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Perumal N, Yurugi H, Dahm K, Rajalingam K, Grus FH, Pfeiffer N, Manicam C. Proteome landscape and interactome of voltage-gated potassium channel 1.6 (Kv1.6) of the murine ophthalmic artery and neuroretina. Int J Biol Macromol 2024; 257:128464. [PMID: 38043654 DOI: 10.1016/j.ijbiomac.2023.128464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/14/2023] [Accepted: 11/25/2023] [Indexed: 12/05/2023]
Abstract
The voltage-gated potassium channel 1.6 (Kv1.6) plays a vital role in ocular neurovascular beds and exerts its modulatory functions via interaction with other proteins. However, the interactome and their potential roles remain unknown. Here, the global proteome landscape of the ophthalmic artery (OA) and neuroretina was mapped, followed by the determination of Kv1.6 interactome and validation of its functionality and cellular localization. Microfluorimetric analysis of intracellular [K+] and Western blot validated the native functionality and cellular expression of the recombinant Kv1.6 channel protein. A total of 54, 9 and 28 Kv1.6-interacting proteins were identified in the mouse OA and, retina of mouse and rat, respectively. The Kv1.6-protein partners in the OA, namely actin cytoplasmic 2, alpha-2-macroglobulin and apolipoprotein A-I, were implicated in the maintenance of blood vessel integrity by regulating integrin-mediated adhesion to extracellular matrix and Ca2+ flux. Many retinal protein interactors, particularly the ADP/ATP translocase 2 and cytoskeleton protein tubulin, were involved in endoplasmic reticulum stress response and cell viability. Three common interactors were found in all samples comprising heat shock cognate 71 kDa protein, Ig heavy constant gamma 1 and Kv1.6 channel. This foremost in-depth investigation enriched and identified the elusive Kv1.6 channel and, elucidated its complex interactome.
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Affiliation(s)
- Natarajan Perumal
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Hajime Yurugi
- Cell Biology Unit, University Medical Centre of the Johannes Gutenberg University Mainz, Germany
| | - Katrin Dahm
- Cell Biology Unit, University Medical Centre of the Johannes Gutenberg University Mainz, Germany
| | - Krishnaraj Rajalingam
- Cell Biology Unit, University Medical Centre of the Johannes Gutenberg University Mainz, Germany
| | - Franz H Grus
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Norbert Pfeiffer
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Caroline Manicam
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany.
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2
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Tolone A, Haq W, Fachinger A, Roy A, Kesh S, Rentsch A, Wucherpfennig S, Zhu Y, Groten J, Schwede F, Tomar T, Herberg FW, Nache V, Paquet-Durand F. The PKG Inhibitor CN238 Affords Functional Protection of Photoreceptors and Ganglion Cells against Retinal Degeneration. Int J Mol Sci 2023; 24:15277. [PMID: 37894958 PMCID: PMC10607377 DOI: 10.3390/ijms242015277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/27/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Hereditary retinal degeneration (RD) is often associated with excessive cGMP signalling in photoreceptors. Previous research has shown that inhibition of cGMP-dependent protein kinase G (PKG) can reduce photoreceptor loss in two different RD animal models. In this study, we identified a PKG inhibitor, the cGMP analogue CN238, which preserved photoreceptor viability and functionality in rd1 and rd10 mutant mice. Surprisingly, in explanted retinae, CN238 also protected retinal ganglion cells from axotomy-induced retrograde degeneration and preserved their functionality. Furthermore, kinase activity-dependent protein phosphorylation of the PKG target Kv1.6 was reduced in CN238-treated rd10 retinal explants. Ca2+-imaging on rd10 acute retinal explants revealed delayed retinal ganglion cell repolarization with CN238 treatment, suggesting a PKG-dependent modulation of Kv1-channels. Together, these results highlight the strong neuroprotective capacity of PKG inhibitors for both photoreceptors and retinal ganglion cells, illustrating their broad potential for the treatment of retinal diseases and possibly neurodegenerative diseases in general.
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Affiliation(s)
- Arianna Tolone
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
| | - Wadood Haq
- Neuroretinal Electrophysiology and Imaging, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany;
| | - Alexandra Fachinger
- Biochemistry Department, University of Kassel, 34132 Kassel, Germany; (A.F.); (F.W.H.)
| | - Akanksha Roy
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Sandeep Kesh
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - Andreas Rentsch
- Biolog Life Science Institute GmbH & Co. KG, 28199 Bremen, Germany; (A.R.); (F.S.)
| | - Sophie Wucherpfennig
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - Yu Zhu
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
| | - John Groten
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Frank Schwede
- Biolog Life Science Institute GmbH & Co. KG, 28199 Bremen, Germany; (A.R.); (F.S.)
| | - Tushar Tomar
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Friedrich W. Herberg
- Biochemistry Department, University of Kassel, 34132 Kassel, Germany; (A.F.); (F.W.H.)
| | - Vasilica Nache
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - François Paquet-Durand
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
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3
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Roy A, Tolone A, Hilhorst R, Groten J, Tomar T, Paquet-Durand F. Kinase activity profiling identifies putative downstream targets of cGMP/PKG signaling in inherited retinal neurodegeneration. Cell Death Dis 2022; 8:93. [PMID: 35241647 PMCID: PMC8894370 DOI: 10.1038/s41420-022-00897-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/16/2021] [Accepted: 02/08/2022] [Indexed: 11/15/2022]
Abstract
Inherited retinal diseases (IRDs) are a group of neurodegenerative disorders that lead to photoreceptor cell death and eventually blindness. IRDs are characterised by a high genetic heterogeneity, making it imperative to design mutation-independent therapies. Mutations in a number of IRD disease genes have been associated with a rise of cyclic 3’,5’-guanosine monophosphate (cGMP) levels in photoreceptors. Accordingly, the cGMP-dependent protein kinase (PKG) has emerged as a new potential target for the mutation-independent treatment of IRDs. However, the substrates of PKG and the downstream degenerative pathways triggered by its activity have yet to be determined. Here, we performed kinome activity profiling of different murine organotypic retinal explant cultures (diseased rd1 and wild-type controls) using multiplex peptide microarrays to identify proteins whose phosphorylation was significantly altered by PKG activity. In addition, we tested the downstream effect of a known PKG inhibitor CN03 in these organotypic retina cultures. Among the PKG substrates were potassium channels belonging to the Kv1 family (KCNA3, KCNA6), cyclic AMP-responsive element-binding protein 1 (CREB1), DNA topoisomerase 2-α (TOP2A), 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (F263), and the glutamate ionotropic receptor kainate 2 (GRIK2). The retinal expression of these PKG targets was further confirmed by immunofluorescence and could be assigned to various neuronal cell types, including photoreceptors, horizontal cells, and ganglion cells. Taken together, this study confirmed the key role of PKG in photoreceptor cell death and identified new downstream targets of cGMP/PKG signalling that will improve the understanding of the degenerative mechanisms underlying IRDs.
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Affiliation(s)
- Akanksha Roy
- Division of Toxicology, Wageningen University and Research, 96708 WE, Wageningen, The Netherlands.,PamGene International B.V, 5200 BJ, s-Hertogenbosch, The Netherlands
| | - Arianna Tolone
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität, Tübingen, 72072, Germany
| | - Riet Hilhorst
- PamGene International B.V, 5200 BJ, s-Hertogenbosch, The Netherlands
| | - John Groten
- Division of Toxicology, Wageningen University and Research, 96708 WE, Wageningen, The Netherlands.,PamGene International B.V, 5200 BJ, s-Hertogenbosch, The Netherlands
| | - Tushar Tomar
- PamGene International B.V, 5200 BJ, s-Hertogenbosch, The Netherlands.
| | - François Paquet-Durand
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität, Tübingen, 72072, Germany.
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4
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Rojo Arias JE, Jászai J. Gene expression profile of the murine ischemic retina and its response to Aflibercept (VEGF-Trap). Sci Rep 2021; 11:15313. [PMID: 34321516 PMCID: PMC8319207 DOI: 10.1038/s41598-021-94500-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 07/05/2021] [Indexed: 02/07/2023] Open
Abstract
Ischemic retinal dystrophies are leading causes of acquired vision loss. Although the dysregulated expression of the hypoxia-responsive VEGF-A is a major driver of ischemic retinopathies, implication of additional VEGF-family members in their pathogenesis has led to the development of multivalent anti-angiogenic tools. Designed as a decoy receptor for all ligands of VEGFR1 and VEGFR2, Aflibercept is a potent anti-angiogenic agent. Notwithstanding, the molecular mechanisms mediating Aflibercept's efficacy remain only partially understood. Here, we used the oxygen-induced retinopathy (OIR) mouse as a model system of pathological retinal vascularization to investigate the transcriptional response of the murine retina to hypoxia and of the OIR retina to Aflibercept. While OIR severely impaired transcriptional changes normally ensuing during retinal development, analysis of gene expression patterns hinted at alterations in leukocyte recruitment during the recovery phase of the OIR protocol. Moreover, the levels of Angiopoietin-2, a major player in the progression of diabetic retinopathy, were elevated in OIR tissues and consistently downregulated by Aflibercept. Notably, GO term, KEGG pathway enrichment, and expression dynamics analyses revealed that, beyond regulating angiogenic processes, Aflibercept also modulated inflammation and supported synaptic transmission. Altogether, our findings delineate novel mechanisms potentially underlying Aflibercept's efficacy against ischemic retinopathies.
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Affiliation(s)
- Jesús Eduardo Rojo Arias
- grid.4488.00000 0001 2111 7257Department of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Saxony, Germany ,grid.5335.00000000121885934Present Address: Wellcome-MRC Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, Cambridge Biomedical Campus, University of Cambridge, Cambridge, UK
| | - József Jászai
- grid.4488.00000 0001 2111 7257Department of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Saxony, Germany
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5
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Kessi M, Chen B, Peng J, Tang Y, Olatoutou E, He F, Yang L, Yin F. Intellectual Disability and Potassium Channelopathies: A Systematic Review. Front Genet 2020; 11:614. [PMID: 32655623 PMCID: PMC7324798 DOI: 10.3389/fgene.2020.00614] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/20/2020] [Indexed: 01/15/2023] Open
Abstract
Intellectual disability (ID) manifests prior to adulthood as severe limitations to intellectual function and adaptive behavior. The role of potassium channelopathies in ID is poorly understood. Therefore, we aimed to evaluate the relationship between ID and potassium channelopathies. We hypothesized that potassium channelopathies are strongly associated with ID initiation, and that both gain- and loss-of-function mutations lead to ID. This systematic review explores the burden of potassium channelopathies, possible mechanisms, advancements using animal models, therapies, and existing gaps. The literature search encompassed both PubMed and Embase up to October 2019. A total of 75 articles describing 338 cases were included in this review. Nineteen channelopathies were identified, affecting the following genes: KCNMA1, KCNN3, KCNT1, KCNT2, KCNJ10, KCNJ6, KCNJ11, KCNA2, KCNA4, KCND3, KCNH1, KCNQ2, KCNAB1, KCNQ3, KCNQ5, KCNC1, KCNB1, KCNC3, and KCTD3. Twelve of these genes presented both gain- and loss-of-function properties, three displayed gain-of-function only, three exhibited loss-of-function only, and one had unknown function. How gain- and loss-of-function mutations can both lead to ID remains largely unknown. We identified only a few animal studies that focused on the mechanisms of ID in relation to potassium channelopathies and some of the few available therapeutic options (channel openers or blockers) appear to offer limited efficacy. In conclusion, potassium channelopathies contribute to the initiation of ID in several instances and this review provides a comprehensive overview of which molecular players are involved in some of the most prominent disease phenotypes.
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Affiliation(s)
- Miriam Kessi
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China.,Kilimanjaro Christian Medical University College, Moshi, Tanzania.,Mawenzi Regional Referral Hospital, Moshi, Tanzania
| | - Baiyu Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Yulin Tang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Eleonore Olatoutou
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fang He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Lifen Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
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6
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Wilson AM, Mazzaferri J, Bergeron É, Patskovsky S, Marcoux-Valiquette P, Costantino S, Sapieha P, Meunier M. In Vivo Laser-Mediated Retinal Ganglion Cell Optoporation Using K V1.1 Conjugated Gold Nanoparticles. NANO LETTERS 2018; 18:6981-6988. [PMID: 30285455 DOI: 10.1021/acs.nanolett.8b02896] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Vision loss caused by retinal diseases affects hundreds of millions of individuals worldwide. The retina is a delicate central nervous system tissue stratified into layers of cells with distinct roles. Currently, there is a void in treatments that selectively target diseased retinal cells, and current therapeutic paradigms present complications associated with off-target effects. Herein, as a proof of concept, we introduce an in vivo method using a femtosecond laser to locally optoporate retinal ganglion cells (RGCs) targeted with functionalized gold nanoparticles (AuNPs). We provide evidence that AuNPs functionalized with an antibody toward the cell-surface voltage-gated K+ channel subunit KV1.1 can selectively deliver fluorescently tagged siRNAs or fluorescein isothiocyanate-dextran dye into retinal cells when irradiated with an 800 nm 100 fs laser. Importantly, neither AuNP administration nor irradiation resulted in RGC death. This system provides a novel, non-viral-based approach that has the potential to selectively target retinal cells in diseased regions while sparing healthy areas and may be harnessed in future cell-specific therapies for retinal degenerative diseases.
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Affiliation(s)
- Ariel M Wilson
- Department of Engineering Physics , Polytechnique Montréal , Montreal , Quebec , Canada , H3C 3A7
| | | | - Éric Bergeron
- Department of Engineering Physics , Polytechnique Montréal , Montreal , Quebec , Canada , H3C 3A7
| | - Sergiy Patskovsky
- Department of Engineering Physics , Polytechnique Montréal , Montreal , Quebec , Canada , H3C 3A7
| | - Paule Marcoux-Valiquette
- Department of Engineering Physics , Polytechnique Montréal , Montreal , Quebec , Canada , H3C 3A7
| | | | | | - Michel Meunier
- Department of Engineering Physics , Polytechnique Montréal , Montreal , Quebec , Canada , H3C 3A7
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7
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Cui P, Li XY, Zhao Y, Li Q, Gao F, Li LZ, Yin N, Sun XH, Wang Z. Activation of dopamine D1 receptors enhances the temporal summation and excitability of rat retinal ganglion cells. Neuroscience 2017; 355:71-83. [DOI: 10.1016/j.neuroscience.2017.04.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 04/24/2017] [Accepted: 04/30/2017] [Indexed: 01/11/2023]
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8
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Cameron MA, Al Abed A, Buskila Y, Dokos S, Lovell NH, Morley JW. Differential effect of brief electrical stimulation on voltage-gated potassium channels. J Neurophysiol 2017; 117:2014-2024. [PMID: 28202576 DOI: 10.1152/jn.00915.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 02/13/2017] [Accepted: 02/13/2017] [Indexed: 02/03/2023] Open
Abstract
Electrical stimulation of neuronal tissue is a promising strategy to treat a variety of neurological disorders. The mechanism of neuronal activation by external electrical stimulation is governed by voltage-gated ion channels. This stimulus, typically brief in nature, leads to membrane potential depolarization, which increases ion flow across the membrane by increasing the open probability of these voltage-gated channels. In spiking neurons, it is activation of voltage-gated sodium channels (NaV channels) that leads to action potential generation. However, several other types of voltage-gated channels are expressed that also respond to electrical stimulation. In this study, we examine the response of voltage-gated potassium channels (KV channels) to brief electrical stimulation by whole cell patch-clamp electrophysiology and computational modeling. We show that nonspiking amacrine neurons of the retina exhibit a large variety of responses to stimulation, driven by different KV-channel subtypes. Computational modeling reveals substantial differences in the response of specific KV-channel subtypes that is dependent on channel kinetics. This suggests that the expression levels of different KV-channel subtypes in retinal neurons are a crucial predictor of the response that can be obtained. These data expand our knowledge of the mechanisms of neuronal activation and suggest that KV-channel expression is an important determinant of the sensitivity of neurons to electrical stimulation.NEW & NOTEWORTHY This paper describes the response of various voltage-gated potassium channels (KV channels) to brief electrical stimulation, such as is applied during prosthetic electrical stimulation. We show that the pattern of response greatly varies between KV channel subtypes depending on activation and inactivation kinetics of each channel. Our data suggest that problems encountered when artificially stimulating neurons such as cessation in firing at high frequencies, or "fading," may be attributed to KV-channel activation.
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Affiliation(s)
- Morven A Cameron
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - Yossi Buskila
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and.,Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
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9
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Kaya N, Alsagob M, D'Adamo MC, Al-Bakheet A, Hasan S, Muccioli M, Almutairi FB, Almass R, Aldosary M, Monies D, Mustafa OM, Alyounes B, Kenana R, Al-Zahrani J, Naim E, Binhumaid FS, Qari A, Almutairi F, Meyer B, Plageman TF, Pessia M, Colak D, Al-Owain M. KCNA4 deficiency leads to a syndrome of abnormal striatum, congenital cataract and intellectual disability. J Med Genet 2016; 53:786-792. [PMID: 27582084 DOI: 10.1136/jmedgenet-2015-103637] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 07/20/2016] [Accepted: 08/06/2016] [Indexed: 12/24/2022]
Abstract
BACKGROUND Voltage-gated potassium channels are highly diverse proteins representing the most complex class of voltage-gated ion channels from structural and functional perspectives. Deficiency of these channels usually results in various human disorders. OBJECTIVES To describe a novel autosomal recessive syndrome associated with KCNA4 deficiency leading to congenital cataract, abnormal striatum, intellectual disability and attention deficit hyperactivity disorder. METHODS We used SNP arrays, linkage analyses, autozygosity mapping, whole-exome sequencing, RT-PCR and two-electrode voltage-clamp recording. RESULTS We identified a missense variant (p.Arg89Gln) in KCNA4 in four patients from a consanguineous family manifesting a novel syndrome of congenital cataract, abnormal striatum, intellectual disability and attention deficit hyperactivity disorder. The variant was fully segregated with the disease and absent in 747 ethnically matched exomes. Xenopus oocytes were injected with human Kv1.4 wild-type mRNA, R89Q and WT/R89Q channels. The wild type had mean current amplitude that was significantly greater than those recorded from the cells expressing the same amount of mutant mRNA. Co-expression of the wild type and mutant mRNAs resulted in mean current amplitude that was significantly different from that of the wild type. RT-PCR indicated that KCNA4 is present in mouse brain, lens and retina. KCNA4 interacts with several molecules including synaptotagmin I, DLG1 and DLG2. The channel co-localises with cholinergic amacrine and rod bipolar cells in rats and is widely distributed in the central nervous system. Based on previous studies, the channel is highly expressed in outer retina, rod inner segments, hippocampus and concentrated in axonal membranes. CONCLUSION KCNA4 (Kv1.4) is implicated in a novel syndrome characterised by striatal thinning, congenital cataract and attention deficit hyperactivity disorder. Our study highlights potassium channels' role in ocular and neuronal genetics.
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Affiliation(s)
- Namik Kaya
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Maysoon Alsagob
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Maria Cristina D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia, Italy
| | - Albandary Al-Bakheet
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Sonia Hasan
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia, Italy
| | - Maria Muccioli
- College of Optometry, The Ohio State University, Columbus, Ohio, USA
| | - Faten B Almutairi
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Rawan Almass
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Mazhor Aldosary
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Dorota Monies
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Osama M Mustafa
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.,College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| | - Banan Alyounes
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Rosan Kenana
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Jawaher Al-Zahrani
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Eva Naim
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Faisal S Binhumaid
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Alya Qari
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Fatema Almutairi
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Brian Meyer
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | | | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia, Italy.,Department of Physiology & Biochemistry Faculty of Medicine & Surgery, University of Malta, Msida, Malta
| | - Dilek Colak
- Department of Biostatistics, Epidemiology and Scientific Computing, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Mohammed Al-Owain
- College of Optometry, The Ohio State University, Columbus, Ohio, USA.,College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
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10
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Fohlmeister JF. Voltage gating by molecular subunits of Na+ and K+ ion channels: higher-dimensional cubic kinetics, rate constants, and temperature. J Neurophysiol 2015; 113:3759-77. [PMID: 25867741 DOI: 10.1152/jn.00551.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 03/25/2015] [Indexed: 11/22/2022] Open
Abstract
The structural similarity between the primary molecules of voltage-gated Na and K channels (alpha subunits) and activation gating in the Hodgkin-Huxley model is brought into full agreement by increasing the model's sodium kinetics to fourth order (m(3) → m(4)). Both structures then virtually imply activation gating by four independent subprocesses acting in parallel. The kinetics coalesce in four-dimensional (4D) cubic diagrams (16 states, 32 reversible transitions) that show the structure to be highly failure resistant against significant partial loss of gating function. Rate constants, as fitted in phase plot data of retinal ganglion cell excitation, reflect the molecular nature of the gating transitions. Additional dimensions (6D cubic diagrams) accommodate kinetically coupled sodium inactivation and gating processes associated with beta subunits. The gating transitions of coupled sodium inactivation appear to be thermodynamically irreversible; response to dielectric surface charges (capacitive displacement) provides a potential energy source for those transitions and yields highly energy-efficient excitation. A comparison of temperature responses of the squid giant axon (apparently Arrhenius) and mammalian channel gating yields kinetic Q10 = 2.2 for alpha unit gating, whose transitions are rate-limiting at mammalian temperatures; beta unit kinetic Q10 = 14 reproduces the observed non-Arrhenius deviation of mammalian gating at low temperatures; the Q10 of sodium inactivation gating matches the rate-limiting component of activation gating at all temperatures. The model kinetics reproduce the physiologically large frequency range for repetitive firing in ganglion cells and the physiologically observed strong temperature dependence of recovery from inactivation.
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Affiliation(s)
- Jürgen F Fohlmeister
- Department of Integrative Biology and Physiology and Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Kv3 channels modulate calcium signals induced by fast firing patterns in the rat retinal ganglion cells. Cell Calcium 2012; 52:405-11. [DOI: 10.1016/j.ceca.2012.06.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/20/2012] [Accepted: 06/23/2012] [Indexed: 02/01/2023]
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Weick M, Demb JB. Delayed-rectifier K channels contribute to contrast adaptation in mammalian retinal ganglion cells. Neuron 2011; 71:166-79. [PMID: 21745646 DOI: 10.1016/j.neuron.2011.04.033] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/27/2011] [Indexed: 11/16/2022]
Abstract
Retinal ganglion cells adapt by reducing their sensitivity during periods of high contrast. Contrast adaptation in the firing response depends on both presynaptic and intrinsic mechanisms. Here, we investigated intrinsic mechanisms for contrast adaptation in OFF Alpha ganglion cells in the in vitro guinea pig retina. Using either visual stimulation or current injection, we show that brief depolarization evoked spiking and suppressed firing during subsequent depolarization. The suppression could be explained by Na channel inactivation, as shown in salamander cells. However, brief hyperpolarization in the physiological range (5-10 mV) also suppressed firing during subsequent depolarization. This suppression was selectively sensitive to blockers of delayed-rectifier K channels (K(DR)). In somatic membrane patches, we observed tetraethylammonium-sensitive K(DR) currents that activated near -25 mV. Recovery from inactivation occurred at potentials hyperpolarized to V(rest). Brief periods of hyperpolarization apparently remove K(DR) inactivation and thereby increase the channel pool available to suppress excitability during subsequent depolarization.
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Affiliation(s)
- Michael Weick
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA
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Fohlmeister JF, Cohen ED, Newman EA. Mechanisms and distribution of ion channels in retinal ganglion cells: using temperature as an independent variable. J Neurophysiol 2010; 103:1357-74. [PMID: 20053849 DOI: 10.1152/jn.00123.2009] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Trains of action potentials of rat and cat retinal ganglion cells (RGCs) were recorded intracellularly across a temperature range of 7-37 degrees C. Phase plots of the experimental impulse trains were precision fit using multicompartment simulations of anatomically reconstructed rat and cat RGCs. Action potential excitation was simulated with a "Five-channel model" [Na, K(delayed rectifier), Ca, K(A), and K(Ca-activated) channels] and the nonspace-clamped condition of the whole cell recording was exploited to determine the channels' distribution on the dendrites, soma, and proximal axon. At each temperature, optimal phase-plot fits for RGCs occurred with the same unique channel distribution. The "waveform" of the electrotonic current was found to be temperature dependent, which reflected the shape changes in the experimental action potentials and confirmed the channel distributions. The distributions are cell-type specific and adequate for soma and dendritic excitation with a safety margin. The highest Na-channel density was found on an axonal segment some 50-130 microm distal to the soma, as determined from the temperature-dependent "initial segment-somadendritic (IS-SD) break." The voltage dependence of the gating rate constants remains invariant between 7 and 23 degrees C and between 30 and 37 degrees C, but undergoes a transition between 23 and 30 degrees C. Both gating-kinetic and ion-permeability Q10s remain virtually constant between 23 and 37 degrees C (kinetic Q10s = 1.9-1.95; permeability Q10s = 1.49-1.64). The Q10s systematically increase for T <23 degrees C (kinetic Q10 = 8 at T = 8 degrees C). The Na channels were consistently "sleepy" (non-Arrhenius) for T <8 degrees C, with a loss of spiking for T <7 degrees C.
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Affiliation(s)
- Jürgen F Fohlmeister
- Department of Integrative Biology Physiology, 6-125 Jackson Hall, 321 Church Street S.E., University of Minnesota, Minneapolis, MN 55455, USA.
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Fohlmeister JF. A nerve model of greatly increased energy-efficiency and encoding flexibility over the Hodgkin-Huxley model. Brain Res 2009; 1296:225-33. [PMID: 19596283 DOI: 10.1016/j.brainres.2009.06.101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 06/20/2009] [Accepted: 06/26/2009] [Indexed: 11/28/2022]
Abstract
A mammalian "RGC model" (retinal ganglion cells) is distinguished from the Hodgkin-Huxley model by the virtual absence of K-current during, and the virtual absence of Na-current after, the regenerative (rising) phase of the action potential. Both Na- and K-currents remain negligible throughout the interspike interval, whose control is therefore relinquished to stimulus currents. These properties yield a highly flexible and energy-efficient nerve impulse encoder. For the Hodgkin-Huxley model, in contrast, only 15% of the Na-ions enter the axon regeneratively during the action potential (squid giant axon); a wasteful 85% enter during the falling phase. Further, early activation of K-current causes the Na- and K-currents of the action potential to dominate over stimulus currents in controlling the sub-threshold membrane potential (interspike interval). This property makes the Hodgkin-Huxley model an intractable high frequency oscillator, which cannot be converted to flexible impulse encoding. The temperature difference between the squid giant axon (6.3 degrees C) and RGCs (37 degrees C) is bridged by a Q10 analysis, which suggests that an additional molecular gating mechanism of high Q10 - which is not present in the squid - is active in RGCs.
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Affiliation(s)
- Jürgen F Fohlmeister
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455, USA.
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