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Trum M, Islam MMT, Lebek S, Baier M, Hegner P, Eaton P, Maier LS, Wagner S. Inhibition of cardiac potassium currents by oxidation-activated protein kinase A contributes to early afterdepolarizations in the heart. Am J Physiol Heart Circ Physiol 2020; 319:H1347-H1357. [PMID: 33035439 PMCID: PMC7792712 DOI: 10.1152/ajpheart.00182.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Reactive oxygen species (ROS) have been shown to prolong cardiac action potential duration resulting in afterdepolarizations, the cellular basis of triggered arrhythmias. As previously shown, protein kinase A type I (PKA I) is readily activated by oxidation of its regulatory subunits. However, the relevance of this mechanism of activation for cardiac pathophysiology is still elusive. In this study, we investigated the effects of oxidation-activated PKA I on cardiac electrophysiology. Ventricular cardiomyocytes were isolated from redox-dead PKA-RI Cys17Ser knock-in (KI) and wild-type (WT) mice and exposed to H2O2 (200 µmol/L) or vehicle (Veh) solution. In WT myocytes, exposure to H2O2 significantly increased oxidation of the regulatory subunit I (RI) and thus its dimerization (threefold increase in PKA RI dimer). Whole cell current clamp and voltage clamp were used to measure cardiac action potentials (APs), transient outward potassium current (Ito) and inward rectifying potassium current (IK1), respectively. In WT myocytes, H2O2 exposure significantly prolonged AP duration due to significantly decreased Ito and IK1 resulting in frequent early afterdepolarizations (EADs). Preincubation with the PKA-specific inhibitor Rp-8-Br-cAMPS (10 µmol/L) completely abolished the H2O2-dependent decrease in Ito and IK1 in WT myocytes. Intriguingly, H2O2 exposure did not prolong AP duration, nor did it decrease Ito, and only slightly enhanced EAD frequency in KI myocytes. Treatment of WT and KI cardiomyocytes with the late INa inhibitor TTX (1 µmol/L) completely abolished EAD formation. Our results suggest that redox-activated PKA may be important for H2O2-dependent arrhythmias and could be important for the development of specific antiarrhythmic drugs.NEW & NOTEWORTHY Oxidation-activated PKA type I inhibits transient outward potassium current (Ito) and inward rectifying potassium current (IK1) and contributes to ROS-induced APD prolongation as well as generation of early afterdepolarizations in murine ventricular cardiomyocytes.
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Affiliation(s)
- M. Trum
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - M. M. T. Islam
- 2Department of Biochemistry and Molecular Biology, University of Dhaka, Bangladesh
- 3Department of Cardiology and Pneumology, University Medical Center Göttingen, Göttingen, Germany
| | - S. Lebek
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - M. Baier
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - P. Hegner
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - P. Eaton
- 4The William Harvey Research Institute, Charterhouse Square, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - L. S. Maier
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - S. Wagner
- 1Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
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Sakamoto K, Suzuki Y, Yamamura H, Ohya S, Muraki K, Imaizumi Y. Molecular mechanisms underlying pimaric acid-induced modulation of voltage-gated K + channels. J Pharmacol Sci 2017; 133:223-231. [PMID: 28391996 DOI: 10.1016/j.jphs.2017.02.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 02/11/2017] [Accepted: 02/21/2017] [Indexed: 01/14/2023] Open
Abstract
Voltage-gated K+ (KV) channels, which control firing and shape of action potentials in excitable cells, are supposed to be potential therapeutic targets in many types of diseases. Pimaric acid (PiMA) is a unique opener of large conductance Ca2+-activated K+ channel. Here, we report that PiMA modulates recombinant rodent KV channel activity. The enhancement was significant at low potentials (<0 mV) but not at more positive potentials. Application of PiMA significantly shifted the voltage-activation relationships (V1/2) of rodent KV1.1, 1.2, 1.3, 1.4, 1.6 and 2.1 channels (KV1.1-KV2.1) but KV4.3 to lower potentials and prolonged their half-decay times of the deactivation (T1/2D). The amino acid sequence which is responsible for the difference in response to PiMA was examined between KV1.1-KV2.1 and KV4.3 by site-directed mutagenesis of residues in S5 and S6 segments of Kv1.1. The point mutation of Phe332 into Tyr mimics the effects of PiMA on V1/2 and T1/2D and also abolished the further change by addition of PiMA. The results indicate that PiMA enhances voltage sensitivity of KV1.1-KV2.1 channels and suggest that the lipophilic residues including Phe332 in S5 of KV1.1-KV2.1 channels may be critical for the effects of PiMA, providing beneficial information for drug development of KV channel openers.
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Affiliation(s)
- Kazuho Sakamoto
- Department of Pharmacology, School of Medicine, Fukushima Medical University, Fukushima 960-1295, Japan; Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yoshiaki Suzuki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Hisao Yamamura
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Susumu Ohya
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan; Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
| | - Katsuhiko Muraki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan; Laboratory Cellular Pharmacology, School of Pharmacy, Aichi Gakuin University, Nagoya 464-8650, Japan
| | - Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
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Ribeiro LAA, Alencar Filho EB, Coelho MC, Silva BA. The vasorelaxant effect of 8(17),12E,14-labdatrien-18-oic acid involves stimulation of adenylyl cyclase and cAMP/PKA pathway: Evidences by pharmacological and molecular docking studies. Eur J Pharmacol 2015; 764:363-371. [PMID: 26144373 DOI: 10.1016/j.ejphar.2015.06.063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 06/19/2015] [Accepted: 06/30/2015] [Indexed: 11/24/2022]
Abstract
The relaxant effect of 8(17),12E,14-labdatrien-18-oic acid (LBD) was investigated on isolated aortic rings and compared with forskolin (FSK), a standard and potent activator of adenylyl cyclase (AC) with relaxing effect. The presence of potassium channel blockers, such as glibenclamide (ATP-blocker), apamin (SKCa-blocker), charybdotoxin (BKCa-blocker) did not significantly affect either the LBD or FSK concentration-response curves. However, in the presence of 4-aminopyridine (KV-blocker), the relaxant effect for both diterpenes was significantly attenuated, with reduction of its relative potencies. Moreover, the relaxation induced by 8-Br-cAMP, an analog of cAMP, was also significantly attenuated in the same conditions, i.e., in the presence of 4-aminopyridine. The presence of aminophylline, a nonselective phosphodiesterase inhibitor, caused a significant increasing in the potency for both LBD and FSK. On the other hand, the presence of Rp-cAMPS, a selective PKA-inhibitor, significantly attenuated the relaxant effect of LBD. In this work, in the same experimental conditions, both labdane-type diterpenes presented remarkably similar results; FSK, however, presented a higher potency (100-fold) than LBD. Thus, the hypothesis that LBD could be a novel AC-activator emerged. To assess that hypothesis, computational molecular docking studies were performed. Crystallographic structure of adenylyl cyclase/forskolin complex (1AB8) was obtained from RSCB Protein Data Bank and used to compare the modes of interaction of the native ligand and LBD. The computational data shows many similarities between LBD and FSK concerning the interaction with the regulatory site of AC. Taken together, the results presented here pointed to LBD as a novel AC-activator.
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Affiliation(s)
- Luciano A A Ribeiro
- Colegiado de Farmácia (CFARM), Universidade Federal do Vale do São Francisco (UNIVASF), Av. José de Sá Maniçoba, S/No, Campus Centro, P.O. Box 252, CEP:56304-205, Petrolina, PE, Brazil; Programa de Pós-Graduação em Recursos Naturais do Semiárido (PGRNSA), Universidade Federal do Vale do São Francisco (UNIVASF), 56304-205, Petrolina, PE, Brazil.
| | - Edilson B Alencar Filho
- Colegiado de Farmácia (CFARM), Universidade Federal do Vale do São Francisco (UNIVASF), Av. José de Sá Maniçoba, S/No, Campus Centro, P.O. Box 252, CEP:56304-205, Petrolina, PE, Brazil
| | - Maisa C Coelho
- Curso de Graduação em Farmácia, Universidade Federal do Vale do São Francisco (UNIVASF), 56304-205, Petrolina, PE, Brazil
| | - Bagnólia A Silva
- Universidade Federal da Paraíba, Laboratório de Tecnologia Farmacêutica-Campus I. Cidade Universitária, 58051-970, Joao Pessoa, PB, Brazil
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Angel-Chavez LI, Acosta-Gómez EI, Morales-Avalos M, Castro E, Cruzblanca H. Forskolin suppresses delayed-rectifier K+ currents and enhances spike frequency-dependent adaptation of sympathetic neurons. PLoS One 2015; 10:e0126365. [PMID: 25962132 PMCID: PMC4427186 DOI: 10.1371/journal.pone.0126365] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/01/2015] [Indexed: 11/30/2022] Open
Abstract
In signal transduction research natural or synthetic molecules are commonly used to target a great variety of signaling proteins. For instance, forskolin, a diterpene activator of adenylate cyclase, has been widely used in cellular preparations to increase the intracellular cAMP level. However, it has been shown that forskolin directly inhibits some cloned K+ channels, which in excitable cells set up the resting membrane potential, the shape of action potential and regulate repetitive firing. Despite the growing evidence indicating that K+ channels are blocked by forskolin, there are no studies yet assessing the impact of this mechanism of action on neuron excitability and firing patterns. In sympathetic neurons, we find that forskolin and its derivative 1,9-Dideoxyforskolin, reversibly suppress the delayed rectifier K+ current (IKV). Besides, forskolin reduced the spike afterhyperpolarization and enhanced the spike frequency-dependent adaptation. Given that IKV is mostly generated by Kv2.1 channels, HEK-293 cells were transfected with cDNA encoding for the Kv2.1 α subunit, to characterize the mechanism of forskolin action. Both drugs reversible suppressed the Kv2.1-mediated K+ currents. Forskolin inhibited Kv2.1 currents and IKV with an IC50 of ~32 μM and ~24 µM, respectively. Besides, the drug induced an apparent current inactivation and slowed-down current deactivation. We suggest that forskolin reduces the excitability of sympathetic neurons by enhancing the spike frequency-dependent adaptation, partially through a direct block of their native Kv2.1 channels.
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Affiliation(s)
- Luis I. Angel-Chavez
- Departamento de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Ciudad Juárez, Chih. 32310, México
| | - Eduardo I. Acosta-Gómez
- Departamento de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Ciudad Juárez, Chih. 32310, México
| | - Mario Morales-Avalos
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
| | - Elena Castro
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
| | - Humberto Cruzblanca
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
- * E-mail:
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Hanna ST, Pigeau GM, Galvanovskis J, Clark A, Rorsman P, MacDonald PE. Kiss-and-run exocytosis and fusion pores of secretory vesicles in human beta-cells. Pflugers Arch 2008; 457:1343-50. [PMID: 18795319 DOI: 10.1007/s00424-008-0588-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 08/27/2008] [Accepted: 09/01/2008] [Indexed: 01/18/2023]
Abstract
Exocytosis of secretory vesicles results in the release of insulin from pancreatic beta-cells, although little is known about this process in humans. We examined the exocytosis of single secretory vesicles and their associated fusion pores in human beta-cells by cell-attached capacitance and conductance measurement. Unitary capacitance steps were observed, consistent with the exocytosis of single secretory vesicles. These were often coincident with increases in patch conductance representing the presence of a stable fusion pore. In some events, the fusion pore closed, mediating kiss-and-run, which contributed 20% of the exocytotic events. The cAMP-raising agent forskolin (5 microM) doubled the relative contribution of kiss-and-run. This effect was confirmed visually in MIN6 cells expressing a fluorescent granule probe. Thus, we demonstrate the unitary capacitance steps and fusion pores during single vesicle exocytosis in human beta-cells. Furthermore, these secretory vesicles can undergo rapid recycling by kiss-and-run, and this process is up-regulated by cAMP.
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Affiliation(s)
- Salma T Hanna
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, HRIF East, Rm 6-126, Edmonton, AB T6G 2E1, Canada
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Kourrich S, Manrique C, Salin P, Mourre C. Transient hippocampal down-regulation of Kv1.1 subunit mRNA during associative learning in rats. Learn Mem 2006; 12:511-9. [PMID: 16204203 PMCID: PMC1240063 DOI: 10.1101/lm.86305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Voltage-gated potassium channels (Kv) are critically involved in learning and memory processes. It is not known, however, whether the expression of the Kv1.1 subunit, constituting Kv1 channels, can be specifically regulated in brain areas important for learning and memory processing. Radioactive in situ hybridization was used to evaluate the content of Kv1.1 alpha-subunit mRNA in the olfactory bulb, ventral, and dorsal hippocampus at different stages of an odor-discrimination associative task in rats. Naive, conditioned, and pseudoconditioned animals were sacrificed at different times either prior to a two-odor significance learning or after odor discrimination was established. Important decreases of Kv1.1 mRNA levels were transiently observed in the ventral hippocampus before successful learning when compared with the pseudoconditioned group. Moreover, temporal group analysis showed significant labeling alterations in the hippocampus of conditioned and pseudoconditioned groups throughout the training. Finally, Kv1.1 mRNA levels in the hippocampus were positively correlated with odor-reward association learning in rats that were beginning to discriminate between odors. These findings indicate that the Kv1.1 subunit is transiently down-regulated in the early stages of learning and suggest that Kv1 channel expression regulation is critical for the modification of neuronal substrates underlying new information acquisition.
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Affiliation(s)
- Saïd Kourrich
- Laboratoire de Neurobiologie des Processus Mnésiques, UMR 6149 CNRS-Université de Provence, Marseille, France
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Preitner F, Ibberson M, Franklin I, Binnert C, Pende M, Gjinovci A, Hansotia T, Drucker DJ, Wollheim C, Burcelin R, Thorens B. Gluco-incretins control insulin secretion at multiple levels as revealed in mice lacking GLP-1 and GIP receptors. J Clin Invest 2004; 113:635-45. [PMID: 14966573 PMCID: PMC338268 DOI: 10.1172/jci20518] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 12/16/2003] [Indexed: 12/20/2022] Open
Abstract
The role of the gluco-incretin hormones GIP and GLP-1 in the control of beta cell function was studied by analyzing mice with inactivation of each of these hormone receptor genes, or both. Our results demonstrate that glucose intolerance was additively increased during oral glucose absorption when both receptors were inactivated. After intraperitoneal injections, glucose intolerance was more severe in double- as compared to single-receptor KO mice, and euglycemic clamps revealed normal insulin sensitivity, suggesting a defect in insulin secretion. When assessed in vivo or in perfused pancreas, insulin secretion showed a lack of first phase in Glp-1R(-/-) but not in Gipr(-/-) mice. In perifusion experiments, however, first-phase insulin secretion was present in both types of islets. In double-KO islets, kinetics of insulin secretion was normal, but its amplitude was reduced by about 50% because of a defect distal to plasma membrane depolarization. Thus, gluco-incretin hormones control insulin secretion (a) by an acute insulinotropic effect on beta cells after oral glucose absorption (b) through the regulation, by GLP-1, of in vivo first-phase insulin secretion, probably by an action on extra-islet glucose sensors, and (c) by preserving the function of the secretory pathway, as evidenced by a beta cell autonomous secretion defect when both receptors are inactivated.
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Preitner F, Ibberson M, Franklin I, Binnert C, Pende M, Gjinovci A, Hansotia T, Drucker DJ, Wollheim C, Burcelin R, Thorens B. Gluco-incretins control insulin secretion at multiple levels as revealed in mice lacking GLP-1 and GIP receptors. J Clin Invest 2004. [DOI: 10.1172/jci200420518] [Citation(s) in RCA: 191] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Hu HJ, Gereau RW. ERK integrates PKA and PKC signaling in superficial dorsal horn neurons. II. Modulation of neuronal excitability. J Neurophysiol 2003; 90:1680-8. [PMID: 12750418 DOI: 10.1152/jn.00341.2003] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Protein kinases belonging to the protein kinase A (PKA), protein kinase C (PKC), and extracellular signal-related kinase (ERK) families have been identified as key players in modulating nociception at the level of the spinal cord dorsal horn, yet little is known about the effects of these kinases on membrane properties of the dorsal horn neurons. PKA, PKC, and ERK exert inhibitory effects on transient potassium currents (A-type currents or IA) in mouse superficial dorsal horn neurons (Hu et al. 2003). Here we aimed to determine the effects of these kinases on action potential firing and membrane properties of these neurons to evaluate the impact of the modulation of IA (and other conductances) in these neurons. We found that activating PKC and PKA has dramatic effects on action potential firing, reflecting an increase in the excitability of superficial dorsal horn neurons. In addition, we found that inhibitors of both PKC and ERK signaling decrease the excitability of dorsal horn neurons, suggesting that these kinases exert a tonic excitation of these cells. Consistent with our findings that these kinases inhibit A-type currents, we found that PKA, PKC, and ERK act to shorten the first-spike latency after depolarization induced by current injection. In addition, activation of these kinases increases spike frequency and action potential amplitude of dorsal horn neurons. Interestingly, we found that the effects of PKA and PKC activators are blocked by inhibitors of ERK signaling, suggesting that PKA and PKC may exert their actions by activation of ERKs.
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Affiliation(s)
- Hui-Juan Hu
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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Rothman JS, Manis PB. The roles potassium currents play in regulating the electrical activity of ventral cochlear nucleus neurons. J Neurophysiol 2003; 89:3097-113. [PMID: 12783953 DOI: 10.1152/jn.00127.2002] [Citation(s) in RCA: 208] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current (IA), a slow-inactivating low-threshold current (ILT), and a noninactivating high-threshold current (IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current (Ih), and 1-50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that IHT mainly functions to repolarize the membrane during an action potential, and IA functions to modulate the rate of repetitive firing. ILT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of ILT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of ILT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of Ih, which changes the resting membrane potential, is a more effective means of modulating the activation level of ILT than simply modulating ILT itself. This result may explain why ILT and Ih are often coexpressed throughout the nervous system.
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Affiliation(s)
- Jason S Rothman
- The Center for Hearing Science, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Winklhofer M, Matthias K, Seifert G, Stocker M, Sewing S, Herget T, Steinhäuser C, Saaler-Reinhardt S. Analysis of phosphorylation-dependent modulation of Kv1.1 potassium channels. Neuropharmacology 2003; 44:829-42. [PMID: 12681381 DOI: 10.1016/s0028-3908(03)00070-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The voltage-gated potassium channel Kv1.1 contains phosphorylation sites for protein kinase A (PKA) and protein kinase C (PKC). To study Kv1.1 protein expression and cellular distribution in regard to its level of phosphorylation, the effects of PKA and PKC activation on Kv1.1 were investigated in HEK 293 cells stably transfected with Kv1.1 (HEK 293/1). Without kinase activation, HEK 293/1 cells carry unphosphorylated Kv1.1 protein in the plasma membranes, whereas large amounts of phosphorylated and unphosphorylated Kv1.1 protein were located intracellularly. Activation of PKA resulted in phosphorylation of intracellular Kv1.1 protein, followed by a rapid translocation of Kv1.1 into the plasma membrane. Patch-clamp analysis revealed an increase in current amplitude upon PKA activation and demonstrated differences in the voltage dependence of current activation between unphosphorylated and phosphorylated Kv1.1 channels. In contrast to PKA, even prolonged activation of PKC did not lead to direct phosphorylation of Kv1.1, but induced Kv1.1 protein synthesis. Thus, protein kinases have direct and indirect effects on the functional expression of voltage-gated potassium channels. Our data suggest that the synergistic action of protein kinases may play an important role in the fine-tuning of Kv channel function.
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Affiliation(s)
- M Winklhofer
- Institute of Physiological Chemistry, Johannes Gutenberg-University, Mainz, Germany
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