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Zhang Y, Tian J, Wang C, Wu T, Yi D, Wang L, Zhao D, Hou Y. N-Acetylcysteine Administration Improves the Redox and Functional Gene Expression Levels in Spleen, Mesenteric Lymph Node and Gastrocnemius Muscle in Piglets Infected with Porcine Epidemic Diarrhea Virus. Animals (Basel) 2023; 13:ani13020262. [PMID: 36670802 PMCID: PMC9854467 DOI: 10.3390/ani13020262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 01/15/2023] Open
Abstract
Our previous study reported that N-acetylcysteine (NAC) administration improved the function of intestinal absorption in piglets infected with porcine epidemic diarrhea virus (PEDV). However, the effects of NAC administration on the functions of other tissues and organs in PEDV-infected piglets have not been reported. In this study, the effects of NAC on the liver, spleen, lung, lymph node, and gastrocnemius muscle in PEDV-infected piglets were investigated. Thirty-two 7-day-old piglets with similar body weights were randomly divided into one of four groups: Control group, NAC group, PEDV group, and PEDV+NAC group (eight replicates per group and one pig per replicate). The trial had a 2 × 2 factorial design consisting of oral administration of 0 or 25 mg/kg body weight NAC and oral administration of 0 or 1.0 × 104.5 TCID50 PEDV. The trial lasted 12 days. All piglets were fed a milk replacer. On days 5-9 of the trial, piglets in the NAC and PEDV + NAC groups were orally administered NAC once a day; piglets in the control and PEDV groups were orally administered the same volume of saline. On day 9 of trial, piglets in the PEDV and PEDV+NAC groups were orally administrated 1.0 × 104.5 TCID50 PEDV, and the piglets in the control and NAC groups were orally administrated the same volume of saline. On day 12 of trial, samples, including of the liver, spleen, lung, lymph node, and gastrocnemius muscle, were collected. PEDV infection significantly increased catalase activity but significantly decreased the mRNA levels of Keap1, Nrf2, HMOX2, IFN-α, MX1, IL-10, TNF-α, S100A12, MMP3, MMP13, TGF-β, and GJA1 in the spleens of piglets. NAC administration ameliorated abnormal changes in measured variables in the spleens of PEDV-infected piglets. In addition, NAC administration also enhanced the antioxidant capacity of the mesenteric lymph nodes and gastrocnemius muscles in PEDV-infected piglets. Collectively, these novel results revealed that NAC administration improved the redox and functional gene expression levels in the spleen, mesenteric lymph nodes, and gastrocnemius muscle in PEDV-infected piglets.
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Schroeder M, Peter VG, Gränse L, Andréasson S, Rivolta C, Kjellström U. A novel phenotype associated with the R162W variant in the KCNJ13 gene. Ophthalmic Genet 2022; 43:500-507. [PMID: 35477418 DOI: 10.1080/13816810.2022.2068041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Pathogenic variants in KCNJ13 have been associated with both autosomal dominant Snowflake vitreoretinal degeneration (SVD) and autosomal recessive Leber congenital amaurosis. SVD is characterized by aberrant vitreoretinal interface leading to increased risk of retinal detachment, crystalline retinal snowflake deposits, optic disc abnormalities, early-onset cataract, and cornea guttae. Reduced dark adaptation and reduced scotopic rod b-waves have also been described. We report a novel phenotype associated with the R162W variant in KCNJ13. METHODS Four affected members of a Swedish family were included. Three of them were examined with best corrected visual acuity, Goldmann perimetry, full-field-and multifocal electroretinography, optical coherence tomography, fundus color photographs, fundus autofluorescence images, slit lamp inspection, and genetic testing. The fourth subject only managed genetic testing. RESULTS All subjects carry the pathogenic missense variant; c.484C>T (NM_002242.4), R162W, in KCNJ13. ERG measurements revealed reduced macular-as well as general retinal function. Two of the subjects had a history of retinal detachment and the two younger subjects demonstrated early onset cataract. They all had structural macular changes and slightly gliotic optic discs. CONCLUSION In this family, the R162W variant in KCNJ13, previously described in association with SVD, causes a somewhat novel phenotype including macular dystrophy and moderate reduction of general retinal function as the main features combined with disc abnormalities, retinal detachment, and presenile cataract that has been described before. In times of up-coming gene-based therapies, it is important to report new genotype-phenotype associations to improve the possibilities to identify future treatment candidates.
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Affiliation(s)
- Marion Schroeder
- Department of Ophthalmology and Clinical Sciences Lund, Lund University, Skane University Hospital, Lund, Sweden
| | - Virginie G Peter
- Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.,Department of Ophthalmology, University of Basel, Basel, Switzerland
| | - Lotta Gränse
- Department of Ophthalmology and Clinical Sciences Lund, Lund University, Skane University Hospital, Lund, Sweden
| | - Sten Andréasson
- Department of Ophthalmology and Clinical Sciences Lund, Lund University, Skane University Hospital, Lund, Sweden
| | - Carlo Rivolta
- Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.,Department of Ophthalmology, University of Basel, Basel, Switzerland
| | - Ulrika Kjellström
- Department of Ophthalmology and Clinical Sciences Lund, Lund University, Skane University Hospital, Lund, Sweden
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Akyuz E, Koklu B, Uner A, Angelopoulou E, Paudel YN. Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy. J Neurosci Res 2021; 100:413-443. [PMID: 34713909 DOI: 10.1002/jnr.24985] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/23/2021] [Accepted: 10/01/2021] [Indexed: 01/29/2023]
Abstract
Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.
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Affiliation(s)
- Enes Akyuz
- Faculty of International Medicine, Department of Biophysics, University of Health Sciences, Istanbul, Turkey
| | - Betul Koklu
- Faculty of Medicine, Namık Kemal University, Tekirdağ, Turkey
| | - Arda Uner
- Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Efthalia Angelopoulou
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Yam Nath Paudel
- Neuropharmacology Research Strength, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
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4
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Toms M, Burgoyne T, Tracey-White D, Richardson R, Dubis AM, Webster AR, Futter C, Moosajee M. Phagosomal and mitochondrial alterations in RPE may contribute to KCNJ13 retinopathy. Sci Rep 2019; 9:3793. [PMID: 30846767 PMCID: PMC6405871 DOI: 10.1038/s41598-019-40507-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 02/18/2019] [Indexed: 12/29/2022] Open
Abstract
Mutations in KCNJ13 are associated with two retinal disorders; Leber congenital amaurosis (LCA) and snowflake vitreoretinal degeneration (SVD). We examined the retina of kcnj13 mutant zebrafish (obelixtd15, c.502T > C p.[Phe168Leu]) to provide new insights into the pathophysiology underlying these conditions. Detailed phenotyping of obelixtd15 fish revealed a late onset retinal degeneration at 12 months. Electron microscopy of the obelixtd15 retinal pigment epithelium (RPE) uncovered reduced phagosome clearance and increased mitochondrial number and size prior any signs of retinal degeneration. Melanosome distribution was also affected in dark-adapted 12-month obelixtd15 fish. At 6 and 12 months, ATP levels were found to be reduced along with increased expression of glial fibrillary acidic protein and heat shock protein 60. Quantitative RT-PCR of polg2, fis1, opa1, sod1/2 and bcl2a from isolated retina showed expression changes consistent with altered mitochondrial activity and retinal stress. We propose that the retinal disease in this model is primarily a failure of phagosome physiology with a secondary mitochondrial dysfunction. Our findings suggest that alterations in the RPE and photoreceptor cellular organelles may contribute to KCNJ13-related retinal degeneration and provide a therapeutic target.
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Affiliation(s)
- Maria Toms
- UCL Institute of Ophthalmology, London, UK
| | | | | | | | - Adam M Dubis
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Andrew R Webster
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | | | - Mariya Moosajee
- UCL Institute of Ophthalmology, London, UK. .,Moorfields Eye Hospital NHS Foundation Trust, London, UK. .,Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK.
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5
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Shahi PK, Hermans D, Sinha D, Brar S, Moulton H, Stulo S, Borys KD, Capowski E, Pillers DAM, Gamm DM, Pattnaik BR. Gene Augmentation and Readthrough Rescue Channelopathy in an iPSC-RPE Model of Congenital Blindness. Am J Hum Genet 2019; 104:310-318. [PMID: 30686507 DOI: 10.1016/j.ajhg.2018.12.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 12/21/2018] [Indexed: 12/11/2022] Open
Abstract
Pathogenic variants of the KCNJ13 gene are known to cause Leber congenital amaurosis (LCA16), an inherited pediatric blindness. KCNJ13 encodes the Kir7.1 subunit that acts as a tetrameric, inwardly rectifying potassium ion channel in the retinal pigment epithelium (RPE) to maintain ionic homeostasis and allow photoreceptors to encode visual information. We sought to determine whether genetic approaches might be effective in treating blindness arising from pathogenic variants in KCNJ13. We derived human induced pluripotent stem cell (hiPSC)-RPE cells from an individual carrying a homozygous c.158G>A (p.Trp53∗) pathogenic variant of KCNJ13. We performed biochemical and electrophysiology assays to confirm Kir7.1 function. We tested both small-molecule readthrough drug and gene-therapy approaches for this "disease-in-a-dish" approach. We found that the LCA16 hiPSC-RPE cells had normal morphology but did not express a functional Kir7.1 channel and were unable to demonstrate normal physiology. After readthrough drug treatment, the LCA16 hiPSC cells were hyperpolarized by 30 mV, and the Kir7.1 current was restored. Similarly, we rescued Kir7.1 channel function after lentiviral gene delivery to the hiPSC-RPE cells. In both approaches, Kir7.1 was expressed normally, and there was restoration of membrane potential and the Kir7.1 current. Loss-of-function variants of Kir7.1 are one cause of LCA. Using either readthrough therapy or gene augmentation, we rescued Kir7.1 channel function in iPSC-RPE cells derived from an affected individual. This supports the development of precision-medicine approaches for the treatment of clinical LCA16.
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Affiliation(s)
- Pawan K Shahi
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA; McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Dalton Hermans
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Divya Sinha
- McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Simran Brar
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Hannah Moulton
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Sabrina Stulo
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Katarzyna D Borys
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Elizabeth Capowski
- McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - De-Ann M Pillers
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA; McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA; Medical Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - David M Gamm
- McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA; Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Bikash R Pattnaik
- Division of Neonatology, Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA; McPherson Eye Research, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA.
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6
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Pattnaik BR, Shahi PK, Marino MJ, Liu X, York N, Brar S, Chiang J, Pillers DAM, Traboulsi EI. A Novel KCNJ13 Nonsense Mutation and Loss of Kir7.1 Channel Function Causes Leber Congenital Amaurosis (LCA16). Hum Mutat 2015; 36:720-7. [PMID: 25921210 DOI: 10.1002/humu.22807] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 04/20/2015] [Indexed: 11/08/2022]
Abstract
Mutations in the KCNJ13 gene that encodes the inwardly rectifying potassium channel Kir7.1 cause snowflake vitreoretinal degeneration (SVD) and leber congenital amaurosis (LCA). Kir7.1 controls the microenvironment between the photoreceptors and the retinal pigment epithelium (RPE) and also contributes to the function of other organs such as uterus and brain. Heterologous expressions of the mutant channel have suggested a dominant-negative loss of Kir7.1 function in SVD, but parallel studies in LCA16 have been lacking. Herein, we report the identification of a novel nonsense mutation in the second exon of the KCNJ13 gene that leads to a premature stop codon in association with LCA16. We have determined that the mutation results in a severe truncation of the Kir7.1 C-terminus, alters protein localization, and disrupts potassium currents. Coexpression of the mutant and wild-type channel has no negative influence on the wild-type channel function, consistent with the normal clinical phenotype of carrier individuals. By suppressing Kir7.1 function in mice, we were able to reproduce the severe LCA electroretinogram phenotype. Thus, we have extended the observation that Kir7.1 mutations are associated with vision disorders to include novel insights into the molecular mechanism of disease pathobiology in LCA16.
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Affiliation(s)
- Bikash R Pattnaik
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin.,Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin.,McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
| | - Pawan K Shahi
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin
| | - Meghan J Marino
- Center for Genetic Eye Diseases and Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio
| | - Xinying Liu
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin
| | - Nathaniel York
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin
| | - Simran Brar
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin
| | - John Chiang
- Casey Molecular Diagnostic Laboratory, Oregon Health & Science University, Portland, Oregon
| | - De-Ann M Pillers
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin.,McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
| | - Elias I Traboulsi
- Center for Genetic Eye Diseases and Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio
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7
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Shukla R, Kannabiran C, Jalali S. Genetics of Leber congenital amaurosis: an update. EXPERT REVIEW OF OPHTHALMOLOGY 2014. [DOI: 10.1586/eop.12.14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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Pattnaik BR, Tokarz S, Asuma MP, Schroeder T, Sharma A, Mitchell JC, Edwards AO, Pillers DAM. Snowflake vitreoretinal degeneration (SVD) mutation R162W provides new insights into Kir7.1 ion channel structure and function. PLoS One 2013; 8:e71744. [PMID: 23977131 PMCID: PMC3747230 DOI: 10.1371/journal.pone.0071744] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 07/02/2013] [Indexed: 01/08/2023] Open
Abstract
Snowflake Vitreoretinal Degeneration (SVD) is associated with the R162W mutation of the Kir7.1 inwardly-rectifying potassium channel. Kir7.1 is found at the apical membrane of Retinal Pigment Epithelial (RPE) cells, adjacent to the photoreceptor neurons. The SVD phenotype ranges from RPE degeneration to an abnormal b-wave to a liquid vitreous. We sought to determine how this mutation alters the structure and function of the human Kir7.1 channel. In this study, we expressed a Kir7.1 construct with the R162W mutation in CHO cells to evaluate function of the ion channel. Compared to the wild-type protein, the mutant protein exhibited a non-functional Kir channel that resulted in depolarization of the resting membrane potential. Upon co-expression with wild-type Kir7.1, R162W mutant showed a reduction of IKir7.1 and positive shift in ‘0’ current potential. Homology modeling based on the structure of a bacterial Kir channel protein suggested that the effect of R162W mutation is a result of loss of hydrogen bonding by the regulatory lipid binding domain of the cytoplasmic structure.
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Affiliation(s)
- Bikash R. Pattnaik
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States of America
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
| | - Sara Tokarz
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Matti P. Asuma
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Tyler Schroeder
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Anil Sharma
- Department of Experimental Pathology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Julie C. Mitchell
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Albert O. Edwards
- Institute for Molecular Biology, University of Oregon, and Oregon Retina, Eugene, Oregon, United States of America
| | - De-Ann M. Pillers
- Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States of America
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, United States of America
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9
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Pattnaik BR, Asuma MP, Spott R, Pillers DAM. Genetic defects in the hotspot of inwardly rectifying K(+) (Kir) channels and their metabolic consequences: a review. Mol Genet Metab 2012; 105:64-72. [PMID: 22079268 PMCID: PMC3253982 DOI: 10.1016/j.ymgme.2011.10.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/11/2011] [Accepted: 10/12/2011] [Indexed: 02/07/2023]
Abstract
Inwardly rectifying potassium (Kir) channels are essential for maintaining normal potassium homeostasis and the resting membrane potential. As a consequence, mutations in Kir channels cause debilitating diseases ranging from cardiac failure to renal, ocular, pancreatic, and neurological abnormalities. Structurally, Kir channels consist of two trans-membrane domains, a pore-forming loop that contains the selectivity filter and two cytoplasmic polar tails. Within the cytoplasmic structure, clusters of amino acid sequences form regulatory domains that interact with cellular metabolites to control the opening and closing of the channel. In this review, we present an overview of Kir channel function and recent progress in the characterization of selected Kir channel mutations that lie in and near a C-terminal cytoplasmic 'hotspot' domain. The resultant molecular mechanisms by which the loss or gain of channel function leads to organ failure provide potential opportunities for targeted therapeutic interventions for this important group of channelopathies.
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Affiliation(s)
- Bikash R. Pattnaik
- Department of Pediatrics, University of Wisconsin, Madison
- Department of Ophthalmology & Visual Sciences, University of Wisconsin, Madison
- Department of Eye Research Institute, University of Wisconsin, Madison
| | - Matti P. Asuma
- Department of Pediatrics, University of Wisconsin, Madison
| | - Ryan Spott
- Department of Pediatrics, University of Wisconsin, Madison
| | - De-Ann M. Pillers
- Department of Pediatrics, University of Wisconsin, Madison
- Department of Eye Research Institute, University of Wisconsin, Madison
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10
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Expression of Kir7.1 and a novel Kir7.1 splice variant in native human retinal pigment epithelium. Exp Eye Res 2007; 86:81-91. [PMID: 18035352 DOI: 10.1016/j.exer.2007.09.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 09/24/2007] [Accepted: 09/25/2007] [Indexed: 11/20/2022]
Abstract
Previous studies on bovine retinal pigment epithelium (RPE) established that Kir7.1 channels compose this epithelium's large apical membrane K+ conductance. The purpose of this study was to determine whether Kir7.1 and potential Kir7.1 splice variants are expressed in native adult human RPE and, if so, to determine their function and how they are generated. RT-PCR analysis indicated that human RPE expresses full-length Kir7.1 and a novel Kir7.1 splice variant, designated Kir7.1S. Analysis of the human Kir7.1 gene (KCNJ13) organization revealed that it contains three exons, two introns, and a novel alternative 5' splice site in exon 2. In human RPE, the alternative usage of two competing 5' splice sites in exon 2 gives rise to transcripts encoding full-length Kir7.1 and Kir7.1S, which is predicted to encode a truncated protein. Real-time PCR indicated that Kir7.1 transcript is nearly as abundant as GAPDH mRNA in human RPE whereas Kir7.1S transcript expression is 4-fold lower. Western blot analysis showed that the splice variant is translated in Xenopus oocytes injected with Kir7.1S cRNA and revealed the expression of full-length Kir7.1 but not Kir7.1S in adult human RPE. Co-expression of Kir7.1 with Kir7.1S in Xenopus oocytes had no effect on either the kinetics or amplitude of Kir7.1 currents. This study confirms the expression of Kir7.1 in human RPE, identifies a Kir7.1 splice variant resulting in predicted changes in protein sequence, and indicates that there is no functional interaction between this splice variant and full-length Kir7.1.
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Derst C, Karschin C, Wischmeyer E, Hirsch JR, Preisig-Müller R, Rajan S, Engel H, Grzeschik K, Daut J, Karschin A. Genetic and functional linkage of Kir5.1 and Kir2.1 channel subunits. FEBS Lett 2001; 491:305-11. [PMID: 11240146 DOI: 10.1016/s0014-5793(01)02202-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have identified several cDNAs for the human Kir5.1 subunit of inwardly rectifying K(+) channels. Alternative splicing of exon 3 and the usage of two alternative polyadenylation sites contribute to cDNA diversity. The hKir5.1 gene KCNJ16 is assigned to chromosomal region 17q23.1-24.2, and is separated by only 34 kb from the hKir2.1 gene (KCNJ2). In the brain, Kir5.1 mRNA is restricted to the evolutionary older parts of the hindbrain, midbrain and diencephalon and overlaps with Kir2.1 in the superior/inferior colliculus and the pontine region. In the kidney Kir5.1 and Kir2.1 are colocalized in the proximal tubule. When expressed in Xenopus oocytes, Kir5.1 is efficiently targeted to the cell surface and forms electrically silent channels together with Kir2.1, thus negatively controlling Kir2.1 channel activity in native cells.
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Affiliation(s)
- C Derst
- Institute for Normal and Pathological Physiology, University of Marburg, Germany
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12
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Döring F, Karschin A. Genomic structure and promoter analysis of the rat kir7.1 potassium channel gene (Kcnj13). FEBS Lett 2000; 483:93-8. [PMID: 11042260 DOI: 10.1016/s0014-5793(00)02092-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the brain inwardly rectifying potassium channel Kir7.1 subunits are predominantly expressed in the choroid plexus and meninges. To investigate this tissue-specific expression pattern, we characterized the genomic organization and the 5' proximal promoter of the rat Kir7.1 gene (Kcnj13). Starting from the major transcriptional initiation site, three exons in Kcnj13 give rise to the dominant approximately 1.45 kb transcript in brain. Adjacent to the transcriptional start the minimal promoter which, uncommon for ion channels, contains a TATA- and CAAT-box is controlled by AP-1 factors and accounts for high gene expression levels. Luciferase reporter gene responses driven by the first 2.1 kb of the 5' flanking region were similarly high in epithelial FRTL-5 and neuronal N2A cells, suggesting that neuron-specific repressor elements are located remote from the non-selective minimal promoter.
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Affiliation(s)
- F Döring
- Molecular Neurobiology of Signal Transduction, Max-Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37070 Göttingen, Germany.
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13
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Nakamura N, Suzuki Y, Ikeda Y, Notoya M, Hirose S. Complex structure and regulation of expression of the rat gene for inward rectifier potassium channel Kir7.1. J Biol Chem 2000; 275:28276-84. [PMID: 10871613 DOI: 10.1074/jbc.m003734200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genomic organization of the rat inward rectifier K(+) channel Kir7.1 was determined in an attempt to clarify how multiple species of its mRNA are generated in a tissue-specific manner and how its expression is regulated. The rat Kir7.1 gene spans >40 kilobases (kb) and consists of eight exons; the first four exons encode the 5'-untranslated region that is unusually long ( approximately 3 kb). The coding region is located in exons 5 and 6. In the testis, exon 4 is processed as four exons (4a-4d), whereas it is recognized as a single exon in the small intestine. The three major species of rat Kir7.1 mRNA (1.4, 2.2, and 3.2 kb) were found to arise from alternative usage of the two promoters and polyadenylation signals and by alternative splicing of the 5'-noncoding exons. The splicing pattern of the 5'-noncoding exons is quite complex and highly tissue-specific, suggesting that complex mechanisms may operate to regulate the Kir7.1 expression. Deletion and mutational analysis of the promoter activity indicated that the rat Kir7.1 gene is regulated by cAMP through a CCAAT element. The cAMP induction was also demonstrated using the rat follicular cell line FRTL-5 endogenously expressing Kir7.1.
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Affiliation(s)
- N Nakamura
- Department of Biological Sciences, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
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