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Parthasarathy A, Anishkin A, Xie Y, Drachuk K, Nishijma Y, Fang J, Koukouritaki SB, Wilcox DA, Zhang DX. Phosphorylation of distal C-terminal residues promotes TRPV4 channel activation in response to arachidonic acid. J Biol Chem 2025; 301:108260. [PMID: 39909371 PMCID: PMC11903807 DOI: 10.1016/j.jbc.2025.108260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2024] [Revised: 01/22/2025] [Accepted: 01/27/2025] [Indexed: 02/07/2025] Open
Abstract
Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+-permeable channel activated by diverse physical and chemical stimuli, including mechanical stress and endogenous lipid arachidonic acid (AA) and its metabolites. Phosphorylation of TRPV4 by protein kinase A (PKA) and protein kinase C (PKC) is a predominant mechanism for channel regulation, especially in the cytoplasmic domains due to their importance in protein assembly, and channelopathies. However, studies corresponding to phosphorylation sites for these kinases remain incomplete. We investigated the role of Ser-823 residue as a potential phosphorylation site in regulating TRPV4 activity and chemical agonist-induced channel activation. Using mass spectrometry, we identified a new phosphorylation site Ser-823 residue and confirmed the previously known phosphorylation site Ser-824 in the C-terminal tail. The low level of phosphorylation at Ser-823 was stimulated by PKC and to a lesser extent by PKA in human coronary artery endothelial cells (HCAECs) and human embryonic kidney 293 (HEK 293) cells. AA-induced TRPV4 activation was enhanced in the phosphomimetic S823E but was blunted in the S823A/S824A mutants, whereas the channel activation by the synthetic agonist GSK1016790A was unaffected. Further, TRPV4 activation by AA but not GSK1016790A was blunted or abolished by PKA inhibitor alone or in combination with PKC inhibitor, respectively. Using computational modeling, we refined a previously proposed structural model for TRPV4 regulation by Ser-823 and Ser-824 phosphorylation. Together, these results provide insight into how stimuli-specific TRPV4 activation is regulated by the phosphorylation of discrete residues (e.g., Ser-823 and Ser-824) in the C-terminal domains of the TRPV4 channel.
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Affiliation(s)
- Aravind Parthasarathy
- Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, Maryland, USA
| | - Yangjing Xie
- Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Kostiantyn Drachuk
- Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Yoshinori Nishijma
- Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Juan Fang
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Children's Research Institute, Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - Sevasti B Koukouritaki
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Children's Research Institute, Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - David A Wilcox
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Children's Research Institute, Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - David X Zhang
- Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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2
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Hernandez-Hernandez G, O'Dwyer SC, Yang PC, Matsumoto C, Tieu M, Fong Z, Lewis TJ, Santana LF, Clancy CE. A computational model predicts sex-specific responses to calcium channel blockers in mammalian mesenteric vascular smooth muscle. eLife 2024; 12:RP90604. [PMID: 38335126 PMCID: PMC10942543 DOI: 10.7554/elife.90604] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2024] Open
Abstract
The function of the smooth muscle cells lining the walls of mammalian systemic arteries and arterioles is to regulate the diameter of the vessels to control blood flow and blood pressure. Here, we describe an in silico model, which we call the 'Hernandez-Hernandez model', of electrical and Ca2+ signaling in arterial myocytes based on new experimental data indicating sex-specific differences in male and female arterial myocytes from murine resistance arteries. The model suggests the fundamental ionic mechanisms underlying membrane potential and intracellular Ca2+ signaling during the development of myogenic tone in arterial blood vessels. Although experimental data suggest that KV1.5 channel currents have similar amplitudes, kinetics, and voltage dependencies in male and female myocytes, simulations suggest that the KV1.5 current is the dominant current regulating membrane potential in male myocytes. In female cells, which have larger KV2.1 channel expression and longer time constants for activation than male myocytes, predictions from simulated female myocytes suggest that KV2.1 plays a primary role in the control of membrane potential. Over the physiological range of membrane potentials, the gating of a small number of voltage-gated K+ channels and L-type Ca2+ channels are predicted to drive sex-specific differences in intracellular Ca2+ and excitability. We also show that in an idealized computational model of a vessel, female arterial smooth muscle exhibits heightened sensitivity to commonly used Ca2+ channel blockers compared to male. In summary, we present a new model framework to investigate the potential sex-specific impact of antihypertensive drugs.
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Affiliation(s)
| | - Samantha C O'Dwyer
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Pei-Chi Yang
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Collin Matsumoto
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Mindy Tieu
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Zhihui Fong
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Timothy J Lewis
- Department of Mathematics, University of California, DavisDavisUnited States
| | - L Fernando Santana
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
| | - Colleen E Clancy
- Department of Physiology & Membrane Biology, University of California, DavisDavisUnited States
- Center for Precision Medicine and Data Sciences, University of California, DavisDavisUnited States
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3
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Hernandez-Hernandez G, O’Dwyer SC, Matsumoto C, Tieu M, Fong Z, Yang PC, Lewis TJ, Fernando Santana L, Clancy CE. A computational model predicts sex-specific responses to calcium channel blockers in mammalian mesenteric vascular smooth muscle. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.24.546394. [PMID: 37425682 PMCID: PMC10327109 DOI: 10.1101/2023.06.24.546394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The function of the smooth muscle cells lining the walls of mammalian systemic arteries and arterioles is to regulate the diameter of the vessels to control blood flow and blood pressure. Here, we describe an in-silico model, which we call the "Hernandez-Hernandez model", of electrical and C a 2+ signaling in arterial myocytes based on new experimental data indicating sex-specific differences in male and female arterial myocytes from murine resistance arteries. The model suggests the fundamental ionic mechanisms underlying membrane potential and intracellular C a 2+ signaling during the development of myogenic tone in arterial blood vessels. Although experimental data suggest that KV1.5 channel currents have similar amplitudes, kinetics, and voltage dependencies in male and female myocytes, simulations suggest that the KV1.5 current is the dominant current regulating membrane potential in male myocytes. In female cells, which have larger KV2.1 channel expression and longer time constants for activation than male myocytes, predictions from simulated female myocytes suggest that KV2.1 plays a primary role in the control of membrane potential. Over the physiological range of membrane potentials, the gating of a small number of voltage-gated K+ channels and L-type C a 2+ channels are predicted to drive sex-specific differences in intracellular C a 2+ and excitability. We also show that in an idealized computational model of a vessel, female arterial smooth muscle exhibits heightened sensitivity to commonly used C a 2+ channel blockers compared to male. In summary, we present a new model framework to investigate the potential sex-specific impact of anti-hypertensive drugs.
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Affiliation(s)
- Gonzalo Hernandez-Hernandez
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Samantha C. O’Dwyer
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Collin Matsumoto
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Mindy Tieu
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Zhihui Fong
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Pei-Chi Yang
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
- Department of Mathematics, University of California, Davis, California, 95616
| | - Timothy J. Lewis
- Department of Mathematics, University of California, Davis, California, 95616
| | | | - Colleen E. Clancy
- Department of Physiology & Membrane Biology, Center for Precision Medicine and Data Science, University of California School of Medicine, Davis, California, 95616
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4
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Chulkov EG, Palygin O, Yahya NA, Park SK, Marchant JS. Electrophysiological characterization of a schistosome transient receptor potential channel activated by praziquantel. Int J Parasitol 2023; 53:415-425. [PMID: 36610556 PMCID: PMC10258134 DOI: 10.1016/j.ijpara.2022.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 11/12/2022] [Accepted: 11/16/2022] [Indexed: 01/06/2023]
Abstract
Ion channels have proved to be productive targets for anthelmintic chemotherapy. One example is the recent discovery of a parasitic flatworm ion channel targeted by praziquantel (PZQ), the main clinical therapy used for treatment of schistosomiasis. The ion channel activated by PZQ - a transient receptor potential ion channel of the melastatin subfamily, named TRPMPZQ - is a Ca2+-permeable ion channel expressed in all parasitic flatworms that are PZQ-sensitive. However, little is currently known about the electrophysiological properties of this target that mediates the deleterious action of PZQ on many trematodes and cestodes. Here, we provide a detailed biophysical characterization of the properties of Schistosoma mansoni TRPMPZQ channel (Sm.TRPMPZQ) in response to PZQ. Single channel electrophysiological analysis demonstrated that Sm.TRPMPZQ when activated by PZQ is a non-selective, large conductance, voltage-insensitive cation channel that displays distinct properties from human TRPM paralogs. Sm.TRPMPZQ is Ca2+-permeable but does not require Ca2+ for channel gating in response to PZQ. TRPMPZQ from Schistosoma japonicum (Sj.TRPMPZQ) and Schistosoma haematobium (Sh.TRPMPZQ) displayed similar characteristics. Profiling Sm.TRPMPZQ responsiveness to PZQ has established a biophysical signature for this channel that will aid future investigation of endogenous TRPMPZQ activity, as well as analyses of endogenous and exogenous regulators of this novel, druggable antiparasitic target.
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Affiliation(s)
- Evgeny G Chulkov
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Oleg Palygin
- Division of Nephrology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Nawal A Yahya
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA; Department of Pharmacology, University of Minnesota Medical School, 312 Church St. SE, Minneapolis, MN 55455, USA
| | - Sang-Kyu Park
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Jonathan S Marchant
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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5
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Klug NR, Sancho M, Gonzales AL, Heppner TJ, O’Brien RIC, Hill-Eubanks D, Nelson MT. Intraluminal pressure elevates intracellular calcium and contracts CNS pericytes: Role of voltage-dependent calcium channels. Proc Natl Acad Sci U S A 2023; 120:e2216421120. [PMID: 36802432 PMCID: PMC9992766 DOI: 10.1073/pnas.2216421120] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 01/24/2023] [Indexed: 02/23/2023] Open
Abstract
Arteriolar smooth muscle cells (SMCs) and capillary pericytes dynamically regulate blood flow in the central nervous system in the face of fluctuating perfusion pressures. Pressure-induced depolarization and Ca2+ elevation provide a mechanism for regulation of SMC contraction, but whether pericytes participate in pressure-induced changes in blood flow remains unknown. Here, utilizing a pressurized whole-retina preparation, we found that increases in intraluminal pressure in the physiological range induce contraction of both dynamically contractile pericytes in the arteriole-proximate transition zone and distal pericytes of the capillary bed. We found that the contractile response to pressure elevation was slower in distal pericytes than in transition zone pericytes and arteriolar SMCs. Pressure-evoked elevation of cytosolic Ca2+ and contractile responses in SMCs were dependent on voltage-dependent Ca2+ channel (VDCC) activity. In contrast, Ca2+ elevation and contractile responses were partially dependent on VDCC activity in transition zone pericytes and independent of VDCC activity in distal pericytes. In both transition zone and distal pericytes, membrane potential at low inlet pressure (20 mmHg) was approximately -40 mV and was depolarized to approximately -30 mV by an increase in pressure to 80 mmHg. The magnitude of whole-cell VDCC currents in freshly isolated pericytes was approximately half that measured in isolated SMCs. Collectively, these results indicate a loss of VDCC involvement in pressure-induced constriction along the arteriole-capillary continuum. They further suggest that alternative mechanisms and kinetics of Ca2+ elevation, contractility, and blood flow regulation exist in central nervous system capillary networks, distinguishing them from neighboring arterioles.
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Affiliation(s)
- Nicholas R. Klug
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
| | - Maria Sancho
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
| | - Albert L. Gonzales
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, NV89557
| | - Thomas J. Heppner
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
| | | | - David Hill-Eubanks
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
| | - Mark T. Nelson
- Department of Pharmacology, Larner College of Medicine, University of Vermont, Burlington, VT05405
- Division of Cardiovascular Sciences, University of Manchester, ManchesterM13 9PL, UK
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6
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Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
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Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
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7
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Ishida Y, Kitayama K, Hanada K, Shibutani S, Nishizaki K, Kinjo T, Endo T, Suzuki A, Tateyama S, Nishizaki F, Sukekawa T, Tanaka M, Osanai T, Okumura K, Tomita H. Diltiazem Inhibits Coronary Spasm via Inhibition of Cav1.2Phosphorylation and Protein Kinase C Activation in a Mouse Model of Coronary Spastic Angina. Int Heart J 2021; 62:910-918. [PMID: 34276002 DOI: 10.1536/ihj.20-366] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Calcium antagonists are used for coronary spastic angina (CSA) treatment. We previously identified a phospholipase C (PLC) -δ1 gene variant that results in enhanced PLC activity in patients with CSA and developed a CSA animal model by generating vascular smooth muscle cell-specific human variant PLC-δ1 overexpression (PLC-TG) mice. In this study, we investigated the molecular mechanism of CSA using the PLC-TG mice and the inhibitory effect of a calcium antagonist, diltiazem hydrochloride (DL).We treated the PLC-TG and wild-type (WT) mice with oral DL or trichlormethiazide (TM) (control) for 2 weeks. Ergometrine injection-induced coronary spasm was observed on the electrocardiogram in all 5 PLC-TG mice treated with TM, but only in 1 of 5 PLC-TG mice treated with DL. Voltage-dependent calcium channel (Cav1.2) phosphorylation and protein kinase C (PKC) activity were enhanced in the aortas of PLC-TG mice treated with TM. DL treatment significantly inhibited Cav1.2 phosphorylation and PKC activity. Although total Cav1.2 expression was similar between WT and PLC-TG mice treated with TM, DL treatment significantly increased its expression in PLC-TG mice. Furthermore, its expression remained high after DL discontinuation. DL and PKC inhibitor suppressed intracellular calcium response to acetylcholine in cultured rat aortic smooth muscle cells transfected with variant PLC-δ1.These results indicate that enhanced PLC activity causes coronary spasm, presumably via enhanced Cav1.2 phosphorylation and PKC activity, both of which were inhibited by DL. Enhanced total Cav1.2 expression after DL discontinuation and high PKC activity may be an important mechanism underlying the calcium antagonist withdrawal syndrome.
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Affiliation(s)
- Yuji Ishida
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Kazutaka Kitayama
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Kenji Hanada
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Shuji Shibutani
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Kimitaka Nishizaki
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Takahiko Kinjo
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Tomohide Endo
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Akiko Suzuki
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Shunta Tateyama
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Fumie Nishizaki
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Takanori Sukekawa
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Makoto Tanaka
- Department of Cardiology, Hirosaki University Graduate School of Medicine
| | - Tomohiro Osanai
- Department of Nursing Science, Hirosaki University Graduate School of Health Sciences
| | - Ken Okumura
- Division of Cardiology, Saiseikai Kumamoto Hospital
| | - Hirofumi Tomita
- Department of Cardiology, Hirosaki University Graduate School of Medicine
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Kim K, Hong KS. Transient receptor potential channel-dependent myogenic responsiveness in small-sized resistance arteries. J Exerc Rehabil 2021; 17:4-10. [PMID: 33728282 PMCID: PMC7939990 DOI: 10.12965/jer.2040836.418] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 12/19/2020] [Indexed: 11/22/2022] Open
Abstract
It is well documented that the inherent ability of small arteries and arterioles to regulate intraluminal diameter in response to alterations in intravascular pressure determines peripheral vascular resistance and blood flow (termed myogenic response or pressure-induced vasoconstriction/dilation). This autoregulatory property of resistance arteries is primarily originated from mechanosensitive vascular smooth muscle cells (VSMCs). There are diverse biological apparatuses in the plasma membrane of VSMCs that sense mechanical stimuli and generate intracellular signals for the contractility of VSMCs. Although the roles of transient receptor potential (TRP) channels in pressure-induced vasoconstriction are not fully understood to date, TRP channels that are directly activated by mechanical stimuli (e.g., stretch of VSMCs) or indirectly evoked by intracellular molecules (e.g., inositol trisphosphate) provide the major sources of Ca2+ (e.g., Ca2+ influx or release from the sarcoplasmic reticulum) and in turn, evoke vascular reactivity. This review sought to summarize mounting evidence over several decades that the activation of TRP canonical, TRP melastatin, TRP vanilloid, and TRP polycystin channels contributes to myogenic vasoconstriction.
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Affiliation(s)
- Kijeong Kim
- School of Exercise & Sport Science, College of Natural Sciences, University of Ulsan, Ulsan, Korea
| | - Kwang-Seok Hong
- Department of Physical Education, College of Education, Chung-Ang University, Seoul, Korea
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9
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Aerobic exercise-induced inhibition of PKCα/CaV1.2 pathway enhances the vasodilation of mesenteric arteries in hypertension. Arch Biochem Biophys 2019; 678:108191. [DOI: 10.1016/j.abb.2019.108191] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/09/2019] [Accepted: 11/12/2019] [Indexed: 01/01/2023]
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10
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Ito DW, Hannigan KI, Ghosh D, Xu B, Del Villar SG, Xiang YK, Dickson EJ, Navedo MF, Dixon RE. β-adrenergic-mediated dynamic augmentation of sarcolemmal Ca V 1.2 clustering and co-operativity in ventricular myocytes. J Physiol 2019; 597:2139-2162. [PMID: 30714156 PMCID: PMC6462464 DOI: 10.1113/jp277283] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 02/03/2019] [Indexed: 01/25/2023] Open
Abstract
Key points Prevailing dogma holds that activation of the β‐adrenergic receptor/cAMP/protein kinase A signalling pathway leads to enhanced L‐type CaV1.2 channel activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. However, the full mechanistic and molecular details underlying this phenomenon are incompletely understood. CaV1.2 channel clusters decorate T‐tubule sarcolemmas of ventricular myocytes. Within clusters, nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by physical interactions between adjacent channel C‐terminal tails. We report that stimulation of cardiomyocytes with isoproterenol, evokes dynamic, protein kinase A‐dependent augmentation of CaV1.2 channel abundance along cardiomyocyte T‐tubules, resulting in the appearance of channel ‘super‐clusters’, and enhanced channel co‐operativity that amplifies Ca2+ influx. On the basis of these data, we suggest a new model in which a sub‐sarcolemmal pool of pre‐synthesized CaV1.2 channels resides in cardiomyocytes and can be mobilized to the membrane in times of high haemodynamic or metabolic demand, to tune excitation–contraction coupling.
Abstract Voltage‐dependent L‐type CaV1.2 channels play an indispensable role in cardiac excitation–contraction coupling. Activation of the β‐adrenergic receptor (βAR)/cAMP/protein kinase A (PKA) signalling pathway leads to enhanced CaV1.2 activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. CaV1.2 channels exhibit a clustered distribution along the T‐tubule sarcolemma of ventricular myocytes where nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by dynamic, physical, allosteric interactions between adjacent channel C‐terminal tails. This amplifies Ca2+ influx and augments myocyte Ca2+ transient and contraction amplitudes. We investigated whether βAR signalling could alter CaV1.2 channel clustering to facilitate co‐operative channel interactions and elevate Ca2+ influx in ventricular myocytes. Bimolecular fluorescence complementation experiments reveal that the βAR agonist, isoproterenol (ISO), promotes enhanced CaV1.2–CaV1.2 physical interactions. Super‐resolution nanoscopy and dynamic channel tracking indicate that these interactions are expedited by enhanced spatial proximity between channels, resulting in the appearance of CaV1.2 ‘super‐clusters’ along the z‐lines of ISO‐stimulated cardiomyocytes. The mechanism that leads to super‐cluster formation involves rapid, dynamic augmentation of sarcolemmal CaV1.2 channel abundance after ISO application. Optical and electrophysiological single channel recordings confirm that these newly inserted channels are functional and contribute to overt co‐operative gating behaviour of CaV1.2 channels in ISO stimulated myocytes. The results of the present study reveal a new facet of βAR‐mediated regulation of CaV1.2 channels in the heart and support the novel concept that a pre‐synthesized pool of sub‐sarcolemmal CaV1.2 channel‐containing vesicles/endosomes resides in cardiomyocytes and can be mobilized to the sarcolemma to tune excitation–contraction coupling to meet metabolic and/or haemodynamic demands. Prevailing dogma holds that activation of the β‐adrenergic receptor/cAMP/protein kinase A signalling pathway leads to enhanced L‐type CaV1.2 channel activity, resulting in increased Ca2+ influx into ventricular myocytes and a positive inotropic response. However, the full mechanistic and molecular details underlying this phenomenon are incompletely understood. CaV1.2 channel clusters decorate T‐tubule sarcolemmas of ventricular myocytes. Within clusters, nanometer proximity between channels permits Ca2+‐dependent co‐operative gating behaviour mediated by physical interactions between adjacent channel C‐terminal tails. We report that stimulation of cardiomyocytes with isoproterenol, evokes dynamic, protein kinase A‐dependent augmentation of CaV1.2 channel abundance along cardiomyocyte T‐tubules, resulting in the appearance of channel ‘super‐clusters’, and enhanced channel co‐operativity that amplifies Ca2+ influx. On the basis of these data, we suggest a new model in which a sub‐sarcolemmal pool of pre‐synthesized CaV1.2 channels resides in cardiomyocytes and can be mobilized to the membrane in times of high haemodynamic or metabolic demand, to tune excitation–contraction coupling.
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Affiliation(s)
- Danica W Ito
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Karen I Hannigan
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Debapriya Ghosh
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Bing Xu
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Silvia G Del Villar
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Yang K Xiang
- Department of Pharmacology, University of California Davis, Davis, CA, USA.,VA Northern California Health Care System, Mather, CA, USA
| | - Eamonn J Dickson
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
| | - Manuel F Navedo
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Rose E Dixon
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
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11
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Hashad AM, Sancho M, Brett SE, Welsh DG. Reactive Oxygen Species Mediate the Suppression of Arterial Smooth Muscle T-type Ca 2+ Channels by Angiotensin II. Sci Rep 2018; 8:3445. [PMID: 29472601 PMCID: PMC5823855 DOI: 10.1038/s41598-018-21899-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 02/13/2018] [Indexed: 02/07/2023] Open
Abstract
Vascular T-type Ca2+ channels (CaV3.1 and CaV3.2) play a key role in arterial tone development. This study investigated whether this conductance is a regulatory target of angiotensin II (Ang II), a vasoactive peptide that circulates and which is locally produced within the arterial wall. Patch clamp electrophysiology performed on rat cerebral arterial smooth muscle cells reveals that Ang II (100 nM) inhibited T-type currents through AT1 receptor activation. Blocking protein kinase C failed to eliminate channel suppression, a finding consistent with unique signaling proteins enabling this response. In this regard, inhibiting NADPH oxidase (Nox) with apocynin or ML171 (Nox1 selective) abolished channel suppression highlighting a role for reactive oxygen species (ROS). In the presence of Ni2+ (50 µM), Ang II failed to modulate the residual T-type current, an observation consistent with this peptide targeting CaV3.2. Selective channel suppression by Ang II impaired the ability of CaV3.2 to alter spontaneous transient outward currents or vessel diameter. Proximity ligation assay confirmed Nox1 colocalization with CaV3.2. In closing, Ang II targets CaV3.2 channels via a signaling pathway involving Nox1 and the generation of ROS. This unique regulatory mechanism alters BKCa mediated feedback giving rise to a “constrictive” phenotype often observed with cerebrovascular disease.
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Affiliation(s)
- Ahmed M Hashad
- Deptartment of Physiology & Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Alberta, Canada
| | - Maria Sancho
- Deptartment Physiology & Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Suzanne E Brett
- Deptartment Physiology & Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Donald G Welsh
- Deptartment of Physiology & Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Alberta, Canada. .,Deptartment Physiology & Pharmacology, University of Western Ontario, London, Ontario, Canada.
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12
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Porras-González C, Ordóñez A, Castellano A, Ureña J. Regulation of RhoA/ROCK and sustained arterial contraction by low cytosolic Ca 2+ levels during prolonged depolarization of arterial smooth muscle. Vascul Pharmacol 2017; 93-95:33-41. [PMID: 28526517 DOI: 10.1016/j.vph.2017.05.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 05/15/2017] [Accepted: 05/16/2017] [Indexed: 11/19/2022]
Abstract
The role of L-type Ca2+ channels (LTCCs) and RhoA/Rho kinase (ROCK) on depolarization-induced sustained arterial contraction lasting several minutes is already known. However, in vivo, vascular smooth muscle cells can be depolarized for longer periods, inducing substantial inactivation of LTCCs and markedly reducing Ca2+ influx into the myocytes. We have examined, in femoral arterial rings, the role of LTCCs and RhoA/ROCK during long-lasting depolarization. Our results reveal a new vasoreactive response after 20-30min of depolarization in 2.5mM external Ca2+ that has not been identified previously with shorter stimuli. Prolonged depolarization-induced arterial contraction was permanently abolished when arterial rings were treated with 100nM external Ca2+ or 20nM nifedipine. However, when Ca2+ influx was restricted, applying ~7μM external Ca2+ solution or 3nM nifedipine, vasorelaxation was transient, and isometric force slowly increased after 30min and maintained its level until the end of the stimulus. Under these conditions, arterial contraction showed the same temporal course of RhoA activity and was sensitive to fasudil, nifedipine and cyclopiazonic acid. Ca2+-response curve in β-escin permeabilized arteries was also sensitive to ROCK inhibitors. Thus, although long-lasting depolarization inactivates LTCCs, the reduced Ca2+ entry can induce a detectable arterial contraction via RhoA/ROCK activation.
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Affiliation(s)
- Cristina Porras-González
- Instituto de Biomedicina de Sevilla, IBiS, Hospital Universitario Virgen del Rocío, CSIC, Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain
| | - Antonio Ordóñez
- Instituto de Biomedicina de Sevilla, IBiS, Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, CIBER CV, Spain
| | - Antonio Castellano
- Instituto de Biomedicina de Sevilla, IBiS, Hospital Universitario Virgen del Rocío, CSIC, Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain.
| | - Juan Ureña
- Instituto de Biomedicina de Sevilla, IBiS, Hospital Universitario Virgen del Rocío, CSIC, Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain.
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13
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Tajada S, Moreno CM, O'Dwyer S, Woods S, Sato D, Navedo MF, Santana LF. Distance constraints on activation of TRPV4 channels by AKAP150-bound PKCα in arterial myocytes. J Gen Physiol 2017; 149:639-659. [PMID: 28507079 PMCID: PMC5460949 DOI: 10.1085/jgp.201611709] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 03/03/2017] [Accepted: 04/27/2017] [Indexed: 11/20/2022] Open
Abstract
Vascular smooth muscle tone can be regulated by angiotensin II, which enhances TRPV4 channel activity via AKAP150-bound protein kinase C. Tajada et al. show that the effect of AKAP150 on TRPV4 channels is inversely proportional to the distance between them, which varies with sex and arterial bed. TRPV4 (transient receptor potential vanilloid 4) channels are Ca2+-permeable channels that play a key role in regulating vascular tone. In arterial myocytes, opening of TRPV4 channels creates local increases in Ca2+ influx, detectable optically as “TRPV4 sparklets.” TRPV4 sparklet activity can be enhanced by the action of the vasoconstrictor angiotensin II (AngII). This modulation depends on the activation of subcellular signaling domains that comprise protein kinase C α (PKCα) bound to the anchoring protein AKAP150. Here, we used super-resolution nanoscopy, patch-clamp electrophysiology, Ca2+ imaging, and mathematical modeling approaches to test the hypothesis that AKAP150-dependent modulation of TRPV4 channels is critically dependent on the distance between these two proteins in the sarcolemma of arterial myocytes. Our data show that the distance between AKAP150 and TRPV4 channel clusters varies with sex and arterial bed. Consistent with our hypothesis, we further find that basal and AngII-induced TRPV4 channel activity decays exponentially as the distance between TRPV4 and AKAP150 increases. Our data suggest a maximum radius of action of ∼200 nm for local modulation of TRPV4 channels by AKAP150-associated PKCα.
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Affiliation(s)
- Sendoa Tajada
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Claudia M Moreno
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Samantha O'Dwyer
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Sean Woods
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Daisuke Sato
- Department of Pharmacology, University of California Davis School of Medicine, Davis, CA
| | - Manuel F Navedo
- Department of Pharmacology, University of California Davis School of Medicine, Davis, CA
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
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14
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Ets HK, Seow CY, Moreland RS. Sustained Contraction in Vascular Smooth Muscle by Activation of L-type Ca 2+ Channels Does Not Involve Ca 2+ Sensitization or Caldesmon. Front Pharmacol 2017; 7:516. [PMID: 28082901 PMCID: PMC5183594 DOI: 10.3389/fphar.2016.00516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 12/12/2016] [Indexed: 11/13/2022] Open
Abstract
Vascular smooth muscle (VSM) is unique in its ability to maintain an intrinsic level of contractile force, known as tone. Vascular tone is believed to arise from the constitutive activity of membrane-bound L-type Ca2+ channels (LTCC). This study used a pharmacological agonist of LTCC, Bay K8644, to elicit a sustained, sub-maximal contraction in VSM that mimics tone. Downstream signaling was investigated in order to determine what molecules are responsible for tone. Medial strips of swine carotid artery were stimulated with 100 nM Bay K8644 to induce a sustained level of force. Force and phosphorylation levels of myosin light chain (MLC), MAP kinase, MYPT1, CPI-17, and caldesmon were measured during Bay K8644 stimulation in the presence and absence of nifedipine, ML-7, U0126, bisindolylmaleimide (Bis), and H-1152. Nifedipine and ML-7 inhibited force and MLC phosphorylation in response to Bay K8644. Inhibition of Rho kinase (H-1152) but not PKC (Bis) inhibited Bay K8644 induced force. U0126 significantly increased Bay K8644-dependent force with no effect on MLC phosphorylation. Neither CPI-17 nor caldesmon phosphorylation were increased during the maintenance of sustained force. Our results suggest that force due to the influx of calcium through LTCCs is partially MLC phosphorylation-dependent but does not involve PKC or caldesmon. Interestingly, inhibition of MLC kinase (MLCK) and PKC significantly increased MAP kinase phosphorylation suggesting that MLCK and PKC may directly or indirectly inhibit MAP kinase activity during prolonged contractions induced by Bay K8544.
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Affiliation(s)
- Hillevi K Ets
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia PA, USA
| | - Chun Y Seow
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver BC, Canada
| | - Robert S Moreland
- Department of Pharmacology and Physiology, Drexel University College of Medicine, PhiladelphiaPA, USA; Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, PhiladelphiaPA, USA
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15
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Karlin A. Membrane potential and Ca2+ concentration dependence on pressure and vasoactive agents in arterial smooth muscle: A model. ACTA ACUST UNITED AC 2016; 146:79-96. [PMID: 26123196 PMCID: PMC4485026 DOI: 10.1085/jgp.201511380] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A mathematical model incorporating junctional and stretch-activated microdomains and 37 protein components describes the myogenic response in arterial smooth muscle cells. Arterial smooth muscle (SM) cells respond autonomously to changes in intravascular pressure, adjusting tension to maintain vessel diameter. The values of membrane potential (Vm) and sarcoplasmic Ca2+ concentration (Cain) within minutes of a change in pressure are the results of two opposing pathways, both of which use Ca2+ as a signal. This works because the two Ca2+-signaling pathways are confined to distinct microdomains in which the Ca2+ concentrations needed to activate key channels are transiently higher than Cain. A mathematical model of an isolated arterial SM cell is presented that incorporates the two types of microdomains. The first type consists of junctions between cisternae of the peripheral sarcoplasmic reticulum (SR), containing ryanodine receptors (RyRs), and the sarcolemma, containing voltage- and Ca2+-activated K+ (BK) channels. These junctional microdomains promote hyperpolarization, reduced Cain, and relaxation. The second type is postulated to form around stretch-activated nonspecific cation channels and neighboring Ca2+-activated Cl− channels, and promotes the opposite (depolarization, increased Cain, and contraction). The model includes three additional compartments: the sarcoplasm, the central SR lumen, and the peripheral SR lumen. It incorporates 37 protein components. In addition to pressure, the model accommodates inputs of α- and β-adrenergic agonists, ATP, 11,12-epoxyeicosatrienoic acid, and nitric oxide (NO). The parameters of the equations were adjusted to obtain a close fit to reported Vm and Cain as functions of pressure, which have been determined in cerebral arteries. The simulations were insensitive to ±10% changes in most of the parameters. The model also simulated the effects of inhibiting RyR, BK, or voltage-activated Ca2+ channels on Vm and Cain. Deletion of BK β1 subunits is known to increase arterial–SM tension. In the model, deletion of β1 raised Cain at all pressures, and these increases were reversed by NO.
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Affiliation(s)
- Arthur Karlin
- Department of Biochemistry and Molecular Biophysics, Department of Physiology and Cellular Biophysics, and Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032
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16
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Tykocki NR, Nelson MT. Location, Location, Location: Juxtaposed calcium-signaling microdomains as a novel model of the vascular smooth muscle myogenic response. J Gen Physiol 2015. [PMID: 26216858 PMCID: PMC4516781 DOI: 10.1085/jgp.201511468] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, VT 05405
| | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT 05405 Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9PL, England, UK
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17
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Hald BO, Welsh DG, Holstein-Rathlou NH, Jacobsen JCB. Gap junctions suppress electrical but not [Ca(2+)] heterogeneity in resistance arteries. Biophys J 2015; 107:2467-76. [PMID: 25418315 DOI: 10.1016/j.bpj.2014.09.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/03/2014] [Accepted: 09/30/2014] [Indexed: 01/03/2023] Open
Abstract
Despite stochastic variation in the molecular composition and morphology of individual smooth muscle and endothelial cells, the membrane potential along intact microvessels is remarkably uniform. This is crucial for coordinated vasomotor responses. To investigate how this electrical homogeneity arises, a virtual arteriole was developed that introduces variation in the activities of ion-transport proteins between cells. By varying the level of heterogeneity and subpopulations of gap junctions (GJs), the resulting simulations shows that GJs suppress electrical variation but can only reduce cytosolic [Ca(2+)] variation. The process of electrical smoothing, however, introduces an energetic cost due to permanent currents, one which is proportional to the level of heterogeneity. This cost is particularly large when electrochemically different endothelial-cell and smooth-muscle-cell layers are coupled. Collectively, we show that homocellular GJs in a passively open state are crucial for electrical uniformity within the given cell layer, but homogenization may be limited by biophysical or energetic constraints. Owing to the ubiquitous presence of ion transport-proteins and cell-cell heterogeneity in biological tissues, these findings generalize across most biological fields.
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Affiliation(s)
- Bjørn Olav Hald
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Donald G Welsh
- Department of Physiology & Pharmacology, University of Calgary, Calgary, Alberta, Canada
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18
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Collier DM, Hill-Eubanks DC, Nelson MT. Orchestrating Ca2+ influx through Ca(V)1.2 and Ca(V)3.x channels in human cerebral arteries. J Gen Physiol 2015; 145:481-3. [PMID: 26009543 PMCID: PMC4442783 DOI: 10.1085/jgp.201511411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Daniel M Collier
- Department of Pharmacology, University of Vermont, Burlington, VT 05405
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT 05405
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19
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Hill-Eubanks DC, Gonzales AL, Sonkusare SK, Nelson MT. Vascular TRP channels: performing under pressure and going with the flow. Physiology (Bethesda) 2015; 29:343-60. [PMID: 25180264 DOI: 10.1152/physiol.00009.2014] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial cells and smooth muscle cells of resistance arteries mediate opposing responses to mechanical forces acting on the vasculature, promoting dilation in response to flow and constriction in response to pressure, respectively. In this review, we explore the role of TRP channels, particularly endothelial TRPV4 and smooth muscle TRPC6 and TRPM4 channels, in vascular mechanosensing circuits, placing their putative mechanosensitivity in context with other proposed upstream and downstream signaling pathways.
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Affiliation(s)
| | - Albert L Gonzales
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, Vermont
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20
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Longden TA, Nelson MT. Vascular inward rectifier K+ channels as external K+ sensors in the control of cerebral blood flow. Microcirculation 2015; 22:183-96. [PMID: 25641345 PMCID: PMC4404517 DOI: 10.1111/micc.12190] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/16/2015] [Indexed: 12/25/2022]
Abstract
For decades it has been known that external K(+) ions are rapid and potent vasodilators that increase CBF. Recent studies have implicated the local release of K(+) from astrocytic endfeet-which encase the entirety of the parenchymal vasculature-in the dynamic regulation of local CBF during NVC. It has been proposed that the activation of KIR channels in the vascular wall by external K(+) is a central component of these hyperemic responses; however, a number of significant gaps in our knowledge remain. Here, we explore the concept that vascular KIR channels are the major extracellular K(+) sensors in the control of CBF. We propose that K(+) is an ideal mediator of NVC, and discuss KIR channels as effectors that produce rapid hyperpolarization and robust vasodilation of cerebral arterioles. We provide evidence that KIR channels, of the KIR 2 subtype in particular, are present in both the endothelial and SM cells of parenchymal arterioles and propose that this dual positioning of KIR 2 channels increases the robustness of the vasodilation to external K(+), enables the endothelium to be actively engaged in NVC, and permits electrical signaling through the endothelial syncytium to promote upstream vasodilation to modulate CBF.
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Affiliation(s)
- Thomas A Longden
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA
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21
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Shi L, Zhang H, Chen Y, Liu Y, Lu N, Zhao T, Zhang L. Chronic exercise normalizes changes in Cav 1.2 and KCa 1.1 channels in mesenteric arteries from spontaneously hypertensive rats. Br J Pharmacol 2015; 172:1846-58. [PMID: 25440572 DOI: 10.1111/bph.13035] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 11/16/2014] [Accepted: 11/24/2014] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. However, the underlying mechanisms are not fully understood. Accumulating evidence shows that the elevated vascular tone in hypertension is a consequence of the 'ion channel remodelling' that occurs during sustained high BP. The present study investigated the effects of aerobic exercise on the electrical remodelling of L-type Ca(2+) (Cav 1.2) and large-conductance Ca(2+) -activated K(+) (KCa 1.1) channels in mesenteric arteries (MAs) from spontaneously hypertensive rats (SHRs). EXPERIMENTAL APPROACH SHRs and normotensive (Wistar-Kyoto) rats were subjected to aerobic training or kept sedentary, and vascular mechanical and functional properties were evaluated. KEY RESULTS Exercise did not affect the heart weight, but reduced the heart rate and body weight in SHR. In mesenteric arterial myocytes, exercise normalized the increased Cav 1.2 and KCa 1.1 current density in SHRs. Exercise also ameliorated the increased open probability and mean open time of the single KCa 1.1 channel in hypertension. The isometric contraction study revealed that both nifedipine (Cav 1.2 channel blocker) and NS11021 (KCa 1.1 channel activator) induced concentration-dependent vasorelaxation in MAs precontracted with noradrenaline. Exercise normalized the increased sensitivity of tissues to nifedipine and NS11021 in SHR. Furthermore, protein expression of the Cav 1.2 α1C -subunit together with the KCa 1.1 α- and β1-subunit was significantly increased in SHRs; and exercise ameliorated these molecular alterations in hypertension. CONCLUSIONS AND IMPLICATIONS Chronic exercise reduces BP and restores vascular function in MAs from SHR, which might be related to the correction of the Cav 1.2 and KCa 1.1 channel remodelling during hypertension.
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Affiliation(s)
- Lijun Shi
- Department of Exercise Physiology, Beijing Sport University, Beijing, China
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22
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Mercado J, Baylie R, Navedo MF, Yuan C, Scott JD, Nelson MT, Brayden JE, Santana LF. Local control of TRPV4 channels by AKAP150-targeted PKC in arterial smooth muscle. ACTA ACUST UNITED AC 2014; 143:559-75. [PMID: 24778429 PMCID: PMC4003184 DOI: 10.1085/jgp.201311050] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Angiotensin signaling promotes interactions between AKAP150, PKC, and TRPV4 channels to form signaling domains that control Ca2+ influx into arterial myocytes. Transient receptor potential vanilloid 4 (TRPV4) channels are Ca2+-permeable, nonselective cation channels expressed in multiple tissues, including smooth muscle. Although TRPV4 channels play a key role in regulating vascular tone, the mechanisms controlling Ca2+ influx through these channels in arterial myocytes are poorly understood. Here, we tested the hypothesis that in arterial myocytes the anchoring protein AKAP150 and protein kinase C (PKC) play a critical role in the regulation of TRPV4 channels during angiotensin II (AngII) signaling. Super-resolution imaging revealed that TRPV4 channels are gathered into puncta of variable sizes along the sarcolemma of arterial myocytes. Recordings of Ca2+ entry via single TRPV4 channels (“TRPV4 sparklets”) suggested that basal TRPV4 sparklet activity was low. However, Ca2+ entry during elementary TRPV4 sparklets was ∼100-fold greater than that during L-type CaV1.2 channel sparklets. Application of the TRPV4 channel agonist GSK1016790A or the vasoconstrictor AngII increased the activity of TRPV4 sparklets in specific regions of the cells. PKC and AKAP150 were required for AngII-induced increases in TRPV4 sparklet activity. AKAP150 and TRPV4 channel interactions were dynamic; activation of AngII signaling increased the proximity of AKAP150 and TRPV4 puncta in arterial myocytes. Furthermore, local stimulation of diacylglycerol and PKC signaling by laser activation of a light-sensitive Gq-coupled receptor (opto-α1AR) resulted in TRPV4-mediated Ca2+ influx. We propose that AKAP150, PKC, and TRPV4 channels form dynamic subcellular signaling domains that control Ca2+ influx into arterial myocytes.
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Affiliation(s)
- Jose Mercado
- Department of Physiology & Biophysics and 2 Howard Hughes Medical Institute, Department of Pharmacology, University of Washington, Seattle, WA 98195
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23
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Mugnai P, Durante M, Sgaragli G, Saponara S, Paliuri G, Bova S, Fusi F. L-type Ca(2+) channel current characteristics are preserved in rat tail artery myocytes after one-day storage. Acta Physiol (Oxf) 2014; 211:334-45. [PMID: 24666564 DOI: 10.1111/apha.12282] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/04/2013] [Accepted: 03/21/2014] [Indexed: 12/14/2022]
Abstract
AIM To develop a cheap and simple method of storing for 24-h vascular tissue and single myocytes while preserving therein the biophysical and pharmacological characteristics of L-type Ca(2+) channels and contractile activity. METHODS Rings or vascular smooth muscle cells obtained from the rat tail main artery were used either freshly (R0h and VSMC0h) or stored for 24 h (R24h and VSMC24h) at 4 °C, to record whole-cell L-type Ca(2+) currents (IC a(L) ) or measure contractile responses. RESULTS R0h/VSMC0h and R24h/VSMC24h comparably contracted when stimulated with phenylephrine, high KCl or ATP. In both VSMC0h and VSMC24h, IC a(L) was identified and characterized as a stable inward current for at least 35 min; IC a(L) was comparably inhibited by the Ca(2+) antagonists nifedipine, verapamil and diltiazem and increased by the Ca(2+) channel agonist (S)-(-)-Bay K 8644; current density and current-voltage relationships were similar; at more hyperpolarized holding potentials, IC a(L) intensity increased comparably; nifedipine shifted the steady-state inactivation curve towards more negative potentials, while verapamil blocked IC a(L) in a frequency-dependent manner and slowed down the rate of recovery from inactivation in a comparable way. CONCLUSION Findings show that smooth muscle contractile activity and the biophysical and pharmacological features of L-type Ca(2+) channels are similar in VSMC24h and VSMC0h. The fact that reproducible results were obtained in vascular myocytes up to 24 h after dissociation may facilitate vascular smooth muscle cell investigation by increasing throughput and reducing the number of animals required.
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Affiliation(s)
- P. Mugnai
- Dipartimento di Scienze della Vita; Università di Siena; Siena Italy
| | - M. Durante
- Dipartimento di Scienze della Vita; Università di Siena; Siena Italy
| | - G. Sgaragli
- Dipartimento di Scienze della Vita; Università di Siena; Siena Italy
| | - S. Saponara
- Dipartimento di Scienze della Vita; Università di Siena; Siena Italy
| | - G. Paliuri
- Dipartimento di Scienze del Farmaco; Università degli Studi di Padova; Padova Italy
| | - S. Bova
- Dipartimento di Scienze del Farmaco; Università degli Studi di Padova; Padova Italy
| | - F. Fusi
- Dipartimento di Scienze della Vita; Università di Siena; Siena Italy
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24
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Sidaway P, Teramoto N. L-type Ca2+ channel sparklets revealed by TIRF microscopy in mouse urinary bladder smooth muscle. PLoS One 2014; 9:e93803. [PMID: 24699670 PMCID: PMC3974850 DOI: 10.1371/journal.pone.0093803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Accepted: 03/06/2014] [Indexed: 12/03/2022] Open
Abstract
Calcium is a ubiquitous second messenger in urinary bladder smooth muscle (UBSM). In this study, small discrete elevations of intracellular Ca(2+), referred to as Ca(2+) sparklets have been detected in an intact detrusor smooth muscle electrical syncytium using a TIRF microscopy Ca(2+) imaging approach. Sparklets were virtually abolished by the removal of extracellular Ca(2+) (0.035 ± 0.01 vs. 0.23 ± 0.07 Hz/mm(2); P<0.05). Co-loading of smooth muscle strips with the slow Ca(2+) chelator EGTA-AM (10 mM) confirmed that Ca(2+) sparklets are restricted to the cell membrane. Ca(2+) sparklets were inhibited by the calcium channel inhibitors R-(+)-Bay K 8644 (1 μM) (0.034 ± 0.02 vs. 0.21 ± 0.08 Hz/mm(2); P<0.05), and diltiazem (10 μM) (0.097 ± 0.04 vs. 0.16 ± 0.06 Hz/mm(2); P<0.05). Ca(2+) sparklets were unaffected by inhibition of P2X1 receptors α,β-meATP (10 μM) whilst sparklet frequencies were significantly reduced by atropine (1 μM). Ca(2+) sparklet frequency was significantly reduced by PKC inhibition with Gö6976 (100 nM) (0.030 ± 0.01 vs. 0.30 ± 0.1 Hz/mm(2); P<0.05), demonstrating that Ca(2+) sparklets are PKC dependant. In the presence of CPA (10 μM), there was no apparent change in the overall frequency of Ca(2+) sparklets, although the sparklet frequencies of each UBSM became statistically independent of each other (Spearman's rank correlation 0.2, P>0.05), implying that Ca(2+) store mediated signals regulate Ca(2+) sparklets. Under control conditions, inhibition of store operated Ca(2+) entry using ML-9 (100 μM) had no significant effect. Amplitudes of Ca(2+) sparklets were unaffected by any agonists or antagonists, suggesting that these signals are quantal events arising from activation of a single channel, or complex of channels. The effects of CPA and ML-9 suggest that Ca(2+) sparklets regulate events in the cell membrane, and contribute to cytosolic and sarcoplasmic Ca(2+) concentrations.
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Affiliation(s)
- Peter Sidaway
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga City, Japan
| | - Noriyoshi Teramoto
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga City, Japan
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Navedo MF, Amberg GC. Local regulation of L-type Ca²⁺ channel sparklets in arterial smooth muscle. Microcirculation 2013; 20:290-8. [PMID: 23116449 DOI: 10.1111/micc.12021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 10/26/2012] [Indexed: 12/16/2022]
Abstract
This review addresses the latest advances in our understanding of the regulation of a novel Ca²⁺ signal called L-type Ca²⁺ channel sparklets in arterial smooth muscle. L-type Ca²⁺ channel sparklets are elementary Ca²⁺ influx events produced by the opening of a single or a small cluster of L-type Ca²⁺ channels. These Ca²⁺ signals were first visualized in the vasculature in arterial smooth muscle cells. In these cells, L-type Ca²⁺ channel sparklets display two functionally distinct gating modalities that regulate local and global [Ca²⁺](i). The activity of L-type Ca²⁺ channel sparklets varies regionally within a cell depending on the dynamic activity of a cohort of protein kinases and phosphatases recruited to L-type Ca²⁺ channels in the arterial smooth muscle sarcolemma in a complex coordinated by the scaffolding molecule AKAP150. We also described a mechanism whereby clusters of L-type Ca²⁺ channels gate cooperatively to amplify intracellular Ca²⁺ signals with likely pathological consequences.
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Affiliation(s)
- Manuel F Navedo
- Department of Pharmacology, University of California, Davis, California, USA.
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26
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Amberg GC, Navedo MF. Calcium dynamics in vascular smooth muscle. Microcirculation 2013; 20:281-9. [PMID: 23384444 DOI: 10.1111/micc.12046] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/31/2013] [Indexed: 12/31/2022]
Abstract
Smooth muscle cells are ultimately responsible for determining vascular luminal diameter and blood flow. Dynamic changes in intracellular calcium are a critical mechanism regulating vascular smooth muscle contractility. Processes influencing intracellular calcium are therefore important regulators of vascular function with physiological and pathophysiological consequences. In this review we discuss the major dynamic calcium signals identified and characterized in vascular smooth muscle cells. These signals vary with respect to their mechanisms of generation, temporal properties, and spatial distributions. The calcium signals discussed include calcium waves, junctional calcium transients, calcium sparks, calcium puffs, and L-type calcium channel sparklets. For each calcium signal we address underlying mechanisms, general properties, physiological importance, and regulation.
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Affiliation(s)
- Gregory C Amberg
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
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27
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Tajada S, Cidad P, Colinas O, Santana LF, López-López JR, Pérez-García MT. Down-regulation of CaV1.2 channels during hypertension: how fewer CaV1.2 channels allow more Ca(2+) into hypertensive arterial smooth muscle. J Physiol 2013; 591:6175-91. [PMID: 24167226 DOI: 10.1113/jphysiol.2013.265751] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Hypertension is a clinical syndrome characterized by increased arterial tone. Although the mechanisms are varied, the generally accepted view is that increased CaV1.2 channel function is a common feature of this pathological condition. Here, we investigated the mechanisms underlying vascular dysfunction in a mouse model of genetic hypertension. Contrary to expectation, we found that whole-cell CaV1.2 currents (ICa) were lower in hypertensive (BPH line) than normotensive (BPN line) myocytes. However, local CaV1.2 sparklet activity was higher in BPH cells, suggesting that the relatively low ICa in these cells was produced by a few hyperactive CaV1.2 channels. Furthermore, our data suggest that while the lower expression of the pore-forming α1c subunit of CaV1.2 currents underlies the lower ICa in BPH myocytes, the increased sparklet activity was due to a different composition in the auxiliary subunits of the CaV1.2 complexes. ICa currents in BPN cells were produced by channels composed of α1c/α2δ/β3 subunits, while in BPH myocytes currents were probably generated by the opening of channels formed by α1c/α2δ/β2 subunits. In addition, Ca(2+) sparks evoked large conductance, Ca(2+)-activated K(+) (BK) currents of lower magnitude in BPH than in BPN myocytes, because BK channels were less sensitive to Ca(2+). Our data are consistent with a model in which a decrease in the global number of CaV1.2 currents coexist with the existence of a subpopulation of highly active channels that dominate the resting Ca(2+) influx. The decrease in BK channel activity makes the hyperpolarizing brake ineffective and leads BPH myocytes to a more contracted resting state.
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Affiliation(s)
- Sendoa Tajada
- Jose R. López-López: Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid, Edificio IBGM, c/ Sanz y Forés s/n, 47003 Valladolid, Spain.
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28
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Cox RH, Fromme SJ. A naturally occurring truncated Cav1.2 α1-subunit inhibits Ca2+ current in A7r5 cells. Am J Physiol Cell Physiol 2013; 305:C896-905. [PMID: 23926129 DOI: 10.1152/ajpcell.00217.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Alternative splicing of the voltage-gated Ca(2+) (CaV) α1-subunit adds to the functional diversity of Ca(2+) channels. A variant with a 73-nt deletion in exon 15 of the Cav1.2 α1-subunit (Cav1.2Δ73) produced by alternative splicing that predicts a truncated protein has been described, but its function, if any, is unknown. We sought to determine if, by analogy to other truncated CaV α1-subunits, Cav1.2Δ73 acts as an inhibitor of wild-type Cav1.2 currents. HEK-293 cells were transfected with Cav1.2Δ73 in a pIRES vector with CD8 or in pcDNA3.1 with a V5/his COOH-terminal tag plus β2 and α2δ1 accessory subunits and pEGFP. Production of Cav1.2Δ73 protein was confirmed by Western blotting and immunofluorescence. Voltage-clamp studies revealed the absence of functional channels in transfected cells. In contrast, cells transfected with full-length Cav1.2 plus accessory subunits and pEGFP exhibited robust Ca(2+) currents. A7r5 cells exhibited endogenous Cav1.2-based currents that were greatly reduced (>80%) without a change in voltage-dependent activation when transfected with Cav1.2Δ73-IRES-CD8 compared with empty vector or pIRES-CD8 controls. Transfection of A7r5 cells with an analogous Cav2.3Δ73-IRES-CD8 had no effect on Ca(2+) currents. Immunofluorescence showed intracellular, but not plasma membrane, localization of Cav1.2Δ73-V5/his, as well as colocalization with an endoplasmic reticulum marker, ER Organelle Lights. Expression of Cav1.2Δ73 α1-subunits in A7r5 cells inhibits endogenous Cav1.2 currents. The fact that this variant arises naturally by alternative splicing raises the possibility that it may represent a physiological mechanism to modulate Cav1.2 functional activity.
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Affiliation(s)
- Robert H Cox
- Program in Cardiovascular Studies, Lankenau Institute for Medical Research, Main Line Health System, Wynnewood, Pennsylvania
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29
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Navedo MF, Santana LF. CaV1.2 sparklets in heart and vascular smooth muscle. J Mol Cell Cardiol 2012; 58:67-76. [PMID: 23220157 DOI: 10.1016/j.yjmcc.2012.11.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 11/16/2012] [Accepted: 11/28/2012] [Indexed: 10/27/2022]
Abstract
CaV1.2 sparklets are local elevations in intracellular Ca(2+) ([Ca(2+)]i) resulting from the opening of a single or small cluster of voltage-gated, dihydropyridine-sensitive CaV1.2 channels. Activation of CaV1.2 sparklets is an early event in the signaling cascade that couples membrane depolarization to contraction (i.e., excitation-contraction coupling) in cardiac and arterial smooth muscle. Here, we review recent work on the molecular and biophysical mechanisms that regulate CaV1.2 sparklet activity in these cells. CaV1.2 sparklet activity is tightly regulated by a cohort of protein kinases and phosphatases that are targeted to specific regions of the sarcolemma by the anchoring protein AKAP150. We discuss a model for the local control of Ca(2+) influx via CaV1.2 channels in which a signaling complex formed by AKAP79/150, protein kinase C, protein kinase A, and calcineurin regulates the activity of individual CaV1.2 channels and also facilitates the coordinated activation of small clusters of these channels. This results in amplification of Ca(2+) influx, which strengthens excitation-contraction coupling in cardiac and vascular smooth muscle.
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Affiliation(s)
- Manuel F Navedo
- Department of Pharmacology, University of California, Davis, One Shields Ave., Davis, CA 95616, USA.
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30
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Fernández-Tenorio M, Porras-González C, Castellano A, López-Barneo J, Ureña J. Tonic arterial contraction mediated by L-type Ca2+ channels requires sustained Ca2+ influx, G protein-associated Ca2+ release, and RhoA/ROCK activation. Eur J Pharmacol 2012; 697:88-96. [PMID: 23051677 DOI: 10.1016/j.ejphar.2012.09.047] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 09/20/2012] [Accepted: 09/21/2012] [Indexed: 11/25/2022]
Abstract
KCl-evoked sustained contraction requires L-type Ca(2+) channel activation, metabotropic Ca(2+) release from the sarcoplasmic reticulum (mechanism denoted calcium channel-induced Ca(2+) release) and RhoA/Rho associated kinase activation. Although high K(+) solutions are used to depolarize myocytes, these solutions can stimulate other signaling pathways such as those triggered by the activation of muscarinic and purinergic receptors. The present study examines the functional role of calcium channel-induced Ca(2+) release under pharmacological activation of L-type Ca(2+) channel without significant membrane depolarization. It also analyzes the role of the "steady-state" Ca(2+) influx through L-type Ca(2+) channels on myocyte sustained contraction. Measurement of contractility in arterial rings was done on a vessel myograph. Membrane potential was measured by fluorescence techniques loading intact myocytes with a membrane potential sensitive dye, and a reversible permeabilization method was used to load myocytes in intact arteries with GDPβS and Ca(v)1.2 siRNA. Application of an L-type Ca(2+) channel agonist, without effect on membrane potential, evoked sustained contraction via G-protein induced Ca(2+) release from the sarcoplasmic reticulum and RhoA/Rho associated kinase activation. Tonic myocyte contractions mediated by L-type Ca(2+) channel activation required sustained Ca(2+) influx through the channels and Ca(2+) uptake by the sarcoplasmic reticulum. Because L-type Ca(2+) channels participate in numerous pathophysiological processes mediated by maintained arterial contraction, our data could help to optimize therapeutic treatment of arterial vasospasm.
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Affiliation(s)
- Miguel Fernández-Tenorio
- Instituto de Biomedicina de Sevilla and Dpto. Fisiología Médica y Biofísica, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain
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31
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Choi EK, Chang PC, Lee YS, Lin SF, Zhu W, Maruyama M, Fishbein MC, Chen Z, Rubart-von der Lohe M, Field LJ, Chen PS. Triggered firing and atrial fibrillation in transgenic mice with selective atrial fibrosis induced by overexpression of TGF-β1. Circ J 2012; 76:1354-62. [PMID: 22447020 DOI: 10.1253/circj.cj-11-1301] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Calcium transient triggered firing (CTTF) is induced by large intracellular calcium (Ca(i)) transient and short action potential duration (APD). We hypothesized that CTTF underlies the mechanisms of early afterdepolarization (EAD) and spontaneous recurrent atrial fibrillation (AF) in transgenic (Tx) mice with overexpression of transforming growth factor β1 (TGF-β1). METHODS AND RESULTS MHC-TGFcys(33)ser Tx mice develop atrial fibrosis because of elevated levels of TGF-β1. We studied membrane potential and Ca(i)transients of isolated superfused atria from Tx and wild-type (Wt) littermates. Short APD and persistently elevated Ca(i) transients promoted spontaneous repetitive EADs, triggered activity and spontaneous AF after cessation of burst pacing in Tx but not Wt atria (39% vs. 0%, P=0.008). We were able to map optically 4 episodes of spontaneous AF re-initiation. All first and second beats of spontaneous AF originated from the right atrium (4/4, 100%), which is more severely fibrotic than the left atrium. Ryanodine and thapsigargin inhibited spontaneous re-initiation of AF in all 7 Tx atria tested. Western blotting showed no significant changes of calsequestrin or sarco/endoplasmic reticulum Ca(2+)-ATPase 2a. CONCLUSIONS Spontaneous AF may occur in the Tx atrium because of CTTF, characterized by APD shortening, prolonged Ca(i) transient, EAD and triggered activity. Inhibition of Ca(2+) release from the sarcoplasmic reticulum suppressed spontaneous AF. Our results indicate that CTTF is an important arrhythmogenic mechanism in TGF-β1 Tx atria.
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Affiliation(s)
- Eue-Keun Choi
- Krannert Institute of Cardiology and the Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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Chaplin NL, Amberg GC. Hydrogen peroxide mediates oxidant-dependent stimulation of arterial smooth muscle L-type calcium channels. Am J Physiol Cell Physiol 2012; 302:C1382-93. [PMID: 22322977 DOI: 10.1152/ajpcell.00222.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Changes in calcium and redox homeostasis influence multiple cellular processes. Dysregulation of these signaling modalities is associated with pathology in cardiovascular, neuronal, endocrine, and other physiological systems. Calcium and oxidant signaling mechanisms are frequently inferred to be functionally related. To address and clarify this clinically relevant issue in the vasculature we tested the hypothesis that the ubiquitous reactive oxygen molecule hydrogen peroxide mediates oxidant-dependent stimulation of cerebral arterial smooth muscle L-type calcium channels. Using a combinatorial approach including intact arterial manipulations, electrophysiology, and total internal reflection fluorescence imaging, we found that application of physiological levels of hydrogen peroxide to isolated arterial smooth muscle cells increased localized calcium influx through L-type calcium channels. Similarly, oxidant-dependent stimulation of L-type calcium channels by the vasoconstrictor ANG II was abolished by intracellular application of catalase. Catalase also prevented ANG II from increasing localized subplasmalemmal sites of increased oxidation previously associated with colocalized calcium influx through L-type channels. Furthermore, catalase largely attenuated the contractile response of intact cerebral arterial segments to ANG II. In contrast, enhanced dismutation of superoxide to hydrogen peroxide with SOD had no effect on ANG II-dependent stimulation of L-type calcium channels. From these data we conclude that hydrogen peroxide is important for oxidant-dependent regulation of smooth muscle L-type calcium channels and arterial function. These data also support the emerging concept of hydrogen peroxide as a biologically relevant oxidant second messenger in multiple cell types with a diverse array of physiological functions.
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Affiliation(s)
- Nathan L Chaplin
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA
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33
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Gonzales AL, Earley S. Endogenous cytosolic Ca(2+) buffering is necessary for TRPM4 activity in cerebral artery smooth muscle cells. Cell Calcium 2012; 51:82-93. [PMID: 22153976 PMCID: PMC3265659 DOI: 10.1016/j.ceca.2011.11.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/28/2011] [Accepted: 11/14/2011] [Indexed: 10/14/2022]
Abstract
The melastatin transient receptor potential (TRP) channel, TRPM4, is a critical regulator of smooth muscle membrane potential and arterial tone. Activation of the channel is Ca(2+)-dependent, but prolonged exposures to high global Ca(2+) causes rapid inactivation under conventional whole-cell patch clamp conditions. Using amphotericin B perforated whole cell patch clamp electrophysiology, which minimally disrupts cytosolic Ca(2+) dynamics, we recently showed that Ca(2+) released from 1,2,5-triphosphate receptors (IP(3)R) on the sarcoplasmic reticulum (SR) activates TRPM4 channels, producing sustained transient inward cation currents (TICCs). Thus, Ca(2+)-dependent inactivation of TRPM4 may not be inherent to the channel itself but rather is a result of the recording conditions. We hypothesized that under conventional whole-cell configurations, loss of intrinsic cytosolic Ca(2+) buffering following cell dialysis contributes to inactivation of TRPM4 channels. With the inclusion of the Ca(2+) buffers ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA, 10mM) or bis-ethane-N,N,N',N'-tetraacetic acid (BAPTA, 0.1mM) in the pipette solution, we mimic endogenous Ca(2+) buffering and record novel, sustained whole-cell TICC activity from freshly-isolated cerebral artery myocytes. Biophysical properties of TICCs recorded under perforated and whole-cell patch clamp were nearly identical. Furthermore, whole-cell TICC activity was reduced by the selective TRPM4 inhibitor, 9-phenanthrol, and by siRNA-mediated knockdown of TRPM4. When a higher concentration (10mM) of BAPTA was included in the pipette solution, TICC activity was disrupted, suggesting that TRPM4 channels on the plasma membrane and IP(3)R on the SR are closely opposed but not physically coupled, and that endogenous Ca(2+) buffer proteins play a critical role in maintaining TRPM4 channel activity in native cerebral artery smooth muscle cells.
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Affiliation(s)
- Albert L Gonzales
- Vascular Physiology Research Group, Department of Biomedical Sciences Colorado State University Fort Collins, CO 80523-1617, USA
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Calcium signaling in vascular smooth muscle cells: from physiology to pathology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:795-810. [PMID: 22453970 DOI: 10.1007/978-94-007-2888-2_35] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cyclic variations in calcium (Ca(2+)) concentrations, through a process called excitation-contraction coupling, allow regulation of vascular smooth muscle cells contractility and thus modulation of vascular tone and blood pressure. As a second messenger, Ca(2+) also activates signaling cascades leading to transcription factors activation in a process called excitation-transcription coupling. Furthermore, recent evidences indicate an interaction between post-transcriptional regulation by microRNAs (miRNAs) and Ca(2+) signaling. All these actors, which are frequently altered in vascular diseases, will be reviewed here.
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Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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Affiliation(s)
- J T Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School ofMedicine, Baltimore, Maryland, USA.
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Amberg GC, Earley S, Glapa SA. Local regulation of arterial L-type calcium channels by reactive oxygen species. Circ Res 2010; 107:1002-10. [PMID: 20798361 DOI: 10.1161/circresaha.110.217018] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
RATIONALE Reactive oxygen species (ROS) are implicated in the development of cardiovascular disease, and oxidants are important signaling molecules in many cell types. Recent evidence suggests that localized subcellular compartmentalization of ROS generation is an important feature of ROS signaling. However, mechanisms that transduce localized subcellular changes in redox status to functionally relevant changes in cellular processes such as Ca(2+) influx are poorly understood. OBJECTIVE To test the hypothesis that ROS regulate L-type Ca(2+) channel activity in cerebral arterial smooth muscle. METHODS AND RESULTS Using a total internal reflection fluorescence imaging-based approach, we found that highly localized subplasmalemmal generation of endogenous ROS preceded and colocalized with sites of enhanced L-type Ca(2+) channel sparklet activity in isolated cerebral arterial smooth muscle cells. Consistent with this observation and our hypothesis, exogenous ROS increased localized L-type Ca(2+) channel sparklet activity in isolated arterial myocytes via activation of protein kinase Cα and when applied to intact cerebral arterial segments, exogenous ROS increased arterial tone in an L-type Ca(2+) channel-dependent fashion. Furthermore, angiotensin II-dependent stimulation of local L-type Ca(2+) channel sparklet activity in isolated cells and contraction of intact arteries was abolished following inhibition of NADPH oxidase. CONCLUSIONS Our data support a novel model of local oxidative regulation of Ca(2+) influx where vasoconstrictors coupled to NAPDH oxidase (eg, angiotensin II) induce discrete sites of ROS generation resulting in oxidative activation of adjacent protein kinase Cα molecules that in turn promote local sites of enhanced L-type Ca(2+) channel activity, resulting in increased Ca(2+) influx and contraction.
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Affiliation(s)
- Gregory C Amberg
- Colorado State University, Department of Biomedical Sciences, 1617 Campus Delivery, Fort Collins, CO 80523, USA.
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Abstract
Neuronal activity is communicated to the cerebral vasculature so that adequate perfusion of brain tissue is maintained at all levels of neuronal metabolism. An increase in neuronal activity is accompanied by vasodilation and an increase in local cerebral blood flow. This process, known as neurovascular coupling (NVC) or functional hyperemia, is essential for cerebral homeostasis and survival. Neuronal activity is encoded in astrocytic Ca(2+) signals that travel to astrocytic processes (;endfeet') encasing parenchymal arterioles within the brain. Astrocytic Ca(2+) signals cause the release of vasoactive substances to cause relaxation, and in some circumstances contraction, of the smooth muscle cells (SMCs) of parenchymal arterioles to modulate local cerebral blood flow. Activation of potassium channels in the SMCs has been proposed to mediate NVC. Here, the current state of knowledge of NVC and potassium channels in parenchymal arterioles is reviewed.
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Affiliation(s)
- Kathryn M Dunn
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405, USA
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Astrocytic endfoot Ca2+ and BK channels determine both arteriolar dilation and constriction. Proc Natl Acad Sci U S A 2010; 107:3811-6. [PMID: 20133576 DOI: 10.1073/pnas.0914722107] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Neuronal activity is thought to communicate to arterioles in the brain through astrocytic calcium (Ca(2+)) signaling to cause local vasodilation. Paradoxically, this communication may cause vasoconstriction in some cases. Here, we show that, regardless of the mechanism by which astrocytic endfoot Ca(2+) was elevated, modest increases in Ca(2+) induced dilation, whereas larger increases switched dilation to constriction. Large-conductance, Ca(2+)-sensitive potassium channels in astrocytic endfeet mediated a majority of the dilation and the entire vasoconstriction, implicating local extracellular K(+) as a vasoactive signal for both dilation and constriction. These results provide evidence for a unifying mechanism that explains the nature and apparent duality of the vascular response, showing that the degree and polarity of neurovascular coupling depends on astrocytic endfoot Ca(2+) and perivascular K(+).
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Navedo MF, Cheng EP, Yuan C, Votaw S, Molkentin JD, Scott JD, Santana LF. Increased coupled gating of L-type Ca2+ channels during hypertension and Timothy syndrome. Circ Res 2010; 106:748-56. [PMID: 20110531 DOI: 10.1161/circresaha.109.213363] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
RATIONALE L-Type (Cav1.2) Ca(2+) channels are critical regulators of muscle and neural function. Although Cav1.2 channel activity varies regionally, little is known about the mechanisms underlying this heterogeneity. OBJECTIVE To test the hypothesis that Cav1.2 channels can gate coordinately. METHODS AND RESULTS We used optical and electrophysiological approaches to record Cav1.2 channel activity in cardiac, smooth muscle, and tsA-201 cells expressing Cav1.2 channels. Consistent with our hypothesis, we found that small clusters of Cav1.2 channels can open and close in tandem. Fluorescence resonance energy transfer and electrophysiological studies suggest that this coupling of Cav1.2 channels involves transient interactions between neighboring channels via their C termini. The frequency of coupled gating events increases in hypertensive smooth muscle and in cells expressing a mutant Cav1.2 channel that causes arrhythmias and autism in humans with Timothy syndrome (LQT8). CONCLUSIONS Coupled gating of Cav1.2 channels may represent a novel mechanism for the regulation of Ca(2+) influx and excitability in neurons, cardiac, and arterial smooth muscle under physiological and pathological conditions.
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MESH Headings
- A Kinase Anchor Proteins/genetics
- A Kinase Anchor Proteins/metabolism
- Animals
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/drug effects
- Calcium-Calmodulin-Dependent Protein Kinases/antagonists & inhibitors
- Calcium-Calmodulin-Dependent Protein Kinases/metabolism
- Calmodulin/metabolism
- Cells, Cultured
- Enzyme Activation
- Enzyme Activators/pharmacology
- Fluorescence Resonance Energy Transfer
- Humans
- Hypertension/genetics
- Hypertension/metabolism
- Hypertension/physiopathology
- Ion Channel Gating/drug effects
- Long QT Syndrome/genetics
- Long QT Syndrome/metabolism
- Long QT Syndrome/physiopathology
- Membrane Potentials
- Mice
- Mice, Knockout
- Microscopy, Confocal
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Mutation
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Patch-Clamp Techniques
- Protein Kinase C-alpha/genetics
- Protein Kinase C-alpha/metabolism
- Protein Kinase Inhibitors/pharmacology
- Protein Structure, Tertiary
- Protein Transport
- Rabbits
- Rats
- Rats, Sprague-Dawley
- Recombinant Fusion Proteins/metabolism
- Time Factors
- Transfection
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Affiliation(s)
- Manuel F Navedo
- Department of Physiology & Biophysics, University of Washington-Seattle, 1705 NE Pacific Street, Seattle, WA 98195, USA
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40
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Zhuge R, Bao R, Fogarty KE, Lifshitz LM. Ca2+ sparks act as potent regulators of excitation-contraction coupling in airway smooth muscle. J Biol Chem 2009; 285:2203-10. [PMID: 19920135 DOI: 10.1074/jbc.m109.067546] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca2+ sparks are short lived and localized Ca2+ transients resulting from the opening of ryanodine receptors in sarcoplasmic reticulum. These events relax certain types of smooth muscle by activating big conductance Ca2+-activated K+ channels to produce spontaneous transient outward currents (STOCs) and the resultant closure of voltage-dependent Ca2+ channels. But in many smooth muscles from a variety of organs, Ca2+ sparks can additionally activate Ca2+-activated Cl(-) channels to generate spontaneous transient inward current (STICs). To date, the physiological roles of Ca2+ sparks in this latter group of smooth muscle remain elusive. Here, we show that in airway smooth muscle, Ca2+ sparks under physiological conditions, activating STOCs and STICs, induce biphasic membrane potential transients (BiMPTs), leading to membrane potential oscillations. Paradoxically, BiMPTs stabilize the membrane potential by clamping it within a negative range and prevent the generation of action potentials. Moreover, blocking either Ca2+ sparks or hyperpolarization components of BiMPTs activates voltage-dependent Ca2+ channels, resulting in an increase in global [Ca2+](i) and cell contraction. Therefore, Ca2+ sparks in smooth muscle presenting both STICs and STOCs act as a stabilizer of membrane potential, and altering the balance can profoundly alter the status of excitability and contractility. These results reveal a novel mechanism underlying the control of excitability and contractility in smooth muscle.
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Affiliation(s)
- Ronghua Zhuge
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
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41
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Navedo MF, Takeda Y, Nieves-Cintrón M, Molkentin JD, Santana LF. Elevated Ca2+ sparklet activity during acute hyperglycemia and diabetes in cerebral arterial smooth muscle cells. Am J Physiol Cell Physiol 2009; 298:C211-20. [PMID: 19846755 DOI: 10.1152/ajpcell.00267.2009] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca(+) sparklets are subcellular Ca(2+) signals produced by the opening of L-type Ca(2+) channels (LTCCs). In cerebral arterial myocytes, Ca(2+) sparklet activity varies regionally, resulting in low and high activity, "persistent" Ca(2+) sparklet sites. Although increased Ca(2+) influx via LTCCs in arterial myocytes has been implicated in the chain of events contributing to vascular dysfunction during acute hyperglycemia and diabetes, the mechanisms underlying these pathological changes remain unclear. Here, we tested the hypothesis that increased Ca(2+) sparklet activity contributes to higher Ca(2+) influx in cerebral artery smooth muscle during acute hyperglycemia and in an animal model of non-insulin-dependent, type 2 diabetes: the dB/dB mouse. Consistent with this hypothesis, acute elevation of extracellular glucose from 10 to 20 mM increased the density of low activity and persistent Ca(2+) sparklet sites as well as the amplitude of LTCC currents in wild-type cerebral arterial myocytes. Furthermore, Ca(2+) sparklet activity and LTCC currents were higher in dB/dB than in control myocytes. We found that activation of PKA contributed to higher Ca(2+) sparklet activity during hyperglycemia and diabetes. In addition, we found that the interaction between PKA and the scaffolding protein A-kinase anchoring protein was critical for the activation of persistent Ca(2+) sparklets by PKA in cerebral arterial myocytes after hyperglycemia. Accordingly, PKA inhibition equalized Ca(2+) sparklet activity between dB/dB and wild-type cells. These findings suggest that hyperglycemia increases Ca(2+) influx by increasing Ca(2+) sparklet activity via a PKA-dependent pathway in cerebral arterial myocytes and contributes to vascular dysfunction during diabetes.
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Affiliation(s)
- Manuel F Navedo
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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42
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Santana LF, Navedo MF. Molecular and biophysical mechanisms of Ca2+ sparklets in smooth muscle. J Mol Cell Cardiol 2009; 47:436-44. [PMID: 19616004 DOI: 10.1016/j.yjmcc.2009.07.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 06/17/2009] [Accepted: 07/06/2009] [Indexed: 11/25/2022]
Abstract
In this article, we review the biophysical basis and functional implications of a novel Ca(2+) signal (called "Ca(2+) sparklets") produced by Ca(2+) influx via L-type Ca(2+) channels (LTCCs) in smooth muscle. Ca(2+) sparklet activity is bimodal. In low activity mode, Ca(2+) sparklets are produced by random, brief openings of solitary LTCCs. In contrast, small clusters of LTCCs can function in a high activity mode that creates sites of continual Ca(2+) influx called "persistent Ca(2+) sparklets". Low activity and persistent Ca(2+) sparklets contribute to Ca(2+) influx in arterial, colonic, and venous smooth muscle. Targeting of PKCalpha by the scaffolding protein AKAP150 to specific sarcolemmal domains is required for the activation of persistent Ca(2+) sparklets. Calcineurin, which is also associated with AKAP150, opposes the actions of PKCalpha on Ca(2+) sparklets. At hyperpolarized potentials, Ca(2+) sparklet activity is low and hence does not contribute to global [Ca(2+)](i). Membrane depolarization increases low and persistent Ca(2+) sparklet activity, thereby increasing local and global [Ca(2+)](i). Ca(2+) sparklet activity is increased in arterial myocytes during hypertension, thus increasing Ca(2+) influx and activating the transcription factor NFATc3. We discuss a model for subcellular variations in Ca(2+) sparklet activity and their role in the regulation of excitation-contraction coupling and excitation-transcription coupling in smooth muscle.
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Affiliation(s)
- Luis F Santana
- Department of Physiology and Biophysics, University of Washington, Box 357290, Seattle, WA 98195, USA.
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43
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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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44
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Saponara S, Sgaragli G, Fusi F. Quercetin antagonism of Bay K 8644 effects on rat tail artery L-type Ca2+ channels. Eur J Pharmacol 2008; 598:75-80. [DOI: 10.1016/j.ejphar.2008.08.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 08/11/2008] [Accepted: 08/22/2008] [Indexed: 01/06/2023]
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45
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Santana LF, Navedo MF, Amberg GC, Nieves-Cintrón M, Votaw VS, Ufret-Vincenty CA. Calcium sparklets in arterial smooth muscle. Clin Exp Pharmacol Physiol 2008; 35:1121-6. [PMID: 18215181 PMCID: PMC5832963 DOI: 10.1111/j.1440-1681.2007.04867.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Voltage-dependent, L-type Ca2+ channels (LTCC) play an essential role in arterial smooth muscle contraction and, consequently, the regulation of arterial diameter, tissue perfusion and blood pressure. However, the spatial organization of functional LTCC in arterial myocytes is incompletely understood. Total internal reflection fluorescence and swept-field confocal microscopy revealed that the opening of a single or a cluster of LTCC produces local elevations in [Ca2+]i called Ca2+ sparklets. In arterial myocytes, Ca2+ sparklets are produced by the opening of Cav1.2 channels. The Ca2+ sparklet activity is bimodal. In low activity mode, rare stochastic openings of solitary LTCC produce limited Ca2+ influx ('low activity Ca2+ sparklets'). In contrast, discrete clusters of LTCC associated with protein kinase Ca (PKCa) operate in a sustained, high-activity mode resulting in substantial Ca2+ influx ('persistent Ca2+ sparklets'). The Ca2+ sparklet activity varies regionally within a myocyte depending on the relative activities of nearby PKCa and opposing protein phosphates 2A and 2B. Low- and high-activity persistent Ca2+ sparklets modulate local and global [Ca2+]i in arterial smooth muscle, suggesting that this Ca2+ signal may play an important role in the regulation of vascular function.
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Affiliation(s)
- Luis F Santana
- Department of Physiology and Biophysics, University of Washington School of Medicine, Box 357290, Seattle, WA 98195, USA.
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46
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Mackie AR, Brueggemann LI, Henderson KK, Shiels AJ, Cribbs LL, Scrogin KE, Byron KL. Vascular KCNQ potassium channels as novel targets for the control of mesenteric artery constriction by vasopressin, based on studies in single cells, pressurized arteries, and in vivo measurements of mesenteric vascular resistance. J Pharmacol Exp Ther 2008; 325:475-83. [PMID: 18272810 PMCID: PMC2597077 DOI: 10.1124/jpet.107.135764] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Pressor effects of the vasoconstrictor hormone arginine vasopressin (AVP), observed when systemic AVP concentrations are less than 100 pM, are important for the physiological maintenance of blood pressure, and they are also the basis for therapeutic use of vasopressin to restore blood pressure in hypotensive patients. However, the mechanisms by which circulating AVP induces arterial constriction are unclear. We examined the novel hypothesis that KCNQ potassium channels mediate the physiological vasoconstrictor actions of AVP. Reverse transcriptase polymerase chain reaction revealed expression of KCNQ1, KCNQ4, and KCNQ5 in rat mesenteric artery smooth muscle cells (MASMCs). Whole-cell perforated patch recordings of voltage-sensitive K+ (Kv) currents in freshly isolated MASMCs revealed 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-2H-indol-2-one (linopirdine)- and 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991)-sensitive KCNQ currents that were electrophysiologically and pharmacologically distinct from other Kv currents. Suppression of KCNQ currents by AVP (100 pM) was associated with significant membrane depolarization, and it was abolished by the protein kinase C (PKC) inhibitor calphostin C (250 nM). The KCNQ channel blocker linopirdine (10 microM) inhibited KCNQ currents in MASMCs, and it induced constriction of isolated rat mesenteric arteries. The vasoconstrictor responses were not additive when combined with 30 pM AVP, and they were prevented by the L-type Ca2+ channel blocker verapamil. Ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl] carbamic acid (flupirtine) significantly enhanced KCNQ currents, and it reversed constrictor responses to 30 pM AVP. In vivo, i.v. administration of linopirdine induced a dose-dependent increase in mesenteric artery resistance and blood pressure, whereas flupirtine had the opposite effects. We conclude that physiological concentrations of AVP induce mesenteric artery constriction via PKC-dependent suppression of KCNQ currents and L-type Ca2+ channel activation in MASMCs.
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Affiliation(s)
- Alexander R Mackie
- Loyola University Medical Center, 2160 S. First Ave., Maywood, IL 60153, USA
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47
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Navedo MF, Nieves-Cintrón M, Amberg GC, Yuan C, Votaw VS, Lederer WJ, McKnight GS, Santana LF. AKAP150 is required for stuttering persistent Ca2+ sparklets and angiotensin II-induced hypertension. Circ Res 2008; 102:e1-e11. [PMID: 18174462 DOI: 10.1161/circresaha.107.167809] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hypertension is a perplexing multiorgan disease involving renal primary pathology and enhanced angiotensin II vascular reactivity. Here, we report that a novel form of a local Ca2+ signaling in arterial smooth muscle is linked to the development of angiotensin II-induced hypertension. Long openings and reopenings of L-type Ca2+ channels in arterial myocytes produce stuttering persistent Ca2+ sparklets that increase Ca2+ influx and vascular tone. These stuttering persistent Ca2+ sparklets arise from the molecular interactions between the L-type Ca2+ channel and protein kinase Calpha at only a few subsarcolemmal regions in resistance arteries. We have identified AKAP150 as the key protein, which targets protein kinase Calpha to the L-type Ca2+ channels and thereby enables its regulatory function. Accordingly, AKAP150 knockout mice (AKAP150-/-) were found to lack persistent Ca2+ sparklets and have lower arterial wall intracellular calcium ([Ca2+]i) and decreased myogenic tone. Furthermore, AKAP150-/- mice were hypotensive and did not develop angiotensin II-induced hypertension. We conclude that local control of L-type Ca2+ channel function is regulated by AKAP150-targeted protein kinase C signaling, which controls stuttering persistent Ca2+ influx, vascular tone, and blood pressure under physiological conditions and underlies angiotensin II-dependent hypertension.
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Affiliation(s)
- Manuel F Navedo
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, USA
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48
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Origins of blood volume change due to glutamatergic synaptic activity at astrocytes abutting on arteriolar smooth muscle cells. J Theor Biol 2007; 250:172-85. [PMID: 17920632 DOI: 10.1016/j.jtbi.2007.08.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 08/20/2007] [Accepted: 08/27/2007] [Indexed: 10/22/2022]
Abstract
The cellular mechanisms that couple activity of glutamatergic synapses with changes in blood flow, measured by a variety of techniques including the BOLD signal, have not previously been modelled. Here we provide such a model, that successfully accounts for the main observed changes in blood flow in both visual cortex and somatosensory cortex following their stimulation by high-contrast drifting grating or by single whisker stimulation, respectively. Coupling from glutamatergic synapses to smooth muscle cells of arterioles is effected by astrocytes releasing epoxyeicosatrienoic acids (EETs) onto them, following glutamate stimulation of the astrocyte. Coupling of EETs to the smooth muscle of arterioles is by means of potassium channels in their membranes, leading to hyperpolarization, relaxation and hence an increase in blood flow. This model predicts a linear increase in blood flow with increasing numbers of activated astrocytes, but a non-linear increase with increasing glutamate release.
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49
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Sonkusare S, Fraer M, Marsh JD, Rusch NJ. Disrupting calcium channel expression to lower blood pressure: new targeting of a well-known channel. Mol Interv 2007; 6:304-10. [PMID: 17200457 PMCID: PMC4917382 DOI: 10.1124/mi.6.6.3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Swapnil Sonkusare
- Department of Pharmacology & Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
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50
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Gibson WG, Farnell L, Bennett MR. A computational model relating changes in cerebral blood volume to synaptic activity in neurons. Neurocomputing 2007. [DOI: 10.1016/j.neucom.2006.10.071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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