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Song R, Chen H, Zhan R, Han M, Zhao L, Shen X. Vitamin E protects dopaminergic neurons against manganese-induced neurotoxicity through stimulation of CHRM1 and KCNJ4. J Trace Elem Med Biol 2024; 81:127326. [PMID: 37939525 DOI: 10.1016/j.jtemb.2023.127326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 10/17/2023] [Accepted: 10/19/2023] [Indexed: 11/10/2023]
Abstract
BACKGROUND Manganese (Mn) overexposure can induce neurotoxicity and lead to manganism. Vitamin E (Vit E) has neuroprotective effects by acting as an ROS scavenger, preventing mitochondrial dysfunction and neuronal apoptosis. However, the effects of Vit E on Mn-induced nigrostriatal system lesions remains unknown. OBJECTIVES We aim to investigate whether Vit E has protective effects on Mn-induced nigrostriatal system lesions and mRNA expression profiles in the SN of mice. METHODS Sixty 8-week-old C57BL/6 male mice were randomly divided into the Control, MnCl2, MnCl2 +Vit E, and Vit E group. Twenty-four hours after the last injection, the behaviour test was performed. The numbers of dopaminergic neurons in Substantia nigra (SN), the contents of dopamine and its metabolite levels in striatium, and the morphology of mitochondria and nuclei in the dopaminergic neurons in SN were detected by immunofluorescence staining, high-performance liquid chromatography, and transmission electron microscopy. Transcriptome analysis was used to analyze the signaling pathways and RT-PCR was used to verify the mRNA levels. RESULTS Vit E ameliorates behavioral disorders and attenuates the loss of nigral dopaminergic neurons in the Mn-induced mouse model. In addition, Vit E antagonized Mn-induced toxicity by restoring mitochondrial function. The results of transcriptome sequencing and RTPCR show that the protective effect of Vit E was related to the upregulation of CHRM1 and KCNJ4 mRNA in the SN. CONCLUSIONS Vit E has neuroprotective effects on Mn-induced neurodegeneration in the nigrostriatal system. This effect may be related to the upregulation of CHRM1 and KCNJ4 mRNA stimulated by Vit E in the SN.
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Affiliation(s)
- Ruihan Song
- Department of Epidemiology and Health Statistics, Medical School of Qingdao University, Qingdao, Shandong, China
| | - Huanhuan Chen
- Qingdao Municipal Center for Disease Control and Prevention/Qingdao Institute of Preventive Medicine, Qingdao, Shandong, China
| | - Runqing Zhan
- Qingdao University Affiliated Hiser Hospital, Qingdao, Shandong, China
| | - Miaomiao Han
- Department of Epidemiology and Health Statistics, Medical School of Qingdao University, Qingdao, Shandong, China
| | - Longzhu Zhao
- Department of Epidemiology and Health Statistics, Medical School of Qingdao University, Qingdao, Shandong, China
| | - Xiaoli Shen
- Department of Epidemiology and Health Statistics, Medical School of Qingdao University, Qingdao, Shandong, China.
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Lebenheim L, Booker SA, Derst C, Weiss T, Wagner F, Gruber C, Vida I, Zahm DS, Veh RW. A novel giant non-cholinergic striatal interneuron restricted to the ventrolateral striatum coexpresses Kv3.3 potassium channel, parvalbumin, and the vesicular GABA transporter. Mol Psychiatry 2022; 27:2315-2328. [PMID: 33190145 PMCID: PMC9126804 DOI: 10.1038/s41380-020-00948-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The striatum is the main input structure of the basal ganglia. Distinct striatal subfields are involved in voluntary movement generation and cognitive and emotional tasks, but little is known about the morphological and molecular differences of striatal subregions. The ventrolateral subfield of the striatum (VLS) is the orofacial projection field of the sensorimotor cortex and is involved in the development of orofacial dyskinesias, involuntary chewing-like movements that often accompany long-term neuroleptic treatment. The biological basis for this particular vulnerability of the VLS is not known. Potassium channels are known to be strategically localized within the striatum. In search of possible molecular correlates of the specific vulnerability of the VLS, we analyzed the expression of voltage-gated potassium channels in rodent and primate brains using qPCR, in situ hybridization, and immunocytochemical single and double staining. Here we describe a novel, giant, non-cholinergic interneuron within the VLS. This neuron coexpresses the vesicular GABA transporter, the calcium-binding protein parvalbumin (PV), and the Kv3.3 potassium channel subunit. This novel neuron is much larger than PV neurons in other striatal regions, displays characteristic electrophysiological properties, and, most importantly, is restricted to the VLS. Consequently, the giant striatal Kv3.3-expressing PV neuron may link compromised Kv3 channel function and VLS-based orofacial dyskinesias.
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Affiliation(s)
- Lydia Lebenheim
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany
| | - Sam A Booker
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Christian Derst
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany
| | - Torsten Weiss
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany
| | - Franziska Wagner
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany.,Hans Berger Klinik für Neurologie, Universitätsklinikum Jena, An der Klinik 1, D-07747, Jena, Germany
| | - Clemens Gruber
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany
| | - Imre Vida
- Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany
| | - Daniel S Zahm
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine, 1402 S. Grand Blvd, Saint Louis, MO, 63104, USA.
| | - Rüdiger W Veh
- Institut für Zell- und Neurobiologie, Charité -Universitätsmedizin Berlin, Philippstraße 12, D-10115, Berlin, Germany.
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Ukhanov K, Uytingco C, Green W, Zhang L, Schurmans S, Martens JR. INPP5E controls ciliary localization of phospholipids and the odor response in olfactory sensory neurons. J Cell Sci 2021; 135:jcs.258364. [PMID: 33771931 PMCID: PMC8126451 DOI: 10.1242/jcs.258364] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 03/15/2021] [Indexed: 12/12/2022] Open
Abstract
The lipid composition of the primary cilia membrane is emerging as a critical regulator of cilia formation, maintenance and function. Here, we show that conditional deletion of the phosphoinositide 5′-phosphatase gene Inpp5e, mutation of which is causative of Joubert syndrome, in terminally developed mouse olfactory sensory neurons (OSNs), leads to a dramatic remodeling of ciliary phospholipids that is accompanied by marked elongation of cilia. Phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2], which is normally restricted to the proximal segment redistributed to the entire length of cilia in Inpp5e knockout mice with a reduction in phosphatidylinositol (3,4)-bisphosphate [PI(3,4)P2] and elevation of phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] in the dendritic knob. The redistribution of phosphoinositides impaired odor adaptation, resulting in less efficient recovery and altered inactivation kinetics of the odor-evoked electrical response and the odor-induced elevation of cytoplasmic Ca2+. Gene replacement of Inpp5e through adenoviral expression restored the ciliary localization of PI(4,5)P2 and odor response kinetics in OSNs. Our findings support the role of phosphoinositides as a modulator of the odor response and in ciliary biology of native multi-ciliated OSNs. Summary: Cilia of olfactory sensory neurons have a unique lipid composition. Localization of phospholipids is controlled by the INPP5E phosphatase and is involved in modulation of the odor response.
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Affiliation(s)
- Kirill Ukhanov
- University of Florida, Department of Pharmacology and Therapeutics, Gainesville, FL 32603, USA.,University of Florida, Center for Smell and Taste, FL 32610-0267, USA
| | - Cedric Uytingco
- University of Florida, Department of Pharmacology and Therapeutics, Gainesville, FL 32603, USA
| | - Warren Green
- University of Florida, Department of Pharmacology and Therapeutics, Gainesville, FL 32603, USA
| | - Lian Zhang
- University of Florida, Department of Pharmacology and Therapeutics, Gainesville, FL 32603, USA.,University of Florida, Center for Smell and Taste, FL 32610-0267, USA
| | - Stephane Schurmans
- Laboratory of Functional Genetics, GIGA-Molecular Biology of Disease, University of Liège, Liège, Belgium
| | - Jeffrey R Martens
- University of Florida, Department of Pharmacology and Therapeutics, Gainesville, FL 32603, USA.,University of Florida, Center for Smell and Taste, FL 32610-0267, USA
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Paz RM, Tubert C, Stahl AM, Amarillo Y, Rela L, Murer MG. Levodopa Causes Striatal Cholinergic Interneuron Burst-Pause Activity in Parkinsonian Mice. Mov Disord 2021; 36:1578-1591. [PMID: 33547844 DOI: 10.1002/mds.28516] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/05/2021] [Accepted: 01/11/2021] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Enhanced striatal cholinergic interneuron activity contributes to the striatal hypercholinergic state in Parkinson's disease (PD) and to levodopa-induced dyskinesia. In severe PD, dyskinesia and motor fluctuations become seriously debilitating, and the therapeutic strategies become scarce. Given that the systemic administration of anticholinergics can exacerbate extrastriatal-related symptoms, targeting cholinergic interneurons is a promising therapeutic alternative. Therefore, unraveling the mechanisms causing pathological cholinergic interneuron activity in severe PD with motor fluctuations and dyskinesia may provide new molecular therapeutic targets. METHODS We used ex vivo electrophysiological recordings combined with pharmacological and morphological studies to investigate the intrinsic alterations of cholinergic interneurons in the 6-hydroxydopamine mouse model of PD treated with levodopa. RESULTS Cholinergic interneurons exhibit pathological burst-pause activity in the parkinsonian "off levodopa" state. This is mediated by a persistent ligand-independent activity of dopamine D1/D5 receptor signaling, involving a cyclic adenosine monophosphate (cAMP) pathway. Dysregulation of membrane ion channels that results in increased inward-rectifier potassium type 2 (Kir2) and decreased leak currents causes the burst pause activity, which can be dampened by pharmacological inhibition of intracellular cAMP. A single challenge with a dyskinetogenic dose of levodopa is sufficient to induce persistent cholinergic interneuron burst-pause firing. CONCLUSION Our data unravel a mechanism causing aberrant cholinergic interneuron burst-pause activity in parkinsonian mice treated with levodopa. Targeting D5-cAMP signaling and the regulation of Kir2 and leak channels may alleviate parkinsonism and dyskinesia by restoring normal cholinergic interneuron function. © 2021 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Rodrigo Manuel Paz
- Universidad de Buenos Aires, CONICET, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, 2155 Paraguay Street, Buenos Aires, 1121, Argentina
| | - Cecilia Tubert
- Universidad de Buenos Aires, CONICET, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, 2155 Paraguay Street, Buenos Aires, 1121, Argentina
| | - Agostina Monica Stahl
- Universidad de Buenos Aires, CONICET, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, 2155 Paraguay Street, Buenos Aires, 1121, Argentina
| | - Yimy Amarillo
- Departamento de Física Médica, Centro Atómico Bariloche and Instituto Balseiro, CONICET, 9500 Ezequiel Bustillo Avenue, San Carlos de Bariloche, Rio Negro, 8402, Argentina
| | - Lorena Rela
- Universidad de Buenos Aires, CONICET, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, 2155 Paraguay Street, Buenos Aires, 1121, Argentina
| | - Mario Gustavo Murer
- Universidad de Buenos Aires, CONICET, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, 2155 Paraguay Street, Buenos Aires, 1121, Argentina
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5
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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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Nibbeling EAR, Delnooz CCS, de Koning TJ, Sinke RJ, Jinnah HA, Tijssen MAJ, Verbeek DS. Using the shared genetics of dystonia and ataxia to unravel their pathogenesis. Neurosci Biobehav Rev 2017; 75:22-39. [PMID: 28143763 DOI: 10.1016/j.neubiorev.2017.01.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 12/09/2016] [Accepted: 01/24/2017] [Indexed: 12/13/2022]
Abstract
In this review we explore the similarities between spinocerebellar ataxias and dystonias, and suggest potentially shared molecular pathways using a gene co-expression network approach. The spinocerebellar ataxias are a group of neurodegenerative disorders characterized by coordination problems caused mainly by atrophy of the cerebellum. The dystonias are another group of neurological movement disorders linked to basal ganglia dysfunction, although evidence is now pointing to cerebellar involvement as well. Our gene co-expression network approach identified 99 shared genes and showed the involvement of two major pathways: synaptic transmission and neurodevelopment. These pathways overlapped in the two disorders, with a large role for GABAergic signaling in both. The overlapping pathways may provide novel targets for disease therapies. We need to prioritize variants obtained by whole exome sequencing in the genes associated with these pathways in the search for new pathogenic variants, which can than be used to help in the genetic counseling of patients and their families.
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Affiliation(s)
- Esther A R Nibbeling
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Cathérine C S Delnooz
- University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Tom J de Koning
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands; University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Richard J Sinke
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Hyder A Jinnah
- Departments of Neurology, Human Genetics and Pediatrics, Emory Clinic, Atlanta, USA
| | - Marina A J Tijssen
- University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Dineke S Verbeek
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands.
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7
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Domingos L, Desrus A, Même S, Même W. L-Phosphinothricin modulation of inwardly rectifying K+ channels increased excitability in striatal medium-sized spiny neurons. Arch Toxicol 2016; 90:1719-27. [DOI: 10.1007/s00204-016-1721-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 04/20/2016] [Indexed: 10/21/2022]
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8
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Zhao B, Zhu J, Dai D, Xing J, He J, Fu Z, Zhang L, Li Z, Wang W. Differential dopaminergic regulation of inwardly rectifying potassium channel mediated subthreshold dynamics in striatal medium spiny neurons. Neuropharmacology 2016; 107:396-410. [PMID: 27018450 DOI: 10.1016/j.neuropharm.2016.03.037] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 03/09/2016] [Accepted: 03/22/2016] [Indexed: 11/29/2022]
Abstract
The dorsal striatum plays a key role in motor control and cognitive processes. Proper functioning of the striatum relies on the fine dynamic balance between the direct pathway projection medium spiny neurons (MSNs) that express D1 dopamine receptor (D1 MSNs) and indirect pathway projection MSNs that express D2 dopamine receptor (D2 MSNs). The inwardly rectifying K(+) channels (Kir), which express on both D1 and D2 MSNs, participate in the subthreshold dynamics including the membrane resonance and dendritic integration. However, it remains unclear whether dopamine differentially regulates Kir mediated subthreshold dynamics in two subtypes MSNs. Using transgenic mice that express either tdTomato in D1 MSNs or eGFP in D2 MSNs, we explored the Kir mediated subthreshold dynamics in D1 or D2 MSNs with whole cell patch clamp recording in acute brain slices. We found that D1 receptor agonist increased the Kir current while D2 receptor activation decreased the Kir conductance. The dopamine regulation of the Kir enhanced the resonant frequency and reduced the resonant impedance of D1 MSNs. The converse is ture for D2 MSNs. It also caused an opposing effect on dendritic integration between D1 and D2 MSNs, which can promote stability of the two pathways. The D1 receptor activation modulated Kir through cAMP-PKA signaling, whereas the D2 receptor modulated Kir through PLC-PKC signaling. Our findings demonstrated the differential dopaminergic regulation role of Kir, which mediates distinct subthreshold dynamics, and thus, contributes to the role of dopamine in fine tuning the balance of the striatal direct and indirect pathway activities.
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Affiliation(s)
- Bo Zhao
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, PR China; Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, PR China; Department of Neurology, Anning Branch of Lanzhou General Hospital of Lanzhou Military Region, Lanzhou 730070, PR China
| | - Junling Zhu
- Department of Neurosurgery, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, PR China
| | - Dongqing Dai
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, PR China; Cadet Brigade, Fourth Military Medical University, Xi'an 710032, PR China
| | - Junling Xing
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, PR China
| | - Jiahou He
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, PR China; Cadet Brigade, Fourth Military Medical University, Xi'an 710032, PR China
| | - Zhanyan Fu
- Model System and Neurobiology Department, Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Lei Zhang
- Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, PR China
| | - Zhuyi Li
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, PR China.
| | - Wenting Wang
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an 710032, PR China.
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Murata Y, Yasaka T, Takano M, Ishihara K. Neuronal and glial expression of inward rectifier potassium channel subunits Kir2.x in rat dorsal root ganglion and spinal cord. Neurosci Lett 2016; 617:59-65. [PMID: 26854211 DOI: 10.1016/j.neulet.2016.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 01/25/2016] [Accepted: 02/02/2016] [Indexed: 12/12/2022]
Abstract
Inward rectifier K(+) channels of the Kir2.x subfamily play important roles in controlling the neuronal excitability. Although their cellular localization in the brain has been extensively studied, only a few studies have examined their expression in the spinal cord and peripheral nervous system. In this study, immunohistochemical analyses of Kir2.1, Kir2.2, and Kir2.3 expression were performed in rat dorsal root ganglion (DRG) and spinal cord using bright-field and confocal microscopy. In DRG, most ganglionic neurons expressed Kir2.1, Kir2.2 and Kir2.3, whereas satellite glial cells chiefly expressed Kir2.3. In the spinal cord, Kir2.1, Kir2.2 and Kir2.3 were all expressed highly in the gray matter of dorsal and ventral horns and moderately in the white matter also. Within the gray matter, the expression was especially high in the substantia gelatinosa (lamina II). Confocal images obtained using markers for neuronal cells, NeuN, and astrocytes, Sox9, showed expression of all three Kir2 subunits in both neuronal somata and astrocytes in lamina I-III of the dorsal horn and the lateral spinal nucleus of the dorsolateral funiculus. Immunoreactive signals other than those in neuronal and glial somata were abundant in lamina I and II, which probably located mainly in nerve fibers or nerve terminals. Colocalization of Kir2.1 and 2.3 and that of Kir2.2 and 2.3 were present in neuronal and glial somata. In the ventral horn, motor neurons and interneurons were also immunoreactive with the three Kir2 subunits. Our study suggests that Kir2 channels composed of Kir2.1-2.3 subunits are expressed in neuronal and glial cells in the DRG and spinal cord, contributing to sensory transduction and motor control.
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Affiliation(s)
- Yuzo Murata
- Department of Anatomy and Physiology, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan.
| | - Toshiharu Yasaka
- Department of Anatomy and Physiology, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan
| | - Makoto Takano
- Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Keiko Ishihara
- Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
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Abstract
The approximately 350 ion channels encoded by the mammalian genome are a main pillar of the nervous system. We have determined the expression pattern of 320 channels in the two-week-old (P14) rat brain by means of non-radioactive robotic in situ hybridization. Optimized methods were developed and implemented to generate stringently coronal brain sections. The use of standardized methods permits a direct comparison of expression patterns across the entire ion channel expression pattern data set and facilitates recognizing ion channel co-expression. All expression data are made publically available at the Genepaint.org database. Inwardly rectifying potassium channels (Kir, encoded by the Kcnj genes) regulate a broad spectrum of physiological processes. Kcnj channel expression patterns generated in the present study were fitted with a deformable subdivision mesh atlas produced for the P14 rat brain. This co-registration, when combined with numerical quantification of expression strengths, allowed for semi-quantitative automated annotation of expression patterns as well as comparisons among and between Kcnj subfamilies. The expression patterns of Kcnj channel were also cross validated against previously published expression patterns of Kcnj channel genes.
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11
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Differential expression of genes encoding neuronal ion-channel subunits in major depression, bipolar disorder and schizophrenia: implications for pathophysiology. Int J Neuropsychopharmacol 2012; 15:869-82. [PMID: 22008100 DOI: 10.1017/s1461145711001428] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Evidence concerning ion-channel abnormalities in the pathophysiology of common psychiatric disorders is still limited. Given the significance of ion channels in neuronal activity, neurotransmission and neuronal plasticity we hypothesized that the expression patterns of genes encoding different ion channels may be altered in schizophrenia, bipolar and unipolar disorders. Frozen samples of striatum including the nucleus accumbens (Str-NAc) and the lateral cerebellar hemisphere of 60 brains from depressed (MDD), bipolar (BD), schizophrenic and normal subjects, obtained from the Stanley Foundation Brain Collection, were assayed. mRNA of 72 different ion-channel subunits were determined by qRT-PCR and alteration in four genes were verified by immunoblotting. In the Str-NAc the prominent change was observed in the MDD group, in which there was a significant up-regulation in genes encoding voltage-gated potassium-channel subunits. However, in the lateral cerebellar hemisphere (cerebellum), the main change was observed in schizophrenia specimens, as multiple genes encoding various ion-channel subunits were significantly down-regulated. The impaired expression of genes encoding ion channels demonstrates a disease-related neuroanatomical pattern. The alterations observed in Str-NAc of MDD may imply electrical hypo-activity of this region that could be of relevance to MDD symptoms and treatment. The robust unidirectional alteration of both excitatory and inhibitory ion channels in the cerebellum may suggests cerebellar general hypo-transcriptional activity in schizophrenia.
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Ferreira NR, Mitkovski M, Stühmer W, Pardo LA, Del Bel EA. Ether-à-go-go 1 (Eag1) Potassium Channel Expression in Dopaminergic Neurons of Basal Ganglia is Modulated by 6-Hydroxydopamine Lesion. Neurotox Res 2011; 21:317-33. [DOI: 10.1007/s12640-011-9286-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 09/09/2011] [Accepted: 09/24/2011] [Indexed: 10/16/2022]
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13
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Stegen M, Kirchheim F, Hanuschkin A, Staszewski O, Veh RW, Wolfart J. Adaptive Intrinsic Plasticity in Human Dentate Gyrus Granule Cells during Temporal Lobe Epilepsy. Cereb Cortex 2011; 22:2087-101. [DOI: 10.1093/cercor/bhr294] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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14
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Gui YX, Wan Y, Xiao Q, Wang Y, Wang G, Chen SD. Verification of expressions of Kir2 as potential peripheral biomarkers in lymphocytes from patients with Parkinson's disease. Neurosci Lett 2011; 505:104-8. [PMID: 22001575 DOI: 10.1016/j.neulet.2011.09.070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 09/20/2011] [Accepted: 09/30/2011] [Indexed: 10/16/2022]
Abstract
Prior studies have reported gene expression alterations in peripheral blood lymphocytes (PBLs) obtained from patients with Parkinson's disease (PD) as compared to healthy controls. These alterations can not only be regarded as potential biomarkers, but also enhance understanding of the pathogenic mechanism of PD. In the present study, the gene expression levels of dopamine receptor (D2, D3), inward rectified potassium channels subunits Kir2 (Kir2.1, Kir2.2, Kir2.3, Kir2.4) and ATP-sensitive potassium channel subunit Kir6.2 in PBLs were analyzed using quantitative real-time PCR among 20 PD patients with medication, 10 PD patients without medication and 16 healthy controls, respectively. The results showed that there was a significantly decrease of the D2, D3 mRNA expression in PBLs of PD patients compared with that in healthy controls. The four inward rectified potassium channels Kir2.1, Kir2.2, Kir2.3, and Kir2.4 mRNA expression in PBLs from PD patients were also significantly down-regulated than that from age-matched healthy controls. However, there was no apparent difference in expression of another potassium channel Kir6.2 mRNA between PD patients and healthy controls. We proposed that the Kir2 potassium channels mRNA on blood lymphocytes may be regarded as a potential biomarker for PD screening.
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Affiliation(s)
- Ya-Xing Gui
- Department of Neurology & Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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15
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Potassium channel expression in adult murine neural progenitor cells. Neuroscience 2011; 180:19-29. [PMID: 21329741 DOI: 10.1016/j.neuroscience.2011.02.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 01/08/2011] [Accepted: 02/08/2011] [Indexed: 11/21/2022]
Abstract
Neural progenitor cells (NPCs) are a source of new neurons and glia in the adult brain. Most NPCs reside in the forebrain subventricular zone (SVZ) and in the subgranular zone of the dentate gyrus, where they contribute to plasticity in the adult brain. To use their potential for repair, it is essential to identify the molecules that regulate their growth, migration and differentiation. Potassium (K+) channels are promising molecule candidates for NPC regulation as they are important components of signal transduction and their diversity is ideal to cover the complex functions required for cell proliferation and differentiation. There is increasing evidence that K+ channels influence cell growth and neurogenesis, however, very little is known regarding K+ channel distribution in NPCs. We therefore explored the expression of a variety of voltage-gated (Kv), inwardly rectifying (Kir) and two-pore (K2P) K+ channels in the SVZ of adult mice and in neurosphere cultures of NPCs during growth and differentiation. Immunocytochemical analysis revealed a differential expression pattern of K+ channels in nestin+ SVZ precursor cells, early SVZ doublecortin+ neurons and (sub)ependymal cells. These findings were confirmed in neurosphere cultures at the protein and mRNA levels. The expression of some K+ channel proteins, such as Kir4.1, Kir6.1, TREK1 or TASK1, suggests a role of K+ channels in the complex regulation of NPC proliferation, maturation and differentiation.
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16
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A KCNJ6 (Kir3.2, GIRK2) gene polymorphism modulates opioid effects on analgesia and addiction but not on pupil size. Pharmacogenet Genomics 2010; 20:291-7. [PMID: 20220551 DOI: 10.1097/fpc.0b013e3283386bda] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIM KCNJ6 coding for potassium inwardly rectifying channels (Kir3.2, GIRK2) is important for opioid receptor transmission. The KCNJ6 rs2070995 AA genotype has been associated with increased opioid analgesic requirements in Japanese. We analyzed its consequences for other opioid effects. METHODS Genotyping was done in 85 methadone-substituted former heroin addicts, 352 opioid-treated chronic pain patients, and in 51 healthy volunteers where miotic effects of levomethadone had been measured. Expression of Kir3.2 in the Edinger-Westphal nucleus of rat brains was analyzed by means of immunohistochemistry. RESULTS Average daily methadone substitution doses during the first therapy year were larger in the AA genotype (n=4, 119.7+/-49.6 mg/day) than in other rs2070995 genotypes (77.5+/-26.2 mg/day, P=0.003) whereas AA carriers lacked opioid withdrawal symptoms. A similar tendency toward less opioid effectiveness was observed toward higher opioid dosing demands for analgesia in the AA genotype (n=17, opioid dose 2.03+/-0.45 log mg oral morphine equivalents per day, controls: 1.81+/-0.52 log mg oral morphine equivalents/day, P=0.093). In contrast, no pharmacogenetic effects were observed on miotic opioid effects. This could be traced back to the absence of Kir3.2 from the Edinger-Westphal nucleus in rat brains, a key cerebral structure governing pupil constriction. CONCLUSION The association of the KCNJ6 rs2070995 AA genotype with increased opioid requirements extends from analgesia to opiate substitution therapy. Opioid induced miosis is exempted for molecular histological reasons.
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Luján R. Organisation of potassium channels on the neuronal surface. J Chem Neuroanat 2010; 40:1-20. [PMID: 20338235 DOI: 10.1016/j.jchemneu.2010.03.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 03/10/2010] [Accepted: 03/11/2010] [Indexed: 11/30/2022]
Abstract
Potassium channels are a family of ion channels that govern the intrinsic electrical properties of neurons in the brain. Molecular cloning has revealed over 100 genes encoding the pore-forming alpha subunits of potassium channels in mammals, making them the most diverse subset of ion channels. Multiplicity in this ion channel family is further generated through alternative splicing. The precise location of potassium channels along the dendro-somato-axonic surface of the neurons is an important factor in determining its functional impact. Today, it is widely accepted that potassium channels can be located at any subcellular compartment on the neuronal surface, at synaptic and extrasynaptic sites, from somata to dendritic shafts, dendritic spines, axons or axon terminals. However, they are not evenly distributed on the neuronal surface and depending on the potassium channel subtype, are instead concentrated at different compartments. This selective localization of ion channels to specific neuronal compartments has many different functional implications. One factor necessary to understand the role of potassium channels in neuronal function is to unravel their specialized distribution and subcellular localization within a cell, and this can only be achieved by electron microscopy. In this review, I summarize anatomical findings, describing their distribution in the central nervous system. The distinct regional, cellular and subcellular distribution of potassium channels in the brain will be discussed in view of their possible functional implications.
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Affiliation(s)
- Rafael Luján
- Departamento de Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006 Albacete, Spain.
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18
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Abstract
To date, most of the major types of Kir channels, Kir2s, Kir3s, Kir4s, and Kir6s, have been found to partition into cholesterol-rich membrane domains and/or to be regulated by changes in the level of membrane cholesterol. Surprisingly, however, in spite of the structural similarities between different Kirs, effects of cholesterol on different types of Kir channels vary from cholesterol-induced decrease in the current density (Kir2 channels) to the loss of channel activity by cholesterol depletion (Kir4 channels) and loss of channel coupling by different mediators (Kir3 and Kir6 channels). Recently, we have gained initial insights into the mechanisms responsible for cholesterol-induced suppression Kir2 channels, but mechanisms underlying cholesterol sensitivity of other Kir channels are mostly unknown. The goal of this review is to present a summary of the current knowledge of the distinct effects of cholesterol on different types of Kir channels in vitro and in vivo.
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Affiliation(s)
- Irena Levitan
- Department of Medicine, Pulmonary Section, University of Illinois at Chicago, Chicago, IL 60612, USA.
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19
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Young CC, Stegen M, Bernard R, Müller M, Bischofberger J, Veh RW, Haas CA, Wolfart J. Upregulation of inward rectifier K+ (Kir2) channels in dentate gyrus granule cells in temporal lobe epilepsy. J Physiol 2009; 587:4213-33. [PMID: 19564397 DOI: 10.1113/jphysiol.2009.170746] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
In humans, temporal lobe epilepsy (TLE) is often associated with Ammon's horn sclerosis (AHS) characterized by hippocampal cell death, gliosis and granule cell dispersion (GCD) in the dentate gyrus. Granule cells surviving TLE have been proposed to be hyperexcitable and to play an important role in seizure generation. However, it is unclear whether this applies to conditions of AHS. We studied granule cells using the intrahippocampal kainate injection mouse model of TLE, brain slice patch-clamp recordings, morphological reconstructions and immunocytochemistry. With progressing AHS and GCD, 'epileptic' granule cells of the injected hippocampus displayed a decreased input resistance, a decreased membrane time constant and an increased rheobase. The resting leak conductance was doubled in epileptic granule cells and roughly 70-80% of this difference were sensitive to K(+) replacement. Of the increased K(+) leak, about 50% were sensitive to 1 mm Ba(2+). Approximately 20-30% of the pathological leak was mediated by a bicuculline-sensitive GABA(A) conductance. Epileptic granule cells had strongly enlarged inwardly rectifying currents with a low micromolar Ba(2+) IC(50), reminiscent of classic inward rectifier K(+) channels (Irk/Kir2). Indeed, protein expression of Kir2 subunits (Kir2.1, Kir2.2, Kir2.3, Kir2.4) was upregulated in epileptic granule cells. Immunolabelling for two-pore weak inward rectifier K(+) channels (Twik1/K2P1.1, Twik2/K2P6.1) was also increased. We conclude that the excitability of granule cells in the sclerotic focus of TLE is reduced due to an increased resting conductance mainly due to upregulated K(+) channel expression. These results point to a local adaptive mechanism that could counterbalance hyperexcitability in epilepsy.
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Affiliation(s)
- Christina C Young
- Cellular Neurophysiology, Dept. of Neurosurgery, University Medical Center Freiburg, Breisacher Str. 64, 79106 Freiburg, Germany
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20
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Blomeley CP, Bracci E. Serotonin excites fast-spiking interneurons in the striatum. Eur J Neurosci 2009; 29:1604-14. [PMID: 19419423 PMCID: PMC2695856 DOI: 10.1111/j.1460-9568.2009.06725.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Revised: 02/18/2009] [Accepted: 02/19/2009] [Indexed: 11/29/2022]
Abstract
Fast-spiking interneurons (FSIs) control the output of the striatum by mediating feed-forward GABAergic inhibition of projection neurons. Their neuromodulation can therefore critically affect the operation of the basal ganglia. We studied the effects of 5-hydroxytryptamine (5-HT, serotonin), a neurotransmitter released in the striatum by fibres originating in the raphe nuclei, on FSIs recorded with whole-cell techniques in rat brain slices. Bath application of serotonin (30 microm) elicited slow, reversible depolarizations (9 +/- 3 mV) in 37/46 FSIs. Similar effects were observed using conventional whole-cell and gramicidin perforated-patch techniques. The serotonin effects persisted in the presence of tetrodotoxin and were mediated by 5-HT(2C) receptors, as they were reversed by the 5-HT(2) receptor antagonist ketanserin and by the selective 5-HT(2C) receptor antagonist RS 102221. Serotonin-induced depolarizations were not accompanied by a significant change in FSI input resistance. Serotonin caused the appearance of spontaneous firing in a minority (5/35) of responsive FSIs, whereas it strongly increased FSI excitability in each of the remaining responsive FSIs, significantly decreasing the latency of the first spike evoked by a current step and increasing spike frequency. Voltage-clamp experiments revealed that serotonin suppressed a current that reversed around -100 mV and displayed a marked inward rectification, a finding that explains the lack of effects of serotonin on input resistance. Consistently, the effects of serotonin were completely occluded by low concentrations of extracellular barium, which selectively blocks Kir2 channels. We concluded that the excitatory effects of serotonin on FSIs were mediated by 5-HT(2C) receptors and involved suppression of an inwardly rectifying K(+) current.
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Affiliation(s)
- Craig P Blomeley
- University of Manchester, Faculty of Life Sciences, AV Hill Building, Oxford Road, Manchester M13 9PT, UK
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21
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Dhingra A, Sulaiman P, Xu Y, Fina ME, Veh RW, Vardi N. Probing neurochemical structure and function of retinal ON bipolar cells with a transgenic mouse. J Comp Neurol 2008; 510:484-96. [PMID: 18671302 DOI: 10.1002/cne.21807] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Retinal ON bipolar cells make up about 70% of all bipolar cells. Glutamate hyperpolarizes these cells by binding to the metabotropic glutamate receptor mGluR6, activating the G-protein G(o1), and closing an unidentified cation channel. To facilitate investigation of ON bipolar cells, we here report on the production of a transgenic mouse (Grm6-GFP) in which enhanced green fluorescent protein (EGFP), under control of mGluR6 promoter, was expressed in all and only ON bipolar cells. We used the mouse to determine density of ON bipolar cells, which in central retina was 29,600 cells/mm(2). We further sorted the fluorescent cells and created a pure ON bipolar cDNA library that was negative for photoreceptor unique genes. With this library, we determined expression of 27 genes of interest. We obtained positive transcripts for G(o) interactors: regulators of G-protein signaling (RGS), Ret-RGS1 (a variant of RGS20), RGS16, RGS7, purkinje cell protein 2 (PCP2, also called L7 or GPSM4), synembryn (RIC-8), LGN (GPSM2), RAP1GAP, and Gbeta5; cGMP modulators: guanylyl cyclase (GC) 1alpha1, GC1beta1, phosphodiesterase (PDE) 1C, and PDE9A; and channels: inwardly rectifying potassium channel Kir2.4, transient receptor potential TRPC2, and sperm-specific cation channels CatSper 2-4. The following transcripts were not found in our library: AGS3 (GPSM1), RGS10, RGS19 (GAIP), calbindin, GC1alpha2, GC1beta2, PDE5, PDE2A, amiloride-sensitive sodium channel ACCN4, and CatSper1. We then localized Kir2.4 to several cell types and showed that, in ON bipolar cells, the channel concentrates in their dendritic tips. The channels and modulators found in ON bipolar cells likely shape their light response. Additional uses of the Grm6-GFP mouse are also discussed.
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Affiliation(s)
- Anuradha Dhingra
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6058, USA
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22
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Szalisznyó K, Müller L. Dopamine induced switch in the subthreshold dynamics of the striatal cholinergic interneurons: a numerical study. J Theor Biol 2008; 256:547-60. [PMID: 18976672 DOI: 10.1016/j.jtbi.2008.09.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 09/12/2008] [Accepted: 09/12/2008] [Indexed: 11/25/2022]
Abstract
The striatum is a part of the basal ganglia, which are a group of nuclei in the brain associated with motor control, cognition and learning. Striatal cholinergic interneurons (AchNs) play a crucial role in these functions. AchNs are tonically active in vivo and in vitro, and are able to fire in the absence of synaptic inputs. AchNs respond to sensory stimuli and sensorimotor learning by transiently suppressing their firing activity. This pause is dopamine signal sensitive, but the neurophysiological mechanism of the dopaminergic influence is under debate. Both the regular spiking response as well as the pause response are influenced by the inwardly rectifying outward G(kir), a slow hyperpolarization activated noninactivating G(h), and calcium and calcium-dependent potassium conductances [Wilson, C., Goldberg, J., 2006. Origin of the slow afterhyperpolarization and slow rhythmic bursting in striatal cholinergic interneurons. J. Neurophysiol. 95(1), 196-204; Wilson, C., 2005. The mechanism of intrinsic amplification of hyperpolarizations and spontaneous bursting in striatal cholinergic interneurons. Neuron 45(4), 575-585]. Recent experimental evidence has shown that dopaminergic modulations on G(h), G(kir) and calcium conductances influence the AchN's excitability [Deng, P., Zhang, Y., Xu, Z., 2007. Involvement of I(h) in dopamine modulation of tonic firing in striatal cholinergic interneurons. J. Neurosci. 27(12), 3148-3156; Aosaki, T., Kiuchi, K., Kawaguchi, Y., 1998. Dopamine D(1)-like receptor activation excites rat striatal large aspiny neurons in vitro. J. Neurosci. 18(14), 5180-5190]. We employed computational models of the AchN to analyze the conductance based dopaminergic changes. We analyzed the robustness of these subthreshold oscillations and how they are affected by dopaminergic modulation. Our results predict that these conductances allow the dopamine to switch the AchN between stable oscillatory and fixed-point behaviors. The present approach and results show that dopamine receptors (D(1) and D(2)) mediate opposing effects on this switch and therefore on the suprathreshold excitability as well. The switching effect of the dopaminergic signal is the major qualitative feature that can serve as a building block for higher network-level descriptions. To our knowledge this is the first paper that synthesizes the growing body of experimental literature about the dopaminergic modulation of the AchNs into a modelling framework.
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Affiliation(s)
- Krisztina Szalisznyó
- Department of Biophysics, KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
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23
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Wang G, Zeng J, Shen CY, Wang ZQ, Chen SD. Overexpression of Kir2.3 in PC12 cells resists rotenone-induced neurotoxicity associated with PKC signaling pathway. Biochem Biophys Res Commun 2008; 374:204-9. [DOI: 10.1016/j.bbrc.2008.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 07/01/2008] [Indexed: 12/23/2022]
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Wang Y, Yang PL, Tang JF, Lin JF, Cai XH, Wang XT, Zheng GQ. Potassium channels: possible new therapeutic targets in Parkinson's disease. Med Hypotheses 2008; 71:546-50. [PMID: 18650029 DOI: 10.1016/j.mehy.2008.05.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2008] [Revised: 05/11/2008] [Accepted: 05/12/2008] [Indexed: 10/21/2022]
Abstract
Parkinson's disease (PD) is one of the most common neurodegenerative disorders and still remains incurable. New targets for potential pharmacological intervention should be explored and evaluated in order to slow down, delay or reverse the progress of this disease, and/or to avoid the serious side effects of levodopa praeparatum. Potassium (K+) channels widely express in basal ganglia and play crucial roles in the pathophysiology of PD, thereby raising their therapeutic application. Based on data from some pilot studies, we propose that K+ channels may provide possible new therapeutic targets for slowing down the progressive loss of dopamine neurons in PD. The most promising targets of K+ channels, including Kv, KATP, Kir, SK, and K2P channels, etc. deserve further pursuit for making comprehensive use of their novel therapeutic potential. Attempts to confirm this hypothesis may lead to new therapeutic strategy of PD.
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Affiliation(s)
- Yan Wang
- Department of Internal Medicine, The Second Affiliated Hospital of Wenzhou Medical College, 325027 Wenzhou, China
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25
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Over-expression of the potassium channel Kir2.3 using the dopamine-1 receptor promoter selectively inhibits striatal neurons. Neuroscience 2008; 155:114-27. [PMID: 18571331 DOI: 10.1016/j.neuroscience.2008.04.075] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 04/03/2008] [Accepted: 04/16/2008] [Indexed: 10/22/2022]
Abstract
Dysfunction of basal ganglia circuits underlies a variety of movement disorders and neuropsychiatric conditions. Selective control of the electrical activity of striatal outflow pathways by manipulation of ion channel function presents a novel therapeutic approach. Toward this end, we have constructed and studied in vitro an adenoviral gene transfer vector that employs the promoter region of the dopamine-1 receptor to drive expression of the inward rectifier K(+) channel Kir2.3. The use of this neuronal promoter confers cell-type specificity and a physiological level of trans-gene expression in rat primary striatal cultures. The electrophysiological properties were confirmed in transfected human embryonic kidney cells, in which an inwardly-rectifying, Cs(+)-sensitive current was measured by voltage clamp. Current clamp studies of transduced striatal neurons demonstrated an increase in the firing threshold, latency to first action potential and decrease in neuronal excitability. Neurotoxin-induced activation of c-Fos, a marker of neuronal activity, was blocked in transduced neurons indicating that the decrease in electrical excitability was physiologically significant. When used in vivo, this strategy may have the potential to positively impact movement disorders by selectively changing activity of neurons belonging to the direct striatal pathway, characterized by the expression of dopamine-1 receptors.
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26
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Moyer JT, Wolf JA, Finkel LH. Effects of dopaminergic modulation on the integrative properties of the ventral striatal medium spiny neuron. J Neurophysiol 2007; 98:3731-48. [PMID: 17913980 DOI: 10.1152/jn.00335.2007] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopaminergic modulation produces a variety of functional changes in the principal cell of the striatum, the medium spiny neuron (MSN). Using a 189-compartment computational model of a ventral striatal MSN, we simulated whole cell D1- and D2-receptor-mediated modulation of both intrinsic (sodium, calcium, and potassium) and synaptic currents (AMPA and NMDA). Dopamine (DA) modulations in the model were based on a review of published experiments in both ventral and dorsal striatum. To objectively assess the net effects of DA modulation, we combined reported individual channel modulations into either D1- or D2-receptor modulation conditions and studied them separately. Contrary to previous suggestions, we found that D1 modulation had no effect on MSN nonlinearity and could not induce bistability. In agreement with previous suggestions, we found that dopaminergic modulation leads to changes in input filtering and neuronal excitability. Importantly, the changes in neuronal excitability agree with the classical model of basal ganglia function. We also found that DA modulation can alter the integration time window of the MSN. Interestingly, the effects of DA modulation of synaptic properties opposed the effects of DA modulation of intrinsic properties, with the synaptic modulations generally dominating the net effect. We interpret this lack of synergy to suggest that the regulation of whole cell integrative properties is not the primary functional purpose of DA. We suggest that D1 modulation might instead primarily regulate calcium influx to dendritic spines through NMDA and L-type calcium channels, by both direct and indirect mechanisms.
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Affiliation(s)
- Jason T Moyer
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
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27
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Shen W, Tian X, Day M, Ulrich S, Tkatch T, Nathanson NM, Surmeier DJ. Cholinergic modulation of Kir2 channels selectively elevates dendritic excitability in striatopallidal neurons. Nat Neurosci 2007; 10:1458-66. [PMID: 17906621 DOI: 10.1038/nn1972] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Accepted: 08/03/2007] [Indexed: 11/08/2022]
Abstract
Dopamine-depleting lesions of the striatum that mimic Parkinson's disease induce a profound pruning of spines and glutamatergic synapses in striatopallidal medium spiny neurons, leaving striatonigral medium spiny neurons intact. The mechanisms that underlie this cell type-specific loss of connectivity are poorly understood. The Kir2 K(+) channel is an important determinant of dendritic excitability in these cells. Here we show that opening of these channels is potently reduced by signaling through M1 muscarinic receptors in striatopallidal neurons, but not in striatonigral neurons. This asymmetry could be attributed to differences in the subunit composition of Kir2 channels. Dopamine depletion alters the subunit composition further, rendering Kir2 channels in striatopallidal neurons even more susceptible to modulation. Reduced opening of Kir2 channels enhances dendritic excitability and synaptic integration. This cell type-specific enhancement of dendritic excitability is an essential trigger for synaptic pruning after dopamine depletion, as pruning was prevented by genetic deletion of M1 muscarinic receptors.
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Affiliation(s)
- Weixing Shen
- Department of Physiology and Institute of Neuroscience, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Chicago, Illinois 60611, USA
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Eulitz D, Prüss H, Derst C, Veh RW. Heterogeneous Distribution of Kir3 Potassium Channel Proteins Within Dopaminergic Neurons in the Mesencephalon of the Rat Brain. Cell Mol Neurobiol 2007; 27:285-302. [PMID: 17235695 DOI: 10.1007/s10571-006-9118-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 09/06/2006] [Indexed: 11/25/2022]
Abstract
1. Dopaminergic neurons in the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) of the ventral mesencephalon play an important role in the regulation of the parallel basal ganglia loops.2. We have raised affinity-purified polyclonal rabbit antibodies specific for all four members of the Kir3 family of inwardly rectifying potassium channels (Kir3.1-Kir3.4) to investigate the distribution of the channel proteins in the dopaminergic neurons of the rat mesencephalon at light and electron microscopic level. In addition, immunocytochemical double labeling with tyrosine hydroxylase (TH), a marker of dopaminergic neurons, were performed.3. All Kir3 channels were present in this region. However, the individual proteins showed differential cellular and subcellular distributions.4. Kir3.1 immunoreactivity was found in SNc fibers and some neurons of the substantia nigra pars reticulata (SNr). Few Kir3.3-positive neurons were found in the SNc. However, a strong Kir3.3 signal was identified in the SNr neuropil. Weak Kir3.4 staining was detected in neuronal somata as well as in dendritic fibers of both parts of the SN.5. In the VTA, Kir3.1, Kir3.3, and Kir3.4 showed only weak staining of neuropil structures. The distribution of the Kir3.2 channel protein was especially striking with strong labeling in the SNc and in the lateral but not central VTA.6. Our results suggest that the heterogeneously distributed Kir3.2 channel proteins could help to discriminate the dopaminergic neurons of VTA and SNc.
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Affiliation(s)
- Dirk Eulitz
- Centrum für Anatomie, Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstrasse 12, D-10115 Berlin, Germany
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Falk T, Xiang S, Erbe EL, Sherman SJ. Neurochemical and electrophysiological characteristics of rat striatal neurons in primary culture. J Comp Neurol 2006; 494:275-89. [PMID: 16320238 PMCID: PMC2923039 DOI: 10.1002/cne.20819] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neurons maintained in dispersed primary culture offer a number of advantages as a model system and are particularly well-suited for studies of the intrinsic electrical properties of neurons by patch clamp. We have characterized the immunocytochemical and electrophysiological properties of cultured rat striatal neurons as they develop in vitro in order to compare this model system with the known properties found in vivo. We found a high abundance of cells in vitro corresponding to the principal striatal output neuron, the medium spiny neuron. Immunocytochemical studies indicate that these cells have both dopamine-1 and dopamine-2 receptors and that there is overlap in their expression within the population of neurons. Semiquantitative analysis revealed bimodal distributions of dopamine receptor expression among the population of neurons. The principal peptide neurotransmitters substance P and enkephalin were present but at reduced levels compared with adult preparations. Other striatal markers such as calbindin, calretinin, and the cannabinoid-1 receptor were abundant. An immunocytochemical survey of voltage-gated K(+) channel subunits characteristic of adult tissue demonstrated the presence in vitro of Kv1.1, Kv1.4, Kv4.2, Kv4.3, and Kvbeta1.1, which have been associated with the rapidly inactivating currents. Electrophysiological studies employing voltage clamp revealed that outward currents had a large inactivating (A-type) component characteristic of mature basal ganglia. Current clamp studies reveal complex spontaneous firing patterns in a subset of neurons, including bursting behaviors superimposed on a slow depolarization. The inward rectifying channels Kir2.1 and Kir2.3, which are specific to particular compartments in adult striatum, were present in culture.
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Affiliation(s)
- Torsten Falk
- The University of Arizona, Depts. of Neurology and Physiology
| | - ShiLing Xiang
- The University of Arizona, Depts. of Neurology and Physiology
| | - Emilie L. Erbe
- The University of Arizona, Depts. of Neurology and Physiology
| | - Scott J. Sherman
- The University of Arizona, Depts. of Neurology and Physiology
- Correspondence to: The University of Arizona, Dept. of Neurology, 1501 N. Campbell Ave, Tucson, AZ 85724-5023. , Telephone: 520-626-2319, Fax: 550-626-5999
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30
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Prüss H, Derst C, Lommel R, Veh RW. Differential distribution of individual subunits of strongly inwardly rectifying potassium channels (Kir2 family) in rat brain. ACTA ACUST UNITED AC 2005; 139:63-79. [PMID: 15936845 DOI: 10.1016/j.molbrainres.2005.05.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 05/03/2005] [Accepted: 05/09/2005] [Indexed: 11/21/2022]
Abstract
Inwardly rectifying potassium (Kir) channels modulate cellular excitability, membrane potential, and secretion of neurotransmitters and hormones. Kir channels with the strongest inward rectification belong to the Kir2 family. In this report, polyclonal monospecific affinity-purified antibodies against the less conserved carboxy-terminal sequences of Kir2.1, Kir2.2, Kir2.3, and Kir2.4 were used to analyze the detailed distribution of all members of the Kir2 family in the rat central nervous system. Kir2 channel expression is detected in neurons but not in glial cells. Kir2 protein distribution confirms the basic mRNA localization pattern given by in situ hybridization. Kir2.1 is detected throughout the whole brain but in particular subsets of neurons with highest expression in olfactory bulb and superior colliculus. Kir2.2 immunoreactivity is primarily displayed in several forebrain nuclei, hypothalamus, cerebellum, and spinal cord. The Kir2.3 subunit is predominantly localized in olfactory bulb, basal ganglia, cortex, and cerebellar Purkinje cells. In contrast, Kir2.4-positive staining is detected at significantly lower levels in most neurons throughout the rat brain with highest expression in brainstem motoneurons. Thus, our data show a more widespread distribution of Kir2.4 than previously determined. In summary, the widespread presence of all four Kir2 channel subunits in the rat brain provides further evidence for their important role in central signal processing and neural transmission.
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Affiliation(s)
- Harald Prüss
- Centrum für Anatomie der Charité, Universitätsklinikum der Humboldt-Universität Berlin, Philippstr. 12,10115 Berlin, Germany
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31
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Wolf JA, Moyer JT, Lazarewicz MT, Contreras D, Benoit-Marand M, O'Donnell P, Finkel LH. NMDA/AMPA ratio impacts state transitions and entrainment to oscillations in a computational model of the nucleus accumbens medium spiny projection neuron. J Neurosci 2005; 25:9080-95. [PMID: 16207867 PMCID: PMC6725747 DOI: 10.1523/jneurosci.2220-05.2005] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We describe a computational model of the principal cell in the nucleus accumbens (NAcb), the medium spiny projection (MSP) neuron. The model neuron, constructed in NEURON, includes all of the known ionic currents in these cells and receives synaptic input from simulated spike trains via NMDA, AMPA, and GABAA receptors. After tuning the model by adjusting maximal current conductances in each compartment, the model cell closely matched whole-cell recordings from an adult rat NAcb slice preparation. Synaptic inputs in the range of 1000-1300 Hz are required to maintain an "up" state in the model. Cell firing in the model required concurrent depolarization of several dendritic branches, which responded independently to afferent input. Depolarization from action potentials traveled to the tips of the dendritic branches and increased Ca2+ influx through voltage-gated Ca2+ channels. As NMDA/AMPA current ratios were increased, the membrane showed an increase in hysteresis of "up" and "down" state dwell times, but intrinsic bistability was not observed. The number of oscillatory inputs required to entrain the model cell was determined to be approximately 20% of the "up" state inputs. Altering the NMDA/AMPA ratio had a profound effect on processing of afferent input, including the ability to entrain to oscillations in afferent input in the theta range (4-12 Hz). These results suggest that afferent information integration by the NAcb MSP cell may be compromised by pathology in which the NMDA current is altered or modulated, as has been proposed in both schizophrenia and addiction.
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Affiliation(s)
- John A Wolf
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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32
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Fang Y, Schram G, Romanenko VG, Shi C, Conti L, Vandenberg CA, Davies PF, Nattel S, Levitan I. Functional expression of Kir2.x in human aortic endothelial cells: the dominant role of Kir2.2. Am J Physiol Cell Physiol 2005; 289:C1134-44. [PMID: 15958527 DOI: 10.1152/ajpcell.00077.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Inward rectifier K+channels (Kir) are a significant determinant of endothelial cell (EC) membrane potential, which plays an important role in endothelium-dependent vasodilatation. In the present study, several complementary strategies were applied to determine the Kir2 subunit composition of human aortic endothelial cells (HAECs). Expression levels of Kir2.1, Kir2.2, and Kir2.4 mRNA were similar, whereas Kir2.3 mRNA expression was significantly weaker. Western blot analysis showed clear Kir2.1 and Kir2.2 protein expression, but Kir2.3 protein was undetectable. Functional analysis of endothelial inward rectifier K+current ( IK) demonstrated that 1) IKcurrent sensitivity to Ba2+and pH were consistent with currents determined using Kir2.1 and Kir2.2 but not Kir2.3 and Kir2.4, and 2) unitary conductance distributions showed two prominent peaks corresponding to known unitary conductances of Kir2.1 and Kir2.2 channels with a ratio of ∼4:6. When HAECs were transfected with dominant-negative (dn)Kir2.x mutants, endogenous current was reduced ∼50% by dnKir2.1 and ∼85% by dnKir2.2, whereas no significant effect was observed with dnKir2.3 or dnKir2.4. These studies suggest that Kir2.2 and Kir2.1 are primary determinants of endogenous K+conductance in HAECs under resting conditions and that Kir2.2 provides the dominant conductance in these cells.
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Affiliation(s)
- Yun Fang
- Institute for Medicine and Engineering, University of Pennsylvania, 1160 Vagelos Research Labs, 3340 Smith Walk, Philadelphia, PA 19104, USA
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33
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Ariano MA, Wagle N, Grissell AE. Neuronal vulnerability in mouse models of Huntington's disease: membrane channel protein changes. J Neurosci Res 2005; 80:634-45. [PMID: 15880743 DOI: 10.1002/jnr.20492] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Huntington's disease (HD) is caused by a polyglutamine expansion that results in atrophy of the striatum and frontal cortex during disease progression. HD-susceptible striatal neurons are affected chronologically with initial degeneration of the striatopallidal neurons then the striatonigral projections, whereas large aspiny striatal interneurons (LAN) survive. Two classes of critical membrane proteins were evaluated in transgenic mouse models to determine their association with HD susceptibility, which leads to dysfunction and death in selected striatal neuron populations. We examined potassium (K+) channel protein subunits that form membrane ionophores conducting inwardly and outwardly rectifying K+ currents. K+ channel protein staining was diminished substantially in the HD striatal projection neurons but was not expressed in the HD-resistant LAN. Because loss of K+ channel subunits depolarizes neurons, other voltage-gated ionophores will be affected. N-methyl-D-aspartate (NMDA) receptors and their phosphorylation by cyclic AMP were studied as a mechanism contributing to excitotoxic vulnerability in striatal projection neurons that would lose voltage regulation after diminished K+ channels. NR1 subunits showed significant elevation in the HD transgenic projection systems but were expressed at very low levels in LAN. NR1 subunit phosphorylation by cyclic AMP also was enhanced in striatal projection neurons but not in LAN. Cyclic AMP-driven phosphorylation of NMDA receptors increases the channel open time and elevates neuronal glutamate responsiveness, which may lead to excitotoxicity. Together our data suggest that changes in these proteins and their modification may predispose striatal projection neurons to dysfunction and then degeneratation in HD and provide a mechanism for LAN resistance in the disease.
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Affiliation(s)
- Marjorie A Ariano
- Department of Neuroscience, The Chicago Medical School at Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064-3095, USA.
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Ariano MA, Cepeda C, Calvert CR, Flores-Hernández J, Hernández-Echeagaray E, Klapstein GJ, Chandler SH, Aronin N, DiFiglia M, Levine MS. Striatal potassium channel dysfunction in Huntington's disease transgenic mice. J Neurophysiol 2004; 93:2565-74. [PMID: 15625098 DOI: 10.1152/jn.00791.2004] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder that mainly affects the projection neurons of the striatum and cerebral cortex. Genetic mouse models of HD have shown that neurons susceptible to the mutation exhibit morphological and electrophysiological dysfunctions before and during development of the behavioral phenotype. We used HD transgenic mouse models to examine inwardly and outwardly rectifying K+ conductances, as well as expression of some related K+ channel subunits. Experiments were conducted in slices and dissociated cells from two mouse models, the R6/2 and TgCAG100, at the beginning and after full development of overt behavioral phenotypes. Striatal medium-sized spiny neurons (MSNs) from symptomatic transgenic mice had increased input resistances, depolarized resting membrane potentials, and reductions in both inwardly and outwardly rectifying K+ currents. These changes were more dramatic in the R6/2 model than in the TgCAG100. Parallel immunofluorescence studies detected decreases in the expression of K+ channel subunit proteins, Kir2.1, Kir2.3, and Kv2.1 in MSNs, which contribute to the formation of the channel ionophores for these currents. Attenuation in K+ conductances and channel subunit expression contribute to altered electrophysiological properties of MSNs and may partially account for selective cellular vulnerability in the striatum.
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Affiliation(s)
- Marjorie A Ariano
- Mental Retardation Research Center, NPI Room 58-258, 760 Westwood Plaza, University of California, Los Angeles, CA 90095, USA
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Romanenko VG, Fang Y, Byfield F, Travis AJ, Vandenberg CA, Rothblat GH, Levitan I. Cholesterol sensitivity and lipid raft targeting of Kir2.1 channels. Biophys J 2004; 87:3850-61. [PMID: 15465867 PMCID: PMC1304896 DOI: 10.1529/biophysj.104.043273] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study investigates how changes in the level of cellular cholesterol affect inwardly rectifying K+ channels belonging to a family of strong rectifiers (Kir2). In an earlier study we showed that an increase in cellular cholesterol suppresses endogenous K+ current in vascular endothelial cells, presumably due to effects on underlying Kir2.1 channels. Here we show that, indeed, cholesterol increase strongly suppressed whole-cell Kir2.1 current when the channels were expressed in a null cell line. However, cholesterol level had no effect on the unitary conductance and only little effect on the open probability of the channels. Moreover, no cholesterol effect was observed either on the total level of Kir2.1 protein or on its surface expression. We suggest, therefore, that cholesterol modulates not the total number of Kir2.1 channels in the plasma membrane but rather the transition of the channels between active and silent states. Comparing the effects of cholesterol on members of the Kir2.x family shows that Kir2.1 and Kir2.2 have similar high sensitivity to cholesterol, Kir2.3 is much less sensitive, and Kir2.4 has an intermediate sensitivity. Finally, we show that Kir2.x channels partition virtually exclusively into Triton-insoluble membrane fractions indicating that the channels are targeted into cholesterol-rich lipid rafts.
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Affiliation(s)
- Victor G Romanenko
- Institute for Medicine and Engineering, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Leichtle A, Rauch U, Albinus M, Benöhr P, Kalbacher H, Mack AF, Veh RW, Quast U, Russ U. Electrophysiological and molecular characterization of the inward rectifier in juxtaglomerular cells from rat kidney. J Physiol 2004; 560:365-76. [PMID: 15284349 PMCID: PMC1665251 DOI: 10.1113/jphysiol.2004.070359] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Renin, the key element of the renin-angiotensin-aldosterone system, is mainly produced by and stored in the juxtaglomerular cells in the kidney. These cells are situated in the media of the afferent arteriole close to the vessel pole and can transform into smooth muscle cells and vice versa. In this study, the electrophysiological properties and the molecular identity of the K+ channels responsible for the resting membrane potential (approximately -60 mV) of the juxtaglomerular cells were examined. In order to increase the number of juxtaglomerular cells, afferent arterioles from NaCl-depleted rats were used, and > 90% of the afferent arterioles were renin positive at the distal end of the arteriole. Whole-cell and cell-attached single-channel patch-clamp experiments showed that juxtaglomerular cells are endowed with a strongly inwardly rectifying K+ channel (Kir). The channel was highly sensitive to inhibition by Ba2+ (inhibition constant 37 microM at 0 mV), but relatively insensitive to Cs+ and, with 142 mM K+ in the pipette, had a single-channel conductance of 31.5 pS. Immunocytochemical studies showed the presence of Kir2.1 but no signal for Kir2.2 in the media of the afferent arteriole. In PCR analyses using isolated juxtaglomerular cells, the mRNA for Kir2.1 and Kir2.2 was detected. Collectively, the results show that Kir2.1 is the dominant component of the channel. The current carried by these channels plays a decisive role in setting the membrane potential of juxtaglomerular cells.
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Affiliation(s)
- Anke Leichtle
- Department of Pharmacology and Toxicology, Medical Faculty, University of Tübingen, Wilhelmstrasse 56, D-72074 Tübingen, Germany
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Thomzig A, Prüss H, Veh RW. The Kir6.1-protein, a pore-forming subunit of ATP-sensitive potassium channels, is prominently expressed by giant cholinergic interneurons in the striatum of the rat brain. Brain Res 2003; 986:132-8. [PMID: 12965237 DOI: 10.1016/s0006-8993(03)03222-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
ATP-sensitive potassium channels comprise a complex of two structurally different proteins: a member of the inwardly rectifying Kir6 family (Kir6.1 or Kir6.2) and a sulfonylurea receptor (SUR1 or SUR2). Their regulation by intracellular ADP/ATP-concentrations and through various pharmacological agents has profound implications for the excitability of cells and, in the case of neurons, for neurotransmitter release. We previously showed that in rat brain, the Kir6.1 subunit is predominantly expressed in astrocytes in contrast to the Kir6.2 subunit, which is exclusively expressed in neurons. In this report we show, that in addition to the astrocytic expression, the Kir6.1 protein is also found in a small subset of neurons in distinct areas of the brain, like the hypothalamic supraoptic and paraventricular nuclei and the striatum. The Kir6.1-positive neurons in the striatum could be characterized as cholinergic interneurones, verified by immunofluorescence double staining. This complete colocalization of the Kir6.1 subunit in cholinergic interneurons is interesting with respect to the pharmacological potential of these channels. A selective modulation of the Kir6.1 subunit in the cholinergic striatal interneurons may eventually be of therapeutic value for the treatment of Parkinson's disease.
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Affiliation(s)
- Achim Thomzig
- Institut für Anatomie, der Charité, Universitätsklinikum der Humboldt-Universität zu Berlin, Philippstrasse 12, D-10115 Berlin, Germany
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Martemyanov KA, Hopp JA, Arshavsky VY. Specificity of G protein-RGS protein recognition is regulated by affinity adapters. Neuron 2003; 38:857-62. [PMID: 12818172 DOI: 10.1016/s0896-6273(03)00320-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
RGS proteins regulate the duration of cell signaling by modulating the lifetime of activated G proteins. The specificity of RGS-G protein mutual recognition is critical for meeting unique timing requirements of numerous G protein-mediated pathways. Our study of two splice isoforms of RGS9 expressed in different types of neurons revealed a novel mechanism whereby this specificity is determined by specialized protein domains or subunits acting as affinity adapters. The long RGS9 isoform contains a C-terminal domain that provides high-affinity interaction with its target G protein. The lack of this domain in the short RGS9 isoform is compensated by the action of a G protein effector subunit that is structurally similar to this C-terminal domain. This allows the short isoform to specifically target the complex between the G protein and its effector. Thus, the specific timing needs of different signaling pathways can be accommodated by affinity adapters positioned at various pathway components.
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Affiliation(s)
- Kirill A Martemyanov
- Howe Laboratory of Ophthalmology, Harvard Medical School, The Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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