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Huffstetler CM, Cochran B, May CA, Maykut N, Silver CR, Cedeno C, Franck E, Cox A, Fadool DA. Single cannabidiol administration affects anxiety-, obsessive compulsive-, object memory-, and attention-like behaviors in mice in a sex and concentration dependent manner. Pharmacol Biochem Behav 2023; 222:173498. [PMID: 36455670 DOI: 10.1016/j.pbb.2022.173498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 11/30/2022]
Abstract
RATIONALE The behavioral effects of cannabidiol (CBD) are understudied, but are important, given its therapeutic potential and widespread use as a natural supplement. OBJECTIVE The objective of this study was to test whether a single injection of CBD affected anxiety-like or attention-like behavior, or memory in wildtype mice or mice with reported trait anxiety due to a targeted gene-deletion in a voltage-dependent potassium channel, Kv1.3. METHODS Wildtype C57BL/6 J and Kv1.3-/- mice of both sexes were reared to adulthood and then administered an intraperitoneal injection of 10 or 20 mg/kg CBD. Mice were behaviorally-phenotyped using the marble-burying test, the light-dark box (LDB), short (1 h) and long-term (24 h) object memory test, the elevated-plus maze (EPM), and the object-based attention task in order to assess obsessive compulsive-, anxiety-, and attention-like behaviors, and memory. RESULTS We discovered that acute CBD treatment reduced marble burying in male, but not female mice. CBD was effective in lessening anxiety-like behaviors determined by the LDB test in both male and female wildtype mice, whereby the effective dose required to observe the effect in females was less. In Kv1.3-/- mice, CBD increased anxiety-like behaviors in the LDB in both sexes at the higher concentration of CBD and it similarly increased anxiety-like behavior in females in the EPM at the lower concentration of CBD. Long-term object memory was reduced in male wildtype mice at the lower concentration of CBD. Finally, ADHD- or attention-like behaviors were not altered by CBD in wildtype mice, but in Kv1.3-/- mice, females were observed to have a loss in attention while males demonstrated improved attention. CONCLUSIONS We conclude that administration of a single dose of CBD has immediate effects on mouse behavior that is dose, sex, and anxiety-state dependent - and that these behavioral outcomes are important to examine in parallel human trials.
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Affiliation(s)
| | - Brigitte Cochran
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Camilla Ann May
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Nicholas Maykut
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Claudia Rose Silver
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Claudia Cedeno
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Ezabelle Franck
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA; Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA.
| | - Alexis Cox
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
| | - Debra Ann Fadool
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA; Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
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Ulusoy KG, Kaya E, Karabacak K, Seyrek M, Duvan İ, Yildirim V, Yildiz O. Taurine relaxes human radial artery through potassium channel opening action. Korean J Physiol Pharmacol 2017; 21:617-623. [PMID: 29200904 PMCID: PMC5709478 DOI: 10.4196/kjpp.2017.21.6.617] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Revised: 05/23/2017] [Accepted: 06/01/2017] [Indexed: 11/15/2022]
Abstract
The vascular actions and mechanisms of taurine were investigated in the isolated human radial artery (RA). RA rings were suspended in isolated organ baths and tension was recorded isometrically. First, a precontraction was achieved by adding potassium chloride (KCl, 45 mM) or serotonin (5-hydroxytryptamine, 5-HT, 30 µM) to organ baths. When the precontractions were stable, taurine (20, 40, 80 mM) was added cumulatively. Antagonistic effect of taurine on calcium chloride (10 µM to 10 mM)-induced contractions was investigated. Taurine-induced relaxations were also tested in the presence of the K+ channel inhibitors tetraethylammonium (1 mM), glibenclamide (10 µM) and 4-aminopyridine (1 mM). Taurine did not affect the basal tone but inhibited the contraction induced by 5-HT and KCl. Calcium chloride-induced contractions were significantly inhibited in the presence of taurine (20, 40, 80 mM) (p<0.05). The relaxation to taurine was inhibited by tetraethylammonium (p<0.05). However, glibenclamide and 4-aminopyridine did not affect taurine-induced relaxations. Present experiments show that taurine inhibits 5-HT and KCl-induced contractions in RA, and suggest that large conductance Ca2+-activated K+ channels may be involved in taurine-induced relaxation of RA.
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Affiliation(s)
- Kemal Gokhan Ulusoy
- Department of Medical Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Ankara 06018, Turkey
| | - Erkan Kaya
- Department of Cardiovascular Surgery, Gaziantep Faculty of Medicine, Gaziantep University, Gaziantep 27310, Turkey
| | - Kubilay Karabacak
- Department of Cardiovascular Surgery, Gulhane Faculty of Medicine, University of Health Sciences, Ankara 06018, Turkey
| | - Melik Seyrek
- Department of Medical Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Ankara 06018, Turkey
| | - İbrahim Duvan
- Department of Cardiovascular Surgery, Guven Hospital, Ankara 06540, Turkey
| | - Vedat Yildirim
- Department of Anesthesiology, Gulhane Faculty of Medicine, University of Health Sciences, Ankara 06018, Turkey
| | - Oguzhan Yildiz
- Department of Medical Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Ankara 06018, Turkey
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Jang YH, Kim JH, Lee YC. Mitochondrial ATP-Sensitive Potassium Channels Play a Role in Reducing Both Myocardial Infarction and Reperfusion Arrhythmia in Remote Ischemic Preconditioned Hearts. Anesth Pain Med 2017; 7:e42505. [PMID: 28920042 PMCID: PMC5554422 DOI: 10.5812/aapm.42505] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 11/10/2016] [Accepted: 11/25/2016] [Indexed: 01/27/2023] Open
Abstract
Background Mitochondrial ATP-sensitive potassium (mKATP) channels play a role in reperfusion arrhythmias (RAs) in ischemia-reperfusion (I/R) injury. Evidence suggests that remote ischemic preconditioning (RIPC) reduces RAs, however not much is known on the mechanistic role of mKATP in RIPC. We evaluated whether mKATP channels are associated with reducing arrhythmia and infarct size in RIPC. Methods Isolated rat hearts received 30 minutes of regional ischemia followed by 2 hours of reperfusion through the Langendorff perfusion system. RIPC was induced by 3 cycles of 5 minutes occlusion and 5 minutes release of the bilateral femoral artery. The animals were randomly divided into 4 groups as follows: 1) CON, I/R injury but not RIPC, 2) RIPC, 3) HD+RIPC, pretreatment of the selective mKATP channel blocker, 5-hydroxydecanoate (5-HD), in RIPC, and 4) HD, pretreatment of 5-HD in CON. Cardiodynamics and infarct size were determined. The severity of arrhythmia was quantitated via the Curtis and Walker scoring system as well as the Lepran scoring system. Results RIPC significantly reduced the infarct size over AR (25.7 ± 2.6%) compared to CON (37.0 ± 2.6%, P < 0.05). The selective mKATP channel blocker 5-HD significantly inhibited the infarct-reducing effect of RIPC (39.3 ± 3.0%, P < 0.05 vs. RIPC). Additionally, RIPC significantly reduced the arrhythmia score compared to CON (14.6 ± 1.9 to 8.7 ± 0.4, P = 0.023, by Curtis and Walker’s system, 16.1 ± 2.1 to 9.1 ± 0.5, P = 0.006, by Lepran’s system). The anti-arrhythmic effect of RIPC was blocked by 5-HD (15.5 ± 1.6 and 16.0 ± 1.2, by Curtis and Walker’s and Lepran’s system, respectively). Conclusions The selective mKATP channel blocker, 5-HD, inhibited the infarct-limitation and anti-arrhythmic effect of RIPC. The mKATP channels play a role in the reduction of both infarct size and RAs in RIPC.
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Affiliation(s)
- Young-Ho Jang
- Institute of Cardiovascular Research, Pusan National University, Yangsan Hospital, Yangsan-si, Gyeongsangnam-do, Korea
| | - June-Hong Kim
- Institute of Cardiovascular Research, Pusan National University, Yangsan Hospital, Yangsan-si, Gyeongsangnam-do, Korea
| | - Yong-Cheol Lee
- Department of Anesthesiology and Pain Medicine, Keimyung University, School of Medicine, Daegu, Korea
- Corresponding author: Yong-Cheol Lee, Ph.D., Department of Anesthesiology and Pain Medicine, Keimyung University, School of Medicine, 56 Dalseong-ro, Jung-gu, Daegu, 700-712, Korea. Tel: +82-532507193, Fax: +82-532507240, E-mail:
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Kuzmenkov AI, Vassilevski AA, Kudryashova KS, Nekrasova OV, Peigneur S, Tytgat J, Feofanov AV, Kirpichnikov MP, Grishin EV. Variability of Potassium Channel Blockers in Mesobuthus eupeus Scorpion Venom with Focus on Kv1.1: AN INTEGRATED TRANSCRIPTOMIC AND PROTEOMIC STUDY. J Biol Chem 2015; 290:12195-209. [PMID: 25792741 DOI: 10.1074/jbc.m115.637611] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Indexed: 12/21/2022] Open
Abstract
The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus, and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here, we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands, and we compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis, we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β and inhibitor cystine knot types of fold. M. eupeus venom was then separated to individual components by multistage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore binding activity during venom separation. As a result, eight high affinity Kv1.1 channel blockers were identified, including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1-780 nm) by the two-electrode voltage clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs.
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Affiliation(s)
- Alexey I Kuzmenkov
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia
| | - Alexander A Vassilevski
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia,
| | - Kseniya S Kudryashova
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia, the Biological Faculty, Lomonosov Moscow State University, Moscow 119992, Russia, and
| | - Oksana V Nekrasova
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia
| | - Steve Peigneur
- the Laboratory of Toxicology and Pharmacology, University of Leuven, Leuven 3000, Belgium
| | - Jan Tytgat
- the Laboratory of Toxicology and Pharmacology, University of Leuven, Leuven 3000, Belgium
| | - Alexey V Feofanov
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia, the Biological Faculty, Lomonosov Moscow State University, Moscow 119992, Russia, and
| | - Mikhail P Kirpichnikov
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia, the Biological Faculty, Lomonosov Moscow State University, Moscow 119992, Russia, and
| | - Eugene V Grishin
- From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia
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Devaraneni PK, Martin GM, Olson EM, Zhou Q, Shyng SL. Structurally distinct ligands rescue biogenesis defects of the KATP channel complex via a converging mechanism. J Biol Chem 2015; 290:7980-91. [PMID: 25637631 DOI: 10.1074/jbc.m114.634576] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Small molecules that correct protein misfolding and misprocessing defects offer a potential therapy for numerous human diseases. However, mechanisms underlying pharmacological correction of such defects, especially in heteromeric complexes with structurally diverse constituent proteins, are not well understood. Here we investigate how two chemically distinct compounds, glibenclamide and carbamazepine, correct biogenesis defects in ATP-sensitive potassium (KATP) channels composed of sulfonylurea receptor 1 (SUR1) and Kir6.2. We present evidence that despite structural differences, carbamazepine and glibenclamide compete for binding to KATP channels, and both drugs share a binding pocket in SUR1 to exert their effects. Moreover, both compounds engage Kir6.2, in particular the distal N terminus of Kir6.2, which is involved in normal channel biogenesis, for their chaperoning effects on SUR1 mutants. Conversely, both drugs can correct channel biogenesis defects caused by Kir6.2 mutations in a SUR1-dependent manner. Using an unnatural, photocross-linkable amino acid, azidophenylalanine, genetically encoded in Kir6.2, we demonstrate in living cells that both drugs promote interactions between the distal N terminus of Kir6.2 and SUR1. These findings reveal a converging pharmacological chaperoning mechanism wherein glibenclamide and carbamazepine stabilize the heteromeric subunit interface critical for channel biogenesis to overcome defective biogenesis caused by mutations in individual subunits.
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Affiliation(s)
- Prasanna K Devaraneni
- From the Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - Gregory M Martin
- From the Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - Erik M Olson
- From the Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - Qing Zhou
- From the Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239
| | - Show-Ling Shyng
- From the Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239
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Yi F, Ling TY, Lu T, Wang XL, Li J, Claycomb WC, Shen WK, Lee HC. Down-regulation of the small conductance calcium-activated potassium channels in diabetic mouse atria. J Biol Chem 2015; 290:7016-26. [PMID: 25605734 DOI: 10.1074/jbc.m114.607952] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The small conductance Ca(2+)-activated K(+) (SK) channels have recently been found to be expressed in the heart, and genome-wide association studies have shown that they are implicated in atrial fibrillation. Diabetes mellitus is an independent risk factor of atrial fibrillation, but the ionic mechanism underlying this relationship remains unclear. We hypothesized that SK channel function is abnormal in diabetes mellitus, leading to altered cardiac electrophysiology. We found that in streptozotocin-induced diabetic mice, the expression of SK2 and SK3 isoforms was down-regulated by 85 and 92%, respectively, whereas that of SK1 was not changed. SK currents from isolated diabetic mouse atrial myocytes were significantly reduced compared with controls. The resting potentials of isolated atrial preparations were similar between control and diabetic mice, but action potential durations were significantly prolonged in the diabetic atria. Exposure to apamin significantly prolonged action potential durations in control but not in diabetic atria. Production of reactive oxygen species was significantly increased in diabetic atria and in high glucose-cultured HL-1 cells, whereas exposure of HL-1 cells in normal glucose culture to H2O2 reduced the expression of SK2 and SK3. Tyrosine nitration in SK2 and SK3 was significantly increased by high glucose culture, leading to accelerated channel turnover. Treatment with Tiron prevented these changes. Our results suggest that increased oxidative stress in diabetes results in SK channel-associated electrical remodeling in diabetic atria and may promote arrhythmogenesis.
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Affiliation(s)
- Fu Yi
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905, Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Tian-You Ling
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905, Department of Cardiology, Ruijin Hospital, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China
| | - Tong Lu
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiao-Li Wang
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905
| | - Jingchao Li
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905, Department of Emergency Medicine, Henan Provincial People's Hospital, Affiliated Hospital of Zhengzhou University, Zhengzhou 450003, Henan, China
| | - William C Claycomb
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, and
| | - Win-Kuang Shen
- Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Phoenix, Arizona 85255
| | - Hon-Chi Lee
- From the Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota 55905,
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8
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Lu L, Sirish P, Zhang Z, Woltz RL, Li N, Timofeyev V, Knowlton AA, Zhang XD, Yamoah EN, Chiamvimonvat N. Regulation of gene transcription by voltage-gated L-type calcium channel, Cav1.3. J Biol Chem 2014; 290:4663-4676. [PMID: 25538241 DOI: 10.1074/jbc.m114.586883] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cav1.3 L-type Ca(2+) channel is known to be highly expressed in neurons and neuroendocrine cells. However, we have previously demonstrated that the Cav1.3 channel is also expressed in atria and pacemaking cells in the heart. The significance of the tissue-specific expression of the channel is underpinned by our previous demonstration of atrial fibrillation in a Cav1.3 null mutant mouse model. Indeed, a recent study has confirmed the critical roles of Cav1.3 in the human heart (Baig, S. M., Koschak, A., Lieb, A., Gebhart, M., Dafinger, C., Nürnberg, G., Ali, A., Ahmad, I., Sinnegger-Brauns, M. J., Brandt, N., Engel, J., Mangoni, M. E., Farooq, M., Khan, H. U., Nürnberg, P., Striessnig, J., and Bolz, H. J. (2011) Nat. Neurosci. 14, 77-84). These studies suggest that detailed knowledge of Cav1.3 may have broad therapeutic ramifications in the treatment of cardiac arrhythmias. Here, we tested the hypothesis that there is a functional cross-talk between the Cav1.3 channel and a small conductance Ca(2+)-activated K(+) channel (SK2), which we have documented to be highly expressed in human and mouse atrial myocytes. Specifically, we tested the hypothesis that the C terminus of Cav1.3 may translocate to the nucleus where it functions as a transcriptional factor. Here, we reported for the first time that the C terminus of Cav1.3 translocates to the nucleus where it functions as a transcriptional regulator to modulate the function of Ca(2+)-activated K(+) channels in atrial myocytes. Nuclear translocation of the C-terminal domain of Cav1.3 is directly regulated by intracellular Ca(2+). Utilizing a Cav1.3 null mutant mouse model, we demonstrate that ablation of Cav1.3 results in a decrease in the protein expression of myosin light chain 2, which interacts and increases the membrane localization of SK2 channels.
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Affiliation(s)
- Ling Lu
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the College of Life Sciences, Nanjing Normal University, Nanjing 210046, China.
| | - Padmini Sirish
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Zheng Zhang
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ryan L Woltz
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ning Li
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Valeriy Timofeyev
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Anne A Knowlton
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the Department of Veterans Affairs, Northern California Health Care System, Mather, California 95655
| | - Xiao-Dong Zhang
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616
| | - Ebenezer N Yamoah
- the Department of Physiology, School of Medicine, University of Nevada, Reno, Nevada 89557, and.
| | - Nipavan Chiamvimonvat
- From the Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, California 95616,; the Department of Veterans Affairs, Northern California Health Care System, Mather, California 95655,.
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Abstract
Voltage-gated K(+) channels (Kv) are responsible for repolarizing excitable cells and can be heavily glycosylated. Cardiac Kv activity is indispensable where even minimal reductions in function can extend action potential duration, prolong QT intervals, and ultimately contribute to life-threatening arrhythmias. Diseases such as congenital disorders of glycosylation often cause significant cardiac phenotypes that can include arrhythmias. Here we investigated the impact of reduced sialylation on ventricular repolarization through gene deletion of the sialyltransferase ST3Gal4. ST3Gal4-deficient mice (ST3Gal4(-/-)) had prolonged QT intervals with a concomitant increase in ventricular action potential duration. Ventricular apex myocytes isolated from ST3Gal4(-/-) mice demonstrated depolarizing shifts in activation gating of the transient outward (Ito) and delayed rectifier (IKslow) components of K(+) current with no change in maximum current densities. Consistently, similar protein expression levels of the three Kv isoforms responsible for Ito and IKslow were measured for ST3Gal4(-/-) versus controls. However, novel non-enzymatic sialic acid labeling indicated a reduction in sialylation of ST3Gal4(-/-) ventricular Kv4.2 and Kv1.5, which contribute to Ito and IKslow, respectively. Thus, we describe here a novel form of regulating cardiac function through the activities of a specific glycogene product. Namely, reduced ST3Gal4 activity leads to a loss of isoform-specific Kv sialylation and function, thereby limiting Kv activity during the action potential and decreasing repolarization rate, which likely contributes to prolonged ventricular repolarization. These studies elucidate a novel role for individual glycogene products in contributing to a complex network of cardiac regulation under normal and pathologic conditions.
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Affiliation(s)
- Andrew R Ednie
- From the Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida 33612
| | - Eric S Bennett
- From the Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida 33612
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10
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Tian J, Tep C, Benedick A, Saidi N, Ryu JC, Kim ML, Sadasivan S, Oberdick J, Smeyne R, Zhu MX, Yoon SO. p75 regulates Purkinje cell firing by modulating SK channel activity through Rac1. J Biol Chem 2014; 289:31458-72. [PMID: 25253694 PMCID: PMC4223344 DOI: 10.1074/jbc.m114.589937] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 09/11/2014] [Indexed: 12/22/2022] Open
Abstract
p75 is expressed among Purkinje cells in the adult cerebellum, but its function has remained obscure. Here we report that p75 is involved in maintaining the frequency and regularity of spontaneous firing of Purkinje cells. The overall spontaneous firing activity of Purkinje cells was increased in p75(-/-) mice during the phasic firing period due to a longer firing period and accompanying reduction in silence period than in the wild type. We attribute these effects to a reduction in small conductance Ca(2+)-activated potassium (SK) channel activity in Purkinje cells from p75(-/-) mice compared with the wild type littermates. The mechanism by which p75 regulates SK channel activity appears to involve its ability to activate Rac1. In organotypic cultures of cerebellar slices, brain-derived neurotrophic factor increased RacGTP levels by activating p75 but not TrkB. These results correlate with a reduction in RacGTP levels in synaptosome fractions from the p75(-/-) cerebellum, but not in that from the cortex of the same animals, compared with wild type littermates. More importantly, we demonstrate that Rac1 modulates SK channel activity and firing patterns of Purkinje cells. Along with the finding that spine density was reduced in p75(-/-) cerebellum, these data suggest that p75 plays a role in maintaining normalcy of Purkinje cell firing in the cerebellum in part by activating Rac1 in synaptic compartments and modulating SK channels.
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Affiliation(s)
- JinBin Tian
- the Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, the Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Chhavy Tep
- From the Department of Molecular and Cellular Biochemistry, the Biochemistry Program, and
| | - Alex Benedick
- From the Department of Molecular and Cellular Biochemistry
| | - Nabila Saidi
- From the Department of Molecular and Cellular Biochemistry
| | - Jae Cheon Ryu
- From the Department of Molecular and Cellular Biochemistry
| | - Mi Lyang Kim
- From the Department of Molecular and Cellular Biochemistry
| | - Shankar Sadasivan
- the Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, and
| | | | - Richard Smeyne
- the Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, and
| | - Michael X Zhu
- the Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, the Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Sung Ok Yoon
- From the Department of Molecular and Cellular Biochemistry,
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11
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Chávez JC, Ferreira JJ, Butler A, De La Vega Beltrán JL, Treviño CL, Darszon A, Salkoff L, Santi CM. SLO3 K+ channels control calcium entry through CATSPER channels in sperm. J Biol Chem 2014; 289:32266-32275. [PMID: 25271166 DOI: 10.1074/jbc.m114.607556] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Here we show how a sperm-specific potassium channel (SLO3) controls Ca(2+) entry into sperm through a sperm-specific Ca(2+) channel, CATSPER, in a totally unanticipated manner. The genetic deletion of either of those channels confers male infertility in mice. During sperm capacitation SLO3 hyperpolarizes the sperm, whereas CATSPER allows Ca(2+) entry. These two channels may be functionally connected, but it had not been demonstrated that SLO3-dependent hyperpolarization is required for Ca(2+) entry through CATSPER channels, nor has a functional mechanism linking the two channels been shown. In this study we show that Ca(2+) entry through CATSPER channels is deficient in Slo3 mutant sperm lacking hyperpolarization; we also present evidence supporting the hypothesis that SLO3 channels activate CATSPER channels indirectly by promoting a rise in intracellular pH through a voltage-dependent mechanism. This mechanism may work through a Na(+)/H(+) exchanger (sNHE) and/or a bicarbonate transporter, which utilizes the inward driving force of the Na(+) gradient, rendering it intrinsically voltage-dependent. In addition, the sperm-specific Na(+)/H(+) exchanger (sNHE) possess a putative voltage sensor that might be activated by membrane hyperpolarization, thus increasing the voltage sensitivity of internal alkalization.
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Affiliation(s)
- Julio César Chávez
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 and; Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), 62210 Cuernavaca, México
| | - Juan José Ferreira
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Alice Butler
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | | | - Claudia L Treviño
- Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), 62210 Cuernavaca, México
| | - Alberto Darszon
- Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), 62210 Cuernavaca, México
| | - Lawrence Salkoff
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Celia M Santi
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 and
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12
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Gonzalez WG, Pham K, Miksovska J. Modulation of the voltage-gated potassium channel (Kv4.3) and the auxiliary protein (KChIP3) interactions by the current activator NS5806. J Biol Chem 2014; 289:32201-32213. [PMID: 25228688 DOI: 10.1074/jbc.m114.577528] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
KChIP3 (potassium channel interacting protein 3) is a calcium-binding protein that binds at the N terminus of the Kv4 voltage-gated potassium channel through interactions at two contact sites and has been shown to regulate potassium current gating kinetics as well as channel trafficking in cardiac and neuronal cells. Using fluorescence spectroscopy, isothermal calorimetry, and docking simulations we show that the novel potassium current activator, NS5806, binds at a hydrophobic site on the C terminus of KChIP3 in a calcium-dependent manner, with an equilibrium dissociation constant of 2-5 μM in the calcium-bound form. We further determined that the association between KChIP3 and the hydrophobic N terminus of Kv4.3 is calcium-dependent, with an equilibrium dissociation constant in the apo-state of 70 ± 3 μM and 2.7 ± 0.1 μM in the calcium-bound form. NS5806 increases the affinity between KChIP3 and the N terminus of Kv4.3 (Kd = 1.9 ± 0.1 μM) in the presence and absence of calcium. Mutation of Tyr-174 or Phe-218 on KChIP3 abolished the enhancement of Kv4.3 site 1 binding in the apo-state, highlighting the role of these residues in drug and K4.3 binding. Kinetic studies show that NS5806 decreases the rate of dissociation between KChIP3 and the N terminus of KV4.3. Overall, these studies support the idea that NS5806 directly interacts with KChIP3 and modulates the interactions between this calcium-binding protein and the T1 domain of the Kv4.3 channels through reorientation of helix 10 on KChIP3.
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Affiliation(s)
- Walter G Gonzalez
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Khoa Pham
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Jaroslava Miksovska
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199.
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13
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Czirják G, Enyedi P. The LQLP calcineurin docking site is a major determinant of the calcium-dependent activation of human TRESK background K+ channel. J Biol Chem 2014; 289:29506-18. [PMID: 25202008 DOI: 10.1074/jbc.m114.577684] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-dependent activation of human TRESK (TWIK-related spinal cord K(+) channel, K2P18.1) depends on direct targeting of calcineurin to the PQIIIS motif. In the present study we demonstrate that TRESK also contains another functionally relevant docking site for the phosphatase, the LQLP amino acid sequence. Combined mutations of the PQIIIS and LQLP motifs were required to eliminate the calcium-dependent regulation of the channel. In contrast to the alanine substitutions of PQIIIS, the mutation of LQLP to AQAP alone did not significantly change the amplitude of TRESK activation evoked by the substantial elevation of cytoplasmic calcium concentration. However, the AQAP mutation slowed down the response to high calcium. In addition, modest elevation of [Ca(2+)], which effectively regulated the wild type channel, failed to activate TRESK-AQAP. This indicates that the AQAP mutation diminished the sensitivity of TRESK to calcium. Even if PQIIIS was replaced by the PVIVIT sequence of high calcineurin binding affinity, the effect of the AQAP mutation was clearly detected in this TRESK-PVIVIT context. Substitution of the LQLP region with the corresponding fragment of NFAT transcription factor, perfectly matching the previously described LXVP calcineurin-binding consensus sequence, increased the calcium-sensitivity of TRESK-PVIVIT. Thus the enhancement of the affinity of TRESK for calcineurin by the incorporation of PVIVIT could not compensate for or prevent the effects of LQLP sequence modifications, suggesting that the two calcineurin-binding regions play distinct roles in the regulation. Our results indicate that the LQLP site is a fundamental determinant of the calcium-sensitivity of human TRESK.
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Affiliation(s)
- Gábor Czirják
- From the Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Péter Enyedi
- From the Department of Physiology, Semmelweis University, Budapest, Hungary
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14
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Velázquez-Marrero C, Seale GE, Treistman SN, Martin GE. Large conductance voltage- and Ca2+-gated potassium (BK) channel β4 subunit influences sensitivity and tolerance to alcohol by altering its response to kinases. J Biol Chem 2014; 289:29261-72. [PMID: 25190810 DOI: 10.1074/jbc.m114.604306] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tolerance is a well described component of alcohol abuse and addiction. The large conductance voltage- and Ca(2+)-gated potassium channel (BK) has been very useful for studying molecular tolerance. The influence of association with the β4 subunit can be observed at the level of individual channels, action potentials in brain slices, and finally, drinking behavior in the mouse. Previously, we showed that 50 mm alcohol increases both α and αβ4 BK channel open probability, but only α BK develops acute tolerance to this effect. Currently, we explore the possibility that the influence of the β4 subunit on tolerance may result from a striking effect of β4 on kinase modulation of the BK channel. We examine the influence of the β4 subunit on PKA, CaMKII, and phosphatase modulation of channel activity, and on molecular tolerance to alcohol. We record from human BK channels heterologously expressed in HEK 293 cells composed of its core subunit, α alone (Insertless), or co-expressed with the β4 BK auxiliary subunit, as well as, acutely dissociated nucleus accumbens neurons using the cell-attached patch clamp configuration. Our results indicate that BK channels are strongly modulated by activation of specific kinases (PKA and CaMKII) and phosphatases. The presence of the β4 subunit greatly influences this modulation, allowing a variety of outcomes for BK channel activity in response to acute alcohol.
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Affiliation(s)
- Cristina Velázquez-Marrero
- the Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico 00901
| | - Garrett E Seale
- the Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico 00901
| | - Steven N Treistman
- the Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico 00901
| | - Gilles E Martin
- From the Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01604 and
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15
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Abstract
Dipeptidyl peptidase-like protein 6 (DPP6) is an auxiliary subunit of the Kv4 family of voltage-gated K(+) channels known to enhance channel surface expression and potently accelerate their kinetics. DPP6 is a single transmembrane protein, which is structurally remarkable for its large extracellular domain. Included in this domain is a cysteine-rich motif, the function of which is unknown. Here we show that this cysteine-rich domain of DPP6 is required for its export from the ER and expression on the cell surface. Disulfide bridges formed at C349/C356 and C465/C468 of the cysteine-rich domain are necessary for the enhancement of Kv4.2 channel surface expression but not its interaction with Kv4.2 subunits. The short intracellular N-terminal and transmembrane domains of DPP6 associates with and accelerates the recovery from inactivation of Kv4.2, but the entire extracellular domain is necessary to enhance Kv4.2 surface expression and stabilization. Our findings show that the cysteine-rich domain of DPP6 plays an important role in protein folding of DPP6 that is required for transport of DPP6/Kv4.2 complexes out of the ER.
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Affiliation(s)
- Lin Lin
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
| | - Laura K Long
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Michael M Hatch
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Dax A Hoffman
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
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16
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Blin S, Chatelain FC, Feliciangeli S, Kang D, Lesage F, Bichet D. Tandem pore domain halothane-inhibited K+ channel subunits THIK1 and THIK2 assemble and form active channels. J Biol Chem 2014; 289:28202-12. [PMID: 25148687 DOI: 10.1074/jbc.m114.600437] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Despite a high level of sequence homology, tandem pore domain halothane-inhibited K(+) channel 1 (THIK1) produces background K(+) currents, whereas THIK2 is silent. This lack of activity is due to a unique combination of intracellular retention and weak basal activity in the plasma membrane. Here, we designed THIK subunits containing dominant negative mutations (THIK1(DN) and THIK2(DN)). THIK2(DN) mutant inhibits THIK1 currents, whereas THIK1(DN) inhibits an activated form of THIK2 (THIK2-A155P-I158D). In situ proximity ligation assays and Förster/fluorescence resonance energy transfer (FRET) experiments support a physical association between THIK1 and THIK2. Next, we expressed covalent tandems of THIK proteins to obtain expression of pure heterodimers. Td-THIK1-THIK2 (where Td indicates tandem) produces K(+) currents of amplitude similar to Td-THIK1-THIK1 but with a noticeable difference in the current kinetics. Unlike Td-THIK2-THIK2 that is mainly detected in the endoplasmic reticulum, Td-THIK1-THIK2 distributes at the plasma membrane, indicating that THIK1 can mask the endoplasmic reticulum retention/retrieval motif of THIK2. Kinetics and unitary conductance of Td-THIK1-THIK2 are intermediate between THIK1 and THIK2. Altogether, these results show that THIK1 and THIK2 form active heteromeric channels, further expanding the known repertoire of K(+) channels.
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Affiliation(s)
- Sandy Blin
- From LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia Antipolis, 660 Route des Lucioles, 06560 Valbonne, France and
| | - Franck C Chatelain
- From LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia Antipolis, 660 Route des Lucioles, 06560 Valbonne, France and
| | - Sylvain Feliciangeli
- From LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia Antipolis, 660 Route des Lucioles, 06560 Valbonne, France and
| | - Dawon Kang
- the Department of Physiology and Institute of Health Sciences, Gyeongsang National University, School of Medicine, Jinju 660-751, South Korea
| | - Florian Lesage
- From LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia Antipolis, 660 Route des Lucioles, 06560 Valbonne, France and
| | - Delphine Bichet
- From LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia Antipolis, 660 Route des Lucioles, 06560 Valbonne, France and
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17
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Streit AK, Matschke LA, Dolga AM, Rinné S, Decher N. RNA editing in the central cavity as a mechanism to regulate surface expression of the voltage-gated potassium channel Kv1.1. J Biol Chem 2014; 289:26762-26771. [PMID: 25100718 DOI: 10.1074/jbc.m113.545731] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Voltage-gated potassium (Kv) 1.1 channels undergo a specific enzymatic RNA deamination, generating a channel with a single amino acid exchange located in the inner pore cavity (Kv1.1(I400V)). We studied I400V-edited Kv1.1 channels in more detail and found that Kv1.1(I400V) gave rise to much smaller whole-cell currents than Kv1.1. To elucidate the mechanism behind this current reduction, we conducted electrophysiological recordings on single-channel level and did not find any differences. Next we examined channel surface expression in Xenopus oocytes and HeLa cells using a chemiluminescence assay and found the edited channels to be less readily expressed at the surface membrane. This reduction in surface expression was verified by fluorescence imaging experiments. Western blot analysis for comparison of protein abundances and glycosylation patterns did not show any difference between Kv1.1 and Kv1.1(I400V), further indicating that changed trafficking of Kv1.1(I400V) is causing the current reduction. Block of endocytosis by dynasore or AP180C did not abolish the differences in current amplitudes between Kv1.1 and Kv1.1(I400V), suggesting that backward trafficking is not affected. Therefore, our data suggest that I400V RNA editing of Kv1.1 leads to a reduced current size by a decreased forward trafficking of the channel to the surface membrane. This effect is specific for Kv1.1 because coexpression of Kv1.4 channel subunits with Kv1.1(I400V) abolishes these trafficking effects. Taken together, we identified RNA editing as a novel mechanism to regulate homomeric Kv1.1 channel trafficking. Fine-tuning of Kv1.1 surface expression by RNA editing might contribute to the complexity of neuronal Kv channel regulation.
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Affiliation(s)
- Anne K Streit
- Institut für Physiologie und Pathophysiologie, Fachbereich Medizin, and Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Lina A Matschke
- Institut für Physiologie und Pathophysiologie, Fachbereich Medizin, and Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Amalia M Dolga
- Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Susanne Rinné
- Institut für Physiologie und Pathophysiologie, Fachbereich Medizin, and Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Niels Decher
- Institut für Physiologie und Pathophysiologie, Fachbereich Medizin, and Philipps-Universität Marburg, 35037 Marburg, Germany.
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18
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Ng CA, Phan K, Hill AP, Vandenberg JI, Perry MD. Multiple interactions between cytoplasmic domains regulate slow deactivation of Kv11.1 channels. J Biol Chem 2014; 289:25822-32. [PMID: 25074935 DOI: 10.1074/jbc.m114.558379] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intracellular domains of many ion channels are important for fine-tuning their gating kinetics. In Kv11.1 channels, the slow kinetics of channel deactivation, which are critical for their function in the heart, are largely regulated by the N-terminal N-Cap and Per-Arnt-Sim (PAS) domains, as well as the C-terminal cyclic nucleotide-binding homology (cNBH) domain. Here, we use mutant cycle analysis to probe for functional interactions between the N-Cap/PAS domains and the cNBH domain. We identified a specific and stable charge-charge interaction between Arg(56) of the PAS domain and Asp(803) of the cNBH domain, as well an additional interaction between the cNBH domain and the N-Cap, both of which are critical for maintaining slow deactivation kinetics. Furthermore, we found that positively charged arginine residues within the disordered region of the N-Cap interact with negatively charged residues of the C-linker domain. Although this interaction is likely more transient than the PAS-cNBD interaction, it is strong enough to stabilize the open conformation of the channel and thus slow deactivation. These findings provide novel insights into the slow deactivation mechanism of Kv11.1 channels.
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Affiliation(s)
- Chai Ann Ng
- From the Victor Chang Cardiac Research Institute and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Kevin Phan
- From the Victor Chang Cardiac Research Institute and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Adam P Hill
- From the Victor Chang Cardiac Research Institute and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Jamie I Vandenberg
- From the Victor Chang Cardiac Research Institute and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Matthew D Perry
- From the Victor Chang Cardiac Research Institute and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
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19
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Zhang Z, Li M, Lu R, Alioua A, Stefani E, Toro L. The angiotensin II type 1 receptor (AT1R) closely interacts with large conductance voltage- and Ca2+-activated K+ (BK) channels and inhibits their activity independent of G-protein activation. J Biol Chem 2014; 289:25678-89. [PMID: 25070892 DOI: 10.1074/jbc.m114.595603] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Angiotensin II (ANG-II) and BK channels play important roles in the regulation of blood pressure. In arterial smooth muscle, ANG-II inhibits BK channels, but the underlying molecular mechanisms are unknown. Here, we first investigated whether ANG-II utilizes its type 1 receptor (AT1R) to modulate BK activity. Pharmacological, biochemical, and molecular evidence supports a role for AT1R. In renal arterial myocytes, the AT1R antagonist losartan (10 μM) abolished the ANG-II (1 μM)-induced reduction of whole cell BK currents, and BK channels and ANG-II receptors were found to co-localize at the cell periphery. We also found that BK inhibition via ANG-II-activated AT1R was independent of G-protein activation (assessed with 500 μM GDPβS). In BK-expressing HEK293T cells, ANG-II (1 μM) also induced a reduction of BK currents, which was contingent on AT1R expression. The molecular mechanisms of AT1R and BK channel coupling were investigated in co-transfected cells. Co-immunoprecipitation showed formation of a macromolecular complex, and live immunolabeling demonstrated that both proteins co-localized at the plasma membrane with high proximity indexes as in arterial myocytes. Consistent with a close association, we discovered that the sole AT1R expression could decrease BK channel voltage sensitivity. Truncated BK proteins revealed that the voltage-sensing conduction cassette is sufficient for BK-AT1R association. Finally, C-terminal yellow and cyan fluorescent fusion proteins, AT1R-YFP and BK-CFP, displayed robust co-localized Förster resonance energy transfer, demonstrating intermolecular interactions at their C termini. Overall, our results strongly suggest that AT1R regulates BK channels through a close protein-protein interaction involving multiple BK regions and independent of G-protein activation.
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Affiliation(s)
- Zhu Zhang
- From the Departments of Anesthesiology
| | - Min Li
- From the Departments of Anesthesiology
| | - Rong Lu
- From the Departments of Anesthesiology
| | | | - Enrico Stefani
- From the Departments of Anesthesiology, Physiology, the Brain Research Institute, and the Cardiovascular Research Laboratory, University of California, Los Angeles, California 90095
| | - Ligia Toro
- From the Departments of Anesthesiology, the Brain Research Institute, and the Cardiovascular Research Laboratory, University of California, Los Angeles, California 90095 Molecular and Medical Pharmacology, and
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20
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Lin TF, Lin IW, Chen SC, Wu HH, Yang CS, Fang HY, Chiu MM, Jeng CJ. The subfamily-specific assembly of Eag and Erg K+ channels is determined by both the amino and the carboxyl recognition domains. J Biol Chem 2014; 289:22815-22834. [PMID: 25008323 DOI: 10.1074/jbc.m114.574814] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A functional voltage-gated K(+) (Kv) channel comprises four pore-forming α-subunits, and only members of the same Kv channel subfamily may co-assemble to form heterotetramers. The ether-à-go-go family of Kv channels (KCNH) encompasses three distinct subfamilies: Eag (Kv10), Erg (Kv11), and Elk (Kv12). Members of different ether-à-go-go subfamilies, such as Eag and Erg, fail to form heterotetramers. Although a short stretch of amino acid sequences in the distal C-terminal section has been implicated in subfamily-specific subunit assembly, it remains unclear whether this region serves as the sole and/or principal subfamily recognition domain for Eag and Erg. Here we aim to ascertain the structural basis underlying the subfamily specificity of ether-à-go-go channels by generating various chimeric constructs between rat Eag1 and human Erg subunits. Biochemical and electrophysiological characterizations of the subunit interaction properties of a series of different chimeric and truncation constructs over the C terminus suggested that the putative C-terminal recognition domain is dispensable for subfamily-specific assembly. Further chimeric analyses over the N terminus revealed that the N-terminal region may also harbor a subfamily recognition domain. Importantly, exchanging either the N-terminal or the C-terminal domain alone led to a virtual loss of the intersubfamily assembly boundary. By contrast, simultaneously swapping both recognition domains resulted in a reversal of subfamily specificity. Our observations are consistent with the notion that both the N-terminal and the C-terminal recognition domains are required to sustain the subfamily-specific assembly of rat Eag1 and human Erg.
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Affiliation(s)
- Ting-Feng Lin
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - I-Wen Lin
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Shu-Ching Chen
- Department of Medical Research, National Taiwan University Hospital, Taipei 10051, Taiwan
| | - Hao-Han Wu
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Chi-Sheng Yang
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Hsin-Yu Fang
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Mei-Miao Chiu
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan
| | - Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology, School of Medicine, and National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan; Brain Research Center, National Yang-Ming University, No. 155, Section 2, Li-Non Street, Taipei 12212, Taiwan and.
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21
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Thomson SJ, Hansen A, Sanguinetti MC. Concerted all-or-none subunit interactions mediate slow deactivation of human ether-à-go-go-related gene K+ channels. J Biol Chem 2014; 289:23428-36. [PMID: 25008322 DOI: 10.1074/jbc.m114.582437] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
During the repolarization phase of a cardiac action potential, hERG1 K(+) channels rapidly recover from an inactivated state then slowly deactivate to a closed state. The resulting resurgence of outward current terminates the plateau phase and is thus a key regulator of action potential duration of cardiomyocytes. The intracellular N-terminal domain of the hERG1 subunit is required for slow deactivation of the channel as its removal accelerates deactivation 10-fold. Here we investigate the stoichiometry of hERG1 channel deactivation by characterizing the kinetic properties of concatenated tetramers containing a variable number of wild-type and mutant subunits. Three mutations known to accelerate deactivation were investigated, including R56Q and R4A/R5A in the N terminus and F656I in the S6 transmembrane segment. In all cases, a single mutant subunit induced the same rapid deactivation of a concatenated channel as that observed for homotetrameric mutant channels. We conclude that slow deactivation gating of hERG1 channels involves a concerted, fully cooperative interaction between all four wild-type channel subunits.
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Affiliation(s)
- Steven J Thomson
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute and
| | - Angela Hansen
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute and
| | - Michael C Sanguinetti
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute and Department of Internal Medicine and Division of Cardiovascular Medicine, University of Utah, Salt Lake City, Utah 84112
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22
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Eckey K, Wrobel E, Strutz-Seebohm N, Pott L, Schmitt N, Seebohm G. Novel Kv7.1-phosphatidylinositol 4,5-bisphosphate interaction sites uncovered by charge neutralization scanning. J Biol Chem 2014; 289:22749-22758. [PMID: 24947509 DOI: 10.1074/jbc.m114.589796] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Kv7.1 to Kv7.5 α-subunits belong to the family of voltage-gated potassium channels (Kv). Assembled with the β-subunit KCNE1, Kv7.1 conducts the slowly activating potassium current IKs, which is one of the major currents underlying repolarization of the cardiac action potential. A known regulator of Kv7 channels is the lipid phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 increases the macroscopic current amplitude by stabilizing the open conformation of 7.1/KCNE1 channels. However, knowledge about the exact nature of the interaction is incomplete. The aim of this study was the identification of the amino acids responsible for the interaction between Kv7.1 and PIP2. We generated 13 charge neutralizing point mutations at the intracellular membrane border and characterized them electrophysiologically in complex with KCNE1 under the influence of diC8-PIP2. Electrophysiological analysis of corresponding long QT syndrome mutants suggested impaired PIP2 regulation as the cause for channel dysfunction. To clarify the underlying structural mechanism of PIP2 binding, molecular dynamics simulations of Kv7.1/KCNE1 complexes containing two PIP2 molecules in each subunit at specific sites were performed. Here, we identified a subset of nine residues participating in the interaction of PIP2 and Kv7.1/KCNE1. These residues may form at least two binding pockets per subunit, leading to the stabilization of channel conformations upon PIP2 binding.
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Affiliation(s)
- Karina Eckey
- Department of Biochemistry I-Cation Channel Group, Ruhr University Bochum, 44801 Bochum, Germany; International Graduate School of Neuroscience, Ruhr University Bochum, 44801 Bochum, Germany; Ruhr University Bochum Research School, and Ruhr University Bochum, 44801 Bochum, Germany
| | - Eva Wrobel
- IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and
| | - Nathalie Strutz-Seebohm
- IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and
| | - Lutz Pott
- Institute of Physiology, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, 1165 Copenhagen, Denmark
| | - Guiscard Seebohm
- International Graduate School of Neuroscience, Ruhr University Bochum, 44801 Bochum, Germany; Ruhr University Bochum Research School, and Ruhr University Bochum, 44801 Bochum, Germany; IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and.
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23
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Edwards W, Fung-Leung WP, Huang C, Chi E, Wu N, Liu Y, Maher MP, Bonesteel R, Connor J, Fellows R, Garcia E, Lee J, Lu L, Ngo K, Scott B, Zhou H, Swanson RV, Wickenden AD. Targeting the ion channel Kv1.3 with scorpion venom peptides engineered for potency, selectivity, and half-life. J Biol Chem 2014; 289:22704-22714. [PMID: 24939846 DOI: 10.1074/jbc.m114.568642] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Ion channels are an attractive class of drug targets, but progress in developing inhibitors for therapeutic use has been limited largely due to challenges in identifying subtype selective small molecules. Animal venoms provide an alternative source of ion channel modulators, and the venoms of several species, such as scorpions, spiders and snails, are known to be rich sources of ion channel modulating peptides. Importantly, these peptides often bind to hyper-variable extracellular loops, creating the potential for subtype selectivity rarely achieved with small molecules. We have engineered scorpion venom peptides and incorporated them in fusion proteins to generate highly potent and selective Kv1.3 inhibitors with long in vivo half-lives. Kv1.3 has been reported to play a role in human T cell activation, and therefore, these Kv1.3 inhibitor fusion proteins may have potential for the treatment of autoimmune diseases. Our results support an emerging approach to generating subtype selective therapeutic ion channel inhibitors.
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Affiliation(s)
- Wilson Edwards
- Janssen Research and Development, LLC, San Diego, California 92121.
| | | | - Chichi Huang
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Ellen Chi
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Nancy Wu
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Yi Liu
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Michael P Maher
- Janssen Research and Development, LLC, San Diego, California 92121
| | | | - Judith Connor
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Ross Fellows
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Elena Garcia
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Jerry Lee
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Lu Lu
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Karen Ngo
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Brian Scott
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Hong Zhou
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Ronald V Swanson
- Janssen Research and Development, LLC, San Diego, California 92121
| | - Alan D Wickenden
- Janssen Research and Development, LLC, San Diego, California 92121
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24
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Kitazawa M, Kubo Y, Nakajo K. The stoichiometry and biophysical properties of the Kv4 potassium channel complex with K+ channel-interacting protein (KChIP) subunits are variable, depending on the relative expression level. J Biol Chem 2014; 289:17597-609. [PMID: 24811166 DOI: 10.1074/jbc.m114.563452] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Kv4 is a voltage-gated K(+) channel, which underlies somatodendritic subthreshold A-type current (ISA) and cardiac transient outward K(+) (Ito) current. Various ion channel properties of Kv4 are known to be modulated by its auxiliary subunits, such as K(+) channel-interacting protein (KChIP) or dipeptidyl peptidase-like protein. KChIP is a cytoplasmic protein and increases the current amplitude, decelerates the inactivation, and accelerates the recovery from inactivation of Kv4. Crystal structure analysis demonstrated that Kv4 and KChIP form an octameric complex with four Kv4 subunits and four KChIP subunits. However, it remains unknown whether the Kv4·KChIP complex can have a different stoichiometry other than 4:4. In this study, we expressed Kv4.2 and KChIP4 with various ratios in Xenopus oocytes and observed that the biophysical properties of Kv4.2 gradually changed with the increase in co-expressed KChIP4. The tandem repeat constructs of Kv4.2 and KChIP4 revealed that the 4:4 (Kv4.2/KChIP4) channel shows faster recovery than the 4:2 channel, suggesting that the biophysical properties of Kv4.2 change, depending on the number of bound KChIP4s. Subunit counting by single-molecule imaging revealed that the bound number of KChIP4 in each Kv4.2·KChIP4 complex was dependent on the expression level of KChIP4. Taken together, we conclude that the stoichiometry of Kv4·KChIP complex is variable, and the biophysical properties of Kv4 change depending on the number of bound KChIP subunits.
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Affiliation(s)
- Masahiro Kitazawa
- From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan
| | - Yoshihiro Kubo
- From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan
| | - Koichi Nakajo
- From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan
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25
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Tang QY, Zhang Z, Meng XY, Cui M, Logothetis DE. Structural determinants of phosphatidylinositol 4,5-bisphosphate (PIP2) regulation of BK channel activity through the RCK1 Ca2+ coordination site. J Biol Chem 2014; 289:18860-72. [PMID: 24778177 DOI: 10.1074/jbc.m113.538033] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Big or high conductance potassium (BK) channels are activated by voltage and intracellular calcium (Ca(2+)). Phosphatidylinositol 4,5-bisphosphate (PIP2), a ubiquitous modulator of ion channel activity, has been reported to enhance Ca(2+)-driven gating of BK channels, but a molecular understanding of this interplay or even of the PIP2 regulation of this channel's activity remains elusive. Here, we identify structural determinants in the KDRDD loop (which follows the αA helix in the RCK1 domain) to be responsible for the coupling between Ca(2+) and PIP2 in regulating BK channel activity. In the absence of Ca(2+), RCK1 structural elements limit channel activation through a decrease in the channel's PIP2 apparent affinity. This inhibitory influence of BK channel activation can be relieved by mutation of residues that (a) connect either the RCK1 Ca(2+) coordination site (Asp(367) or its flanking basic residues in the KDRDD loop) to the PIP2-interacting residues (Lys(392) and Arg(393)) found in the αB helix or (b) are involved in hydrophobic interactions between the αA and αB helix of the RCK1 domain. In the presence of Ca(2+), the RCK1-inhibitory influence of channel-PIP2 interactions and channel activity is relieved by Ca(2+) engaging Asp(367). Our results demonstrate that, along with Ca(2+) and voltage, PIP2 is a third factor critical to the integral control of BK channel activity.
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Affiliation(s)
- Qiong-Yao Tang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298 and the Jiangsu Province Key Laboratory of Anesthesiology and Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical College, Xuzhou 221004, China
| | - Zhe Zhang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298 and the Jiangsu Province Key Laboratory of Anesthesiology and Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical College, Xuzhou 221004, China
| | - Xuan-Yu Meng
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298 and
| | - Meng Cui
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298 and
| | - Diomedes E Logothetis
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298 and
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26
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Liu HW, Hou PP, Guo XY, Zhao ZW, Hu B, Li X, Wang LY, Ding JP, Wang S. Structural basis for calcium and magnesium regulation of a large conductance calcium-activated potassium channel with β1 subunits. J Biol Chem 2014; 289:16914-23. [PMID: 24764303 DOI: 10.1074/jbc.m114.557991] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Large conductance Ca(2+)- and voltage-activated potassium (BK) channels, composed of pore-forming α subunits and auxiliary β subunits, play important roles in diverse physiological activities. The β1 is predominately expressed in smooth muscle cells, where it greatly enhances the Ca(2+) sensitivity of BK channels for proper regulation of smooth muscle tone. However, the structural basis underlying dynamic interaction between BK mSlo1 α and β1 remains elusive. Using macroscopic ionic current recordings in various Ca(2+) and Mg(2+) concentrations, we identified two binding sites on the cytosolic N terminus of β1, namely the electrostatic enhancing site (mSlo1(K392,R393)-β1(E13,T14)), increasing the calcium sensitivity of BK channels, and the hydrophobic site (mSlo1(L906,L908)-β1(L5,V6,M7)), passing the physical force from the Ca(2+) bowl onto the enhancing site and S6 C-linker. Dynamic binding of these sites affects the interaction between the cytosolic domain and voltage-sensing domain, leading to the reduction of Mg(2+) sensitivity. A comprehensive structural model of the BK(mSlo1 α-β1) complex was reconstructed based on these functional studies, which provides structural and mechanistic insights for understanding BK gating.
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Affiliation(s)
- Hao-Wen Liu
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Pan-Pan Hou
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Xi-Ying Guo
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Zhi-Wen Zhao
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Bin Hu
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Xia Li
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Lu-Yang Wang
- the Program in Neurosciences and Mental Health, SickKids Research Institute and Department of Physiology, University of Toronto, Toronto, Ontario M5G 1X8, Canada
| | - Jiu-Ping Ding
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
| | - Sheng Wang
- From the Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China and
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27
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Abstract
As all integral membrane proteins, voltage-gated ion channels are embedded in a lipid matrix that regulates their channel behavior either by physicochemical properties or by direct binding. Because manipulation of the lipid composition in cells is difficult, we investigated the influence of different lipids on purified KvAP channels reconstituted in planar lipid bilayers of known composition. Lipids developed two distinct and independent effects on the KvAP channels; lipids interacting with the pore lowered the energy barriers for the final transitions, whereas voltage sensor-bound lipids shifted the midpoint of activation dependent on their electrostatic charge. Above all, the midpoint of activation was determined only by those lipids the channels came in contact with first after purification and can seemingly only be exchanged if the channel resides in the open state. The high affinity of the bound lipids to the binding site has implications not only on our understanding of the gating mechanism but also on the general experimental design of any lipid dependence study.
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Affiliation(s)
- Élise Faure
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, Canada Physiology
| | - Christine Thompson
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, CanadaFrom the Departments of Physics and
| | - Rikard Blunck
- Groupe d'étude des protéines membranaires (GÉPROM), Université de Montréal, Montréal CH3C 3J7, Canada Physiology, From the Departments of Physics and
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28
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Yang W, Feng J, Wang B, Cao Z, Li W, Wu Y, Chen Z. BF9, the first functionally characterized snake toxin peptide with Kunitz-type protease and potassium channel inhibiting properties. J Biochem Mol Toxicol 2013; 28:76-83. [PMID: 24243656 DOI: 10.1002/jbt.21538] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Revised: 10/16/2013] [Indexed: 12/14/2022]
Abstract
Although numerous Kunitz-type toxins were isolated from snake venom, no bifunctional Kunitz-type snake toxins with protease and potassium channel inhibiting properties have been reported till now. With the help of bioinformatics analyses and biological experiments, we characterized Kunitz-type snake toxin BF9 as a bifunctional peptide. Enzyme and inhibitor reaction kinetics experiments showed that BF9 inhibited α-chymotrypsin with Ki value of 1.8 × 10⁻⁸ M. Electrophysiological experiments showed that BF9 inhibited the Kv1.3 potassium channel with an IC₅₀ of 120.0 nM, which demonstrated that serine protease inhibitor BF9 could also inhibit potassium channels. In addition, the key amino acids of BF9 responsible for the unique bifunctional mechanism are further investigated. To the best of our knowledge, BF9 is the first Kunitz-type snake peptide with the unique bifunctionality of potassium channel and serine protease inhibiting properties, providing novel insights into divergent evolution and functional applications of snake Kunitz-type peptides.
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Affiliation(s)
- Weishan Yang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
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