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Denisova KR, Orlov NA, Yakimov SA, Kryukova EA, Dolgikh DA, Kirpichnikov MP, Feofanov AV, Nekrasova OV. GFP-Margatoxin, a Genetically Encoded Fluorescent Ligand to Probe Affinity of Kv1.3 Channel Blockers. Int J Mol Sci 2022; 23:1724. [PMID: 35163644 DOI: 10.3390/ijms23031724] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/30/2022] [Accepted: 01/31/2022] [Indexed: 02/01/2023] Open
Abstract
Peptide pore blockers and their fluorescent derivatives are useful molecular probes to study the structure and functions of the voltage-gated potassium Kv1.3 channel, which is considered as a pharmacological target in the treatment of autoimmune and neurological disorders. We present Kv1.3 fluorescent ligand, GFP-MgTx, constructed on the basis of green fluorescent protein (GFP) and margatoxin (MgTx), the peptide, which is widely used in physiological studies of Kv1.3. Expression of the fluorescent ligand in E. coli cells resulted in correctly folded and functionally active GFP-MgTx with a yield of 30 mg per 1 L of culture. Complex of GFP-MgTx with the Kv1.3 binding site is reported to have the dissociation constant of 11 ± 2 nM. GFP-MgTx as a component of an analytical system based on the hybrid KcsA-Kv1.3 channel is shown to be applicable to recognize Kv1.3 pore blockers of peptide origin and to evaluate their affinities to Kv1.3. GFP-MgTx can be used in screening and pre-selection of Kv1.3 channel blockers as potential drug candidates.
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Maezawa I, Nguyen HM, Di Lucente J, Jenkins DP, Singh V, Hilt S, Kim K, Rangaraju S, Levey AI, Wulff H, Jin LW. Kv1.3 inhibition as a potential microglia-targeted therapy for Alzheimer's disease: preclinical proof of concept. Brain 2019; 141:596-612. [PMID: 29272333 DOI: 10.1093/brain/awx346] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 10/30/2017] [Indexed: 12/14/2022] Open
Abstract
Microglia significantly contribute to the pathophysiology of Alzheimer's disease but an effective microglia-targeted therapeutic approach is not yet available clinically. The potassium channels Kv1.3 and Kir2.1 play important roles in regulating immune cell functions and have been implicated by in vitro studies in the 'M1-like pro-inflammatory' or 'M2-like anti-inflammatory' state of microglia, respectively. We here found that amyloid-β oligomer-induced expression of Kv1.3 and Kir2.1 in cultured primary microglia. Likewise, ex vivo microglia acutely isolated from the Alzheimer's model 5xFAD mice co-expressed Kv1.3 and Kir2.1 as well as markers traditionally associated with M1 and M2 activation suggesting that amyloid-β oligomer induces a microglial activation state that is more complex than previously thought. Using the orally available, brain penetrant small molecule Kv1.3 blocker PAP-1 as a tool, we showed that pro-inflammatory and neurotoxic microglial responses induced by amyloid-β oligomer required Kv1.3 activity in vitro and in hippocampal slices. Since we further observed that Kv1.3 was highly expressed in microglia of transgenic Alzheimer's mouse models and human Alzheimer's disease brains, we hypothesized that pharmacological Kv1.3 inhibition could mitigate the pathology induced by amyloid-β aggregates. Indeed, treating APP/PS1 transgenic mice with a 5-month oral regimen of PAP-1, starting at 9 months of age, when the animals already manifest cognitive deficits and amyloid pathology, reduced neuroinflammation, decreased cerebral amyloid load, enhanced hippocampal neuronal plasticity, and improved behavioural deficits. The observed decrease in cerebral amyloid deposition was consistent with the in vitro finding that PAP-1 enhanced amyloid-β uptake by microglia. Collectively, these results provide proof-of-concept data to advance Kv1.3 blockers to Alzheimer's disease clinical trials.
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Affiliation(s)
- Izumi Maezawa
- Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, 2805 50th Street, Sacramento, CA 95817, USA
| | - Hai M Nguyen
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Jacopo Di Lucente
- Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, 2805 50th Street, Sacramento, CA 95817, USA
| | - David Paul Jenkins
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Vikrant Singh
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Silvia Hilt
- Department of Biochemistry and Molecular Medicine, University of California Davis, 2700 Stockton Blvd, Sacramento, CA 95817, USA
| | - Kyoungmi Kim
- Department of Public Health Sciences, University of California Davis, One Shields Avenue, Med Sci 1-C, Davis, CA 95616, USA
| | - Srikant Rangaraju
- Department of Neurology and Alzheimer's Disease Research Center, Emory University, 201 Dowman Drive, Atlanta, GA 30322, USA
| | - Allan I Levey
- Department of Neurology and Alzheimer's Disease Research Center, Emory University, 201 Dowman Drive, Atlanta, GA 30322, USA
| | - Heike Wulff
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Lee-Way Jin
- Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, 2805 50th Street, Sacramento, CA 95817, USA.,Alzheimer's Disease Center, University of California Davis Medical Center, 4860 Y Street, Suite 3900, Sacramento, CA 95817, USA
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Di Lucente J, Nguyen HM, Wulff H, Jin LW, Maezawa I. The voltage-gated potassium channel Kv1.3 is required for microglial pro-inflammatory activation in vivo. Glia 2018; 66:1881-1895. [PMID: 30043400 DOI: 10.1002/glia.23457] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [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: 10/10/2017] [Revised: 04/26/2018] [Accepted: 05/02/2018] [Indexed: 11/09/2022]
Abstract
Microglia show a rich repertoire of activation patterns regulated by a complex ensemble of surface ion channels, receptors, and transporters. We and others have investigated whether microglia vary their K+ channel expression as a means to achieve functional diversity. However, most of the prior studies were conducted using in vitro models such as BV2 cells, primary microglia, or brain slices in culture, which may not accurately reflect microglia physiology in adult individuals. Here we employed an in vivo mouse model of selective innate immune activation by intracerebroventricular injection of lipopolysaccharides (ICV-LPS) to determine the role of the voltage-gated Kv1.3 channel in LPS-induced M1-like microglial activation. Using microglia acutely isolated from adult brains, we detected Kv1.3 and Kir2.1 currents, and found that ICV-LPS increased the current density and RNA expression of Kv1.3 but did not affect those of Kir2.1. Genetic knockout of Kv1.3 abolished LPS-induced microglial activation exemplified by Iba-1 immunoreactivity and expression of pro-inflammatory mediators such as IL-1β, TNF-α, IL-6, and iNOS. Moreover, Kv1.3 knockout mitigated the LPS-induced impairment of hippocampal long-term potentiation (hLTP), suggesting that Kv1.3 activity regulates pro-inflammatory microglial neurotoxicity. Pharmacological intervention using PAP-1, a small molecule that selectively blocks homotetrameric Kv1.3 channels, achieved anti-inflammatory and hLTP-recovery effects similar to Kv1.3 knockout. We conclude that Kv1.3 is required for microglial M1-like pro-inflammatory activation in vivo. A significant implication of our in vivo data is that Kv1.3 blockers could be therapeutic candidates for neurological diseases where microglia-mediated neurotoxicity is implicated in the pathogenesis.
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Affiliation(s)
- Jacopo Di Lucente
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
| | - Hai M Nguyen
- Department of Pharmacology, University of California, Davis, California
| | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California
| | - Lee-Way Jin
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
| | - Izumi Maezawa
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
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Voros O, Szilagyi O, Balajthy A, Somodi S, Panyi G, Hajdu P. The C-terminal HRET sequence of Kv1.3 regulates gating rather than targeting of Kv1.3 to the plasma membrane. Sci Rep 2018; 8:5937. [PMID: 29650988 PMCID: PMC5897520 DOI: 10.1038/s41598-018-24159-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 03/08/2018] [Indexed: 12/13/2022] Open
Abstract
Kv1.3 channels are expressed in several cell types including immune cells, such as T lymphocytes. The targeting of Kv1.3 to the plasma membrane is essential for T cell clonal expansion and assumed to be guided by the C-terminus of the channel. Using two point mutants of Kv1.3 with remarkably different features compared to the wild-type Kv1.3 (A413V and H399K having fast inactivation kinetics and tetraethylammonium-insensitivity, respectively) we showed that both Kv1.3 channel variants target to the membrane when the C-terminus was truncated right after the conserved HRET sequence and produce currents identical to those with a full-length C-terminus. The truncation before the HRET sequence (NOHRET channels) resulted in reduced membrane-targeting but non-functional phenotypes. NOHRET channels did not display gating currents, and coexpression with wild-type Kv1.3 did not rescue the NOHRET-A413V phenotype, no heteromeric current was observed. Interestingly, mutants of wild-type Kv1.3 lacking HRET(E) (deletion) or substituted with five alanines for the HRET(E) motif expressed current indistinguishable from the wild-type. These results demonstrate that the C-terminal region of Kv1.3 immediately proximal to the S6 helix is required for the activation gating and conduction, whereas the presence of the distal region of the C-terminus is not exclusively required for trafficking of Kv1.3 to the plasma membrane.
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Affiliation(s)
- Orsolya Voros
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Orsolya Szilagyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - András Balajthy
- Department of Pediatrics, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Sándor Somodi
- Department of Internal Medicine, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 1 Egyetem sq., 4032, Hungary. MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, 400, Debrecen, Hungary
| | - Péter Hajdu
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary. .,Department of Biophysics and Cell Biology, Faculty of Dentistry, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary.
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Bednenko J, Harriman R, Mariën L, Nguyen HM, Agrawal A, Papoyan A, Bisharyan Y, Cardarelli J, Cassidy-Hanley D, Clark T, Pedersen D, Abdiche Y, Harriman W, van der Woning B, de Haard H, Collarini E, Wulff H, Colussi P. A multiplatform strategy for the discovery of conventional monoclonal antibodies that inhibit the voltage-gated potassium channel Kv1.3. MAbs 2018; 10:636-650. [PMID: 29494279 PMCID: PMC5973702 DOI: 10.1080/19420862.2018.1445451] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [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] [Indexed: 11/19/2022] Open
Abstract
Identifying monoclonal antibodies that block human voltage-gated ion channels (VGICs) is a challenging endeavor exacerbated by difficulties in producing recombinant ion channel proteins in amounts that support drug discovery programs. We have developed a general strategy to address this challenge by combining high-level expression of recombinant VGICs in Tetrahymena thermophila with immunization of phylogenetically diverse species and unique screening tools that allow deep-mining for antibodies that could potentially bind functionally important regions of the protein. Using this approach, we targeted human Kv1.3, a voltage-gated potassium channel widely recognized as a therapeutic target for the treatment of a variety of T-cell mediated autoimmune diseases. Recombinant Kv1.3 was used to generate and recover 69 full-length anti-Kv1.3 mAbs from immunized chickens and llamas, of which 10 were able to inhibit Kv1.3 current. Select antibodies were shown to be potent (IC50<10 nM) and specific for Kv1.3 over related Kv1 family members, hERG and hNav1.5.
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Affiliation(s)
| | - Rian Harriman
- b Department of Immunology , Crystal Bioscience , Emeryville , California , USA
| | | | - Hai M Nguyen
- d Department of Pharmacology , University of California , Davis , California , USA
| | - Alka Agrawal
- a TetraGenetics Inc , Arlington , Massachusetts , USA
| | - Ashot Papoyan
- a TetraGenetics Inc , Arlington , Massachusetts , USA
| | | | | | - Donna Cassidy-Hanley
- e Department of Immunology and Microbiology , Cornell University , Ithaca , New York , USA
| | - Ted Clark
- a TetraGenetics Inc , Arlington , Massachusetts , USA.,e Department of Immunology and Microbiology , Cornell University , Ithaca , New York , USA
| | | | | | | | | | | | | | - Heike Wulff
- d Department of Pharmacology , University of California , Davis , California , USA
| | - Paul Colussi
- a TetraGenetics Inc , Arlington , Massachusetts , USA
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Kuzmenkov AI, Grishin EV, Vassilevski AA. Diversity of Potassium Channel Ligands: Focus on Scorpion Toxins. Biochemistry Moscow 2016; 80:1764-99. [DOI: 10.1134/s0006297915130118] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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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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Bose T, Cieślar-Pobuda A, Wiechec E. Role of ion channels in regulating Ca²⁺ homeostasis during the interplay between immune and cancer cells. Cell Death Dis 2015; 6:e1648. [PMID: 25695601 PMCID: PMC4669790 DOI: 10.1038/cddis.2015.23] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 12/23/2014] [Accepted: 01/06/2015] [Indexed: 01/08/2023]
Abstract
Ion channels are abundantly expressed in both excitable and non-excitable cells, thereby regulating the Ca2+ influx and downstream signaling pathways of physiological processes. The immune system is specialized in the process of cancer cell recognition and elimination, and is regulated by different ion channels. In comparison with the immune cells, ion channels behave differently in cancer cells by making the tumor cells more hyperpolarized and influence cancer cell proliferation and metastasis. Therefore, ion channels comprise an important therapeutic target in anti-cancer treatment. In this review, we discuss the implication of ion channels in regulation of Ca2+ homeostasis during the crosstalk between immune and cancer cell as well as their role in cancer progression.
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Affiliation(s)
- T Bose
- Leibniz-Institute of Neurobiology, Brenneckestrasse 6, D-39 Magdeburg, Germany
| | - A Cieślar-Pobuda
- 1] Department of Clinical and Experimental Medicine, Division of Cell Biology & Integrative Regenerative Medicine Center (IGEN), Linköping University, 581 85 Linköping, Sweden [2] Biosystems Group, Institute of Automatic Control, Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland
| | - E Wiechec
- Department of Clinical and Experimental Medicine, Division of Cell Biology & Integrative Regenerative Medicine Center (IGEN), Linköping University, 581 85 Linköping, Sweden
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Kudryashova KS, Nekrasova OV, Kuzmenkov AI, Vassilevski AA, Ignatova AA, Korolkova YV, Grishin EV, Kirpichnikov MP, Feofanov AV. Fluorescent system based on bacterial expression of hybrid KcsA channels designed for Kv1.3 ligand screening and study. Anal Bioanal Chem 2013; 405:2379-89. [DOI: 10.1007/s00216-012-6655-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/22/2012] [Accepted: 12/12/2012] [Indexed: 10/27/2022]
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Wu SN, Chen BS, Lo YC. Evidence for aconitine-induced inhibition of delayed rectifier K(+) current in Jurkat T-lymphocytes. Toxicology 2011; 289:11-8. [PMID: 21782880 DOI: 10.1016/j.tox.2011.07.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 07/04/2011] [Accepted: 07/06/2011] [Indexed: 02/07/2023]
Abstract
Aconitine (ACO) is a highly toxic diterpenoid alkaloid and known to exert the immunomodulatory action. However, whether it has any effects on ion currents in immune cells remains unknown. The effects of ACO and other related compounds on ion currents in Jurkat T-lymphocytes were investigated in this study. ACO suppressed the amplitude of delayed-rectifier K(+) current (I(K(DR))) in a time- and concentration-dependent manner. Margatoxin (100 nM), a specific blocker of K(V)1.3-encoded current, decreased the I(K(DR)) amplitude in these cells and the ACO-induced inhibition of I(K(DR)) was not reversed by 1-ethyl-2-benzimidazolinone (30 μM) or nicotine (10 μM). The IC(50) value for ACO-mediated inhibition of I(K(DR)) was 5.6 μM. ACO accelerated the inactivation of I(K(DR)) with no change in the activation rate of this current. Increasing the ACO concentration not only reduced the I(K(DR)) amplitude, but also accelerated the inactivation time course of the current. With the aid of minimal binding scheme, the inhibitory action of ACO on I(K(DR)) was estimated with a dissociation constant of 6.8 μM. ACO also shifted the inactivation curve of I(K(DR)) to a hyperpolarized potential with no change in the slope factor. Cumulative inactivation for I(K(DR)) was enhanced in the presence of ACO. In Jurkat cells incubated with amiloride (30 μM), the ACO-induced inhibition of I(K(DR)) remained unaltered. In RAW 264.7 murine macrophages, ACO did not modify the kinetics of I(K(DR)), although it suppressed I(K(DR)) amplitude. Taken together, these effects can significantly contribute to its action on functional activity of immune cells if similar results are found in vivo.
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Affiliation(s)
- Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan.
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11
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Ramirez-Navarro A, Glazebrook PA, Kane-Sutton M, Padro C, Kline DD, Kunze DL. Kv1.3 channels regulate synaptic transmission in the nucleus of solitary tract. J Neurophysiol 2011; 105:2772-80. [PMID: 21430270 DOI: 10.1152/jn.00494.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The voltage-gated K(+) channel Kv1.3 has been reported to regulate transmitter release in select central and peripheral neurons. In this study, we evaluated its role at the synapse between visceral sensory afferents and secondary neurons in the nucleus of the solitary tract (NTS). We identified mRNA and protein for Kv1.3 in rat nodose ganglia using RT-PCR and Western blot analysis. In immunohistochemical experiments, anti-Kv1.3 immunoreactivity was very strong in internal organelles in the soma of nodose neurons with a weaker distribution near the plasma membrane. Anti-Kv1.3 was also identified in the axonal branches that project centrally, including their presynaptic terminals in the medial and commissural NTS. In current-clamp experiments, margatoxin (MgTx), a high-affinity blocker of Kv1.3, produced an increase in action potential duration in C-type but not A- or Ah-type neurons. To evaluate the role of Kv1.3 at the presynaptic terminal, we examined the effect of MgTx on tract evoked monosynaptic excitatory postsynaptic currents (EPSCs) in brain slices of the NTS. MgTx increased the amplitude of evoked EPSCs in a subset of neurons, with the major increase occurring during the first stimuli in a 20-Hz train. These data, together with the results from somal recordings, support the hypothesis that Kv1.3 regulates the duration of the action potential in the presynaptic terminal of C fibers, limiting transmitter release to the postsynaptic cell.
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Affiliation(s)
- Angelina Ramirez-Navarro
- Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, OH 44109-1998, USA
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Jang SH, Choi SY, Ryu PD, Lee SY. Anti-proliferative effect of Kv1.3 blockers in A549 human lung adenocarcinoma in vitro and in vivo. Eur J Pharmacol 2011; 651:26-32. [DOI: 10.1016/j.ejphar.2010.10.066] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 10/07/2010] [Accepted: 10/29/2010] [Indexed: 01/05/2023]
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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.
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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.
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Valencia-Cruz G, Shabala L, Delgado-Enciso I, Shabala S, Bonales-Alatorre E, Pottosin II, Dobrovinskaya OR. K(bg) and Kv1.3 channels mediate potassium efflux in the early phase of apoptosis in Jurkat T lymphocytes. Am J Physiol Cell Physiol 2009; 297:C1544-53. [PMID: 19794143 DOI: 10.1152/ajpcell.00064.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Microelectrode ion flux estimation (MIFE) and patch-clamp techniques were combined for noninvasive K(+) flux measurements and recording of activities of the dominant K(+) channels in the early phases of apoptosis in Jurkat cells. Staurosporine (STS, 1 microM) evoked rapid (peaking around 15 min) transient K(+) efflux, which then gradually decreased. This transient K(+) efflux occurred concurrently with the transient increase of the K(+) background (K(bg)) TWIK-related spinal cord K(+) channel-like current density, followed by a drastic decrease and concomitant membrane depolarization. The Kv1.3 current density remained almost constant. Kv1.3 activation was not altered by STS, whereas the inactivation was shifted to more positive potentials. Contribution of K(bg) and Kv1.3 channels to the transient and posttransient STS-induced K(+) efflux components, respectively, was confirmed by the effects of bupivacaine, predominantly blocking K(bg) current, and the Kv1.3-specific blocker margatoxin. Channel-mediated K(+) efflux provoked a substantial cellular shrinkage and affected the activation of caspases.
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16
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Matsushita Y, Ohya S, Suzuki Y, Itoda H, Kimura T, Yamamura H, Imaizumi Y. Inhibition of Kv1.3 potassium current by phosphoinositides and stromal-derived factor-1α in Jurkat T cells. Am J Physiol Cell Physiol 2009; 296:C1079-85. [DOI: 10.1152/ajpcell.00668.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The activation of Kv1.3 potassium channel has obligatory roles in immune responses of T lymphocytes. Stromal cell-derived factor-1α (SDF-1α) binds to C-X-C chemokine receptor type 4, activates phosphoinositide 3-kinase, and plays essential roles in cell migration of T lymphocytes. In this study, the effects of phosphoinositides and SDF-1α on Kv1.3 current activity were examined in the Jurkat T cell line using whole cell patch-clamp techniques. The internal application of 10 μM phosphatidylinositol 4,5-bisphosphate (PIP2) or 10 μM phosphatidylinositol-3,4,5-trisphosphate (PIP3) significantly reduced Kv1.3 current, but that of 10 μM phosphatidylinositol-4-monophosphate (PIP) did not. The coapplication of 10 μg/ml anti-PIP3 antibody with PIP2 from the pipette did not change the reduction of Kv1.3 current by PIP2, but the coapplication of the antibody with PIP3 eliminated the reduction. The heat-inactivated anti-PIP3 antibody had no effect on PIP3-induced inhibition. These results suggest that PIP2 per se can reduce Kv1.3 current as well as PIP3. External application of 1 μM Akt-kinase inhibitor VIII did not reverse the effect of intracellular PIP3. External application of 10 and 30 ng/ml SDF-1α significantly reduced Kv1.3 current. Internal application of anti-PIP3 antibody reversed the SDF-1α-induced reduction. These results suggest that, in Jurkat T cells, PIP2, PIP3, and SDF-1α reduce Kv1.3 channel activity and that the reduction by SDF-1α may be mediated by the enhancement of PIP3 production. These novel inhibitory effects of phosphoinositides and SDF-1α on Kv1.3 current may have a significant function as a downregulation mechanism of Kv1.3 activity for the maintenance of T lymphocyte activation in immune responses.
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Zhu J, Recio-Pinto E, Hartwig T, Sellers W, Yan J, Thornhill WB. The Kv1.2 potassium channel: the position of an N-glycan on the extracellular linkers affects its protein expression and function. Brain Res 2008; 1251:16-29. [PMID: 19056359 DOI: 10.1016/j.brainres.2008.11.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 10/24/2008] [Accepted: 11/10/2008] [Indexed: 12/15/2022]
Abstract
Voltage-gated potassium Kv1 channels have three extracellular linkers, the S1-S2, the S3-S4, and the S5-P. The S1-S2 is the only linker that has an N-glycan and it is at a conserved position on this linker on Kv1.1-Kv1.5 and Kv1.7 channels. We hypothesize that an N-glycan is found at only this position due to its effect on folding, trafficking, and/or function of these channels. To investigate this hypothesis, N-glycosylation sites were engineered at different positions on the extracellular linkers of Kv1.2 to determine the effects of N-glycans on channel surface protein expression and function. Our data suggest that for Kv1 channels, (1) placing an N-glycan at non-native positions on the S1-S2 linker decreased cell surface protein expression but the N-glycan still affected function similarly as if it were at its native position, (2) placing a non-native N-glycan on the S3-S4 linker significantly altered function, and (3) placing a non-native N-glycan on the S5-P linker disrupted both trafficking and function. We suggest that Kv1 channels have an N-glycan at a conserved position on only the S1-S2 linker to overcome the constraints for proper folding, trafficking, and function that appear to occur if the N-glycan is moved from this position.
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Affiliation(s)
- Jing Zhu
- Department of Biological Sciences, Fordham University, Bronx, NY 10458, USA
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18
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Matsushita Y, Ohya S, Itoda H, Kimura T, Suzuki Y, Yamamura H, Imaizumi Y. Molecular mechanisms for Kv1.3 potassium channel current inhibition by CD3/CD28 stimulation in Jurkat T cells. Biochem Biophys Res Commun 2008; 374:152-7. [DOI: 10.1016/j.bbrc.2008.06.118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2008] [Accepted: 06/28/2008] [Indexed: 10/21/2022]
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Affiliation(s)
- Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA.
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Watanabe I, Zhu J, Sutachan JJ, Gottschalk A, Recio-Pinto E, Thornhill WB. The glycosylation state of Kv1.2 potassium channels affects trafficking, gating, and simulated action potentials. Brain Res 2007; 1144:1-18. [PMID: 17324383 DOI: 10.1016/j.brainres.2007.01.092] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 12/21/2006] [Accepted: 01/20/2007] [Indexed: 10/23/2022]
Abstract
We presented evidence previously that decreasing the glycosylation state of the Kv1.1 potassium channel modified its gating by a combined surface potential and a cooperative subunit interaction mechanism and these effects modified simulated action potentials. Here we continued to test the hypothesis that glycosylation affects channel function in a predictable fashion by increasing and decreasing the glycosylation state of Kv1.2 channels. Compared with Kv1.2, increasing the glycosylation state shifted the V(1/2) negatively with a steeper G-V slope, increased activation kinetics with little change in deactivation kinetics or in their voltage-dependence, and decreased the apparent level of C-type inactivation. Decreasing the glycosylation state had essentially the opposite effects and shifted the V(1/2) positively with a shallower G-V slope, decreased activation kinetics (and voltage-dependence), decreased deactivation kinetics, and increased the apparent level of C-type inactivation. Single channel conductance was not affected by the different glycosylation states of Kv1.2 tested here. Hyperpolarized or depolarized shifts in V(1/2) from wild type were apparently due to an increased or decreased level of channel sialylation, respectively. Data and modeling suggested that the changes in activation properties were mostly predictable within and between channels and were consistent with a surface potential mechanism, but those on deactivation properties were not predictable and were more consistent with a conformational mechanism. Moreover the effect on the deactivation process appeared to be channel-type dependent as well as glycosylation-site dependent. The glycosylation state of Kv1.2 also affected action potentials in simulations. In addition, preventing N-glycosylation decreased cell surface Kv1.2 expression levels by approximately 40% primarily by increasing partial endoplasmic reticulum retention and this effect was completely rescued by Kv1.4 subunits, which are glycosylated, but not by cytoplasmic Kvbeta2.1 subunits. The nonglycosylated Kv1.2 protein had a similar protein half-life as the glycosylated protein and appeared to be folded properly. Thus altering the native Kv1.2 glycosylation state affected its trafficking, gating, and simulated action potentials. Differential glycosylation of ion channels could be used by excitable cells to modify cell signaling.
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Affiliation(s)
- Itaru Watanabe
- Department of Biological Sciences, Fordham University, Bronx, New York 10458, USA
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21
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Abstract
Neurodegeneration induced by excitatory neurotransmitter glutamate is considered to be of particular relevance in several types of acute and chronic neurological impairments ranging from cerebral ischaemia to neuropathological conditions such as motor neuron disease, Alzheimer's, Parkinson's disease and epilepsy. The hyperexcitation of glutamate receptors coupled with calcium overload can be prevented or modulated by using well-established competitive and non-competitive antagonists targeting ion/receptor channels. The exponentially increasing body of pharmacological evidence over the years indicates potential applications of peptide toxins, due to their exquisite subtype selectivity on ion channels and receptors, as lead structures for the development of drugs for the treatment of wide variety of neurological disorders. This review comprehensively highlights the overview of the diversity in the molecular as well as neurobiological mechanisms of different peptide toxins derived from venomous animals with particular reference to neuroprotection. In addition, the potential applications of peptide toxins in the diagnosis and treatment of neurological disorders such as neuromuscular disorders, epilepsy, Alzheimer's and Parkinson's diseases, gliomas and ischaemic stroke and their future prospects in the diagnosis as well as in the therapy are addressed.
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Affiliation(s)
- Wudayagiri Rajendra
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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22
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Abstract
Human peripheral blood T lymphocytes possess two types of K(+) channels: the voltage-gated Kv1.3 and the calcium-activated IKCa1 channels. The use of peptidyl inhibitors of Kv1.3 and IKCa1 indicated that these channels are involved in the maintenance of membrane potential and that they play a crucial role in Ca(2+) signaling during T-cell activation. Thus, in vitro blockade of Kv1.3 and IKCa1 leads to inhibition of cytokine production and lymphocyte proliferation. These observations prompted several groups of investigators in academia and pharmaceutical companies to characterize the expression of Kv1.3 and IKCa1 in different subsets of human T lymphocytes and to evaluate their potential as novel targets for immunosuppression. Recent in vivo studies showed that chronically activated T lymphocytes involved in the pathogenesis of multiple sclerosis present unusually high expression of Kv1.3 channels and that the treatment with selective Kv1.3 inhibitors can either prevent or ameliorate the symptoms of the disease. In this model of multiple sclerosis, blockade of IKCa1 channels had no effect alone, but improved the response to Kv1.3 inhibitors. In addition, the expression of Kv1.3 and IKCa1 channels in human cells is very restricted, which makes them attractive targets for a more cell-specific and less harmful action than what is typically obtained with classical immunosuppressants. Studies using high-throughput toxin displacement, (86)Rb-efflux screening or membrane potential assays led to the identification of non-peptidyl small molecules with high affinity for Kv1.3 or IKCa1 channels. Analysis of structure-function relationships in Kv1.3 and IKCa1 channels helped define the binding sites for channel blockers, allowing the design of a new generation of small molecules with selectivity for either Kv1.3 or IKCa1, which could help the development of new drugs for safer treatment of auto-immune diseases.
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Affiliation(s)
- Rosane Vianna-Jorge
- Divisão de Farmacologia, Coordenação de Pesquisa, Instituto Nacional de Câncer, Rio de Janeiro, Brazil.
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Abstract
K(+) channels play an important role in glial cell proliferation and are functionally expressed in glial tumors. Because voltage-gated K(+) channel (Kv) subtypes Kv1.3 and Kv1.5 have been shown to contribute to growth-related properties of normal glia rather specifically, we investigated different human glioma samples for the expression of these channel subtypes using reverse transcriptase-PCR. Kv1.5 expression correlated with glioma entities and malignancy grades, i.e. expression was high in astrocytomas, moderate in oligodendrogliomas, and low in glioblastomas. No such correlation was evident for Kv1.3 expression. This study shows a clear differential expression of Kv1.5 in gliomas according to subtype and malignancy grade. This result corresponds to previous data on the expression of voltage-gated sodium channels in gliomas, which likewise showed a low or absent expression of channel subtypes in high-grade tumors.
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Affiliation(s)
- Katja Preussat
- Institute of Pathology (Neuropathology), Friedrich Schiller University Jena, Bachstrasse 18, D-07740 Jena, Germany
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Zhu J, Watanabe I, Gomez B, Thornhill WB. Heteromeric Kv1 potassium channel expression: amino acid determinants involved in processing and trafficking to the cell surface. J Biol Chem 2003; 278:25558-67. [PMID: 12730233 DOI: 10.1074/jbc.m207984200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Kv1.4 and Kv1.1 potassium channels are expressed in brain as mature glycoproteins that are trans-Golgi glycosylated. When expressed in cell lines these homomers had very different trans-Golgi glycosylation efficiencies and cell surface expression levels with Kv1.4 > Kv1.1 for both parameters (Zhu, J., Watanabe, I., Gomez, B., and Thornhill, W. B. (2001) J. Biol. Chem. 276, 39419-39427). This previous study identified determinants in the outer pore region of Kv1.4 and Kv1.1 that positively and negatively, respectively, affected these events when expressed as homomers. Here we investigated which subunit exhibited positive or negative effects on these processes when expressed as heteromers. Kv1.4/Kv1.1 heteromers, by coexpression or expression as tandem-linked heteromers, were expressed on the cell surface at approximately 20-fold lower levels versus Kv1.4 homomers but they were trans-Golgi glycosylated. The lower Kv1.4/Kv1.1 expression level was not rescued by Kvbeta 2.1 subunits. Thus Kv1.1 inhibited high cell surface expression and partially retained the heteromer in the endoplasmic reticulum, whereas Kv1.4 stimulated trans-Golgi glycosylation. The subunit determinants and cellular events responsible for these differences were investigated. In a Kv1.4/Kv1.1 heteromer, the Kv1.1 pore was a major negative determinant, and it inhibited high cell surface expression because it induced high partial endoplasmic reticulum retention and it decreased protein stability. Other Kv1.1 regions also inhibited high surface expression of heteromers. The Kv1.1 C terminus induced partial Golgi retention and contributed to a decreased protein stability, whereas the Kv1.1 N terminus contributed to only a decreased protein stability. Thus a neuron may regulate its cell surface K+ channel protein levels by different Kv1 subfamily homomeric and heteromeric combinations that affect intracellular retention characteristics and protein stability.
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Affiliation(s)
- Jing Zhu
- Department of Biological Sciences, Fordham University, Bronx, New York 10458, USA
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Watanabe I, Wang HG, Sutachan JJ, Zhu J, Recio-Pinto E, Thornhill WB. Glycosylation affects rat Kv1.1 potassium channel gating by a combined surface potential and cooperative subunit interaction mechanism. J Physiol 2003; 550:51-66. [PMID: 12879861 PMCID: PMC2343013 DOI: 10.1113/jphysiol.2003.040337] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The effect of glycosylation on Kv1.l potassium channel function was investigated in mammalian cells stably transfected with Kv1.l or Kv1.1N207Q. Macroscopic current analysis showed that both channels were expressed but Kv1.1N207Q, which was not glycosylated, displayed functional differences compared with wild-type, including slowed activation kinetics, a positively shifted V 1/2, a shallower slope for the conductance versus voltage relationship, slowed C-type inactivation kinetics, and a reduced extent of and recovery from C-type inactivation. Kv1. 1N207Q activation properties were also less sensitive to divalent cations compared with those of Kv1.l. These effects were largely due to the lack of trans-Golgi added sugars, such as galactose and sialic acid, to the N207 carbohydrate tree. No apparent change in ionic current deactivation kinetics was detected inKv1.1N207Q compared with wild-type. Our data, coupled with modelling, suggested that removal of the N207 carbohydrate tree had two major effects. The first effect slowed the concerted channel transition from the last dosed state to the open state without changing the voltage dependence of its kinetics. This effect contributed to the G-V curve depolarization shift and together with the lower sensitivity to divalent cations suggested that the carbohydrate tree and its negatively charged sialic acids affected the negative surface charge density on the channel's extracellular face that was sensed by the activation gating machinery. The second effect reduced a cooperativity factor that slowed the transition from the open state to the dosed state without changing its voltage dependence. This effect accounted for the shallower G-V slope, and contributed to the depolarized G-V shift, and together with the inactivation changes it suggested that the carbohydrate tree also affected channel conformations. Thus N-glycosylation, and particularly terminal sialylation, affected Kv1.l gating properties both by altering the surface potential sensed by the channel's activation gating machinery and by modifying conformational changes regulating cooperative subunit interactions during activation and inactivation. Differences in glycosylation pattern among closely related channels may contribute to their functional differences and affect their physiological roles.
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Affiliation(s)
- Itaru Watanabe
- Department of Biological Sciences, Fordham University, Bronx, NY 10458, USA
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Schroeder N, Mullmann TJ, Schmalhofer WA, Gao YD, Garcia ML, Giangiacomo KM. Glycine 30 in iberiotoxin is a critical determinant of its specificity for maxi-K versus K(V) channels. FEBS Lett 2002; 527:298-302. [PMID: 12220678 DOI: 10.1016/s0014-5793(02)03256-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Iberiotoxin (IbTX) is a remarkably selective alpha-K toxin peptide (alpha-KTx) inhibitor of the maxi-K channel. In contrast, the highly homologous charybdotoxin inhibits both the maxi-K and K(V)1.3 channels with similar high affinity. The present study investigates the molecular basis for this specificity through mutagenesis of IbTX. The interactions of mutated peptides with maxi-K and K(V)1.3 channels were monitored through dose-dependent displacement of specifically bound iodinated alpha-KTx peptides from membranes expressing these channels. Results of these studies suggest that the presence of a glycine at position 30 in IbTX is a major determinant of its specificity while the presence of four unique acidic residues in IbTX is not.
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Affiliation(s)
- Nathan Schroeder
- Department of Biochemistry, Temple University School of Medicine, 3420 N. Broad Street, Philadelphia, PA 19140, USA
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Racapé J, Lecoq A, Romi-Lebrun R, Liu J, Kohler M, Garcia ML, Ménez A, Gasparini S. Characterization of a novel radiolabeled peptide selective for a subpopulation of voltage-gated potassium channels in mammalian brain. J Biol Chem 2002; 277:3886-93. [PMID: 11707459 DOI: 10.1074/jbc.m109886200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BgK, a 37-amino acid voltage-gated potassium (Kv) 1 channel blocker isolated from the sea anemone Bunodosoma granulifera, can be modified at certain positions to alter its pharmacological profile (Alessandri-Haber, N., Lecoq, A., Gasparini, S., Grangier-Macmath, G., Jacquet, G., Harvey, A. L., de Medeiros, C., Rowan, E. G., Gola, M., Ménez, A., and Crest, M. (1999) J. Biol. Chem. 274, 35653-35661). In the present study, we report the design of two BgK analogs that have been radiolabeled with (125)INa. Whereas BgK(W5Y/Y26F) and its radiolabeled derivative, (125)I-BgK(W5Y/Y26F), bind to Kv1.1, Kv1.2, and Kv1.6 channels with potencies similar to those for the parent peptide, BgK, BgK(W5Y/F6A/Y26F) and its monoiodo-tyrosine derivative, (125)I-BgK(W5Y/F6A/Y26F), display a distinctive and unique pharmacological profile; they bind with high affinity to homomultimeric Kv1.1 and Kv1.6 channels, but not to Kv1.2 channels. Interaction of BgK(W5Y/F6A/Y26F) with potassium channels depends on the nature of a residue in the mouth of the channel, at a position that determines channel sensitivity to external tetraethylammonium. In native brain tissue, (125)I-BgK(W5Y/F6A/Y26F) binds to a population of Kv1 channels that appear to consist of at least two sensitive (Kv1.1 and/or Kv1.6) subunits, in adjacent position. Given its unique pharmacological properties, (125)I-BgK(W5Y/F6A/Y26F) represents a new tool for studying subpopulations of Kv1 channels in native tissues.
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Affiliation(s)
- Judith Racapé
- Département d'Ingénierie et d'Etudes des Protéines, Commissariat à l'Energie Atomique Saclay, 91191 Gif sur Yvette cedex, France
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Chung I, Zelivyanskaya M, Gendelman HE. Mononuclear phagocyte biophysiology influences brain transendothelial and tissue migration: implication for HIV-1-associated dementia. J Neuroimmunol 2002; 122:40-54. [PMID: 11777542 DOI: 10.1016/s0165-5728(01)00462-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mononuclear phagocyte (MP) brain migration influence neuronal damage during HIV-1-associated dementia (HAD). We demonstrate that potassium channels, expressed in human monocyte-derived macrophages (MDM), are vital for MP movement through Boyden chemotactic chambers, an artificial blood-brain barrier and organotypic hippocampal brain slices. MDM migration is inhibited by voltage-and calcium-activated potassium channel blockers that include charybodotoxin, margatoxin, agatoxin and apamin. This is observed both in uninfected and HIV-1-infected MP. The results suggest that potassium channels affect MDM brain migration through altering cell volume and shape. Such mechanisms likely affect MP-induced neuronal destruction during HAD.
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Affiliation(s)
- Induk Chung
- The Center for Neurovirology and Neurodegenerative Disorders, Departments of Pathology and Microbiology, University of Nebraska Medical Center, 985215 Nebraska Medical Center, Omaha, NE 68198-5215, USA
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Legros C, Pollmann V, Knaus HG, Farrell AM, Darbon H, Bougis PE, Martin-Eauclaire MF, Pongs O. Generating a high affinity scorpion toxin receptor in KcsA-Kv1.3 chimeric potassium channels. J Biol Chem 2000; 275:16918-24. [PMID: 10828071 DOI: 10.1074/jbc.275.22.16918] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of the bacterial K(+) channel, KcsA (Doyle, D. A., Morais, C. J., Pfuetzner, R. A., Kuo, A., Gulbis, J. M., Cohen, S. L., Chait, B. T., and MacKinnon, R. (1998) Science 280, 69-77), and subsequent mutagenesis have revealed a high structural conservation from bacteria to human (MacKinnon, R., Cohen, S. L., Kuo, A., Lee, A., and Chait, B. T. (1998) Science 280, 106-109). We have explored this conservation by swapping subregions of the M1-M2 linker of KcsA with those of the S5-S6 linker of the human Kv-channel Kv1.3. The chimeric K(+) channel constructs were expressed in Escherichia coli, and their multimeric state was analyzed after purification. We used two scorpion toxins, kaliotoxin and hongotoxin 1, which bind specifically to Kv1.3, to analyze the pharmacological properties of the KcsA-Kv1.3 chimeras. The results demonstrate that the high affinity scorpion toxin receptor of Kv1.3 could be transferred to KcsA. Our biochemical studies with purified KcsA-Kv1.3 chimeras provide direct chemical evidence that a tetrameric channel structure is necessary for forming a functional scorpion toxin receptor. We have obtained KcsA-Kv1.3 chimeras with kaliotoxin affinities (IC(50) values of approximately 4 pm) like native Kv1.3 channels. Furthermore, we show that a subregion of the S5-S6 linker may be an important determinant of the pharmacological profile of K(+) channels. Using available structural information on KcsA and kaliotoxin, we have developed a structural model for the complex between KcsA-Kv1.3 chimeras and kaliotoxin to aid future pharmacological studies of K(+) channels.
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Affiliation(s)
- C Legros
- Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, D-20246 Hamburg, Germany
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30
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Hanner M, Schmalhofer WA, Green B, Bordallo C, Liu J, Slaughter RS, Kaczorowski GJ, Garcia ML. Binding of correolide to K(v)1 family potassium channels. Mapping the domains of high affinity interaction. J Biol Chem 1999; 274:25237-44. [PMID: 10464244 DOI: 10.1074/jbc.274.36.25237] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Correolide, a novel nortriterpene natural product, potently inhibits the voltage-gated potassium channel, K(v)1.3, and [(3)H]dihydrocorreolide (diTC) binds with high affinity (K(d) approximately 10 nM) to membranes from Chinese hamster ovary cells that express K(v)1.3 (Felix, J. P., Bugianesi, R. M., Schmalhofer, W. A., Borris, R., Goetz, M. A., Hensens, O. D., Bao, J.-M., Kayser, F. , Parsons, W. H., Rupprecht, K., Garcia, M. L., Kaczorowski, G. J., and Slaughter, R. S. (1999) Biochemistry 38, 4922-4930). Mutagenesis studies were used to localize the diTC binding site and to design a high affinity receptor in the diTC-insensitive channel, K(v)3.2. Transferring the pore from K(v)1.3 to K(v)3.2 produces a chimera that binds peptidyl inhibitors of K(v)1.3 with high affinity, but not diTC. Transfer of the S(5) region of K(v)1.3 to K(v)3.2 reconstitutes diTC binding at 4-fold lower affinity as compared with K(v)1.3, whereas transfer of the entire S(5)-S(6) domain results in a normal K(v)1.3 phenotype. Substitutions in S(5)-S(6) of K(v)1.3 with nonconserved residues from K(v)3.2 has identified two positions in S(5) and one in S(6) that cause significant alterations in diTC binding. High affinity diTC binding can be conferred to K(v)3.2 after substitution of these three residues with the corresponding amino acids found in K(v)1.3. These results suggest that lack of sensitivity of K(v)3.2 to diTC is a consequence of the presence of Phe(382) and Ile(387) in S(5), and Met(458) in S(6). Inspection of K(v)1.1-1.6 channels indicates that they all possess identical S(5) and S(6) domains. As expected, diTC binds with high affinity (K(d) values 7-21 nM) to each of these homotetrameric channels. However, the kinetics of binding are fastest with K(v)1.3 and K(v)1.4, suggesting that conformations associated with C-type inactivation will facilitate entry and exit of diTC at its binding site. Taken together, these findings identify K(v)1 channel regions necessary for high affinity diTC binding, as well as, reveal a channel conformation that markedly influences the rate of binding of this ligand.
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Affiliation(s)
- M Hanner
- Department of Membrane Biochemistry and Biophysics, Merck Research Laboratories, Rahway, New Jersey 07065, USA
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Abstract
Several important new findings have furthered the development of voltage-gated and calcium-activated potassium channel pharmacology. The molecular constituents of several members of these large ion channel families were identified. Small-molecule modulators of some of these channels were reported, including correolide, the first potent, small-molecule, natural product inhibitor of the Shaker family of voltage-gated potassium channels to be disclosed. The initial crystal structure of a bacterial potassium channel was determined; this work gives a physical basis for understanding the mechanisms of ion selectivity and ion conduction. With the recent molecular characterization of a potassium channel structure and the discovery of new templates for channel modulatory agents, the ability to rationally identify and develop potassium channel agonists and antagonists may become a reality in the near future.
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Affiliation(s)
- G J Kaczorowski
- Department of Membrane Biochemistry and Biophysics, Merck Research Laboratories, PO Box 2000, 80N-31C, Rahway, NJ 07065, USA.
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Koschak A, Bugianesi RM, Mitterdorfer J, Kaczorowski GJ, Garcia ML, Knaus HG. Subunit composition of brain voltage-gated potassium channels determined by hongotoxin-1, a novel peptide derived from Centruroides limbatus venom. J Biol Chem 1998; 273:2639-44. [PMID: 9446567 DOI: 10.1074/jbc.273.5.2639] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Five novel peptidyl inhibitors of Shaker-type (Kv1) K+ channels have been purified to homogeneity from venom of the scorpion Centruroides limbatus. The complete primary amino acid sequence of the major component, hongotoxin-1 (HgTX1), has been determined and confirmed after expression of the peptide in Escherichia coli. HgTX1 inhibits 125I-margatoxin binding to rat brain membranes as well as depolarization-induced 86Rb+ flux through homotetrameric Kv1.1, Kv1. 2, and Kv1.3 channels stably transfected in HEK-293 cells, but it displays much lower affinity for Kv1.6 channels. A HgTX1 double mutant (HgTX1-A19Y/Y37F) was constructed to allow high specific activity iodination of the peptide. HgTX1-A19Y/Y37F and monoiodinated HgTX1-A19Y/Y37F are equally potent in inhibiting 125I-margatoxin binding to rat brain membranes as HgTX1 (IC50 values approximately 0.3 pM). 125I-HgTX1-A19Y/Y37F binds with subpicomolar affinities to membranes derived from HEK-293 cells expressing homotetrameric Kv1.1, Kv1.2, and Kv1.3 channels and to rat brain membranes (Kd values 0.1-0.25 pM, respectively) but with lower affinity to Kv1.6 channels (Kd 9.6 pM), and it does not interact with either Kv1.4 or Kv1.5 channels. Several subpopulations of native Kv1 subunit oligomers that contribute to the rat brain HgTX1 receptor have been deduced by immunoprecipitation experiments using antibodies specific for Kv1 subunits. HgTX1 represents a novel and useful tool with which to investigate subclasses of voltage-gated K+ channels and Kv1 subunit assembly in different tissues.
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Affiliation(s)
- A Koschak
- Institute for Biochemical Pharmacology, University of Innsbruck, Peter-Mayr Strasse 1, A-6020 Innsbruck, Austria
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Abstract
The discovery of a diverse and unique subset of ion channels in T lymphocytes has led to a rapidly growing body of knowledge about their functional roles in the immune system. Potent and specific blockers have provided molecular tools to probe channel structure-function relations and to elucidate the involvement of K+, Ca2+, and Cl- channels in T-cell activation and cell volume regulation. Recent advances in analyzing Kv1.3 channel structure-function relationships have defined binding sites for channel blockers, which have now been shown to be effective in suppressing T-cell function in vivo. Ion channels may provide excellent pharmaceutical targets for modulating immune system function.
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Affiliation(s)
- M D Cahalan
- Department of Physiology and Biophysics, University of California, Irvine 92697-4560, USA.
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Koch RO, Wanner SG, Koschak A, Hanner M, Schwarzer C, Kaczorowski GJ, Slaughter RS, Garcia ML, Knaus HG. Complex subunit assembly of neuronal voltage-gated K+ channels. Basis for high-affinity toxin interactions and pharmacology. J Biol Chem 1997; 272:27577-81. [PMID: 9346893 DOI: 10.1074/jbc.272.44.27577] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Neurons require specific patterns of K+ channel subunit expression as well as the precise coassembly of channel subunits into heterotetrameric structures for proper integration and transmission of electrical signals. In vivo subunit coassembly was investigated by studying the pharmacological profile, distribution, and subunit composition of voltage-gated Shaker family K+ (Kv1) channels in rat cerebellum that are labeled by 125I-margatoxin (125I-MgTX; Kd, 0.08 pM). High-resolution receptor autoradiography showed spatial receptor expression mainly in basket cell terminals (52% of all cerebellar sites) and the molecular layer (39% of sites). Sequence-directed antibodies indicated overlapping expression of Kv1. 1 and Kv1.2 in basket cell terminals, whereas the molecular layer expressed Kv1.1, Kv1.2, Kv1.3, and Kv1.6 proteins. Immunoprecipitation experiments revealed that all 125I-MgTX receptors contain at least one Kv1.2 subunit and that 83% of these receptors are heterotetramers of Kv1.1 and Kv1.2 subunits. Moreover, 33% of these Kv1.1/Kv1.2-containing receptors possess either an additional Kv1.3 or Kv1.6 subunit. Only a minority of the 125I-MgTX receptors (<20%) seem to be homotetrameric Kv1.2 channels. Heterologous coexpression of Kv1.1 and Kv1.2 subunits in COS-1 cells leads to the formation of a complex that combines the pharmacological profile of both parent subunits, reconstituting the native MgTX receptor phenotype. Subunit assembly provides the structural basis for toxin binding pharmacology and can lead to the association of as many as three distinct channel subunits to form functional K+ channels in vivo.
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Affiliation(s)
- R O Koch
- Institute for Biochemical Pharmacology, Neuropharmacology Unit, University Innsbruck, Peter-Mayr Strasse 1, A-6020 Innsbruck, Austria
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