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Abstract
Lysosomes are acidic membrane-bound organelles that use hydrolytic enzymes to break down material through pathways such as endocytosis, phagocytosis, mitophagy, and autophagy. To function properly, intralysosomal environments are strictly controlled by a set of integral membrane proteins such as ion channels and transporters. Potassium ion (K+) channels are a large and diverse family of membrane proteins that control K+ flux across both the plasma membrane and intracellular membranes. In the plasma membrane, they are essential in both excitable and non-excitable cells for the control of membrane potential and cell signaling. However, our understanding of intracellular K+ channels is very limited. In this review, we summarize the recent development in studies of K+ channels in the lysosome. We focus on their characterization, potential roles in maintaining lysosomal membrane potential and lysosomal function, and pathological implications.
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Affiliation(s)
- Peng Huang
- Collaborative Innovation Center for Biomedicine, School of Clinical Medicine, Shanghai University of Medicine and Health Sciences, Shanghai, China
| | - Mengnan Xu
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, Halifax, NS, Canada
| | - Yi Wu
- Collaborative Innovation Center for Biomedicine, School of Clinical Medicine, Shanghai University of Medicine and Health Sciences, Shanghai, China
| | - Alia Kazim Rizvi Syeda
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, Halifax, NS, Canada
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, Halifax, NS, Canada.
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Di A, Xiong S, Ye Z, Malireddi RKS, Kometani S, Zhong M, Mittal M, Hong Z, Kanneganti TD, Rehman J, Malik AB. The TWIK2 Potassium Efflux Channel in Macrophages Mediates NLRP3 Inflammasome-Induced Inflammation. Immunity 2018; 49:56-65.e4. [PMID: 29958799 DOI: 10.1016/j.immuni.2018.04.032] [Citation(s) in RCA: 249] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 03/06/2018] [Accepted: 04/27/2018] [Indexed: 12/12/2022]
Abstract
Potassium (K+) efflux across the plasma membrane is thought to be an essential mechanism for ATP-induced NLRP3 inflammasome activation, yet the identity of the efflux channel has remained elusive. Here we identified the two-pore domain K+ channel (K2P) TWIK2 as the K+ efflux channel triggering NLRP3 inflammasome activation. Deletion of Kcnk6 (encoding TWIK2) prevented NLRP3 activation in macrophages and suppressed sepsis-induced lung inflammation. Adoptive transfer of Kcnk6-/- macrophages into mouse airways after macrophage depletion also prevented inflammatory lung injury. The K+ efflux channel TWIK2 in macrophages has a fundamental role in activating the NLRP3 inflammasome and consequently mediates inflammation, pointing to TWIK2 as a potential target for anti-inflammatory therapies.
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Affiliation(s)
- Anke Di
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Shiqin Xiong
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Zhiming Ye
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | | | - Satoshi Kometani
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Ming Zhong
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Manish Mittal
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Zhigang Hong
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | | | - Jalees Rehman
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Asrar B Malik
- Department of Pharmacology and the Center for Lung and Vascular Biology, The University of Illinois College of Medicine, Chicago, IL 60612, USA.
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Recombinant tandem of pore-domains in a Weakly Inward rectifying K + channel 2 (TWIK2) forms active lysosomal channels. Sci Rep 2017; 7:649. [PMID: 28381826 PMCID: PMC5428834 DOI: 10.1038/s41598-017-00640-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 03/07/2017] [Indexed: 12/27/2022] Open
Abstract
Recombinant TWIK2 channels produce weak basal background K+ currents. Current amplitudes depend on the animal species the channels have been isolated from and on the heterologous system used for their re-expression. Here we show that this variability is due to a unique cellular trafficking. We identified three different sequence signals responsible for the preferential expression of TWIK2 in the Lamp1-positive lysosomal compartment. Sequential inactivation of tyrosine-based (Y308ASIP) and di-leucine-like (E266LILL and D282EDDQVDIL) trafficking motifs progressively abolishes the targeting of TWIK2 to lysosomes, and promotes its functional relocation at the plasma membrane. In addition, TWIK2 contains two N-glycosylation sites (N79AS and N85AS) on its luminal side, and glycosylation is necessary for expression in lysosomes. As shown by electrophysiology and electron microscopy, TWIK2 produces functional background K+ currents in the endolysosomes, and its expression affects the number and mean size of the lysosomes. These results show that TWIK2 is expressed in lysosomes, further expanding the registry of ion channels expressed in these organelles.
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Chen H, Zuo D, Zhang J, Zhou M, Ma L. Classification of 2-pore domain potassium channels based on rectification under quasi-physiological ionic conditions. Channels (Austin) 2015; 8:503-8. [PMID: 25616686 DOI: 10.4161/19336950.2014.973779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
It is generally expected that 2-pore domain K(+) (K2P) channels are open or outward rectifiers in asymmetric physiological K(+) gradients, following the Goldman-Hodgkin-Katz (GHK) current equation. Although cloned K2P channels have been extensively studied, their current-voltage (I-V) relationships are not precisely characterized and previous definitions are contradictory. Here we study all the functional channels from 6 mammalian K2P subfamilies in transfected Chinese hamster ovary cells with patch-clamp technique, and examine whether their I-V relationships are described by the GHK current equation. K2P channels display 2 distinct types of I-V curves in asymmetric physiological K(+) gradients. Two K2P isoforms in the TWIK subfamily conduct large inward K(+) currents and have a nearly linear I-V curve. Ten isoforms from 5 other K2P subfamilies conduct small inward K(+) currents and exhibit open rectification, but fits with the GHK current equation cannot precisely reveal the differences in rectification among K2P channels. The Rectification Index, a ratio of limiting I-V slopes for outward and inward currents, is used to quantitatively describe open rectification of each K2P isoform, which is previously qualitatively defined as strong or weak open rectification. These results systematically and precisely classify K2P channels and suggest that TWIK K(+) channels have a unique feature in regulating cellular function.
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Affiliation(s)
- Haijun Chen
- a Department of Biological Sciences ; University at Albany; State University of New York ; Albany , NY USA
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Bouhadfane M, Kaszás A, Rózsa B, Harris-Warrick RM, Vinay L, Brocard F. Sensitization of neonatal rat lumbar motoneuron by the inflammatory pain mediator bradykinin. eLife 2015; 4:e06195. [PMID: 25781633 PMCID: PMC4410746 DOI: 10.7554/elife.06195] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 03/16/2015] [Indexed: 11/27/2022] Open
Abstract
Bradykinin (Bk) is a potent inflammatory mediator that causes hyperalgesia. The action of Bk on the sensory system is well documented but its effects on motoneurons, the final pathway of the motor system, are unknown. By a combination of patch-clamp recordings and two-photon calcium imaging, we found that Bk strongly sensitizes spinal motoneurons. Sensitization was characterized by an increased ability to generate self-sustained spiking in response to excitatory inputs. Our pharmacological study described a dual ionic mechanism to sensitize motoneurons, including inhibition of a barium-sensitive resting K+ conductance and activation of a nonselective cationic conductance primarily mediated by Na+. Examination of the upstream signaling pathways provided evidence for postsynaptic activation of B2 receptors, G protein activation of phospholipase C, InsP3 synthesis, and calmodulin activation. This study questions the influence of motoneurons in the assessment of hyperalgesia since the withdrawal motor reflex is commonly used as a surrogate pain model. DOI:http://dx.doi.org/10.7554/eLife.06195.001 When we accidentally place our hand on a hot stove, we normally experience a painful sensation that starts with the sensory nerves under our skin. These nerves respond by transmitting electrical impulses to our brain, where the painful sensation is then processed. At the same time, these impulses are also transmitted to the motor nerves that control the muscles in our hand to trigger an immediate reflex to withdraw the hand from the hot stove. Pain therefore has a useful role as it can reduce how bad an injury is. People with a condition called hyperalgesia have an increased sensitivity to pain. This condition can result from a chemical called bradykinin ‘sensitizing’ the sensory nerves, causing them to transmit more electrical impulses in response to pain than normal. This makes the injury feel much more painful, and can make the pain last for longer than is beneficial. It was less clear whether bradykinin also affects motor nerves and so triggers a withdrawal reflex. By recording the electrical activity of motor nerve cells taken from the spinal cords of newborn rats, Bouhadfane et al. now show that these motor nerves become more active when exposed to bradykinin. Nerve cells generate electrical signals when ions—such as potassium, sodium, and calcium ions—move through channels in the membranes of the cell. Therefore, to investigate how bradykinin influences the electrical activity of motor nerves, Bouhadfane et al. exposed the cells to drugs that inhibit particular ion channels. This revealed that bradykinin sensitizes the motor nerves by blocking a type of potassium ion channel and activating another ion channel that mainly transports sodium ions. Furthermore, Bouhadfane et al. were able to identify the signaling pathways that allow bradykinin to affect the motor nerve cells. The study implies that the neuronal circuitry for pain does not rely exclusively on sensory nerve cells but should also integrate motor nerve cells. A future challenge remains in developing a protocol to resolve the contribution of motor nerve cells to hyperalgesia assessed by reflex withdrawal. DOI:http://dx.doi.org/10.7554/eLife.06195.002
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Affiliation(s)
- Mouloud Bouhadfane
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
| | - Attila Kaszás
- Institut de Neuroscience des Systèmes (UMR1106), Aix Marseille Université and INSERM, Marseille, France
| | - Balázs Rózsa
- Two-Photon Imaging Center, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | | | - Laurent Vinay
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
| | - Frédéric Brocard
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
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Hayoz S, Cubano L, Maldonado H, Bychkov R. Protein kinase A and C regulate leak potassium currents in freshly isolated vascular myocytes from the aorta. PLoS One 2013; 8:e75077. [PMID: 24086441 PMCID: PMC3781042 DOI: 10.1371/journal.pone.0075077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 08/09/2013] [Indexed: 11/18/2022] Open
Abstract
We tested the hypothesis that protein kinase A (PKA) inhibits K2P currents activated by protein kinase C (PKC) in freshly isolated aortic myocytes. PDBu, the PKC agonist, applied extracellularly, increased the amplitude of the K2P currents in the presence of the “cocktail” of K+ channel blockers. Gö 6976 significantly reduced the increase of the K2P currents by PDBu suggesting the involvement of either α or β isoenzymes of PKC. We found that forskolin, or membrane permeable cAMP, did not inhibit K2P currents activated by the PKC. However, when PKA agonists were added prior to PDBu, they produced a strong decrease in the K2P current amplitudes activated by PKC. Inhibition of PDBu-elicited K2P currents by cAMP agonists was not prevented by the treatment of vascular smooth muscle cells with PKA antagonists (H-89 and Rp-cAMPs). Zn2+ and Hg2+ inhibited K2P currents in one population of cells, produced biphasic responses in another population, and increased the amplitude of the PDBu-elicited K+ currents in a third population of myocytes, suggesting expression of several K2P channel types. We found that cAMP agonists inhibited biphasic responses and increase of amplitude of the PDBu-elicited K2P currents produced by Zn2+ and Hg2. 6-Bnz-cAMp produced a significantly altered pH sensitivity of PDBu-elicited K2P-currents, suggesting the inhibition of alkaline-activated K2P-currents. These results indicate that 6-Bnz-cAMP and other cAMP analogs may inhibit K2P currents through a PKA-independent mechanism. cAMP analogs may interact with unidentified proteins involved in K2P channel regulation. This novel cellular mechanism could provide insights into the interplay between PKC and PKA pathways that regulate vascular tone.
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Affiliation(s)
- Sébastien Hayoz
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, United States of America
- Department of Pharmacology, Universidad Central Del Caribe, Bayamon, Puerto Rico, United States of America
| | - Luis Cubano
- Department of Pharmacology, Universidad Central Del Caribe, Bayamon, Puerto Rico, United States of America
| | - Hector Maldonado
- Department of Pharmacology, Universidad Central Del Caribe, Bayamon, Puerto Rico, United States of America
| | - Rostislav Bychkov
- Department of Pharmacology, Universidad Central Del Caribe, Bayamon, Puerto Rico, United States of America
- * E-mail:
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Nielsen G, Wandall-Frostholm C, Sadda V, Oliván-Viguera A, Lloyd EE, Bryan RM, Simonsen U, Köhler R. Alterations of N-3 polyunsaturated fatty acid-activated K2P channels in hypoxia-induced pulmonary hypertension. Basic Clin Pharmacol Toxicol 2013; 113:250-8. [PMID: 23724868 DOI: 10.1111/bcpt.12092] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 05/24/2013] [Indexed: 01/06/2023]
Abstract
Polyunsaturated fatty acid (PUFA)-activated two-pore domain potassium channels (K2P ) have been proposed to be expressed in the pulmonary vasculature. However, their physiological or pathophysiological roles are poorly defined. Here, we tested the hypothesis that PUFA-activated K2P are involved in pulmonary vasorelaxation and that alterations of channel expression are pathophysiologically linked to pulmonary hypertension. Expression of PUFA-activated K2P in the murine lung was investigated by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), by patch clamp (PC) and myography. K2P -gene expression was examined in chronic hypoxic mice. qRT-PCR showed that the K2P 2.1 and K2P 6.1 were the predominantly expressed K2P in the murine lung. IHC revealed protein expression of K2P 2.1 and K2P 6.1 in the endothelium of pulmonary arteries and of K2P 6.1 in bronchial epithelium. PC showed pimozide-sensitive K2P -like K(+) -current activated by docosahexaenoic acid (DHA) in freshly isolated endothelial cells as well as DHA-induced membrane hyperpolarization. Myography on pulmonary arteries showed that DHA induced concentration-dependent instantaneous relaxations that were resistant to endothelial removal and inhibition of NO and prostacyclin synthesis and to a cocktail of blockers of calcium-activated K(+) channels but were abolished by high extracellular (30 mM) K(+) -concentration. Gene expression and protein of K2P 2.1 were not altered in chronic hypoxic mice, while K2P 6.1 was up-regulated by fourfold. In conclusion, the PUFA-activated K2P 2.1 and K2P 6.1 are expressed in murine lung and functional K2P -like channels contribute to endothelium hyperpolarization and pulmonary artery relaxation. The increased K2P 6.1-gene expression may represent a novel counter-regulatory mechanism in pulmonary hypertension and suggest that arterial K2P 2.1 and K2P 6.1 could be novel therapeutic targets.
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Affiliation(s)
- Gorm Nielsen
- Cardiovascular and Renal Research, Institute for Molecular Medicine, University of Southern Denmark, Odense, Denmark
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Vetri F, Xu H, Paisansathan C, Pelligrino DA. Impairment of neurovascular coupling in type 1 diabetes mellitus in rats is linked to PKC modulation of BK(Ca) and Kir channels. Am J Physiol Heart Circ Physiol 2012; 302:H1274-84. [PMID: 22268114 DOI: 10.1152/ajpheart.01067.2011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We hypothesized that chronic hyperglycemia has a detrimental effect on neurovascular coupling in the brain and that this may be linked to protein kinase C (PKC)-mediated phosphorylation. Therefore, in a rat model of streptozotocin-induced chronic type 1 diabetes mellitus (T1DM), and in nondiabetic (ND) controls, we monitored pial arteriole diameter changes during sciatic nerve stimulation and topical applications of the large-conductance Ca(2+)-operated K(+) channel (BK(Ca)) opener, NS-1619, or the K(+) inward rectifier (Kir) channel agonist, K(+). In the T1DM vs. ND rats, the dilatory response associated with sciatic nerve stimulation was decreased by ∼30%, whereas pial arteriolar dilations to NS-1619 and K(+) were largely suppressed. These responses were completely restored by the acute topical application of a PKC antagonist, calphostin C. Moreover, the suffusion of a PKC activator, phorbol 12,13-dibutyrate, in ND rats was able to reproduce the vascular reactivity impairments found in T1DM rats. Assay of PKC activity in brain samples from T1DM vs. ND rats revealed a significant gain in activity only in specimens harvested from the pial and superficial glia limitans tissue, but not in bulk cortical gray matter. Altogether, these findings suggest that the T1DM-associated impairment of neurovascular coupling may be mechanistically linked to a readily reversible PKC-mediated depression of BK(Ca) and Kir channel activity.
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Affiliation(s)
- Francesco Vetri
- Neuroanesthesia Research Laboratory, Department of Anesthesiology, University of Illinois at Chicago, 60612, USA.
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Clark RB, Kondo C, Belke DD, Giles WR. Two-pore domain K⁺ channels regulate membrane potential of isolated human articular chondrocytes. J Physiol 2011; 589:5071-89. [PMID: 21911614 DOI: 10.1113/jphysiol.2011.210757] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Potassium channels that regulate resting membrane potential (RMP) of human articular chondrocytes (HACs) of the tibial joint maintained in short-term (0-3 days) non-confluent cell culture were studied using patch-clamp techniques. Quantitative PCR showed that transcripts of genes for two-pore domain K(+) channels (KCNK1, KCNK5 and KCNK6), and 'BK' Ca(2+)-activated K(+) channels (KCNMA1) were abundantly expressed. Immunocytological methods detected α-subunits for BK and K(2p)5.1 (TASK-2) K(+) channels. Electrophysiological recordings identified three distinct K(+) currents in isolated HACs: (i) a voltage- and time-dependent 'delayed rectifier', blocked by 100 nM α-dendrotoxin, (ii) a large 'noisy' voltage-dependent current that was blocked by low concentrations of tetraethylammonium (TEA; 50% blocking dose = 0.15 mM) and iberiotoxin (52% block, 100 nM) and (iii) a voltage-independent 'background' K(+) current that was blocked by acidic pH (5.5-6), was increased by alkaline pH (8.5), and was not blocked by TEA, but was blocked by the local anaesthetic bupivacaine (0.25 mM). The RMP of isolated HACs was very slightly affected by 5 mM TEA, which was sufficient to block both voltage-dependent K(+) currents, suggesting that these currents probably contributed little to maintaining RMP under 'resting' conditions (i.e. low internal [Ca(2+)]). Increases in external K(+) concentration depolarized HACs by 30 mV in response to a 10-fold increase in [K(+)], indicating a significant but not exclusive role for K(+) current in determining RMP. Increases in external [K(+)] in voltage-clamped HACs revealed a voltage-independent K(+) current whose inward current magnitude increased with external [K(+)]. Block of this current by bupivacaine (0.25-1 mM) in 5 and 25 mM external [K(+)] resulted in a large (8-25 mV) depolarization of RMP. The biophysical and pharmacological properties of the background K(+) current, together with expression of mRNA and α-subunit protein for TASK-2, strongly suggest that these two-pore domain K(+) channels contribute significantly to stabilizing the RMP of HACs.
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Affiliation(s)
- Robert B Clark
- Roger Jackson Centre for Health and Wellness Research, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Lloyd EE, Crossland RF, Phillips SC, Marrelli SP, Reddy AK, Taffet GE, Hartley CJ, Bryan RM. Disruption of K(2P)6.1 produces vascular dysfunction and hypertension in mice. Hypertension 2011; 58:672-8. [PMID: 21876070 DOI: 10.1161/hypertensionaha.111.175349] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
K(2P)6.1, a member of the 2-pore domain K channel family, is highly expressed in the vascular system; however, its function is unknown. We tested the following hypotheses. K(2P)6.1 regulates the following: (1) systemic blood pressure; (2) the contractile state of arteries; (3) vascular smooth muscle cell migration; (4) proliferation; and/or (5) volume regulation. Mice lacking K(2P)6.1 (KO) were generated by deleting exon 1 of Kcnk6. Mean arterial blood pressure in both anesthetized and awake KO mice was increased by 17±2 and 26±3 mm Hg, respectively (P<0.05). The resting membrane potential in freshly dispersed vascular smooth muscle cells was depolarized by 17±2 mV in the KO compared with wild-type littermates (P<0.05). The contractile responses to KCl (P<0.05) and BAY K 8644 (P<0.01), an activator of L-type calcium channels, were enhanced in isolated segments of aorta from KO mice. However, there was no difference in the current density of L-type calcium channels. Responses to U46619, an agent that activates rho kinase, showed an enhanced contraction in aorta from KO mice (P<0.001). The BAY K 8644-mediated increase in contraction was decreased to wild-type levels when treated with Y27632, a rho kinase inhibitor, (P<0.05). K(2P)6.1 does not appear to be involved with migration, proliferation, or volume regulation in cultured vascular smooth muscle cells. We conclude that K(2P)6.1 deficiency induces vascular dysfunction and hypertension through a mechanism that may involve smooth muscle cell depolarization and enhanced rho kinase activity.
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Affiliation(s)
- Eric E Lloyd
- Department of Anesthesiology, Baylor College of Medicine, Houston, TX 77030, USA
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Namiranian K, Lloyd EE, Crossland RF, Marrelli SP, Taffet GE, Reddy AK, Hartley CJ, Bryan RM. Cerebrovascular responses in mice deficient in the potassium channel, TREK-1. Am J Physiol Regul Integr Comp Physiol 2010; 299:R461-9. [PMID: 20357027 PMCID: PMC2928619 DOI: 10.1152/ajpregu.00057.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 03/30/2010] [Indexed: 12/19/2022]
Abstract
We tested the hypothesis that TREK-1, a two-pore domain K channel, is involved with dilations in arteries. Because there are no selective activators or inhibitors of TREK-1, we generated a mouse line deficient in TREK-1. Endothelium-mediated dilations were not different in arteries from wild-type (WT) and TREK-1 knockout (KO) mice. This includes dilations of the middle cerebral artery to ATP, dilations of the basilar artery to ACh, and relaxations of the aorta to carbachol, a cholinergic agonist. The nitric oxide (NO) and endothelium-dependent hyperpolarizing factor components of ATP dilations were identical in the middle cerebral arteries of WT and TREK-1 KO mice. Furthermore, the NO and cyclooxygenase-dependent components were identical in the basilar arteries of the different genotypes. Dilations of the basilar artery to alpha-linolenic acid, an activator of TREK-1, were not affected by the absence of TREK-1. Whole cell currents recorded using patch-clamp techniques were similar in cerebrovascular smooth muscle cells (CVSMCs) from WT and TREK-1 KO mice. alpha-linolenic acid or arachidonic acid increased whole cell currents in CVSMCs from both WT and TREK-1 KO mice. The selective blockers of large-conductance Ca-activated K channels, penitrem A and iberiotoxin, blocked the increased currents elicited by either alpha-linolenic or arachidonic acid. In summary, dilations were similar in arteries from WT and TREK-1 KO mice. There was no sign of TREK-1-like currents in CVSMCs from WT mice, and there were no major differences in currents between the genotypes. We conclude that regulation of arterial diameter is not altered in mice lacking TREK-1.
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Affiliation(s)
- Khodadad Namiranian
- Department of Anesthesiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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