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Yuan T, Wang Y, Jin Y, Yang H, Xu S, Zhang H, Chen Q, Li N, Ma X, Song H, Peng C, Geng Z, Dong J, Duan G, Sun Q, Yang Y, Yang F, Huang Z. Coupling of Slack and Na V1.6 sensitizes Slack to quinidine blockade and guides anti-seizure strategy development. eLife 2024; 12:RP87559. [PMID: 38289338 PMCID: PMC10942592 DOI: 10.7554/elife.87559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024] Open
Abstract
Quinidine has been used as an anticonvulsant to treat patients with KCNT1-related epilepsy by targeting gain-of-function KCNT1 pathogenic mutant variants. However, the detailed mechanism underlying quinidine's blockade against KCNT1 (Slack) remains elusive. Here, we report a functional and physical coupling of the voltage-gated sodium channel NaV1.6 and Slack. NaV1.6 binds to and highly sensitizes Slack to quinidine blockade. Homozygous knockout of NaV1.6 reduces the sensitivity of native sodium-activated potassium currents to quinidine blockade. NaV1.6-mediated sensitization requires the involvement of NaV1.6's N- and C-termini binding to Slack's C-terminus and is enhanced by transient sodium influx through NaV1.6. Moreover, disrupting the Slack-NaV1.6 interaction by viral expression of Slack's C-terminus can protect against SlackG269S-induced seizures in mice. These insights about a Slack-NaV1.6 complex challenge the traditional view of 'Slack as an isolated target' for anti-epileptic drug discovery efforts and can guide the development of innovative therapeutic strategies for KCNT1-related epilepsy.
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Affiliation(s)
- Tian Yuan
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Yifan Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Yuchen Jin
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Hui Yang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Shuai Xu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Heng Zhang
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang UniversityZhejiangChina
| | - Qian Chen
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Na Li
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Xinyue Ma
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Huifang Song
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Chao Peng
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Ze Geng
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Jie Dong
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Guifang Duan
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Qi Sun
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
| | - Yang Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue UniversityWest LafayetteUnited States
| | - Fan Yang
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang UniversityZhejiangChina
- Department of Biophysics, Kidney Disease Center of the First Affiliated Hospital, Zhejiang University School of Medicine, HangzhouZhejiangChina
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science CenterBeijingChina
- IDG/McGovern Institute for Brain Research, Peking UniversityBeijingChina
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Qunies AM, Spitznagel BD, Du Y, David Weaver C, Emmitte KA. Design, synthesis, and biological evaluation of a novel series of 1,2,4-oxadiazole inhibitors of SLACK potassium channels: Identification of in vitro tool VU0935685. Bioorg Med Chem 2023; 95:117487. [PMID: 37812884 PMCID: PMC10842602 DOI: 10.1016/j.bmc.2023.117487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 09/28/2023] [Accepted: 09/29/2023] [Indexed: 10/11/2023]
Abstract
Malignant migrating partial seizure of infancy (MMPSI) is a devastating and pharmacoresistant form of infantile epilepsy. MMPSI has been linked to multiple gain-of-function (GOF) mutations in the KCNT1 gene, which encodes for a potassium channel often referred to as SLACK. SLACK channels are sodium-activated potassium channels distributed throughout the central nervous system (CNS) and the periphery. The investigation described here aims to discover SLACK channel inhibitor tool compounds and profile their pharmacokinetic and pharmacodynamic properties. A SLACK channel inhibitor VU0531245 (VU245) was identified via a high-throughput screen (HTS) campaign. Structure-activity relationship (SAR) studies were conducted in five distinct regions of the hit VU245. VU245 analogs were evaluated for their ability to affect SLACK channel activity using a thallium flux assay in HEK-293 cells stably expressing wild-type (WT) human SLACK. Selected analogs were tested for metabolic stability in mouse liver microsomes and plasma-protein binding in mouse plasma. The same set of analogs was tested via thallium flux for activity versus human A934T SLACK and other structurally related potassium channels, including SLICK and Maxi-K. In addition, potencies for selected VU245 analogs were obtained using whole-cell electrophysiology (EP) assays in CHO cells stably expressing WT human SLACK through an automated patch clamp system. Results revealed that this scaffold tolerates structural changes in some regions, with some analogs demonstrating improved SLACK inhibitory activity, good selectivity against the other channels tested, and modest improvements in metabolic clearance. Analog VU0935685 represents a new, structurally distinct small-molecule inhibitor of SLACK channels that can serve as an in vitro tool for studying this target.
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Affiliation(s)
- Alshaima'a M Qunies
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | | | - Yu Du
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - C David Weaver
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Kyle A Emmitte
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
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Shore AN, Qunies AM, Spitznagel BD, Weaver CD, Emmitte KA, Frankel WN, Weston MC. Heterozygous expression of a Kcnt1 gain-of-function variant has differential effects on SST- and PV-expressing cortical GABAergic neurons. bioRxiv 2023:2023.10.11.561953. [PMID: 37873369 PMCID: PMC10592778 DOI: 10.1101/2023.10.11.561953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
More than twenty recurrent missense gain-of-function (GOF) mutations have been identified in the sodium-activated potassium (KNa) channel gene KCNT1 in patients with severe developmental and epileptic encephalopathies (DEEs), most of which are resistant to current therapies. Defining the neuron types most vulnerable to KCNT1 GOF will advance our understanding of disease mechanisms and provide refined targets for precision therapy efforts. Here, we assessed the effects of heterozygous expression of a Kcnt1 GOF variant (Y777H) on KNa currents and neuronal physiology among cortical glutamatergic and GABAergic neurons in mice, including those expressing vasoactive intestinal polypeptide (VIP), somatostatin (SST), and parvalbumin (PV), to identify and model the pathogenic mechanisms of autosomal dominant KCNT1 GOF variants in DEEs. Although the Kcnt1-Y777H variant had no effects on glutamatergic or VIP neuron function, it increased subthreshold KNa currents in both SST and PV neurons but with opposite effects on neuronal output; SST neurons became hypoexcitable with a higher rheobase current and lower action potential (AP) firing frequency, whereas PV neurons became hyperexcitable with a lower rheobase current and higher AP firing frequency. Further neurophysiological and computational modeling experiments showed that the differential effects of the Y777H variant on SST and PV neurons are not likely due to inherent differences in these neuron types, but to an increased persistent sodium current in PV, but not SST, neurons. The Y777H variant also increased excitatory input onto, and chemical and electrical synaptic connectivity between, SST neurons. Together, these data suggest differential pathogenic mechanisms, both direct and compensatory, contribute to disease phenotypes, and provide a salient example of how a pathogenic ion channel variant can cause opposite functional effects in closely related neuron subtypes due to interactions with other ionic conductances.
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Affiliation(s)
- Amy N. Shore
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
- Department of Neurological Sciences, University of Vermont, Burlington, VT, USA
| | - Alshaima’a M. Qunies
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
- School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Brittany D. Spitznagel
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA
| | - C. David Weaver
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA
| | - Kyle A. Emmitte
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Wayne N. Frankel
- Institute for Genomic Medicine, Columbia University, New York, NY, USA
- Department of Neurology, Columbia University, New York, NY, USA
| | - Matthew C. Weston
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
- Department of Neurological Sciences, University of Vermont, Burlington, VT, USA
- School of Neuroscience, Virginia Tech, Blacksburg, VA, USA
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Marczyk CES, Saurin TA, Bulhões IR, Patriarca R, Bilotta F. Slack in the infrastructure of intensive care units: resilience management in the post-pandemic era. BMC Health Serv Res 2023; 23:579. [PMID: 37277870 DOI: 10.1186/s12913-023-09495-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/03/2023] [Indexed: 06/07/2023] Open
Abstract
BACKGROUND Although slack is an asset to resilient hospitals, it is usually explicitly discussed only in terms of the quantity and quality of beds and staff. This paper expands this view by addressing slack in four infrastructures of intensive care units (ICUs) (physical space, electricity supply, oxygen supply, and air treatment) during the COVID pandemic. METHODS The study occurred in a leading private hospital in Brazil, aiming at the identification of slack in four units originally designed as ICUs and two units adapted as ICUs. Data collection was based on 12 interviews with healthcare professionals, documents, and comparison between infrastructures and regulatory requirements. RESULTS Twenty-seven instantiations of slack were identified, with several indications that the adapted ICUs did not provide infrastructure conditions as good as the designed ones. Findings gave rise to five propositions addressing: relationships intra and inter infrastructures; the need for adapted ICUs that match as closely as possible the designed ICUs; the consideration of both clinical and engineering perspectives in design; and the need for the revision of some requirements of the Brazilian regulations. CONCLUSIONS Results are relevant to both the designers of the infrastructures and to the designers of clinical activities as these must take place in fit-for-purpose workspaces. Top management might also benefit as they are the ultimate responsible for decision-making on whether or not to invest in slack. The pandemic dramatically demonstrated the value of investing in slack resources, creating momentum for this discussion in health services.
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Affiliation(s)
- Carlos Emilio Stigler Marczyk
- Construction and Infrastructure Post-Graduate Program, Universidade Federal do Rio Grande do Sul, Av. Osvaldo Aranha, 99, Porto Alegre, CEP 90035-190, Brazil
| | - Tarcisio Abreu Saurin
- Industrial Engineering Post-Graduate Program, Universidade Federal do Rio Grande do Sul, Av. Osvaldo Aranha, 99, Porto Alegre, CEP 90035-190, Brazil.
| | - Iamara Rossi Bulhões
- Construction and Infrastructure Post-Graduate Program, Universidade Federal do Rio Grande do Sul, Av. Osvaldo Aranha, 99, Porto Alegre, CEP 90035-190, Brazil
| | - Riccardo Patriarca
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Via Eudossiana 18, Rome, 00184, Italy
| | - Federico Bilotta
- Department of Anesthesiology, Critical Care and Pain Medicine, Sapienza University of Rome, Via Eudossiana 18, Rome, 00184, Italy
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Qunies AM, Mishra NM, Spitznagel BD, Du Y, Acuña VS, David Weaver C, Emmitte KA. Structure-activity relationship studies in a new series of 2-amino-N-phenylacetamide inhibitors of Slack potassium channels. Bioorg Med Chem Lett 2022; 76:129013. [PMID: 36184030 PMCID: PMC10230575 DOI: 10.1016/j.bmcl.2022.129013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/20/2022] [Accepted: 09/26/2022] [Indexed: 11/02/2022]
Abstract
In this Letter we describe structure-activity relationship (SAR) studies conducted in five distinct regions of a new 2-amino-N-phenylacetamides series of Slack potassium channel inhibitors exemplified by recently disclosed high-throughput screening (HTS) hit VU0606170 (4). New analogs were screened in a thallium (Tl+) flux assay in HEK-293 cells stably expressing wild-type human (WT) Slack. Selected analogs were screened in Tl+ flux versus A934T Slack and other Slo family members Slick and Maxi-K and evaluated in whole-cell electrophysiology (EP) assays using an automated patch clamp system. Results revealed the series to have flat SAR with significant structural modifications resulting in a loss of Slack activity. More minor changes led to compounds with Slack activity and Slo family selectivity similar to the HTS hit.
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Affiliation(s)
- Alshaima'a M Qunies
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA; Graduate School of Biomedical Sciences, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Nigam M Mishra
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | | | - Yu Du
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Valerie S Acuña
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - C David Weaver
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Kyle A Emmitte
- Department of Pharmaceutical Sciences, UNT System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA.
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M Qunies A, A Emmitte K. Small-molecule inhibitors of Slack potassium channels as potential therapeutics for childhood epilepsies. Pharm Pat Anal 2022; 11:45-56. [PMID: 35369761 DOI: 10.4155/ppa-2022-0002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Slack channels are sodium-activated potassium channels that are encoded by the KCNT1 gene. Several KCNT1 gain of function mutations have been linked to malignant migrating partial seizures of infancy. Quinidine is an anti-arrhythmic drug that functions as a moderately potent inhibitor of Slack channels; however, quinidine use is limited by its poor selectivity, safety and pharmacokinetic profile. Slack channels represent an interesting target for developing novel therapeutics for the treatment of malignant migrating partial seizures of infancy and other childhood epilepsies; thus, ongoing efforts are directed toward the discovery of small-molecules that inhibit Slack currents. This review summarizes patent applications published in 2020-2021 that describe the discovery of novel small-molecule Slack inhibitors.
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Ehinger R, Kuret A, Matt L, Frank N, Wild K, Kabagema-Bilan C, Bischof H, Malli R, Ruth P, Bausch AE, Lukowski R. Slack K + channels attenuate NMDA-induced excitotoxic brain damage and neuronal cell death. FASEB J 2021; 35:e21568. [PMID: 33817875 DOI: 10.1096/fj.202002308rr] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 10/12/2020] [Revised: 03/14/2021] [Accepted: 03/17/2021] [Indexed: 12/13/2022]
Abstract
The neuronal Na+ -activated K+ channel Slack (aka Slo2.2, KNa 1.1, or Kcnt1) has been implicated in setting and maintaining the resting membrane potential and defining excitability and firing patterns, as well as in the generation of the slow afterhyperpolarization following bursts of action potentials. Slack activity increases significantly under conditions of high intracellular Na+ levels, suggesting this channel may exert important pathophysiological functions. To address these putative roles, we studied whether Slack K+ channels contribute to pathological changes and excitotoxic cell death caused by glutamatergic overstimulation of Ca2+ - and Na+ -permeable N-methyl-D-aspartic acid receptors (NMDAR). Slack-deficient (Slack KO) and wild-type (WT) mice were subjected to intrastriatal microinjections of the NMDAR agonist NMDA. NMDA-induced brain lesions were significantly increased in Slack KO vs WT mice, suggesting that the lack of Slack renders neurons particularly susceptible to excitotoxicity. Accordingly, excessive neuronal cell death was seen in Slack-deficient primary cerebellar granule cell (CGC) cultures exposed to glutamate and NMDA. Differences in neuronal survival between WT and Slack KO CGCs were largely abolished by the NMDAR antagonist MK-801, but not by NBQX, a potent and highly selective competitive antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type ionotropic glutamate receptors. Interestingly, NMDAR-evoked Ca2+ signals did not differ with regard to Slack genotype in CGCs. However, real-time monitoring of K+ following NMDAR activation revealed a significant contribution of this channel to the intracellular drop in K+ . Finally, TrkB and TrkC neurotrophin receptor transcript levels were elevated in NMDA-exposed Slack-proficient CGCs, suggesting a mechanism by which this K+ channel contributes to the activation of the extracellular-signal-regulated kinase (Erk) pathway and thereby to neuroprotection. Combined, our findings suggest that Slack-dependent K+ signals oppose the NMDAR-mediated excitotoxic neuronal injury by promoting pro-survival signaling via the BDNF/TrkB and Erk axis.
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Affiliation(s)
- Rebekka Ehinger
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Anna Kuret
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Lucas Matt
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Nadine Frank
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Katharina Wild
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Clement Kabagema-Bilan
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Helmut Bischof
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Roland Malli
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Anne E Bausch
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
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Lu R, Metzner K, Zhou F, Flauaus C, Balzulat A, Engel P, Petersen J, Ehinger R, Bausch A, Ruth P, Lukowski R, Schmidtko A. Functional Coupling of Slack Channels and P2X3 Receptors Contributes to Neuropathic Pain Processing. Int J Mol Sci 2021; 22:E405. [PMID: 33401689 DOI: 10.3390/ijms22010405] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/19/2020] [Accepted: 12/29/2020] [Indexed: 12/16/2022] Open
Abstract
The sodium-activated potassium channel Slack (KNa1.1, Slo2.2, or Kcnt1) is highly expressed in populations of sensory neurons, where it mediates the sodium-activated potassium current (IKNa) and modulates neuronal activity. Previous studies suggest that Slack is involved in the processing of neuropathic pain. However, mechanisms underlying the regulation of Slack activity in this context are poorly understood. Using whole-cell patch-clamp recordings we found that Slack-mediated IKNa in sensory neurons of mice is reduced after peripheral nerve injury, thereby contributing to neuropathic pain hypersensitivity. Interestingly, Slack is closely associated with ATP-sensitive P2X3 receptors in a population of sensory neurons. In vitro experiments revealed that Slack-mediated IKNa may be bidirectionally modulated in response to P2X3 activation. Moreover, mice lacking Slack show altered nocifensive responses to P2X3 stimulation. Our study identifies P2X3/Slack signaling as a mechanism contributing to hypersensitivity after peripheral nerve injury and proposes a potential novel strategy for treatment of neuropathic pain.
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Matt L, Pham T, Skrabak D, Hoffmann F, Eckert P, Yin J, Gisevius M, Ehinger R, Bausch A, Ueffing M, Boldt K, Ruth P, Lukowski R. The Na(+)-activated K(+) channel Slack contributes to synaptic development and plasticity. Cell Mol Life Sci 2021; 78:7569-87. [PMID: 34664085 DOI: 10.1007/s00018-021-03953-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 01/20/2021] [Revised: 09/08/2021] [Accepted: 09/22/2021] [Indexed: 11/29/2022]
Abstract
Human mutations of the Na+-activated K+ channel Slack (KCNT1) are associated with epilepsy and intellectual disability. Accordingly, Slack knockout mice (Slack-/-) exhibit cognitive flexibility deficits in distinct behavioral tasks. So far, however, the underlying causes as well as the role of Slack in hippocampus-dependent memory functions remain enigmatic. We now report that infant (P6-P14) Slack-/- lack both hippocampal LTD and LTP, likely due to impaired NMDA receptor (NMDAR) signaling. Postsynaptic GluN2B levels are reduced in infant Slack-/-, evidenced by lower amplitudes of NMDAR-meditated excitatory postsynaptic potentials. Low GluN2B affected NMDAR-mediated Ca2+-influx, rendering cultured hippocampal Slack-/-neurons highly insensitive to the GluN2B-specific inhibitor Ro 25-6981. Furthermore, dephosphorylation of the AMPA receptor (AMPAR) subunit GluA1 at S845, which is involved in AMPAR endocytosis during homeostatic and neuromodulator-regulated plasticity, is reduced after chemical LTD (cLTD) in infant Slack-/-. We additionally detect a lack of mGluR-induced LTD in infant Slack-/-, possibly caused by upregulation of the recycling endosome-associated small GTPase Rab4 which might accelerate AMPAR recycling from early endosomes. Interestingly, LTP and mGluR LTD, but not LTD and S845 dephosphorylation after cLTD are restored in adult Slack-/-. This together with normalized expression levels of GluN2B and Rab4 hints to developmental "restoration" of LTP expression despite Slack ablation, whereas in infant and adult brain, NMDAR-dependent LTD induction depends on this channel. Based on the present findings, NMDAR and vesicular transport might represent novel targets for the therapy of intellectual disability associated with Slack mutations. Consequently, careful modulation of hippocampal Slack activity should also improve learning abilities.
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10
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Shore AN, Colombo S, Tobin WF, Petri S, Cullen ER, Dominguez S, Bostick CD, Beaumont MA, Williams D, Khodagholy D, Yang M, Lutz CM, Peng Y, Gelinas JN, Goldstein DB, Boland MJ, Frankel WN, Weston MC. Reduced GABAergic Neuron Excitability, Altered Synaptic Connectivity, and Seizures in a KCNT1 Gain-of-Function Mouse Model of Childhood Epilepsy. Cell Rep 2020; 33:108303. [PMID: 33113364 PMCID: PMC7712469 DOI: 10.1016/j.celrep.2020.108303] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 08/06/2020] [Accepted: 10/01/2020] [Indexed: 01/07/2023] Open
Abstract
Gain-of-function (GOF) variants in K+ channels cause severe childhood epilepsies, but there are no mechanisms to explain how increased K+ currents lead to network hyperexcitability. Here, we introduce a human Na+-activated K+ (KNa) channel variant (KCNT1-Y796H) into mice and, using a multiplatform approach, find motor cortex hyperexcitability and early-onset seizures, phenotypes strikingly similar to those of human patients. Although the variant increases KNa currents in cortical excitatory and inhibitory neurons, there is an increase in the KNa current across subthreshold voltages only in inhibitory neurons, particularly in those with non-fast-spiking properties, resulting in inhibitory-neuron-specific impairments in excitability and action potential (AP) generation. We further observe evidence of synaptic rewiring, including increases in homotypic synaptic connectivity, accompanied by network hyperexcitability and hypersynchronicity. These findings support inhibitory-neuron-specific mechanisms in mediating the epileptogenic effects of KCNT1 channel GOF, offering cell-type-specific currents and effects as promising targets for therapeutic intervention.
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Affiliation(s)
- Amy N Shore
- Department of Neurological Sciences, University of Vermont, Burlington, VT 05405, USA
| | - Sophie Colombo
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA
| | - William F Tobin
- Department of Neurological Sciences, University of Vermont, Burlington, VT 05405, USA
| | - Sabrina Petri
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA
| | - Erin R Cullen
- Department of Neurological Sciences, University of Vermont, Burlington, VT 05405, USA
| | - Soledad Dominguez
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA
| | | | - Michael A Beaumont
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Axion BioSystems, Atlanta, GA 30309, USA
| | - Damian Williams
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA
| | - Dion Khodagholy
- Department of Electrical Engineering, Columbia University, New York, NY 10032, USA
| | - Mu Yang
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA
| | | | - Yueqing Peng
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
| | - Jennifer N Gelinas
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Neurology, Columbia University, New York, NY 10032, USA
| | - David B Goldstein
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Genetics and Development, Columbia University, New York, NY 10032, USA
| | - Michael J Boland
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Genetics and Development, Columbia University, New York, NY 10032, USA
| | - Wayne N Frankel
- Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Neurology, Columbia University, New York, NY 10032, USA
| | - Matthew C Weston
- Department of Neurological Sciences, University of Vermont, Burlington, VT 05405, USA.
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11
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Fu L, Boehe D, Orlitzky M. Are R&D-Intensive firms also corporate social responsibility specialists? A multicountry study. Res Policy 2020; 49:104082. [PMID: 32834183 PMCID: PMC7406420 DOI: 10.1016/j.respol.2020.104082] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 05/29/2020] [Accepted: 07/27/2020] [Indexed: 12/01/2022]
Abstract
Firms with higher R&D intensity tend to be corporate social responsibility (CSR) specialists. High-discretion slack resources allow R&D-intensive firms to be more balanced in their CSR. The R&D intensity–CSR specialization relationship varies across industry characteristics. A natural experiment indicates that R&D intensity influences CSR specialization, rather than vice versa.
Seeking to obtain efficiency in the development and integration of knowledge about R&D and corporate social responsibility (CSR), firms face hard choices about their resource allocation to these two areas because of the specialized nature of knowledge and related barriers to integration. We address this organizational resource allocation dilemma by relaxing the common assumption that firms are either responsible or irresponsible and examining financial slack as a possible moderator. Using a multicountry sample of 1,957 firms over a 16-year timespan, we find strong empirical support for the positive association between firms' R&D intensity and CSR specialization, a novel concept that—distinct from CSR as such—gauges the extent to which firms specialize in specific environmental, social, or governance aspects of CSR. However, there is insufficient support for financial slack as a moderator in general (except for one noteworthy industry pattern and an alternative operationalization of slack). The exceptions suggest that the nature of organizational slack may influence the relationship between R&D and CSR specialization.
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Affiliation(s)
- Limin Fu
- Australian Catholic University, Peter Faber Business School, 8-20 Napier Street, Sydney, NSW, 2060 Australia.,Business School, The University of Adelaide, 10 Pulteney St, Adelaide SA 5005, Australia
| | - Dirk Boehe
- Massey University, Business School, Albany Campus, Private Bag 102904, Auckland, 0745, New Zealand
| | - Marc Orlitzky
- Massey University, Business School, Albany Campus, Private Bag 102904, Auckland, 0745, New Zealand
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12
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Abstract
Advances in information technology have changed human interactions. These changes have had considerable implications for nonmedical and medical educational practices. The use of semi-private applications such as WhatsApp (Mountain View, CA), Slack (Canada), Viber (Israel), and Google Hangouts (Mountain View, CA) has not been well studied in nephrology education. In this narrative review, we review the literature on the use of these communication applications in medicine and nephrology education. Although many of these applications might be used currently in nephrology, there is little published data regarding the use of WhatsApp in nephrology fellowship. Given the easy accessibility of these communication applications by our learners in medical school, residency, and fellowship, the use of such applications can enhance nephrology education.
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Affiliation(s)
- Aadi Pandya
- Herricks High School, New Hyde Park, New York
| | | | - Kenar D Jhaveri
- Division of Kidney Diseases and Hypertension, Donald and Barbara Zucker School of Medicine, Hofstra/Northwell, Great Neck, NY.
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13
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Abstract
With a growing need to recruit the future nephrology workforce, medical educators and members of the nephrology community are turning to innovative approaches to improve communication and stimulate dialogue in the field. One feasible strategy is the use of electronic collaboration tools such as Slack (Slack Technologies, San Francisco, CA), which facilitates real-time conversational communication in a private or semiprivate virtual workspace. The potential uses of Slack for nephrology education, research collaboration, and community building are outlined in this overview.
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Affiliation(s)
- Jennie Lin
- Division of Nephrology, Department of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL.
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14
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Kates FR, Samuels SK, Case JB, Dujowich M. Lessons Learned from a Pilot Study Implementing a Team-Based Messaging Application ( Slack) to Improve Communication and Teamwork in Veterinary Medical Education. J Vet Med Educ 2020; 47:18-26. [PMID: 30920946 DOI: 10.3138/jvme.0717-091r2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Communication skills are paramount for a successful veterinary curriculum. Technological advances have improved communication processes, and the way instruction is delivered. Yet, with these advances come challenges such as email overload, increased interruptions, and miscommunications. Time is a valuable commodity at any high caseload veterinary teaching hospital. When increasingly more time is spent sending and receiving emails, text messages, pages, and calls in lieu of more focused clinical teaching, then the modes of communication and traditional learning theories need to be evaluated. An effective mode of communication is needed to reduce information overload and miscommunication. This article describes lessons learned from a pilot study to determine if a team-based messaging application could improve a surgical team's communication by having all forms of transmitted media directly related to their scope of work accessible to everyone on the team in one real-time digital platform (Slack). Fifteen members of a university-based surgical team were enrolled into the study and provided with surveys at specific time points to evaluate the efficacy of an internet-based team communication tool during a 3-month period. Results of our study showed an overall perception of improved communication among team members when using a team-based communication platform. Recommendations are provided to address team member's underutilization of the platform, which resulted in duplicate messages and miscommunication. We conclude an initial adoption by staff members is essential when implementing significant shifts in communication platforms.
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Affiliation(s)
- Frederick R Kates
- Department of Health Services Research, Management and Policy, College of Public Health and Health Professions, University of Florida
| | - Shenae K Samuels
- Department of Healthcare Management & Leadership, Texas Tech University Health Sciences Center, School of Health Professions
| | - J Brad Case
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida
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15
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Sarkisian SA, Kagel A. The Use of Slack for Medical Residency Development and Recruiting. J Innov Health Inform 2018; 25:194-195. [PMID: 30398463 DOI: 10.14236/jhi.v25i3.1019] [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] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/28/2018] [Accepted: 06/07/2018] [Indexed: 11/18/2022] Open
Abstract
As technology evolves, medical residency programmes must evolve as well. Slack is a cloud-based team collaborative application that was used by our Emergency Medicine Residency Program to not only streamline communication but also help in recruiting new residents. The majority of medical students auditioning for our programme responded to our use of Slack in a positive manner. We encourage other residency programmes to adopt a similar communication platform to attract the best applicant in a pool of modern learners.
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16
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Gururaj S, Palmer EE, Sheehan GD, Kandula T, Macintosh R, Ying K, Morris P, Tao J, Dias KR, Zhu Y, Dinger ME, Cowley MJ, Kirk EP, Roscioli T, Sachdev R, Duffey ME, Bye A, Bhattacharjee A. A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy. Cell Rep 2018; 21:926-933. [PMID: 29069600 DOI: 10.1016/j.celrep.2017.09.088] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 06/12/2017] [Accepted: 09/26/2017] [Indexed: 12/31/2022] Open
Abstract
Early infantile epileptic encephalopathies (EOEE) are a debilitating spectrum of disorders associated with cognitive impairments. We present a clinical report of a KCNT2 mutation in an EOEE patient. The de novo heterozygous variant Phe240Leu SLICK was identified by exome sequencing and confirmed by Sanger sequencing. Phe240Leu rSlick and hSLICK channels were electrophysiologically, heterologously characterized to reveal three significant alterations to channel function. First, [Cl-]i sensitivity was reversed in Phe240Leu channels. Second, predominantly K+-selective WT channels were made to favor Na+ over K+ by Phe240Leu. Third, and consequent to altered ion selectivity, Phe240Leu channels had larger inward conductance. Further, rSlick channels induced membrane hyperexcitability when expressed in primary neurons, resembling the cellular seizure phenotype. Taken together, our results confirm that Phe240Leu is a "change-of-function" KCNT2 mutation, demonstrating unusual altered selectivity in KNa channels. These findings establish pathogenicity of the Phe240Leu KCNT2 mutation in the reported EOEE patient.
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Affiliation(s)
- Sushmitha Gururaj
- Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
| | - Elizabeth Emma Palmer
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
| | - Garrett D Sheehan
- Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
| | - Tejaswi Kandula
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
| | | | - Kevin Ying
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Paula Morris
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Jiang Tao
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Kerith-Rae Dias
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Ying Zhu
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
| | - Marcel E Dinger
- University of New South Wales, Sydney, NSW 2031, Australia; Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Mark J Cowley
- University of New South Wales, Sydney, NSW 2031, Australia; Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
| | - Edwin P Kirk
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
| | - Tony Roscioli
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
| | - Rani Sachdev
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
| | - Michael E Duffey
- Physiology and Biophysics, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
| | - Ann Bye
- Sydney Children's Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
| | - Arin Bhattacharjee
- Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA; Program for Neuroscience, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA.
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17
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Nowotka MM, Gaulton A, Mendez D, Bento AP, Hersey A, Leach A. Using ChEMBL web services for building applications and data processing workflows relevant to drug discovery. Expert Opin Drug Discov 2017; 12:757-767. [PMID: 28602100 DOI: 10.1080/17460441.2017.1339032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
INTRODUCTION ChEMBL is a manually curated database of bioactivity data on small drug-like molecules, used by drug discovery scientists. Among many access methods, a REST API provides programmatic access, allowing the remote retrieval of ChEMBL data and its integration into other applications. This approach allows scientists to move from a world where they go to the ChEMBL web site to search for relevant data, to one where ChEMBL data can be simply integrated into their everyday tools and work environment. Areas covered: This review highlights some of the audiences who may benefit from using the ChEMBL API, and the goals they can address, through the description of several use cases. The examples cover a team communication tool (Slack), a data analytics platform (KNIME), batch job management software (Luigi) and Rich Internet Applications. Expert opinion: The advent of web technologies, cloud computing and micro services oriented architectures have made REST APIs an essential ingredient of modern software development models. The widespread availability of tools consuming RESTful resources have made them useful for many groups of users. The ChEMBL API is a valuable resource of drug discovery bioactivity data for professional chemists, chemistry students, data scientists, scientific and web developers.
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Affiliation(s)
- Michał M Nowotka
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
| | - Anna Gaulton
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
| | - David Mendez
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
| | - A Patricia Bento
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
| | - Anne Hersey
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
| | - Andrew Leach
- a European Molecular Biology Laboratory - European Bioinformatics Institute , Wellcome Genome Campus , Hinxton , UK
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18
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Hirata K, Kanehisa H, Miyamoto N. Acute effect of static stretching on passive stiffness of the human gastrocnemius fascicle measured by ultrasound shear wave elastography. Eur J Appl Physiol 2017; 117:493-9. [PMID: 28161870 DOI: 10.1007/s00421-017-3550-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 01/16/2017] [Indexed: 10/20/2022]
Abstract
PURPOSE Passive muscle stiffness and muscle architecture at a given joint angle, as well as slack angle of the muscle have been shown to change after an acute bout of stretching. However, it remains unclear whether passive muscle stiffness at a given fascicle length is reduced after stretching. We aimed to elucidate the acute effect of static stretching on the passive fascicle stiffness using ultrasound shear wave elastography. METHODS Shear modulus, fascicle length, and slack angle of the medial gastrocnemius (MG) as well as passive plantar flexion torque during passive dorsiflexion were measured before and after a 5-min static stretching in 14 healthy males. RESULTS After stretching, passive torques were significantly reduced at >50% of range of motion (ROM). Shear modulus at a given fascicle length was significantly reduced at >80% of the change in fascicle length during passive dorsiflexion. Slack angle of MG was observed at the middle part of ROM and significantly shifted toward more dorsiflexed position after stretching. CONCLUSION The present study showed the significant effectiveness of static stretching on the passive fascicle stiffness. Furthermore, the present results suggest that both the shift in slack angle and the reduction in passive fascicle stiffness contribute to produce the change in passive torque-joint angle relationship during passive dorsiflexion. Notably, the contribution of the reduced passive fascicle stiffness to the decrease in passive torque is substantial over the latter part of ROM.
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19
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Abstract
The magnocellular neurosecretory cells (MNCs) of the hypothalamus secrete the neurohormones vasopressin and oxytocin. The systemic release of these hormones depends on the rate and pattern of MNC firing and it is therefore important to identify the ion channels that contribute to the electrical behaviour of MNCs. In the present study, we report evidence for the presence of Na(+) -activated K(+) (KN a ) channels in rat MNCs. KN a channels mediate outwardly rectifying K(+) currents activated by the increases in intracellular Na(+) that occur during electrical activity. Although the molecular identity of native KN a channels is unclear, their biophysical properties are consistent with those of expressed Slick (slo 2.1) and Slack (slo 2.2) proteins. Using immunocytochemistry and Western blot experiments, we found that both Slick and Slack proteins are expressed in rat MNCs. Using whole cell voltage clamp techniques on acutely isolated rat MNCs, we found that inhibiting Na(+) influx by the addition of the Na(+) channel blocker tetrodotoxin or the replacement of Na(+) in the external solution with Li(+) caused a significant decrease in sustained outward currents. Furthermore, the evoked outward current density was significantly higher in rat MNCs using patch pipettes containing 60 mm Na(+) than it was when patch pipettes containing 0 mm Na(+) were used. Our data show that functional KN a channels are expressed in rat MNCs. These channels could contribute to the activity-dependent afterhyperpolarisations that have been identified in the MNCs and thereby play a role in the regulation of their electrical behaviour.
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Affiliation(s)
- V Bansal
- Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - T E Fisher
- Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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20
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Gururaj S, Fleites J, Bhattacharjee A. Slack sodium-activated potassium channel membrane expression requires p38 mitogen-activated protein kinase phosphorylation. Neuropharmacology 2015; 103:279-89. [PMID: 26721627 DOI: 10.1016/j.neuropharm.2015.12.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 01/14/2023]
Abstract
p38 MAPK has long been understood as an inducible kinase under conditions of cellular stress, but there is now increasing evidence to support its role in the regulation of neuronal function. Several phosphorylation targets have been identified, an appreciable number of which are ion channels, implicating the possible involvement of p38 MAPK in neuronal excitability. The KNa channel Slack is an important protein to be studied as it is highly and ubiquitously expressed in DRG neurons and is important in the maintenance of their firing accommodation. We sought to examine if the Slack channel could be a substrate of p38 MAPK activity. First, we found that the Slack C-terminus contains two putative p38 MAPK phosphorylation sites that are highly conserved across species. Second, we show via electrophysiology experiments that KNa currents and further, Slack currents, are subject to tonic modulation by p38 MAPK. Third, biochemical approaches revealed that Slack channel regulation by p38 MAPK occurs through direct phosphorylation at the two putative sites of interaction, and mutating both sites prevented surface expression of Slack channels. Based on these results, we conclude that p38 MAPK is an obligate regulator of Slack channel function via the trafficking of channels into the membrane. The present study identifies Slack KNa channels as p38 MAPK substrates.
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Affiliation(s)
- Sushmitha Gururaj
- Department of Pharmacology and Toxicology, The State University of New York, Buffalo, USA
| | - John Fleites
- Program in Neuroscience, The State University of New York, Buffalo, USA
| | - Arin Bhattacharjee
- Department of Pharmacology and Toxicology, The State University of New York, Buffalo, USA; Program in Neuroscience, The State University of New York, Buffalo, USA.
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21
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van Arkel RJ, Amis AA, Jeffers JRT. The envelope of passive motion allowed by the capsular ligaments of the hip. J Biomech 2015; 48:3803-9. [PMID: 26429769 PMCID: PMC4655836 DOI: 10.1016/j.jbiomech.2015.09.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 07/28/2015] [Accepted: 09/05/2015] [Indexed: 11/25/2022]
Abstract
Laboratory data indicate the hip capsular ligaments prevent excessive range of motion, may protect the joint against adverse edge loading and contribute to synovial fluid replenishment at the cartilage surfaces of the joint. However, their repair after joint preserving or arthroplasty surgery is not routine. In order to restore their biomechanical function after hip surgery, the positions of the hip at which the ligaments engage together with their tensions when they engage is required. Nine cadaveric left hips without pathology were skeletonised except for the hip joint capsule and mounted in a six-degrees-of-freedom testing rig. A 5 N m torque was applied to all rotational degrees-of-freedom separately to quantify the passive restraint envelope throughout the available range of motion with the hip functionally loaded. The capsular ligaments allowed the hip to internally/externally rotate with a large range of un-resisted rotation (up to 50±10°) in mid-flexion and mid-ab/adduction but this was reduced towards the limits of flexion/extension and ab/adduction such that there was a near-zero slack region in some positions (p<0.014). The slack region was not symmetrical; the mid-slack point was found with internal rotation in extension and external rotation in flexion (p<0.001). The torsional stiffness of the capsular ligamentous restraint averaged 0.8±0.3 N m/° and was greater in positions where there were large slack regions. These data provide a target for restoration of normal capsular ligament tensions after joint preserving hip surgery. Ligament repair is technically demanding, particularly for arthroscopic procedures, but failing to restore their function may increase the risk of osteoarthritic degeneration.
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Affiliation(s)
- Richard J van Arkel
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, Unitrd Kingdom
| | - Andrew A Amis
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, Unitrd Kingdom; Musculoskeletal Surgery, Department of Surgery and Cancer, Imperial College London, Charing Cross Hospital, London W6 8RF, United Kingdom
| | - Jonathan R T Jeffers
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, Unitrd Kingdom.
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Báez A, Salceda E, Fló M, Graña M, Fernández C, Vega R, Soto E. α-Dendrotoxin inhibits the ASIC current in dorsal root ganglion neurons from rat. Neurosci Lett 2015; 606:42-7. [PMID: 26314509 DOI: 10.1016/j.neulet.2015.08.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/11/2015] [Accepted: 08/19/2015] [Indexed: 11/23/2022]
Abstract
Dendrotoxins are a group of peptide toxins purified from the venom of several mamba snakes. α-Dendrotoxin (α-DTx, from the Eastern green mamba Dendroaspis angusticeps) is a well-known blocker of voltage-gated K(+) channels and specifically of K(v)1.1, K(v)1.2 and K(v)1.6. In this work we show that α-DTx inhibited the ASIC currents in DRG neurons (IC50=0.8 μM) when continuously perfused during 25 s (including a 5 s pulse to pH 6.1), but not when co-applied with the pH drop. Additionally, we show that α-DTx abolished a transient component of the outward current that, in some experiments, appeared immediately after the end of the acid pulse. Our data indicate that α-DTx inhibits ASICs in the high nM range while some Kv are inhibited in the low nM range. The α-DTx selectivity and its potential interaction with ASICs should be taken in consideration when DTx is used in the high nM range.
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23
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Abstract
The sodium-activated potassium KNa channels Slack and Slick are encoded by KCNT1 and KCNT2, respectively. These channels are found in neurons throughout the brain, and are responsible for a delayed outward current termed I KNa. These currents integrate into shaping neuronal excitability, as well as adaptation in response to maintained stimulation. Abnormal Slack channel activity may play a role in Fragile X syndrome, the most common cause for intellectual disability and inherited autism. Slack channels interact directly with the fragile X mental retardation protein (FMRP) and I KNa is reduced in animal models of Fragile X syndrome that lack FMRP. Human Slack mutations that alter channel activity can also lead to intellectual disability, as has been found for several childhood epileptic disorders. Ongoing research is elucidating the relationship between mutant Slack channel activity, development of early onset epilepsies and intellectual impairment. This review describes the emerging role of Slack channels in intellectual disability, coupled with an overview of the physiological role of neuronal I KNa currents.
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Affiliation(s)
- Grace E Kim
- Departments of Pharmacology and Cellular & Molecular Physiology, Yale University School of Medicine New Haven, CT, USA
| | - Leonard K Kaczmarek
- Departments of Pharmacology and Cellular & Molecular Physiology, Yale University School of Medicine New Haven, CT, USA
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24
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Abstract
Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K+ channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K+ channels in pancreatic duct cells, including KCNN4 (KCa3.1), KCNMA1 (KCa1.1), KCNQ1 (Kv7.1), KCNH2 (Kv11.1), KCNH5 (Kv10.2), KCNT1 (KCa4.1), KCNT2 (KCa4.2), and KCNK5 (K2P5.1). We will give an overview of K+ channels with respect to their electrophysiological and pharmacological characteristics and regulation, which we know from other cell types, preferably in epithelia, and, where known, their identification and functions in pancreatic ducts and in adenocarcinoma cells. We conclude by pointing out some outstanding questions and future directions in pancreatic K+ channel research with respect to the physiology of secretion and pancreatic pathologies, including pancreatitis, cystic fibrosis, and cancer, in which the dysregulation or altered expression of K+ channels may be of importance.
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Affiliation(s)
- Mikio Hayashi
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
| | - Ivana Novak
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
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