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Ritzau-Jost A, Gsell F, Sell J, Sachs S, Montanaro J, Kirmann T, Maaß S, Irani SR, Werner C, Geis C, Sauer M, Shigemoto R, Hallermann S. LGI1 Autoantibodies Enhance Synaptic Transmission by Presynaptic K v1 Loss and Increased Action Potential Broadening. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2024; 11:e200284. [PMID: 39141878 PMCID: PMC11379440 DOI: 10.1212/nxi.0000000000200284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/16/2024]
Abstract
BACKGROUND AND OBJECTIVES Autoantibodies against the protein leucine-rich glioma inactivated 1 (LGI1) cause the most common subtype of autoimmune encephalitis with predominant involvement of the limbic system, associated with seizures and memory deficits. LGI1 and its receptor ADAM22 are part of a transsynaptic protein complex that includes several proteins involved in presynaptic neurotransmitter release and postsynaptic glutamate sensing. Autoantibodies against LGI1 increase excitatory synaptic strength, but studies that genetically disrupt the LGI1-ADAM22 complex report a reduction in postsynaptic glutamate receptor-mediated responses. Thus, the mechanisms underlying the increased synaptic strength induced by LGI1 autoantibodies remain elusive, and the contributions of presynaptic molecules to the LGI1-transsynaptic complex remain unclear. We therefore investigated the presynaptic mechanisms that mediate autoantibody-induced synaptic strengthening. METHODS We studied the effects of patient-derived purified polyclonal LGI1 autoantibodies on synaptic structure and function by combining direct patch-clamp recordings from presynaptic boutons and somata of hippocampal neurons with super-resolution light and electron microscopy of hippocampal cultures and brain slices. We also identified the protein domain mediating the presynaptic effect using domain-specific patient-derived monoclonal antibodies. RESULTS LGI1 autoantibodies dose-dependently increased short-term depression during high-frequency transmission, consistent with increased release probability. The increased neurotransmission was not related to presynaptic calcium channels because presynaptic Cav2.1 channel density, calcium current amplitude, and calcium channel gating were unaffected by LGI1 autoantibodies. By contrast, application of LGI1 autoantibodies homogeneously reduced Kv1.1 and Kv1.2 channel density on the surface of presynaptic boutons. Direct presynaptic patch-clamp recordings revealed that LGI1 autoantibodies cause a pronounced broadening of the presynaptic action potential. Domain-specific effects of LGI1 autoantibodies were analyzed at the neuronal soma. Somatic action potential broadening was induced by polyclonal LGI1 autoantibodies and patient-derived monoclonal autoantibodies targeting the epitempin domain, but not the leucin-rich repeat domain. DISCUSSION Our results indicate that LGI1 autoantibodies reduce the density of both Kv1.1 and Kv1.2 on presynaptic boutons, without actions on calcium channel density or function, thereby broadening the presynaptic action potential and increasing neurotransmitter release. This study provides a molecular explanation for the neuronal hyperactivity observed in patients with LGI1 autoantibodies.
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Affiliation(s)
- Andreas Ritzau-Jost
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Felix Gsell
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Josefine Sell
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Stefan Sachs
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Jacqueline Montanaro
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Toni Kirmann
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Sebastian Maaß
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Sarosh R Irani
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Christian Werner
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Christian Geis
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Markus Sauer
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Ryuichi Shigemoto
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
| | - Stefan Hallermann
- From the Carl-Ludwig-Institute of Physiology (A.R.-J., F.G., T.K., S.M., S.H.), Faculty of Medicine, Leipzig University; Section Translational Neuroimmunology (J.S., C.G.), Department of Neurology, Jena University Hospital; Department of Biotechnology and Biophysics (S.S., C.W., M.S.), University of Würzburg, Biocenter, Germany; Institute of Science and Technology Austria (ISTA) (J.M., R.S.), Klosterneuburg, Austria; Oxford Autoimmune Neurology Group (S.R.I.), Nuffield Department of Clinical Neurosciences, University of Oxford, ; Department of Neurology (S.R.I.), John Radcliffe Hospital, Oxford University Hospitals, United Kingdom; and Departments of Neurology and Neurosciences (S.R.I.), Mayo Clinic Jacksonville, FL
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Hasan SM, Aswad N, Al-Sabah S. A positively charged residue at the Kv1.1 T1 interface is critical for voltage-dependent activation and gating kinetics. Am J Physiol Cell Physiol 2024; 327:C790-C797. [PMID: 39099423 DOI: 10.1152/ajpcell.00422.2024] [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: 06/21/2024] [Revised: 07/17/2024] [Accepted: 07/18/2024] [Indexed: 08/06/2024]
Abstract
Within the tetramerization domain (T1) of most voltage-gated potassium channels (Kv) are highly conserved charged residues that line the T1-T1 interface. We investigated the Kv1.1 residue R86 located at the narrowest region of the T1 interface. A Kv1.1 R86Q mutation was reported in a child diagnosed with lower limb dyskinesia (Set KK, Ghosh D, Huq AHM, Luat AF. Mov Disord Clin Pract 4: 784-786, 2017). The child did not present with episodic ataxia 1 (EA1) symptoms typically associated with Kv1.1 loss-of-function mutations. We characterized the electrophysiological outcome of the R86Q substitution by expressing Kv1.1 in Xenopus laevis oocytes. Mutated α-subunits were able to form functional channels that pass delayed rectifier currents. Oocytes that expressed only mutated α-subunits produced a significant reduction in Kv1.1 current and showed a positive shift in voltage dependence of activation. In addition, there was substantially slower activation and faster deactivation implying a reduction in the time the channel is in its open state. Oocytes co-injected with both mutated and wild-type cRNA in equal amounts, to mimic the heterozygous condition of the disease, showed a decrease in current amplitude at -10 mV, a positive shift in activation voltage-dependence and faster deactivation kinetics when compared with the wild-type channel. These findings indicate that T1 plays a role in Kv1.1's voltage-dependent activation and in its kinetics of activation and deactivation.NEW & NOTEWORTHY This is the first Kv1.1 study to characterize the electrophysiological and structural phenotype of a tetramerization (T1) domain mutation. Surprisingly, the mutated α-subunits were able to tetramerize, albeit with different gating kinetics and voltage dependence. This novel finding points to a clear role of T1 in the channel's voltage dependence and gating. Mimicking the heterozygous condition resulted in milder alterations in channel function when compared with previously reported mutations. This is in agreement with the child's milder symptoms.
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Affiliation(s)
- Sonia Majed Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Nawal Aswad
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Suleiman Al-Sabah
- Department of Pharmacology & Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait
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Singh V, Auerbach DS. Neurocardiac pathologies associated with potassium channelopathies. Epilepsia 2024. [PMID: 39087855 DOI: 10.1111/epi.18066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 07/10/2024] [Accepted: 07/10/2024] [Indexed: 08/02/2024]
Abstract
Voltage-gated potassium channels are expressed throughout the human body and are essential for physiological functions. These include delayed rectifiers, A-type channels, outward rectifiers, and inward rectifiers. They impact electrical function in the heart (repolarization) and brain (repolarization and stabilization of the resting membrane potential). KCNQx and KCNHx encode Kv7.x and Kv11.x proteins, which form delayed rectifier potassium channels. KCNQx and KCNHx channelopathies are associated with both cardiac and neuronal pathologies. These include electrocardiographic abnormalities, cardiac arrhythmias, sudden cardiac death (SCD), epileptiform discharges, seizures, bipolar disorder, and sudden unexpected death in epilepsy (SUDEP). Due to the ubiquitous expression of KCNQx and KCNHx channels, abnormalities in their function can be particularly harmful, increasing the risk of sudden death. For example, KCNH2 variants have a dual role in both cardiac and neuronal pathologies, whereas KCNQ2 and KCNQ3 variants are associated with severe and refractory epilepsy. Recurrent and uncontrolled seizures lead to secondary abnormalities, which include autonomics, cardiac electrical function, respiratory drive, and neuronal electrical activity. Even with a wide array of anti-seizure therapies available on the market, one-third of the more than 70 million people worldwide with epilepsy have uncontrolled seizures (i.e., intractable/drug-resistant epilepsy), which negatively impact neurodevelopment and quality of life. To capture the current state of the field, this review examines KCNQx and KCNHx expression patterns and electrical function in the brain and heart. In addition, it discusses several KCNQx and KCNHx variants that have been clinically and electrophysiologically characterized. Because these channel variants are associated with multi-system pathologies, such as epileptogenesis, Kv7 channel modulators provide a potential anti-seizure therapy, particularly for people with intractable epilepsy. Ultimately an increased understanding of the role of Kv channels throughout the body will fuel the development of innovative, safe, and effective therapies for people at a high risk of sudden death (SCD and SUDEP).
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Affiliation(s)
- Veronica Singh
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - David S Auerbach
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York, USA
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Szanto TG, Papp F, Zakany F, Varga Z, Deutsch C, Panyi G. Molecular rearrangements in S6 during slow inactivation in Shaker-IR potassium channels. J Gen Physiol 2023; 155:e202313352. [PMID: 37212728 PMCID: PMC10202832 DOI: 10.1085/jgp.202313352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 04/14/2023] [Accepted: 05/04/2023] [Indexed: 05/23/2023] Open
Abstract
Voltage-gated K+ channels have distinct gates that regulate ion flux: the activation gate (A-gate) formed by the bundle crossing of the S6 transmembrane helices and the slow inactivation gate in the selectivity filter. These two gates are bidirectionally coupled. If coupling involves the rearrangement of the S6 transmembrane segment, then we predict state-dependent changes in the accessibility of S6 residues from the water-filled cavity of the channel with gating. To test this, we engineered cysteines, one at a time, at S6 positions A471, L472, and P473 in a T449A Shaker-IR background and determined the accessibility of these cysteines to cysteine-modifying reagents MTSET and MTSEA applied to the cytosolic surface of inside-out patches. We found that neither reagent modified either of the cysteines in the closed or the open state of the channels. On the contrary, A471C and P473C, but not L472C, were modified by MTSEA, but not by MTSET, if applied to inactivated channels with open A-gate (OI state). Our results, combined with earlier studies reporting reduced accessibility of residues I470C and V474C in the inactivated state, strongly suggest that the coupling between the A-gate and the slow inactivation gate is mediated by rearrangements in the S6 segment. The S6 rearrangements are consistent with a rigid rod-like rotation of S6 around its longitudinal axis upon inactivation. S6 rotation and changes in its environment are concomitant events in slow inactivation of Shaker KV channels.
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Affiliation(s)
- Tibor G. Szanto
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Ferenc Papp
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Florina Zakany
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltan Varga
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Carol Deutsch
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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Labbaf A, Dellin M, Komadowski M, Chetkovich DM, Decher N, Pape HC, Seebohm G, Budde T, Zobeiri M. Characterization of Kv1.2-mediated outward current in TRIP8b-deficient mice. Biol Chem 2023; 404:291-302. [PMID: 36852869 DOI: 10.1515/hsz-2023-0116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 02/16/2023] [Indexed: 03/01/2023]
Abstract
Tonic current through hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels is influencing neuronal firing properties and channel function is strongly influenced by the brain-specific auxiliary subunit tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b). Since Kv1.2 channels and TRIP8b were also suggested to interact, we assessed brain Kv1.2 mRNA and protein expression as well as the reduction of K+ outward currents by Kv1.2-blocking compounds (Psora-4; tityustoxin-Kα, TsTX-Kα) in different brain areas of TRIP8b-deficient (TRIP8b -/- ) compared to wildtype (WT) mice. We found that transcription levels of Kv1.2 channels were not different between genotypes. Furthermore, Kv1.2 current amplitude was not affected upon co-expression with TRIP8b in oocytes. However, Kv1.2 immunofluorescence was stronger in dendritic areas of cortical and hippocampal neurons. Furthermore, the peak net outward current was increased and the inactivation of the Psora-4-sensitive current component was less pronounced in cortical neurons in TRIP8b -/- mice. In current clamp recordings, application of TsTX increased the excitability of thalamocortical (TC) neurons with increased number of elicited action potentials upon step depolarization. We conclude that TRIP8b may not preferentially influence the amplitude of current through Kv1.2 channels but seems to affect current inactivation and channel localization. In TRIP8b -/- a compensatory upregulation of other Kv channels was observed.
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Affiliation(s)
- Afsaneh Labbaf
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany
| | - Maurice Dellin
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany
| | - Marlene Komadowski
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Deutschhausstr. 1-2, 35037, Marburg, Germany
| | - Dane M Chetkovich
- Medical Center, Department of Neurology, Vanderbilt University, Nashville, TN, USA
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Deutschhausstr. 1-2, 35037, Marburg, Germany
| | - Hans-Chrisitian Pape
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany
| | - Guiscard Seebohm
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany
| | - Mehrnoush Zobeiri
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany
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Ortner NJ. CACNA1D-Related Channelopathies: From Hypertension to Autism. Handb Exp Pharmacol 2023. [PMID: 36592224 DOI: 10.1007/164_2022_626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Tightly controlled Ca2+ influx through voltage-gated Ca2+ channels (Cavs) is indispensable for proper physiological function. Thus, it is not surprising that Cav loss and/or gain of function have been implicated in human pathology. Deficiency of Cav1.3 L-type Ca2+ channels (LTCCs) causes deafness and bradycardia, whereas several genetic variants of CACNA1D, the gene encoding the pore-forming α1 subunit of Cav1.3, have been linked to various disease phenotypes, such as hypertension, congenital hypoglycemia, or autism. These variants include not only common polymorphisms associated with an increased disease risk, but also rare de novo missense variants conferring high risk. This review provides a concise summary of disease-associated CACNA1D variants, whereas the main focus lies on de novo germline variants found in individuals with a neurodevelopmental disorder of variable severity. Electrophysiological recordings revealed activity-enhancing gating changes induced by these de novo variants, and tools to predict their pathogenicity and to study the resulting pathophysiological consequences will be discussed. Despite the low number of affected patients, potential phenotype-genotype correlations and factors that could impact the severity of symptoms will be covered. Since increased channel activity is assumed as the disease-underlying mechanism, pharmacological inhibition could be a treatment option. In the absence of Cav1.3-selective blockers, dihydropyridine LTCC inhibitors clinically approved for the treatment of hypertension may be used for personalized off-label trials. Findings from in vitro studies and treatment attempts in some of the patients seem promising as outlined. Taken together, due to advances in diagnostic sequencing techniques the number of reported CACNA1D variants in human diseases is constantly rising. Evidence from in silico, in vitro, and in vivo disease models can help to predict the pathogenic potential of such variants and to guide diagnosis and treatment in the clinical practice when confronted with patients harboring CACNA1D variants.
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Affiliation(s)
- Nadine J Ortner
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
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Wang ZW, Trussell LO, Vedantham K. Regulation of Neurotransmitter Release by K + Channels. ADVANCES IN NEUROBIOLOGY 2023; 33:305-331. [PMID: 37615872 DOI: 10.1007/978-3-031-34229-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
K+ channels play potent roles in the process of neurotransmitter release by influencing the action potential waveform and modulating neuronal excitability and release probability. These diverse effects of K+ channel activation are ensured by the wide variety of K+ channel genes and their differential expression in different cell types. Accordingly, a variety of K+ channels have been implicated in regulating neurotransmitter release, including the Ca2+- and voltage-gated K+ channel Slo1 (also known as BK channel), voltage-gated K+ channels of the Kv3 (Shaw-type), Kv1 (Shaker-type), and Kv7 (KCNQ) families, G-protein-gated inwardly rectifying K+ (GIRK) channels, and SLO-2 (a Ca2+-. Cl-, and voltage-gated K+ channel in C. elegans). These channels vary in their expression patterns, subcellular localization, and biophysical properties. Their roles in neurotransmitter release may also vary depending on the synapse and physiological or experimental conditions. This chapter summarizes key findings about the roles of K+ channels in regulating neurotransmitter release.
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Affiliation(s)
- Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA.
| | - Laurence O Trussell
- Oregon Hearing Research Center & Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Kiranmayi Vedantham
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
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Peng Y, Zhang Q, Cheng H, Shen S, Weng X. Activation of TREK1 Channel in the Anterior Cingulate Cortex Improves Neuropathic Pain in a Rat Model. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2022; 2022:1372823. [PMID: 36211011 PMCID: PMC9546664 DOI: 10.1155/2022/1372823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/15/2022] [Accepted: 06/27/2022] [Indexed: 11/18/2022]
Abstract
Objective. To explore the biological function and mechanism of TREK1 in neuropathic pain. Thirty-two healthy rats and rats with sciatic nerve chronic press-fitting model (chronic constriction injury of the sciatic nerve, CCI) were selected. Western blot, immunofluorescence staining, and patch clamp technique were performed to explore the biological functions of TREK1. The expression of TREK1 was decreased in the CCI model. The TREK1 channel current in the CCI model was decreased. After local administration of TREK1 channel activator in the anterior cingulate cortex area, the pain behavior of CCI rats and the expression of TREK1 protein were reversed. The expression of TREK1 was downregulated in the ACC area of CCI rats and the current of TREK1 was decreased, which played an important role in the regulation of neuropathic pain.
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Affiliation(s)
- Yuanzhi Peng
- Department of Anesthesiology and SICU, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, China
| | - Qingqing Zhang
- Department of Anesthesiology and SICU, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, China
| | - Hao Cheng
- Department of Cardiovascular Surgery, Changhai Hospital, the Navy Medical University, Shanghai 200433, China
| | - Saie Shen
- Department of Anesthesiology and SICU, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, China
| | - Xiaojian Weng
- Department of Anesthesiology and SICU, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, China
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9
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Sharma K, Kang KW, Seo YW, Glowatzki E, Yi E. Low-voltage Activating K + Channels in Cochlear Afferent Nerve Fiber Dendrites. Exp Neurobiol 2022; 31:243-259. [PMID: 36050224 PMCID: PMC9471414 DOI: 10.5607/en22013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/18/2022] [Accepted: 07/29/2022] [Indexed: 11/19/2022] Open
Abstract
Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.
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Affiliation(s)
- Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Young-Woo Seo
- KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea
| | - Elisabeth Glowatzki
- Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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10
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A missense mutation in Kcnc3 causes hippocampal learning deficits in mice. Proc Natl Acad Sci U S A 2022; 119:e2204901119. [PMID: 35881790 PMCID: PMC9351536 DOI: 10.1073/pnas.2204901119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although a wide variety of genetic tools has been developed to study learning and memory, the molecular basis of memory encoding remains incompletely understood. Here, we undertook an unbiased approach to identify novel genes critical for memory encoding. From a large-scale, in vivo mutagenesis screen using contextual fear conditioning, we isolated in mice a mutant, named Clueless, with spatial learning deficits. A causative missense mutation (G434V) was found in the voltage-gated potassium channel, subfamily C member 3 (Kcnc3) gene in a region that encodes a transmembrane voltage sensor. Generation of a Kcnc3G434V CRISPR mutant mouse confirmed this mutation as the cause of the learning defects. While G434V had no effect on transcription, translation, or trafficking of the channel, electrophysiological analysis of the G434V mutant channel revealed a complete loss of voltage-gated conductance, a broadening of the action potential, and decreased neuronal firing. Together, our findings have revealed a role for Kcnc3 in learning and memory.
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11
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Bogacheva PO, Molchanova AI, Pravdivceva ES, Miteva AS, Balezina OP, Gaydukov AE. ProBDNF and Brain-Derived Neurotrophic Factor Prodomain Differently Modulate Acetylcholine Release in Regenerating and Mature Mouse Motor Synapses. Front Cell Neurosci 2022; 16:866802. [PMID: 35591942 PMCID: PMC9110780 DOI: 10.3389/fncel.2022.866802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/18/2022] [Indexed: 11/30/2022] Open
Abstract
The effects of brain-derived neurotrophic factor (BDNF) processing by-products (proBDNF and BDNF prodomain) on the activity of mouse neuromuscular junctions (NMJs) were studied in synapses formed during the reinnervation of extensor digitorum longus muscle (m. EDL) and mature synapses of the diaphragm. The parameters of spontaneous miniature endplate potentials (MEPPs) and evoked endplate potentials (EPPs) were analyzed in presence of each of the BDNF maturation products (both – 1 nM). In newly formed NMJs, proBDNF caused an increase in the resting membrane potential of muscle fibers and a decrease in the frequency of MEPPs, which was prevented by tertiapin-Q, a G-protein-coupled inwardly rectifying potassium channels (GIRK) blocker but not by p75 receptor signaling inhibitor TAT-Pep5. proBDNF had no effect on the parameters of EPPs. BDNF prodomain in newly formed synapses had effects different from those of proBDNF: it increased the amplitude of MEPPs, which was prevented by vesamicol, an inhibitor of vesicular acetylcholine (ACh) transporter; and reduced the quantal content of EPPs. In mature NMJs, proBDNF did not influence MEPPs parameters, but BDNF prodomain suppressed both spontaneous and evoked ACh release: decreased the frequency and amplitude of MEPPs, and the amplitude and quantal content of EPPs. This effect of the BDNF prodomain was prevented by blocking GIRK channels, by TAT-Pep5 or by Rho-associated protein kinase (ROCK) inhibitor Y-27632. At the same time, the BDNF prodomain did not show any inhibitory effects in diaphragm motor synapses of pannexin 1 knockout mice, which have impaired purinergic regulation of neuromuscular transmission. The data obtained suggest that there is a previously unknown mechanism for the acute suppression of spontaneous and evoked ACh release in mature motor synapses, which involves the activation of p75 receptors, ROCK and GIRK channels by BDNF prodomain and requires interaction with metabotropic purinoreceptors. In general, our results show that both the precursor of BDNF and the product of its maturation have predominantly inhibitory effects on spontaneous and evoked ACh release in newly formed or functionally mature neuromuscular junctions, which are mainly opposite to the effects of BDNF. The inhibitory influences of both proteins related to brain neurotrophin are mediated via GIRK channels of mouse NMJs.
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12
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The role of axonal voltage-gated potassium channels in tDCS. Brain Stimul 2022; 15:861-869. [DOI: 10.1016/j.brs.2022.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/17/2022] [Accepted: 05/26/2022] [Indexed: 11/17/2022] Open
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13
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Zhang Y, Li D, Darwish Y, Fu X, Trussell LO, Huang H. KCNQ Channels Enable Reliable Presynaptic Spiking and Synaptic Transmission at High Frequency. J Neurosci 2022; 42:3305-3315. [PMID: 35256530 PMCID: PMC9034779 DOI: 10.1523/jneurosci.0363-20.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 02/06/2022] [Accepted: 02/26/2022] [Indexed: 11/21/2022] Open
Abstract
The presynaptic action potential (AP) is required to drive calcium influx into nerve terminals, resulting in neurotransmitter release. Accordingly, the AP waveform is crucial in determining the timing and strength of synaptic transmission. The calyx of Held nerve terminals of rats of either sex showed minimum changes in AP waveform during high-frequency AP firing. We found that the stability of the calyceal AP waveform requires KCNQ (KV7) K+ channel activation during high-frequency spiking activity. High-frequency presynaptic spikes gradually led to accumulation of KCNQ channels in open states which kept interspike membrane potential sufficiently negative to maintain Na+ channel availability. Blocking KCNQ channels during stimulus trains led to inactivation of presynaptic Na+, and to a lesser extent KV1 channels, thereby reducing the AP amplitude and broadening AP duration. Moreover, blocking KCNQ channels disrupted the stable calcium influx and glutamate release required for reliable synaptic transmission at high frequency. Thus, while KCNQ channels are generally thought to prevent hyperactivity of neurons, we find that in axon terminals these channels function to facilitate reliable high-frequency synaptic signaling needed for sensory information processing.SIGNIFICANCE STATEMENT The presynaptic spike results in calcium influx required for neurotransmitter release. For this reason, the spike waveform is crucial in determining the timing and strength of synaptic transmission. Auditory information is encoded by spikes phase locked to sound frequency at high rates. The calyx of Held nerve terminals in the auditory brainstem show minimum changes in spike waveform during high-frequency spike firing. We found that activation of KCNQ K+ channel builds up during high-frequency firing and its activation helps to maintain a stable spike waveform and reliable synaptic transmission. While KCNQ channels are generally thought to prevent hyperexcitability of neurons, we find that in axon terminals these channels function to facilitate high-frequency synaptic signaling during auditory information processing.
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Affiliation(s)
- Yihui Zhang
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118
| | - Dainan Li
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118
| | - Youad Darwish
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118
| | - Xin Fu
- Brain Institute, Tulane University, New Orleans, LA 70118
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR 97239
| | - Hai Huang
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118
- Brain Institute, Tulane University, New Orleans, LA 70118
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Overexpression of Neuregulin-1 Type III Has Impact on Visual Function in Mice. Int J Mol Sci 2022; 23:ijms23094489. [PMID: 35562880 PMCID: PMC9104020 DOI: 10.3390/ijms23094489] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/16/2022] [Accepted: 04/17/2022] [Indexed: 12/05/2022] Open
Abstract
Schizophrenia is associated with several brain deficits, including abnormalities in visual processes. Neuregulin-1 (Nrg1) is a family of trophic factors containing an epidermal growth factor (EGF)-like domain. It is thought to play a role in neural development and has been linked to neuropsychiatric disorders. Abnormal Nrg1 expression has been observed in schizophrenia in clinical studies. Moreover, in schizophrenia, there is more and more evidence found about pathological changes of the retina regarding structural, neurochemical and physiological parameters. However, mechanisms of these changes are not well known. To investigate this, we analysed the function of the visual system using electroretinography (ERG) and the measurement of visual evoked potentials (VEP) in transgenic mice overexpressing Nrg1 type III of three different ages (12 weeks, 24 weeks and 55 weeks). ERG amplitudes tended to be higher in transgenic mice than in control mice in 12-week old mice, whereas the amplitudes were almost similar in older mice. VEP amplitudes were larger in transgenic mice at all ages, with significant differences at 12 and 55 weeks (p values between 0.003 and 0.036). Latencies in ERG and VEP measurements did not differ considerably between control mice and transgenic mice at any age. Our data show for the first time that overexpression of Nrg1 type III changed visual function in transgenic mice. Overall, this investigation of visual function in transgenic mice may be helpful to understand corresponding changes that occur in schizophrenia, as they may find use as biomarkers for psychiatric disorders as well as a potential tool for diagnosis in psychiatry.
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15
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Wang GH, Chuang AY, Lai YC, Chen HI, Hsueh SW, Yang YC. Pre- and post-synaptic A-type K + channels regulate glutamatergic transmission and switch of the network into epileptiform oscillations. Br J Pharmacol 2022; 179:3754-3777. [PMID: 35170022 DOI: 10.1111/bph.15818] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 12/28/2021] [Accepted: 02/02/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Anticonvulsants targeting K+ channels have not been clinically available, although neuronal hyperexcitability in seizures could be suppressed by activation of K+ channels. Voltage-gated A-type K+ channel (A-channel) inhibitors may be prescribed for diseases of neuromuscular junction but could cause seizures. Consistently, genetic loss of function of A-channels may also cause seizures. It is unclear why inhibition of A-channels, if compared with the other types of K+ channels, is particularly prone to seizure induction. This hinders the development of relevant therapeutic interventions. EXPERIMENTAL APPROACH The epileptogenic mechanisms of A-channel inhibition and antiepileptic actions of A-channel activation were investigated in electrophysiological and behavioral seizures with pharmacological and optogenetic maneuvers. KEY RESULTS Presynaptic Kv1.4 and postsynaptic Kv4.3 A-channels act synergistically to gate glutamatergic transmission and control rhythmogenesis in the amygdala. The interconnected neurons set into the oscillatory mode by A-channel inhibition would reverberate with regular paces and the same top frequency, demonstrating a spatiotemporally well-orchestrated system with built-in oscillatory rhythms normally curbed by A-channels. Accordingly, selective over-excitation of glutamatergic neurons or inhibition of A-channels suffices to induce behavioral seizures, which are effectively ameliorated by A-channel activators such as NS-5806 or AMPA receptor antagonists such as perampanel. CONCLUSION AND IMPLICATIONS Transsynaptic voltage-dependent A-channels serve as a biophysical-biochemical transducer responsible for a novel form of synaptic plasticity. Such a network-level switch into and out of the oscillatory mode may underlie a wide-scope of telencephalic information processing, or to its extreme, epileptic seizures. A-channels thus constitute a potential target of antiepileptic therapy.
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Affiliation(s)
- Guan-Hsun Wang
- Department of Neurology, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, Taiwan
| | - Ai-Yu Chuang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Yi-Chen Lai
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Hsin-I Chen
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Shu-Wei Hsueh
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Ya-Chin Yang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.,Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, Taiwan.,Department of Psychiatry, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, Taiwan
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16
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Baudin P, Cousyn L, Navarro V. The LGI1 protein: molecular structure, physiological functions and disruption-related seizures. Cell Mol Life Sci 2021; 79:16. [PMID: 34967933 PMCID: PMC11072701 DOI: 10.1007/s00018-021-04088-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/07/2021] [Accepted: 12/09/2021] [Indexed: 01/16/2023]
Abstract
Leucine-rich, glioma inactivated 1 (LGI1) is a secreted glycoprotein, mainly expressed in the brain, and involved in central nervous system development and physiology. Mutations of LGI1 have been linked to autosomal dominant lateral temporal lobe epilepsy (ADLTE). Recently auto-antibodies against LGI1 have been described as the basis for an autoimmune encephalitis, associated with specific motor and limbic epileptic seizures. It is the second most common cause of autoimmune encephalitis. This review presents details on the molecular structure, expression and physiological functions of LGI1, and examines how their disruption underlies human pathologies. Knock-down of LGI1 in rodents reveals that this protein is necessary for normal brain development. In mature brains, LGI1 is associated with Kv1 channels and AMPA receptors, via domain-specific interaction with membrane anchoring proteins and contributes to regulation of the expression and function of these channels. Loss of function, due to mutations or autoantibodies, of this key protein in the control of neuronal activity is a common feature in the genesis of epileptic seizures in ADLTE and anti-LGI1 autoimmune encephalitis.
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Affiliation(s)
- Paul Baudin
- Sorbonne Université, Paris Brain Institute - Institut du Cerveau, ICM, INSERM, CNRS, AP-HP, Pitié-Salpêtrière Hospital, Paris, France
| | - Louis Cousyn
- Sorbonne Université, Paris Brain Institute - Institut du Cerveau, ICM, INSERM, CNRS, AP-HP, Pitié-Salpêtrière Hospital, Paris, France
- AP-HP, Epilepsy Unit, Pitié-Salpêtrière Hospital, DMU Neurosciences, Paris, France
| | - Vincent Navarro
- Sorbonne Université, Paris Brain Institute - Institut du Cerveau, ICM, INSERM, CNRS, AP-HP, Pitié-Salpêtrière Hospital, Paris, France.
- AP-HP, Epilepsy Unit, Pitié-Salpêtrière Hospital, DMU Neurosciences, Paris, France.
- AP-HP, Center of Reference for Rare Epilepsies, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
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17
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Diochot S. Pain-related toxins in scorpion and spider venoms: a face to face with ion channels. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20210026. [PMID: 34925480 PMCID: PMC8667759 DOI: 10.1590/1678-9199-jvatitd-2021-0026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/10/2021] [Indexed: 12/12/2022] Open
Abstract
Pain is a common symptom induced during envenomation by spiders and scorpions.
Toxins isolated from their venom have become essential tools for studying the
functioning and physiopathological role of ion channels, as they modulate their
activity. In particular, toxins that induce pain relief effects can serve as a
molecular basis for the development of future analgesics in humans. This review
provides a summary of the different scorpion and spider toxins that directly
interact with pain-related ion channels, with inhibitory or stimulatory effects.
Some of these toxins were shown to affect pain modalities in different animal
models providing information on the role played by these channels in the pain
process. The close interaction of certain gating-modifier toxins with membrane
phospholipids close to ion channels is examined along with molecular approaches
to improve selectivity, affinity or bioavailability in vivo for
therapeutic purposes.
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Affiliation(s)
- Sylvie Diochot
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Centre National de la Recherche Scientifique (CNRS) UMR 7275 et Université Côte d'Azur (UCA), 06560 Valbonne, France. Institut de Pharmacologie Moléculaire et Cellulaire Centre National de la Recherche Scientifique Université Côte d'Azur Valbonne France
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18
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Fels E, Muñiz-Castrillo S, Vogrig A, Joubert B, Honnorat J, Pascual O. Role of LGI1 protein in synaptic transmission: From physiology to pathology. Neurobiol Dis 2021; 160:105537. [PMID: 34695575 DOI: 10.1016/j.nbd.2021.105537] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 01/17/2023] Open
Abstract
Leucine-Rich Glioma Inactivated protein 1 (LGI1) is a secreted neuronal protein highly expressed in the central nervous system and high amount are found in the hippocampus. An alteration of its function has been described in few families of patients with autosomal dominant temporal lobe epilepsy (ADLTE) or with autoimmune limbic encephalitis (LE), both characterized by epileptic seizures. Studies have shown that LGI1 plays an essential role during development, but also in neuronal excitability through an action on voltage-gated potassium Kv1.1 channels, and in synaptic transmission by regulating the surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-R). Over the last decade, a growing number of studies investigating LGI1 functions have been published. They aimed to improve the understanding of LGI1 function in the regulation of neuronal networks using different animal and cellular models. LGI1 appears to be a major actor of synaptic regulation by modulating trans-synaptically pre- and post-synaptic proteins. In this review, we will focus on LGI1 binding partners, "A Disintegrin And Metalloprotease (ADAM) 22 and 23", the complex they form at the synapse, and will discuss the effects of LGI1 on neuronal excitability and synaptic transmission in physiological and pathological conditions. Finally, we will highlight new insights regarding N-terminal Leucine-Rich Repeat (LRR) domain and C-terminal Epitempin repeat (EPTP) domain and their potentially distinct role in LGI1 function.
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Affiliation(s)
- Elodie Fels
- Synaptopathies and Auto-antibodies (SynatAc) Team, Institut NeuroMyoGène, INSERM U1217/CNRS UMR 5310, Universités de Lyon, Université Claude Bernard Lyon 1, Lyon, France; Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France
| | - Sergio Muñiz-Castrillo
- Synaptopathies and Auto-antibodies (SynatAc) Team, Institut NeuroMyoGène, INSERM U1217/CNRS UMR 5310, Universités de Lyon, Université Claude Bernard Lyon 1, Lyon, France; Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France; French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Hôpital Neurologique, 59 Boulevard Pinel, 69677 Bron Cedex, France
| | - Alberto Vogrig
- Synaptopathies and Auto-antibodies (SynatAc) Team, Institut NeuroMyoGène, INSERM U1217/CNRS UMR 5310, Universités de Lyon, Université Claude Bernard Lyon 1, Lyon, France; Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France; French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Hôpital Neurologique, 59 Boulevard Pinel, 69677 Bron Cedex, France
| | - Bastien Joubert
- Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France; French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Hôpital Neurologique, 59 Boulevard Pinel, 69677 Bron Cedex, France
| | - Jérôme Honnorat
- Synaptopathies and Auto-antibodies (SynatAc) Team, Institut NeuroMyoGène, INSERM U1217/CNRS UMR 5310, Universités de Lyon, Université Claude Bernard Lyon 1, Lyon, France; Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France; French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Hôpital Neurologique, 59 Boulevard Pinel, 69677 Bron Cedex, France.
| | - Olivier Pascual
- Synaptopathies and Auto-antibodies (SynatAc) Team, Institut NeuroMyoGène, INSERM U1217/CNRS UMR 5310, Universités de Lyon, Université Claude Bernard Lyon 1, Lyon, France; Université Claude Bernard Lyon 1, Universités de Lyon, Lyon, France.
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19
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OIsen T, Capurro A, Švent M, Pilati N, Large C, Hartell N, Hamann M. Sparsely Distributed, Pre-synaptic Kv3 K + Channels Control Spontaneous Firing and Cross-Unit Synchrony via the Regulation of Synaptic Noise in an Auditory Brainstem Circuit. Front Cell Neurosci 2021; 15:721371. [PMID: 34539351 PMCID: PMC8446535 DOI: 10.3389/fncel.2021.721371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 08/02/2021] [Indexed: 11/13/2022] Open
Abstract
Spontaneous subthreshold activity in the central nervous system is fundamental to information processing and transmission, as it amplifies and optimizes sub-threshold signals, thereby improving action potential initiation and maintaining reliable firing. This form of spontaneous activity, which is frequently considered noise, is particularly important at auditory synapses where acoustic information is encoded by rapid and temporally precise firing rates. In contrast, when present in excess, this form of noise becomes detrimental to acoustic information as it contributes to the generation and maintenance of auditory disorders such as tinnitus. The most prominent contribution to subthreshold noise is spontaneous synaptic transmission (synaptic noise). Although numerous studies have examined the role of synaptic noise on single cell excitability, little is known about its pre-synaptic modulation owing in part to the difficulties of combining noise modulation with monitoring synaptic release. Here we study synaptic noise in the auditory brainstem dorsal cochlear nucleus (DCN) of mice and show that pharmacological potentiation of Kv3 K+ currents reduces the level of synaptic bombardment onto DCN principal fusiform cells. Using a transgenic mouse line (SyG37) expressing SyGCaMP2-mCherry, a calcium sensor that targets pre-synaptic terminals, we show that positive Kv3 K+ current modulation decreases calcium influx in a fifth of pre-synaptic boutons. Furthermore, while maintaining rapid and precise spike timing, positive Kv3 K+ current modulation increases the synchronization of local circuit neurons by reducing spontaneous activity. In conclusion, our study identifies a unique pre-synaptic mechanism which reduces synaptic noise at auditory synapses and contributes to the coherent activation of neurons in a local auditory brainstem circuit. This form of modulation highlights a new therapeutic target, namely the pre-synaptic bouton, for ameliorating the effects of hearing disorders which are dependent on aberrant spontaneous activity within the central auditory system.
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Affiliation(s)
- Timothy OIsen
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom.,Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Alberto Capurro
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom.,Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Maša Švent
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom
| | | | - Charles Large
- Autifony Therapeutics Limited, Stevenage Bioscience Catalyst, Stevenage, United Kingdom
| | - Nick Hartell
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom
| | - Martine Hamann
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, United Kingdom.,Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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A Novel KCNA2 Variant in a Patient with Non-Progressive Congenital Ataxia and Epilepsy: Functional Characterization and Sensitivity to 4-Aminopyridine. Int J Mol Sci 2021; 22:ijms22189913. [PMID: 34576077 PMCID: PMC8469797 DOI: 10.3390/ijms22189913] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/02/2021] [Accepted: 09/08/2021] [Indexed: 12/26/2022] Open
Abstract
Kv1.2 channels, encoded by the KCNA2 gene, are localized in the central and peripheral nervous system, where they regulate neuronal excitability. Recently, heterozygous mutations in KCNA2 have been associated with a spectrum of symptoms extending from epileptic encephalopathy, intellectual disability, and cerebellar ataxia. Patients are treated with a combination of antiepileptic drugs and 4-aminopyridine (4-AP) has been recently trialed in specific cases. We identified a novel variant in KCNA2, E236K, in a Serbian proband with non-progressive congenital ataxia and early onset epilepsy, treated with sodium valproate. To ascertain the pathogenicity of E236K mutation and to verify its sensitivity to 4-AP, we transfected HEK 293 cells with Kv1.2 WT or E236K cDNAs and recorded potassium currents through the whole-cell patch-clamp. In silico analysis supported the electrophysiological data. E236K channels showed voltage-dependent activation shifted towards negative potentials and slower kinetics of deactivation and activation compared with Kv1.2 WT. Heteromeric Kv1.2 WT+E236K channels, resembling the condition of the heterozygous patient, confirmed a mixed gain- and loss-of-function (GoF/LoF) biophysical phenotype. 4-AP inhibited both Kv1.2 and E236K channels with similar potency. Homology modeling studies of mutant channels suggested a reduced interaction between the residue K236 in the S2 segment and the gating charges at S4. Overall, the biophysical phenotype of E236K channels correlates with the mild end of the clinical spectrum reported in patients with GoF/LoF defects. The response to 4-AP corroborates existing evidence that KCNA2-disorders could benefit from variant-tailored therapeutic approaches, based on functional studies.
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21
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K v1.1 channels mediate network excitability and feed-forward inhibition in local amygdala circuits. Sci Rep 2021; 11:15180. [PMID: 34312446 PMCID: PMC8313690 DOI: 10.1038/s41598-021-94633-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 07/14/2021] [Indexed: 01/15/2023] Open
Abstract
Kv1.1 containing potassium channels play crucial roles towards dampening neuronal excitability. Mice lacking Kv1.1 subunits (Kcna1−/−) display recurrent spontaneous seizures and often exhibit sudden unexpected death. Seizures in Kcna1−/− mice resemble those in well-characterized models of temporal lobe epilepsy known to involve limbic brain regions and spontaneous seizures result in enhanced cFos expression and neuronal death in the amygdala. Yet, the functional alterations leading to amygdala hyperexcitability have not been identified. In this study, we used Kcna1−/− mice to examine the contributions of Kv1.1 subunits to excitability in neuronal subtypes from basolateral (BLA) and central lateral (CeL) amygdala known to exhibit distinct firing patterns. We also analyzed synaptic transmission properties in an amygdala local circuit predicted to be involved in epilepsy-related comorbidities. Our data implicate Kv1.1 subunits in controlling spontaneous excitatory synaptic activity in BLA pyramidal neurons. In the CeL, Kv1.1 loss enhances intrinsic excitability and impairs inhibitory synaptic transmission, notably resulting in dysfunction of feed-forward inhibition, a critical mechanism for controlling spike timing. Overall, we find inhibitory control of CeL interneurons is reduced in Kcna1−/− mice suggesting that basal inhibitory network functioning is less able to prevent recurrent hyperexcitation related to seizures.
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Gene Expression Profile in Different Age Groups and Its Association with Cognitive Function in Healthy Malay Adults in Malaysia. Cells 2021; 10:cells10071611. [PMID: 34199148 PMCID: PMC8304476 DOI: 10.3390/cells10071611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/13/2021] [Accepted: 06/21/2021] [Indexed: 11/16/2022] Open
Abstract
The mechanism of cognitive aging at the molecular level is complex and not well understood. Growing evidence suggests that cognitive differences might also be caused by ethnicity. Thus, this study aims to determine the gene expression changes associated with age-related cognitive decline among Malay adults in Malaysia. A cross-sectional study was conducted on 160 healthy Malay subjects, aged between 28 and 79, and recruited around Selangor and Klang Valley, Malaysia. Gene expression analysis was performed using a HumanHT-12v4.0 Expression BeadChip microarray kit. The top 20 differentially expressed genes at p < 0.05 and fold change (FC) = 1.2 showed that PAFAH1B3, HIST1H1E, KCNA3, TM7SF2, RGS1, and TGFBRAP1 were regulated with increased age. The gene set analysis suggests that the Malay adult's susceptibility to developing age-related cognitive decline might be due to the changes in gene expression patterns associated with inflammation, signal transduction, and metabolic pathway in the genetic network. It may, perhaps, have important implications for finding a biomarker for cognitive decline and offer molecular targets to achieve successful aging, mainly in the Malay population in Malaysia.
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23
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Szanto TG, Gaal S, Karbat I, Varga Z, Reuveny E, Panyi G. Shaker-IR K+ channel gating in heavy water: Role of structural water molecules in inactivation. J Gen Physiol 2021; 153:212166. [PMID: 34014250 PMCID: PMC8148028 DOI: 10.1085/jgp.202012742] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 04/30/2021] [Indexed: 01/01/2023] Open
Abstract
It has been reported earlier that the slow (C-type) inactivated conformation in Kv channels is stabilized by a multipoint hydrogen-bond network behind the selectivity filter. Furthermore, MD simulations revealed that structural water molecules are also involved in the formation of this network locking the selectivity filter in its inactive conformation. We found that the application of an extracellular, but not intracellular, solution based on heavy water (D2O) dramatically slowed entry into the slow inactivated state in Shaker-IR mutants (T449A, T449A/I470A, and T449K/I470C, displaying a wide range of inactivation kinetics), consistent with the proposed effect of the dynamics of structural water molecules on the conformational stability of the selectivity filter. Alternative hypotheses capable of explaining the observed effects of D2O were examined. Increased viscosity of the external solution mimicked by the addition of glycerol had a negligible effect on the rate of inactivation. In addition, the inactivation time constants of K+ currents in the outward and the inward directions in asymmetric solutions were not affected by a H2O/D2O exchange, negating an indirect effect of D2O on the rate of K+ rehydration. The elimination of the nonspecific effects of D2O on our macroscopic current measurements supports the hypothesis that the rate of structural water exchange at the region behind the selectivity filter determines the rate of slow inactivation, as proposed by molecular modeling.
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Affiliation(s)
- Tibor G Szanto
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Szabolcs Gaal
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Izhar Karbat
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Zoltan Varga
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eitan Reuveny
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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24
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Huang CS, Wang GH, Chuang HH, Chuang AY, Yeh JY, Lai YC, Yang YC. Conveyance of cortical pacing for parkinsonian tremor-like hyperkinetic behavior by subthalamic dysrhythmia. Cell Rep 2021; 35:109007. [PMID: 33882305 DOI: 10.1016/j.celrep.2021.109007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 12/01/2020] [Accepted: 03/25/2021] [Indexed: 10/21/2022] Open
Abstract
Parkinson's disease is characterized by both hypokinetic and hyperkinetic symptoms. While increased subthalamic burst discharges have a direct causal relationship with the hypokinetic manifestations (e.g., rigidity and bradykinesia), the origin of the hyperkinetic symptoms (e.g., resting tremor and propulsive gait) has remained obscure. Neuronal burst discharges are presumed to be autonomous or less responsive to synaptic input, thereby interrupting the information flow. We, however, demonstrate that subthalamic burst discharges are dependent on cortical glutamatergic synaptic input, which is enhanced by A-type K+ channel inhibition. Excessive top-down-triggered subthalamic burst discharges then drive highly correlative activities bottom-up in the motor cortices and skeletal muscles. This leads to hyperkinetic behaviors such as tremors, which are effectively ameliorated by inhibition of cortico-subthalamic AMPAergic synaptic transmission. We conclude that subthalamic burst discharges play an imperative role in cortico-subcortical information relay, and they critically contribute to the pathogenesis of both hypokinetic and hyperkinetic parkinsonian symptoms.
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Affiliation(s)
- Chen-Syuan Huang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Guan-Hsun Wang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; School of Medicine, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Department of Medical Education, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 333, Taiwan
| | - Hsiang-Hao Chuang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Ai-Yu Chuang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Jui-Yu Yeh
- Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Yi-Chen Lai
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Ya-Chin Yang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan; Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan 333, Taiwan.
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25
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Murano H, Kaneko T, Zaw SYM, Sone PP, Zaw ZCT, Okada Y, Sunakawa M, Katsube KI, Okiji T. Pulp inflammation induces Kv1.1 K + channel down-regulation in rat thalamus. Oral Dis 2021; 28:1674-1681. [PMID: 33811796 DOI: 10.1111/odi.13866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 03/07/2021] [Accepted: 03/16/2021] [Indexed: 10/21/2022]
Abstract
OBJECTIVES Signals from inflamed tooth pulp activate thalamic neurons to evoke central sensitization. We aimed to gain insights into the mechanisms mediating the early phase of pulpal inflammation-induced thalamic neural and glial activation. MATERIALS AND METHODS Pulpal inflammation was induced via the application of mustard oil (MO) to the upper first molar of Wistar rats with local anesthesia (LA) or saline injection. After 0.5, 1, 2, and 24 hr, contralateral thalami were subjected to microarrays, a real-time polymerase chain reaction and immunohistochemistry to identify differentially expressed genes and assess potassium voltage-gated channel subfamily A member 1 (Kv1.1)-expressing axons and glial fibrillary acidic protein (GFAP)-expressing astrocytes. RESULTS The Kv1.1 gene (Kcna1) was down-regulated and the density of Kv1.1-expressing axons decreased in non-anesthetized rats, but not in anesthetized rats 1 hr after the MO treatment. The density of GFAP-expressing astrocytes increased in both groups until 24 hr after the MO treatment, with a greater increase being observed in the saline-injection group than in the LA group. CONCLUSIONS MO induced the transient down-regulation of Kcna1, transiently reduced the density of Kv1.1-expressing axons, and increased astrocytes in thalami within 1 hr of pulpal application. These results suggest central sensitization represented by neuronal hyperexcitability and astrocyte activation.
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Affiliation(s)
- Hiroki Murano
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Tomoatsu Kaneko
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Su Yee Myo Zaw
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Phyo Pyai Sone
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Zar Chi Thein Zaw
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Yamato Okada
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Mitsuhiro Sunakawa
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | | | - Takashi Okiji
- Department of Pulp Biology and Endodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
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Imbrici P, Accogli A, Blunck R, Altamura C, Iacomino M, D’Adamo MC, Allegri A, Pedemonte M, Brolatti N, Vari S, Cataldi M, Capra V, Gustincich S, Zara F, Desaphy JF, Fiorillo C. Musculoskeletal Features without Ataxia Associated with a Novel de novo Mutation in KCNA1 Impairing the Voltage Sensitivity of Kv1.1 Channel. Biomedicines 2021; 9:75. [PMID: 33466780 PMCID: PMC7829709 DOI: 10.3390/biomedicines9010075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/02/2021] [Accepted: 01/06/2021] [Indexed: 02/06/2023] Open
Abstract
The KCNA1 gene encodes the α subunit of the voltage-gated Kv1.1 potassium channel that critically regulates neuronal excitability in the central and peripheral nervous systems. Mutations in KCNA1 have been classically associated with episodic ataxia type 1 (EA1), a movement disorder triggered by physical and emotional stress. Additional features variably reported in recent years include epilepsy, myokymia, migraine, paroxysmal dyskinesia, hyperthermia, hypomagnesemia, and cataplexy. Interestingly, a few individuals with neuromyotonia, either isolated or associated with skeletal deformities, have been reported carrying variants in the S2-S3 transmembrane segments of Kv1.1 channels in the absence of any other symptoms. Here, we have identified by whole-exome sequencing a novel de novo variant, T268K, in KCNA1 in a boy displaying recurrent episodes of neuromyotonia, muscle hypertrophy, and skeletal deformities. Through functional analysis in heterologous cells and structural modeling, we show that the mutation, located at the extracellular end of the S3 helix, causes deleterious effects, disrupting Kv1.1 function by altering the voltage dependence of activation and kinetics of deactivation, likely due to abnormal interactions with the voltage sensor in the S4 segment. Our study supports previous evidence suggesting that specific residues within the S2 and S3 segments of Kv1.1 result in a distinctive phenotype with predominant musculoskeletal presentation.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari Aldo Moro, 70121 Bari, Italy
| | - Andrea Accogli
- Medical Genetics Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (A.A.); (M.I.)
| | - Rikard Blunck
- Department of Physics, Université de Montréal, Montréal, QC H3C 3J7, Canada;
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, 70121 Bari, Italy; (C.A.); (J.-F.D.)
| | - Michele Iacomino
- Medical Genetics Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (A.A.); (M.I.)
| | - Maria Cristina D’Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, MDS-2080 Msida, Malta;
| | - Anna Allegri
- Paediatric Endocrinology Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy;
| | - Marina Pedemonte
- Paediatric Neurology and Neuromuscular Disorders Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (M.P.); (N.B.); (S.V.); (C.F.)
| | - Noemi Brolatti
- Paediatric Neurology and Neuromuscular Disorders Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (M.P.); (N.B.); (S.V.); (C.F.)
| | - Stella Vari
- Paediatric Neurology and Neuromuscular Disorders Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (M.P.); (N.B.); (S.V.); (C.F.)
| | - Matteo Cataldi
- Neuropsychiatric Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy;
| | - Valeria Capra
- Neurosurgery Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy;
| | - Stefano Gustincich
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 80131 Genoa, Italy;
| | - Federico Zara
- Medical Genetics Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (A.A.); (M.I.)
| | - Jean-Francois Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, 70121 Bari, Italy; (C.A.); (J.-F.D.)
| | - Chiara Fiorillo
- Paediatric Neurology and Neuromuscular Disorders Unit, IRCCS Institute “G. Gaslini”, 80131 Genoa, Italy; (M.P.); (N.B.); (S.V.); (C.F.)
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16126 Genoa, Italy
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27
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BmK NSPK, a Potent Potassium Channel Inhibitor from Scorpion Buthus martensii Karsch, Promotes Neurite Outgrowth via NGF/TrkA Signaling Pathway. Toxins (Basel) 2021; 13:toxins13010033. [PMID: 33466524 PMCID: PMC7824859 DOI: 10.3390/toxins13010033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 12/30/2020] [Accepted: 12/31/2020] [Indexed: 12/31/2022] Open
Abstract
Scorpion toxins represent a variety of tools to explore molecular mechanisms and cellular signaling pathways of many biological functions. These toxins are also promising lead compounds for developing treatments for many neurological diseases. In the current study, we purified a new scorpion toxin designated as BmK NSPK (Buthus martensii Karsch neurite-stimulating peptide targeting Kv channels) from the BmK venom. The primary structure was determined using Edman degradation. BmK NSPK directly inhibited outward K+ current without affecting sodium channel activities, depolarized membrane, and increased spontaneous calcium oscillation in spinal cord neurons (SCNs) at low nanomolar concentrations. BmK NSPK produced a nonmonotonic increase on the neurite extension that peaked at ~10 nM. Mechanistic studies demonstrated that BmK NSPK increased the release of nerve growth factor (NGF). The tyrosine kinases A (TrkA) receptor inhibitor, GW 441756, eliminated the BmK NSPK-induced neurite outgrowth. BmK NSPK also increased phosphorylation levels of protein kinase B (Akt) that is the downstream regulator of TrkA receptors. These data demonstrate that BmK NSPK is a new voltage-gated potassium (Kv) channel inhibitor that augments neurite extension via NGF/TrkA signaling pathway. Kv channels may represent molecular targets to modulate SCN development and regeneration and to develop the treatments for spinal cord injury.
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28
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Schieweck R, Ninkovic J, Kiebler MA. RNA-binding proteins balance brain function in health and disease. Physiol Rev 2020; 101:1309-1370. [PMID: 33000986 DOI: 10.1152/physrev.00047.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Posttranscriptional gene expression including splicing, RNA transport, translation, and RNA decay provides an important regulatory layer in many if not all molecular pathways. Research in the last decades has positioned RNA-binding proteins (RBPs) right in the center of posttranscriptional gene regulation. Here, we propose interdependent networks of RBPs to regulate complex pathways within the central nervous system (CNS). These are involved in multiple aspects of neuronal development and functioning, including higher cognition. Therefore, it is not sufficient to unravel the individual contribution of a single RBP and its consequences but rather to study and understand the tight interplay between different RBPs. In this review, we summarize recent findings in the field of RBP biology and discuss the complex interplay between different RBPs. Second, we emphasize the underlying dynamics within an RBP network and how this might regulate key processes such as neurogenesis, synaptic transmission, and synaptic plasticity. Importantly, we envision that dysfunction of specific RBPs could lead to perturbation within the RBP network. This would have direct and indirect (compensatory) effects in mRNA binding and translational control leading to global changes in cellular expression programs in general and in synaptic plasticity in particular. Therefore, we focus on RBP dysfunction and how this might cause neuropsychiatric and neurodegenerative disorders. Based on recent findings, we propose that alterations in the entire regulatory RBP network might account for phenotypic dysfunctions observed in complex diseases including neurodegeneration, epilepsy, and autism spectrum disorders.
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Affiliation(s)
- Rico Schieweck
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Jovica Ninkovic
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Michael A Kiebler
- Biomedical Center (BMC), Department for Cell Biology and Anatomy, Medical Faculty, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
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29
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Direct and indirect cholesterol effects on membrane proteins with special focus on potassium channels. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158706. [DOI: 10.1016/j.bbalip.2020.158706] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 03/19/2020] [Accepted: 03/30/2020] [Indexed: 12/16/2022]
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30
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Scarnati MS, Clarke SG, Pang ZP, Paradiso KG. Presynaptic Calcium Channel Open Probability and Changes in Calcium Influx Throughout the Action Potential Determined Using AP-Waveforms. Front Synaptic Neurosci 2020; 12:17. [PMID: 32425764 PMCID: PMC7212394 DOI: 10.3389/fnsyn.2020.00017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 03/31/2020] [Indexed: 12/02/2022] Open
Abstract
Action potentials arriving at a nerve terminal activate voltage-gated calcium channels and set the electrical driving force for calcium entry which affects the amount and duration of neurotransmitter release. During propagation, the duration, amplitude, and shape of action potentials often changes. This affects calcium entry, and can cause large changes in neurotransmitter release. Here, we have used a series of amplitude and area matched stimuli to examine how the shape and amplitude of a stimulus affect calcium influx at a presynaptic nerve terminal in the mammalian brain. We identify fundamental differences in calcium entry following calcium channel activation by a standard voltage jump vs. an action potential-like stimulation. We also tested a series of action potential-like stimuli with the same amplitude, duration, and stimulus area, but differing in their rise and decay times. We find that a stimulus that matches the rise and decay times of a physiological action potential produces a calcium channel response that is optimized over a range of peak amplitudes. Next, we determined the relative number of calcium channels that are active at different times during an action potential, which is important in the context of how local calcium domains trigger neurotransmitter release. We find the depolarizing phase of an AP-like stimulus only opens ~20% of the maximum number of calcium channels that can be activated. Channels continue to activate during the falling phase of the action potential, with peak calcium channel activation occurring near 0 mV. Although less than 25% of calcium channels are active at the end of the action potential, these calcium channels will generate a larger local calcium concentration that will increase the release probability for nearby vesicles. Determining the change in open probability of presynaptic calcium channels, and taking into account how local calcium concentration also changes throughout the action potential are both necessary to fully understand how the action potential triggers neurotransmitter release.
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Affiliation(s)
- Matthew S Scarnati
- Department of Cell Biology and Neuroscience, Rutgers University Piscataway, Piscataway, NJ, United States.,Department of Neuroscience and Cell Biology and Child Health Institute of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ, United States
| | - Stephen G Clarke
- Department of Cell Biology and Neuroscience, Rutgers University Piscataway, Piscataway, NJ, United States.,Graduate Program in Biomedical Engineering, Rutgers University Piscataway, Piscataway, NJ, United States
| | - Zhiping P Pang
- Department of Neuroscience and Cell Biology and Child Health Institute of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ, United States
| | - Kenneth G Paradiso
- Department of Cell Biology and Neuroscience, Rutgers University Piscataway, Piscataway, NJ, United States.,Child Health Institute of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ, United States
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31
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D’Adamo MC, Liantonio A, Rolland JF, Pessia M, Imbrici P. Kv1.1 Channelopathies: Pathophysiological Mechanisms and Therapeutic Approaches. Int J Mol Sci 2020; 21:ijms21082935. [PMID: 32331416 PMCID: PMC7215777 DOI: 10.3390/ijms21082935] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 04/19/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
Kv1.1 belongs to the Shaker subfamily of voltage-gated potassium channels and acts as a critical regulator of neuronal excitability in the central and peripheral nervous systems. KCNA1 is the only gene that has been associated with episodic ataxia type 1 (EA1), an autosomal dominant disorder characterized by ataxia and myokymia and for which different and variable phenotypes have now been reported. The iterative characterization of channel defects at the molecular, network, and organismal levels contributed to elucidating the functional consequences of KCNA1 mutations and to demonstrate that ataxic attacks and neuromyotonia result from cerebellum and motor nerve alterations. Dysfunctions of the Kv1.1 channel have been also associated with epilepsy and kcna1 knock-out mouse is considered a model of sudden unexpected death in epilepsy. The tissue-specific association of Kv1.1 with other Kv1 members, auxiliary and interacting subunits amplifies Kv1.1 physiological roles and expands the pathogenesis of Kv1.1-associated diseases. In line with the current knowledge, Kv1.1 has been proposed as a novel and promising target for the treatment of brain disorders characterized by hyperexcitability, in the attempt to overcome limited response and side effects of available therapies. This review recounts past and current studies clarifying the roles of Kv1.1 in and beyond the nervous system and its contribution to EA1 and seizure susceptibility as well as its wide pharmacological potential.
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Affiliation(s)
- Maria Cristina D’Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
| | - Antonella Liantonio
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
| | | | - Mauro Pessia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain Po Box 17666, UAE
| | - Paola Imbrici
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
- Correspondence:
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Clinical Spectrum of KCNA1 Mutations: New Insights into Episodic Ataxia and Epilepsy Comorbidity. Int J Mol Sci 2020; 21:ijms21082802. [PMID: 32316562 PMCID: PMC7215408 DOI: 10.3390/ijms21082802] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 12/13/2022] Open
Abstract
Mutations in the KCNA1 gene, which encodes voltage-gated Kv1.1 potassium channel α-subunits, cause a variety of human diseases, complicating simple genotype–phenotype correlations in patients. KCNA1 mutations are primarily associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1). However, some patients have EA1 in combination with epilepsy, whereas others have epilepsy alone. KCNA1 mutations can also cause hypomagnesemia and paroxysmal dyskinesia in rare cases. Why KCNA1 variants are associated with such phenotypic heterogeneity in patients is not yet understood. In this review, literature databases (PubMed) and public genetic archives (dbSNP and ClinVar) were mined for known pathogenic or likely pathogenic mutations in KCNA1 to examine whether patterns exist between mutation type and disease manifestation. Analyses of the 47 deleterious KCNA1 mutations that were identified revealed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein. In addition, insights from animal models of KCNA1 channelopathy were considered, as well as the possible influence of genetic modifiers on disease expressivity and severity. Elucidation of the complex relationship between KCNA1 variants and disease will enable better diagnostic risk assessment and more personalized therapeutic strategies for KCNA1 channelopathy.
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Bán EG, Brassai A, Vizi ES. The role of the endogenous neurotransmitters associated with neuropathic pain and in the opioid crisis: The innate pain-relieving system. Brain Res Bull 2019; 155:129-136. [PMID: 31816407 DOI: 10.1016/j.brainresbull.2019.12.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 11/22/2019] [Accepted: 12/02/2019] [Indexed: 12/28/2022]
Abstract
Neuropathic pain is a chronic pain caused by central and peripheral nerve injury, long-term diabetes or treatment with chemotherapy drugs, and it is dissimilar to other chronic pain conditions. Chronic pain usually seriously affects the quality of life, and its drug treatment may result in increased costs of social and medical care. As in the USA and Canada, in Europe, the demand for pain-relieving medicines used in chronic pain has also significantly increased, but most European countries are not experiencing an opioid crisis. In this review, the role of various endogenous transmitters (noradrenaline, dopamine, serotonin, met- and leu-enkephalins, β-endorphin, dynorphins, cannabinoids, ATP) and various receptors (α2, μ, etc.) in the innate pain-relieving system will be discussed. Furthermore, the modulation of pain processing pathways by transmitters, focusing on neuropathic pain and the role of the sympathetic nervous system in the side effects of excessive opioid treatment, will be explained.
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Affiliation(s)
- E Gy Bán
- Dept. ME1, Faculty of Medicine in English, "George Emil Palade" University of Medicine, Pharmacy, Science and Technology of Târgu-Mureș, Marosvásárhely, Romania
| | - A Brassai
- Dept. ME1, Faculty of Medicine in English, "George Emil Palade" University of Medicine, Pharmacy, Science and Technology of Târgu-Mureș, Marosvásárhely, Romania
| | - E S Vizi
- Institute of Experimental Medicine, Budapest, Hungary; Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.
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34
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Panzera LC, Hoppa MB. Genetically Encoded Voltage Indicators Are Illuminating Subcellular Physiology of the Axon. Front Cell Neurosci 2019; 13:52. [PMID: 30881287 PMCID: PMC6406964 DOI: 10.3389/fncel.2019.00052] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 02/04/2019] [Indexed: 12/13/2022] Open
Abstract
Everything we see and do is regulated by electrical signals in our nerves and muscle. Ion channels are crucial for sensing and generating electrical signals. Two voltage-dependent conductances, Na+ and K+, form the bedrock of the electrical impulse in the brain known as the action potential. Several classes of mammalian neurons express combinations of nearly 100 different varieties of these two voltage-dependent channels and their subunits. Not surprisingly, this variability orchestrates a diversity of action potential shapes and firing patterns that have been studied in detail at neural somata. A remarkably understudied phenomena exists in subcellular compartments of the axon, where action potentials initiate synaptic transmission. Ion channel research was catalyzed by the invention of glass electrodes to measure electrical signals in cell membranes, however, progress in the field of neurobiology has been stymied by the fact that most axons in the mammalian CNS are far too small and delicate for measuring ion channel function with electrodes. These quantitative measurements of membrane voltage can be achieved within the axon using light. A revolution of optical voltage sensors has enabled exploring important questions of how ion channels regulate axon physiology and synaptic transmission. In this review we will consider advantages and disadvantages of different fluorescent voltage indicators and discuss particularly relevant questions that these indicators can elucidate for understanding the crucial relationship between action potentials and synaptic transmission.
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Affiliation(s)
| | - Michael B. Hoppa
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
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35
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Alpizar SA, Cho IH, Hoppa MB. Subcellular control of membrane excitability in the axon. Curr Opin Neurobiol 2019; 57:117-125. [PMID: 30784979 DOI: 10.1016/j.conb.2019.01.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 01/21/2019] [Indexed: 12/11/2022]
Abstract
Ion channels are microscopic pore proteins in the membrane that open and close in response to chemical and electrical stimuli. This simple concept underlies rapid electrical signaling in the brain as well as several important aspects of neural plasticity. Although the soma accounts for less than 1% of many neurons by membrane area, it has been the major site of measuring ion channel function. However, the axon is one of the longest processes found in cellular biology and hosts a multitude of critical signaling functions in the brain. Not only does the axon initiate and rapidly propagate action potentials (APs) across the brain but it also forms the presynaptic terminals that convert these electrical inputs into chemical outputs. Here, we review recent advances in the physiological role of ion channels within the diverse landscape of the axon and presynaptic terminals.
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Affiliation(s)
- Scott A Alpizar
- Dartmouth College, Department of Biological Sciences, Hanover, NH, United States
| | - In Ha Cho
- Dartmouth College, Department of Biological Sciences, Hanover, NH, United States
| | - Michael B Hoppa
- Dartmouth College, Department of Biological Sciences, Hanover, NH, United States.
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36
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Yin XM, Lin JH, Cao L, Zhang TM, Zeng S, Zhang KL, Tian WT, Hu ZM, Li N, Wang JL, Guo JF, Wang RX, Xia K, Zhang ZH, Yin F, Peng J, Liao WP, Yi YH, Liu JY, Yang ZX, Chen Z, Mao X, Yan XX, Jiang H, Shen L, Chen SD, Zhang LM, Tang BS. Familial paroxysmal kinesigenic dyskinesia is associated with mutations in the KCNA1 gene. Hum Mol Genet 2019; 27:625-637. [PMID: 29294000 DOI: 10.1093/hmg/ddx430] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 12/15/2017] [Indexed: 12/23/2022] Open
Abstract
Paroxysmal kinesigenic dyskinesia (PKD) is a heterogeneous movement disorder characterized by recurrent dyskinesia attacks triggered by sudden movement. PRRT2 has been identified as the first causative gene of PKD. However, it is only responsible for approximately half of affected individuals, indicating that other loci are most likely involved in the etiology of this disorder. To explore the underlying causative gene of PRRT2-negative PKD, we used a combination strategy including linkage analysis, whole-exome sequencing and copy number variations analysis to detect the genetic variants within a family with PKD. We identified a linkage locus on chromosome 12 (12p13.32-12p12.3) and detected a novel heterozygous mutation c.956 T>G (p.319 L>R) in the potassium voltage-gated channel subfamily A member 1, KCNA1. Whole-exome sequencing in another 58 Chinese patients with PKD who lacked mutations in PRRT2 revealed another novel mutation in the KCNA1 gene [c.765 C>A (p.255 N>K)] within another family. Biochemical analysis revealed that the L319R mutant accelerated protein degradation via the proteasome pathway and disrupted membrane expression of the Kv1.1 channel. Electrophysiological examinations in transfected HEK293 cells showed that both the L319R and N255K mutants resulted in reduced potassium currents and respective altered gating properties, with a dominant negative effect on the Kv1.1 wild-type channel. Our study suggests that these mutations in KCNA1 cause the Kv1.1 channel dysfunction, which leads to familial PKD. The current study further extended the genotypic spectrum of this disorder, indicating that Kv1.1 channel dysfunction maybe one of the underlying defects in PKD.
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Affiliation(s)
- Xiao-Meng Yin
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Jing-Han Lin
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, China
| | - Li Cao
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Tong-Mei Zhang
- Department of Physiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.,The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Sheng Zeng
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kai-Lin Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Wo-Tu Tian
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Zheng-Mao Hu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Nan Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Jun-Ling Wang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Ji-Feng Guo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Ruo-Xi Wang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Institute of Precision Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kun Xia
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhuo-Hua Zhang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Institute of Precision Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Department of Neurosciences, School of Medicine, University of South China, Hengyang, Hunan 420001, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Hunan Intellectual and Development Disabilities Research Center, Changsha, Hunan 410008, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Hunan Intellectual and Development Disabilities Research Center, Changsha, Hunan 410008, China
| | - Wei-Ping Liao
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and Ministry of Education of China, Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Institute of Neuroscience, Guangzhou Medical University, Guangzhou 510260, China
| | - Yong-Hong Yi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and Ministry of Education of China, Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Institute of Neuroscience, Guangzhou Medical University, Guangzhou 510260, China
| | - Jing-Yu Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhi-Xian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Zhong Chen
- Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Department of Pharmacology, College of Pharmaceutical Sciences, School of Medicine, Zhejiang University, Hangzhou 310027, China.,Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310027, China
| | - Xiao Mao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Xin-Xiang Yan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Hong Jiang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Lu Shen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Sheng-Di Chen
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Li-Ming Zhang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, China
| | - Bei-Sha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China.,Collaborative Innovation Center for Brain Science, Shanghai 200032, China.,Collaborative Innovation Center for Genetics and Development, Shanghai 200433, China
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37
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Liu YY, Hsiao HT, Wang JCF, Liu YC, Wu SN. Parecoxib, a selective blocker of cyclooxygenase-2, directly inhibits neuronal delayed-rectifier K + current, M-type K + current and Na + current. Eur J Pharmacol 2018; 844:95-101. [PMID: 30529469 DOI: 10.1016/j.ejphar.2018.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 11/29/2018] [Accepted: 12/05/2018] [Indexed: 11/24/2022]
Abstract
Parecoxib, a prodrug of valdecoxib, is a selective inhibitor of cyclooxygenase-2 and widely used for traumatic and postoperative patients to avoid opioid-induced side effects. It is a potent analgesic and has a role in multimodal analgesic and enhanced recovery after surgery. Whether parecoxib exerts any actions on these types of ionic currents remains unclear. In this study, we investigated whether it exerts any effects on ion currents in differentiated NG108-15 neuronal cells. Cell exposure to parecoxib (1-30 μM) caused a reversible reduction in the amplitude of IK(DR) with an IC50 value of 9.7 μM. The time course for the IK(DR) inactivation in response to a long-lasting pulse was changed to the biexponential process during cell exposure to 3 μM parecoxib. Other agents known to inhibit the cyclooxygenase activity have minimal effects on IK(DR). Parecoxib enhanced the degree of excessive accumulative inhibition of IK(DR) inactivation evoked by a train of brief repetitive stimuli. This compound suppressed the amplitude of M-type K+ current. It depressed the peak amplitude of voltage-gated Na+ current with no change in the current-voltage relationship of this current. However, it did not have any effect on hyperpolarization-activated cation current. No change in the expression level of KV3.1 mRNA was detected in the presence of parecoxib. The effects of parecoxib on ion currents are direct and unrelated to its inhibition of the enzymatic activity of cyclooxygenase-2. The inhibition of these ion channels by parecoxib may partly contribute to the underlying mechanisms by which it affects neuronal function in vivo.
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Affiliation(s)
- Yuan-Yuarn Liu
- Division of Trauma, Department of Emergency, Kaohsiung Veterans General Hospital, Kaohsiung City, Taiwan
| | - Hung-Tsung Hsiao
- Department of Anesthesiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Taiwan
| | - Jeffrey Chi-Fei Wang
- Department of Anesthesiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Taiwan
| | - Yen-Chin Liu
- Department of Anesthesiology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Taiwan
| | - Sheng-Nan Wu
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan; Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan.
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38
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Wang JZ, Long C, Li KY, Xu HT, Yuan LL, Wu GY. Potent block of potassium channels by MEK inhibitor U0126 in primary cultures and brain slices. Sci Rep 2018; 8:8808. [PMID: 29892075 PMCID: PMC5995919 DOI: 10.1038/s41598-018-27235-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 05/29/2018] [Indexed: 12/05/2022] Open
Abstract
U0126 (1,4-diamino-2,3-dicyano-1,4-bis (2-aminophenylthio) butadiene), a widely used mitogen-activated protein kinase kinase (MEK) inhibitor, was found to accelerate voltage-gated K+ channel (KV) inactivation in heterologous cells expressing several types of KV. The goal of this study was to examine whether U0126 at a concentration thought to specifically inhibit MEK signaling also inhibits KV in native neurons of primary cultures or brain slices. U0126 caused a dose-dependent inhibition of both the transient (IA) and sustained (IDR) components of K+ currents in hippocampal neurons. U0126 also exhibited much higher potency on the IA and IDR than the classical KV blockers 4-aminopyridine (4-AP) and tetraethylammonium (TEA). Consistent with its inhibitory effect on KV, U0126 broadened action potential duration, profoundly affected the repolarizing phase, and dramatically reduced firing frequency in response to current pulse injections. Despite the potent and reversible action of U0126 on Kv channels, PD98059, a structurally-unrelated MEK inhibitor, did not induce such an effect, suggesting U0126 may act independently of MEK inhibition. Together, these results raise cautions for using U0126 as a specific inhibitor for studying MEK signaling in neurons; on the other hand, further studies on the blocking mechanisms of U0126 as a potent inhibitor of KV may provide useful insights into the structure-function relationship of KV in general.
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Affiliation(s)
- Jin-Zhao Wang
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Cheng Long
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
| | - Kai-Yuan Li
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Hua-Tai Xu
- Institute of Neuroscience, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai, 200031, China
| | - Li-Lian Yuan
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, 50312, USA
| | - Gang-Yi Wu
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
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39
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Shim HG, Lee YS, Kim SJ. The Emerging Concept of Intrinsic Plasticity: Activity-dependent Modulation of Intrinsic Excitability in Cerebellar Purkinje Cells and Motor Learning. Exp Neurobiol 2018; 27:139-154. [PMID: 30022866 PMCID: PMC6050419 DOI: 10.5607/en.2018.27.3.139] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 06/28/2018] [Accepted: 06/28/2018] [Indexed: 12/15/2022] Open
Abstract
What is memory? How does the brain process the sensory information and modify an organism's behavior? Many neuroscientists have focused on the activity- and experience-dependent modifications of synaptic functions in order to solve these fundamental questions in neuroscience. Recently, the plasticity of intrinsic excitability (called intrinsic plasticity) has emerged as an important element for information processing and storage in the brain. As the cerebellar Purkinje cells are the sole output neurons in the cerebellar cortex and the information is conveyed from a neuron to its relay neurons by forms of action potential firing, the modulation of the intrinsic firing activity may play a critical role in the cerebellar learning. Many voltage-gated and/or Ca2+-activated ion channels are involved in shaping the spiking output as well as integrating synaptic inputs to finely tune the cerebellar output. Recent studies suggested that the modulation of the intrinsic excitability and its plasticity in the cerebellar Purkinje cells might function as an integrator for information processing and memory formation. Moreover, the intrinsic plasticity might also determine the strength of connectivity to the sub-cortical areas such as deep cerebellar nuclei and vestibular nuclei to trigger the consolidation of the cerebellar-dependent memory by transferring the information.
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Affiliation(s)
- Hyun Geun Shim
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
- Department of Biomedical Science, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Yong-Seok Lee
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
- Department of Biomedical Science, Seoul National University College of Medicine, Seoul 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Sang Jeong Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
- Department of Biomedical Science, Seoul National University College of Medicine, Seoul 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul 03080, Korea
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40
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Regulation of Nociceptive Glutamatergic Signaling by Presynaptic Kv3.4 Channels in the Rat Spinal Dorsal Horn. J Neurosci 2018. [PMID: 29540546 DOI: 10.1523/jneurosci.3212-17.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Presynaptic voltage-gated K+ (Kv) channels in dorsal root ganglion (DRG) neurons are thought to regulate nociceptive synaptic transmission in the spinal dorsal horn. However, the Kv channel subtypes responsible for this critical role have not been identified. The Kv3.4 channel is particularly important because it is robustly expressed in DRG nociceptors, where it regulates action potential (AP) duration. Furthermore, Kv3.4 dysfunction is implicated in the pathophysiology of neuropathic pain in multiple pain models. We hypothesized that, through their ability to modulate AP repolarization, Kv3.4 channels in DRG nociceptors help to regulate nociceptive synaptic transmission. To test this hypothesis, we investigated Kv3.4 immunoreactivity (IR) in the rat cervical superficial dorsal horn (sDH) in both sexes and implemented an intact spinal cord preparation to investigate glutamatergic synaptic currents from second order neurons in the sDH under conditions that selectively inhibit the Kv3.4 current. We found presynaptic Kv3.4 IR in peptidergic and nonpeptidergic nociceptive fibers of the sDH. The Kv3.4 channel is hypersensitive to 4-aminopyridine and tetraethylammonium (TEA). Accordingly, 50 μm 4-aminopyridine and 500 μm TEA significantly prolong the AP, slow the maximum rate of repolarization in small-diameter DRG neurons, and potentiate monosynaptic excitatory postsynaptic currents (EPSCs) in dorsal horn laminae I and II through a presynaptic mechanism. In contrast, highly specific inhibitors of BK, Kv7, and Kv1 channels are less effective modulators of the AP and have little to no effect on EPSCs. The results strongly suggest that presynaptic Kv3.4 channels are major regulators of nociceptive synaptic transmission in the spinal cord.SIGNIFICANCE STATEMENT Intractable neuropathic pain can result from disease or traumatic injury and many studies have been conducted to determine the underlying pathophysiological changes. Voltage-gated ion channels, including the K+ channel Kv3.4, are dysregulated in multiple pain models. Kv3.4 channels are ubiquitously expressed in the dorsal root ganglion (DRG), where they are major regulators of DRG excitability. However, little is known about the ionic mechanisms that regulate nociceptive synaptic transmission at the level of the first synapse in the spinal cord, which is critical to pain transmission in both intact and pathological states. Here, we show that Kv3.4 channels have a significant impact on glutamatergic synaptic transmission in the dorsal horn, further illuminating its potential as a molecular pain therapeutic target.
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41
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Margas W, Ferron L, Nieto-Rostro M, Schwartz A, Dolphin AC. Effect of knockout of α2δ-1 on action potentials in mouse sensory neurons. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0430. [PMID: 27377724 PMCID: PMC4938030 DOI: 10.1098/rstb.2015.0430] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2016] [Indexed: 12/12/2022] Open
Abstract
Gene deletion of the voltage-gated calcium channel auxiliary subunit α2δ-1 has been shown previously to have a cardiovascular phenotype, and a reduction in mechano- and cold sensitivity, coupled with delayed development of neuropathic allodynia. We have also previously shown that dorsal root ganglion (DRG) neuron calcium channel currents were significantly reduced in α2δ-1 knockout mice. To extend our findings in these sensory neurons, we have examined here the properties of action potentials (APs) in DRG neurons from α2δ-1 knockout mice in comparison to their wild-type (WT) littermates, in order to dissect how the calcium channels that are affected by α2δ-1 knockout are involved in setting the duration of individual APs and their firing frequency. Our main findings are that there is reduced Ca2+ entry on single AP stimulation, particularly in the axon proximal segment, reduced AP duration and reduced firing frequency to a 400 ms stimulation in α2δ-1 knockout neurons, consistent with the expected role of voltage-gated calcium channels in these events. Furthermore, lower intracellular Ca2+ buffering also resulted in reduced AP duration, and a lower frequency of AP firing in WT neurons, mimicking the effect of α2δ-1 knockout. By contrast, we did not obtain any consistent evidence for the involvement of Ca2+-activation of large conductance calcium-activated potassium (BK) and small conductance calcium-activated potassium (SK) channels in these events. In conclusion, the reduced Ca2+ elevation as a result of single AP stimulation is likely to result from the reduced duration of the AP in α2δ-1 knockout sensory neurons. This article is part of the themed issue ‘Evolution brings Ca2+ and ATP together to control life and death’.
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Affiliation(s)
- Wojciech Margas
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Manuela Nieto-Rostro
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Arnold Schwartz
- College of Medicine, University of Cincinnati, Cincinnati, OH 45267-0557, USA
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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42
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SK Channels Regulate Resting Properties and Signaling Reliability of a Developing Fast-Spiking Neuron. J Neurosci 2017; 37:10738-10747. [PMID: 28982705 DOI: 10.1523/jneurosci.1243-17.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 09/07/2017] [Accepted: 09/27/2017] [Indexed: 11/21/2022] Open
Abstract
Reliable and precise signal transmission is essential in circuits of the auditory brainstem to encode timing with submillisecond accuracy. Globular bushy cells reliably and faithfully transfer spike signals to the principal neurons of the medial nucleus of the trapezoid body (MNTB) through the giant glutamatergic synapse, the calyx of Held. Thus, the MNTB works as a relay nucleus that preserves the temporal pattern of firing at high frequency. Using whole-cell patch-clamp recordings, we observed a K+ conductance mediated by small-conductance calcium-activated potassium (SK) channels in the MNTB neurons from rats of either sex. SK channels were activated by intracellular Ca2+ sparks and mediated spontaneous transient outward currents in developing MNTB neurons. SK channels were also activated by Ca2+ influx through voltage-gated Ca2+ channels and synaptically activated NMDA receptors. Blocking SK channels with apamin depolarized the resting membrane potential, reduced resting conductance, and affected the responsiveness of MNTB neurons to signal inputs. Moreover, SK channels were activated by action potentials and affected the spike afterhyperpolarization. Blocking SK channels disrupted the one-to-one signal transmission from presynaptic calyces to postsynaptic MNTB neurons and induced extra postsynaptic action potentials in response to presynaptic firing. These data reveal that SK channels play crucial roles in regulating the resting properties and maintaining reliable signal transmission of MNTB neurons.SIGNIFICANCE STATEMENT Reliable and precise signal transmission is required in auditory brainstem circuits to localize the sound source. The calyx of Held synapse in the mammalian medial nucleus of the trapezoid body (MNTB) plays an important role in sound localization. We investigated the potassium channels that shape the reliability of signal transfer across the calyceal synapse and observed a potassium conductance mediated by small-conductance calcium-activated potassium (SK) channels in rat MNTB principal neurons. We found that SK channels are tonically activated and contribute to the resting membrane properties of MNTB neurons. Interestingly, SK channels are transiently activated by calcium sparks and calcium influx during action potentials and control the one-to-one signal transmission from presynaptic calyces to postsynaptic MNTB neurons.
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Alteration of Neuronal Excitability and Short-Term Synaptic Plasticity in the Prefrontal Cortex of a Mouse Model of Mental Illness. J Neurosci 2017; 37:4158-4180. [PMID: 28283561 DOI: 10.1523/jneurosci.4345-15.2017] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 02/17/2017] [Accepted: 02/22/2017] [Indexed: 01/28/2023] Open
Abstract
Using a genetic mouse model that faithfully recapitulates a DISC1 genetic alteration strongly associated with schizophrenia and other psychiatric disorders, we examined the impact of this mutation within the prefrontal cortex. Although cortical layering, cytoarchitecture, and proteome were found to be largely unaffected, electrophysiological examination of the mPFC revealed both neuronal hyperexcitability and alterations in short-term synaptic plasticity consistent with enhanced neurotransmitter release. Increased excitability of layer II/III pyramidal neurons was accompanied by consistent reductions in voltage-activated potassium currents near the action potential threshold as well as by enhanced recruitment of inputs arising from superficial layers to layer V. We further observed reductions in both the paired-pulse ratios and the enhanced short-term depression of layer V synapses arising from superficial layers consistent with enhanced neurotransmitter release at these synapses. Recordings from layer II/III pyramidal neurons revealed action potential widening that could account for enhanced neurotransmitter release. Significantly, we found that reduced functional expression of the voltage-dependent potassium channel subunit Kv1.1 substantially contributes to both the excitability and short-term plasticity alterations that we observed. The underlying dysregulation of Kv1.1 expression was attributable to cAMP elevations in the PFC secondary to reduced phosphodiesterase 4 activity present in Disc1 deficiency and was rescued by pharmacological blockade of adenylate cyclase. Our results demonstrate a potentially devastating impact of Disc1 deficiency on neural circuit function, partly due to Kv1.1 dysregulation that leads to a dual dysfunction consisting of enhanced neuronal excitability and altered short-term synaptic plasticity.SIGNIFICANCE STATEMENT Schizophrenia is a profoundly disabling psychiatric illness with a devastating impact not only upon the afflicted but also upon their families and the broader society. Although the underlying causes of schizophrenia remain poorly understood, a growing body of studies has identified and strongly implicated various specific risk genes in schizophrenia pathogenesis. Here, using a genetic mouse model, we explored the impact of one of the most highly penetrant schizophrenia risk genes, DISC1, upon the medial prefrontal cortex, the region believed to be most prominently dysfunctional in schizophrenia. We found substantial derangements in both neuronal excitability and short-term synaptic plasticity-parameters that critically govern neural circuit information processing-suggesting that similar changes may critically, and more broadly, underlie the neural computational dysfunction prototypical of schizophrenia.
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Mukunda CL, Narayanan R. Degeneracy in the regulation of short-term plasticity and synaptic filtering by presynaptic mechanisms. J Physiol 2017; 595:2611-2637. [PMID: 28026868 DOI: 10.1113/jp273482] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 12/13/2016] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS We develop a new biophysically rooted, physiologically constrained conductance-based synaptic model to mechanistically account for short-term facilitation and depression, respectively through residual calcium and transmitter depletion kinetics. We address the specific question of how presynaptic components (including voltage-gated ion channels, pumps, buffers and release-handling mechanisms) and interactions among them define synaptic filtering and short-term plasticity profiles. Employing global sensitivity analyses (GSAs), we show that near-identical synaptic filters and short-term plasticity profiles could emerge from disparate presynaptic parametric combinations with weak pairwise correlations. Using virtual knockout models, a technique to address the question of channel-specific contributions within the GSA framework, we unveil the differential and variable impact of each ion channel on synaptic physiology. Our conclusions strengthen the argument that parametric and interactional complexity in biological systems should not be viewed from the limited curse-of-dimensionality standpoint, but from the evolutionarily advantageous perspective of providing functional robustness through degeneracy. ABSTRACT Information processing in neurons is known to emerge as a gestalt of pre- and post-synaptic filtering. However, the impact of presynaptic mechanisms on synaptic filters has not been quantitatively assessed. Here, we developed a biophysically rooted, conductance-based model synapse that was endowed with six different voltage-gated ion channels, calcium pumps, calcium buffer and neurotransmitter-replenishment mechanisms in the presynaptic terminal. We tuned our model to match the short-term plasticity profile and band-pass structure of Schaffer collateral synapses, and performed sensitivity analyses to demonstrate that presynaptic voltage-gated ion channels regulated synaptic filters through changes in excitability and associated calcium influx. These sensitivity analyses also revealed that calcium- and release-control mechanisms were effective regulators of synaptic filters, but accomplished this without changes in terminal excitability or calcium influx. Next, to perform global sensitivity analysis, we generated 7000 randomized models spanning 15 presynaptic parameters, and computed eight different physiological measurements in each of these models. We validated these models by applying experimentally obtained bounds on their measurements, and found 104 (∼1.5%) models to match the validation criteria for all eight measurements. Analysing these valid models, we demonstrate that analogous synaptic filters emerge from disparate combinations of presynaptic parameters exhibiting weak pairwise correlations. Finally, using virtual knockout models, we establish the variable and differential impact of different presynaptic channels on synaptic filters, underlining the critical importance of interactions among different presynaptic components in defining synaptic physiology. Our results have significant implications for protein-localization strategies required for physiological robustness and for degeneracy in long-term synaptic plasticity profiles.
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Affiliation(s)
- Chinmayee L Mukunda
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
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A Neural Mass Computational Framework to Study Synaptic Mechanisms Underlying Alpha and Theta Rhythms. COMPUTATIONAL NEUROLOGY AND PSYCHIATRY 2017. [DOI: 10.1007/978-3-319-49959-8_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Rowan MJM, DelCanto G, Yu JJ, Kamasawa N, Christie JM. Synapse-Level Determination of Action Potential Duration by K(+) Channel Clustering in Axons. Neuron 2016; 91:370-83. [PMID: 27346528 DOI: 10.1016/j.neuron.2016.05.035] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 03/13/2016] [Accepted: 05/23/2016] [Indexed: 10/21/2022]
Abstract
In axons, an action potential (AP) is thought to be broadcast as an unwavering binary pulse over its arbor, driving neurotransmission uniformly at release sites. Yet by recording from axons of cerebellar stellate cell (SC) interneurons, we show that AP width varies between presynaptic bouton sites, even within the same axon branch. The varicose geometry of SC boutons alone does not impose differences in spike duration. Rather, axonal patching revealed heterogeneous peak conductance densities of currents mediated mainly by fast-activating Kv3-type potassium channels, with clustered hotspots at boutons and restricted expression at adjoining shafts. Blockade of Kv channels at individual boutons indicates that currents immediately local to a release site direct spike repolarization at that location. Thus, the clustered arrangement and variable expression density of Kv3 channels at boutons are key determinants underlying compartmentalized control of AP width in a near synapse-by-synapse manner, multiplying the signaling capacity of these structures.
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Affiliation(s)
- Matthew J M Rowan
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Gina DelCanto
- Wilkes Honors Campus of Florida Atlantic University, Jupiter, FL 33405, USA
| | - Jianqing J Yu
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Naomi Kamasawa
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Jason M Christie
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA.
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KV1 and KV3 Potassium Channels Identified at Presynaptic Terminals of the Corticostriatal Synapses in Rat. Neural Plast 2016; 2016:8782518. [PMID: 27379187 PMCID: PMC4917754 DOI: 10.1155/2016/8782518] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/12/2016] [Accepted: 05/16/2016] [Indexed: 12/19/2022] Open
Abstract
In the last years it has been increasingly clear that KV-channel activity modulates neurotransmitter release. The subcellular localization and composition of potassium channels are crucial to understanding its influence on neurotransmitter release. To investigate the role of KV in corticostriatal synapses modulation, we combined extracellular recording of population-spike and pharmacological blockage with specific and nonspecific blockers to identify several families of KV channels. We induced paired-pulse facilitation (PPF) and studied the changes in paired-pulse ratio (PPR) before and after the addition of specific KV blockers to determine whether particular KV subtypes were located pre- or postsynaptically. Initially, the presence of KV channels was tested by exposing brain slices to tetraethylammonium or 4-aminopyridine; in both cases we observed a decrease in PPR that was dose dependent. Further experiments with tityustoxin, margatoxin, hongotoxin, agitoxin, dendrotoxin, and BDS-I toxins all rendered a reduction in PPR. In contrast heteropodatoxin and phrixotoxin had no effect. Our results reveal that corticostriatal presynaptic KV channels have a complex stoichiometry, including heterologous combinations KV1.1, KV1.2, KV1.3, and KV1.6 isoforms, as well as KV3.4, but not KV4 channels. The variety of KV channels offers a wide spectrum of possibilities to regulate neurotransmitter release, providing fine-tuning mechanisms to modulate synaptic strength.
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Correlation between the increased release of catecholamines evoked by local anesthetics and their analgesic and adverse effects: Role of K + channel inhibition. Brain Res Bull 2016; 124:21-6. [DOI: 10.1016/j.brainresbull.2016.03.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/11/2016] [Accepted: 03/16/2016] [Indexed: 01/05/2023]
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Schorova L, Martin S. Sumoylation in Synaptic Function and Dysfunction. Front Synaptic Neurosci 2016; 8:9. [PMID: 27199730 PMCID: PMC4848311 DOI: 10.3389/fnsyn.2016.00009] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/08/2016] [Indexed: 12/18/2022] Open
Abstract
Sumoylation has recently emerged as a key post-translational modification involved in many, if not all, biological processes. Small Ubiquitin-like Modifier (SUMO) polypeptides are covalently attached to specific lysine residues of target proteins through a dedicated enzymatic pathway. Disruption of the SUMO enzymatic pathway in the developing brain leads to lethality indicating that this process exerts a central role during embryonic and post-natal development. However, little is still known regarding how this highly dynamic protein modification is regulated in the mammalian brain despite an increasing number of data implicating sumoylated substrates in synapse formation, synaptic communication and plasticity. The aim of this review is therefore to briefly describe the enzymatic SUMO pathway and to give an overview of our current knowledge on the function and dysfunction of protein sumoylation at the mammalian synapse.
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Affiliation(s)
- Lenka Schorova
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique (UMR7275), University of Nice-Sophia-Antipolis, Laboratory of Excellence "Network for Innovation on Signal Transduction, Pathways in Life Sciences" Valbonne, France
| | - Stéphane Martin
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique (UMR7275), University of Nice-Sophia-Antipolis, Laboratory of Excellence "Network for Innovation on Signal Transduction, Pathways in Life Sciences" Valbonne, France
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