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Oniani T, Vinnenberg L, Chaudhary R, Schreiber JA, Riske K, Williams B, Pape HC, White JA, Junker A, Seebohm G, Meuth SG, Hundehege P, Budde T, Zobeiri M. Effects of Axonal Demyelination, Inflammatory Cytokines and Divalent Cation Chelators on Thalamic HCN Channels and Oscillatory Bursting. Int J Mol Sci 2022; 23:ijms23116285. [PMID: 35682964 PMCID: PMC9181513 DOI: 10.3390/ijms23116285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 12/13/2022] Open
Abstract
Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that is characterized by the progressive loss of oligodendrocytes and myelin and is associated with thalamic dysfunction. Cuprizone (CPZ)-induced general demyelination in rodents is a valuable model for studying different aspects of MS pathology. CPZ feeding is associated with the altered distribution and expression of different ion channels along neuronal somata and axons. However, it is largely unknown whether the copper chelator CPZ directly influences ion channels. Therefore, we assessed the effects of different divalent cations (copper; zinc) and trace metal chelators (EDTA; Tricine; the water-soluble derivative of CPZ, BiMPi) on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that are major mediators of thalamic function and pathology. In addition, alterations of HCN channels induced by CPZ treatment and MS-related proinflammatory cytokines (IL-1β; IL-6; INF-α; INF-β) were characterized in C57Bl/6J mice. Thus, the hyperpolarization-activated inward current (Ih) was recorded in thalamocortical (TC) neurons and heterologous expression systems (mHCN2 expressing HEK cells; hHCN4 expressing oocytes). A number of electrophysiological characteristics of Ih (potential of half-maximal activation (V0.5); current density; activation kinetics) were unchanged following the extracellular application of trace metals and divalent cation chelators to native neurons, cell cultures or oocytes. Mice were fed a diet containing 0.2% CPZ for 35 days, resulting in general demyelination in the brain. Withdrawal of CPZ from the diet resulted in rapid remyelination, the effects of which were assessed at three time points after stopping CPZ feeding (Day1, Day7, Day25). In TC neurons, Ih was decreased on Day1 and Day25 and revealed a transient increased availability on Day7. In addition, we challenged naive TC neurons with INF-α and IL-1β. It was found that Ih parameters were differentially altered by the application of the two cytokines to thalamic cells, while IL-1β increased the availability of HCN channels (depolarized V0.5; increased current density) and the excitability of TC neurons (depolarized resting membrane potential (RMP); increased the number of action potentials (APs); produced a larger voltage sag; promoted higher input resistance; increased the number of burst spikes; hyperpolarized the AP threshold), INF-α mediated contrary effects. The effect of cytokine modulation on thalamic bursting was further assessed in horizontal slices and a computational model of slow thalamic oscillations. Here, IL-1β and INF-α increased and reduced oscillatory bursting, respectively. We conclude that HCN channels are not directly modulated by trace metals and divalent cation chelators but are subject to modulation by different MS-related cytokines.
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Affiliation(s)
- Tengiz Oniani
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - Laura Vinnenberg
- Department of Neurology with Institute of Translational Neurology, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany; (L.V.); (P.H.)
| | - Rahul Chaudhary
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - Julian A. Schreiber
- Institute of Pharmaceutical and Medicinal Chemistry, Westfälische Wilhelms-Universität, Corren-Str. 48, D-48149 Münster, Germany;
- Cellular Electrophysiology and Molecular Biology, Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany;
| | - Kathrin Riske
- European Institute for Molecular Imaging (EIMI), Westfälische Wilhelms-Universität, Waldeyer-Str. 15, D-48149 Münster, Germany; (K.R.); (A.J.)
| | - Brandon Williams
- Center for Systems Neuroscience, Neurophotonics Center, Department of Biomedical Engineering, Boston University, 610 Commonwealth Ave., Boston, MA 02215, USA; (B.W.); (J.A.W.)
| | - Hans-Christian Pape
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
| | - John A. White
- Center for Systems Neuroscience, Neurophotonics Center, Department of Biomedical Engineering, Boston University, 610 Commonwealth Ave., Boston, MA 02215, USA; (B.W.); (J.A.W.)
| | - Anna Junker
- European Institute for Molecular Imaging (EIMI), Westfälische Wilhelms-Universität, Waldeyer-Str. 15, D-48149 Münster, Germany; (K.R.); (A.J.)
| | - Guiscard Seebohm
- Cellular Electrophysiology and Molecular Biology, Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Robert-Koch-Str. 45, D-48149 Münster, Germany;
| | - Sven G. Meuth
- Neurology Clinic, University Clinic Düsseldorf, Moorenstraße 5, D-40225 Düsseldorf, Germany;
| | - Petra Hundehege
- Department of Neurology with Institute of Translational Neurology, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany; (L.V.); (P.H.)
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
- Correspondence:
| | - Mehrnoush Zobeiri
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149 Münster, Germany; (T.O.); (R.C.); (H.-C.P.); (M.Z.)
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Biophysical analysis of an HCN1 epilepsy variant suggests a critical role for S5 helix Met-305 in voltage sensor to pore domain coupling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:156-172. [PMID: 34298002 DOI: 10.1016/j.pbiomolbio.2021.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 06/30/2021] [Accepted: 07/13/2021] [Indexed: 12/22/2022]
Abstract
Hyperpolarization-gated, cyclic nucleotide-activated (HCN1-4) channels are inwardly rectifying cation channels that display voltage dependent activation and de-activation. Pathogenic variants in HCN1 are associated with severe developmental and epileptic encephalopathies including the de novo HCN1 M305L variant. M305 is located in the S5 domain that is implicated in coupling voltage sensor domain movement to pore opening. This variant lacks voltage-dependent activation and de-activation and displays normal cation selectivity. To elucidate the impact of the mutation on the channel structure-function relations, molecular dynamics simulations of the wild type and mutant homotetramers were compared and identified a sulphur-aromatic interaction between M305 and F389 that contributes to the coupling of the voltage-sensing domain to the pore domain. To mimic the heterozygous condition as a heterotetrameric channel assembly, Xenopus oocytes were co-injected with various ratios of wild-type and mutant subunit cRNAs and the biophysical properties of channels with different subunit stoichiometries were determined. The results showed that a single mutated subunit was sufficient to significantly disrupt the voltage dependence of activation. The functional data were qualitatively consistent with predictions of a model that assumes independent activation of the voltage sensing domains allosterically controlling the closed to open transition of the pore. Overall, the M305L mutation results in an HCN1 channel that lacks voltage dependence and facilitates excitatory cation flow at membrane potentials that would normally close the channel. Our findings provide molecular insights into HCN1 channels and reveal the structural and biophysical basis of the severe epilepsy phenotype associated with the M305L mutation.
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Martens H, Stumpff F. Assessment of magnesium intake according to requirement in dairy cows. J Anim Physiol Anim Nutr (Berl) 2019; 103:1023-1029. [PMID: 31025783 DOI: 10.1111/jpn.13106] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 02/04/2019] [Accepted: 03/27/2019] [Indexed: 11/28/2022]
Abstract
To date, no specific hormonal regulation system has been identified for homoeostatic control of the essential mineral Mg. In cattle, the maintenance of physiological plasma Mg concentration depends on gastrointestinal absorption, primarily from the rumen, which serves as a pool for covering the requirement. Whereas a possible surplus (absorption greater than requirement) is rapidly excreted by the kidneys, a shortage (absorption lower than requirement) cannot be compensated for by mobilization from the large Mg pool in bones or soft tissue, so that the maintenance of the necessary physiological Mg concentration in plasma relies on continuous and sufficient absorption. Our knowledge concerning the site and mechanisms of Mg absorption has improved during the last few decades, and meta-analyses of the absorption of Mg in dairy cows have shown that the K content has a pronounced negative effect on Mg digestibility. The current recommendations of Mg intake propose a constant percentage of Mg and emphasize the depressive effect of high potassium (K) intake on Mg absorption. The current knowledge about the antagonism between K intake and Mg absorption allows a more flexible solution which includes the K content of the diet. An assessment of Mg intake is proposed that incorporates the improved knowledge of Mg absorption, metabolism and requirement. Within this framework, an equation is derived that allows a prediction of the amount of Mg required to compensate for dietary K content, the goal being to avoid both possible undernutrition or an unnecessary surplus of dietary Mg.
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Affiliation(s)
- Holger Martens
- Institute of Veterinary Physiology, Freie Universität Berlin, Berlin, Germany
| | - Friederike Stumpff
- Institute of Veterinary Physiology, Freie Universität Berlin, Berlin, Germany
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Luo P, He G, Liu D. HCN channels: New targets for the design of an antidepressant with rapid effects. J Affect Disord 2019; 245:764-770. [PMID: 30448761 DOI: 10.1016/j.jad.2018.11.081] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 10/22/2018] [Accepted: 11/11/2018] [Indexed: 12/18/2022]
Abstract
BACKGROUND Major depressive disorder (MDD) is a prevalent neuropsychiatric disease that carries a staggering global burden. Although numerous antidepressants are available on the market, unfortunately, many patients die by committing suicide as a result of the therapeutic lag between treatment initiation and the improvement of depressive symptoms. This therapeutic lag highlights the need for new antidepressants that provide rapid relief of depressive symptoms. METHOD In this review, we discuss the seminal researches on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in animal models of depression and highlight the substantial evidence supporting the development of rapid-acting antidepressants targeting HCN channels. RESULTS HCN channels are associated with the risk of depression and targeting HCN channels or its auxiliary subunit tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) function may exert a rapid antidepressant-like effect. CONCLUSIONS Compounds acting on HCN subunits or the TRIP8b-HCN interaction site may be excellent candidates for development into effective drugs with rapid antidepressant action.
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Affiliation(s)
- Pan Luo
- Department of Pharmacy, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - GuoFang He
- Department of Pharmacy, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
| | - Dong Liu
- Department of Pharmacy, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Abstract
Magnesium (Mg2+) is an essential mineral without known specific regulatory mechanisms. In ruminants, plasma Mg2+ concentration depends primarily on the balance between Mg2+ absorption and Mg2+ excretion. The primary site of Mg2+ absorption is the rumen, where Mg2+ is apically absorbed by both potential-dependent and potential-independent uptake mechanisms, reflecting involvement of ion channels and electroneutral transporters, respectively. Transport is energised in a secondary active manner by a basolateral Na+/Mg2+ exchanger. Ruminal transport of Mg2+ is significantly influenced by a variety of factors such as high K+ concentration, sudden increases of ammonia, pH, and the concentration of SCFA. Impaired Mg2+ absorption in the rumen is not compensated for by increased transport in the small or large intestine. While renal excretion can be adjusted to compensate precisely for any surplus in Mg2+ uptake, a shortage in dietary Mg2+ cannot be compensated for either via skeletal mobilisation of Mg2+ or via up-regulation of ruminal absorption. In such situations, hypomagnesaemia will lead to decrease of a Mg2+ in the cerebrospinal fluid and clinical manifestations of tetany. Improved knowledge concerning the factors governing Mg2+ homeostasis will allow reliable recommendations for an adequate Mg2+ intake and for the avoidance of possible disturbances. Future research should clarify the molecular identity of the suggested Mg2+ transport proteins and the regulatory mechanisms controlling renal Mg excretion as parameters influencing Mg2+ homeostasis.
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Beining M, Mongiat LA, Schwarzacher SW, Cuntz H, Jedlicka P. T2N as a new tool for robust electrophysiological modeling demonstrated for mature and adult-born dentate granule cells. eLife 2017; 6:e26517. [PMID: 29165247 PMCID: PMC5737656 DOI: 10.7554/elife.26517] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 11/21/2017] [Indexed: 12/18/2022] Open
Abstract
Compartmental models are the theoretical tool of choice for understanding single neuron computations. However, many models are incomplete, built ad hoc and require tuning for each novel condition rendering them of limited usability. Here, we present T2N, a powerful interface to control NEURON with Matlab and TREES toolbox, which supports generating models stable over a broad range of reconstructed and synthetic morphologies. We illustrate this for a novel, highly detailed active model of dentate granule cells (GCs) replicating a wide palette of experiments from various labs. By implementing known differences in ion channel composition and morphology, our model reproduces data from mouse or rat, mature or adult-born GCs as well as pharmacological interventions and epileptic conditions. This work sets a new benchmark for detailed compartmental modeling. T2N is suitable for creating robust models useful for large-scale networks that could lead to novel predictions. We discuss possible T2N application in degeneracy studies.
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Affiliation(s)
- Marcel Beining
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck SocietyFrankfurtGermany
- Frankfurt Institute for Advanced StudiesFrankfurtGermany
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe UniversityFrankfurtGermany
- Faculty of BiosciencesGoethe UniversityFrankfurtGermany
| | - Lucas Alberto Mongiat
- Instituto de Investigación en Biodiversidad y MedioambienteUniversidad Nacional del Comahue-CONICETSan Carlos de BarilocheArgentina
| | | | - Hermann Cuntz
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck SocietyFrankfurtGermany
- Frankfurt Institute for Advanced StudiesFrankfurtGermany
| | - Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe UniversityFrankfurtGermany
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Limon A, Mamdani F, Hjelm BE, Vawter MP, Sequeira A. Targets of polyamine dysregulation in major depression and suicide: Activity-dependent feedback, excitability, and neurotransmission. Neurosci Biobehav Rev 2016; 66:80-91. [PMID: 27108532 DOI: 10.1016/j.neubiorev.2016.04.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 04/09/2016] [Accepted: 04/13/2016] [Indexed: 01/19/2023]
Abstract
Major depressive disorder (MDD) is a leading cause of disability worldwide characterized by altered neuronal activity in brain regions involved in the control of stress and emotion. Although multiple lines of evidence suggest that altered stress-coping mechanisms underlie the etiology of MDD, the homeostatic control of neuronal excitability in MDD at the molecular level is not well established. In this review, we examine past and current evidence implicating dysregulation of the polyamine system as a central factor in the homeostatic response to stress and the etiology of MDD. We discuss the cellular effects of abnormal metabolism of polyamines in the context of their role in sensing and modulation of neuronal, electrical, and synaptic activity. Finally, we discuss evidence supporting an allostatic model of depression based on a chronic elevation in polyamine levels resulting in self-sustained stress response mechanisms maintained by maladaptive homeostatic mechanisms.
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Affiliation(s)
- Agenor Limon
- Functional Genomics Laboratory, Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92627, USA
| | - Firoza Mamdani
- Functional Genomics Laboratory, Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92627, USA
| | - Brooke E Hjelm
- Functional Genomics Laboratory, Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92627, USA
| | - Marquis P Vawter
- Functional Genomics Laboratory, Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92627, USA
| | - Adolfo Sequeira
- Functional Genomics Laboratory, Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92627, USA.
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Gamo NJ, Lur G, Higley MJ, Wang M, Paspalas CD, Vijayraghavan S, Yang Y, Ramos BP, Peng K, Kata A, Boven L, Lin F, Roman L, Lee D, Arnsten AF. Stress Impairs Prefrontal Cortical Function via D1 Dopamine Receptor Interactions With Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels. Biol Psychiatry 2015; 78:860-70. [PMID: 25731884 PMCID: PMC4524795 DOI: 10.1016/j.biopsych.2015.01.009] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 01/19/2015] [Accepted: 01/22/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND Psychiatric disorders such as schizophrenia are worsened by stress, and working memory deficits are often a central feature of illness. Working memory is mediated by the persistent firing of prefrontal cortical (PFC) pyramidal neurons. Stress impairs working memory via high levels of dopamine D1 receptor (D1R) activation of cyclic adenosine monophosphate signaling, which reduces PFC neuronal firing. The current study examined whether D1R-cyclic adenosine monophosphate signaling reduces neuronal firing and impairs working memory by increasing the open state of hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels, which are concentrated on dendritic spines where PFC pyramidal neurons interconnect. METHODS A variety of methods were employed to test this hypothesis: dual immunoelectron microscopy localized D1R and HCN channels, in vitro recordings tested for D1R actions on HCN channel current, while recordings in monkeys performing a working memory task tested for D1R-HCN channel interactions in vivo. Finally, cognitive assessments following intra-PFC infusions of drugs examined D1R-HCN channel interactions on working memory performance. RESULTS Immunoelectron microscopy confirmed D1R colocalization with HCN channels near excitatory-like synapses on dendritic spines in primate PFC. Mouse PFC slice recordings demonstrated that D1R stimulation increased HCN channel current, while local HCN channel blockade in primate PFC protected task-related firing from D1R-mediated suppression. D1R stimulation in rat or monkey PFC impaired working memory performance, while HCN channel blockade in PFC prevented this impairment in rats exposed to either stress or D1R stimulation. CONCLUSIONS These findings suggest that D1R stimulation or stress weakens PFC function via opening of HCN channels at network synapses.
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Affiliation(s)
- Nao J. Gamo
- Department of Neurobiology, Yale University, New Haven, CT
| | - Gyorgy Lur
- Department of Neurobiology, Yale University, New Haven, CT,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University, New Haven, CT
| | - Michael J. Higley
- Department of Neurobiology, Yale University, New Haven, CT,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University, New Haven, CT
| | - Min Wang
- Department of Neurobiology, Yale University, New Haven, CT
| | | | | | - Yang Yang
- Department of Neurobiology, Yale University, New Haven, CT
| | - Brian P. Ramos
- Department of Neurobiology, Yale University, New Haven, CT
| | - Kathy Peng
- Department of Neurobiology, Yale University, New Haven, CT
| | - Anna Kata
- Department of Neurobiology, Yale University, New Haven, CT
| | - Lindsay Boven
- Department of Neurobiology, Yale University, New Haven, CT
| | - Faith Lin
- Department of Neurobiology, Yale University, New Haven, CT
| | - Lisette Roman
- Department of Neurobiology, Yale University, New Haven, CT
| | - Daeyeol Lee
- Department of Neurobiology, Yale University, New Haven, CT
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Wemhöner K, Kanyshkova T, Silbernagel N, Fernandez-Orth J, Bittner S, Kiper AK, Rinné S, Netter MF, Meuth SG, Budde T, Decher N. An N-terminal deletion variant of HCN1 in the epileptic WAG/Rij strain modulates HCN current densities. Front Mol Neurosci 2015; 8:63. [PMID: 26578877 PMCID: PMC4630678 DOI: 10.3389/fnmol.2015.00063] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 10/13/2015] [Indexed: 11/26/2022] Open
Abstract
Rats of the Wistar Albino Glaxo/Rij (WAG/Rij) strain show symptoms resembling human absence epilepsy. Thalamocortical neurons of WAG/Rij rats are characterized by an increased HCN1 expression, a negative shift in Ih activation curve, and an altered responsiveness of Ih to cAMP. We cloned HCN1 channels from rat thalamic cDNA libraries of the WAG/Rij strain and found an N-terminal deletion of 37 amino acids. In addition, WAG-HCN1 has a stretch of six amino acids, directly following the deletion, where the wild-type sequence (GNSVCF) is changed to a polyserine motif. These alterations were found solely in thalamus mRNA but not in genomic DNA. The truncated WAG-HCN1 was detected late postnatal in WAG/Rij rats and was not passed on to rats obtained from pairing WAG/Rij and non-epileptic August Copenhagen Irish rats. Heterologous expression in Xenopus oocytes revealed 2.2-fold increased current amplitude of WAG-HCN1 compared to rat HCN1. While WAG-HCN1 channels did not have altered current kinetics or changed regulation by protein kinases, fluorescence imaging revealed a faster and more pronounced surface expression of WAG-HCN1. Using co-expression experiments, we found that WAG-HCN1 channels suppress heteromeric HCN2 and HCN4 currents. Moreover, heteromeric channels of WAG-HCN1 with HCN2 have a reduced cAMP sensitivity. Functional studies revealed that the gain-of-function of WAG-HCN1 is not caused by the N-terminal deletion alone, thus requiring a change of the N-terminal GNSVCF motif. Our findings may help to explain previous observations in neurons of the WAG/Rij strain and indicate that WAG-HCN1 may contribute to the genesis of absence seizures in WAG/Rij rats.
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Affiliation(s)
- Konstantin Wemhöner
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
| | - Tatyana Kanyshkova
- Institute for Physiology I, Westfälische Wilhelms-Universität Münster, Germany
| | - Nicole Silbernagel
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
| | | | - Stefan Bittner
- Department of Neurology, University Medical Center, Johannes Gutenberg-University Mainz Mainz, Germany
| | - Aytug K Kiper
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
| | - Susanne Rinné
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
| | - Michael F Netter
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
| | - Sven G Meuth
- Department of Neurology, Westfälische Wilhelms-Universität Münster, Germany
| | - Thomas Budde
- Institute for Physiology I, Westfälische Wilhelms-Universität Münster, Germany
| | - Niels Decher
- Institute for Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg Marburg, Germany
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Lyashchenko AK, Redd KJ, Goldstein PA, Tibbs GR. cAMP control of HCN2 channel Mg2+ block reveals loose coupling between the cyclic nucleotide-gating ring and the pore. PLoS One 2014; 9:e101236. [PMID: 24983358 PMCID: PMC4077740 DOI: 10.1371/journal.pone.0101236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 06/04/2014] [Indexed: 12/24/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na+-K+ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6 albeit this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg2+ which blocks the open channel pore and blunts the inhibitory effect of outward K+ flux. Here, we show that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg2+ block. A combination of experimental and simulation studies demonstrates that agonist acceleration of block is mediated via acceleration of the blocking reaction itself rather than as a secondary consequence of the cAMP enhancement of channel opening. These results suggest that the activation status of the gating ring and the open state of the pore are not coupled in an obligate manner (as required by the often invoked Monod-Wyman-Changeux allosteric model) but couple more loosely (as envisioned in a modular model of protein activation). Importantly, the emergence of second messenger sensitivity of open channel rectification suggests that loose coupling may have an unexpected consequence: it may endow these erstwhile “slow” channels with an ability to exert voltage and ligand-modulated control over cellular excitability on the fastest of physiologically relevant time scales.
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Affiliation(s)
- Alex K. Lyashchenko
- Department of Anesthesiology, Columbia University, New York, New York, United States of America
| | - Kacy J. Redd
- Department of Neuroscience, Columbia University, New York, New York, United States of America
| | - Peter A. Goldstein
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York, United States of America
| | - Gareth R. Tibbs
- Department of Anesthesiology, Columbia University, New York, New York, United States of America
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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11
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Gancedo JM. Biological roles of cAMP: variations on a theme in the different kingdoms of life. Biol Rev Camb Philos Soc 2013; 88:645-68. [PMID: 23356492 DOI: 10.1111/brv.12020] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 12/19/2012] [Accepted: 12/20/2012] [Indexed: 12/18/2022]
Abstract
Cyclic AMP (cAMP) plays a key regulatory role in most types of cells; however, the pathways controlled by cAMP may present important differences between organisms and between tissues within a specific organism. Changes in cAMP levels are caused by multiple triggers, most affecting adenylyl cyclases, the enzymes that synthesize cAMP. Adenylyl cyclases form a large and diverse family including soluble forms and others with one or more transmembrane domains. Regulatory mechanisms for the soluble adenylyl cyclases involve either interaction with diverse proteins, as happens in Escherichia coli or yeasts, or with calcium or bicarbonate ions, as occurs in mammalian cells. The transmembrane cyclases can be regulated by a variety of proteins, among which the α subunit and the βγ complex from G proteins coupled to membrane receptors are prominent. cAMP levels also are controlled by the activity of phosphodiesterases, enzymes that hydrolyze cAMP. Phosphodiesterases can be regulated by cAMP, cGMP or calcium-calmodulin or by phosphorylation by different protein kinases. Regulation through cAMP depends on its binding to diverse proteins, its proximal targets, this in turn causing changes in a variety of distal targets. Specifically, binding of cAMP to regulatory subunits of cAMP-dependent protein kinases (PKAs) affects the activity of substrates of PKA, binding to exchange proteins directly activated by cAMP (Epac) regulates small GTPases, binding to transcription factors such as the cAMP receptor protein (CRP) or the virulence factor regulator (Vfr) modifies the rate of transcription of certain genes, while cAMP binding to ion channels modulates their activity directly. Further studies on cAMP signalling will have important implications, not only for advancing fundamental knowledge but also for identifying targets for the development of new therapeutic agents.
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Affiliation(s)
- Juana M Gancedo
- Department of Metabolism and Cell Signalling, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid 28029, Spain.
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12
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Wu S, Gao W, Xie C, Xu X, Vorvis C, Marni F, Hackett AR, Liu Q, Zhou L. Inner activation gate in S6 contributes to the state-dependent binding of cAMP in full-length HCN2 channel. ACTA ACUST UNITED AC 2012; 140:29-39. [PMID: 22689828 PMCID: PMC3382721 DOI: 10.1085/jgp.201110749] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recently, applications of the patch-clamp fluorometry (PCF) technique in studies of cyclic nucleotide-gated (CNG) and hyperpolarization-activated, cyclic nucleotide-regulated (HCN) channels have provided direct evidence for the long-held notion that ligands preferably bind to and stabilize these channels in an open state. This state-dependent ligand-channel interaction involves contributions from not only the ligand-binding domain but also other discrete structural elements within the channel protein. This insight led us to investigate whether the pore of the HCN channel plays a role in the ligand-whole channel interaction. We used three well-characterized HCN channel blockers to probe the ion-conducting passage. The PCF technique was used to simultaneously monitor channel activity and cAMP binding. Two ionic blockers, Cs(+) and Mg(2+), effectively block channel conductance but have no obvious effect on cAMP binding. Surprisingly, ZD7288, an open channel blocker specific for HCN channels, significantly reduces the activity-dependent increase in cAMP binding. Independent biochemical assays exclude any nonspecific interaction between ZD7288 and isolated cAMP-binding domain. Because ZD7228 interacts with the inner pore region, where the activation gate is presumably located, we did an alanine scanning of the intracellular end of S6, from T426 to A435. Mutations of three residues, T426, M430, and H434, which are located at regular intervals on the S6 α-helix, enhance cAMP binding. In contrast, mutations of two residues in close proximity, F431A and I432A, dampen the response. Our results demonstrate that movements of the structural elements near the activation gate directly affect ligand binding affinity, which is a simple mechanistic explanation that could be applied to the interpretation of ligand gating in general.
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Affiliation(s)
- Shengjun Wu
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
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13
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Battefeld A, Bierwirth C, Li YC, Barthel L, Velmans T, Strauss U. I(h) "run-up" in rat neocortical neurons and transiently rat or human HCN1-expressing HEK293 cells. J Neurosci Res 2011; 88:3067-78. [PMID: 20806410 DOI: 10.1002/jnr.22475] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated ion channels (HCN) are key determinants of CNS functions. Here we describe an increase in hyperpolarization-activated current (I(h)) at the beginning of whole-cell recordings in rat layer 5 cortical neurons. For a closer investigation of this I(h) increase, we overexpressed the predominant layer 5 rat subunit HCN1 in HEK293 cells. We characterized the resulting I(h) in the cell-attached and whole-cell configurations. Breaking into whole-cell configuration led to about a 30% enhancement of rat HCN1-mediated I(h) accompanied by a depolarizing shift in voltage dependence and an accelerated time course of activation. This current enhancement is not species specific; for human HCN1, the current similarly increases in amount and kinetics. Although the changes were bound to cytosolic solution exchange, they were independent of cAMP, ATP, GTP, and the phosphate group donor phosphocreatine. Together, these data provide a characterization of heterologous expression of rat HCN1 and suggest that cytosolic contents suppress I(h). Such a mechanism might constitute a reserve in h-channel function in vivo.
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Affiliation(s)
- Arne Battefeld
- Institute of Cell Biology and Neurobiology, Center for Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany.
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14
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Effects of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blockers on the proliferation and cell cycle progression of embryonic stem cells. Pflugers Arch 2010; 461:191-202. [DOI: 10.1007/s00424-010-0899-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 10/20/2010] [Accepted: 10/25/2010] [Indexed: 02/05/2023]
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15
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Matsuda H, Kurata Y, Oka C, Matsuoka S, Noma A. Magnesium gating of cardiac gap junction channels. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 103:102-10. [PMID: 20553744 DOI: 10.1016/j.pbiomolbio.2010.05.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 02/26/2010] [Accepted: 05/19/2010] [Indexed: 01/18/2023]
Abstract
We aimed to study kinetics of modulation by intracellular Mg(2+) of cardiac gap junction (Mg(2+) gate). Paired myocytes of guinea-pig ventricle were superfused with solutions containing various concentrations of Mg(2+). In order to rapidly apply Mg(2+) to one aspect of the gap junction, the non-junctional membrane of one of the pair was perforated at nearly the connecting site by pulses of nitrogen laser beam. The gap junction conductance (G(j)) was measured by clamping the membrane potential of the other cell using two-electrode voltage clamp method. The laser perforation immediately increased G(j), followed by slow G(j) change with time constant of 3.5 s at 10 mM Mg(2+). Mg(2+) more than 1.0 mM attenuated dose-dependently the gap junction conductance and lower Mg(2+) (0.6 mM) increased G(j) with a Hill coefficient of 3.4 and a half-maximum effective concentration of 0.6 mM. The time course of G(j) changes was fitted by single exponential function, and the relationship between the reciprocal of time constant and Mg(2+) concentration was almost linear. Based on the experimental data, a mathematical model of Mg(2+) gate with one open state and three closed states well reproduced experimental results. One-dimensional cable model of thirty ventricular myocytes connected to the Mg(2+) gate model suggested a pivotal role of the Mg(2+) gate of gap junction under pathological conditions.
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Affiliation(s)
- Hiroyuki Matsuda
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Yoshida-konoe, Sakyo-ku, Kyoto 606-8501, Japan
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16
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Zhou YH, Sun LH, Liu ZH, Bu G, Pang XP, Sun SC, Qiao GF, Li BY, Schild JH. Functional impact of the hyperpolarization-activated current on the excitability of myelinated A-type vagal afferent neurons in the rat. Clin Exp Pharmacol Physiol 2010; 37:852-61. [PMID: 20456426 DOI: 10.1111/j.1440-1681.2010.05396.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
1. The hyperpolarization-induced, cation-selective current I(h) is widely observed in peripheral sensory neurons of the vagal and dorsal root ganglia, but the peak magnitude and voltage- and time-dependent properties of this current vary widely across afferent fibre type. 2. Using patch clamp investigations of rat isolated vagal ganglion neurons (VGN) identified as myelinated A-type afferents, we established a compendium of functional correlates between changes in membrane potential and the dynamic discharge properties of these sensory neurons as a result of the controlled recruitment of I(h) using the current clamp technique. 3. Two robust responses were observed in response to hyperpolarizing step currents: (i) upon initiation of the negative step current, there was a rapid hyperpolarization of membrane potential followed by a depolarizing voltage sag (DVS) towards a plateau in membrane potential as a result of steady state recruitment of I(h); and (ii) upon termination of the negative step current, there was a rapid return to the pretest resting membrane potential that often led to spontaneous action potential discharge. These data were strongly correlated (r(2) > 0.9) with a broad compendium of dynamic discharge characteristics in these A-type VGN. 4. In response to depolarizing step currents of increasing magnitude, the discharge frequency of the A-type VGN responded with increases in the rate of sustained repetitive discharge. Upon termination of the depolarizing step current, there was a post-excitatory membrane hyperpolarization of a magnitude that was strongly correlated with action potential discharge rate (r(2) > 0.9). 5. Application of the selective hyperpolarization-activated cyclic nucleotide gated (HCN) channel blockers ZD7288 (10 micromol/L) or CsCl (1.0 mmol/L) abolished I(h) and all of the aforementioned functional correlates. In addition to reducing the excitability of the A-type VGN to step depolarizing currents. 6. Because there is increasing evidence that the HCN channel current may represent a valid target for pharmacological intervention, the quantitative relationships described in the present study could potentially help guide the molecular and/or chemical modification of HCN channel gating properties to effect a particular outcome in VGN discharge properties, ideally well beyond merely selective blockade of a particular HCN channel subtype.
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Affiliation(s)
- Yu-Hong Zhou
- Department of Pharmacology, Harbin Medical University, Harbin, China
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17
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Rozario AO, Turbendian HK, Fogle KJ, Olivier NB, Tibbs GR. Voltage-dependent opening of HCN channels: Facilitation or inhibition by the phytoestrogen, genistein, is determined by the activation status of the cyclic nucleotide gating ring. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1939-49. [PMID: 19524546 DOI: 10.1016/j.bbamem.2009.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Revised: 05/29/2009] [Accepted: 06/08/2009] [Indexed: 11/27/2022]
Abstract
Investigation of the mechanistic bases and physiological importance of cAMP regulation of HCN channels has exploited an arginine to glutamate mutation in the nucleotide-binding fold, an approach critically dependent on the mutation selectively lowering the channel's nucleotide affinity. In apparent conflict with this, in intact Xenopus oocytes, HCN and HCN-RE channels exhibit qualitatively and quantitatively distinct responses to the tyrosine kinase inhibitor, genistein -- the estrogenic isoflavonoid strongly depolarizes the activation mid-point of HCN1-R538E, but not HCN1 channels (+9.8 mV + or - 0.9 versus +2.2 mV + or - 0.6) and hyperpolarizes gating of HCN2 (-4.8 mV + or - 1.0) but depolarizes gating of HCN2-R591E (+13.2 mV + or - 2.1). However, excised patch recording, X-ray crystallography and modeling reveal that this is not due to either a fundamental effect of the mutation on channel gating per se or of genistein acting as a mutation-sensitive partial agonist at the cAMP site. Rather, we find that genistein equivalently moves both HCN and HCN-RE channels closer to the open state (rendering the channels inherently easier to open but at a cost of decreasing the coupling energy of cAMP) and that the anomaly reflects a balance of these energetic effects with the isoform-specific inhibition of activation by the nucleotide gating ring and relief of this by endogenous cAMP. These findings have specific implications with regard to findings based on HCN-RE channels and kinase antagonists and general implications with respect to interpretation of drug effects in mutant channel backgrounds.
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Affiliation(s)
- Anjali O Rozario
- Department of Anesthesiology, Columbia University, New York, NY 10032, USA
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