Journal articles: 'Kv7.2/3'

1

Hernandez, Ciria C., Björn Falkenburger, and Mark S. Shapiro. "Affinity for phosphatidylinositol 4,5-bisphosphate determines muscarinic agonist sensitivity of Kv7 K+ channels." Journal of General Physiology 134, no. 5 (October 26, 2009): 437–48. http://dx.doi.org/10.1085/jgp.200910313.

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Kv7 K+-channel subunits differ in their apparent affinity for PIP2 and are differentially expressed in nerve, muscle, and epithelia in accord with their physiological roles in those tissues. To investigate how PIP2 affinity affects the response to physiological stimuli such as receptor stimulation, we exposed homomeric and heteromeric Kv7.2, 7.3, and 7.4 channels to a range of concentrations of the muscarinic receptor agonist oxotremorine-M (oxo-M) in a heterologous expression system. Activation of M1 receptors by oxo-M leads to PIP2 depletion through Gq and phospholipase C (PLC). Chinese hamster ovary cells were transiently transfected with Kv7 subunits and M1 receptors and studied under perforated-patch voltage clamp. For Kv7.2/7.3 heteromers, the EC50 for current suppression was 0.44 ± 0.08 µM, and the maximal inhibition (Inhibmax) was 74 ± 3% (n = 5–7). When tonic PIP2 abundance was increased by overexpression of PIP 5-kinase, the EC50 was shifted threefold to the right (1.2 ± 0.1 µM), but without a significant change in Inhibmax (73 ± 4%, n = 5). To investigate the muscarinic sensitivity of Kv7.3 homomers, we used the A315T pore mutant (Kv7.3T) that increases whole-cell currents by 30-fold without any change in apparent PIP2 affinity. Kv7.3T currents had a slightly right-shifted EC50 as compared with Kv7.2/7.3 heteromers (1.0 ± 0.8 µM) and a strongly reduced Inhibmax (39 ± 3%). In contrast, the dose–response curve of homomeric Kv7.4 channels was shifted considerably to the left (66 ± 8 nM), and Inhibmax was slightly increased (81 ± 6%, n = 3–4). We then studied several Kv7.2 mutants with altered apparent affinities for PIP2 by coexpressing them with Kv7.3T subunits to boost current amplitudes. For the lower affinity (Kv7.2 (R463Q)/Kv7.3T) or higher affinity (Kv7.2 (R463E)/Kv7.3T) channels, the EC50 and Inhibmax were similar to Kv7.4 or Kv7.3T homomers (0.12 ± 0.08 µM and 79 ± 6% [n = 3–4] and 0.58 ± 0.07 µM and 27 ± 3% [n = 3–4], respectively). The very low-affinity Kv7.2 (R452E, R459E, and R461E) triple mutant was also coexpressed with Kv7.3T. The resulting heteromer displayed a very low EC50 for inhibition (32 ± 8 nM) and a slightly increased Inhibmax (83 ± 3%, n = 3–4). We then constructed a cellular model that incorporates PLC activation by oxo-M, PIP2 hydrolysis, PIP2 binding to Kv7-channel subunits, and K+ current through Kv7 tetramers. We were able to fully reproduce our data and extract a consistent set of PIP2 affinities.

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Miceli, Francesco, Maria V. Soldovieri, Paolo Ambrosino, Laura Manocchio, Ilaria Mosca, and Maurizio Taglialatela. "Pharmacological Targeting of Neuronal Kv7.2/3 Channels: A Focus on Chemotypes and Receptor Sites." Current Medicinal Chemistry 25, no. 23 (July 4, 2018): 2637–60. http://dx.doi.org/10.2174/0929867324666171012122852.

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Background: The Kv7 (KCNQ) subfamily of voltage-gated potassium channels consists of 5 members (Kv7.1-5) each showing characteristic tissue distribution and physiological roles. Given their functional heterogeneity, Kv7 channels represent important pharmacological targets for the development of new drugs for neuronal, cardiovascular and metabolic diseases. <p> Objective: In the present manuscript, we focus on describing the pharmacological relevance and potential therapeutic applications of drugs acting on neuronally-expressed Kv7.2/3 channels, placing particular emphasis on the different chemotypes, and highlighting their pharmacodynamic and, whenever possible, pharmacokinetic peculiarities. <p> Methods: The present work is based on an in-depth search of the currently available scientific literature, and on our own experience and knowledge in the field of neuronal Kv7 channel pharmacology. Space limitations impeded to describe the full pharmacological potential of Kv7 channels; thus, we have chosen to focus on neuronal channels composed of Kv7.2 and Kv7.3 subunits, and to mainly concentrate on their involvement in epilepsy. <p> Results: An astonishing heterogeneity in the molecular scaffolds exploitable to develop Kv7.2/3 modulators is evident, with important structural/functional peculiarities of distinct compound classes. <p> Conclusion: In the present work we have attempted to show the current status and growing potential of the Kv7 pharmacology field. We anticipate a bright future for the field, and express our hopes that the efforts herein reviewed will result in an improved treatment of hyperexcitability (or any other) diseases.

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Peretz, Asher, Anton Sheinin, Cuiyong Yue, Nurit Degani-Katzav, Gilad Gibor, Rachel Nachman, Anna Gopin, et al. "Pre- and Postsynaptic Activation of M-Channels By a Novel Opener Dampens Neuronal Firing and Transmitter Release." Journal of Neurophysiology 97, no. 1 (January 2007): 283–95. http://dx.doi.org/10.1152/jn.00634.2006.

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The M-type K+ current (M-current), encoded by Kv7.2/3 (KCNQ2/3) K+ channels, plays a critical role in regulating neuronal excitability because it counteracts subthreshold depolarizations. Here we have characterized the functions of pre- and postsynaptic M-channels using a novel Kv7.2/3 channel opener, NH6, which we synthesized as a new derivative of N-phenylanthranilic acid. NH6 exhibits a good selectivity as it does not affect Kv7.1 and IKS K+ currents as well as NR1/NR2B, AMPA, and GABAA receptor-mediated currents. Superfusion of NH6 increased recombinant Kv7.2/3 current amplitude (EC50 = 18 μM) by causing a hyperpolarizing shift of the voltage activation curve and by markedly slowing the deactivation kinetics. Activation of native M-currents by NH6 robustly reduced the number of evoked and spontaneous action potentials in cultured cortical, hippocampal and dorsal root ganglion neurons. In hippocampal slices, NH6 decreased somatically evoked spike afterdepolarization of CA1 pyramidal neurons and induced regular firing in bursting neurons. Activation of M-channels by NH6, potently reduced the frequency of spontaneous excitatory and inhibitory postsynaptic currents. Activation of M-channels also decreased the frequency of miniature excitatory (mEPSC) and inhibitory (mIPSC) postsynaptic currents without affecting their amplitude and waveform, thus suggesting that M-channels presynaptically inhibit glutamate and GABA release. Our results suggest a role of presynaptic M-channels in the release of glutamate and GABA. They also indicate that M-channels act pre- and postsynaptically to dampen neuronal excitability.

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Wright, Andrew B., Khrystyna Yu Sukhanova, and Keith S. Elmslie. "KV7 channels are potential regulators of the exercise pressor reflex." Journal of Neurophysiology 126, no. 1 (July 1, 2021): 1–10. http://dx.doi.org/10.1152/jn.00700.2020.

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KV7 channels control neuronal excitability. We show that these channels are expressed in muscle afferents and generate currents that are blocked by XE991 and bradykinin (BK). The XE991 block suggests that KV7 current comprises KV7.2/3 and KV7.5 channels. The BK inhibition of KV7 channels may explain how BK activates the exercise pressor reflex (EPR). Retigabine can enhance KV7 current, which could help control the inappropriately activated EPR in patients with cardiovascular disease.

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Barro-Soria, Rene. "Effects of small molecules on neurodevelopmental disorder-associated Kv7.2/3 mutations." Biophysical Journal 123, no. 3 (February 2024): 528a. http://dx.doi.org/10.1016/j.bpj.2023.11.3192.

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Peretz, Asher S., Eti Patrich, Polina Kornilov, Nataly Menaker, and Bernard Attali. "A Novel Compound Targeting Kv7.2/3 Channels Relieves Inflammatory and Neuropathic Pain." Biophysical Journal 106, no. 2 (January 2014): 141a. http://dx.doi.org/10.1016/j.bpj.2013.11.820.

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Liu, Wenjing, and Jérôme J. Devaux. "Calmodulin orchestrates the heteromeric assembly and the trafficking of KCNQ2/3 (Kv7.2/3) channels in neurons." Molecular and Cellular Neuroscience 58 (January 2014): 40–52. http://dx.doi.org/10.1016/j.mcn.2013.12.005.

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Surur, Abdrrahman S., Christian Bock, Kristin Beirow, Konrad Wurm, Lukas Schulig, Markus K. Kindermann, Werner Siegmund, Patrick J. Bednarski, and Andreas Link. "Flupirtine and retigabine as templates for ligand-based drug design of KV7.2/3 activators." Organic & Biomolecular Chemistry 17, no. 18 (2019): 4512–22. http://dx.doi.org/10.1039/c9ob00511k.

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Puzzling stability: molecular jigsaw pieces of residues characterized in light of activity, lipophilicity, stability against oxidation, and hepatotoxicity were combined to yield flupirtine analogue 25b.

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Li, S., V. Choi, and T. Tzounopoulos. "Pathogenic plasticity of Kv7.2/3 channel activity is essential for the induction of tinnitus." Proceedings of the National Academy of Sciences 110, no. 24 (May 28, 2013): 9980–85. http://dx.doi.org/10.1073/pnas.1302770110.

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Miranda, Pablo, Alba Cadaveira-Mosquera, Rafaela Gonzalez-Montelongo, Alvaro Villarroel, Jose Antonio Lamas, Diego Alvarez de la Rosa, and Teresa Giraldez. "Regulation of the Kv7.2/3 Channels by the Neuronal Serum-and Gluococorticoids-Regulated Kinase 1.1." Biophysical Journal 104, no. 2 (January 2013): 268a. http://dx.doi.org/10.1016/j.bpj.2012.11.1505.

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Sander, Svenja E., Catherine Lambrecht, and Angelika Richter. "The KV7.2/3 preferring channel opener ICA 27243 attenuates L-DOPA-induced dyskinesia in hemiparkinsonian rats." Neuroscience Letters 545 (June 2013): 59–63. http://dx.doi.org/10.1016/j.neulet.2013.04.017.

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Pablo, Juan Lorenzo, and Geoffrey S. Pitt. "FGF14 is a regulator of KCNQ2/3 channels." Proceedings of the National Academy of Sciences 114, no. 1 (December 19, 2016): 154–59. http://dx.doi.org/10.1073/pnas.1610158114.

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KCNQ2/3 (Kv7.2/7.3) channels and voltage-gated sodium channels (VGSCs) are enriched in the axon initial segment (AIS) where they bind to ankyrin-G and coregulate membrane potential in central nervous system neurons. The molecular mechanisms supporting coordinated regulation of KCNQ and VGSCs and the cellular mechanisms governing KCNQ trafficking to the AIS are incompletely understood. Here, we show that fibroblast growth factor 14 (FGF14), previously described as a VGSC regulator, also affects KCNQ function and localization. FGF14 knockdown leads to a reduction of KCNQ2 in the AIS and a reduction in whole-cell KCNQ currents. FGF14 positively regulates KCNQ2/3 channels in a simplified expression system. FGF14 interacts with KCNQ2 at a site distinct from the FGF14–VGSC interaction surface, thus enabling the bridging of NaV1.6 and KCNQ2. These data implicate FGF14 as an organizer of channel localization in the AIS and provide insight into the coordination of KCNQ and VGSC conductances in the regulation of membrane potential.

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Lee, Inn-Chi, Jiann-Jou Yang, Ying-Ming Liou, and Swee-Hee Wong. "KCNQ2 Selectivity Filter Mutations Cause Kv7.2 M-Current Dysfunction and Configuration Changes Manifesting as Epileptic Encephalopathies and Autistic Spectrum Disorders." Cells 11, no. 5 (March 5, 2022): 894. http://dx.doi.org/10.3390/cells11050894.

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KCNQ2 mutations can cause benign familial neonatal convulsions (BFNCs), epileptic encephalopathy (EE), and mild-to-profound neurodevelopmental disabilities. Mutations in the KCNQ2 selectivity filter (SF) are critical to neurodevelopmental outcomes. Three patients with neonatal EE carry de novo heterozygous KCNQ2 p.Thr287Ile, p.Gly281Glu and p.Pro285Thr, and all are followed-up in our clinics. Whole-cell patch-clamp analysis with transfected mutations was performed. The Kv7.2 in three mutations demonstrated significant current changes in the homomeric-transfected cells. The conduction curves for V1/2, the K slope, and currents in 3 mutations were lower than those for the wild type (WT). The p.Gly281Glu had a worse conductance than the p.Thr287Ile and p.Pro285Thr, the patient compatible with p.Gly281Glu had a worse clinical outcome than patients with p.Thr287Ile and p.Pro285Thr. The p.Gly281Glu had more amino acid weight changes than the p.Gly281Glu and p.Pro285Thr. Among 5 BFNCs and 23 EE from mutations in the SF, the greater weight of the mutated protein compared with that of the WT was presumed to cause an obstacle to pore size, which is one of the most important factors in the phenotype and outcome. For the 35 mutations in the SF domain, using changes in amino acid weight between the WT and the KCNQ2 mutations to predict EE resulted in 80.0% sensitivity and 80% specificity, a positive prediction rate of 96.0%, and a negative prediction rate of 40.0% (p = 0.006, χ2 (1, n = 35) = 7.56; odds ratio 16.0, 95% confidence interval, 1.50 to 170.63). The findings suggest that p.Thr287Ile, p.Gly281Glu and p.Pro285Thr are pathogenic to KCNQ2 EE. In mutations in SF, a mutated protein heavier than the WT is a factor in the Kv7.2 current and outcome.

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Roeloffs, Rosemarie, Alan D. Wickenden, Christopher Crean, Stephen Werness, Grant McNaughton-Smith, James Stables, James O. McNamara, Neil Ghodadra, and Greg C. Rigdon. "In Vivo Profile of ICA-27243 [N-(6-Chloro-pyridin-3-yl)-3,4-difluoro-benzamide], a Potent and Selective KCNQ2/Q3 (Kv7.2/Kv7.3) Activator in Rodent Anticonvulsant Models." Journal of Pharmacology and Experimental Therapeutics 326, no. 3 (June 24, 2008): 818–28. http://dx.doi.org/10.1124/jpet.108.137794.

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El-Chemali, Léa El, Suzan Boutary, Song Liu, Guo-Jun Liu, Ryan J. Middleton, Richard B. Banati, Gregor Bahrenberg, Rainer Rupprecht, Michael Schumacher, and Liliane Massaad-Massade. "GRT-X Stimulates Dorsal Root Ganglia Axonal Growth in Culture via TSPO and Kv7.2/3 Potassium Channel Activation." International Journal of Molecular Sciences 25, no. 13 (July 3, 2024): 7327. http://dx.doi.org/10.3390/ijms25137327.

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GRT-X, which targets both the mitochondrial translocator protein (TSPO) and the Kv7.2/3 (KCNQ2/3) potassium channels, has been shown to efficiently promote recovery from cervical spine injury. In the present work, we investigate the role of GRT-X and its two targets in the axonal growth of dorsal root ganglion (DRG) neurons. Neurite outgrowth was quantified in DRG explant cultures prepared from wild-type C57BL6/J and TSPO-KO mice. TSPO was pharmacologically targeted with the agonist XBD173 and the Kv7 channels with the activator ICA-27243 and the inhibitor XE991. GRT-X efficiently stimulated DRG axonal growth at 4 and 8 days after its single administration. XBD173 also promoted axonal elongation, but only after 8 days and its repeated administration. In contrast, both ICA27243 and XE991 tended to decrease axonal elongation. In dissociated DRG neuron/Schwann cell co-cultures, GRT-X upregulated the expression of genes associated with axonal growth and myelination. In the TSPO-KO DRG cultures, the stimulatory effect of GRT-X on axonal growth was completely lost. However, GRT-X and XBD173 activated neuronal and Schwann cell gene expression after TSPO knockout, indicating the presence of additional targets warranting further investigation. These findings uncover a key role of the dual mode of action of GRT-X in the axonal elongation of DRG neurons.

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Sedivy, Vojtech, Shreena Joshi, Youssef Ghaly, Roman Mizera, Marie Zaloudikova, Sean Brennan, Jana Novotna, Jan Herget, and Alison M. Gurney. "Role of Kv7 channels in responses of the pulmonary circulation to hypoxia." American Journal of Physiology-Lung Cellular and Molecular Physiology 308, no. 1 (January 1, 2015): L48—L57. http://dx.doi.org/10.1152/ajplung.00362.2013.

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Hypoxic pulmonary vasoconstriction (HPV) is a beneficial mechanism that diverts blood from hypoxic alveoli to better ventilated areas of the lung, but breathing hypoxic air causes the pulmonary circulation to become hypertensive. Responses to airway hypoxia are associated with depolarization of smooth muscle cells in the pulmonary arteries and reduced activity of K+channels. As Kv7 channels have been proposed to play a key role in regulating the smooth muscle membrane potential, we investigated their involvement in the development of HPV and hypoxia-induced pulmonary hypertension. Vascular effects of the selective Kv7 blocker, linopirdine, and Kv7 activator, flupirtine, were investigated in isolated, saline-perfused lungs from rats maintained for 3–5 days in an isobaric hypoxic chamber (FiO2= 0.1) or room air. Linopirdine increased vascular resistance in lungs from normoxic, but not hypoxic rats. This effect was associated with reduced mRNA expression of the Kv7.4 channel α-subunit in hypoxic arteries, whereas Kv7.1 and Kv7.5 were unaffected. Flupirtine had no effect in normoxic lungs but reduced vascular resistance in hypoxic lungs. Moreover, oral dosing with flupirtine (30 mg/kg/day) prevented short-term in vivo hypoxia from increasing pulmonary vascular resistance and sensitizing the arteries to acute hypoxia. These findings suggest a protective role for Kv7.4 channels in the pulmonary circulation, limiting its reactivity to pressor agents and preventing hypoxia-induced pulmonary hypertension. They also provide further support for the therapeutic potential of Kv7 activators in pulmonary vascular disease.

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Wu, Yong-Jin, Charles M. Conway, Li-Qiang Sun, Frederic Machet, Jie Chen, Ping Chen, Huan He, et al. "Discovery of (S,E)-3-(2-fluorophenyl)-N-(1-(3-(pyridin-3-yloxy)phenyl)ethyl)-acrylamide as a potent and efficacious KCNQ2 (Kv7.2) opener for the treatment of neuropathic pain." Bioorganic & Medicinal Chemistry Letters 23, no. 22 (November 2013): 6188–91. http://dx.doi.org/10.1016/j.bmcl.2013.08.092.

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Dickson, Eamonn J., Björn H. Falkenburger, and Bertil Hille. "Quantitative properties and receptor reserve of the IP3 and calcium branch of Gq-coupled receptor signaling." Journal of General Physiology 141, no. 5 (April 29, 2013): 521–35. http://dx.doi.org/10.1085/jgp.201210886.

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Gq-coupled plasma membrane receptors activate phospholipase C (PLC), which hydrolyzes membrane phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). This leads to calcium release, protein kinase C (PKC) activation, and sometimes PIP2 depletion. To understand mechanisms governing these diverging signals and to determine which of these signals is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels, we monitored levels of PIP2, IP3, and calcium in single living cells. DAG and PKC are monitored in our companion paper (Falkenburger et al. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210887). The results extend our previous kinetic model of Gq-coupled receptor signaling to IP3 and calcium. We find that activation of low-abundance endogenous P2Y2 receptors by a saturating concentration of uridine 5′-triphosphate (UTP; 100 µM) leads to calcium release but not to PIP2 depletion. Activation of overexpressed M1 muscarinic receptors by 10 µM Oxo-M leads to a similar calcium release but also depletes PIP2. KCNQ2/3 channels are inhibited by Oxo-M (by 85%), but not by UTP (<1%). These differences can be attributed purely to differences in receptor abundance. Full amplitude calcium responses can be elicited even after PIP2 was partially depleted by overexpressed inducible phosphatidylinositol 5-phosphatases, suggesting that very low amounts of IP3 suffice to elicit a full calcium release. Hence, weak PLC activation can elicit robust calcium signals without net PIP2 depletion or KCNQ2/3 channel inhibition.

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Falkenburger, Björn H., Eamonn J. Dickson, and Bertil Hille. "Quantitative properties and receptor reserve of the DAG and PKC branch of Gq-coupled receptor signaling." Journal of General Physiology 141, no. 5 (April 29, 2013): 537–55. http://dx.doi.org/10.1085/jgp.201210887.

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Gq protein–coupled receptors (GqPCRs) of the plasma membrane activate the phospholipase C (PLC) signaling cascade. PLC cleaves the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers diacylgycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), leading to calcium release, protein kinase C (PKC) activation, and in some cases, PIP2 depletion. We determine the kinetics of each of these downstream endpoints and also ask which is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels in single living tsA-201 cells. We measure DAG production and PKC activity by Förster resonance energy transfer–based sensors, and PIP2 by KCNQ2/3 channels. Fully activating endogenous purinergic receptors by uridine 5′triphosphate (UTP) leads to calcium release, DAG production, and PKC activation, but no net PIP2 depletion. Fully activating high-density transfected muscarinic receptors (M1Rs) by oxotremorine-M (Oxo-M) leads to similar calcium, DAG, and PKC signals, but PIP2 is depleted. KCNQ2/3 channels are inhibited by the Oxo-M treatment (85%) and not by UTP (<1%), indicating that depletion of PIP2 is required to inhibit KCNQ2/3 in response to receptor activation. Overexpression of A kinase–anchoring protein (AKAP)79 or calmodulin (CaM) does not increase KCNQ2/3 inhibition by UTP. From these results and measurements of IP3 and calcium presented in our companion paper (Dickson et al. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210886), we extend our kinetic model for signaling from M1Rs to DAG/PKC and IP3/calcium signaling. We conclude that calcium/CaM and PKC-mediated phosphorylation do not underlie dynamic KCNQ2/3 channel inhibition during GqPCR activation in tsA-201 cells. Finally, our experimental data provide indirect evidence for cleavage of PI(4)P by PLC in living cells, and our modeling revisits/explains the concept of receptor reserve with measurements from all steps of GqPCR signaling.

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Anta, Begoña, Carlos Martín-Rodríguez, Carolina Gomis-Perez, Laura Calvo, Saray López-Benito, Andrés A. Calderón-García, Cristina Vicente-García, Álvaro Villarroel, and Juan C. Arévalo. "Ubiquitin-specific Protease 36 (USP36) Controls Neuronal Precursor Cell-expressed Developmentally Down-regulated 4-2 (Nedd4-2) Actions over the Neurotrophin Receptor TrkA and Potassium Voltage-gated Channels 7.2/3 (Kv7.2/3)." Journal of Biological Chemistry 291, no. 36 (July 21, 2016): 19132–45. http://dx.doi.org/10.1074/jbc.m116.722637.

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Erdem, Fatma A. "Phosphorylation of KV7.2 regulates its PIP2 sensitivity." Intrinsic Activity 3, Suppl. 2 (September 9, 2015): A2.21. http://dx.doi.org/10.25006/ia.3.s2-a2.21.

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Andersen, Martin N., Søren-Peter Olesen, and Hanne B. Rasmussen. "Kv7.1 surface expression is regulated by epithelial cell polarization." American Journal of Physiology-Cell Physiology 300, no. 4 (April 2011): C814—C824. http://dx.doi.org/10.1152/ajpcell.00390.2010.

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The potassium channel KV7.1 is expressed in the heart where it contributes to the repolarization of the cardiac action potential. In addition, KV7.1 is expressed in epithelial tissues where it plays a role in salt and water transport. Mutations in the kcnq1 gene can lead to long QT syndrome and deafness, and several mutations have been described as trafficking mutations. To learn more about the basic mechanisms that regulate KV7.1 surface expression, we have investigated the trafficking of KV7.1 during the polarization process of the epithelial cell line Madin-Darby Canine Kidney (MDCK) using a modified version of the classical calcium switch. We discovered that KV7.1 exhibits a very dynamic localization pattern during the calcium switch. When MDCK cells are kept in low calcium medium, KV7.1 is mainly observed at the plasma membrane. During the first hours of the switch, KV7.1 is removed from the plasma membrane and an intracellular accumulation in the endoplasmic reticulum (ER) is observed. The channel is retained in the ER until the establishment of the lateral membranes at which point KV7.1 is released from the ER and moves to the plasma membrane. Our data furthermore suggest that while the removal of KV7.1 from the cell surface and its accumulation in the ER could involve activation of protein kinase C, the subsequent release of KV7.1 from the ER depends on phosphoinositide 3-kinase (PI3K) activation. In conclusion, our results demonstrate that KV7.1 surface expression is regulated by signaling mechanisms involved in epithelial cell polarization in particular signaling cascades involving protein kinase C and PI3K.

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Telezhkin, Vsevolod, Alison M. Thomas, Stephen C. Harmer, Andrew Tinker, and David A. Brown. "A basic residue in the proximal C-terminus is necessary for efficient activation of the M-channel subunit Kv7.2 by PI(4,5)P2." Pflügers Archiv - European Journal of Physiology 465, no. 7 (January 6, 2013): 945–53. http://dx.doi.org/10.1007/s00424-012-1199-3.

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Andersen, Martin Nybo, Katarzyna Krzystanek, Frederic Petersen, Sofia Hammami Bomholtz, Søren-Peter Olesen, Hugues Abriel, Thomas Jespersen, and Hanne Borger Rasmussen. "A Phosphoinositide 3-Kinase (PI3K)-serum- and glucocorticoid-inducible Kinase 1 (SGK1) Pathway Promotes Kv7.1 Channel Surface Expression by Inhibiting Nedd4-2 Protein." Journal of Biological Chemistry 288, no. 52 (November 8, 2013): 36841–54. http://dx.doi.org/10.1074/jbc.m113.525931.

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Dai, Shuiping, Duane D. Hall, and Johannes W. Hell. "Supramolecular Assemblies and Localized Regulation of Voltage-Gated Ion Channels." Physiological Reviews 89, no. 2 (April 2009): 411–52. http://dx.doi.org/10.1152/physrev.00029.2007.

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This review addresses the localized regulation of voltage-gated ion channels by phosphorylation. Comprehensive data on channel regulation by associated protein kinases, phosphatases, and related regulatory proteins are mainly available for voltage-gated Ca2+ channels, which form the main focus of this review. Other voltage-gated ion channels and especially Kv7.1-3 (KCNQ1-3), the large- and small-conductance Ca2+-activated K+ channels BK and SK2, and the inward-rectifying K+ channels Kir3 have also been studied to quite some extent and will be included. Regulation of the L-type Ca2+ channel Cav1.2 by PKA has been studied most thoroughly as it underlies the cardiac fight-or-flight response. A prototypical Cav1.2 signaling complex containing the β2 adrenergic receptor, the heterotrimeric G protein Gs, adenylyl cyclase, and PKA has been identified that supports highly localized via cAMP. The type 2 ryanodine receptor as well as AMPA- and NMDA-type glutamate receptors are in close proximity to Cav1.2 in cardiomyocytes and neurons, respectively, yet independently anchor PKA, CaMKII, and the serine/threonine phosphatases PP1, PP2A, and PP2B, as is discussed in detail. Descriptions of the structural and functional aspects of the interactions of PKA, PKC, CaMKII, Src, and various phosphatases with Cav1.2 will include comparisons with analogous interactions with other channels such as the ryanodine receptor or ionotropic glutamate receptors. Regulation of Na+ and K+ channel phosphorylation complexes will be discussed in separate papers. This review is thus intended for readers interested in ion channel regulation or in localization of kinases, phosphatases, and their upstream regulators.

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Amin, Ahmad S., John R. Giudicessi, Anke J. Tijsen, Anne M. Spanjaart, Yolan J. Reckman, Christine A. Klemens, Michael W. Tanck, et al. "Variants in the 3′ untranslated region of the KCNQ1-encoded Kv7.1 potassium channel modify disease severity in patients with type 1 long QT syndrome in an allele-specific manner." European Heart Journal 33, no. 6 (December 23, 2011): 714–23. http://dx.doi.org/10.1093/eurheartj/ehr473.

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Giudicessi, J. R., A. S. Amin, A. J. Tjisen, C. A. Klemens, J. D. Kapplinger, N. Hofman, Y. Pinto, A. A. Wilde, and M. J. Ackerman. "Modification of Disease Severity by Functional Variants in the 3′ Untranslated Region of the KCNQ1-Encoded Kv7.1 Channel is Most Pronounced in Patients Harboring Dominant-Negative LQT1-Causative Mutations." Heart Rhythm 8, no. 11 (November 2011): 1827. http://dx.doi.org/10.1016/j.hrthm.2011.09.050.

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Haick, Jennifer M., Lioubov I. Brueggemann, Leanne L. Cribbs, Mitchell F. Denning, Jeffrey Schwartz, and Kenneth L. Byron. "PKC-dependent regulation of Kv7.5 channels by the bronchoconstrictor histamine in human airway smooth muscle cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 312, no. 6 (June 1, 2017): L822—L834. http://dx.doi.org/10.1152/ajplung.00567.2016.

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Kv7 potassium channels have recently been found to be expressed and functionally important for relaxation of airway smooth muscle. Previous research suggests that native Kv7 currents are inhibited following treatment of freshly isolated airway smooth muscle cells with bronchoconstrictor agonists, and in intact airways inhibition of Kv7 channels is sufficient to induce bronchiolar constriction. However, the mechanism by which Kv7 currents are inhibited by bronchoconstrictor agonists has yet to be elucidated. In the present study, native Kv7 currents in cultured human trachealis smooth muscle cells (HTSMCs) were observed to be inhibited upon treatment with histamine; inhibition of Kv7 currents was associated with membrane depolarization and an increase in cytosolic Ca2+ ([Ca2+]cyt). The latter response was inhibited by verapamil, a blocker of L-type voltage-sensitive Ca2+ channels (VSCCs). Protein kinase C (PKC) has been implicated as a mediator of bronchoconstrictor actions, although the targets of PKC are not clearly established. We found that histamine treatment significantly and dose-dependently suppressed currents through overexpressed wild-type human Kv7.5 (hKv7.5) channels in cultured HTSMCs, and this effect was inhibited by the PKC inhibitor Ro-31-8220 (3 µM). The PKC-dependent suppression of hKv7.5 currents corresponded with a PKC-dependent increase in hKv7.5 channel phosphorylation. Knocking down or inhibiting PKCα, or mutating hKv7.5 serine 441 to alanine, abolished the inhibitory effects of histamine on hKv7.5 currents. These findings provide the first evidence linking PKC activation to suppression of Kv7 currents, membrane depolarization, and Ca2+ influx via L-type VSCCs as a mechanism for histamine-induced bronchoconstriction.

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Sheng, Zhao-Fu, Hua Zhang, PeiRu Zheng, Shanyan Chen, Zezong Gu, Jing-Jing Zhou, Jeffery G. Phaup, et al. "Impaired Kv7 channel activity in the central amygdala contributes to elevated sympathetic outflow in hypertension." Cardiovascular Research, February 14, 2021. http://dx.doi.org/10.1093/cvr/cvab031.

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Abstract Aims Elevated sympathetic outflow is associated with primary hypertension. However, the mechanisms involved in heightened sympathetic outflow in hypertension are unclear. The central amygdala (CeA) regulates autonomic components of emotions through projections to the brainstem. The neuronal Kv7 channel is a non-inactivating voltage-dependent K+ channel encoded by KCNQ2/3 genes involved in stabilizing the neuronal membrane potential and regulating neuronal excitability. In this study, we investigated if altered Kv7 channel activity in the CeA contributes to heightened sympathetic outflow in hypertension. Methods and results The mRNA and protein expression levels of Kv7.2/Kv7.3 in the CeA were significantly reduced in spontaneously hypertensive rats (SHRs) compared with Wistar–Kyoto (WKY) rats. Lowering blood pressure with coeliac ganglionectomy in SHRs did not alter Kv7.2 and Kv7.3 channel expression levels in the CeA. Fluospheres were injected into the rostral ventrolateral medulla (RVLM) to retrogradely label CeA neurons projecting to the RVLM (CeA–RVLM neurons). Kv7 channel currents recorded from CeA–RVLM neurons in brain slices were much smaller in SHRs than in WKY rats. Furthermore, the basal firing activity of CeA–RVLM neurons was significantly greater in SHRs than in WKY rats. Bath application of specific Kv7 channel blocker 10, 10-bis (4-pyridinylmethyl)-9(10H)-anthracnose (XE-991) increased the excitability of CeA–RVLM neurons in WKY rats, but not in SHRs. Microinjection of XE-991 into the CeA increased arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), while microinjection of Kv7 channel opener QO-58 decreased ABP and RSNA, in anaesthetized WKY rats but not SHRs. Conclusions Our findings suggest that diminished Kv7 channel activity in the CeA contributes to elevated sympathetic outflow in primary hypertension. This novel information provides new mechanistic insight into the pathogenesis of neurogenic hypertension.

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Celentano, Camilla, Lidia Carotenuto, Francesco Miceli, Giusy Carleo, Brunella Corrado, Giulia Baroli, Stefania Iervolino, Raffaele Vecchione, Maurizio Taglialatela, and Vincenzo Barrese. "Kv7 CHANNELS ACTIVATION REDUCES BRAIN ENDOTHELIAL CELLS PERMEABILITY AND PREVENTS KAINIC ACID INDUCED BLOOD BRAIN BARRIER DAMAGE." American Journal of Physiology-Cell Physiology, January 29, 2024. http://dx.doi.org/10.1152/ajpcell.00709.2023.

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Ion channels in the blood brain barrier (BBB) play a main role in controlling interstitial fluid composition and cerebral blood flow, and their dysfunction contributes to the disruption of the BBB occurring in many neurological diseases such as epilepsy. In this study, using morphological and functional approaches, we evaluated the expression and role in the BBB of Kv7 channels, a family of voltage-gated potassium channels including five members (Kv7.1-5) that play a major role in the regulation of cell excitability and transmembrane flux of potassium ions. Immunofluorescence experiments showed that Kv7.1, Kv7.4 and Kv7.5 were expressed in rat brain microvessels (BMVs), as well as well as brain primary- and clonal (BEND-3) endothelial cells (ECs). Kv7.5 localized at the cell-to cell junction sites, whereas Kv7.4 was also found in pericytes. The Kv7 activator retigabine increased trans-endothelial electrical resistance (TEER) in both primary ECs and BEND-3 cells; moreover, retigabine reduced paracellular dextran flux in BEND-3 cells. These effects were prevented by the selective Kv7 blocker XE-991. Exposure to retigabine also hyperpolarized cell membrane and increased tight junctions (TJs) integrity in BEND-3 cells. BMVs from rats treated with kainic acid (KA) showed a disruption of TJs and a selective reduction of Kv7.5 expression. In BEND-3 cells, retigabine prevented the increase of cell permeability and the reduction of TJs integrity induced by KA. Overall, these findings demonstrate that Kv7 channels are expressed in the BBB, where they modulate barrier properties both in physiological and pathological conditions.

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Varghese, Nissi, Bruno Moscoso, Ana Chavez, Kristen Springer, Erika Ortiz, Heun Soh, Sabato Santaniello, Atul Maheshwari, and Anastasios V. Tzingounis. "KCNQ2/3 Gain-of-Function Variants and Cell Excitability: Differential Effects in CA1 vs. L2/3 pyramidal neurons." Journal of Neuroscience, August 22, 2023, JN—RM—0980–23. http://dx.doi.org/10.1523/jneurosci.0980-23.2023.

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Gain-of-function pathogenic variants in the potassium channels KCNQ2 (KV7.2) and KCNQ3 (KV7.3) lead to hyperexcitability disorders such as epilepsy and autism spectrum disorders. However, the underlying cellular mechanisms of how these variants impair forebrain function are unclear. Here, we show that the R201C variant in KCNQ2 has opposite effects on the excitability of two types of mouse pyramidal neurons of either sex, causing hyperexcitability in layer 2/3 (L2/3) pyramidal neurons and hypoexcitability in CA1 pyramidal neurons. Similarly, the homologous R231C variant in KCNQ3 leads to hyperexcitability in L2/3 pyramidal neurons and hypoexcitability in CA1 pyramidal neurons. However, the effects of KCNQ3 gain of function on excitability are specific to superficial CA1 pyramidal neurons. These findings reveal a new level of complexity in the function of KCNQ2 and KCNQ3 channels in the forebrain and provide a framework for understanding the effects of gain-of-function variants and potassium channels in the brain.Significance StatementKCNQ2/3 gain-of-function (GOF) variants lead to severe forms of neurodevelopmental disorders, but the mechanisms by which these channels affect neuronal activity are poorly understood. In this study, using a series of transgenic mice we demonstrate that the same KCNQ2/3 GOF variants can lead to either hyperexcitability or hypoexcitability in different types of pyramidal neurons (CA1 vs L2/3). Additionally, we show that expression of the recurrent KCNQ2 GOF variant R201C in forebrain pyramidal neurons could lead to seizures and SUDEP. Our data suggest that the effects of KCNQ2/3 GOF variants depend on specific cell types and brain regions, possibly accounting for the diverse range of phenotypes observed in individuals with KCNQ2/3 GOF variants.

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Li, Shuang, Bopanna I. Kalappa, and Thanos Tzounopoulos. "Noise-induced plasticity of KCNQ2/3 and HCN channels underlies vulnerability and resilience to tinnitus." eLife 4 (August 27, 2015). http://dx.doi.org/10.7554/elife.07242.

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Vulnerability to noise-induced tinnitus is associated with increased spontaneous firing rate in dorsal cochlear nucleus principal neurons, fusiform cells. This hyperactivity is caused, at least in part, by decreased Kv7.2/3 (KCNQ2/3) potassium currents. However, the biophysical mechanisms underlying resilience to tinnitus, which is observed in noise-exposed mice that do not develop tinnitus (non-tinnitus mice), remain unknown. Our results show that noise exposure induces, on average, a reduction in KCNQ2/3 channel activity in fusiform cells in noise-exposed mice by 4 days after exposure. Tinnitus is developed in mice that do not compensate for this reduction within the next 3 days. Resilience to tinnitus is developed in mice that show a re-emergence of KCNQ2/3 channel activity and a reduction in HCN channel activity. Our results highlight KCNQ2/3 and HCN channels as potential targets for designing novel therapeutics that may promote resilience to tinnitus.

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Perez-Vizcaino, Francisco, Angel Cogolludo, and Gema Mondejar-Parreño. "Transcriptomic profile of cationic channels in human pulmonary arterial hypertension." Scientific Reports 11, no. 1 (August 4, 2021). http://dx.doi.org/10.1038/s41598-021-95196-z.

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AbstractThe dysregulation of K+ channels is a hallmark of pulmonary arterial hypertension (PAH). Herein, the channelome was analyzed in lungs of patients with PAH in a public transcriptomic database. Sixty six (46%) mRNA encoding cationic channels were dysregulated in PAH with most of them downregulated (83%). The principal component analysis indicated that dysregulated cationic channel expression is a signature of the disease. Changes were very similar in idiopathic, connective tissue disease and congenital heart disease associated PAH. This analysis 1) is in agreement with the widely recognized pathophysiological role of TASK1 and KV1.5, 2) supports previous preliminary reports pointing to the dysregulation of several K+ channels including the downregulation of KV1.1, KV1.4, KV1.6, KV7.1, KV7.4, KV9.3 and TWIK2 and the upregulation of KCa1.1 and 3) points to other cationic channels dysregulated such as Kv7.3, TALK2, CaV1 and TRPV4 which might play a pathophysiological role in PAH. The significance of other changes found in Na+ and TRP channels remains to be investigated.

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Tracy, Gregory C., Angelina R. Wilton, Justin S. Rhodes, and Hee Jung Chung. "Heterozygous Deletion of Epilepsy Gene KCNQ2 Has Negligible Effects on Learning and Memory." Frontiers in Behavioral Neuroscience 16 (July 19, 2022). http://dx.doi.org/10.3389/fnbeh.2022.930216.

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Neuronal Kv7/Potassium Voltage-Gated Channel Subfamily Q (KCNQ) potassium channels underlie M-current that potently suppresses repetitive and burst firing of action potentials (APs). They are mostly heterotetramers of Kv7.2 and Kv7.3 subunits in the hippocampus and cortex, the brain regions important for cognition and behavior. Underscoring their critical roles in inhibiting neuronal excitability, autosomal dominantly inherited mutations in Potassium Voltage-Gated Channel Subfamily Q Member 2 (KCNQ2) and Potassium Voltage-Gated Channel Subfamily Q Member 3 (KCNQ3) genes are associated with benign familial neonatal epilepsy (BFNE) in which most seizures spontaneously remit within months without cognitive deficits. De novo mutations in KCNQ2 also cause epileptic encephalopathy (EE), which is characterized by persistent seizures that are often drug refractory, neurodevelopmental delay, and intellectual disability. Heterozygous expression of EE variants of KCNQ2 is recently shown to induce spontaneous seizures and cognitive deficit in mice, although it is unclear whether this cognitive deficit is caused directly by Kv7 disruption or by persistent seizures in the developing brain as a consequence of Kv7 disruption. In this study, we examined the role of Kv7 channels in learning and memory by behavioral phenotyping of the KCNQ2+/− mice, which lack a single copy of KCNQ2 but dos not display spontaneous seizures. We found that both KCNQ2+/− and wild-type (WT) mice showed comparable nociception in the tail-flick assay and fear-induced learning and memory during a passive inhibitory avoidance (IA) test and contextual fear conditioning (CFC). Both genotypes displayed similar object location and recognition memory. These findings together provide evidence that heterozygous loss of KCNQ2 has minimal effects on learning or memory in mice in the absence of spontaneous seizures.

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Li, De-Pei, Zhao-Fu Sheng, Hua Zhang, and Peiru Zheng. "Dysfunction of M channels in the insular cortex is involved in pathogenesis of primary hypertension." Physiology 39, S1 (May 2024). http://dx.doi.org/10.1152/physiol.2024.39.s1.1993.

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Heightened sympathetic nerve activity is critically involved in the pathogenesis of primary hypertension. However, the sources driving increased sympathetic vasomotor tone remain unclear. The posterior insular cortex (PIC) is a brain region involved in regulating blood pressure and sympathetic tone. Neurons in the PIC project to the rostral ventrolateral medulla (RVLM), a key brain stem region in regulating sympathetic nerve activity and blood pressure. The non-inactivating voltage-dependent K+ channels, M channels (Kv7/KCNQ channel family) encoded by KCNQ2/3 genes, play a unique role in stabilizing the neuronal membrane potential and regulating neuronal excitability. Here, we determined if the M channel activity of neurons in the PIC is altered in a primary hypertension. Compared with Wistar-Kyoto (WKY) rats, the mRNA and protein expression levels of Kv7.2/Kv7.3 in the PIC tissue were significantly reduced in spontaneously hypertensive rats (SHRs). Microinjection of M channel blocker 10, 10-bis (4-pyridinylmethyl)-9(10H)-anthracnose (XE-991) into the PIC increased arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) in anesthetized WKY rats, while induced minimal changes of ABP and RSNA in SHRs. M currents recorded from PIC neurons in brain slices labeled by retrograde tracer, Fluospheres, injected into the RVLM were significantly smaller in SHRs than in WKY rats. Furthermore, bath application of specific M channel blocker XE-991 increased the firing rate of PIC-RVLM output neurons in WKY rats while caused a minimal increase in firing rate of PIC-RVLM output neurons in SHRs. In addition, M currents recorded from PIC-RVLM output neurons in SHRs were significantly smaller than those recorded from WKY rats. These data suggest that M channel activity is diminished in PIC-RVLM output neurons in SHRs, and the diminished Kv7 channel activity contributes to elevated sympathetic outflow in primary hypertension. This novel information provides new a mechanistic insight into the pathogenesis of neurogenic hypertension. Supported by grants from National Institutes of Health (HL139523, HL142133, and HL159157 to DPL). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

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French, Jacqueline A., Roger J. Porter, Emilio Perucca, Martin J. Brodie, Michael A. Rogawski, Simon Pimstone, Ernesto Aycardi, et al. "Efficacy and Safety of XEN1101, a Novel Potassium Channel Opener, in Adults With Focal Epilepsy." JAMA Neurology, October 9, 2023. http://dx.doi.org/10.1001/jamaneurol.2023.3542.

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ImportanceMany patients with focal epilepsy experience seizures despite treatment with currently available antiseizure medications (ASMs) and may benefit from novel therapeutics.ObjectiveTo evaluate the efficacy and safety of XEN1101, a novel small-molecule selective Kv7.2/Kv7.3 potassium channel opener, in the treatment of focal-onset seizures (FOSs).Design, Setting, and ParticipantsThis phase 2b, randomized, double-blind, placebo-controlled, parallel-group, dose-ranging adjunctive trial investigated XEN1101 over an 8-week treatment period from January 30, 2019, to September 2, 2021, and included a 6-week safety follow-up. Adults experiencing 4 or more monthly FOSs while receiving stable treatment (1-3 ASMs) were enrolled at 97 sites in North America and Europe.InterventionsPatients were randomized 2:1:1:2 to receive XEN1101, 25, 20, or 10 mg, or placebo with food once daily for 8 weeks. Dosage titration was not used. On completion of the double-blind phase, patients were offered the option of entering an open-label extension (OLE). Patients not participating in the OLE had follow-up safety visits (1 and 6 weeks after the final dose).Main Outcomes and MeasuresThe primary efficacy end point was the median percent change from baseline in monthly FOS frequency. Treatment-emergent adverse events (TEAEs) were recorded and comprehensive laboratory assessments were made. Modified intention-to-treat analysis was conducted.ResultsA total of 325 patients who were randomized and treated were included in the safety analysis; 285 completed the 8-week double-blind phase. In the 325 patients included, mean (SD) age was 40.8 (13.3) years, 168 (51.7%) were female, and 298 (91.7%) identified their race as White. Treatment with XEN1101 was associated with seizure reduction in a robust dose-response manner. The median (IQR) percent reduction from baseline in monthly FOS frequency was 52.8% (P &lt; .001 vs placebo; IQR, −80.4% to −16.9%) for 25 mg, 46.4% (P &lt; .001 vs placebo; IQR, −76.7% to −14.0%) for 20 mg, and 33.2% (P = .04 vs placebo; IQR, −61.8% to 0.0%) for 10 mg, compared with 18.2% (IQR, −37.3% to 7.0%) for placebo. XEN1101 was generally well tolerated and TEAEs were similar to those of commonly prescribed ASMs, and no TEAEs leading to death were reported.Conclusions and RelevanceThe efficacy and safety findings of this clinical trial support the further clinical development of XEN1101 for the treatment of FOSs.Trial RegistrationClinicalTrials.gov Identifier: NCT03796962

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Pant, Shashank, Jiaren Zhang, Eung Chang Kim, Kin Lam, Hee Jung Chung, and Emad Tajkhorshid. "PIP2-dependent coupling of voltage sensor and pore domains in Kv7.2 channel." Communications Biology 4, no. 1 (October 14, 2021). http://dx.doi.org/10.1038/s42003-021-02729-3.

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AbstractPhosphatidylinositol-4,5-bisphosphate (PIP2) is a signaling lipid which regulates voltage-gated Kv7/KCNQ potassium channels. Altered PIP2 sensitivity of neuronal Kv7.2 channel is involved in KCNQ2 epileptic encephalopathy. However, the molecular action of PIP2 on Kv7.2 gating remains largely elusive. Here, we use molecular dynamics simulations and electrophysiology to characterize PIP2 binding sites in a human Kv7.2 channel. In the closed state, PIP2 localizes to the periphery of the voltage-sensing domain (VSD). In the open state, PIP2 binds to 4 distinct interfaces formed by the cytoplasmic ends of the VSD, the gate, intracellular helices A and B and their linkers. PIP2 binding induces bilayer-interacting conformation of helices A and B and the correlated motion of the VSD and the pore domain, whereas charge-neutralizing mutations block this coupling and reduce PIP2 sensitivity of Kv7.2 channels by disrupting PIP2 binding. These findings reveal the allosteric role of PIP2 in Kv7.2 channel activation.

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Pant, Shashank, Jiaren Zhang, Eung Chang Kim, Kin Lam, Hee Jung Chung, and Emad Tajkhorshid. "PIP2-dependent coupling of voltage sensor and pore domains in Kv7.2 channel." Communications Biology 4, no. 1 (October 14, 2021). http://dx.doi.org/10.1038/s42003-021-02729-3.

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AbstractPhosphatidylinositol-4,5-bisphosphate (PIP2) is a signaling lipid which regulates voltage-gated Kv7/KCNQ potassium channels. Altered PIP2 sensitivity of neuronal Kv7.2 channel is involved in KCNQ2 epileptic encephalopathy. However, the molecular action of PIP2 on Kv7.2 gating remains largely elusive. Here, we use molecular dynamics simulations and electrophysiology to characterize PIP2 binding sites in a human Kv7.2 channel. In the closed state, PIP2 localizes to the periphery of the voltage-sensing domain (VSD). In the open state, PIP2 binds to 4 distinct interfaces formed by the cytoplasmic ends of the VSD, the gate, intracellular helices A and B and their linkers. PIP2 binding induces bilayer-interacting conformation of helices A and B and the correlated motion of the VSD and the pore domain, whereas charge-neutralizing mutations block this coupling and reduce PIP2 sensitivity of Kv7.2 channels by disrupting PIP2 binding. These findings reveal the allosteric role of PIP2 in Kv7.2 channel activation.

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Klemz, Alexander, Florian Wildner, Ecem Tütüncü, and Zoltan Gerevich. "Regulation of Hippocampal Gamma Oscillations by Modulation of Intrinsic Neuronal Excitability." Frontiers in Neural Circuits 15 (January 26, 2022). http://dx.doi.org/10.3389/fncir.2021.778022.

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Ion channels activated around the subthreshold membrane potential determine the likelihood of neuronal firing in response to synaptic inputs, a process described as intrinsic neuronal excitability. Long-term plasticity of chemical synaptic transmission is traditionally considered the main cellular mechanism of information storage in the brain; however, voltage- and calcium-activated channels modulating the inputs or outputs of neurons are also subjects of plastic changes and play a major role in learning and memory formation. Gamma oscillations are associated with numerous higher cognitive functions such as learning and memory, but our knowledge of their dependence on intrinsic plasticity is by far limited. Here we investigated the roles of potassium and calcium channels activated at near subthreshold membrane potentials in cholinergically induced persistent gamma oscillations measured in the CA3 area of rat hippocampal slices. Among potassium channels, which are responsible for the afterhyperpolarization in CA3 pyramidal cells, we found that blockers of SK (KCa2) and KV7.2/7.3 (KCNQ2/3), but not the BK (KCa1.1) and IK (KCa3.1) channels, increased the power of gamma oscillations. On the contrary, activators of these channels had an attenuating effect without affecting the frequency. Pharmacological blockade of the low voltage-activated T-type calcium channels (CaV3.1–3.3) reduced gamma power and increased the oscillation peak frequency. Enhancement of these channels also inhibited the peak power without altering the frequency of the oscillations. The presented data suggest that voltage- and calcium-activated ion channels involved in intrinsic excitability strongly regulate the power of hippocampal gamma oscillations. Targeting these channels could represent a valuable pharmacological strategy against cognitive impairment.

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Yang, Gui-mei, Fu-yun Tian, Yan-wen Shen, Chuan-yan Yang, Hui Yuan, Ping Li, and Zhao-bing Gao. "Functional characterization and in vitro pharmacological rescue of KCNQ2 pore mutations associated with epileptic encephalopathy." Acta Pharmacologica Sinica, March 17, 2023. http://dx.doi.org/10.1038/s41401-023-01073-y.

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AbstractMutations in the KCNQ2 gene encoding KV7.2 subunit that mediates neuronal M-current cause a severe form of developmental and epileptic encephalopathy (DEE). Electrophysiological evaluation of KCNQ2 mutations has been proved clinically useful in improving outcome prediction and choosing rational anti-seizure medications (ASMs). In this study we described the clinical characteristics, electrophysiological phenotypes and the in vitro response to KCNQ openers of five KCNQ2 pore mutations (V250A, N258Y, H260P, A265T and G290S) from seven patients diagnosed with KCNQ2-DEE. The KCNQ2 variants were transfected into Chinese hamster ovary (CHO) cells alone, in combination with KCNQ3 (1:1) or with wild-type KCNQ2 (KCNQ2-WT) and KCNQ3 in a ratio of 1:1:2, respectively. Their expression and electrophysiological function were assessed. When transfected alone or in combination with KCNQ3, none of these mutations affected the membrane expression of KCNQ2, but most failed to induce a potassium current except A265T, in which trace currents were observed when co-transfected with KCNQ3. When co-expressed with KCNQ2-WT and KCNQ3 (1:1:2), the currents at 0 mV of these mutations were decreased by 30%-70% compared to the KCNQ2/3 channel, which could be significantly rescued by applying KCNQ openers including the approved antiepileptic drug retigabine (RTG, 10 μM), as well as two candidates subjected to clinical trials, pynegabine (HN37, 1 μM) and XEN1101 (1 μM). These newly identified pathologic variants enrich the KCNQ2-DEE mutation hotspots in the pore-forming domain. This electrophysiological study provides a rational basis for personalized therapy with KCNQ openers in DEE patients carrying loss-of-function (LOF) mutations in KCNQ2.

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JULIANA, CHRISTINE, and DIVA DE LEON. "1745-P: Voltage-Gated K+ Channel Kv7.1 Is an Important Regulator of Insulin Secretion in Normal and Hyperinsulinemic Islets." Diabetes 72, Supplement_1 (June 20, 2023). http://dx.doi.org/10.2337/db23-1745-p.

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Fifty percent of infants with Beckwith-Wiedemann syndrome (BWS), an overgrowth syndrome caused by genetic / epigenetic abnormalities in imprinted genes on chromosome 11p15, have persistent hypoglycemia due to hyperinsulinism (BWS-HI). BWS-HI islets exhibit increased baseline and glucose-stimulated insulin secretion (GSIS) and are responsive to the KATP channel inhibitor glyburide, suggesting it is not caused by impaired KATP channels. KCNQ1 expression, encoding the pore-forming α subunit of voltage-gated K+ channel Kv7.1, is reduced in BWS-HI islets compared to normal islets (3-fold; p = 4.5×10−7) and KCNQ1 loss-of-function mutations in humans are associated with HI. We used genetic and pharmacologic methods to modify Kv7.1 activity and examined changes to insulin secretion. In response to glucose, Kcnq1−/− mice had lower plasma glucose and higher plasma insulin than wild-type controls. Perifusion of Kcnq1−/− pancreatic islets with increasing concentrations of glucose showed that GSIS in these islets was faster and greater than in wild-type islets. The perifusion GSIS responses in normal human, wild-type mouse and Sur1−/− mouse (KATP-HI mouse model) islets with two different Kv7.1 activators (hexachlorophene or ML277) were markedly slower and diminished. In contrast, wild-type mouse islet perifusion with the Kv7.1 inhibitor chromanol 293B strikingly fastened and increased the GSIS response compared to vehicle controls. Membrane potential (Vm) analysis of Kcnq1−/− islets demonstrated that depolarization occurs more quickly during the initiation of insulin secretion compared to wild-type controls. Treatment with Kv7.1 activators resulted in Vm changes in both wild-type mouse and normal human islets compared to controls. Our results reveal the capacity of Kv7.1 to regulate insulin secretion in pancreatic islets and that Kv7.1 is a viable target for development of therapeutics for HI. Disclosure C.Juliana: Research Support; Crinetics Pharmaceuticals, Inc., Twist Bioscience, AmideBio. D.De leon: Consultant; Zealand Pharma A/S, Crinetics Pharmaceuticals, Inc., Eiger BioPharmaceuticals, Hanmi Pharm. Co., Ltd., Research Support; Ultragenix, Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Rezolute, Inc. Funding National Institutes of Health (5R01DK098517-08)

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Trancuccio, A., A. Mazzanti, D. Kukavica, M. Marino, N. Monteforte, R. Bloise, L. Braghieri, et al. "Mutation site-specific risk profile in patients with Type 1 Long QT Syndrome." European Heart Journal 41, Supplement_2 (November 1, 2020). http://dx.doi.org/10.1093/ehjci/ehaa946.0743.

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Abstract Background Type 1 Long QT Syndrome (LQT1) is an arrhythmogenic disorder, caused by loss-of-function mutations on KCNQ1 gene, coding for Kv7.1 potassium channel. Although LQT1 is described as the most benign form of LQTS, patients still experience arrhythmic events and there is an unmet need for personalized risk stratification. Attempts have been made to correlate the location of mutations with outcome, but the results are unequivocal. Purpose We provide in the present study a new mutation site-specific risk profile obtained from a large cohort of LQT1 patients. Methods We gathered data on 963 patients with the diagnosis of LQT1 and divided the Kv7.1 channel into 5 functional regions: the N-terminus (NT), the voltage sensor (VS, including transmembrane segments S1 to S4), the cytoplasmic loops (CL), the pore (PO, including the transmembrane segments S5, S6 and the S5-S6 extracellular linker), the C-terminus (CT). Results We studied 963 LQT1 patients: 518 (54%) females; average age 20±17 years; mean QTc at baseline ECG 465±38ms. During a mean follow-up of 8±7 years, 172 (18%) patients experienced arrhythmic events: 31 (3%) experienced one or more cardiac arrests, while 141 (15%) experienced one or more syncopal spells. We identified 188 different variants in the KCNQ1 gene, with the following distribution: 15 (8%) in the NT, 33 (18%) in the VS, 27 (14%) in the CL, 43 (23%) in the PO, 70 (37%) in the CT. The frequency of pathogenic variants per number of amino acids (a.a.) was higher in the CL region, as compared to the other domains (1 mutation every 1.4 a.a.). The duration of QTc interval was significantly longer for patients with mutations in the PO region (473±40 ms) and in the CL region (468±38 ms) as compared to the other regions (p<0.01). Importantly, in a multivariate analysis PO and CL regions were associated with a higher probability of experiencing arrhythmic events (OR 2.89, 95% CI 1.95–4.29, p=0.019 and OR 1.61, 95% CI 1.0–2.49, p=0.05, respectively. Figure) than the other regions. Interestingly, the risk was independent from QTc interval duration. Conclusions Mutations affecting the PO and the CL region of the Kv7.1. channel are associated with a higher probability of experiencing arrhythmic events. This finding is clinically relevant, because it will allow for a more personalized, mutation site-specific risk stratification. Mutation site and arrhythmic events Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Italian Ministry of Research and University Dipartimenti di Eccellenza 2018–2022 grant to the Molecular Medicine Department (University of Pavia)

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Liao, Qian-Qian, Qing-Qing Dong, Hui Zhang, Hua-Pan Shu, Yu-Chi Tu, and Li-Jun Yao. "Contributions of SGK3 to transporter-related diseases." Frontiers in Cell and Developmental Biology 10 (December 1, 2022). http://dx.doi.org/10.3389/fcell.2022.1007924.

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Serum- and glucocorticoid-induced kinase 3 (SGK3), which is ubiquitously expressed in mammals, is regulated by estrogens and androgens. SGK3 is activated by insulin and growth factors through signaling pathways involving phosphatidylinositol-3-kinase (PI3K), 3-phosphoinositide-dependent kinase-1 (PDK-1), and mammalian target of rapamycin complex 2 (mTORC2). Activated SGK3 can activate ion channels (TRPV5/6, SOC, Kv1.3, Kv1.5, Kv7.1, BKCa, Kir2.1, Kir2.2, ENaC, Nav1.5, ClC-2, and ClC Ka), carriers and receptors (Npt2a, Npt2b, NHE3, GluR1, GluR6, SN1, EAAT1, EAAT2, EAAT4, EAAT5, SGLT1, SLC1A5, SLC6A19, SLC6A8, and NaDC1), and Na+/K+-ATPase, promoting the transportation of calcium, phosphorus, sodium, glucose, and neutral amino acids in the kidney and intestine, the absorption of potassium and neutral amino acids in the renal tubules, the transportation of glutamate and glutamine in the nervous system, and the transportation of creatine. SGK3-sensitive transporters contribute to a variety of physiological and pathophysiological processes, such as maintaining calcium and phosphorus homeostasis, hydro-salinity balance and acid-base balance, cell proliferation, muscle action potential, cardiac and neural electrophysiological disturbances, bone density, intestinal nutrition absorption, immune function, and multiple substance metabolism. These processes are related to kidney stones, hypophosphorous rickets, multiple syndromes, arrhythmia, hypertension, heart failure, epilepsy, Alzheimer’s disease, amyotrophic lateral sclerosis, glaucoma, ataxia idiopathic deafness, and other diseases.

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Svecova, O., R. Kula, L. Chmelikova, J. Hosek, I. Synkova, T. Novotny, and M. Bebarova. "Clinical, genetic and functional analysis of R562S-Kv7.1 mutation associated with long QT syndrome type 1." EP Europace 23, Supplement_3 (May 1, 2021). http://dx.doi.org/10.1093/europace/euab116.560.

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Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Ministry of Education, Youth and Sports of the Czech Republic Introduction Loss-of-function variants of the KCNQ1 gene are associated with life-threatening arrhythmogenic long QT syndrome type 1 (LQT1). This gene encodes structure of the slow delayed rectifier potassium channel (IKs). Some functional characteristics of the C-terminal KCNQ1 variant c.1686G > C (p.R562S) have been recently described [1]. However, accumulation of the current under beta-adrenergic stimulation, essential for shortening the action potential duration during exercise, have not been tested. Purpose The aim of this study was to analyse clinical and genetic characteristics of the R562S variant in our patients and to investigate impact of the variant on IKs channel function with a special focus on reactivity of the channels on beta-adrenergic stimulation. Methods The clinical diagnosis was established according to ESC Guidelines including QTc analysis at rest and after exercise. The molecular genetics diagnostics followed according to current practices (the massive parallel sequencing since 2016). The biophysical analysis was performed on Chinese hamster ovary cells (CHO) by the whole cell patch clamp technique at 37 °C. CHO cells were transiently transfected with wild type (WT) and/or R562S human IKs channels (KCNQ1/KCNE1/Yotiao, 1:2:4). Cyclic adenosine monophosphate (cAMP, 200 µM) and okadaic acid (OA, 0.2 µM) in the pipette solution were used to simulate the beta-adrenergic stimulation. In the confocal microscopy experiments, expression of Yotiao was omitted and GFP-tagged KCNQ1 was used. Results The variant R562S-Kv7.1 has been identified in 7 heterozygous carriers from 3 putatively unrelated families in the Czech Republic. The genotype was associated with long QT syndrome phenotype (prolonged QTc, symptoms including syncopes and aborted cardiac arrest) in some of the carriers. The basic functional analysis proved that both homozygous and heterozygous R562S channels are expressed on the cell membrane (confocal microscopy) and carry IKs (whole cell patch clamp) which agrees with the recently published data on this variant. Importantly, reactivity on beta-adrenergic stimulation was absent in both homozygous and heterozygous R562S channels (n = 14 and 8, respectively), but present in the wild-type channels (increase by 51.4 ± 11.1 % at 120-s cAMP/OA diffusion; n = 12). Conclusions The R562S-Kv7.1 variant may be a founder LQT1 variant in our region which will be further investigated in the future. This variant impairs response of IKs channel to beta-adrenergic stimulation. Absence of this essential regulation may considerably aggravate the channel dysfunction and, thus, may result in life-threatening arrhythmias in R562S carriers during exercise.

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Bomholtz, S. H., R. Simo-Vicens, L. Abildgaard, N. G. Edvardsson, U. S. Soerensen, M. Grunnet, J. G. Diness, and B. H. Bentzen. "P699Mechanisms of action of the small conductance Ca2+-activated K+-channel modulator AP30663, a novel compound being developed for treatment of atrial fibrillation in man." European Heart Journal 40, Supplement_1 (October 1, 2019). http://dx.doi.org/10.1093/eurheartj/ehz747.0304.

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Abstract Background Small conductance Ca2+-activated K+-channels (SK-channels) are a promising new atrial selective target for treatment of atrial fibrillation (AF). AP30663 is a small molecule inhibitor of SK-channels that is effective in converting vernakalant-resistant AF in tachy-paced pigs. Detailed understanding of the molecular mechanism of AP30663 is important for the development of SK channel inhibition for use in man. Purpose To establish the electrophysiological profile, mechanism of action and efficacy in prolonging atrial refractoriness ex vivo of AP30663. Methods AP30663 potency and mechanism of action were established by whole cell and inside-out patch clamp recordings of expressed SK channels. The ion channel selectivity profile of AP30663 was investigated on heterologous expressed channels. Effects of AP30663 or vehicle (DMSO) on atrial refractoriness (AERP) and ventricular repolarization (QTcB) were investigated on isolated perfused guinea pig hearts. Results AP30663 was found to be a selective negative allosteric modulator of SK channels (IC50=0.77±x0.13 μM) with no or minor effects on a panel of other cardiac ion channels, including hERG/KV11.1, (IKr), KV7.1/KCNE1 (IKs), KV4.3/KChiP2 (Ito), Kir2.1 (IK1), Kir3.1/Kir3.4 (IKACh), KV1.5 (IKur), NaV1.5 (INa) and CaV1.2 (ICa). AP30663 inhibited the SK-channel by right-shifting the calcium activation curve of the SK-channel (the EC50 of Ca2+ increased from 0.43±0.02 μM (control, n=6) to 1.37±0.05 μM (in the presence of 7μM AP30663, n=6). In isolated guinea pig hearts, administration of vehicle had no effect on AERP or QTcB. AP30663 significantly prolonged the AERP in 3 μM (to 131±6% of baseline) and 10 μM (to 165±3% of baseline) without any effects on the QTcB. Conclusion AP30663 is a selective negative allosteric modulator of SK channels, acting by means of shifting the calcium dependence of SK-channel activation. AP30663 prolonged atrial refractoriness without affecting the QT-interval in isolated perfused heart preparations. These properties support continued development of AP30663 for treatment of AF in man. Acknowledgement/Funding Innovation Fund Denmark, Wellcome Trust

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Kato, Koichi, Holly M. Isbell, Véronique Fressart, Isabelle Denjoy, Amal Debbiche, Hideki Itoh, Jacques Poinsot, et al. "Novel CALM3 Variant Causing Calmodulinopathy With Variable Expressivity in a 4-Generation Family." Circulation: Arrhythmia and Electrophysiology 15, no. 3 (March 2022). http://dx.doi.org/10.1161/circep.121.010572.

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Background: CaM (calmodulin), encoded by 3 separate genes ( CALM1 , CALM2 , and CALM3 ), is a multifunctional Ca 2+ -binding protein involved in many signal transduction events including ion channel regulation. CaM variants may present with early-onset long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia, or sudden cardiac death. Most reported variants occurred de novo. We identified a novel CALM3 variant, p.Asn138Lys (N138K), in a 4-generation family segregating with LQTS. The aim of this study was to elucidate its pathogenicity and to compare it with that of p.D130G-CaM—a variant associated with a severe LQTS phenotype. Methods: We performed whole exome sequencing for a large, 4-generation family affected by LQTS. To assess the effect of the detected CALM3 variant, the intrinsic Ca 2+ -binding affinity was measured by stoichiometric Ca 2+ titrations and equilibrium titrations. L-type Ca 2+ and slow delayed rectifier potassium currents (I CaL and I Ks ) were recorded by whole-cell patch-clamp. Cav1.2 and Kv7.1 membrane expression were determined by optical fluorescence assays. Results: We identified 14 p.N138K-CaM carriers in a family where 2 sudden deaths occurred in children. Several members were only mildly affected compared with CaM-LQTS patients to date described in literature. The intrinsic Ca 2+ -binding affinity of the CaM C-terminal domain was 10-fold lower for p.N138K-CaM compared with wild-type-CaM. I CaL inactivation was slowed in cells expressing p.N138K-CaM but less than in p.D130G-CaM cells. Unexpectedly, a larger I Ks current density was observed in cells expressing p.N138K-CaM, but not for p.D130G-CaM, compared with wild-type-CaM. Conclusions: The p.N138K CALM3 variant impairs Ca 2+ -binding affinity of CaM and I CaL inactivation but potentiates I Ks . The variably expressed phenotype of this variant compared with previously published de novo LQTS-CaM variants is likely explained by a milder impairment of I CaL inactivation combined with I Ks augmentation.

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Giammarino, L., S. Nimani, S. Bains, N. Alerni, D. J. Tester, N. Christoforou, J. Louradour, et al. "In vivo KCNQ1-suppression-replacement gene therapy in transgenic rabbits with type 1 long QT syndrome." Europace 25, Supplement_1 (May 24, 2023). http://dx.doi.org/10.1093/europace/euad122.594.

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Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Pfizer Background Type 1 long QT syndrome (LQT1) is a genetic channelopathy characterized by both haploinsufficient and dominant-negative loss-of-function pathogenic variants in the KCNQ1-encoded Kv7.1 K+ channels conducting IKs. Patients with LQT1 may manifest QT prolongation and ventricular arrhythmias that can culminate in sudden cardiac death. Purpose With this project, we aim to investigate whether our mutation independent, KCNQ1-specific suppression-replacement (SupRep) gene therapy can restore the deficient K+-channel and thereby restore the healthy phenotype. Methods Our proprietary dual component SupRep gene therapy was created by combining a custom-designed KCNQ1 shRNA and a shRNA-immune (shIMM) KCNQ1 cDNA into AAV9. In vivo AAV9-mediated KCNQ1SupRep gene therapy was performed by targeted intra-aortic root construct injection (1E12 vg/kg body weight) during balloon occlusion using a Swan Ganz catheter. 2 weeks after in vivo gene therapy, 12-lead ECGs were assessed in adult transgenic LQT1 (KCNQ1-Y315S, loss-of IKs) and wild-type (WT) rabbits to determine the effect of SupRep therapy on the rabbit’s QTc. Patch-clamp and calcium transient measurements were performed in isolated ventricular cardiomyocytes to evaluate the effect of SupRep on the cardiomyocyte’s action potential duration (APD90) and Ca2+ transient duration (Ca2+90) both, in vitro – after plasmid transfection, and in vivo – after AAV9-mediated gene therapy. AAV9-KCNQ1-construct expression was verified with immunohistochemistry targeting the GFP-tag. Results After injection of 3 LQT1 rabbits so far, no significant changes were observed in the LQT1 rabbits’ QTc before and after in vivo AAV9-mediated gene therapy. However, at the cellular level, LQT1 cardiomyocytes transfected in vitro with the SupRep-plasmid demonstrated a significant reduction of APD90 (ms, 1Hz stimulation at 37°) compared to LQT1 control cells (SupRep-in-vitro, 358±21 vs. control 447±22, p<0.05). No differences were observed between sham-plasmid transfected cardiomyocytes and LQT1 control cells after one day of culturing. Similarly, cardiomyocytes isolated from the 3 LQT1 rabbits that underwent in vivo SupRep gene therapy demonstrated pronounced shortening of both APD90 and Ca2+90 compared to LQT1 controls, leading to levels similar to WT controls (APD90, 1Hz, 37°: LQT1: 530±18, WT: 445±18, LQT1-SupRep: 375±25, p<0.0001 LQT1 vs. LQT1-SupRep, p=ns LQT1-SupRep vs. WT) (Ca2+90: LQT1: 487±23, WT: 346±16, LQT1-SupRep: 393±19, p<0.0001 LQT1 vs. LQT1-SupRep, p=ns LQT1-SupRep vs. WT). Conclusion In vivo KCNQ1-suppression-replacement gene therapy normalizes cellular action potential and calcium transient duration in transgenic LQT1 rabbits. Further in vivo experiments will be conducted to evaluate whether this therapeutic correction at the cardiomyocyte level will translate into normalization of the LQT1 rabbits’ QTc both at rest and during stress testing.

Journal articles on the topic 'Kv7.2/3'

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