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Baldwin SN, Jepps TA, Greenwood IA. Cycling matters: Sex hormone regulation of vascular potassium channels. Channels (Austin) 2023; 17:2217637. [PMID: 37243715 PMCID: PMC10228406 DOI: 10.1080/19336950.2023.2217637] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/07/2023] [Accepted: 05/19/2023] [Indexed: 05/29/2023] Open
Abstract
Sex hormones and the reproductive cycle (estrus in rodents and menstrual in humans) have a known impact on arterial function. In spite of this, sex hormones and the estrus/menstrual cycle are often neglected experimental factors in vascular basic preclinical scientific research. Recent research by our own laboratory indicates that cyclical changes in serum concentrations of sex -hormones across the rat estrus cycle, primary estradiol, have significant consequences for the subcellular trafficking and function of KV. Vascular potassium channels, including KV, are essential components of vascular reactivity. Our study represents a small part of a growing field of literature aimed at determining the role of sex hormones in regulating arterial ion channel function. This review covers key findings describing the current understanding of sex hormone regulation of vascular potassium channels, with a focus on KV channels. Further, we highlight areas of research where the estrus cycle should be considered in future studies to determine the consequences of physiological oscillations in concentrations of sex hormones on vascular potassium channel function.
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Affiliation(s)
- Samuel N Baldwin
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas A Jepps
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Iain A Greenwood
- Vascular Biology Research Centre, Institute of Molecular and Clinical Sciences, St George’s University of London, London, UK
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2
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Li XT. The modulation of potassium channels by estrogens facilitates neuroprotection. Front Cell Dev Biol 2022; 10:998009. [PMID: 36393851 PMCID: PMC9643774 DOI: 10.3389/fcell.2022.998009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 10/11/2022] [Indexed: 08/31/2023] Open
Abstract
Estrogens, the sex hormones, have the potential to govern multiple cellular functions, such as proliferation, apoptosis, differentiation, and homeostasis, and to exert numerous beneficial influences for the cardiovascular system, nervous system, and bones in genomic and/or non-genomic ways. Converging evidence indicates that estrogens serve a crucial role in counteracting neurodegeneration and ischemic injury; they are thereby being considered as a potent neuroprotectant for preventing neurological diseases such as Alzheimer's disease and stroke. The underlying mechanism of neuroprotective effects conferred by estrogens is thought to be complex and multifactorial, and it remains obscure. It is well established that the K+ channels broadly expressed in a variety of neural subtypes determine the essential physiological features of neuronal excitability, and dysfunction of these channels is closely associated with diverse brain deficits, such as ataxia and epilepsy. A growing body of evidence supports a neuroprotective role of K+ channels in malfunctions of nervous tissues, with the channels even being a therapeutic target in clinical trials. As multitarget steroid hormones, estrogens also regulate the activity of distinct K+ channels to generate varying biological actions, and accumulated data delineate that some aspects of estrogen-mediated neuroprotection may arise from the impact on multiple K+ channels, including Kv, BK, KATP, and K2P channels. The response of these K+ channels after acute or chronic exposure to estrogens may oppose pathological abnormality in nervous cells, which serves to extend our understanding of these phenomena.
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Affiliation(s)
- Xian-Tao Li
- School of Medicine, Guizhou University, Guiyang, China
- Department of Neuroscience, South-Central University for Nationalities, Wuhan, China
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3
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Adiponectin Exerts Peripheral Inhibitory Effects on the Mouse Gastric Smooth Muscle through the AMPK Pathway. Int J Mol Sci 2020; 21:ijms21249617. [PMID: 33348652 PMCID: PMC7767160 DOI: 10.3390/ijms21249617] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/10/2020] [Accepted: 12/15/2020] [Indexed: 12/17/2022] Open
Abstract
Some adipokines, such as adiponectin (ADPN), other than being implicated in the central regulation of feeding behavior, may influence gastric motor responses, which are a source of peripheral signals that also influence food intake. The present study aims to elucidate the signaling pathways through which ADPN exerts its actions in the mouse gastric fundus. To this purpose, we used a multidisciplinary approach. The mechanical results showed that ADPN caused a decay of the strip basal tension, which was abolished by the nitric oxide (NO) synthesis inhibitor, L-NG-nitro arginine (L-NNA). The electrophysiological experiments confirmed that all ADPN effects were abolished by L-NNA, except for the reduction of Ca2+ current, which was instead prevented by the inhibitor of AMP-activated protein kinase (AMPK), dorsomorphin. The activation of the AMPK signaling by ADPN was confirmed by immunofluorescence analysis, which also revealed the ADPN R1 receptor (AdipoR1) expression in glial cells of the myenteric plexus. In conclusion, our results indicate that ADPN exerts an inhibitory action on the gastric smooth muscle by acting on AdipoR1 and involving the AMPK signaling pathway at the peripheral level. These findings provide novel bases for considering AMPK as a possible pharmacologic target for the potential treatment of obesity and eating disorders.
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Kirmiz M, Palacio S, Thapa P, King AN, Sack JT, Trimmer JS. Remodeling neuronal ER-PM junctions is a conserved nonconducting function of Kv2 plasma membrane ion channels. Mol Biol Cell 2018; 29:2410-2432. [PMID: 30091655 PMCID: PMC6233057 DOI: 10.1091/mbc.e18-05-0337] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The endoplasmic reticulum (ER) and plasma membrane (PM) form junctions crucial to ion and lipid signaling and homeostasis. The Kv2.1 ion channel is localized at ER–PM junctions in brain neurons and is unique among PM proteins in its ability to remodel these specialized membrane contact sites. Here, we show that this function is conserved between Kv2.1 and Kv2.2, which differ in their biophysical properties, modulation, and cellular expression. Kv2.2 ER–PM junctions are present at sites deficient in the actin cytoskeleton, and disruption of the actin cytoskeleton affects their spatial organization. Kv2.2-containing ER–PM junctions overlap with those formed by canonical ER–PM tethers. The ability of Kv2 channels to remodel ER–PM junctions is unchanged by point mutations that eliminate their ion conduction but eliminated by point mutations within the Kv2-specific proximal restriction and clustering (PRC) domain that do not impact their ion channel function. The highly conserved PRC domain is sufficient to transfer the ER–PM junction–remodeling function to another PM protein. Last, brain neurons in Kv2 double-knockout mice have altered ER–PM junctions. Together, these findings demonstrate a conserved in vivo function for Kv2 family members in remodeling neuronal ER–PM junctions that is distinct from their canonical role as ion-conducting channels shaping neuronal excitability.
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Affiliation(s)
- Michael Kirmiz
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Stephanie Palacio
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616
| | - Anna N King
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - James S Trimmer
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616.,Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616
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Cameron MA, Al Abed A, Buskila Y, Dokos S, Lovell NH, Morley JW. Differential effect of brief electrical stimulation on voltage-gated potassium channels. J Neurophysiol 2017; 117:2014-2024. [PMID: 28202576 DOI: 10.1152/jn.00915.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 02/13/2017] [Accepted: 02/13/2017] [Indexed: 02/03/2023] Open
Abstract
Electrical stimulation of neuronal tissue is a promising strategy to treat a variety of neurological disorders. The mechanism of neuronal activation by external electrical stimulation is governed by voltage-gated ion channels. This stimulus, typically brief in nature, leads to membrane potential depolarization, which increases ion flow across the membrane by increasing the open probability of these voltage-gated channels. In spiking neurons, it is activation of voltage-gated sodium channels (NaV channels) that leads to action potential generation. However, several other types of voltage-gated channels are expressed that also respond to electrical stimulation. In this study, we examine the response of voltage-gated potassium channels (KV channels) to brief electrical stimulation by whole cell patch-clamp electrophysiology and computational modeling. We show that nonspiking amacrine neurons of the retina exhibit a large variety of responses to stimulation, driven by different KV-channel subtypes. Computational modeling reveals substantial differences in the response of specific KV-channel subtypes that is dependent on channel kinetics. This suggests that the expression levels of different KV-channel subtypes in retinal neurons are a crucial predictor of the response that can be obtained. These data expand our knowledge of the mechanisms of neuronal activation and suggest that KV-channel expression is an important determinant of the sensitivity of neurons to electrical stimulation.NEW & NOTEWORTHY This paper describes the response of various voltage-gated potassium channels (KV channels) to brief electrical stimulation, such as is applied during prosthetic electrical stimulation. We show that the pattern of response greatly varies between KV channel subtypes depending on activation and inactivation kinetics of each channel. Our data suggest that problems encountered when artificially stimulating neurons such as cessation in firing at high frequencies, or "fading," may be attributed to KV-channel activation.
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Affiliation(s)
- Morven A Cameron
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - Yossi Buskila
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia; and.,Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, New South Wales, Australia
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Tanahashi Y, Wang B, Murakami Y, Unno T, Matsuyama H, Nagano H, Komori S. Inhibitory effects of SKF96365 on the activities of K(+) channels in mouse small intestinal smooth muscle cells. J Vet Med Sci 2015; 78:203-11. [PMID: 26498720 PMCID: PMC4785108 DOI: 10.1292/jvms.15-0346] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In order to investigate the effects of SKF96365 (SKF), which is a non-selective cationic channel blocker, on
K+ channel currents, we recorded currents through ATP sensitive K+ (IKATP),
voltage-gated K+ (IKv) and Ca2+ activated K+ channels
(IBK) in the absence and presence of SKF in single small intestinal myocytes of mice with
patch-clamp techniques. SKF (10 µM) reversibly abolished IKATP that was induced by
cromakalim (10 µM), which is a selective ATP sensitive K+ channel opener. These
inhibitory effects were induced in a concentration-dependent and voltage-independent manner. The 50%
inhibitory concentration (IC50) was 0.85 µM, which was obviously lower than that
reported for the muscarinic cationic current. In addition, SKF (1 µM ≈ the IC50
value in IKATP suppression) reversibly inhibited the IKv that was induced by repetitive
depolarizing pulses from −80 to 20 mV. However, the extent of the inhibitory effects was only ~30%. In
contrast, SKF (1 µM) had no significant effects on spontaneous transient IBK and
caffeine-induced IBK. These results indicated that SKF inhibited ATP sensitive K+
channels and voltage-gated K+ channels, with the ATP sensitive K+ channels being more
sensitive than the voltage-gated K+ channels. These inhibitory effects on K+ channels
should be considered when SKF is used as a cationic channel blocker.
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Affiliation(s)
- Yasuyuki Tanahashi
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan
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Law R, Levin M. Bioelectric memory: modeling resting potential bistability in amphibian embryos and mammalian cells. Theor Biol Med Model 2015; 12:22. [PMID: 26472354 PMCID: PMC4608135 DOI: 10.1186/s12976-015-0019-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 09/27/2015] [Indexed: 12/20/2022] Open
Abstract
Background Bioelectric gradients among all cells, not just within excitable nerve and muscle, play instructive roles in developmental and regenerative pattern formation. Plasma membrane resting potential gradients regulate cell behaviors by regulating downstream transcriptional and epigenetic events. Unlike neurons, which fire rapidly and typically return to the same polarized state, developmental bioelectric signaling involves many cell types stably maintaining various levels of resting potential during morphogenetic events. It is important to begin to quantitatively model the stability of bioelectric states in cells, to understand computation and pattern maintenance during regeneration and remodeling. Method To facilitate the analysis of endogenous bioelectric signaling and the exploitation of voltage-based cellular controls in synthetic bioengineering applications, we sought to understand the conditions under which somatic cells can stably maintain distinct resting potential values (a type of state memory). Using the Channelpedia ion channel database, we generated an array of amphibian oocyte and mammalian membrane models for voltage evolution. These models were analyzed and searched, by simulation, for a simple dynamical property, multistability, which forms a type of voltage memory. Results We find that typical mammalian models and amphibian oocyte models exhibit bistability when expressing different ion channel subsets, with either persistent sodium or inward-rectifying potassium, respectively, playing a facilitative role in bistable memory formation. We illustrate this difference using fast sodium channel dynamics for which a comprehensive theory exists, where the same model exhibits bistability under mammalian conditions but not amphibian conditions. In amphibians, potassium channels from the Kv1.x and Kv2.x families tend to disrupt this bistable memory formation. We also identify some common principles under which physiological memory emerges, which suggest specific strategies for implementing memories in bioengineering contexts. Conclusion Our results reveal conditions under which cells can stably maintain one of several resting voltage potential values. These models suggest testable predictions for experiments in developmental bioelectricity, and illustrate how cells can be used as versatile physiological memory elements in synthetic biology, and unconventional computation contexts. Electronic supplementary material The online version of this article (doi:10.1186/s12976-015-0019-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Robert Law
- Department of Neuroscience, Brown University, Box G, Providence, RI, 02912, USA.
| | - Michael Levin
- Department of Biology and Tufts Center for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA, 02155, USA.
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Liu DH, Huang X, Meng XM, Zhang CM, Lu HL, Kim YC, Xu WX. Exogenous H2 S enhances mice gastric smooth muscle tension through S-sulfhydration of KV 4.3, mediating the inhibition of the voltage-dependent potassium current. Neurogastroenterol Motil 2014; 26:1705-16. [PMID: 25292410 DOI: 10.1111/nmo.12451] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 09/12/2014] [Indexed: 12/30/2022]
Abstract
BACKGROUND Hydrogen sulfide (H2 S) has been shown to have an excitatory effect on gastric motility, but the underlying molecular mechanism is unclear. In this study, we aimed to investigate the possible targets of H2 S and determine how H2 S affects its target proteins during H2 S-induced contraction. METHODS Patch-clamp and potentiometric fluorescence dye were utilized to measure the electrophysiological changes. The Biotin-switch assay was utilized to detect the protein S-sulfhydration. The isometric tension measurement was conducted too. KEY RESULTS Exogenous H2 S enhanced the tonic contraction of gastric antral smooth muscle, and voltage-dependent potassium channel (KV ) blocker and Dithiothreitol (DTT, a reducing agent) abolished the excitatory effect of NaHS. Exogenous H2 S inhibited the fast inactivation component of the voltage-dependent potassium channel current (IKVfast ) in isolated gastric antral smooth muscle cells. H2 S inhibited the KV 4.3 current in H293 cells with heterologous expression of KV 4.3, but did not inhibit the KV 4.1 and KV 4.2 currents, which together contribute greatly to IKVfast . NaHS significantly decreased the membrane potential in cultured gastric smooth muscle cells, but the NaHS-induced depolarization was suppressed by knockdown of KV 4.3 and N-ethylamaleimide (NEM), a free thiol group blocker. In addition, NaHS sulfhydrated KV 4.3 in H293 cells and in gastric smooth muscle tissue. However, this S-sulfhydration was inhibited by NEM and DTT. Meanwhile the NaHS-induced inhibition of IKVfast and KV 4.3 was also blocked by NEM and DTT. CONCLUSIONS & INFERENCES These results suggest that exogenous H2 S sulfhydrates KV 4.3 to decrease the membrane potential, thereby enhancing the basal tension of gastric antral smooth muscle.
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Affiliation(s)
- D-H Liu
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
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9
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Pekala D, Baginskas A, Szkudlarek HJ, Raastad M. Components of action potential repolarization in cerebellar parallel fibres. J Physiol 2014; 592:4911-29. [PMID: 25239461 DOI: 10.1113/jphysiol.2014.280719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Repolarization of the presynaptic action potential is essential for transmitter release, excitability and energy expenditure. Little is known about repolarization in thin, unmyelinated axons forming en passant synapses, which represent the most common type of axons in the mammalian brain's grey matter.We used rat cerebellar parallel fibres, an example of typical grey matter axons, to investigate the effects of K(+) channel blockers on repolarization. We show that repolarization is composed of a fast tetraethylammonium (TEA)-sensitive component, determining the width and amplitude of the spike, and a slow margatoxin (MgTX)-sensitive depolarized after-potential (DAP). These two components could be recorded at the granule cell soma as antidromic action potentials and from the axons with a newly developed miniaturized grease-gap method. A considerable proportion of fast repolarization remained in the presence of TEA, MgTX, or both. This residual was abolished by the addition of quinine. The importance of proper control of fast repolarization was demonstrated by somatic recordings of antidromic action potentials. In these experiments, the relatively broad K(+) channel blocker 4-aminopyridine reduced the fast repolarization, resulting in bursts of action potentials forming on top of the DAP. We conclude that repolarization of the action potential in parallel fibres is supported by at least three groups of K(+) channels. Differences in their temporal profiles allow relatively independent control of the spike and the DAP, whereas overlap of their temporal profiles provides robust control of axonal bursting properties.
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Affiliation(s)
- Dobromila Pekala
- Department of Physiology, Emory University School of Medicine, Atlanta GA, USA
| | - Armantas Baginskas
- Department of Physics, Mathematics and Biophysics, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Hanna J Szkudlarek
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, Krakow, Poland
| | - Morten Raastad
- Department of Physiology, Emory University School of Medicine, Atlanta GA, USA
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Liu DH, Huang X, Guo X, Meng XM, Wu YS, Lu HL, Zhang CM, Kim YC, Xu WX. Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction. PLoS One 2014; 9:e86109. [PMID: 24516526 PMCID: PMC3916336 DOI: 10.1371/journal.pone.0086109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 12/05/2013] [Indexed: 11/18/2022] Open
Abstract
Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (KV) was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of KV activation was altered. The sensitivity of KV currents (IKV) to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a KV blocker, stays the same. The protein levels of KV4.3 and KV2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of KV4.3 and KV2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of KV channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of KV4.3 and KV2.2 may be involved in this process.
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Affiliation(s)
- Dong-Hai Liu
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Xu Huang
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Xin Guo
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Xiang-Min Meng
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Yi-Song Wu
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Hong-Li Lu
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Chun-Mei Zhang
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Young-chul Kim
- Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Chungbuk, Republic of Korea
| | - Wen-Xie Xu
- Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai, China
- * E-mail:
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Kenny EE, Pe'er I, Karban A, Ozelius L, Mitchell AA, Ng SM, Erazo M, Ostrer H, Abraham C, Abreu MT, Atzmon G, Barzilai N, Brant SR, Bressman S, Burns ER, Chowers Y, Clark LN, Darvasi A, Doheny D, Duerr RH, Eliakim R, Giladi N, Gregersen PK, Hakonarson H, Jones MR, Marder K, McGovern DPB, Mulle J, Orr-Urtreger A, Proctor DD, Pulver A, Rotter JI, Silverberg MS, Ullman T, Warren ST, Waterman M, Zhang W, Bergman A, Mayer L, Katz S, Desnick RJ, Cho JH, Peter I. A genome-wide scan of Ashkenazi Jewish Crohn's disease suggests novel susceptibility loci. PLoS Genet 2012; 8:e1002559. [PMID: 22412388 PMCID: PMC3297573 DOI: 10.1371/journal.pgen.1002559] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 01/12/2012] [Indexed: 12/19/2022] Open
Abstract
Crohn's disease (CD) is a complex disorder resulting from the interaction of intestinal microbiota with the host immune system in genetically susceptible individuals. The largest meta-analysis of genome-wide association to date identified 71 CD-susceptibility loci in individuals of European ancestry. An important epidemiological feature of CD is that it is 2-4 times more prevalent among individuals of Ashkenazi Jewish (AJ) descent compared to non-Jewish Europeans (NJ). To explore genetic variation associated with CD in AJs, we conducted a genome-wide association study (GWAS) by combining raw genotype data across 10 AJ cohorts consisting of 907 cases and 2,345 controls in the discovery stage, followed up by a replication study in 971 cases and 2,124 controls. We confirmed genome-wide significant associations of 9 known CD loci in AJs and replicated 3 additional loci with strong signal (p<5×10⁻⁶). Novel signals detected among AJs were mapped to chromosomes 5q21.1 (rs7705924, combined p = 2×10⁻⁸; combined odds ratio OR = 1.48), 2p15 (rs6545946, p = 7×10⁻⁹; OR = 1.16), 8q21.11 (rs12677663, p = 2×10⁻⁸; OR = 1.15), 10q26.3 (rs10734105, p = 3×10⁻⁸; OR = 1.27), and 11q12.1 (rs11229030, p = 8×10⁻⁹; OR = 1.15), implicating biologically plausible candidate genes, including RPL7, CPAMD8, PRG2, and PRG3. In all, the 16 replicated and newly discovered loci, in addition to the three coding NOD2 variants, accounted for 11.2% of the total genetic variance for CD risk in the AJ population. This study demonstrates the complementary value of genetic studies in the Ashkenazim.
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Affiliation(s)
- Eimear E. Kenny
- Department of Computer Sciences, Columbia University, New York, New York, United States of America
| | - Itsik Pe'er
- Department of Computer Sciences, Columbia University, New York, New York, United States of America
| | - Amir Karban
- Department of Gastroenterology, Rambam Health Care Campus, B. Rappaport Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Laurie Ozelius
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Adele A. Mitchell
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Sok Meng Ng
- Department of Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Monica Erazo
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Harry Ostrer
- Department of Pathology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Clara Abraham
- Department of Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Maria T. Abreu
- Division of Gastroenterology, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Gil Atzmon
- Genetic Core for Longevity, Institute for Aging Research and the Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Nir Barzilai
- Genetic Core for Longevity, Institute for Aging Research and the Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Steven R. Brant
- Meyerhoff Inflammatory Bowel Disease Center, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Susan Bressman
- Mirken Department of Neurology, Beth Israel Medical Center, New York, New York, United States of America
- The Saul R. Korey Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Edward R. Burns
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Yehuda Chowers
- Department of Gastroenterology, Rambam Health Care Campus, B. Rappaport Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Lorraine N. Clark
- Department of Pathology and Cell Biology, Columbia University, New York, New York, United States of America
| | - Ariel Darvasi
- The Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Dana Doheny
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Richard H. Duerr
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Rami Eliakim
- Department of Gastroenterology and Hepatology, Sheba Medical Center, Raman Gan, Israel
| | - Nir Giladi
- Department of Neurology, Tel Aviv Sourasky Medical Center, Sackler School of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Peter K. Gregersen
- Robert S. Boas Center for Genomics and Human Genetics, Feinstein Institute for Medical Research, North Shore LIJ Health System, Manhasset, New York, United States of America
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Michelle R. Jones
- Division of Endocrinology, Diabetes, and Metabolism, Graduate Program in Biomedical Sciences and Translational Medicine, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Karen Marder
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Dermot P. B. McGovern
- Department of Translational Medicine, Inflammatory Bowel and Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Jennifer Mulle
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Avi Orr-Urtreger
- Genetic Institute, Tel Aviv Sourasky Medical Center, Sackler School of Medicine, Tel Aviv University, Tel-Aviv, Israel
| | - Deborah D. Proctor
- Department of Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Ann Pulver
- Epidemiology-Genetics Program in Schizophrenia, Bipolar Disorders, and Related Disorders, Department of Psychiatry and Behavioral Sciences, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jerome I. Rotter
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | | | - Thomas Ullman
- Division of Gastroenterology, Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Stephen T. Warren
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, United States of America
- Departments of Biochemistry and Pediatrics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Matti Waterman
- Department of Gastroenterology, Rambam Health Care Campus, B. Rappaport Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Wei Zhang
- Department of Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Aviv Bergman
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Lloyd Mayer
- Division of Gastroenterology, Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Seymour Katz
- Albert Einstein College of Medicine, North Shore University Hospital-Long Island Jewish Hospital Systems, St. Francis Hospital, Great Neck, New York, United States of America
| | - Robert J. Desnick
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Judy H. Cho
- Department of Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
- * E-mail: (JH Cho) (JC); (I Peter) (IP)
| | - Inga Peter
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail: (JH Cho) (JC); (I Peter) (IP)
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12
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Kyle B, Bradley E, Ohya S, Sergeant GP, McHale NG, Thornbury KD, Hollywood MA. Contribution of Kv2.1 channels to the delayed rectifier current in freshly dispersed smooth muscle cells from rabbit urethra. Am J Physiol Cell Physiol 2011; 301:C1186-200. [PMID: 21813710 DOI: 10.1152/ajpcell.00455.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have characterized the native voltage-dependent K(+) (K(v)) current in rabbit urethral smooth muscle cells (RUSMC) and compared its pharmacological and biophysical properties with K(v)2.1 and K(v)2.2 channels cloned from the rabbit urethra and stably expressed in human embryonic kidney (HEK)-293 cells (HEK(Kv2.1) and HEK(Kv2.2)). RUSMC were perfused with Hanks' solution at 37°C and studied using the patch-clamp technique with K(+)-rich pipette solutions. Cells were bathed in 100 nM Penitrem A (Pen A) to block large-conductance Ca(2+)-activated K(+) (BK) currents and depolarized to +40 mV for 500 ms to evoke K(v) currents. These were unaffected by margatoxin, κ-dendrotoxin, or α-dendrotoxin (100 nM, n = 3-5) but were blocked by stromatoxin-1 (ScTx, IC(50) ∼130 nM), consistent with the idea that the currents were carried through K(v)2 channels. RNA was detected for K(v)2.1, K(v)2.2, and the silent subunit K(v)9.3 in urethral smooth muscle. Immunocytochemistry showed membrane staining for both K(v)2 subtypes and K(v)9.3 in isolated RUSMC. HEK(Kv2.1) and HEK(Kv2.2) currents were blocked in a concentration-dependent manner by ScTx, with estimated IC(50) values of ∼150 nM (K(v)2.1, n = 5) and 70 nM (K(v)2.2, n = 6). The mean half-maximal voltage (V(1/2)) of inactivation of the USMC K(v) current was -56 ± 3 mV (n = 9). This was similar to the HEK(Kv2.1) current (-55 ± 3 mV, n = 13) but significantly different from the HEK(Kv2.2) currents (-30 ± 3 mV, n = 11). Action potentials (AP) evoked from RUSMC studied under current-clamp mode were unaffected by ScTx. However, when ScTx was applied in the presence of Pen A, the AP duration was significantly prolonged. Similarly, ScTx increased the amplitude of spontaneous contractions threefold, but only after Pen A application. These data suggest that K(v)2.1 channels contribute significantly to the K(v) current in RUSMC.
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Affiliation(s)
- B Kyle
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
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13
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Zhong XZ, Abd-Elrahman KS, Liao CH, El-Yazbi AF, Walsh EJ, Walsh MP, Cole WC. Stromatoxin-sensitive, heteromultimeric Kv2.1/Kv9.3 channels contribute to myogenic control of cerebral arterial diameter. J Physiol 2010; 588:4519-37. [PMID: 20876197 DOI: 10.1113/jphysiol.2010.196618] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cerebral vascular smooth muscle contractility plays a crucial role in controlling arterial diameter and, thereby, blood flow regulation in the brain. A number of K(+) channels have been suggested to contribute to the regulation of diameter by controlling smooth muscle membrane potential (E(m)) and Ca(2+) influx. Previous studies indicate that stromatoxin (ScTx1)-sensitive, Kv2-containing channels contribute to the control of cerebral arterial diameter at 80 mmHg, but their precise role and molecular composition were not determined. Here, we tested if Kv2 subunits associate with 'silent' subunits from the Kv5, Kv6, Kv8 or Kv9 subfamilies to form heterotetrameric channels that contribute to control of diameter of rat middle cerebral arteries (RMCAs) over a range of intraluminal pressure from 10 to 100 mmHg. The predominant mRNAs expressed by RMCAs encode Kv2.1 and Kv9.3 subunits. Co-localization of Kv2.1 and Kv9.3 proteins at the plasma membrane of dissociated single RMCA myocytes was detected by proximity ligation assay. ScTx1-sensitive native current of RMCA myocytes and Kv2.1/Kv9.3 currents exhibited functional identity based on the similarity of their deactivation kinetics and voltage dependence of activation that were distinct from those of homomultimeric Kv2.1 channels. ScTx1 treatment enhanced the myogenic response of pressurized RMCAs between 40 and 100 mmHg, but this toxin also caused constriction between 10 and 40 mmHg that was not previously observed following inhibition of large conductance Ca(2+)-activated K(+) (BK(Ca)) and Kv1 channels. Taken together, this study defines the molecular basis of Kv2-containing channels and contributes to our understanding of the functional significance of their expression in cerebral vasculature. Specifically, our findings provide the first evidence of heteromultimeric Kv2.1/Kv9.3 channel expression in RMCA myocytes and their distinct contribution to control of cerebral arterial diameter over a wider range of E(m) and transmural pressure than Kv1 or BK(Ca) channels owing to their negative range of voltage-dependent activation.
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Affiliation(s)
- Xi Zoë Zhong
- The Smooth Muscle Research Group, Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, 3330 Hospital Drive N.W., Calgary, Alberta, Canada T2N 4N1
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14
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Jepps TA, Greenwood IA, Moffatt JD, Sanders KM, Ohya S. Molecular and functional characterization of Kv7 K+ channel in murine gastrointestinal smooth muscles. Am J Physiol Gastrointest Liver Physiol 2009; 297:G107-15. [PMID: 19389803 PMCID: PMC2711751 DOI: 10.1152/ajpgi.00057.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Members of the K(v)7 voltage-gated K(+) channel family are important determinants of cardiac and neuronal membrane excitability. Recently, we and others have shown that K(v)7 channels are also crucial regulators of smooth muscle activity. The aim of the present study was to assess the K(v)7 expression in different parts of the murine gastrointestinal (GI) tract and to assess their functional roles by use of pharmacological agents. Of KCNQ/K(v)7 members, both KCNQ4/K(v)7.4 and KCNQ5/K(v)7.5 genes and proteins were the most abundantly expressed K(v)7 channels in smooth muscles throughout the GI tract. Immunohistochemical staining also revealed that K(v)7.4 and K(v)7.5 but not K(v)7.1 were expressed in the circular muscle layer of the colon. In segments of distal colon circular muscle exhibiting spontaneous phasic contractions, the nonselective K(v)7 blockers XE991 and linopirdine increased the integral of tension. Increases in the integral of tension were also observed under conditions of neuronal blockade. Similar effects, although less marked, were observed in the proximal colon. As expected, the K(v)7.1-selective blocker chromanol 293B had no effect in either type of segment. These data show that K(v)7.x especially K(v)7.4 and K(v)7.5 are expressed in different regions of the murine gastrointestinal tract and blockers of K(v)7 channels augment inherent contractile activity. Drugs that selectively block K(v)7.4/7.5 might be promising therapeutics for the treatment of motility disorders such as constipation associated with irritable bowel syndrome.
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Affiliation(s)
- Thomas A. Jepps
- Division of Basic Medical Sciences, St George's, University of London, London, United Kingdom; Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada; and Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Iain A. Greenwood
- Division of Basic Medical Sciences, St George's, University of London, London, United Kingdom; Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada; and Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - James D. Moffatt
- Division of Basic Medical Sciences, St George's, University of London, London, United Kingdom; Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada; and Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Kenton M. Sanders
- Division of Basic Medical Sciences, St George's, University of London, London, United Kingdom; Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada; and Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Susumu Ohya
- Division of Basic Medical Sciences, St George's, University of London, London, United Kingdom; Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada; and Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
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15
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Heaps CL, Jeffery EC, Laine GA, Price EM, Bowles DK. Effects of exercise training and hypercholesterolemia on adenosine activation of voltage-dependent K+ channels in coronary arterioles. J Appl Physiol (1985) 2008; 105:1761-71. [PMID: 18832757 DOI: 10.1152/japplphysiol.90958.2008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Coronary arterioles from hypercholesterolemic swine display attenuated adenosine-mediated vasodilatation that is attributable to the elimination of voltage-dependent K(+) (Kv) channel stimulation. For the present study, we tested the hypotheses that exercise training would correct impaired adenosine-induced dilatation in coronary arterioles from hypercholesterolemic pigs through restoration of adenosine activation of Kv channels and that vasodilatation to the receptor-independent adenylyl cyclase activator, forskolin, would also be attenuated in arterioles from hypercholesterolemic pigs. Pigs were randomly assigned to a control (NC) or high-fat, high-cholesterol (HC) diet for 20 wk. Four weeks after the diet was initiated, pigs from both groups were assigned to exercise training (Ex; 5 days/wk for 16 wk) or sedentary (Sed) protocols, resulting in four groups of pigs: NC-Sed, NC-Ex, HC-Sed, and HC-Ex. Arterioles ( approximately 150 mum) from both HC-Sed and HC-Ex pigs displayed impaired adenosine-mediated dilatation that was attributable to the elimination of 4-aminopyridine (4-AP; 1 mM)-sensitive Kv channel activation compared with NC counterparts. Arteriolar smooth muscle whole cell Kv currents were significantly reduced in HC-Sed compared with NC-Sed, although HC-Ex and NC-Ex did not differ. Forskolin-mediated dilatation was attenuated by 4-AP (1 mM) and in a concentration-dependent manner by tetraethylammonium (TEA; 0.1-1 mM) in NC-Sed but not HC-Sed. Further, TEA-sensitive Kv currents were diminished in cells of HC-Sed compared with NC-Sed pigs. Quantitative RT-PCR revealed similar expression levels of Kv3.1 and 3.3 in arterioles of NC-Sed and HC-Sed swine with undetectable expression of Kv1.1, 3.2, and 3.4. Taken together, these results suggest that hypercholesterolemia-mediated attenuation of adenosine-induced vasodilatation in coronary arterioles is not corrected by exercise training and is likely attributable to an impairment in the pathway coupling adenylyl cyclase with a highly TEA-sensitive Kv channel isoform(s).
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Affiliation(s)
- Cristine L Heaps
- Michael E. DeBakey Institute for Comparative Cardiovascular Science and Biomedical Devices, Texas, USA.
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16
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Heitzmann D, Warth R. Physiology and pathophysiology of potassium channels in gastrointestinal epithelia. Physiol Rev 2008; 88:1119-82. [PMID: 18626068 DOI: 10.1152/physrev.00020.2007] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cells of the gastrointestinal tract are an important barrier between the "milieu interne" and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K(+) channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K(+) channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K(+) channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K(+) channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K(+) homeostasis occurs in colonic epithelia cells, where K(+) channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K(+) channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K(+) channels of the gastrointestinal tract.
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Affiliation(s)
- Dirk Heitzmann
- Institute of Physiology and Clinic and Policlinic for Internal Medicine II, Regensburg, Germany
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17
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Johnston J, Griffin SJ, Baker C, Skrzypiec A, Chernova T, Forsythe ID. Initial segment Kv2.2 channels mediate a slow delayed rectifier and maintain high frequency action potential firing in medial nucleus of the trapezoid body neurons. J Physiol 2008; 586:3493-509. [PMID: 18511484 DOI: 10.1113/jphysiol.2008.153734] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The medial nucleus of the trapezoid body (MNTB) is specialized for high frequency firing by expression of Kv3 channels, which minimize action potential (AP) duration, and Kv1 channels, which suppress multiple AP firing, during each calyceal giant EPSC. However, the outward K(+) current in MNTB neurons is dominated by another unidentified delayed rectifier. It has slow kinetics and a peak conductance of approximately 37 nS; it is half-activated at -9.2 +/- 2.1 mV and half-inactivated at -35.9 +/- 1.5 mV. It is blocked by several non-specific potassium channel antagonists including quinine (100 microm) and high concentrations of extracellular tetraethylammonium (TEA; IC(50) = 11.8 mM), but no specific antagonists were found. These characteristics are similar to recombinant Kv2-mediated currents. Quantitative RT-PCR showed that Kv2.2 mRNA was much more prevalent than Kv2.1 in the MNTB. A Kv2.2 antibody showed specific staining and Western blots confirmed that it recognized a protein approximately 110 kDa which was absent in brainstem tissue from a Kv2.2 knockout mouse. Confocal imaging showed that Kv2.2 was highly expressed in axon initial segments of MNTB neurons. In the absence of a specific antagonist, Hodgkin-Huxley modelling of voltage-gated conductances showed that Kv2.2 has a minor role during single APs (due to its slow activation) but assists recovery of voltage-gated sodium channels (Nav) from inactivation by hyperpolarizing interspike potentials during repetitive AP firing. Current-clamp recordings during high frequency firing and characterization of Nav inactivation confirmed this hypothesis. We conclude that Kv2.2-containing channels have a distinctive initial segment location and crucial function in maintaining AP amplitude by regulating the interspike potential during high frequency firing.
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Affiliation(s)
- Jamie Johnston
- MRC Toxicology Unit, University of Leicester, Leicester LE1 9HN, UK
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18
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Kito Y, Suzuki H. Role of K+ channels in the regulation of electrical spontaneous activity of the mouse small intestine. Pflugers Arch 2007; 455:505-14. [PMID: 17602242 DOI: 10.1007/s00424-007-0306-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 05/25/2007] [Accepted: 06/01/2007] [Indexed: 10/23/2022]
Abstract
The roles of K(+) channels in the regulation of slow waves and pacemaker potentials recorded from mouse small intestine were investigated using intracellular recording techniques in the presence of nifedipine. Iberiotoxin (0.1 microM) and charybdotoxin (0.1 microM) had no effect on the generation of slow waves recorded from circular smooth muscle cells. Apamin (0.3 microM) depolarized the membrane and decreased the amplitude of early, rapid repolarization of slow waves, without altering the amplitude, frequency, duration, or maximum rate of rise of the initial upstroke phase (dV/dt(max)). The early, rapid repolarization was enhanced by phenylephrine (15 microM). 4-Aminopyridine (4-AP, 5 mM) depolarized the membrane and increased the amplitude and dV/dt(max) of slow waves. Both apamin and 4-AP depolarized the membrane and decreased the amplitude and dV/dt(max) of pacemaker potentials recorded from interstitial cells of Cajal distributed in the myenteric region (ICC-MY). Membrane depolarization with a high-K(+) solution decreased the amplitude and dV/dt(max) of slow waves. These results suggest that apamin-sensitive K(+) conductance and 4-AP-sensitive K(+) conductance may contribute to the resting membrane potential of circular smooth muscle cells. The early, rapid repolarization of slow waves appears to result from the opening of apamin-sensitive K(+) conductance. 4-AP-sensitive K(+) conductance is likely to be activated in the initial upstroke component (primary component) of slow waves. In ICC-MY, membrane depolarization induced by apamin or 4-AP may result from electrotonic spread from smooth muscle cells.
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Affiliation(s)
- Yoshihiko Kito
- Department of Physiology, Nagoya City University Medical School, Nagoya, Japan.
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19
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Chen X, Johnston D. Properties of single voltage-dependent K+ channels in dendrites of CA1 pyramidal neurones of rat hippocampus. J Physiol 2004; 559:187-203. [PMID: 15218076 PMCID: PMC1665081 DOI: 10.1113/jphysiol.2004.068114] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Voltage-dependent K(+) channels in the apical dendrites of CA1 pyramidal neurones play important roles in regulating dendritic excitability, synaptic integration, and synaptic plasticity. Using cell-attached, voltage-clamp recordings, we found a large variability in the waveforms of macroscopic K(+) currents in the dendrites. With single-channel analysis, however, we were able to identify four types of voltage-dependent K(+) channels and we categorized them as belonging to delayed-rectifier, M-, D-, or A-type K(+) channels previously described from whole-cell recordings. Delayed-rectifier-type K(+) channels had a single-channel conductance of 19 +/- 0.5 pS, and made up the majority of the sustained K(+) current uniformly distributed along the apical dendrites. The M-type K(+) channels had a single-channel conductance of 11 +/- 0.8 pS, did not inactivate with prolonged membrane depolarization, deactivated with slow kinetics (time constant 100 +/- 6 ms at -40 mV), and were inhibited by bath-applied muscarinic agonist carbachol (10 microm). The D-type K(+) channels had a single-channel conductance of around 18 pS, and inactivated with a time constant of 98 +/- 4 ms at +54 mV. The A-type K(+) channels had a single-channel conductance of 6 +/- 0.6 pS, inactivated with a time constant of 23 +/- 2 ms at +54 mV, and contributed to the majority of the transient K(+) current previously described. These results suggest both functional and molecular complexity for K(+) channels in dendrites of CA1 pyramidal neurones.
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Affiliation(s)
- Xixi Chen
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
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20
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Thorneloe KS, Nelson MT. Properties and molecular basis of the mouse urinary bladder voltage-gated K+ current. J Physiol 2003; 549:65-74. [PMID: 12679374 PMCID: PMC2342925 DOI: 10.1113/jphysiol.2003.039859] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Potassium channels play an important role in controlling the excitability of urinary bladder smooth muscle (UBSM). Here we describe the biophysical, pharmacological and molecular properties of the mouse UBSM voltage-gated K+ current (IK(V)). The IK(V) activated, deactivated and inactivated slowly with time constants of 29.9 ms at +30 mV, 131 ms at -40 mV and 3.4 s at +20 mV. The midpoints of steady-state activation and inactivation curves were 1.1 mV and -61.4 mV, respectively. These properties suggest that IK(V) plays a role in regulating the resting membrane potential and contributes to the repolarization and after-hyperpolarization phases of action potentials. The IK(V) was blocked by tetraethylammonium ions with an IC50 of 5.2 mM and was unaffected by 1 mM 4-aminopyridine. RT-PCR for voltage-gated K+ channel (KV) subunits revealed the expression of Kv2.1, Kv5.1, Kv6.1, Kv6.2 and Kv6.3 in isolated UBSM myocytes. A comparison of the biophysical properties of UBSM IK(V) with those reported for Kv2.1 and Kv5.1 and/or Kv6 heteromultimeric channels demonstrated a marked similarity. We propose that heteromultimeric channel complexes composed of Kv2.1 and Kv5.1 and/or Kv6 subunits form the molecular basis of the mouse UBSM IK(V).
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Affiliation(s)
- Kevin S Thorneloe
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA
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21
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Knock GA, Smirnov SV, Aaronson PI. Voltage-gated K+ currents in freshly isolated myocytes of the pregnant human myometrium. J Physiol 1999; 518 ( Pt 3):769-81. [PMID: 10420013 PMCID: PMC2269461 DOI: 10.1111/j.1469-7793.1999.0769p.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/1998] [Accepted: 04/21/1999] [Indexed: 11/29/2022] Open
Abstract
1. Voltage-gated K+ currents in human myometrium are not well characterized, and were therefore investigated, using the whole-cell patch clamp technique, in freshly isolated myometrial smooth muscle cells from pregnant women at term. 2. Three types of voltage-gated K+ currents were identified. IK1 was a 4-aminopyridine-insensitive current with a negative half-inactivation (V0.5 = -61 to -67 mV) and negative activation characteristics (threshold between -60 and -40 mV) and slow kinetics. IK2 was a 4-aminopyridine-sensitive current (half-maximal block at approximately 1 mM) with relatively positive half-inactivation (V0.5 = -30 mV) and activation characteristics (threshold between -40 and -30 mV) and faster kinetics. IK,A was a 4-aminopyridine-sensitive current with a negative inactivation and very fast inactivation kinetics. 3. Both IK1 and IK2 were sensitive to high concentrations of tetraethylammonium (half-maximal block at approximately 3 mM) and low concentrations of clofilium (half-maximal block by 3-10 microM). 4. IK1 and IK2 were unevenly distributed between myometrial cells, most cells possessing either IK1 (30 cells) or IK2 (24 cells) as the predominant current. 5. The characteristics of these currents suggest a possible function in the control of membrane potentials and smooth muscle quiescence in the pregnant human myometrium.
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Affiliation(s)
- G A Knock
- London Myometrial Group and Division of Pharmacology and Therapeutics, King's College London, St Thomas' Campus, Lambeth Palace Road, London SE1 7EH, UK
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Clément-Chomienne O, Ishii K, Walsh MP, Cole WC. Identification, cloning and expression of rabbit vascular smooth muscle Kv1.5 and comparison with native delayed rectifier K+ current. J Physiol 1999; 515 ( Pt 3):653-67. [PMID: 10066895 PMCID: PMC2269178 DOI: 10.1111/j.1469-7793.1999.653ab.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. The molecular basis of voltage-gated, delayed rectifier K+ (KDR) channels in vascular smooth muscle cells is poorly defined. In this study we employed (i) an antibody against Kv1.5 and (ii) a cDNA clone encoding Kv1.5 derived from rabbit portal vein (RPV) to demonstrate Kv1.5 expression in RPV and to compare the properties of RPVKv1.5 expressed in mammalian cells with those of native RPV KDR current. 2. Expression of Kv1.5 channel protein in RPV was demonstrated by (i) immunocytolocalization of an antibody raised against a C-terminal epitope of mouse cardiac Kv1.5 in permeabilized, freshly isolated RPV smooth muscle cells and (ii) isolation of a cDNA clone encoding RPVKv1.5 by reverse transcription-polymerase chain reaction (RT-PCR) using mRNA derived from endothelium-denuded and adventitia-free RPV. 3. RPVKv1.5 cDNA was expressed in mammalian L cells and human embryonic kidney (HEK293) cells and the properties of the expressed channels compared with those of native KDR channels of freshly dispersed myocytes under identical conditions. 4. The kinetics and voltage dependence of activation of L cell-expressed RPVKv1.5 and native KDR current were identical, as were the kinetics of recovery from inactivation and single channel conductance. In contrast, there was little similarity between HEK293 cell-expressed RPVKv1.5 and native KDR current. 5. Inactivation occurred with the same voltage for half-maximal availability, but the kinetics and slope constant for the voltage dependence of inactivation for L cell-expressed RPVKv1.5 and the native current were different: slow time constants were 6.5 +/- 0.6 and 3.5 +/- 0.4 s and slope factors were 4.7 +/- 0.2 and 7.0 +/- 0.8 mV, respectively. 6. This study provides immunofluorescence and functional evidence that Kv1.5 alpha-subunits are a component of native KDR channels of vascular smooth muscle cells of RPV. However, the differences in kinetics and voltage sensitivity of inactivation between L cell- and HEK293 cell-expressed channels and native KDR channels provide functional evidence that vascular KDR current is not due to homomultimers of RPV Kv1.5 alone. The channel structure may be more complex, involving heteromultimers and modulatory Kvbeta-subunits, and/or native KDR current may have other components involving Kvalpha-subunits of other families.
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Affiliation(s)
- O Clément-Chomienne
- Smooth Muscle Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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Koh SD, Ward SM, Dick GM, Epperson A, Bonner HP, Sanders KM, Horowitz B, Kenyon JL. Contribution of delayed rectifier potassium currents to the electrical activity of murine colonic smooth muscle. J Physiol 1999; 515 ( Pt 2):475-87. [PMID: 10050014 PMCID: PMC2269159 DOI: 10.1111/j.1469-7793.1999.475ac.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. We used intracellular microelectrodes to record the membrane potential (Vm) of intact murine colonic smooth muscle. Electrical activity consisted of spike complexes separated by quiescent periods (Vm approximately -60 mV). The spike complexes consisted of about a dozen action potentials of approximately 30 mV amplitude. Tetraethylammonium (TEA, 1-10 mM) had little effect on the quiescent periods but increased the amplitude of the action potential spikes. 4-Aminopyridine (4-AP, >= 5 mM) caused continuous spiking. 2. Voltage clamp of isolated myocytes identified delayed rectifier K+ currents that activated rapidly (time to half-maximum current, 11.5 ms at 0 mV) and inactivated in two phases (tauf = 96 ms, taus = 1.5 s at 0 mV). The half-activation voltage of the permeability was -27 mV, with significant activation at -50 mV. 3. TEA (10 mM) reduced the outward current at potentials positive to 0 mV. 4-AP (5 mM) reduced the early current but increased outward current at later times (100-500 ms) consistent with block of resting channels relieved by depolarization. 4-AP inhibited outward current at potentials negative to -20 mV, potentials where TEA had no effect. 4. Qualitative PCR amplification of mRNA identified transcripts encoding delayed rectifier K+ channel subunits Kv1.6, Kv4.1, Kv4.2, Kv4.3 and the Kvbeta1.1 subunit in murine colon myocytes. mRNA encoding Kv 1.4 was not detected. 5. We find that TEA-sensitive delayed rectifier currents are important determinants of action potential amplitude but not rhythmicity. Delayed rectifier currents sensitive to 4-AP are important determinants of rhythmicity but not action potential amplitude.
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Affiliation(s)
- S D Koh
- Department of Physiology and Cell Biology/MS 352, University of Nevada School of Medicine, Reno, NV 89557, USA.
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