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Page DA, Ruben PC. Cannabidiol potentiates hyperpolarization-activated cyclic nucleotide-gated (HCN4) channels. J Gen Physiol 2024; 156:e202313505. [PMID: 38652080 PMCID: PMC11040500 DOI: 10.1085/jgp.202313505] [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: 11/10/2023] [Revised: 03/15/2024] [Accepted: 04/09/2024] [Indexed: 04/25/2024] Open
Abstract
Cannabidiol (CBD), the main non-psychotropic phytocannabinoid produced by the Cannabis sativa plant, blocks a variety of cardiac ion channels. We aimed to identify whether CBD regulated the cardiac pacemaker channel or the hyperpolarization-activated cyclic nucleotide-gated channel (HCN4). HCN4 channels are important for the generation of the action potential in the sinoatrial node of the heart and increased heart rate in response to β-adrenergic stimulation. HCN4 channels were expressed in HEK 293T cells, and the effect of CBD application was examined using a whole-cell patch clamp. We found that CBD depolarized the V1/2 of activation in holo-HCN4 channels, with an EC50 of 1.6 µM, without changing the current density. CBD also sped activation kinetics by approximately threefold. CBD potentiation of HCN4 channels occurred via binding to the closed state of the channel. We found that CBD's mechanism of action was distinct from cAMP, as CBD also potentiated apo-HCN4 channels. The addition of an exogenous PIP2 analog did not alter the ability of CBD to potentiate HCN4 channels, suggesting that CBD also acts using a unique mechanism from the known HCN4 potentiator PIP2. Lastly, to gain insight into CBD's mechanism of action, computational modeling and targeted mutagenesis were used to predict that CBD binds to a lipid-binding pocket at the C-terminus of the voltage sensor. CBD represents the first FDA-approved drug to potentiate HCN4 channels, and our findings suggest a novel starting point for drug development targeting HCN4 channels.
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Affiliation(s)
- Dana A. Page
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Peter C. Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
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2
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Metzner C, Mäki-Marttunen T, Karni G, McMahon-Cole H, Steuber V. The effect of alterations of schizophrenia-associated genes on gamma band oscillations. SCHIZOPHRENIA 2022; 8:46. [PMID: 35854005 PMCID: PMC9261091 DOI: 10.1038/s41537-022-00255-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 04/08/2022] [Indexed: 11/30/2022]
Abstract
Abnormalities in the synchronized oscillatory activity of neurons in general and, specifically in the gamma band, might play a crucial role in the pathophysiology of schizophrenia. While these changes in oscillatory activity have traditionally been linked to alterations at the synaptic level, we demonstrate here, using computational modeling, that common genetic variants of ion channels can contribute strongly to this effect. Our model of primary auditory cortex highlights multiple schizophrenia-associated genetic variants that reduce gamma power in an auditory steady-state response task. Furthermore, we show that combinations of several of these schizophrenia-associated variants can produce similar effects as the more traditionally considered synaptic changes. Overall, our study provides a mechanistic link between schizophrenia-associated common genetic variants, as identified by genome-wide association studies, and one of the most robust neurophysiological endophenotypes of schizophrenia.
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Mäki-Marttunen T, Devor A, Phillips WA, Dale AM, Andreassen OA, Einevoll GT. Computational Modeling of Genetic Contributions to Excitability and Neural Coding in Layer V Pyramidal Cells: Applications to Schizophrenia Pathology. Front Comput Neurosci 2019; 13:66. [PMID: 31616272 PMCID: PMC6775251 DOI: 10.3389/fncom.2019.00066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 09/09/2019] [Indexed: 11/13/2022] Open
Abstract
Pyramidal cells in layer V of the neocortex are one of the most widely studied neuron types in the mammalian brain. Due to their role as integrators of feedforward and cortical feedback inputs, they are well-positioned to contribute to the symptoms and pathology in mental disorders-such as schizophrenia-that are characterized by a mismatch between the internal perception and external inputs. In this modeling study, we analyze the input/output properties of layer V pyramidal cells and their sensitivity to modeled genetic variants in schizophrenia-associated genes. We show that the excitability of layer V pyramidal cells and the way they integrate inputs in space and time are altered by many types of variants in ion-channel and Ca2+ transporter-encoding genes that have been identified as risk genes by recent genome-wide association studies. We also show that the variability in the output patterns of spiking and Ca2+ transients in layer V pyramidal cells is altered by these model variants. Importantly, we show that many of the predicted effects are robust to noise and qualitatively similar across different computational models of layer V pyramidal cells. Our modeling framework reveals several aspects of single-neuron excitability that can be linked to known schizophrenia-related phenotypes and existing hypotheses on disease mechanisms. In particular, our models predict that single-cell steady-state firing rate is positively correlated with the coding capacity of the neuron and negatively correlated with the amplitude of a prepulse-mediated adaptation and sensitivity to coincidence of stimuli in the apical dendrite and the perisomatic region of a layer V pyramidal cell. These results help to uncover the voltage-gated ion-channel and Ca2+ transporter-associated genetic underpinnings of schizophrenia phenotypes and biomarkers.
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Affiliation(s)
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States.,Martinos Center for Biomedical Imaging, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States
| | - William A Phillips
- Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States
| | - Ole A Andreassen
- NORMENT, Division of Mental Health and Addiction, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Gaute T Einevoll
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway.,Department of Physics, University of Oslo, Oslo, Norway
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Mäki-Marttunen T, Krull F, Bettella F, Hagen E, Næss S, Ness TV, Moberget T, Elvsåshagen T, Metzner C, Devor A, Edwards AG, Fyhn M, Djurovic S, Dale AM, Andreassen OA, Einevoll GT. Alterations in Schizophrenia-Associated Genes Can Lead to Increased Power in Delta Oscillations. Cereb Cortex 2019; 29:875-891. [PMID: 30475994 PMCID: PMC6319172 DOI: 10.1093/cercor/bhy291] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/03/2018] [Indexed: 12/13/2022] Open
Abstract
Genome-wide association studies have implicated many ion channels in schizophrenia pathophysiology. Although the functions of these channels are relatively well characterized by single-cell studies, the contributions of common variation in these channels to neurophysiological biomarkers and symptoms of schizophrenia remain elusive. Here, using computational modeling, we show that a common biomarker of schizophrenia, namely, an increase in delta-oscillation power, may be a direct consequence of altered expression or kinetics of voltage-gated ion channels or calcium transporters. Our model of a circuit of layer V pyramidal cells highlights multiple types of schizophrenia-related variants that contribute to altered dynamics in the delta-frequency band. Moreover, our model predicts that the same membrane mechanisms that increase the layer V pyramidal cell network gain and response to delta-frequency oscillations may also cause a deficit in a single-cell correlate of the prepulse inhibition, which is a behavioral biomarker highly associated with schizophrenia.
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Affiliation(s)
- Tuomo Mäki-Marttunen
- Simula Research Laboratory, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Florian Krull
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Francesco Bettella
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Espen Hagen
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Solveig Næss
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Torbjørn V Ness
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Torgeir Moberget
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Torbjørn Elvsåshagen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Christoph Metzner
- Centre for Computer Science and Informatics Research, University of Hertfordshire, Hatfield, UK
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | | | - Marianne Fyhn
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Srdjan Djurovic
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
| | - Ole A Andreassen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
| | - Gaute T Einevoll
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
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5
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Cao Y, Chen S, Liang Y, Wu T, Pang J, Liu S, Zhou P. Inhibition of hyperpolarization-activated cyclic nucleotide-gated channels by β-blocker carvedilol. Br J Pharmacol 2018; 175:3963-3975. [PMID: 30098004 DOI: 10.1111/bph.14469] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 07/02/2018] [Accepted: 07/30/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE Carvedilol is a clinically effective β-blocker broadly used for treating congestive heart failure (CHF), and several clinical trials have demonstrated that it shows a favourable effect compared with other β-blockers in patients with CHF. The mechanism underlying this beneficial effect of carvedilol compared to other β-blockers is not clearly understood. In addition to β-blockers, inhibitors of hyperpolarization-activated cyclic nucleotide (HCN)-gated channels, which play a critical role in spontaneous rhythmic activity in the heart, have also been proposed to be suitable drugs for reducing heart rate and, therefore, beneficial for treating CHF. In the present study, we investigated the effect of carvedilol on HCN channels. EXPERIMENTAL APPROACH Whole-cell patch-clamp recordings were used to assess the effect of carvedilol on currents from wild-type and mutant HCN1, HCN2 and HCN4 channels expressed in CHO cells. KEY RESULTS Carvedilol was the only β-blocker tested that showed inhibitory effects on the major sinoatrial HCN channel isoform HCN4. Carvedilol inhibited HCN4 in a concentration-dependent manner with an EC50 of 4.4 μM. In addition, carvedilol also inhibited HCN1 and HCN2 channels. Carvedilol blocked HCN channels by decelerating the rate of channel activation and increasing that of deactivation, and shifted the voltage-dependence of activation leftwards. Our data also showed that carvedilol, unlike other inhibitors of this channel (ivabradine and ZD7288), is not an 'open-channel' inhibitor of HCN4. CONCLUSIONS AND IMPLICATIONS Carvedilol is a negative gating modulator of HCN channels. It represents a novel structure for future drug design of HCN channel inhibitors.
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Affiliation(s)
- Ying Cao
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Shujun Chen
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Yemei Liang
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Ting Wu
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Jianxin Pang
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Shuwen Liu
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China.,State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Southern Medical University, Guangzhou, China
| | - Pingzheng Zhou
- Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
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6
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Mäki-Marttunen T, Lines GT, Edwards AG, Tveito A, Dale AM, Einevoll GT, Andreassen OA. Pleiotropic effects of schizophrenia-associated genetic variants in neuron firing and cardiac pacemaking revealed by computational modeling. Transl Psychiatry 2017; 7:5. [PMID: 30446648 PMCID: PMC5802468 DOI: 10.1038/s41398-017-0007-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/07/2017] [Accepted: 07/14/2017] [Indexed: 01/01/2023] Open
Abstract
Schizophrenia patients have an increased risk of cardiac dysfunction. A possible factor underlying this comorbidity are the common variants in the large set of genes that have recently been discovered in genome-wide association studies (GWASs) as risk genes of schizophrenia. Many of these genes control the cell electrogenesis and calcium homeostasis. We applied biophysically detailed models of layer V pyramidal cells and sinoatrial node cells to study the contribution of schizophrenia-associated genes on cellular excitability. By including data from functional genomics literature to simulate the effects of common variants of these genes, we showed that variants of voltage-gated Na+ channel or hyperpolarization-activated cation channel-encoding genes cause qualitatively similar effects on layer V pyramidal cell and sinoatrial node cell excitability. By contrast, variants of Ca2+ channel or transporter-encoding genes mostly have opposite effects on cellular excitability in the two cell types. We also show that the variants may crucially affect the propagation of the cardiac action potential in the sinus node. These results may help explain some of the cardiac comorbidity in schizophrenia, and may facilitate generation of effective antipsychotic medications without cardiac side-effects such as arrhythmia.
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Affiliation(s)
- Tuomo Mäki-Marttunen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway. .,Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway.
| | - Glenn T. Lines
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Andrew G. Edwards
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Aslak Tveito
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Anders M. Dale
- 0000 0001 2107 4242grid.266100.3Multimodal Imaging Laboratory, UC San Diego, La Jolla, CA USA ,0000 0001 2107 4242grid.266100.3Department of Neurosciences, University of California San Diego, La Jolla, CA USA ,0000 0001 2107 4242grid.266100.3Department of Radiology, University of California, San Diego, La Jolla, CA USA
| | - Gaute T. Einevoll
- 0000 0004 0607 975Xgrid.19477.3cDepartment of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway ,0000 0004 1936 8921grid.5510.1Department of Physics, University of Oslo, Oslo, Norway
| | - Ole A. Andreassen
- 0000 0004 1936 8921grid.5510.1NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway ,0000 0004 0389 8485grid.55325.34Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
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7
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Skerrett IM, Williams JB. A structural and functional comparison of gap junction channels composed of connexins and innexins. Dev Neurobiol 2017; 77:522-547. [PMID: 27582044 PMCID: PMC5412853 DOI: 10.1002/dneu.22447] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 08/12/2016] [Accepted: 08/30/2016] [Indexed: 02/03/2023]
Abstract
Methods such as electron microscopy and electrophysiology led to the understanding that gap junctions were dense arrays of channels connecting the intracellular environments within almost all animal tissues. The characteristics of gap junctions were remarkably similar in preparations from phylogenetically diverse animals such as cnidarians and chordates. Although few studies directly compared them, minor differences were noted between gap junctions of vertebrates and invertebrates. For instance, a slightly wider gap was noted between cells of invertebrates and the spacing between invertebrate channels was generally greater. Connexins were identified as the structural component of vertebrate junctions in the 1980s and innexins as the structural component of pre-chordate junctions in the 1990s. Despite a lack of similarity in gene sequence, connexins and innexins are remarkably similar. Innexins and connexins have the same membrane topology and form intercellular channels that play a variety of tissue- and temporally specific roles. Both protein types oligomerize to form large aqueous channels that allow the passage of ions and small metabolites and are regulated by factors such as pH, calcium, and voltage. Much more is currently known about the structure, function, and structure-function relationships of connexins. However, the innexin field is expanding. Greater knowledge of innexin channels will permit more detailed comparisons with their connexin-based counterparts, and provide insight into the ubiquitous yet specific roles of gap junctions. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 522-547, 2017.
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Affiliation(s)
- I Martha Skerrett
- Biology Department, SUNY Buffalo State, 1300 Elmwood Ave, Buffalo, New York, 14222
| | - Jamal B Williams
- Biology Department, SUNY Buffalo State, 1300 Elmwood Ave, Buffalo, New York, 14222
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8
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Okuda H, Yonezawa Y, Takano Y, Okamura Y, Fujiwara Y. Direct Interaction between the Voltage Sensors Produces Cooperative Sustained Deactivation in Voltage-gated H+ Channel Dimers. J Biol Chem 2016; 291:5935-5947. [PMID: 26755722 PMCID: PMC4786727 DOI: 10.1074/jbc.m115.666834] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 12/23/2015] [Indexed: 01/31/2023] Open
Abstract
The voltage-gated H(+) channel (Hv) is a voltage sensor domain-like protein consisting of four transmembrane segments (S1-S4). The native Hv structure is a homodimer, with the two channel subunits functioning cooperatively. Here we show that the two voltage sensor S4 helices within the dimer directly cooperate via a π-stacking interaction between Trp residues at the middle of each segment. Scanning mutagenesis showed that Trp situated around the original position provides the slow gating kinetics characteristic of the dimer's cooperativity. Analyses of the Trp mutation on the dimeric and monomeric channel backgrounds and analyses with tandem channel constructs suggested that the two Trp residues within the dimer are functionally coupled during Hv deactivation but are less so during activation. Molecular dynamics simulation also showed direct π-stacking of the two Trp residues. These results provide new insight into the cooperative function of voltage-gated channels, where adjacent voltage sensor helices make direct physical contact and work as a single unit according to the gating process.
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Affiliation(s)
- Hiroko Okuda
- From Division of Integrative Physiology, Graduate School of Medicine
| | - Yasushige Yonezawa
- the High Pressure Protein Research Center, Institute of Advanced Technology, Kinki University, Kinokawa 649-6493, Wakayama, Japan, and
| | - Yu Takano
- the Institute for Protein Research, and; the Graduate School of Information Sciences, Hiroshima City University, Hiroshima 731-3194, Hiroshima, Japan
| | - Yasushi Okamura
- From Division of Integrative Physiology, Graduate School of Medicine,; the Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Osaka, Japan
| | - Yuichiro Fujiwara
- From Division of Integrative Physiology, Graduate School of Medicine,.
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9
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Mäki-Marttunen T, Halnes G, Devor A, Witoelar A, Bettella F, Djurovic S, Wang Y, Einevoll GT, Andreassen OA, Dale AM. Functional Effects of Schizophrenia-Linked Genetic Variants on Intrinsic Single-Neuron Excitability: A Modeling Study. BIOLOGICAL PSYCHIATRY: COGNITIVE NEUROSCIENCE AND NEUROIMAGING 2016; 1:49-59. [PMID: 26949748 DOI: 10.1016/j.bpsc.2015.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Recent genome-wide association studies have identified a large number of genetic risk factors for schizophrenia (SCZ) featuring ion channels and calcium transporters. For some of these risk factors, independent prior investigations have examined the effects of genetic alterations on the cellular electrical excitability and calcium homeostasis. In the present proof-of-concept study, we harnessed these experimental results for modeling of computational properties on layer V cortical pyramidal cells and identified possible common alterations in behavior across SCZ-related genes. METHODS We applied a biophysically detailed multicompartmental model to study the excitability of a layer V pyramidal cell. We reviewed the literature on functional genomics for variants of genes associated with SCZ and used changes in neuron model parameters to represent the effects of these variants. RESULTS We present and apply a framework for examining the effects of subtle single nucleotide polymorphisms in ion channel and calcium transporter-encoding genes on neuron excitability. Our analysis indicates that most of the considered SCZ-related genetic variants affect the spiking behavior and intracellular calcium dynamics resulting from summation of inputs across the dendritic tree. CONCLUSIONS Our results suggest that alteration in the ability of a single neuron to integrate the inputs and scale its excitability may constitute a fundamental mechanistic contributor to mental disease, alongside the previously proposed deficits in synaptic communication and network behavior.
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Affiliation(s)
- Tuomo Mäki-Marttunen
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Geir Halnes
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Anna Devor
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Aree Witoelar
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Francesco Bettella
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Srdjan Djurovic
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Yunpeng Wang
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Gaute T Einevoll
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Ole A Andreassen
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
| | - Anders M Dale
- Norwegian Centre for Mental Disorders Research and KG Jebsen Centre for Psychosis Research (TM-M, AW, FB, YW, OAA), Institute of Clinical Medicine, University of Oslo, Oslo; and Department of Mathematical Sciences and Technology (GH, GTE), Norwegian University of Life Sciences, Ås, Norway; Departments of Neurosciences (AD, YW, AMD) and Radiology (AD, AMD), University of California, San Diego, La Jolla, California; Martinos Center for Biomedical Imaging (AD), Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; and Division of Mental Health and Addiction (FB, YW, OAA) and Department of Medical Genetics (SD), Oslo University Hospital, Oslo; Norwegian Centre for Mental Disorders Research (SD), KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen; and Department of Physics (GTE), University of Oslo, Oslo, Norway
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10
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Brennan MJ, Karcz J, Vaughn NR, Woolwine-Cunningham Y, DePriest AD, Escalona Y, Perez-Acle T, Skerrett IM. Tryptophan Scanning Reveals Dense Packing of Connexin Transmembrane Domains in Gap Junction Channels Composed of Connexin32. J Biol Chem 2015; 290:17074-84. [PMID: 25969535 PMCID: PMC4498046 DOI: 10.1074/jbc.m115.650747] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/29/2015] [Indexed: 11/06/2022] Open
Abstract
Tryptophan was substituted for residues in all four transmembrane domains of connexin32. Function was assayed using dual cell two-electrode voltage clamp after expression in Xenopus oocytes. Tryptophan substitution was poorly tolerated in all domains, with the greatest impact in TM1 and TM4. For instance, in TM1, 15 substitutions were made, six abolished coupling and five others significantly reduced function. Only TM2 and TM3 included a distinct helical face that lacked sensitivity to tryptophan substitution. Results were visualized on a comparative model of Cx32 hemichannel. In this model, a region midway through the membrane appears highly sensitive to tryptophan substitution and includes residues Arg-32, Ile-33, Met-34, and Val-35. In the modeled channel, pore-facing regions of TM1 and TM2 were highly sensitive to tryptophan substitution, whereas the lipid-facing regions of TM3 and TM4 were variably tolerant. Residues facing a putative intracellular water pocket (the IC pocket) were also highly sensitive to tryptophan substitution. Although future studies will be required to separate trafficking-defective mutants from those that alter channel function, a subset of interactions important for voltage gating was identified. Interactions important for voltage gating occurred mainly in the mid-region of the channel and focused on TM1. To determine whether results could be extrapolated to other connexins, TM1 of Cx43 was scanned revealing similar but not identical sensitivity to TM1 of Cx32.
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Affiliation(s)
- Matthew J Brennan
- From the Biology Department, State University of New York Buffalo State, Buffalo, New York 14222
| | - Jennifer Karcz
- From the Biology Department, State University of New York Buffalo State, Buffalo, New York 14222
| | - Nicholas R Vaughn
- From the Biology Department, State University of New York Buffalo State, Buffalo, New York 14222
| | - Yvonne Woolwine-Cunningham
- the Clinical and Translational Research Center, State University of New York at Buffalo, Buffalo, New York 14214
| | - Adam D DePriest
- the Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Yerko Escalona
- the Computational Biology Lab, Fundación Ciencia and Vida, 7780344 Santiago, Chile, and the Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, 2360102 Valparaíso, Chile
| | - Tomas Perez-Acle
- the Computational Biology Lab, Fundación Ciencia and Vida, 7780344 Santiago, Chile, and the Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, 2360102 Valparaíso, Chile
| | - I Martha Skerrett
- From the Biology Department, State University of New York Buffalo State, Buffalo, New York 14222,
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11
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Abstract
Ion channels, as membrane proteins, are the sensors of the cell. They act as the first line of communication with the world beyond the plasma membrane and transduce changes in the external and internal environments into unique electrical signals to shape the responses of excitable cells. Because of their importance in cellular communication, ion channels have been intensively studied at the structural and functional levels. Here, we summarize the diverse approaches, including molecular and cellular, chemical, optical, biophysical, and computational, used to probe the structural and functional rearrangements that occur during channel activation (or sensitization), inactivation (or desensitization), and various forms of modulation. The emerging insights into the structure and function of ion channels by multidisciplinary approaches allow the development of new pharmacotherapies as well as new tools useful in controlling cellular activity.
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Affiliation(s)
- Wei-Guang Li
- Neuroscience Division, Department of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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12
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Depriest A, Phelan P, Martha Skerrett I. Tryptophan scanning mutagenesis of the first transmembrane domain of the innexin Shaking-B(Lethal). Biophys J 2011; 101:2408-16. [PMID: 22098739 DOI: 10.1016/j.bpj.2011.10.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 10/03/2011] [Accepted: 10/06/2011] [Indexed: 12/25/2022] Open
Abstract
The channel proteins of gap junctions are encoded by two distinct gene families, connexins, which are exclusive to chordates, and innexins/pannexins, which are found throughout the animal kingdom. Although the relationship between the primary structure and function of the vertebrate connexins has been relatively well studied, there are, to our knowledge, no structure-function analyses of invertebrate innexins. In the first such study, we have used tryptophan scanning to probe the first transmembrane domain (M1) of the Drosophila innexin Shaking-B(Lethal), which is a component of rectifying electrical synapses in the Giant Fiber escape neural circuit. Tryptophan was substituted sequentially for 16 amino acids within M1 of Shaking-B(Lethal). Tryptophan insertion at every fourth residue (H27, T31, L35, and S39) disrupted gap junction function. The distribution of these sites is consistent with helical secondary structure and identifies the face of M1 involved in helix-helix interactions. Tryptophan substitution at several sites in M1 altered channel properties in a variety of ways. Changes in sensitivity to transjunctional voltage (Vj) were common and one mutation (S39W) induced sensitivity to transmembrane voltage (Vm). In addition, several mutations induced hemichannel activity. These changes are similar to those observed after substitutions within the transmembrane domains of connexins.
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Affiliation(s)
- Adam Depriest
- Biology Department, Buffalo State College, Buffalo, New York, USA
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13
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Ishii TM, Nakashima N, Takatsuka K, Ohmori H. Peripheral N- and C-terminal domains determine deactivation kinetics of HCN channels. Biochem Biophys Res Commun 2007; 359:592-8. [PMID: 17548059 DOI: 10.1016/j.bbrc.2007.05.127] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 05/18/2007] [Indexed: 11/28/2022]
Abstract
Among four subtypes of mammalian HCN channels, HCN1 has the fastest activation and deactivation kinetics while HCN4 shows the slowest. We previously showed that the activation kinetics are determined mainly by S1, S1-S2, and the S6-cyclic nucleotide binding domain. However, the effects of those regions on the deactivation kinetics were relatively small. Therefore, we investigated the structural basis for deactivation kinetics. Substitution of the core region (from S3 to S6) between HCN1 and HCN4 did not affect deactivation kinetics. This suggests that the peripheral regions (outside of S3 to S6) determine subtype-specific deactivation kinetics. Furthermore, we examined whether peripheral regions determined the deactivation kinetics across species by introducing the core region of DMIH (Drosophila homologue) into both HCN1 and HCN4. The DMIH core with HCN1 activated and deactivated more than threefold faster than that with HCN4. Taken together, the peripheral domains are diversified to create distinct kinetics.
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Affiliation(s)
- Takahiro M Ishii
- Department of Physiology, Faculty of Medicine, Kyoto University, Kyoto 606-8501, Japan
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