND Paraneoplastic syndromes that affect the visual pathways and present with neuro-ophthalmologic signs or symptoms may involve the afferent or efferent systems. Afferent syndromes may involve the optic nerve or retina and, in some cases, these may be associated with systemic neurologic disease. Efferent symptoms typically affect eye movements and may involve the neuromuscular junction or involuntary eye movements. EVIDENCE ACQUISITION Literature review and personal clinical and research experience. RESULTS Diagnosis of paraneoplastic syndromes relies on clinical and laboratory evaluations. In the appropriate clinical setting, the presence of specific antibodies may help confirm the diagnosis. CONCLUSIONS In some cases, the visual pathway disturbance precedes a diagnosis of malignancy. Astute observation and selective evaluation and management are critical to establish the correct diagnosis and institute therapeutic approaches that can be sight or life saving.
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Altered short-term synaptic plasticity and reduced muscle strength in mice with impaired regulation of presynaptic CaV2.1 Ca2+ channels. Proc Natl Acad Sci U S A 2016; 113:1068-73. [PMID: 26755585 DOI: 10.1073/pnas.1524650113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Facilitation and inactivation of P/Q-type calcium (Ca(2+)) currents through the regulation of voltage-gated Ca(2+) (CaV) 2.1 channels by Ca(2+) sensor (CaS) proteins contributes to the facilitation and rapid depression of synaptic transmission in cultured neurons that transiently express CaV2.1 channels. To examine the modulation of endogenous CaV2.1 channels by CaS proteins in native synapses, we introduced a mutation (IM-AA) into the CaS protein-binding site in the C-terminal domain of CaV2.1 channels in mice, and tested synaptic facilitation and depression in neuromuscular junction synapses that use exclusively CaV2.1 channels for Ca(2+) entry that triggers synaptic transmission. Even though basal synaptic transmission was unaltered in the neuromuscular synapses in IM-AA mice, we found reduced short-term facilitation in response to paired stimuli at short interstimulus intervals in IM-AA synapses. In response to trains of action potentials, we found increased facilitation at lower frequencies (10-30 Hz) in IM-AA synapses accompanied by slowed synaptic depression, whereas synaptic facilitation was reduced at high stimulus frequencies (50-100 Hz) that would induce strong muscle contraction. As a consequence of altered regulation of CaV2.1 channels, the hindlimb tibialis anterior muscle in IM-AA mice exhibited reduced peak force in response to 50 Hz stimulation and increased muscle fatigue. The IM-AA mice also had impaired motor control, exercise capacity, and grip strength. Taken together, our results indicate that regulation of CaV2.1 channels by CaS proteins is essential for normal synaptic plasticity at the neuromuscular junction and for muscle strength, endurance, and motor coordination in mice in vivo.
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Lambert–Eaton myasthenic syndrome – Diagnosis, pathogenesis and therapy. Clin Neurophysiol 2014; 125:2328-36. [DOI: 10.1016/j.clinph.2014.06.031] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 06/05/2014] [Accepted: 06/26/2014] [Indexed: 02/07/2023]
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Tarr TB, Wipf P, Meriney SD. Synaptic Pathophysiology and Treatment of Lambert-Eaton Myasthenic Syndrome. Mol Neurobiol 2014; 52:456-63. [PMID: 25195700 DOI: 10.1007/s12035-014-8887-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 08/29/2014] [Indexed: 12/12/2022]
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease that disrupts the normally reliable neurotransmission at the neuromuscular junction (NMJ). This disruption is thought to result from an autoantibody-mediated removal of a subset of the P/Q-type Ca(2+) channels involved with neurotransmitter release. With less neurotransmitter release at the NMJ, LEMS patients experience debilitating muscle weakness. The underlying cause of LEMS in slightly more than half of all patients is small cell lung cancer, and cancer therapy is the priority for these patients. In the remaining cases, the cause of LEMS is unknown, and these patients often rely on symptomatic treatment options, as there is no cure. However, current symptomatic treatment options, such as 3,4-diaminopyridine (3,4-DAP), can have significant dose-limiting side effects; thus, additional treatment approaches would benefit LEMS patients. Recent studies introduced a novel Ca(2+) channel agonist (GV-58) as a potential therapeutic alternative for LEMS. Additionally, this work has shown that GV-58 and 3,4-DAP interact in a supra-additive manner to completely restore the magnitude of neurotransmitter release at the NMJs of a LEMS mouse model. In this review, we discuss synaptic mechanisms for reliability at the NMJ and how these mechanisms are disrupted in LEMS. We then discuss the current treatment options for LEMS patients, while also considering recent work demonstrating the therapeutic potential of GV-58 alone and in combination with 3,4-DAP.
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Affiliation(s)
- Tyler B Tarr
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15260, USA
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Tarr TB, Lacomis D, Reddel SW, Liang M, Valdomir G, Frasso M, Wipf P, Meriney SD. Complete reversal of Lambert-Eaton myasthenic syndrome synaptic impairment by the combined use of a K+ channel blocker and a Ca2+ channel agonist. J Physiol 2014; 592:3687-96. [PMID: 25015919 DOI: 10.1113/jphysiol.2014.276493] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder in which a significant fraction of the presynaptic P/Q-type Ca(2+) channels critical to the triggering of neurotransmitter release at the neuromuscular junction (NMJ) are thought to be removed. There is no cure for LEMS, and the current most commonly used symptomatic treatment option is a potassium channel blocker [3,4-diaminopyridine (3,4-DAP)] that does not completely reverse symptoms and can have dose-limiting side-effects. We previously reported the development of a novel Ca(2+) channel agonist, GV-58, as a possible alternative treatment strategy for LEMS. In this study, we tested the hypothesis that the combination of GV-58 and 3,4-DAP will elicit a supra-additive increase in neurotransmitter release at LEMS model NMJs. First, we tested GV-58 in a cell survival assay to assess potential effects on cyclin-dependent kinases (Cdks) and showed that GV-58 did not affect cell survival at the relevant concentrations for Ca(2+) channel effects. Then, we examined the voltage dependence of GV-58 effects on Ca(2+) channels using patch clamp techniques; this showed the effects of GV-58 to be dependent upon Ca(2+) channel opening. Based on this mechanism, we predicted an interaction between 3,4-DAP and GV-58. We tested this hypothesis using a mouse passive transfer model of LEMS. Using intracellular electrophysiological ex vivo recordings, we demonstrated that a combined application of 3,4-DAP plus GV-58 had a supra-additive effect that completely reversed the deficit in neurotransmitter release magnitude at LEMS model NMJs. This reversal contrasts with the less significant improvement observed with either compound alone. Our data indicate that a combination of 3,4-DAP and GV-58 represents a promising treatment option for LEMS and potentially for other disorders of the NMJ.
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Affiliation(s)
- Tyler B Tarr
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, USA
| | - David Lacomis
- Division of Neuromuscular Diseases, Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA Department of Pathology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Stephen W Reddel
- Department of Clinical Neurology, Concord Hospital, Sydney, NSW, Australia
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA Center for Chemical Methodologies and Library Development, University of Pittsburgh, Pittsburgh, PA, USA
| | - Guillermo Valdomir
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA Center for Chemical Methodologies and Library Development, University of Pittsburgh, Pittsburgh, PA, USA
| | - Michael Frasso
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA Center for Chemical Methodologies and Library Development, University of Pittsburgh, Pittsburgh, PA, USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA Center for Chemical Methodologies and Library Development, University of Pittsburgh, Pittsburgh, PA, USA
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, USA
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van Sonderen A, Wirtz PW, Verschuuren JJGM, Titulaer MJ. Treatment options for Lambert–Eaton myasthenic syndrome. Expert Opin Orphan Drugs 2014. [DOI: 10.1517/21678707.2014.872559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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