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Rudrabhatla PK, Divya KP, Fasaludeen A, Menon RN, Cherian A, Urulangodi M, Sundaram S. Generalized Stiffness in Hereditary Hyperekplexia Responsive to Trihexyphenidyl: A Novel Finding. Clin Pediatr (Phila) 2024; 63:885-888. [PMID: 37899614 DOI: 10.1177/00099228231203300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/31/2023]
Affiliation(s)
- Pavan Kumar Rudrabhatla
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - K P Divya
- Comprehensive Care Centre for Movement Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Alfiya Fasaludeen
- Pediatric Neurology and Neurodevelopmental Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Ramshekhar N Menon
- Pediatric Neurology and Neurodevelopmental Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Ajith Cherian
- R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Madhusoodanan Urulangodi
- Department of Biochemistry, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Soumya Sundaram
- Pediatric Neurology and Neurodevelopmental Disorders, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
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Zhan FX, Wang SG, Cao L. Advances in hyperekplexia and other startle syndromes. Neurol Sci 2021; 42:4095-4107. [PMID: 34379238 DOI: 10.1007/s10072-021-05493-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/14/2021] [Indexed: 02/03/2023]
Abstract
Startle, a basic alerting reaction common to all mammals, is described as a sudden involuntary movement of the body evoked by all kinds of sudden and unexpected stimulus. Startle syndromes are heterogeneous groups of disorders with abnormal and exaggerated responses to startling events, including hyperekplexia, stimulus-induced disorders, and neuropsychiatric startle syndromes. Hyperekplexia can be attributed to a genetic, idiopathic, or symptomatic cause. Excluding secondary factors, hereditary hyperekplexia, a rare neurogenetic disorder with highly genetic heterogeneity, is characterized by neonatal hypertonia, exaggerated startle response provoked by the sudden external stimuli, and followed by a short period of general stiffness. It mainly arises from defects of inhibitory glycinergic neurotransmission. GLRA1 is the major pathogenic gene of hereditary hyperekplexia, along with many other genes involved in the function of glycinergic inhibitory synapses. While about 40% of patients remain negative genetic findings. Clonazepam, which can specifically upgrade the GABARA1 chloride channels, is the main and most effective administration for hereditary hyperekplexia patients. In this review, with the aim at enhancing the recognition and prompting potential treatment for hyperekplexia, we focused on discussing the advances in hereditary hyperekplexia genetics and the expound progress in pathogenic mechanisms of the glycinergic-synapse-related pathway and then followed by a brief overview of other common startle syndromes.
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Affiliation(s)
- Fei-Xia Zhan
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China
| | - Shi-Ge Wang
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China
| | - Li Cao
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China.
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Inhibition of Glycine Re-Uptake: A Potential Approach for Treating Pain by Augmenting Glycine-Mediated Spinal Neurotransmission and Blunting Central Nociceptive Signaling. Biomolecules 2021; 11:biom11060864. [PMID: 34200954 PMCID: PMC8230656 DOI: 10.3390/biom11060864] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022] Open
Abstract
Among the myriad of cellular and molecular processes identified as contributing to pathological pain, disinhibition of spinal cord nociceptive signaling to higher cortical centers plays a critical role. Importantly, evidence suggests that impaired glycinergic neurotransmission develops in the dorsal horn of the spinal cord in inflammatory and neuropathic pain models and is a key maladaptive mechanism causing mechanical hyperalgesia and allodynia. Thus, it has been hypothesized that pharmacological agents capable of augmenting glycinergic tone within the dorsal horn may be able to blunt or block aberrant nociceptor signaling to the brain and serve as a novel class of analgesics for various pathological pain states. Indeed, drugs that enhance dysfunctional glycinergic transmission, and in particular inhibitors of the glycine transporters (GlyT1 and GlyT2), are generating widespread interest as a potential class of novel analgesics. The GlyTs are Na+/Cl−-dependent transporters of the solute carrier 6 (SLC6) family and it has been proposed that the inhibition of them presents a possible mechanism by which to increase spinal extracellular glycine concentrations and enhance GlyR-mediated inhibitory neurotransmission in the dorsal horn. Various inhibitors of both GlyT1 and GlyT2 have demonstrated broad analgesic efficacy in several preclinical models of acute and chronic pain, providing promise for the approach to deliver a first-in-class non-opioid analgesic with a mechanism of action differentiated from current standard of care. This review will highlight the therapeutic potential of GlyT inhibitors as a novel class of analgesics, present recent advances reported for the field, and discuss the key challenges associated with the development of a GlyT inhibitor into a safe and effective agent to treat pain.
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Abstract
The inhibitory glycine receptor is a member of the Cys-loop superfamily of ligand-gated ion channels. It is the principal mediator of rapid synaptic inhibition in the spinal cord and brainstem and plays an important role in the modulation of higher brain functions including vision, hearing, and pain signaling. Glycine receptor function is controlled by only a few agonists, while the number of antagonists and positive or biphasic modulators is steadily increasing. These modulators are important for the study of receptor activation and regulation and have found clinical interest as potential analgesics and anticonvulsants. High-resolution structures of the receptor have become available recently, adding to our understanding of structure-function relationships and revealing agonistic, inhibitory, and modulatory sites on the receptor protein. This Review presents an overview of compounds that activate, inhibit, or modulate glycine receptor function in vitro and in vivo.
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Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo 11835, Egypt
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Wu Z, Lape R, Jopp-Saile L, O'Callaghan BJ, Greiner T, Sivilotti LG. The startle disease mutation α1S270T predicts shortening of glycinergic synaptic currents. J Physiol 2020; 598:3417-3438. [PMID: 32445491 PMCID: PMC7649747 DOI: 10.1113/jp279803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/19/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Loss-of-function mutations in proteins found at glycinergic synapses, most commonly in the α1 subunit of the glycine receptor (GlyR), cause the startle disease/hyperekplexia channelopathy in man. It was recently proposed that the receptors responsible are presynaptic homomeric GlyRs, rather than postsynaptic heteromeric GlyRs (which mediate glycinergic synaptic transmission), because heteromeric GlyRs are less affected by many startle mutations than homomers. We examined the α1 startle mutation S270T, at the extracellular end of the M2 transmembrane helix. Recombinant heteromeric GlyRs were less impaired than homomers by this mutation when we measured their response to equilibrium applications of glycine. However, currents elicited by synaptic-like millisecond applications of glycine to outside-out patches were much shorter (7- to 10-fold) in all mutant receptors, both homomeric and heteromeric. Thus, the synaptic function of heteromeric receptors is likely to be impaired by the mutation. ABSTRACT Human startle disease is caused by mutations in glycine receptor (GlyR) subunits or in other proteins associated with glycinergic synapses. Many startle mutations are known, but it is hard to correlate the degree of impairment at molecular level with the severity of symptoms in patients. It was recently proposed that the disease is caused by disruption in the function of presynaptic homomeric GlyRs (rather than postsynaptic heteromeric GlyRs), because homomeric GlyRs are more sensitive to loss-of-function mutations than heteromers. Our patch-clamp recordings from heterologously expressed GlyRs characterised in detail the functional consequences of the α1S270T startle mutation, which is located at the extracellular end of the pore lining M2 transmembrane segment (18'). This mutation profoundly decreased the maximum single-channel open probability of homomeric GlyRs (to 0.16; cf. 0.99 for wild type) but reduced only marginally that of heteromeric GlyRs (0.96; cf. 0.99 for wild type). However, both heteromeric and homomeric mutant GlyRs became less sensitive to the neurotransmitter glycine. Responses evoked by brief, quasi-synaptic pulses of glycine onto outside-out patches were impaired in mutant receptors, as deactivation was approximately 10- and 7-fold faster for homomeric and heteromeric GlyRs, respectively. Our data suggest that the α1S270T mutation is likely to affect the opening step in GlyR activation. The faster decay of synaptic currents mediated by mutant heteromeric GlyRs is expected to reduce charge transfer at the synapse, despite the high equilibrium open probability of these mutant channels.
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Affiliation(s)
- Zhiyi Wu
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Remigijus Lape
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Lea Jopp-Saile
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Benjamin J O'Callaghan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Timo Greiner
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Lucia G Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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Yahyaoui R, Pérez-Frías J. Amino Acid Transport Defects in Human Inherited Metabolic Disorders. Int J Mol Sci 2019; 21:ijms21010119. [PMID: 31878022 PMCID: PMC6981491 DOI: 10.3390/ijms21010119] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/12/2019] [Accepted: 12/18/2019] [Indexed: 02/07/2023] Open
Abstract
Amino acid transporters play very important roles in nutrient uptake, neurotransmitter recycling, protein synthesis, gene expression, cell redox balance, cell signaling, and regulation of cell volume. With regard to transporters that are closely connected to metabolism, amino acid transporter-associated diseases are linked to metabolic disorders, particularly when they involve different organs, cell types, or cell compartments. To date, 65 different human solute carrier (SLC) families and more than 400 transporter genes have been identified, including 11 that are known to include amino acid transporters. This review intends to summarize and update all the conditions in which a strong association has been found between an amino acid transporter and an inherited metabolic disorder. Many of these inherited disorders have been identified in recent years. In this work, the physiological functions of amino acid transporters will be described by the inherited diseases that arise from transporter impairment. The pathogenesis, clinical phenotype, laboratory findings, diagnosis, genetics, and treatment of these disorders are also briefly described. Appropriate clinical and diagnostic characterization of the underlying molecular defect may give patients the opportunity to avail themselves of appropriate therapeutic options in the future.
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Affiliation(s)
- Raquel Yahyaoui
- Laboratory of Metabolic Disorders and Newborn Screening Center of Eastern Andalusia, Málaga Regional University Hospital, 29011 Málaga, Spain
- Grupo Endocrinología y Nutrición, Diabetes y Obesidad, Instituto de Investigación Biomédica de Málaga-IBIMA, 29010 Málaga, Spain
- Correspondence:
| | - Javier Pérez-Frías
- Grupo Multidisciplinar de Investigación Pediátrica, Instituto de Investigación Biomédica de Málaga-IBIMA, 29010 Málaga, Spain;
- Departamento de Farmacología y Pediatría, Facultad de Medicina, Universidad de Málaga, 29010 Málaga, Spain
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Clinical features and genetic analysis of two siblings with startle disease in an Italian family: a case report. BMC MEDICAL GENETICS 2019; 20:40. [PMID: 30866851 PMCID: PMC6417078 DOI: 10.1186/s12881-019-0779-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 03/06/2019] [Indexed: 12/03/2022]
Abstract
Background Hyperekplexia also known as Startle disease is a rare neuromotor hereditary disorder characterized by exaggerated startle responses to unexpected auditory, tactile, and visual stimuli and generalized muscle stiffness, which both gradually subside during the first months of life. Although the diagnosis of Hyperekplexia is based on clinical findings, pathogenic variants in five genes have been reported to cause Hyperekplexia, of which GLRA1 accounts for about 80% of cases. Dominant and recessive mutations have been identified in GLRA1 gene as pathogenic variants in many individuals with the familial form of Hyperekplexia and occasionally in simplex cases. Case presentation In the present study, we describe clinical and genetic features of two Italian siblings, one with the major and one with the minor form of the disease. DNA samples from the probands and their parents were performed by NGS approach and validated by Sanger sequencing. The analysis of the GLRA1 gene revealed, in both probands, compound heterozygous mutations: c.895C > T or p.R299X inherited from the mother and c.587C > A or p.D98E inherited from the father. Conclusions Until now, these two identified mutations in GLRA1 have not been reported before as compound mutations. What clearly emerges within our study is the clinical heterogeneity in the same family. In fact, even though in the same pedigree, the affected mother showed only mild startle responses to unexpected noise stimuli, which might be explained by variable expressivity, while the father, showed no clear signs of symptomatology, which might be explained by non-penetrance. Finally, the two brothers have different form of the disease, even if the compound heterozygous mutations in GLRA1 are the same, showing that the same mutation in GLRA1 could have different phenotypic expressions and suggesting an underling mechanism of variable expressivity.
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Schaefer N, Zheng F, van Brederode J, Berger A, Leacock S, Hirata H, Paige CJ, Harvey RJ, Alzheimer C, Villmann C. Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease. Front Mol Neurosci 2018; 11:167. [PMID: 29910711 PMCID: PMC5992992 DOI: 10.3389/fnmol.2018.00167] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/02/2018] [Indexed: 11/25/2022] Open
Abstract
Mutations in GlyR α1 or β subunit genes in humans and rodents lead to severe startle disease characterized by rigidity, massive stiffness and excessive startle responses upon unexpected tactile or acoustic stimuli. The recently characterized startle disease mouse mutant shaky carries a missense mutation (Q177K) in the β8-β9 loop within the large extracellular N-terminal domain of the GlyR α1 subunit. This results in a disrupted hydrogen bond network around K177 and faster GlyR decay times. Symptoms in mice start at postnatal day 14 and increase until premature death of homozygous shaky mice around 4–6 weeks after birth. Here we investigate the in vivo functional effects of the Q177K mutation using behavioral analysis coupled to protein biochemistry and functional assays. Western blot analysis revealed GlyR α1 subunit expression in wild-type and shaky animals around postnatal day 7, a week before symptoms in mutant mice become obvious. Before 2 weeks of age, homozygous shaky mice appeared healthy and showed no changes in body weight. However, analysis of gait and hind-limb clasping revealed that motor coordination was already impaired. Motor coordination and the activity pattern at P28 improved significantly upon diazepam treatment, a pharmacotherapy used in human startle disease. To investigate whether functional deficits in glycinergic neurotransmission are present prior to phenotypic onset, we performed whole-cell recordings from hypoglossal motoneurons (HMs) in brain stem slices from wild-type and shaky mice at different postnatal stages. Shaky homozygotes showed a decline in mIPSC amplitude and frequency at P9-P13, progressing to significant reductions in mIPSC amplitude and decay time at P18-24 compared to wild-type littermates. Extrasynaptic GlyRs recorded by bath-application of glycine also revealed reduced current amplitudes in shaky mice compared to wild-type neurons, suggesting that presynaptic GlyR function is also impaired. Thus, a distinct, but behaviorally ineffective impairment of glycinergic synapses precedes the symptoms onset in shaky mice. These findings extend our current knowledge on startle disease in the shaky mouse model in that they demonstrate how the progression of GlyR dysfunction causes, with a delay of about 1 week, the appearance of disease symptoms.
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Affiliation(s)
- Natascha Schaefer
- Institute for Clinical Neurobiology, Julius-Maximilians-University of Würzburg, Würzburg, Germany
| | - Fang Zheng
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Johannes van Brederode
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Alexandra Berger
- Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Sophie Leacock
- Research Department of Pharmacology, UCL School of Pharmacy, London, United Kingdom
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, Japan
| | - Christopher J Paige
- Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Robert J Harvey
- School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD, Australia.,Sunshine Coast Health Institute, Birtinya, QLD, Australia
| | - Christian Alzheimer
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Carmen Villmann
- Institute for Clinical Neurobiology, Julius-Maximilians-University of Würzburg, Würzburg, Germany
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Cioffi CL. Modulation of Glycine-Mediated Spinal Neurotransmission for the Treatment of Chronic Pain. J Med Chem 2017; 61:2652-2679. [PMID: 28876062 DOI: 10.1021/acs.jmedchem.7b00956] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chronic pain constitutes a significant and expanding worldwide health crisis. Currently available analgesics poorly serve individuals suffering from chronic pain, and new therapeutic agents that are more effective, safer, and devoid of abuse liabilities are desperately needed. Among the myriad of cellular and molecular processes contributing to chronic pain, spinal disinhibition of pain signaling to higher cortical centers plays a critical role. Accumulating evidence shows that glycinergic inhibitory neurotransmission in the spinal cord dorsal horn gates nociceptive signaling, is essential in maintaining physiological pain sensitivity, and is diminished in pathological pain states. Thus, it is hypothesized that agents capable of enhancing glycinergic tone within the dorsal horn could obtund nociceptor signaling to the brain and serve as analgesics for persistent pain. This Perspective highlights the potential that pharmacotherapies capable of increasing inhibitory spinal glycinergic neurotransmission hold in providing new and transformative analgesic therapies for the treatment of chronic pain.
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Affiliation(s)
- Christopher L Cioffi
- Departments of Basic and Clinical Sciences and Pharmaceutical Sciences , Albany College of Pharmacy and Health Sciences , 106 New Scotland Avenue , Albany , New York 12208 United States
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Martinez-Hernandez E, Ariño H, McKeon A, Iizuka T, Titulaer MJ, Simabukuro MM, Lancaster E, Petit-Pedrol M, Planagumà J, Blanco Y, Harvey RJ, Saiz A, Graus F, Dalmau J. Clinical and Immunologic Investigations in Patients With Stiff-Person Spectrum Disorder. JAMA Neurol 2017; 73:714-20. [PMID: 27065452 DOI: 10.1001/jamaneurol.2016.0133] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
IMPORTANCE Symptoms of stiff-person syndrome (SPS), stiff-limb syndrome (SLS), or progressive encephalomyelitis with rigidity, myoclonus, or other symptoms (SPS-plus) can occur with several autoantibodies, but the relative frequency of each antibody, syndrome specificity, and prognostic implications are unclear. OBJECTIVE To report the clinical and immunologic findings of a large cohort of patients with stiff-person spectrum disorder (SPSD), including SPS, SLS, and SPS-plus. DESIGN, SETTING, AND PATIENTS This study retrospectively examined a case series (January 1, 1998, through December 31, 2014) of immunologic investigations performed in a neuroimmunology referral center. The study included 121 patients with clinical features of SPSD. Data analysis was performed from July 1, 2015, through November 1, 2015. MAIN OUTCOMES AND MEASURES Analysis of clinical-immunologic associations, including autoantibodies to 8 proteins expressed in inhibitory synapses. RESULTS The median age of the patients was 51 years (interquartile range, 40-61 years), and 75 (62.0%) were female. Fifty (41.3%) had SPS, 37 (30.6%) had SPS-plus, 24 (19.8%) had SLS, and 10 (8.3%) had SPS or SLS overlapping with ataxia, epilepsy, or encephalitis. Fifty-two patients (43.0%) had glutamic acid decarboxylase (GAD65) antibodies (2 with γ-aminobutyric acid-A [GABA-A] receptor antibodies), 24 (19.8%) had α1-subunit of the glycine receptor (GlyR) antibodies (2 with GAD65 antibodies), 5 (4.1%) had other antibodies, and 40 (33.1%) tested negative for antibodies. None had gephyrin or glycine transporter antibodies. Among the main immunologic groups (GAD65 antibodies, GlyR antibodies, and antibody negative), those with GAD65 antibodies were more likely to be female (45 [86.5%] of 52, 8 [36.4%] of 22, and 18 [45.0%] of 40, respectively; P < .001), have systemic autoimmunity (34 [65.4%] of 52, 7 [31.8%] of 22, and 13 [32.5%] of 40, respectively; P = .004), and have longer delays in being tested for antibodies (median, 3 vs 0.5 and 1 year; P < .001). Patients with GAD65 antibodies were more likely to develop SPS (27 [51.9%] of 52) or overlapping syndromes (8 [15.4%] of 52) than patients with GlyR antibodies (5 [22.7%] and 0 [0%] of 22, respectively), who more often developed SPS-plus (12 [54.5%] of 22 vs 7 [13.5%] in those with GAD65 antibodies); antibody-negative patients had an intermediate syndrome distribution. In multivariable analysis, symptom severity (P = .001) and immunologic group (P = .01) were independently associated with outcome. Compared with patients with GlyR antibodies, those with GAD65 antibodies (odds ratio, 11.1, 95% CI, 2.3-53.7; P = .003) had worse outcome. Patients without antibodies had similar outcome than patients with GlyR antibodies (odds ratio, 4.2, 95% CI, 0.9-20.0; P = .07). CONCLUSIONS AND RELEVANCE In SPSD, symptom severity and presence and type of antibodies are predictors of outcome.
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Affiliation(s)
- Eugenia Martinez-Hernandez
- Department of Neurology, Hospital Clínic, University of Barcelona, Barcelona, Spain2Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Helena Ariño
- Department of Neurology, Hospital Clínic, University of Barcelona, Barcelona, Spain2Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Andrew McKeon
- Departments of Neurology, Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Takahiro Iizuka
- Department of Neurology, Kitasato University School of Medicine, Sagamihara, Japan
| | - Maarten J Titulaer
- Department of Neurology, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Mateus M Simabukuro
- Neurology Division, Hospital das Clinicas, São Paulo University, São Paulo, Brazil
| | - Eric Lancaster
- Department of Neurology, University of Pennsylvania, Philadelphia
| | - Mar Petit-Pedrol
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Jesús Planagumà
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Yolanda Blanco
- Department of Neurology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Robert J Harvey
- Department of Pharmacology, UCL School of Pharmacy, London, England
| | - Albert Saiz
- Department of Neurology, Hospital Clínic, University of Barcelona, Barcelona, Spain2Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Francesc Graus
- Department of Neurology, Hospital Clínic, University of Barcelona, Barcelona, Spain2Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Josep Dalmau
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain7Department of Neurology, University of Pennsylvania, Philadelphia9Institució Catalana de Recerca i Estudis Avançats (ICREA), Catalonia, Spain
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The astrocytic transporter SLC7A10 (Asc-1) mediates glycinergic inhibition of spinal cord motor neurons. Sci Rep 2016; 6:35592. [PMID: 27759100 PMCID: PMC5069678 DOI: 10.1038/srep35592] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/03/2016] [Indexed: 12/27/2022] Open
Abstract
SLC7A10 (Asc-1) is a sodium-independent amino acid transporter known to facilitate transport of a number of amino acids including glycine, L-serine, L-alanine, and L-cysteine, as well as their D-enantiomers. It has been described as a neuronal transporter with a primary role related to modulation of excitatory glutamatergic neurotransmission. We find that SLC7A10 is substantially enriched in a subset of astrocytes of the caudal brain and spinal cord in a distribution corresponding with high densities of glycinergic inhibitory synapses. Accordingly, we find that spinal cord glycine levels are significantly reduced in Slc7a10-null mice and spontaneous glycinergic postsynaptic currents in motor neurons show substantially diminished amplitudes, demonstrating an essential role for SLC7A10 in glycinergic inhibitory function in the central nervous system. These observations establish the etiology of sustained myoclonus (sudden involuntary muscle movements) and early postnatal lethality characteristic of Slc7a10-null mice, and implicate SLC7A10 as a candidate gene and auto-antibody target in human hyperekplexia and stiff person syndrome, respectively.
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Ogino K, Hirata H. Defects of the Glycinergic Synapse in Zebrafish. Front Mol Neurosci 2016; 9:50. [PMID: 27445686 PMCID: PMC4925712 DOI: 10.3389/fnmol.2016.00050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022] Open
Abstract
Glycine mediates fast inhibitory synaptic transmission. Physiological importance of the glycinergic synapse is well established in the brainstem and the spinal cord. In humans, the loss of glycinergic function in the spinal cord and brainstem leads to hyperekplexia, which is characterized by an excess startle reflex to sudden acoustic or tactile stimulation. In addition, glycinergic synapses in this region are also involved in the regulation of respiration and locomotion, and in the nociceptive processing. The importance of the glycinergic synapse is conserved across vertebrate species. A teleost fish, the zebrafish, offers several advantages as a vertebrate model for research of glycinergic synapse. Mutagenesis screens in zebrafish have isolated two motor defective mutants that have pathogenic mutations in glycinergic synaptic transmission: bandoneon (beo) and shocked (sho). Beo mutants have a loss-of-function mutation of glycine receptor (GlyR) β-subunit b, alternatively, sho mutant is a glycinergic transporter 1 (GlyT1) defective mutant. These mutants are useful animal models for understanding of glycinergic synaptic transmission and for identification of novel therapeutic agents for human diseases arising from defect in glycinergic transmission, such as hyperekplexia or glycine encephalopathy. Recent advances in techniques for genome editing and for imaging and manipulating of a molecule or a physiological process make zebrafish more attractive model. In this review, we describe the glycinergic defective zebrafish mutants and the technical advances in both forward and reverse genetic approaches as well as in vivo visualization and manipulation approaches for the study of the glycinergic synapse in zebrafish.
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Affiliation(s)
- Kazutoyo Ogino
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
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Wilkins ME, Caley A, Gielen MC, Harvey RJ, Smart TG. Murine startle mutant Nmf11 affects the structural stability of the glycine receptor and increases deactivation. J Physiol 2016; 594:3589-607. [PMID: 27028707 PMCID: PMC4929309 DOI: 10.1113/jp272122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/21/2016] [Indexed: 11/10/2022] Open
Abstract
Key points Hyperekplexia or startle disease is a serious neurological condition affecting newborn children and usually involves dysfunctional glycinergic neurotransmission. Glycine receptors (GlyRs) are major mediators of inhibition in the spinal cord and brainstem. A missense mutation, replacing asparagine (N) with lysine (K), at position 46 in the GlyR α1 subunit induced hyperekplexia following a reduction in the potency of the transmitter glycine; this resulted from a rapid deactivation of the agonist current at mutant GlyRs. These effects of N46K were rescued by mutating a juxtaposed residue, N61 on binding Loop D, suggesting these two asparagines may interact. Asparagine 46 is considered to be important for the structural stability of the subunit interface and glycine binding site, and its mutation represents a new mechanism by which GlyR dysfunction induces startle disease.
Abstract Dysfunctional glycinergic inhibitory transmission underlies the debilitating neurological condition, hyperekplexia, which is characterised by exaggerated startle reflexes, muscle hypertonia and apnoea. Here we investigated the N46K missense mutation in the GlyR α1 subunit gene found in the ethylnitrosourea (ENU) murine mutant, Nmf11, which causes reduced body size, evoked tremor, seizures, muscle stiffness, and morbidity by postnatal day 21. Introducing the N46K mutation into recombinant GlyR α1 homomeric receptors, expressed in HEK cells, reduced the potencies of glycine, β‐alanine and taurine by 9‐, 6‐ and 3‐fold respectively, and that of the competitive antagonist strychnine by 15‐fold. Replacing N46 with hydrophobic, charged or polar residues revealed that the amide moiety of asparagine was crucial for GlyR activation. Co‐mutating N61, located on a neighbouring β loop to N46, rescued the wild‐type phenotype depending on the amino acid charge. Single‐channel recording identified that burst length for the N46K mutant was reduced and fast agonist application revealed faster glycine deactivation times for the N46K mutant compared with the WT receptor. Overall, these data are consistent with N46 ensuring correct alignment of the α1 subunit interface by interaction with juxtaposed residues to preserve the structural integrity of the glycine binding site. This represents a new mechanism by which GlyR dysfunction induces startle disease. Hyperekplexia or startle disease is a serious neurological condition affecting newborn children and usually involves dysfunctional glycinergic neurotransmission. Glycine receptors (GlyRs) are major mediators of inhibition in the spinal cord and brainstem. A missense mutation, replacing asparagine (N) with lysine (K), at position 46 in the GlyR α1 subunit induced hyperekplexia following a reduction in the potency of the transmitter glycine; this resulted from a rapid deactivation of the agonist current at mutant GlyRs. These effects of N46K were rescued by mutating a juxtaposed residue, N61 on binding Loop D, suggesting these two asparagines may interact. Asparagine 46 is considered to be important for the structural stability of the subunit interface and glycine binding site, and its mutation represents a new mechanism by which GlyR dysfunction induces startle disease.
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Affiliation(s)
- Megan E Wilkins
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Alex Caley
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Marc C Gielen
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Robert J Harvey
- Department of Pharmacology, UCL School of Pharmacy, 29-39, Brunswick Square, London, WC1N 1AX, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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Inhibition of miR-203 Reduces Spontaneous Recurrent Seizures in Mice. Mol Neurobiol 2016; 54:3300-3308. [PMID: 27165289 DOI: 10.1007/s12035-016-9901-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 05/03/2016] [Indexed: 01/03/2023]
Abstract
Inhibitory synaptic receptors are dysfunctional in epileptic brains, and agents that selectively target these receptors may be effective for the treatment of epilepsy. MicroRNAs interfere with the translation of target genes, including various synaptic proteins. Here, we show that miR-203 regulates glycine receptor-β (Glrb) in epilepsy models. miR-203 is upregulated in the hippocampus of epileptic mice and human epileptic brains and is predicted to target inhibitory synaptic receptors, including Glrb. In vitro transfection, target gene luciferase assays, and analysis of human samples confirmed the direct inhibition of GLRB by miR-203, and AM203, an antagomir targeting miR-203, reversed the effect of miR-203. When intranasal AM203 was administered, AM203 reached the brain and restored hippocampal GLRB levels in epileptic mice. Finally, intranasal AM203 reduced the epileptic seizure frequency of mice. Overall, this study suggests that GLRB expression in the epileptic brain is controlled by miR-203, and intranasal delivery of AM203 showed therapeutic effects in chronic epilepsy mice.
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15
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Eckle VS, Grasshoff C, Mirakaj V, O'Neill PM, Berry NG, Leuwer M, Antkowiak B. 4-bromopropofol decreases action potential generation in spinal neurons by inducing a glycine receptor-mediated tonic conductance. Br J Pharmacol 2015; 171:5790-801. [PMID: 25131750 DOI: 10.1111/bph.12880] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 07/29/2014] [Accepted: 08/11/2014] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Impaired function of spinal strychnine-sensitive glycine receptors gives rise to chronic pain states and movement disorders. Therefore, increased activity of glycine receptors should help to treat such disorders. Although compounds targeting glycine receptors with a high selectivity are lacking, halogenated analogues of propofol have recently been considered as potential candidates. Therefore we asked whether 4-bromopropofol attenuated the excitability of spinal neurons by promoting glycine receptor-dependent inhibition. EXPERIMENTAL APPROACH The actions of sub-anaesthetic concentrations of propofol and 4-bromopropofol were investigated in spinal tissue cultures prepared from mice. Drug-induced alterations in action potential firing were monitored by extracellular multi-unit recordings. The effects on GABAA and glycine receptor-mediated inhibition were quantified by whole-cell voltage-clamp recordings. KEY RESULTS Low concentrations of 4-bromopropofol (50 nM) reduced action potential activity of ventral horn neurons by about 30%, compared with sham-treated slices. This effect was completely abolished by strychnine (1 μM). In voltage-clamped neurons, 4-bromopropofol activated glycine receptors, generating a tonic current of 65 ± 10 pA, while GABAA - and glycine receptor-mediated synaptic transmission remained unaffected. CONCLUSIONS AND IMPLICATIONS The highest glycine levels in the CNS are found in the ventral horn of the spinal cord, a region mediating pain-induced motor reflexes and participating in the control of muscle tone. 4-Bromopropofol may serve as a starting point for the development of non-sedative, non-addictive, muscle relaxants and analgesics to be used to treat low back pain.
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Affiliation(s)
- V S Eckle
- Experimental Anaesthesiology Section, Department of Anaesthesiology and Intensive Care, Eberhard-Karls-University, Tübingen, Germany
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16
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Breitinger U, Raafat KM, Breitinger HG. Glucose is a positive modulator for the activation of human recombinant glycine receptors. J Neurochem 2015; 134:1055-66. [DOI: 10.1111/jnc.13215] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 06/15/2015] [Accepted: 06/16/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry; The German University in Cairo; New Cairo Egypt
| | - Karim M. Raafat
- Department of Biochemistry; The German University in Cairo; New Cairo Egypt
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17
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Allosteric and hyperekplexic mutant phenotypes investigated on an α1 glycine receptor transmembrane structure. Proc Natl Acad Sci U S A 2015; 112:2865-70. [PMID: 25730860 DOI: 10.1073/pnas.1417864112] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The glycine receptor (GlyR) is a pentameric ligand-gated ion channel (pLGIC) mediating inhibitory transmission in the nervous system. Its transmembrane domain (TMD) is the target of allosteric modulators such as general anesthetics and ethanol and is a major locus for hyperekplexic congenital mutations altering the allosteric transitions of activation or desensitization. We previously showed that the TMD of the human α1GlyR could be fused to the extracellular domain of GLIC, a bacterial pLGIC, to form a functional chimera called Lily. Here, we overexpress Lily in Schneider 2 insect cells and solve its structure by X-ray crystallography at 3.5 Å resolution. The TMD of the α1GlyR adopts a closed-channel conformation involving a single ring of hydrophobic residues at the center of the pore. Electrophysiological recordings show that the phenotypes of key allosteric mutations of the α1GlyR, scattered all along the pore, are qualitatively preserved in this chimera, including those that confer decreased sensitivity to agonists, constitutive activity, decreased activation kinetics, or increased desensitization kinetics. Combined structural and functional data indicate a pore-opening mechanism for the α1GlyR, suggesting a structural explanation for the effect of some key hyperekplexic allosteric mutations. The first X-ray structure of the TMD of the α1GlyR solved here using GLIC as a scaffold paves the way for mechanistic investigation and design of allosteric modulators of a human receptor.
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18
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Aguayo LG, Castro P, Mariqueo T, Muñoz B, Xiong W, Zhang L, Lovinger DM, Homanics GE. Altered sedative effects of ethanol in mice with α1 glycine receptor subunits that are insensitive to Gβγ modulation. Neuropsychopharmacology 2014; 39:2538-48. [PMID: 24801766 PMCID: PMC4207329 DOI: 10.1038/npp.2014.100] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 03/20/2014] [Accepted: 03/21/2014] [Indexed: 12/17/2022]
Abstract
Alcohol abuse and alcoholism are major health problems and one of the leading preventable causes of death. Before achieving better treatments for alcoholism, it is necessary to understand the critical actions of alcohol on membrane proteins that regulate fundamental functions in the central nervous system. After generating a genetically modified knock-in (KI) mouse having a glycine receptor (GlyR) with phenotypical silent mutations at KK385/386AA, we studied its cellular and in vivo ethanol sensitivity. Analyses with western blotting and immunocytochemistry indicated that the expression of α1 GlyRs in nervous tissues and spinal cord neurons (SCNs) were similar between WT and KI mice. The analysis of synaptic currents recorded from KI mice showed that the glycinergic synaptic transmission had normal properties, but the sensitivity to ethanol was significantly reduced. Furthermore, the glycine-evoked current in SCNs from KI was resistant to ethanol and G-protein activation by GTP-γ-S. In behavioral studies, KI mice did not display the foot-clasping behavior upon lifting by the tail and lacked an enhanced startle reflex response that are characteristic of other glycine KI mouse lines with markedly impaired glycine receptor function. The most notable characteristic of the KI mice was their significant lower sensitivity to ethanol (∼40%), expressed by shorter times in loss of righting reflex (LORR) in response to a sedative dose of ethanol (3.5 g/Kg). These data provide the first evidence to link a molecular site in the GlyR with the sedative effects produced by intoxicating doses of ethanol.
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Affiliation(s)
- Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile,Department of Physiology, University of Concepcion, PO BOX 160C, Concepcion 4030001, Chile. E-mail:
| | - Patricio Castro
- Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
| | - Trinidad Mariqueo
- Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
| | - Braulio Muñoz
- Laboratory of Neurophysiology, Department of Physiology, University of Concepcion, Concepcion, Chile
| | - Wei Xiong
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Li Zhang
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - David M Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Gregg E Homanics
- Departments of Anesthesiology and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA,Departments of Anesthesiology and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA. E-mail:
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19
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Dwyer DS, Aamodt E, Cohen B, Buttner EA. Drug elucidation: invertebrate genetics sheds new light on the molecular targets of CNS drugs. Front Pharmacol 2014; 5:177. [PMID: 25120487 PMCID: PMC4112795 DOI: 10.3389/fphar.2014.00177] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 07/09/2014] [Indexed: 02/02/2023] Open
Abstract
Many important drugs approved to treat common human diseases were discovered by serendipity, without a firm understanding of their modes of action. As a result, the side effects and interactions of these medications are often unpredictable, and there is limited guidance for improving the design of next-generation drugs. Here, we review the innovative use of simple model organisms, especially Caenorhabditis elegans, to gain fresh insights into the complex biological effects of approved CNS medications. Whereas drug discovery involves the identification of new drug targets and lead compounds/biologics, and drug development spans preclinical testing to FDA approval, drug elucidation refers to the process of understanding the mechanisms of action of marketed drugs by studying their novel effects in model organisms. Drug elucidation studies have revealed new pathways affected by antipsychotic drugs, e.g., the insulin signaling pathway, a trace amine receptor and a nicotinic acetylcholine receptor. Similarly, novel targets of antidepressant drugs and lithium have been identified in C. elegans, including lipid-binding/transport proteins and the SGK-1 signaling pathway, respectively. Elucidation of the mode of action of anesthetic agents has shown that anesthesia can involve mitochondrial targets, leak currents, and gap junctions. The general approach reviewed in this article has advanced our knowledge about important drugs for CNS disorders and can guide future drug discovery efforts.
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Affiliation(s)
- Donard S. Dwyer
- Department of Psychiatry–Department of Pharmacology, Toxicology and Neuroscience, Louisiana State University Health Sciences Center-ShreveportShreveport, LA, USA
| | - Eric Aamodt
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center-ShreveportShreveport, LA, USA
| | - Bruce Cohen
- Department of Psychiatry, Harvard Medical SchoolBoston, MA, USA
- Mailman Research Center, McLean HospitalBelmont, MA, USA
| | - Edgar A. Buttner
- Mailman Research Center, McLean HospitalBelmont, MA, USA
- Department of Neurology–Department of Psychiatry, McLean Hospital, Harvard Medical SchoolBelmont, MA, USA
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20
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Bode A, Lynch JW. The impact of human hyperekplexia mutations on glycine receptor structure and function. Mol Brain 2014; 7:2. [PMID: 24405574 PMCID: PMC3895786 DOI: 10.1186/1756-6606-7-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 01/07/2014] [Indexed: 01/11/2023] Open
Abstract
Hyperekplexia is a rare neurological disorder characterized by neonatal hypertonia, exaggerated startle responses to unexpected stimuli and a variable incidence of apnoea, intellectual disability and delays in speech acquisition. The majority of motor defects are successfully treated by clonazepam. Hyperekplexia is caused by hereditary mutations that disrupt the functioning of inhibitory glycinergic synapses in neuromotor pathways of the spinal cord and brainstem. The human glycine receptor α1 and β subunits, which predominate at these synapses, are the major targets of mutations. International genetic screening programs, that together have analysed several hundred probands, have recently generated a clear picture of genotype-phenotype correlations and the prevalence of different categories of hyperekplexia mutations. Focusing largely on this new information, this review seeks to summarise the effects of mutations on glycine receptor structure and function and how these functional alterations lead to hyperekplexia.
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Affiliation(s)
| | - Joseph W Lynch
- Queensland Brain Institute and School of Biomedical Sciences, The University of Queensland, Queensland 4072, Australia.
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21
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Presynaptic glycine receptors as a potential therapeutic target for hyperekplexia disease. Nat Neurosci 2014; 17:232-9. [PMID: 24390226 DOI: 10.1038/nn.3615] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 12/03/2013] [Indexed: 11/08/2022]
Abstract
Although postsynaptic glycine receptors (GlyRs) as αβ heteromers attract considerable research attention, little is known about the role of presynaptic GlyRs, likely α homomers, in diseases. Here, we demonstrate that dehydroxylcannabidiol (DH-CBD), a nonpsychoactive cannabinoid, can rescue GlyR functional deficiency and exaggerated acoustic and tactile startle responses in mice bearing point mutations in α1 GlyRs that are responsible for a hereditary startle-hyperekplexia disease. The GlyRs expressed as α1 homomers either in HEK-293 cells or at presynaptic terminals of the calyceal synapses in the auditory brainstem are more vulnerable than heteromers to hyperekplexia mutation-induced impairment. Homomeric mutants are more sensitive to DH-CBD than are heteromers, suggesting presynaptic GlyRs as a primary target. Consistent with this idea, DH-CBD selectively rescues impaired presynaptic GlyR activity and diminished glycine release in the brainstem and spinal cord of hyperekplexic mutant mice. Thus, presynaptic α1 GlyRs emerge as a potential therapeutic target for dominant hyperekplexia disease and other diseases with GlyR deficiency.
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22
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Bode A, Wood SE, Mullins JGL, Keramidas A, Cushion TD, Thomas RH, Pickrell WO, Drew CJG, Masri A, Jones EA, Vassallo G, Born AP, Alehan F, Aharoni S, Bannasch G, Bartsch M, Kara B, Krause A, Karam EG, Matta S, Jain V, Mandel H, Freilinger M, Graham GE, Hobson E, Chatfield S, Vincent-Delorme C, Rahme JE, Afawi Z, Berkovic SF, Howell OW, Vanbellinghen JF, Rees MI, Chung SK, Lynch JW. New hyperekplexia mutations provide insight into glycine receptor assembly, trafficking, and activation mechanisms. J Biol Chem 2013; 288:33745-33759. [PMID: 24108130 DOI: 10.1074/jbc.m113.509240] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperekplexia is a syndrome of readily provoked startle responses, alongside episodic and generalized hypertonia, that presents within the first month of life. Inhibitory glycine receptors are pentameric ligand-gated ion channels with a definitive and clinically well stratified linkage to hyperekplexia. Most hyperekplexia cases are caused by mutations in the α1 subunit of the human glycine receptor (hGlyR) gene (GLRA1). Here we analyzed 68 new unrelated hyperekplexia probands for GLRA1 mutations and identified 19 mutations, of which 9 were novel. Electrophysiological analysis demonstrated that the dominant mutations p.Q226E, p.V280M, and p.R414H induced spontaneous channel activity, indicating that this is a recurring mechanism in hGlyR pathophysiology. p.Q226E, at the top of TM1, most likely induced tonic activation via an enhanced electrostatic attraction to p.R271 at the top of TM2, suggesting a structural mechanism for channel activation. Receptors incorporating p.P230S (which is heterozygous with p.R65W) desensitized much faster than wild type receptors and represent a new TM1 site capable of modulating desensitization. The recessive mutations p.R72C, p.R218W, p.L291P, p.D388A, and p.E375X precluded cell surface expression unless co-expressed with α1 wild type subunits. The recessive p.E375X mutation resulted in subunit truncation upstream of the TM4 domain. Surprisingly, on the basis of three independent assays, we were able to infer that p.E375X truncated subunits are incorporated into functional hGlyRs together with unmutated α1 or α1 plus β subunits. These aberrant receptors exhibit significantly reduced glycine sensitivity. To our knowledge, this is the first suggestion that subunits lacking TM4 domains might be incorporated into functional pentameric ligand-gated ion channel receptors.
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Affiliation(s)
- Anna Bode
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia
| | - Sian-Elin Wood
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Jonathan G L Mullins
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Angelo Keramidas
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia
| | - Thomas D Cushion
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Rhys H Thomas
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - William O Pickrell
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Cheney J G Drew
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Amira Masri
- Department of Paediatrics, Division of Child Neurology, Faculty of Medicine, University of Jordan, Amman 11942, Jordan
| | - Elizabeth A Jones
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom; Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom
| | - Grace Vassallo
- Royal Manchester Children's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom
| | - Alfred P Born
- Department of Pediatrics, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark
| | - Fusun Alehan
- Department of Pediatrics, Division of Child Neurology, Faculty of Medicine, Basşkent University, 06990 Ankara, Turkey
| | - Sharon Aharoni
- Institute of Pediatric Neurology, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69987, Israel
| | - Gerald Bannasch
- Neurology Department, Affinity Medical Group, Menasha, Wisconsin 54952
| | - Marius Bartsch
- Department of Neonatology, University Medical Center of the Johannes Gutenberg University Mainz, D-55099 Mainz, Germany
| | - Bulent Kara
- Kocaeli University Medical Faculty, Department of Pediatrics, Division of Child Neurology, 41380 Kocaeli, Turkey
| | - Amanda Krause
- Division of Human Genetics, National Health Laboratory Service, and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 2000 Johannesburg, South Africa
| | - Elie G Karam
- Department of Psychiatry and Clinical Psychology, Saint George Hospital University Medical Center, Balamand University, Faculty of Medicine, Beirut 1100 2807, Lebanon
| | - Stephanie Matta
- Department of Psychiatry and Clinical Psychology, Saint George Hospital University Medical Center, Balamand University, Faculty of Medicine, Beirut 1100 2807, Lebanon
| | - Vivek Jain
- Royal Children's Hospital Melbourne, Children's Neuroscience Centre, Royal Children's Hospital, Victoria 3052, Australia
| | - Hanna Mandel
- Metabolic Unit, Meyer Children's Hospital, Rambam Medical Center, Technion Faculty of Medicine, Haifa 31096, Israel
| | - Michael Freilinger
- Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, 1090 Vienna, Austria
| | - Gail E Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Emma Hobson
- Yorkshire Regional Genetic Service, Chapel Allerton Hospital, Leeds, West Yorkshire LS9 7TF, United Kingdom
| | - Sue Chatfield
- Neonatal Unit, Bradford Royal Infirmary, Bradford, West Yorkshire BD9 6RJ, United Kingdom
| | | | | | - Zaid Afawi
- Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Samuel F Berkovic
- Epilepsy Research Centre, Melbourne Brain Centre, Austin Health, Heidelberg 3084, Victoria, Australia
| | - Owain W Howell
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | | | - Mark I Rees
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Seo-Kyung Chung
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Joseph W Lynch
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia.
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Abstract
Strychnine-sensitive glycine receptors (GlyRs) mediate synaptic inhibition in the spinal cord, brainstem, and other regions of the mammalian central nervous system. In this minireview, we summarize our current view of the structure, ligand-binding sites, and chloride channel of these receptors and discuss recently emerging functions of distinct GlyR isoforms. GlyRs not only regulate the excitability of motor and afferent sensory neurons, including pain fibers, but also are involved in the processing of visual and auditory signals. Hence, GlyRs constitute promising targets for the development of therapeutically useful compounds.
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Affiliation(s)
- Sébastien Dutertre
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Cord-Michael Becker
- the Institute of Biochemistry, University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Heinrich Betz
- the Max-Planck-Institute for Medical Research, 69120 Heidelberg, Germany, and
- the Department of Molecular Neurobiology, Max-Planck-Institute for Experimental Medicine, 37075 Göttingen, Germany
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24
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de la Roche J, Leuwer M, Krampfl K, Haeseler G, Dengler R, Buchholz V, Ahrens J. 4-Chloropropofol enhances chloride currents in human hyperekplexic and artificial mutated glycine receptors. BMC Neurol 2012; 12:104. [PMID: 23006332 PMCID: PMC3517478 DOI: 10.1186/1471-2377-12-104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 09/19/2012] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND The mammalian neurological disorder hereditary hyperekplexia can be attributed to various mutations of strychnine sensitive glycine receptors. The clinical symptoms of "startle disease" predominantly occur in the newborn leading to convulsive hypertonia and an exaggerated startle response to unexpected mild stimuli. Amongst others, point mutations R271Q and R271L in the α1-subunit of strychnine sensitive glycine receptors show reduced glycine sensitivity and cause the clinical symptoms of hyperekplexia.Halogenation has been shown to be a crucial structural determinant for the potency of a phenolic compound to positively modulate glycine receptor function.The aim of this in vitro study was to characterize the effects of 4-chloropropofol (4-chloro-2,6-dimethylphenol) at four glycine receptor mutations. METHODS Glycine receptor subunits were expressed in HEK 293 cells and experiments were performed using the whole-cell patch-clamp technique. RESULTS 4-chloropropofol exerted a positive allosteric modulatory effect in a low sub-nanomolar concentration range at the wild type receptor (EC50 value of 0.08 ± 0.02 nM) and in a micromolar concentration range at the mutations (1.3 ± 0.6 μM, 0.1 ± 0.2 μM, 6.0 ± 2.3 μM and 55 ± 28 μM for R271Q, L, K and S267I, respectively). CONCLUSIONS 4-chloropropofol might be an effective compound for the activation of mutated glycine receptors in experimental models of startle disease.
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Affiliation(s)
- Jeanne de la Roche
- Clinic for Anesthesia and Critical Care Medicine, OE 8050, Hannover Medical School, Carl-Neuberg-Str, 1, 30625, Hannover, Germany.
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Carta E, Chung SK, James VM, Robinson A, Gill JL, Remy N, Vanbellinghen JF, Drew CJG, Cagdas S, Cameron D, Cowan FM, Del Toro M, Graham GE, Manzur AY, Masri A, Rivera S, Scalais E, Shiang R, Sinclair K, Stuart CA, Tijssen MAJ, Wise G, Zuberi SM, Harvey K, Pearce BR, Topf M, Thomas RH, Supplisson S, Rees MI, Harvey RJ. Mutations in the GlyT2 gene (SLC6A5) are a second major cause of startle disease. J Biol Chem 2012; 287:28975-85. [PMID: 22700964 PMCID: PMC3436555 DOI: 10.1074/jbc.m112.372094] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/11/2012] [Indexed: 11/06/2022] Open
Abstract
Hereditary hyperekplexia or startle disease is characterized by an exaggerated startle response, evoked by tactile or auditory stimuli, leading to hypertonia and apnea episodes. Missense, nonsense, frameshift, splice site mutations, and large deletions in the human glycine receptor α1 subunit gene (GLRA1) are the major known cause of this disorder. However, mutations are also found in the genes encoding the glycine receptor β subunit (GLRB) and the presynaptic Na(+)/Cl(-)-dependent glycine transporter GlyT2 (SLC6A5). In this study, systematic DNA sequencing of SLC6A5 in 93 new unrelated human hyperekplexia patients revealed 20 sequence variants in 17 index cases presenting with homozygous or compound heterozygous recessive inheritance. Five apparently unrelated cases had the truncating mutation R439X. Genotype-phenotype analysis revealed a high rate of neonatal apneas and learning difficulties associated with SLC6A5 mutations. From the 20 SLC6A5 sequence variants, we investigated glycine uptake for 16 novel mutations, confirming that all were defective in glycine transport. Although the most common mechanism of disrupting GlyT2 function is protein truncation, new pathogenic mechanisms included splice site mutations and missense mutations affecting residues implicated in Cl(-) binding, conformational changes mediated by extracellular loop 4, and cation-π interactions. Detailed electrophysiology of mutation A275T revealed that this substitution results in a voltage-sensitive decrease in glycine transport caused by lower Na(+) affinity. This study firmly establishes the combination of missense, nonsense, frameshift, and splice site mutations in the GlyT2 gene as the second major cause of startle disease.
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Affiliation(s)
- Eloisa Carta
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Seo-Kyung Chung
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Victoria M. James
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Angela Robinson
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Jennifer L. Gill
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Nathalie Remy
- Human Genetics, Liège University Hospital, B-4000 Liège, Belgium
| | | | - Cheney J. G. Drew
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Sophie Cagdas
- Department of Child Neuropsychiatry, C Poma Hospital, 46100 Mantova, Italy
| | - Duncan Cameron
- Department of Paediatrics, Glan Clwyd Hospital, Rhyl LL18 5UJ, United Kingdom
| | - Frances M. Cowan
- Department of Paediatrics, Imperial College, London W12 0HS, United Kingdom
| | - Mireria Del Toro
- Servicio de Neurologia Pediatrica, Hospital General Universitari Vall d'Hebron, 08035 Barcelona, Spain
| | - Gail E. Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Adnan Y. Manzur
- Department of Paediatric Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom
| | - Amira Masri
- Department of Paediatrics, University of Jordan, 11941 Amman, Jordan
| | - Serge Rivera
- Service de Pédiatrie, Centre Hospitalier de la Côte Basque, 64109 Bayonne, France
| | - Emmanuel Scalais
- Neurologie Pédiatrique, Centre Hospitalier de Luxembourg, L-1210 Luxembourg
| | - Rita Shiang
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia 23298-0033
| | - Kate Sinclair
- Queensland Paediatric Rehabilitation Service, Royal Children's Hospital, Herston 4029, Australia
| | | | - Marina A. J. Tijssen
- Department of Neurology, University Medical Centre Groningen, 9713 GZ, Groningen, The Netherlands
| | - Grahame Wise
- Sydney Children's Hospital, Randwick NSW 2031, Australia
| | - Sameer M. Zuberi
- Paediatric Neurosciences Research Group, Royal Hospital for Sick Children, Glasgow G3 8SJ, United Kingdom
| | - Kirsten Harvey
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Brian R. Pearce
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London WC1E 7HX, United Kingdom
| | - Rhys H. Thomas
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
- Wales Epilepsy Research Network, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Stéphane Supplisson
- Institut de Biologie de l'Ecole Normale Supérieure, Paris 75000, France
- Institut National de la Santé et de la Recherche Médicale, U1024, Paris 75000, France, and
- CNRS, UMR 8197, Paris 75000, France
| | - Mark I. Rees
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
- Wales Epilepsy Research Network, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Robert J. Harvey
- Department of Pharmacology, UCL School of Pharmacy, London WC1N 1AX, United Kingdom
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Harvey RJ, Rigo JM. Glycinergic transmission: physiological, developmental and pathological implications. Front Mol Neurosci 2010; 3. [PMID: 20877421 PMCID: PMC2944627 DOI: 10.3389/fnmol.2010.00115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 08/03/2010] [Indexed: 11/28/2022] Open
Affiliation(s)
- Robert J Harvey
- Department of Pharmacology, The School of Pharmacy London, UK
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