1
|
Hussain S, De Waele J, Lammens M, Bosmans F. N-Type Inactivation Variances in Honeybee and Asian Giant Hornet Kv Channels. Bioelectricity 2022. [DOI: 10.1089/bioe.2022.0006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Shahid Hussain
- Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| | - Jolien De Waele
- Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| | - Maxime Lammens
- Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| | - Frank Bosmans
- Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| |
Collapse
|
2
|
Niespodziany I, Mullier B, André VM, Ghisdal P, Jnoff E, Moreno-Delgado D, Swinnen D, Sands Z, Wood M, Wolff C. Discovery of a small molecule modulator of the Kv1.1/Kvβ1 channel complex that reduces neuronal excitability and in vitro epileptiform activity. CNS Neurosci Ther 2018; 25:442-451. [PMID: 30242974 DOI: 10.1111/cns.13060] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/13/2018] [Accepted: 08/15/2018] [Indexed: 11/27/2022] Open
Abstract
AIMS Kv1.1 (KCNA1) channels contribute to the control of neuronal excitability and have been associated with epilepsy. Kv1.1 channels can associate with the cytoplasmic Kvβ1 subunit resulting in rapid inactivating A-type currents. We hypothesized that removal of channel inactivation, by modulating Kv1.1/Kvβ1 interaction with a small molecule, would lead to decreased neuronal excitability and anticonvulsant activity. METHODS We applied high-throughput screening to identify ligands able to modulate the Kv1.1-T1 domain/Kvβ1 protein complex. We then selected a compound that was characterized on recombinant Kv1.1/Kvβ1 channels by electrophysiology and further evaluated on sustained neuronal firing and on in vitro epileptiform activity using a high K+ -low Ca2+ model in hippocampal slices. RESULTS We identified a novel compound able to modulate the interaction of the Kv1.1/Kvβ1 complex and that produced a functional inhibition of Kv1.1/Kvβ1 channel inactivation. We demonstrated that this compound reduced the sustained repetitive firing in hippocampal neurons and was able to abolish the development of in vitro epileptiform activity. CONCLUSIONS This study describes a rational drug discovery approach for the identification of novel ligands that inhibit Kv1.1 channel inactivation and provides pharmacological evidence that such a mechanism translates into physiological effects by reducing in vitro epileptiform activity.
Collapse
Affiliation(s)
| | - Brice Mullier
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | | | - Philippe Ghisdal
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | - Eric Jnoff
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | | | - Dominique Swinnen
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | - Zara Sands
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | - Martyn Wood
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| | - Christian Wolff
- Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium
| |
Collapse
|
3
|
Bishop HI, Cobb MM, Kirmiz M, Parajuli LK, Mandikian D, Philp AM, Melnik M, Kuja-Panula J, Rauvala H, Shigemoto R, Murray KD, Trimmer JS. Kv2 Ion Channels Determine the Expression and Localization of the Associated AMIGO-1 Cell Adhesion Molecule in Adult Brain Neurons. Front Mol Neurosci 2018; 11:1. [PMID: 29403353 PMCID: PMC5780429 DOI: 10.3389/fnmol.2018.00001] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/03/2018] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated K+ (Kv) channels play important roles in regulating neuronal excitability. Kv channels comprise four principal α subunits, and transmembrane and/or cytoplasmic auxiliary subunits that modify diverse aspects of channel function. AMIGO-1, which mediates homophilic cell adhesion underlying neurite outgrowth and fasciculation during development, has recently been shown to be an auxiliary subunit of adult brain Kv2.1-containing Kv channels. We show that AMIGO-1 is extensively colocalized with both Kv2.1 and its paralog Kv2.2 in brain neurons across diverse mammals, and that in adult brain, there is no apparent population of AMIGO-1 outside of that colocalized with these Kv2 α subunits. AMIGO-1 is coclustered with Kv2 α subunits at specific plasma membrane (PM) sites associated with hypolemmal subsurface cisternae at neuronal ER:PM junctions. This distinct PM clustering of AMIGO-1 is not observed in brain neurons of mice lacking Kv2 α subunit expression. Moreover, in heterologous cells, coexpression of either Kv2.1 or Kv2.2 is sufficient to drive clustering of the otherwise uniformly expressed AMIGO-1. Kv2 α subunit coexpression also increases biosynthetic intracellular trafficking and PM expression of AMIGO-1 in heterologous cells, and analyses of Kv2.1 and Kv2.2 knockout mice show selective loss of AMIGO-1 expression and localization in neurons lacking the respective Kv2 α subunit. Together, these data suggest that in mammalian brain neurons, AMIGO-1 is exclusively associated with Kv2 α subunits, and that Kv2 α subunits are obligatory in determining the correct pattern of AMIGO-1 expression, PM trafficking and clustering.
Collapse
Affiliation(s)
- Hannah I Bishop
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Melanie M Cobb
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Michael Kirmiz
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Laxmi K Parajuli
- Center for Neuroscience, University of California, Davis, Davis, CA, United States.,Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki, Japan
| | - Danielle Mandikian
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Ashleigh M Philp
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Mikhail Melnik
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | | | - Heikki Rauvala
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Ryuichi Shigemoto
- Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki, Japan
| | - Karl D Murray
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States.,Center for Neuroscience, University of California, Davis, Davis, CA, United States
| | - James S Trimmer
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States.,Department Physiology and Membrane Biology, University of California, Davis, Davis, CA, United States
| |
Collapse
|
4
|
Sakamoto K, Suzuki Y, Yamamura H, Ohya S, Muraki K, Imaizumi Y. Molecular mechanisms underlying pimaric acid-induced modulation of voltage-gated K + channels. J Pharmacol Sci 2017; 133:223-231. [PMID: 28391996 DOI: 10.1016/j.jphs.2017.02.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 02/11/2017] [Accepted: 02/21/2017] [Indexed: 01/14/2023] Open
Abstract
Voltage-gated K+ (KV) channels, which control firing and shape of action potentials in excitable cells, are supposed to be potential therapeutic targets in many types of diseases. Pimaric acid (PiMA) is a unique opener of large conductance Ca2+-activated K+ channel. Here, we report that PiMA modulates recombinant rodent KV channel activity. The enhancement was significant at low potentials (<0 mV) but not at more positive potentials. Application of PiMA significantly shifted the voltage-activation relationships (V1/2) of rodent KV1.1, 1.2, 1.3, 1.4, 1.6 and 2.1 channels (KV1.1-KV2.1) but KV4.3 to lower potentials and prolonged their half-decay times of the deactivation (T1/2D). The amino acid sequence which is responsible for the difference in response to PiMA was examined between KV1.1-KV2.1 and KV4.3 by site-directed mutagenesis of residues in S5 and S6 segments of Kv1.1. The point mutation of Phe332 into Tyr mimics the effects of PiMA on V1/2 and T1/2D and also abolished the further change by addition of PiMA. The results indicate that PiMA enhances voltage sensitivity of KV1.1-KV2.1 channels and suggest that the lipophilic residues including Phe332 in S5 of KV1.1-KV2.1 channels may be critical for the effects of PiMA, providing beneficial information for drug development of KV channel openers.
Collapse
Affiliation(s)
- Kazuho Sakamoto
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan; Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yoshiaki Suzuki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Hisao Yamamura
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Susumu Ohya
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan; Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
| | - Katsuhiko Muraki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan; Laboratory Cellular Pharmacology, School of Pharmacy, Aichi Gakuin University, Nagoya 464-8650, Japan
| | - Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
| |
Collapse
|
5
|
Jerng HH, Pfaffinger PJ. S-glutathionylation of an auxiliary subunit confers redox sensitivity to Kv4 channel inactivation. PLoS One 2014; 9:e93315. [PMID: 24675763 PMCID: PMC3968176 DOI: 10.1371/journal.pone.0093315] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 03/04/2014] [Indexed: 12/24/2022] Open
Abstract
Reactive oxygen species (ROS) regulate ion channels, modulate neuronal excitability, and contribute to the etiology of neurodegenerative disorders. ROS differentially suppress fast "ball-and-chain" N-type inactivation of cloned Kv1 and Kv3 potassium channels but not of Kv4 channels, likely due to a lack of reactive cysteines in Kv4 N-termini. Recently, we discovered that N-type inactivation of Kv4 channel complexes can be independently conferred by certain N-terminal variants of Kv4 auxiliary subunits (DPP6a, DPP10a). Here, we report that both DPP6a and DPP10a, like Kv subunits with redox-sensitive N-type inactivation, contain a highly conserved cysteine in their N-termini (Cys-13). To test if N-type inactivation mediated by DPP6a or DPP10a is redox sensitive, Xenopus oocyte recordings were performed to examine the effects of two common oxidants, tert-butyl hydroperoxide (tBHP) and diamide. Both oxidants markedly modulate DPP6a- or DPP10a-conferred N-type inactivation of Kv4 channels, slowing the overall inactivation and increasing the peak current. These functional effects are fully reversed by the reducing agent dithiothreitol (DTT) and appear to be due to a selective modulation of the N-type inactivation mediated by these auxiliary subunits. Mutation of DPP6a Cys-13 to serine eliminated the tBHP or diamide effects, confirming the importance of Cys-13 to the oxidative regulation. Biochemical studies designed to elucidate the underlying molecular mechanism show no evidence of protein-protein disulfide linkage formation following cysteine oxidation. Instead, using a biotinylated glutathione (BioGEE) reagent, we discovered that oxidation by tBHP or diamide leads to S-glutathionylation of Cys-13, suggesting that S-glutathionylation underlies the regulation of fast N-type inactivation by redox. In conclusion, our studies suggest that Kv4-based A-type current in neurons may show differential redox sensitivity depending on whether DPP6a or DPP10a is highly expressed, and that the S-glutathionylation mechanism may play a previously unappreciated role in mediating excitability changes and neuropathologies associated with ROS.
Collapse
Affiliation(s)
- Henry H. Jerng
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Paul J. Pfaffinger
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| |
Collapse
|
6
|
Tian C, Zhu R, Zhu L, Qiu T, Cao Z, Kang T. Potassium Channels: Structures, Diseases, and Modulators. Chem Biol Drug Des 2013; 83:1-26. [DOI: 10.1111/cbdd.12237] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Chuan Tian
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| | - Ruixin Zhu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Lixin Zhu
- Department of Pediatrics; Digestive Diseases and Nutrition Center; The State University of New York at Buffalo; Buffalo NY 14226 USA
| | - Tianyi Qiu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Zhiwei Cao
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Tingguo Kang
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| |
Collapse
|
7
|
Pfaffinger PJ. A conserved pre-block interaction motif regulates potassium channel activation and N-type inactivation. PLoS One 2013; 8:e79891. [PMID: 24236164 PMCID: PMC3827413 DOI: 10.1371/journal.pone.0079891] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 10/06/2013] [Indexed: 02/02/2023] Open
Abstract
N-type inactivation occurs when the N-terminus of a potassium channel binds into the open pore of the channel. This study examined the relationship between activation and steady state inactivation for mutations affecting the N-type inactivation properties of the Aplysia potassium channel AKv1 expressed in Xenopus oocytes. The results show that the traditional single-step model for N-type inactivation fails to properly account for the observed relationship between steady state channel activation and inactivation curves. We find that the midpoint of the steady state inactivation curve depends in part on a secondary interaction between the channel core and a region of the N-terminus just proximal to the pore blocking peptide that we call the Inactivation Proximal (IP) region. The IP interaction with the channel core produces a negative shift in the activation and inactivation curves, without blocking the pore. A tripeptide motif in the IP region was identified in a large number of different N-type inactivation domains most likely reflecting convergent evolution in addition to direct descent. Point mutating a conserved hydrophobic residue in this motif eliminates the gating voltage shift, accelerates recovery from inactivation and decreases the amount of pore block produced during inactivation. The IP interaction we have identified likely stabilizes the open state and positions the pore blocking region of the N-terminus at the internal opening to the transmembrane pore by forming a Pre-Block (P state) interaction with residues lining the side window vestibule of the channel.
Collapse
Affiliation(s)
- Paul J. Pfaffinger
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
| |
Collapse
|
8
|
Huang GS, Hong MY. Functional and Molecular Characterization for the Damp-Obstructed Rat Model in Chinese Medicine. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 34:323-40. [PMID: 16552842 DOI: 10.1142/s0192415x06003862] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Functional and molecular characterization was performed on the major organs of damp-obstructed rats by applying expression datasets of microarray experiments and real-time RT-PCR. Gene ontology repertoires, i.e. cellular component, molecular function, and biological process were used to classify differentially expressed genes in the major organs of rats upon treatment of dampness. As to the cellular component, over-expression of genes associated with the plasma membrane was observed in the stomach, spleen, kidney, heart, liver, and lung. Genes associated with translational machinery, endoplasmic recticulum membrane, Golgi apparatus, and nuclear envelope were down-regulated in the stomach. Concerning the molecular function, genes associated with oxidoreductase activity were up-regulated in the stomach, spleen, kidney, lung, and brain. Channel activity, membrane receptor, and electron transporter activity were up-regulated in stomach, kidney, and lung. Regarding the biological process, genes associated with signal transduction were up-regulated in the stomach, while genes associated with biosynthesis and ATP metabolism were down-regulated. In the spleen, melanin biosynthesis was up-regulated while hormone-related activities were down-regulated. In the kidney, genes associated with nucleotide biosynthesis and ATP metabolism were depressed. In the heart and liver, apoptosis was up-regulated while immune response and RAS signal transduction were down-regulated. Interestingly, genes associated with oncogenesis were up-regulated in the stomach and kidney. Functional fingerprints indicated that dampness weakened membrane structures, depressed metabolic activity (especially ATP metabolism), damaged matrix proteins, enhanced signal transduction, and revealed a positive association with oncogenesis. To quantify the functional impact at the molecular level, mRNA levels of key genes were determined by real-time RT-PCR. The results indicated that ATP storage in kidney, spleen, and stomach was depleted in damp-obstructed rats. We propose that oxidative stress, membrane integrity, melanin biosynthesis, ion channel activity, and ATP metabolism might be hallmarks for damp-obstructed rats. Our results also suggested dampness as a pathogenic factor in rats which is possibly associated with enhanced liabilities of cancer.
Collapse
Affiliation(s)
- G Steven Huang
- Institute of Nanotechnology, National Chiao Tung University, Hsinchu 300, Taiwan.
| | | |
Collapse
|
9
|
Castle NA. Pharmacological modulation of voltage-gated potassium channels as a therapeutic strategy. Expert Opin Ther Pat 2010; 20:1471-503. [PMID: 20726689 DOI: 10.1517/13543776.2010.513384] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
IMPORTANCE OF THE FIELD The human genome encodes at least 40 distinct voltage-gated potassium channel subtypes, which vary in regional expression, pharmacological and biophysical properties. Voltage-dependent potassium (Kv) channels help orchestrate many of the physiological and pathophysiological processes that promote and sometimes hinder the healthy functioning of our bodies. AREAS COVERED IN THIS REVIEW This review summarizes patent and scientific literature reports from the past decade highlighting the opportunities that Kv channels offer for the development of new therapeutic interventions for a wide variety of disorders. WHAT THE READER WILL GAIN The reader will gain an insight from an analysis of the associations of different Kv family members with disease processes, summary and evaluation of the development of therapeutically relevant pharmacological modulators of these channels, particularly focusing on proprietary agents being developed. TAKE HOME MESSAGE Development of new drugs that target Kv channels continue to be of great interest but is proving to be challenging. Nevertheless, opportunities for Kv channel modulators to have an impact on a wide range of disorders in the future remain an exciting prospect.
Collapse
|
10
|
Abstract
The human genome encodes 40 voltage-gated K(+) channels (K(V)), which are involved in diverse physiological processes ranging from repolarization of neuronal and cardiac action potentials, to regulating Ca(2+) signalling and cell volume, to driving cellular proliferation and migration. K(V) channels offer tremendous opportunities for the development of new drugs to treat cancer, autoimmune diseases and metabolic, neurological and cardiovascular disorders. This Review discusses pharmacological strategies for targeting K(V) channels with venom peptides, antibodies and small molecules, and highlights recent progress in the preclinical and clinical development of drugs targeting the K(V)1 subfamily, the K(V)7 subfamily (also known as KCNQ), K(V)10.1 (also known as EAG1 and KCNH1) and K(V)11.1 (also known as HERG and KCNH2) channels.
Collapse
|
11
|
Jerng HH, Dougherty K, Covarrubias M, Pfaffinger PJ. A novel N-terminal motif of dipeptidyl peptidase-like proteins produces rapid inactivation of KV4.2 channels by a pore-blocking mechanism. Channels (Austin) 2009; 3:448-61. [PMID: 19901547 DOI: 10.4161/chan.3.6.10216] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The somatodendritic subthreshold A-type K(+) current in neurons (I(SA)) depends on its kinetic and voltage-dependent properties to regulate membrane excitability, action potential repetitive firing, and signal integration. Key functional properties of the K(V)4 channel complex underlying I(SA) are determined by dipeptidyl peptidase-like proteins known as dipeptidyl peptidase 6 (DPP6) and dipeptidyl peptidase 10 (DPP10). Among the multiple known DPP10 isoforms with alternative N-terminal sequences, DPP10a confers exceptionally fast inactivation to K(V)4.2 channels. To elucidate the molecular basis of this fast inactivation, we investigated the structure-function relationship of the DPP10a N-terminal region and its interaction with the K(V)4.2 channel. Here, we show that DPP10a shares a conserved N-terminal sequence (MNQTA) with DPP6a (aka DPP6-E), which also induces fast inactivation. Deletion of the NQTA sequence in DPP10a eliminates this dramatic fast inactivation, and perfusion of MNQTA peptide to the cytoplasmic face of inside-out patches inhibits the K(V)4.2 current. DPP10a-induced fast inactivation exhibits competitive interactions with internally applied tetraethylammonium (TEA), and elevating the external K(+) concentration accelerates recovery from DPP10a-mediated fast inactivation. These results suggest that fast inactivation induced by DPP10a or DPP6a is mediated by a common N-terminal inactivation motif via a pore-blocking mechanism. This mechanism may offer an attractive target for novel pharmacological interventions directed at impairing I(SA) inactivation and reducing neuronal excitability.
Collapse
Affiliation(s)
- Henry H Jerng
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
| | | | | | | |
Collapse
|
12
|
Kryukova Y, Rybin VO, Qu J, Steinberg SF, Robinson RB. Age-dependent differences in the inhibition of HCN2 current in rat ventricular myocytes by the tyrosine kinase inhibitor erbstatin. Pflugers Arch 2008; 457:821-30. [PMID: 18696104 DOI: 10.1007/s00424-008-0565-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 06/27/2008] [Accepted: 07/26/2008] [Indexed: 10/21/2022]
Abstract
Previously, we have shown that murine HCN2 channels over-expressed in newborn and adult cardiac myocytes produce currents with different biophysical characteristics. To investigate the role of tyrosine kinase modulation in these age-dependent differences, we employed the broad spectrum tyrosine kinase inhibitor erbstatin. Our results demonstrated distinct and separable effects of erbstatin on channel gating and current amplitude and a marked age dependence to these effects. In newborn myocytes, erbstatin decreased current amplitude, shifted the activation relation negative, and slowed activation kinetics. The effect on activation voltage but not that on amplitude was absent when expressing a cAMP-insensitive mutant (HCN2R/E), while a C-terminal truncated form of HCN2 (HCN2DeltaCx) exhibited only the voltage dependent but not the amplitude effect of erbstatin. Thus, the action of erbstatin on the activation relation and current amplitude are distinct and separable in newborn myocytes, and the effect on activation voltage depends on the cAMP status of HCN2 channels. In contrast to newborn myocytes, erbstatin had no effect on HCN2 under control conditions in adult myocytes but induced a negative shift with no change in amplitude when saturated cAMP was added to the pipette solution. We conclude that erbstatin's effects on HCN2 current magnitude and voltage dependence are distinct and separable, and there are fundamental developmental differences in the heart that affect channel function and its modulation by the tyrosine kinase inhibitor erbstatin.
Collapse
Affiliation(s)
- Yelena Kryukova
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | | | | | | | | |
Collapse
|
13
|
Rhodes KJ, Trimmer JS. Antibody-based validation of CNS ion channel drug targets. ACTA ACUST UNITED AC 2008; 131:407-13. [PMID: 18411328 PMCID: PMC2346570 DOI: 10.1085/jgp.200709926] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
14
|
|