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Debra Ann Fadool - One of the best experts on this subject based on the ideXlab platform.
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Long‐term obesogenic diet and targeted deletion of Potassium Channel Kv1.3 have differing effects on voluntary exercise in mice
Physiological Reports, 2019Co-Authors: Brandon M Chelette, Abigail M. Thomas, Debra Ann FadoolAbstract:Voluntary exercise is frequently employed as an intervention for obesity. The voltage‐gated Potassium Channel Kv1.3 is also receiving attention as a therapeutic target for obesity, in addition to potential therapeutic capabilities for neuroinflammatory diseases. To investigate the combinatorial effects of these two therapies, we have compared the metabolic status and voluntary exercise behavior of both wild‐type mice and a transgenic line of mice that are genetic knockouts for Kv1.3 when provided with a running wheel and maintained on diets of differing fat content and caloric density. We tracked the metabolic parameters and wheel running behavior while maintaining the mice on their assigned treatment for 6 months. Wild‐type mice maintained on the fatty diet gain a significant amount of bodyweight and adipose tissue and display significantly impaired glucose tolerance, though all these effects were partially reduced with provision of a running wheel. Similar to previous studies, the Kv1.3‐null mice were resistant to obesity, increased adiposity, and impaired glucose tolerance. Both wild‐type and Kv1.3‐null mice maintained on the fatty diet displayed increased wheel running activity compared to control‐fed mice, which was caused primarily by a significant increase in the amount of time spent running as opposed to an increase in running velocity. Interestingly, the patterns of running behavior differed between wild‐type and Kv1.3‐null mice. Kv1.3‐null mice spent significantly less time running during the light phase and displayed a decrease in running 1–2 h before the onset of the light phase, seemingly in anticipation of the dark‐to‐light phase transition. These studies indicate that voluntary exercise combats metabolic maladies and running behavior is modified by both consumption of an obesogenic diet and deletion of the Kv1.3 Channel.
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long term obesogenic diet and targeted deletion of Potassium Channel Kv1.3 have differing effects on voluntary exercise in mice
Physiological Reports, 2019Co-Authors: Brandon M Chelette, Abigail Thomas, Debra Ann FadoolAbstract:Voluntary exercise is frequently employed as an intervention for obesity. The voltage‐gated Potassium Channel Kv1.3 is also receiving attention as a therapeutic target for obesity, in addition to potential therapeutic capabilities for neuroinflammatory diseases. To investigate the combinatorial effects of these two therapies, we have compared the metabolic status and voluntary exercise behavior of both wild‐type mice and a transgenic line of mice that are genetic knockouts for Kv1.3 when provided with a running wheel and maintained on diets of differing fat content and caloric density. We tracked the metabolic parameters and wheel running behavior while maintaining the mice on their assigned treatment for 6 months. Wild‐type mice maintained on the fatty diet gain a significant amount of bodyweight and adipose tissue and display significantly impaired glucose tolerance, though all these effects were partially reduced with provision of a running wheel. Similar to previous studies, the Kv1.3‐null mice were resistant to obesity, increased adiposity, and impaired glucose tolerance. Both wild‐type and Kv1.3‐null mice maintained on the fatty diet displayed increased wheel running activity compared to control‐fed mice, which was caused primarily by a significant increase in the amount of time spent running as opposed to an increase in running velocity. Interestingly, the patterns of running behavior differed between wild‐type and Kv1.3‐null mice. Kv1.3‐null mice spent significantly less time running during the light phase and displayed a decrease in running 1–2 h before the onset of the light phase, seemingly in anticipation of the dark‐to‐light phase transition. These studies indicate that voluntary exercise combats metabolic maladies and running behavior is modified by both consumption of an obesogenic diet and deletion of the Kv1.3 Channel.
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Obesogenic diet and targeted deletion of Potassium Channel Kv1.3 have differing effects on voluntary exercise in mice.
bioRxiv, 2019Co-Authors: Brandon M Chelette, Abigail M. Thomas, Debra Ann FadoolAbstract:Voluntary exercise is frequently employed as an intervention for obesity. The voltage-gated Potassium Kv1.3 is also receiving attention as a therapeutic target for obesity, in addition to potential therapeutic capabilities for neuroinflammatory diseases. To investigate combinatorial effects of these two therapies, we have compared the metabolic status and voluntary exercise behavior of both wildtype mice and a transgenic line of mice that are genetic knockouts for Kv1.3 when provided with a running wheel and maintained on diets of differing fat content and caloric density. We tracked metabolic parameters and wheel running behavior while maintaining the mice on their assigned treatment for 6 months. Wildtype mice maintained on the fatty diet gain a significant amount of bodyweight and adipose tissue and display significantly impaired glucose tolerance, though all these effects were partially reduced with provision of a running wheel. Similarly to previous studies, the Kv1.3-null mice were resistant to obesity, increased adiposity, and impaired glucose tolerance. Both wildtype and Kv1.3-null mice maintained on the fatty diet displayed increased wheel running activity compared to CF-fed mice which was caused primarily by a significant increase in amount of time spent running as opposed to an increase in running velocity. Interestingly, the patterns of running behavior differ between wildtype and Kv1.3-null mice, especially in how their resting periods are distributed through the dark phase. These studies indicate that voluntary exercise combats metabolic maladies and running behavior is modified by both consumption of an obesogenic diet and deletion of the Kv1.3 Channel.nnNEW and NOTEWORTHYO_LIKv1.3-null mice exhibit different running and resting patterns compared to wildtype micenC_LIO_LIMice maintained on an obesogenic diet (32% kcal from fat) exhibit increased running distance and increased time spent running compared to mice fed normal rodent chow.nC_LI
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Glucose sensitivity of mouse olfactory bulb neurons is conveyed by a voltage-gated Potassium Channel
The Journal of Physiology, 2013Co-Authors: Kristal R. Tucker, Nicolas Thiebaud, Michael X. Henderson, Debra Ann FadoolAbstract:metabolism. • Mice with gene-targeted deletion of the Potassium Channel Kv1.3, a Channel regulating action potentialspikefrequencyintheolfactorybulb,are‘super-smellers’andresistanttodiet-induced obesity. • ElectrophysiologyexperimentsdemonstratethatKv1.3issensitivetotheactiveformofglucose and that Kv1.3-expressing mitral neurons of the olfactory bulb are predominantly inhibited by a change to high glucose concentration. • Modulation of the neuron target properties of spike firing rather than action potential shape involves synaptic activity of glutamate or GABA signalling circuits, and is dependent upon Kv1.3 expression. • Giventherisingincidenceofmetabolicdisordersattributedtoweightgain,changesinneuronal excitability in brain regions regulating sensory perception of food are of consequence if we are to understand the function of the brain under chronic hyperglycaemia as is typical with obesity.
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The Olfactory Bulb: A Metabolic Sensor of Brain Insulin and Glucose Concentrations via a Voltage-Gated Potassium Channel
Results and problems in cell differentiation, 2010Co-Authors: Kristal R. Tucker, Melissa Ann Cavallin, K.c. Biju, Patrick Jean-baptiste, J. M. Overton, Paola Pedarzani, Debra Ann FadoolAbstract:The voltage-gated Potassium Channel, Kv1.3, contributes a large proportion of the current in mitral cell neurons of the olfactory bulb where it assists to time the firing patterns of action potentials as spike clusters that are important for odorant detection. Gene-targeted deletion of the Kv1.3 Channel, produces a “super-smeller” phenotype, whereby mice are additionally resistant to diet- and genetically-induced obesity. As assessed via an electrophysiological slice preparation of the olfactory bulb, Kv1.3 is modulated via energetically important molecules – such as insulin and glucose – contributing to the body’s metabolic response to fat intake. We discuss a biophysical characterization of modulated synaptic communication in the slice following acute glucose and insulin stimulation, chronic elevation of insulin in mice that are in a conscious state, and induction of diet-induced obesity. We have discovered that Kv1.3 contributes an unusual nonconducting role – the detection of metabolic state.
Heike Wulff - One of the best experts on this subject based on the ideXlab platform.
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Antibodies and venom peptides: new modalities for ion Channels
Nature Reviews Drug Discovery, 2019Co-Authors: Heike Wulff, Paul Colussi, Palle Christophersen, K G Chandy, Vladimir Yarov-yarovoyAbstract:Ion Channels play fundamental roles in both excitable and non-excitable tissues and therefore constitute attractive drug targets for myriad neurological, cardiovascular and metabolic diseases as well as for cancer and immunomodulation. However, achieving selectivity for specific ion Channel subtypes with small-molecule drugs has been challenging, and there currently is a growing trend to target ion Channels with biologics. One approach is to improve the pharmacokinetics of existing or novel venom-derived peptides. In parallel, after initial studies with polyclonal antibodies demonstrated the technical feasibility of inhibiting Channel function with antibodies, multiple preclinical programmes are now using the full spectrum of available technologies to generate conventional monoclonal and engineered antibodies or nanobodies against extracellular loops of ion Channels. After a summary of the current state of ion Channel drug discovery, this Review discusses recent developments using the purinergic receptor Channel P2X purinoceptor 7 (P2X7), the voltage-gated Potassium Channel Kv1.3 and the voltage-gated sodium Channel NaV1.7 as examples of targeting ion Channels with biologics.Ion Channels are attractive therapeutic targets for a wide range of diseases, but achieving sufficient selectivity with small-molecule drugs can be challenging. In this Review, Wulff and colleagues discuss strategies to selectively modulate ion Channel function using biologics — namely, antibodies and venom-derived peptides — highlighting opportunities, hurdles and future directions for the field.
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The voltage-gated Potassium Channel Kv1.3 is required for microglial pro-inflammatory activation in vivo.
Glia, 2018Co-Authors: Jacopo Di Lucente, Hai M Nguyen, Heike Wulff, Izumi MaezawaAbstract:: 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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Inhibition of the Potassium Channel Kv1.3 reduces infarction and inflammation in ischemic stroke
Annals of clinical and translational neurology, 2017Co-Authors: Yi-je Chen, Hai M Nguyen, Izumi Maezawa, Heike WulffAbstract:Author(s): Chen, Yi-Je; Nguyen, Hai M; Maezawa, Izumi; Jin, Lee-Way; Wulff, Heike | Abstract: Objective:Inhibitors of the voltage-gated K+ Channel Kv1.3 are currently in development as immunomodulators for the treatment of autoimmune diseases. As Kv1.3 is also expressed on microglia and has been shown to be specifically up-regulated on "M1-like" microglia, we here tested the therapeutic hypothesis that the brain-penetrant small-molecule Kv1.3-inhibitor PAP-1 reduces secondary inflammatory damage after ischemia/reperfusion. Methods:We studied microglial Kv1.3 expression using electrophysiology and immunohistochemistry, and evaluated PAP-1 in hypoxia-exposed organotypic hippocampal slices and in middle cerebral artery occlusion (MCAO) with 8 days of reperfusion in both adult male C57BL/6J mice (60 min MCAO) and adult male Wistar rats (90 min MCAO). In both models, PAP-1 administration was started 12 h after reperfusion. Results:We observed Kv1.3 staining on activated microglia in ischemic infarcts in mice, rats, and humans and found higher Kv1.3 current densities in acutely isolated microglia from the infarcted hemisphere than in microglia isolated from the contralateral hemisphere of MCAO mice. PAP-1 reduced microglia activation and increased neuronal survival in hypoxia-exposed hippocampal slices as effectively as minocycline. In mouse MCAO, PAP-1 dose-dependently reduced infarct area, improved neurological deficit score, and reduced brain levels of IL-1β and IFN-γ without affecting IL-10 and brain-derived nerve growth factor (BDNF) levels or inhibiting ongoing phagocytosis. The beneficial effects on infarct area and neurological deficit score were reproduced in rats providing confirmation in a second species. Interpretation:Our findings suggest that Kv1.3 constitutes a promising therapeutic target for preferentially inhibiting "M1-like" inflammatory microglia/macrophage functions in ischemic stroke.
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The Voltage-Gated Potassium Channel Kv1.3 as a Target for Inhibiting Detrimental M1 Microglia Functions
Biophysical Journal, 2016Co-Authors: Yi-je Chen, Hai M Nguyen, Izumi Maezawa, Heike WulffAbstract:Kv1.3 was first discovered in human T cells in 1984 and has since then been pursued as a potential target for immunosuppression. It was later shown to be overexpressed in effector memory T cells, suggesting that Kv1.3 blockers would be particularly useful for the treatment of T cell mediated autoimmune diseases like multiple sclerosis, psoriasis and rheumatoid arthritis. In fact, the Kv1.3 blocking peptide ShK-186 has recently been found to be effective in Phase-1b study for psoriatic arthritis. We hypothesized that Kv1.3 blockers might also be useful for reducing microglia activation in ischemic stroke and other neurological diseases accompanied by neuroinflammation. Starting with cultured microglia, we observed that Kv1.3 expression is up-regulated in pro-inflammatory M1-like microglia and that Kv1.3 blockers preferentially reduce the production of IL-1beta and TNF-alpha without affecting IL-10 production. In organotypic hippocampal slices exposed to hypoxia/aglycemia Kv1.3 blockers significantly reduced microglia activation and increased neuronal survival. We further observed strong Kv1.3 expression on iNOS expressing inflammatory microglia in human stroke biopsies validating Kv1.3 as potential target. In both mouse and rat models of ischemic stroke the small molecule Kv1.3 blocker PAP-1 significantly reduced infarct area and improved neurological deficit 7 days after reperfusion when administered 12 hours after reperfusion. In the mouse model, PAP-1 selectively reduced brain levels of the inflammatory cytokines IL1-beta and IFN-gamma without affecting IL-10 and BDNF. Based on these findings we propose Kv1.3 inhibitors as potential therapeutic agents for preferentially inhibiting pro-inflammatory M1 microglia functions in ischemic stroke and other neurological diseases.Supported by GM076063 and AG043788.
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Spiro azepane-oxazolidinones as Kv1.3 Potassium Channel blockers: WO2010066840.
Expert Opinion on Therapeutic Patents, 2010Co-Authors: Heike WulffAbstract:This article evaluates a patent application from Solvay Pharmaceuticals, which claims spiro azepane-oxazolidinones as novel blockers of the voltage-gated Potassium Channel Kv1.3 for the treatment of diabetes, psoriasis, obesity, transplant rejection and T-cell mediated autoimmune diseases such as rheumatoid arthritis and MS. The patent describes a new chemotype of Kv1.3 blockers and thus illustrates the growing interest of the pharmaceutical industry in Kv1.3 as a target of immunosuppression and metabolic disorders. This article briefly summarizes the chemistry and biological data provided in the patent and then compares the new compounds to Kv1.3 blockers previously disclosed by both academia and pharmaceutical companies.
Raymond S Norton - One of the best experts on this subject based on the ideXlab platform.
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The voltage-gated Potassium Channel Kv1.3 as a therapeutic target for venom-derived peptides.
Biochemical pharmacology, 2020Co-Authors: Gabor Tajti, Gyorgy Panyi, Raymond S NortonAbstract:The voltage-gated Potassium Channel Kv1.3 is a well-established therapeutic target for a range of autoimmune diseases, in addition to being the site of action of many venom-derived peptides. Numerous studies have documented the efficacy of venom peptides that target Kv1.3, in particular from sea anemones and scorpions, in animal models of autoimmune diseases such as rheumatoid arthritis, psoriasis and multiple sclerosis. Moreover, an analogue of the sea anemone peptide ShK (known as dalazatide) has successfully completed Phase 1 clinical trials in mild-to-moderate plaque psoriasis. In this article we consider other potential therapeutic applications of inhibitors of Kv1.3, including in inflammatory bowel disease and neuroinflammatory conditions such as Alzheimer's and Parkinson's diseases, as well as fibrotic diseases. We also summarise strategies for facilitating the entry of peptides to the central nervous system, given that this will be a pre-requisite for the treatment of most neuroinflammatory diseases. Venom-derived peptides that have been reported recently to target Kv1.3 are also described. The increasing number of autoimmune and other conditions in which Kv1.3 is upregulated and is therefore a potential therapeutic target, combined with the fact that many venom-derived peptides are potent inhibitors of Kv1.3, suggests that venoms are likely to continue to serve as a rich source of new pharmacological tools and therapeutic leads targeting this Channel.
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Distribution and kinetics of the Kv1.3-blocking peptide HsTX1[R14A] in experimental rats.
Scientific Reports, 2017Co-Authors: Ralf Bergmann, Raymond S Norton, Michael W. Pennington, Sandeep Chhabra, Christine Beeton, Manja Kubeil, Kristof Zarschler, Rajeev B. Tajhya, Michael H. Bachmann, Holger StephanAbstract:The peptide HsTX1[R14A] is a potent and selective blocker of the voltage-gated Potassium Channel Kv1.3, which is a highly promising target for the treatment of autoimmune diseases and other conditions. In order to assess the biodistribution of this peptide, it was conjugated with NOTA and radiolabelled with copper-64. [64Cu]Cu-NOTA-HsTX1[R14A] was synthesised in high radiochemical purity and yield. The radiotracer was evaluated in vitro and in vivo. The biodistribution and PET studies after intravenous and subcutaneous injections showed similar patterns and kinetics. The hydrophilic peptide was rapidly distributed, showed low accumulation in most of the organs and tissues, and demonstrated high molecular stability in vitro and in vivo. The most prominent accumulation occurred in the epiphyseal plates of trabecular bones. The high stability and bioavailability, low normal-tissue uptake of [64Cu]Cu-NOTA-HsTX1[R14A], and accumulation in regions of up-regulated Kv Channels both in vitro and in vivo demonstrate that HsTX1[R14A] represents a valuable lead for conditions treatable by blockade of the voltage-gated Potassium Channel Kv1.3. The pharmacokinetics shows that both intravenous and subcutaneous applications are viable routes for the delivery of this potent peptide.
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N-Terminally extended analogues of the K⁺ Channel toxin from Stichodactyla helianthus as potent and selective blockers of the voltage-gated Potassium Channel Kv1.3.
FEBS Journal, 2015Co-Authors: Shih Chieh Chang, Brian J Smith, Michael W. Pennington, Sandeep Chhabra, Christine Beeton, Raymond S NortonAbstract:The voltage-gated Potassium Channel Kv1.3 is an important target for the treatment of autoimmune diseases and asthma. Blockade of Kv1.3 by the sea anemone peptide K+-Channel toxin from Stichodactyla helianthus (ShK) inhibits the proliferation of effector memory T lymphocytes and ameliorates autoimmune diseases in animal models. However, the lack of selectivity of ShK for Kv1.3 over the Kv1.1 subtype has driven a search for Kv1.3-selective analogues. In the present study, we describe N-terminally extended analogues of ShK that contain a negatively-charged Glu, designed to mimic the phosphonate adduct in earlier Kv1.3-selective analogues, and consist entirely of common protein amino acids. Molecular dynamics simulations indicated that a Trp residue at position [-3] of the tetrapeptide extension could form stable interactions with Pro377 of Kv1.3 and best discriminates between Kv1.3 and Kv1.1. This led to the development of ShK with an N-terminal Glu-Trp-Ser-Ser extension ([EWSS]ShK), which inhibits Kv1.3 with an IC50 of 34 pm and is 158-fold selective for Kv1.3 over Kv1.1. In addition, [EWSS]ShK is more than 2900-fold more selective for Kv1.3 over Kv1.2 and KCa3.1 Channels. As a highly Kv1.3-selective analogue of ShK based entirely on protein amino acids, which can be produced by recombinant expression, this peptide is a valuable addition to the complement of therapeutic candidates for the treatment of autoimmune diseases.
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Computational approaches for designing potent and selective analogs of peptide toxins as novel therapeutics
Future Medicinal Chemistry, 2014Co-Authors: Serdar Kuyucak, Raymond S NortonAbstract:Peptide toxins provide valuable therapeutic leads for many diseases. As they bind to their targets with high affinity, potency is usually ensured. However, toxins also bind to off-target receptors, causing potential side effects. Thus, a major challenge in generating drugs from peptide toxins is ensuring their specificity for their intended targets. Computational methods can play an important role in solving such design problems through construction of accurate models of receptor–toxin complexes and calculation of binding free energies. Here we review the computational methods used for this purpose and their application to toxins targeting ion Channels. We describe ShK and HsTX1 toxins, high-affinity blockers of the voltage-gated Potassium Channel Kv1.3, which could be developed as therapeutic agents for autoimmune diseases.
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intracellular trafficking of the Kv1.3 Potassium Channel is regulated by the prodomain of a matrix metalloprotease
Journal of Biological Chemistry, 2013Co-Authors: Hai M Nguyen, Charles A Galea, Galina Schmunk, Brian J Smith, Robert Edwards, Raymond S Norton, George K ChandyAbstract:Matrix metalloproteases (MMPs) are endopeptidases that regulate diverse biological processes. Synthesized as zymogens, MMPs become active after removal of their prodomains. Much is known about the metalloprotease activity of these enzymes, but noncanonical functions are poorly defined, and functions of the prodomains have been largely ignored. Here we report a novel metalloprotease-independent, Channel-modulating function for the prodomain of MMP23 (MMP23-PD). Whole-cell patch clamping and confocal microscopy, coupled with deletion analysis, demonstrate that MMP23-PD suppresses the voltage-gated Potassium Channel Kv1.3, but not the closely related KV1.2 Channel, by trapping the Channel intracellularly. Studies with KV1.2-1.3 chimeras suggest that MMP23-PD requires the presence of the Kv1.3 region from the S5 trans-membrane segment to the C terminus to modulate Kv1.3 Channel function. NMR studies of MMP23-PD reveal a single, kinked trans-membrane α-helix, joined by a short linker to a juxtamembrane α-helix, which is associated with the surface of the membrane and protected from exchange with the solvent. The topological similarity of MMP23-PD to KCNE1, KCNE2, and KCNE4 proteins that trap Kv1.3, KV1.4, KV3.3, and KV3.4 Channels early in the secretory pathway suggests a shared mechanism of Channel regulation. MMP23 and Kv1.3 expression is enhanced and overlapping in colorectal cancers where the interaction of the two proteins could affect cell function.
John P. Felix - One of the best experts on this subject based on the ideXlab platform.
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Di-substituted cyclohexyl derivatives bind to two identical sites with positive cooperativity on the voltage-gated Potassium Channel, Kv1.3
Biochemistry, 2003Co-Authors: William A. Schmalhofer, John P. Felix, Robert S. Slaughter, Mary Matyskiela, Yui S. Tang, Kathleen M. Rupprecht, Gregory J. Kaczorowski, Maria L. GarciaAbstract:Di-substituted cyclohexyl (DSC) derivatives inhibit the voltage-gated Potassium Channel, Kv1.3, and have immunosuppressant activity (Schmalhofer et al. (2002) Biochemistry 41, 7781−7794). This class of inhibitors displays Hill coefficients of near 2 in functional assays, and trans DSC analogues appear to selectively interact with Kv1.3 Channel conformations related to C-type inactivation. To further understand the details of the DSC inhibitor interaction with Potassium Channels, trans-1-(N-n-propylcarbamoyloxy)-4-phenyl-4-(3-(2-methoxyphenyl)-3-oxo-2-azaprop-1-yl)cyclo-hexane (trans-NPCO-DSC) was radiolabeled with tritium, and its binding characteristics to Kv1.3 Channels were determined. Specific binding of [3H]-trans-NPCO-DSC to Kv1.3 Channels is a saturable, time-dependent, and fully reversible process. Saturation binding isotherms and competition binding experiments are consistent with the presence of two receptor sites for DSC derivatives on the Kv1.3 Channel that display positive allosteric cooperat...
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Identification of a New Class of Inhibitors of the Voltage-Gated Potassium Channel, Kv1.3, with Immunosuppressant Properties†
Biochemistry, 2002Co-Authors: William A. Schmalhofer, John P. Felix, Mary Matyskiela, Markus Hanner, Brian N. Green, Randal M. Bugianesi, Owen B. Mcmanus, Denise Wunderler, Ana-rosa Linde-ariasAbstract:The voltage-gated Potassium Channel, K v 1.3, is a novel target for development of immunosuppressants. Using a functional 8 6 Rb + efflux assay, a new class of high-affinity K v 1.3 inhibitors has been identified. The initial active in this series, 4-phenyl-4-[3-(2-methoxyphenyl)-3-oxo-2-azaprop1-yl]cyclohexanone (PAC), which is representative of a disubstituted cyclohexyl (DSC) template, displays a K i of ca. 300 nM and a Hill coefficient near 2 in the flux assay and in voltage clamp recordings of K v 1.3 Channels in human T-lymphocytes. PAC displays excellent specificity as it only blocks members of the K v 1 family of Potassium Channels but does not affect many other types of ion Channels, receptors, or enzyme systems. Block of K v 1.3 by DSC analogues occurs with a well-defined structure-activity relationship. Substitution at the C-1 ketone of PAC generates trans (down) and cis (up) isomer pairs. Whereas many DSC derivatives do not display selectivity in their interaction with different K v 1. x Channels, trans DSC derivatives distinguish between K v 1.x Channels based on their rates of C-type inactivation. DSC analogues reversibly inhibit the Ca 2 + -dependent pathway of T cell activation in in vitro assays. Together, these data suggest that DSC derivatives represent a new class of immunosuppressant agents and that specific interactions of trans DSC analogues with Channel conformations related to C-type inactivation may permit development of selective K v 1.3 Channel inhibitors useful for the safe treatment of autoimmune diseases.
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Binding of Correolide to the Kv1.3 Potassium Channel: Characterization of the Binding Domain by Site-Directed Mutagenesis†
Biochemistry, 2001Co-Authors: Markus Hanner, John P. Felix, William A. Schmalhofer, Mary Matyskiela, Brian N. Green, Daniel J. Durand, Ana-rosa Linde, Carmen Bordallo, Gregory J. KaczorowskiAbstract:Correolide is a novel immunosuppressant that inhibits the voltage-gated Potassium Channel Kv1.3 [Felix et al. (1999) Biochemistry 38, 4922−4930]. [3H]Dihydrocorreolide (diTC) binds with high affini...
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Diterpenoid pyrones, novel blockers of the voltage-gated Potassium Channel Kv1.3 from fungal fermentations
Tetrahedron Letters, 2001Co-Authors: Michael A. Goetz, Deborah L. Zink, Gabe Dezeny, Anne W. Dombrowski, Jon D. Polishook, John P. Felix, Robert S. Slaughter, Sheo B. SinghAbstract:Abstract The isolation, structure elucidation and chemical modification of nalanthalide, a novel diterpenoid pyrone blocker of the voltage-gated Potassium Channel Kv1.3 are reported. The structure–activity relationship of the derivatives with respect to various associated biological activities is also discussed.
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Candelalides A-C: novel diterpenoid pyrones from fermentations of Sesquicillium candelabrum as blockers of the voltage-gated Potassium Channel Kv1.3.
Organic Letters, 2001Co-Authors: Sheo B. Singh, Deborah L. Zink, Gabe Dezeny, Anne W. Dombrowski, John P. Felix, Robert S. Slaughter, Gerald F. Bills, Michael A. GoetzAbstract:Blockers of the voltage-gated Potassium Channel Kv1.3 are potential immunosuppressants. Candelalides A−C are three novel diterpenoid pyrones that block this Channel. The structure, stereochemistry, and activity against Kv1.3 are described.
Debra A Fadool - One of the best experts on this subject based on the ideXlab platform.
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Brain-derived neurotrophic factor modulation of Kv1.3 Channel is disregulated by adaptor proteins Grb10 and nShc
BMC Neuroscience, 2009Co-Authors: Beverly S. Colley, Melissa Ann Cavallin, K.c. Biju, David R. Marks, Debra A FadoolAbstract:Background Neurotrophins are important regulators of growth and regeneration, and acutely, they can modulate the activity of voltage-gated ion Channels. Previously we have shown that acute brain-derived neurotrophic factor (BDNF) activation of neurotrophin receptor tyrosine kinase B (TrkB) suppresses the Shaker voltage-gated Potassium Channel (Kv1.3) via phosphorylation of multiple tyrosine residues in the N and C terminal aspects of the Channel protein. It is not known how adaptor proteins, which lack catalytic activity, but interact with members of the neurotrophic signaling pathway, might scaffold with ion Channels or modulate Channel activity. Results We report the co-localization of two adaptor proteins, neuronal Src homology and collagen (nShc) and growth factor receptor-binding protein 10 (Grb10), with Kv1.3 Channel as demonstrated through immunocytochemical approaches in the olfactory bulb (OB) neural lamina. To further explore the specificity and functional ramification of adaptor/Channel co-localization, we performed immunoprecipitation and Western analysis of Channel, kinase, and adaptor transfected human embryonic kidney 293 cells (HEK 293). nShc formed a direct protein-protein interaction with Kv1.3 that was independent of BDNF-induced phosphorylation of Kv1.3, whereas Grb10 did not complex with Kv1.3 in HEK 293 cells. Both adaptors, however, co-immunoprecipitated with Kv1.3 in native OB. Grb10 was interestingly able to decrease the total expression of Kv1.3, particularly at the membrane surface, and subsequently eliminated the BDNF-induced phosphorylation of Kv1.3. To examine the possibility that the Src homology 2 (SH2) domains of Grb10 were directly binding to basally phosphorylated tyrosines in Kv1.3, we utilized point mutations to substitute multiple tyrosine residues with phenylalanine. Removal of the tyrosines 111–113 and 449 prevented Grb10 from decreasing Kv1.3 expression. In the absence of either adaptor protein, Channel co-expression reciprocally down-regulated expression and tyrosine phosphorylation of TrkB kinase and related insulin receptor kinase. Finally, through patch-clamp electrophysiology, we found that the BDNF-induced current suppression of the Channel was prevented by both nShc and Grb10. Conclusion We report that adaptor protein alteration of kinase-induced Kv1.3 Channel modulation is related to the degree of direct protein-protein association and that the Channel itself can reciprocally modulate receptor-linked tyrosine kinase expression and activity.