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Sheak JR, Yan S, Weise-Cross L, Ahmadian R, Walker BR, Jernigan NL, Resta TC. PKCβ and reactive oxygen species mediate enhanced pulmonary vasoconstrictor reactivity following chronic hypoxia in neonatal rats. Am J Physiol Heart Circ Physiol 2020; 318:H470-H483. [PMID: 31922892 DOI: 10.1152/ajpheart.00629.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Reactive oxygen species (ROS), mitochondrial dysfunction, and excessive vasoconstriction are important contributors to chronic hypoxia (CH)-induced neonatal pulmonary hypertension. On the basis of evidence that PKCβ and mitochondrial oxidative stress are involved in several cardiovascular and metabolic disorders, we hypothesized that PKCβ and mitochondrial ROS (mitoROS) signaling contribute to enhanced pulmonary vasoconstriction in neonatal rats exposed to CH. To test this hypothesis, we examined effects of the PKCβ inhibitor LY-333,531, the ROS scavenger 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (TEMPOL), and the mitochondrial antioxidants mitoquinone mesylate (MitoQ) and (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (MitoTEMPO) on vasoconstrictor responses in saline-perfused lungs (in situ) or pressurized pulmonary arteries from 2-wk-old control and CH (12-day exposure, 0.5 atm) rats. Lungs from CH rats exhibited greater basal tone and vasoconstrictor sensitivity to 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F2α (U-46619). LY-333,531 and TEMPOL attenuated these effects of CH, while having no effect in lungs from control animals. Basal tone was similarly elevated in isolated pulmonary arteries from neonatal CH rats compared with control rats, which was inhibited by both LY-333,531 and mitochondria-targeted antioxidants. Additional experiments assessing mitoROS generation with the mitochondria-targeted ROS indicator MitoSOX revealed that a PKCβ-mitochondrial oxidant signaling pathway can be pharmacologically stimulated by the PKC activator phorbol 12-myristate 13-acetate in primary cultures of pulmonary artery smooth muscle cells (PASMCs) from control neonates. Finally, we found that neonatal CH increased mitochondrially localized PKCβ in pulmonary arteries as assessed by Western blotting of subcellular fractions. We conclude that PKCβ activation leads to mitoROS production in PASMCs from neonatal rats. Furthermore, this signaling axis may account for enhanced pulmonary vasoconstrictor sensitivity following CH exposure.NEW & NOTEWORTHY This research demonstrates a novel contribution of PKCβ and mitochondrial reactive oxygen species signaling to increased pulmonary vasoconstrictor reactivity in chronically hypoxic neonates. The results provide a potential mechanism by which chronic hypoxia increases both basal and agonist-induced pulmonary arterial smooth muscle tone, which may contribute to neonatal pulmonary hypertension.
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Affiliation(s)
- Joshua R Sheak
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Simin Yan
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Laura Weise-Cross
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Rosstin Ahmadian
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Benjimen R Walker
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Nikki L Jernigan
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
| | - Thomas C Resta
- Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico
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2
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Tengah A, Syed NIH, Talip STA, Bujang SNB, Kennedy C. Comparison of signalling mechanisms underlying UTP-evoked vasoconstriction of rat pulmonary and tail arteries. Eur J Pharmacol 2018; 837:45-52. [PMID: 30170065 DOI: 10.1016/j.ejphar.2018.08.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 08/22/2018] [Accepted: 08/24/2018] [Indexed: 12/16/2022]
Abstract
The endogenous nucleotide, UTP, acts at smooth muscle P2Y receptors to constrict rat pulmonary and tail arteries, but the underlying signalling pathways are poorly understood. The aim was to characterise the contribution of Ca2+ release and influx, rho kinase and protein kinase C to these contractions. Isometric tension was recorded from endothelium-denuded rat intralobar pulmonary and tail artery rings mounted on a wire myograph. Contractions were evoked by UTP and peak amplitude measured. Thapsigargin (1 µM), but not ryanodine (10 µM), significantly depressed contractions in both by 30-40% (P < 0.05). Nifedipine (1 µM) significantly reduced contractions in tail artery by ~60% (P < 0.01). Y27632 (10 µM), a rho kinase inhibitor and GF109203X (10 µM), a protein kinase C inhibitor, each significantly reduced pulmonary vasoconstriction by ~20%, and tail artery contractions by ~80% and ~40%, respectively (P < 0.01). In pulmonary artery, Y27632, GF109203X and thapsigargin, acted in an additive manner, but nifedipine less so. Adding all four together abolished the UTP response. In tail artery, Y27632 plus thapsigargin or GF109203X or nifedipine abolished contractions. Thapsigargin, GF109203X and nifedipine, coapplied pair-wise, acted additively and applying all three together abolished UTP-evoked contractions. So, Ca2+ release from the sarcoplasmic reticulum and influx through Cav1.2 channels, but not ryanodine receptors, play significant roles in UTP-evoked vasoconstriction of rat pulmonary and tail arteries. Rho kinase and protein kinase C are also involved, but more so in tail artery. Thus UTP activates multiple signalling mechanisms that lead to vasoconstriction, but their relative importance differs in pulmonary compared with systemic arteries.
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Affiliation(s)
- Asrin Tengah
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Nawazish-I-Husain Syed
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Siti Tajidah Abdul Talip
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Siti Nur Basirah Bujang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
| | - Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
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3
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Panhwar F, Rainbow RD, Jackson R, Davies NW. Ca2+ dependent but PKC independent signalling mediates UTP induced contraction of rat mesenteric arteries. J Smooth Muscle Res 2016; 51:58-69. [PMID: 26447104 PMCID: PMC5137259 DOI: 10.1540/jsmr.51.58] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Uridine triphosphate (UTP) can be released from damaged cells to cause vasoconstriction.
Although UTP is known to act through P2Y receptors and PLC activation in vascular smooth
muscle, the role of PKC in generating the response is somewhat unclear. Here we have used
Tat-linked membrane permeable peptide inhibitors of PKC to assess the general role of PKC
and also of specific isoforms of PKC in the UTP induced contraction of rat mesenteric
artery. We examined the effect of PKC inhibition on UTP induced contraction, increased
cytoplasmic Ca2+ and reduction of K+ currents and found that PKC
inhibition caused a relatively small attenuation of contraction but had little effect on
changes in cytoplasmic Ca2+. UTP attenuation of both voltage-gated
(Kv) and ATP-dependent (KATP) K+ currents was abolished
when intracellular Ca2+ was decreased from 100 to 20 nM. PKC inhibition reduced
slightly the ability of UTP to attenuate Kv currents but had no effect on
KATP current inhibition. In conclusion, both UTP induced contraction of
mesenteric artery and the inhibition of Kv and KATP currents of
mesenteric artery smooth muscle cells by UTP are relatively independent of PKC activation;
furthermore, the inhibition of both Kv and KATP currents requires
intracellular Ca2+.
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Affiliation(s)
- Fouzia Panhwar
- Departments of Cell Physiology & Pharmacology, University of Leicester, Leicester, UK
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4
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Eddinger TJ. Smooth muscle-protein translocation and tissue function. Anat Rec (Hoboken) 2015; 297:1734-46. [PMID: 25125185 DOI: 10.1002/ar.22970] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 03/18/2014] [Accepted: 03/18/2014] [Indexed: 01/25/2023]
Abstract
Smooth muscle (SM) tissue is a complex organization of multiple cell types and is regulated by numerous signaling molecules (neurotransmitters, hormones, cytokines, etc.). SM contractile function can be regulated via expression and distribution of the contractile and cytoskeletal proteins, and activation of any of the second messenger pathways that regulate them. Spatial-temporal changes in the contractile, cytoskeletal or regulatory components of SM cells (SMCs) have been proposed to alter SM contractile activity. Ca(2+) sensitization/desensitization can occur as a result of changes at any of these levels, and specific pathways have been identified at all of these levels. Understanding when and how proteins can translocate within the cytoplasm, or to-and-from the plasmalemma and the cytoplasm to alter contractile activity is critical. Numerous studies have reported translocation of proteins associated with the adherens junction and G protein-coupled receptor activation pathways in isolated SMC systems. Specific examples of translocation of vinculin to and from the adherens junction and protein kinase C (PKC) and 17 kDa PKC-potentiated inhibitor of myosin light chain phosphatase (CPI-17) to and from the plasmalemma in isolated SMC systems but not in intact SM tissues are discussed. Using both isolated SMC systems and SM tissues in parallel to pursue these studies will advance our understanding of both the role and mechanism of these pathways as well as their possible significance for Ca(2+) sensitization in intact SM tissues and organ systems.
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Affiliation(s)
- Thomas J Eddinger
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
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5
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Steady-state modulation of voltage-gated K+ channels in rat arterial smooth muscle by cyclic AMP-dependent protein kinase and protein phosphatase 2B. PLoS One 2015; 10:e0121285. [PMID: 25793374 PMCID: PMC4368632 DOI: 10.1371/journal.pone.0121285] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 01/29/2015] [Indexed: 01/17/2023] Open
Abstract
Voltage-gated potassium channels (Kv) are important regulators of membrane potential in vascular smooth muscle cells, which is integral to controlling intracellular Ca2+ concentration and regulating vascular tone. Previous work indicates that Kv channels can be modulated by receptor-driven alterations of cyclic AMP-dependent protein kinase (PKA) activity. Here, we demonstrate that Kv channel activity is maintained by tonic activity of PKA. Whole-cell recording was used to assess the effect of manipulating PKA signalling on Kv and ATP-dependent K+ channels of rat mesenteric artery smooth muscle cells. Application of PKA inhibitors, KT5720 or H89, caused a significant inhibition of Kv currents. Tonic PKA-mediated activation of Kv appears maximal as application of isoprenaline (a β-adrenoceptor agonist) or dibutyryl-cAMP failed to enhance Kv currents. We also show that this modulation of Kv by PKA can be reversed by protein phosphatase 2B/calcineurin (PP2B). PKA-dependent inhibition of Kv by KT5720 can be abrogated by pre-treatment with the PP2B inhibitor cyclosporin A, or inclusion of a PP2B auto-inhibitory peptide in the pipette solution. Finally, we demonstrate that tonic PKA-mediated modulation of Kv requires intact caveolae. Pre-treatment of the cells with methyl-β-cyclodextrin to deplete cellular cholesterol, or adding caveolin-scaffolding domain peptide to the pipette solution to disrupt caveolae-dependent signalling each attenuated PKA-mediated modulation of the Kv current. These findings highlight a novel, caveolae-dependent, tonic modulatory role of PKA on Kv channels providing new insight into mechanisms and the potential for pharmacological manipulation of vascular tone.
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6
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Zhang Y, Hermanson ME, Eddinger TJ. Tonic and phasic smooth muscle contraction is not regulated by the PKCα - CPI-17 pathway in swine stomach antrum and fundus. PLoS One 2013; 8:e74608. [PMID: 24058600 PMCID: PMC3776813 DOI: 10.1371/journal.pone.0074608] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 08/04/2013] [Indexed: 01/31/2023] Open
Abstract
Regulation of myosin light chain phosphatase (MLCP) via protein kinase C (PKC) and the 17 kDa PKC-potentiated inhibitor of myosin light chain phosphatase (CPI-17) has been reported as a Ca2+ sensitization signaling pathway in smooth muscle (SM), and thus may be involved in tonic vs. phasic contractions. This study examined the protein expression and spatial-temporal distribution of PKCα and CPI-17 in intact SM tissues. KCl or carbachol (CCh) stimulation of tonic stomach fundus SM generates a sustained contraction while the phasic stomach antrum generates a transient contraction. In addition, the tonic fundus generates greater relative force than phasic antrum with 1 µM phorbol 12, 13-dibutyrate (PDBu) stimulation which is reported to activate the PKCα – CPI-17 pathway. Western blot analyses demonstrated that this contractile difference was not caused by a difference in the protein expression of PKCα or CPI-17 between these two tissues. Immunohistochemical results show that the distribution of PKCα in the longitudinal and circular layers of the fundus and antrum do not differ, being predominantly localized near the SM cell plasma membrane. Stimulation of either tissue with 1 µM PDBu or 1 µM CCh does not alter this peripheral PKCα distribution. There are no differences between these two tissues for the CPI-17 distribution, but unlike the PKCα distribution, CPI-17 appears to be diffusely distributed throughout the cytoplasm under relaxed tissue conditions but shifts to a primarily peripheral distribution at the plasma membrane with stimulation of the tissues with 1 µM PDBu or 1 µM CCh. Results from double labeling show that neither PKCα nor CPI-17 co-localize at the adherens junction (vinculin/talin) at the membrane but they do co-localize with each other and with caveoli (caveolin) at the membrane. This lack of difference suggests that the PKCα - CPI-17 pathway is not responsible for the tonic vs. phasic contractions observed in stomach fundus and antrum.
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Affiliation(s)
- Yu Zhang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, United States of America
| | - Meghan E. Hermanson
- Department of Biology, Bradley University, Peoria, Illinois, United States of America
| | - Thomas J. Eddinger
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, United States of America
- * E-mail:
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7
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Vascular endothelial cells mediate mechanical stimulation-induced enhancement of endothelin hyperalgesia via activation of P2X2/3 receptors on nociceptors. J Neurosci 2013; 33:2849-59. [PMID: 23407944 DOI: 10.1523/jneurosci.3229-12.2013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Endothelin-1 (ET-1) is unique among a broad range of hyperalgesic agents in that it induces hyperalgesia in rats that is markedly enhanced by repeated mechanical stimulation at the site of administration. Antagonists to the ET-1 receptors, ET(A) and ET(B), attenuated both initial as well as stimulation-induced enhancement of hyperalgesia (SIEH) by endothelin. However, administering antisense oligodeoxynucleotide to attenuate ET(A) receptor expression on nociceptors attenuated ET-1 hyperalgesia but had no effect on SIEH, suggesting that this is mediated via a non-neuronal cell. Because vascular endothelial cells are both stretch sensitive and express ET(A) and ET(B) receptors, we tested the hypothesis that SIEH is dependent on endothelial cells by impairing vascular endothelial function with octoxynol-9 administration; this procedure eliminated SIEH without attenuating ET-1 hyperalgesia. A role for protein kinase Cε (PKCε), a second messenger implicated in the induction and maintenance of chronic pain, was explored. Intrathecal antisense for PKCε did not inhibit either ET-1 hyperalgesia or SIEH, suggesting no role for neuronal PKCε; however, administration of a PKCε inhibitor at the site of testing selectively attenuated SIEH. Compatible with endothelial cells releasing ATP in response to mechanical stimulation, P2X(2/3) receptor antagonists eliminated SIEH. The endothelium also appears to contribute to hyperalgesia in two ergonomic pain models (eccentric exercise and hindlimb vibration) and in a model of endometriosis. We propose that SIEH is produced by an effect of ET-1 on vascular endothelial cells, sensitizing its release of ATP in response to mechanical stimulation; ATP in turn acts at the nociceptor P2X(2/3) receptor.
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8
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Abstract
Inositol 1,4,5-trisphosphate (IP(3)) is a ubiquitous second messenger, derived from the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)) by enzymes of the phospholipase C (PLC) family. Binding of IP(3) to its cognate receptor in the endoplasmic reticulum membrane leads to release of Ca(2+) into the cytoplasm, which is involved in the regulation of an array of cellular functions. Traditional techniques for the detection of IP(3) have required the extraction of a large number of cells, with limitations in the time resolution of changes in IP(3) and an inability to obtain detailed information on the dynamics of this second messenger in single cells. Recent progress in this field has led to the development of a number of genetically encoded fluorescent biosensors, which upon recombinant expression are able selectively to detect real-time changes in IP(3) in single live cells. In this chapter, I detail protocols for the expression, visualization (by confocol or fluorescence microscopy), and interpretation of data obtained with such biosensors expressed in mammalian cells.
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Affiliation(s)
- Carl P Nelson
- Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care, and Pain Management, Leicester Royal Infirmary, University of Leicester, Leicester, UK.
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9
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Aziz Q, Thomas AM, Khambra T, Tinker A. Regulation of the ATP-sensitive potassium channel subunit, Kir6.2, by a Ca2+-dependent protein kinase C. J Biol Chem 2011; 287:6196-207. [PMID: 22207763 DOI: 10.1074/jbc.m111.243923] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of ATP-sensitive potassium (K(ATP)) channels is governed by the concentration of intracellular ATP and ADP and is thus responsive to the metabolic status of the cell. Phosphorylation of K(ATP) channels by protein kinase A (PKA) or protein kinase C (PKC) results in the modulation of channel activity and is particularly important in regulating smooth muscle tone. At the molecular level the smooth muscle channel is composed of a sulfonylurea subunit (SUR2B) and a pore-forming subunit Kir6.1 and/or Kir6.2. Previously, Kir6.1/SUR2B channels have been shown to be inhibited by PKC, and Kir6.2/SUR2B channels have been shown to be activated or have no response to PKC. In this study we have examined the modulation of channel complexes formed of the inward rectifier subunit, Kir6.2, and the sulfonylurea subunit, SUR2B. Using a combination of biochemical and electrophysiological techniques we show that this complex can be inhibited by protein kinase C in a Ca(2+)-dependent manner and that this inhibition is likely to be as a result of internalization. We identify a residue in the distal C terminus of Kir6.2 (Ser-372) whose phosphorylation leads to down-regulation of the channel complex. This inhibitory effect is distinct from activation which is seen with low levels of channel activity.
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Affiliation(s)
- Qadeer Aziz
- William Harvey Heart Centre, Barts and the London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, United Kingdom
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10
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Morris GE, Nelson CP, Brighton PJ, Standen NB, Challiss RAJ, Willets JM. Arrestins 2 and 3 differentially regulate ETA and P2Y2 receptor-mediated cell signaling and migration in arterial smooth muscle. Am J Physiol Cell Physiol 2011; 302:C723-34. [PMID: 22159081 DOI: 10.1152/ajpcell.00202.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Overstimulation of endothelin type A (ET(A)) and nucleotide (P2Y) Gα(q)-coupled receptors in vascular smooth muscle causes vasoconstriction, hypertension, and, eventually, hypertrophy and vascular occlusion. G protein-coupled receptor kinases (GRKs) and arrestin proteins are sequentially recruited by agonist-occupied Gα(q)-coupled receptors to terminate phospholipase C signaling, preventing prolonged/inappropriate contractile signaling. However, these proteins also play roles in the regulation of several mitogen-activated protein kinase (MAPK) signaling cascades known to be essential for vascular remodeling. Here we investigated whether different arrestin isoforms regulate endothelin and nucleotide receptor MAPK signaling in rat aortic smooth muscle cells (ASMCs). When intracellular Ca(2+) levels were assessed in isolated ASMCs loaded with Ca(2+)-sensitive dyes, P2Y(2) and ET(A) receptor desensitization was attenuated by selective small-interfering (si)RNA-mediated depletion of G protein-coupled receptor kinase 2 (GRK2). Using similar siRNA techniques, knockdown of arrestin2 prevented P2Y(2) receptor desensitization and enhanced and prolonged p38 and ERK MAPK signals, while arrestin3 depletion was ineffective. Conversely, arrestin3 knockdown prevented ET(A) receptor desensitization and attenuated ET1-stimulated p38 and ERK signals, while arrestin2 depletion had no effect. Using Transwell assays to assess agonist-stimulated ASMC migration, we found that UTP-stimulated migration was markedly attenuated following arrestin2 depletion, while ET1-stimulated migration was attenuated following knockdown of either arrestin. These data highlight a differential arrestin-dependent regulation of ET(A) and P2Y(2) receptor-stimulated MAPK signaling. GRK2 and arrestin expression are essential for agonist-stimulated ASMC migration, which, as a key process in vascular remodeling, highlights the potential roles of GRK2 and arrestin proteins in the progression of vascular disease.
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Affiliation(s)
- Gavin E Morris
- Dept. of Cancer Studies and Molecular Medicine, Leicester Royal Infirmary, Leicester, UK
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11
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Barrows ND, Nelson OL, Robbins CT, Rourke BC. Increased cardiac alpha-myosin heavy chain in left atria and decreased myocardial insulin-like growth factor (Igf-I) expression accompany low heart rate in hibernating grizzly bears. Physiol Biochem Zool 2011; 84:1-17. [PMID: 21117961 DOI: 10.1086/657589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Grizzly bears (Ursus arctos horribilis) tolerate extended periods of extremely low heart rate during hibernation without developing congestive heart failure or cardiac chamber dilation. Left ventricular atrophy and decreased left ventricular compliance have been reported in this species during hibernation. We evaluated the myocardial response to significantly reduced heart rate during hibernation by measuring relative myosin heavy-chain (MyHC) isoform expression and expression of a set of genes important to muscle plasticity and mass regulation in the left atria and left ventricles of active and hibernating bears. We supplemented these data with measurements of systolic and diastolic function via echocardiography in unanesthetized grizzly bears. Atrial strain imaging revealed decreased atrial contractility, decreased expansion/reservoir function (increased atrial stiffness), and decreased passive-filling function (increased ventricular stiffness) in hibernating bears. Relative MyHC-α protein expression increased significantly in the atrium during hibernation. The left ventricle expressed 100% MyHC-β protein in both groups. Insulin-like growth factor (IGF-I) mRNA expression was reduced by ∼50% in both chambers during hibernation, consistent with the ventricular atrophy observed in these bears. Interestingly, mRNA expression of the atrophy-related ubiquitin ligases Muscle Atrophy F-box (MAFBx) and Muscle Ring Finger 1 did not increase, nor did expression of myostatin or hypoxia-inducible factor 1α (HIF-1α). We report atrium-specific decreases of 40% and 50%, respectively, in MAFBx and creatine kinase mRNA expression during hibernation. Decreased creatine kinase expression is consistent with lowered energy requirements and could relate to reduced atrial emptying function during hibernation. Taken together with our hemodynamic assessment, these data suggest a potential downregulation of atrial chamber function during hibernation to prevent fatigue and dilation due to excessive work against an optimally filled ventricle, a response unpredicted by the Frank-Starling mechanism.
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Affiliation(s)
- N D Barrows
- Department of Biological Sciences, California State University, Long Beach, California 90840, USA
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12
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Snow JB, Gonzalez Bosc LV, Kanagy NL, Walker BR, Resta TC. Role for PKCβ in enhanced endothelin-1-induced pulmonary vasoconstrictor reactivity following intermittent hypoxia. Am J Physiol Lung Cell Mol Physiol 2011; 301:L745-54. [PMID: 21803871 DOI: 10.1152/ajplung.00020.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Intermittent hypoxia (IH) resulting from sleep apnea causes both systemic and pulmonary hypertension. Enhanced endothelin-1 (ET-1)-induced vasoconstrictor reactivity is thought to play a central role in the systemic hypertensive response to IH. However, whether IH similarly increases pulmonary vasoreactivity and the signaling mechanisms involved are unknown. The objective of the present study was to test the hypothesis that IH augments ET-1-induced pulmonary vasoconstrictor reactivity through a PKCβ-dependent signaling pathway. Responses to ET-1 were assessed in endothelium-disrupted, pressurized pulmonary arteries (∼150 μm inner diameter) from eucapnic-IH [(E-IH) 3 min cycles, 5% O(2)-5% CO(2)/air flush, 7 h/day; 4 wk] and sham (air-cycled) rats. Arteries were loaded with fura-2 AM to monitor vascular smooth muscle (VSM) intracellular Ca(2+) concentration ([Ca(2+)](i)). E-IH increased vasoconstrictor reactivity without altering Ca(2+) responses, suggestive of myofilament Ca(2+) sensitization. Consistent with our hypothesis, inhibitors of both PKCα/β (myr-PKC) and PKCβ (LY-333-531) selectively decreased vasoconstriction to ET-1 in arteries from E-IH rats and normalized responses between groups, whereas Rho kinase (fasudil) and PKCδ (rottlerin) inhibition were without effect. Although E-IH did not alter arterial PKCα/β mRNA or protein expression, E-IH increased basal PKCβI/II membrane localization and caused ET-1-induced translocation of these isoforms away from the membrane fraction. We conclude that E-IH augments pulmonary vasoconstrictor reactivity to ET-1 through a novel PKCβ-dependent mechanism that is independent of altered PKC expression. These findings provide new insights into signaling mechanisms that contribute to vasoconstriction in the hypertensive pulmonary circulation.
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Affiliation(s)
- Jessica B Snow
- Dept. of Cell Biology and Physiology, Univ. of New Mexico Health Sciences Center, MSC 08-4750, 1 Univ. of New Mexico, Albuquerque, NM 87131-0001, USA.
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13
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Zheng H, Liu J, Liu C, Lu F, Zhao Y, Jin Z, Ren H, Leng X, Jia J, Hu G, Dong S, Zhong X, Li H, Yang B, Xu C, Zhang W. Calcium-sensing receptor activating phosphorylation of PKCδ translocation on mitochondria to induce cardiomyocyte apoptosis during ischemia/reperfusion. Mol Cell Biochem 2011; 358:335-43. [DOI: 10.1007/s11010-011-0984-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 07/06/2011] [Indexed: 12/15/2022]
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14
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Brighton PJ, Rana S, Challiss RJ, Konje JC, Willets JM. Arrestins differentially regulate histamine- and oxytocin-evoked phospholipase C and mitogen-activated protein kinase signalling in myometrial cells. Br J Pharmacol 2011; 162:1603-17. [PMID: 21175586 DOI: 10.1111/j.1476-5381.2010.01173.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE The uterotonins oxytocin and histamine, mediate contractile signals through specific G protein-coupled receptors, a process which is tightly controlled during gestation to prevent preterm labour. We previously identified G protein-coupled receptor kinase (GRK)2 and GRK6 as respective cardinal negative regulators of histamine H(1) and oxytocin receptor signalling. GRK-mediated phosphorylation promotes arrestin recruitment, not only desensitizing receptors but activating an increasing number of diverse signalling pathways. Here we investigate potential roles that arrestins play in the regulation of myometrial oxytocin/histamine H(1) receptor signalling. EXPERIMENTAL APPROACH Endogenous arrestins2 and 3 were specifically depleted using RNA-interference in a human myometrial cell line and the consequences of this for G protein-coupled receptor-mediated signalling were assessed using Ca(2+) /inositol 1,4,5-trisphophate imaging and standard mitogen-activated protein kinase (MAPK) assays. KEY RESULTS Depletion of arrestin3, but not arrestin2 enhanced and prolonged H(1) receptor-stimulated Ca(2+) responses, whilst depletion of either arrestin increased oxytocin receptor responses. Arrestin3 depletion decreased H(1) receptor desensitization, whilst removal of either arrestin isoform was equally effective in preventing oxytocin receptor desensitization. Following arrestin3 depletion oxytocin-induced phospho-extracellular signal-regulated kinase1/2 signals were diminished and histamine-stimulated signals virtually absent, whereas depletion of arrestin2 augmented extracellular signal-regulated kinase1/2 responses to each agonist. Conversely, depletion of arrestin3 enhanced p38 signals to each agonist, whilst arrestin2 suppression increased oxytocin-, but not histamine-induced p38 MAPK responses. CONCLUSIONS AND IMPLICATIONS Arrestin proteins are key regulators of H(1) and oxytocin receptor desensitization, and play integral roles mediating uterotonin-stimulated MAPK-signalling. These data provide insights into the in situ regulation of these receptor subtypes and may inform pathophysiological functioning in preterm labour.
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Affiliation(s)
- Paul J Brighton
- Endocannabinoid Research Group, Reproductive Sciences Section, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester Royal Infirmary, Leicester, UK
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Rainbow RD, Parker AM, Davies NW. Protein kinase C-independent inhibition of arterial smooth muscle K(+) channels by a diacylglycerol analogue. Br J Pharmacol 2011; 163:845-56. [PMID: 21323899 PMCID: PMC3111686 DOI: 10.1111/j.1476-5381.2011.01268.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Analogues of the endogenous diacylglycerols have been used extensively as pharmacological activators of protein kinase C (PKC). Several reports show that some of these compounds have additional effects that are independent of PKC activation, including direct block of K(+) and Ca(2+) channels. We investigated whether dioctanoyl-sn-glycerol (DiC8), a commonly used diacylglycerol analogue, blocks K(+) currents of rat mesenteric arterial smooth muscle in a PKC-independent manner. EXPERIMENTAL APPROACH Conventional whole-cell and inside-out patch clamp was used to measure the inhibition of K(+) currents of rat isolated mesenteric smooth muscle cells by DiC8 in the absence and presence of PKC inhibitor peptide. KEY RESULTS Mesenteric artery smooth muscle K(v) currents inactivated very slowly with a time constant of about 2 s following pulses from -65 to +40 mV. Application of 1 µM DiC8 produced an approximate 40-fold increase in the apparent rate of inactivation. Pretreatment of the cells with PKC inhibitor peptide had a minimal effect on the action of DiC8, and substantial inactivation still occurred, indicating that this effect was mainly independent of PKC. We also found that DiC8 blocked BK and K(ATP) currents, and again a significant proportion of these blocks occurred independently of PKC activation. CONCLUSIONS AND IMPLICATIONS These results show that DiC8 has a direct effect on arterial smooth muscle K(+) channels, and this precludes its use as a PKC activator when investigating PKC-mediated effects on vascular K(+) channels.
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Affiliation(s)
- RD Rainbow
- Department of Cardiovascular Sciences, University of LeicesterLeicester, UK
| | - AM Parker
- Department of Cell Physiology and Pharmacology, University of LeicesterLeicester, UK
| | - NW Davies
- Department of Cell Physiology and Pharmacology, University of LeicesterLeicester, UK
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Nelson CP, Challiss RAJ. The use of translocating fluorescent biosensors for real-time monitoring of GPCR-mediated signaling events. Methods Mol Biol 2011; 746:329-343. [PMID: 21607866 DOI: 10.1007/978-1-61779-126-0_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The ability to visualize the subcellular localization of proteins by labeling them with fluorescent proteins is a powerful tool in cell biology. In the G protein-coupled receptor signaling field, this technique has been utilized to examine the various aspects of receptor behavior, including activation, internalization and recycling, as well as alterations in the cellular levels of a variety of second messengers and signaling intermediates. Attaching variants of green fluorescent protein on to protein modules, which possess high affinity and selectivity for specific signaling molecules has allowed the visualization of key signaling pathway intermediates in real time, in living cells. This chapter outlines a protocol for the expression and visualization (by confocal microscopy) of such fluorescent "biosensors" and provides guidance on the analysis and interpretation of data obtained from such experiments.
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Affiliation(s)
- Carl P Nelson
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK
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Song J, Eyster KM, Kost CK, Kjellsen B, Martin DS. Involvement of protein kinase C-CPI-17 in androgen modulation of angiotensin II-renal vasoconstriction. Cardiovasc Res 2009; 85:614-21. [PMID: 19797427 DOI: 10.1093/cvr/cvp326] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
AIMS Previous studies suggested that androgens augmented renal vascular responses to angiotensin II (Ang II). The protein kinase C (PKC)-CPI-17 pathway is involved in vascular constriction. We tested the hypothesis that this pathway may contribute to androgenic amplification of Ang II-renal vasoconstriction in the New Zealand genetically hypertensive (NZGH) rat. METHODS AND RESULTS NZGH underwent sham operation, castration, or castration with testosterone replacement at 5 weeks of age. When the rats were 16-17 weeks of age, mean arterial pressure (MAP) and renal vascular resistance (RVR) responses to intravenous Ang II infusion (20, 40, and 80 ng/kg/min) were recorded before and after treatment with a PKC inhibitor, chelerythrine. mRNA expression of PKC isoforms and CPI-17 protein expression were analysed in renal cortex. MAP and RVR responses to Ang II were enhanced in androgen-replete NZGH. The Ang II-induced increase in RVR was significantly lower in castrated NZGH (ranged from 100 +/- 8% to 161 +/- 9% of baseline) than in sham-operated NZGH (ranged between 123 +/- 3% and 237 +/- 19% of baseline). Testosterone treatment restored RVR responses to Ang II in castrated rats. Chelerythrine treatment markedly reduced the MAP and RVR responses to Ang II in each group and attenuated the differential MAP and RVR responses to Ang II amongst the three groups. PKCdelta and PKCepsilon mRNA levels were significantly reduced by castration and increased by testosterone treatment. In contrast, no significant differences in protein expression were detected for these PKC isoforms. Castration decreased while testosterone treatment increased CPI-17 and phospho-CPI-17 expression. CONCLUSION Collectively, these results suggest that androgens modulate renal vascular responses to Ang II in part via an effect on the PKC-CPI-17 signalling pathway.
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Affiliation(s)
- Jin Song
- Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, NY 11040, USA
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18
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Morris GE, Nelson CP, Standen NB, Challiss RAJ, Willets JM. Endothelin signalling in arterial smooth muscle is tightly regulated by G protein-coupled receptor kinase 2. Cardiovasc Res 2009; 85:424-33. [PMID: 19748906 PMCID: PMC2802200 DOI: 10.1093/cvr/cvp310] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
AIMS Prolonged endothelin (ET) receptor signalling causes vasoconstriction and can lead to hypertension, vascular smooth muscle hypertrophy, and hyperplasia. Usually, G protein-coupled receptor signalling is negatively regulated by G protein-coupled receptor kinases (GRKs), preventing prolonged or inappropriate signalling. This study investigated whether GRKs regulate ET receptor contractile signalling in adult Wistar rat mesenteric arterial smooth muscle cells (MSMCs). METHODS AND RESULTS ET-1-stimulated phospholipase C (PLC) activity and changes in [Ca2+]i were assessed using confocal microscopy in rat MSMCs transfected with the pleckstrin-homology domain of PLCdelta1 (eGFP-PH) and loaded with Fura-Red. ET-1 applications (30 s) stimulated transient concentration-dependent eGFP-PH translocations from plasma membrane to cytoplasm and graded [Ca2+]i increases. ET-1-mediated PLC signalling was blocked by the type A endothelin receptor (ET(A)R) antagonist, BQ123. To characterize ET(A)R desensitization, cells were stimulated with a maximally effective concentration of ET-1 (50 nM, 30 s) followed by a variable washout period and a second identical application of ET-1. This brief exposure to ET-1 markedly decreased ET(A)R responsiveness to re-challenge, and reversal was incomplete even after increasing the time period between agonist challenges to 60 min. To assess GRK involvement in ET(A)R desensitization, MSMCs were co-transfected with eGFP-PH and catalytically inactive (D110A,K220R)GRK2, (D110A,K220R)GRK3, (K215R)GRK5, or (K215R)GRK6 constructs. (D110A,K220R)GRK2 expression significantly attenuated ET(A)R desensitization, whereas other constructs were ineffective. Small interfering RNA-targeted GRK2 depletion equally attenuated ET(A)R desensitization. Finally, immunocyotchemical data showed that ET(A)R activation recruited endogenous GRK2 from cytoplasm to membrane. CONCLUSION These studies identify GRK2 as a key regulator of ET(A)R responsiveness in resistance arteries, highlighting the potential importance of this GRK isoenzyme in regulating vasoconstrictor signalling pathways implicated in vascular disease.
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Affiliation(s)
- Gavin E Morris
- Reproductive Sciences Section, Department of Cancer Studies and Molecular Medicine, Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK
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Rainbow RD, Norman RI, Everitt DE, Brignell JL, Davies NW, Standen NB. Endothelin-I and angiotensin II inhibit arterial voltage-gated K+ channels through different protein kinase C isoenzymes. Cardiovasc Res 2009; 83:493-500. [PMID: 19429666 DOI: 10.1093/cvr/cvp143] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Voltage-gated K+ (Kv) channels of arterial smooth muscle (ASM) modulate arterial tone and are inhibited by vasoconstrictors through protein kinase C (PKC). We aimed to determine whether endothelin-1 (ET-1) and angiotensin II (AngII), which cause similar inhibition of Kv, use the same signalling pathway and PKC isoenzyme to exert their effects on Kv and to compare the involvement of PKC isoenzymes in contractile responses to these agents. METHODS AND RESULTS Kv currents recorded using the patch clamp technique with freshly isolated rat mesenteric ASM cells were inhibited by ET-1 or AngII. Inclusion of a PKCepsilon inhibitor peptide in the intracellular solution substantially reduced inhibition by AngII, but did not affect that by ET-1. Kv inhibition by ET-1 was reduced by the conventional PKC inhibitor Gö 6976 but not by the PKCbeta inhibitor LY333531. Selective peptide inhibitors of PKCalpha and PKCepsilon were linked to a Tat carrier peptide to make them membrane permeable and used to show that inhibition of PKCalpha prevented ET-1 inhibition of Kv current, but did not affect that by AngII. In contrast, inhibition of PKCepsilon prevented Kv inhibition by AngII but not by ET-1. The Tat-linked inhibitor peptides were also used to investigate the involvement of PKCalpha and PKCepsilon in the contractile responses of mesenteric arterial rings, showing that ET-1 contractions were substantially reduced by inhibition of PKCalpha, but unaffected by inhibition of PKCepsilon. AngII contractions were unaffected by inhibition of PKCalpha but substantially reduced by inhibition of PKCepsilon. CONCLUSION ET-1 inhibits Kv channels of mesenteric ASM through activation of PKCalpha, while AngII does so through PKCepsilon. This implies that ET-1 and AngII target Kv channels of ASM through different pathways of PKC-interacting proteins, so each vasoconstrictor enables its distinct PKC isoenzyme to interact functionally with the Kv channel.
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Affiliation(s)
- Richard D Rainbow
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
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McCarron JG, Olson ML, Currie S, Wright AJ, Anderson KI, Girkin JM. Elevations of intracellular calcium reflect normal voltage-dependent behavior, and not constitutive activity, of voltage-dependent calcium channels in gastrointestinal and vascular smooth muscle. ACTA ACUST UNITED AC 2009; 133:439-57. [PMID: 19289573 PMCID: PMC2699105 DOI: 10.1085/jgp.200810189] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In smooth muscle, the gating of dihydropyridine-sensitive Ca2+ channels may either be stochastic and voltage dependent or coordinated among channels and constitutively active. Each form of gating has been proposed to be largely responsible for Ca2+ influx and determining the bulk average cytoplasmic Ca2+ concentration. Here, the contribution of voltage-dependent and constitutively active channel behavior to Ca2+ signaling has been studied in voltage-clamped single vascular and gastrointestinal smooth muscle cells using wide-field epifluorescence with near simultaneous total internal reflection fluorescence microscopy. Depolarization (−70 to +10 mV) activated a dihydropyridine-sensitive voltage-dependent Ca2+ current (ICa) and evoked a rise in [Ca2+] in each of the subplasma membrane space and bulk cytoplasm. In various regions of the bulk cytoplasm the [Ca2+] increase ([Ca2+]c) was approximately uniform, whereas that of the subplasma membrane space ([Ca2+]PM) had a wide range of amplitudes and time courses. The variations that occurred in the subplasma membrane space presumably reflected an uneven distribution of active Ca2+ channels (clusters) across the sarcolemma, and their activation appeared consistent with normal voltage-dependent behavior. Indeed, in the present study, dihydropyridine-sensitive Ca2+ channels were not normally constitutively active. The repetitive localized [Ca2+]PM rises (“persistent Ca2+ sparklets”) that characterize constitutively active channels were observed rarely (2 of 306 cells). Neither did dihydropyridine-sensitive constitutively active Ca2+ channels regulate the bulk average [Ca2+]c. A dihydropyridine blocker of Ca2+ channels, nimodipine, which blocked ICa and accompanying [Ca2+]c rise, reduced neither the resting bulk average [Ca2+]c (at −70 mV) nor the rise in [Ca2+]c, which accompanied an increased electrochemical driving force on the ion by hyperpolarization (−130 mV). Activation of protein kinase C with indolactam-V did not induce constitutive channel activity. Thus, although voltage-dependent Ca2+ channels appear clustered in certain regions of the plasma membrane, constitutive activity is unlikely to play a major role in [Ca2+]c regulation. The stochastic, voltage-dependent activity of the channel provides the major mechanism to generate rises in [Ca2+].
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, SUPA, University of Strathclyde, Glasgow G4 0NR, Scotland, UK.
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